US20120116382A1 - Catheter apparatuses having multi-electrode arrays for renal neuromodulation and associated systems and methods - Google Patents

Catheter apparatuses having multi-electrode arrays for renal neuromodulation and associated systems and methods Download PDF

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US20120116382A1
US20120116382A1 US13/281,360 US201113281360A US2012116382A1 US 20120116382 A1 US20120116382 A1 US 20120116382A1 US 201113281360 A US201113281360 A US 201113281360A US 2012116382 A1 US2012116382 A1 US 2012116382A1
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treatment
support structure
helical
region
energy delivery
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US13/281,360
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Vincent Ku
Robert Beetel
Andrew Wu
Denise Zarins
Maria G. Aboytes
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Medtronic Ardian Luxembourg SARL
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Priority to US201161528684P priority
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Priority to US13/281,360 priority patent/US20120116382A1/en
Assigned to MEDTRONIC ARDIAN LUXEMBOURG S.A.R.L. reassignment MEDTRONIC ARDIAN LUXEMBOURG S.A.R.L. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ABOYTES, MARIA G, BEETEL, ROBERT, KU, VINCENT, WU, ANDREW, ZARINS, DENISE
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    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/12Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
    • A61B18/14Probes or electrodes therefor
    • A61B18/1492Probes or electrodes therefor having a flexible, catheter-like structure, e.g. for heart ablation
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M25/00Catheters; Hollow probes
    • A61M25/0067Catheters; Hollow probes characterised by the distal end, e.g. tips
    • A61M25/0074Dynamic characteristics of the catheter tip, e.g. openable, closable, expandable or deformable
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M25/00Catheters; Hollow probes
    • A61M25/01Introducing, guiding, advancing, emplacing or holding catheters
    • A61M25/0105Steering means as part of the catheter or advancing means; Markers for positioning
    • A61M25/0133Tip steering devices
    • A61M25/0138Tip steering devices having flexible regions as a result of weakened outer material, e.g. slots, slits, cuts, joints or coils
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M25/00Catheters; Hollow probes
    • A61M25/01Introducing, guiding, advancing, emplacing or holding catheters
    • A61M25/0105Steering means as part of the catheter or advancing means; Markers for positioning
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    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00005Cooling or heating of the probe or tissue immediately surrounding the probe
    • A61B2018/00011Cooling or heating of the probe or tissue immediately surrounding the probe with fluids
    • A61B2018/00023Cooling or heating of the probe or tissue immediately surrounding the probe with fluids closed, i.e. without wound contact by the fluid
    • AHUMAN NECESSITIES
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    • A61B2018/00315Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for treatment of particular body parts
    • A61B2018/00345Vascular system
    • A61B2018/00404Blood vessels other than those in or around the heart
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    • A61B2018/00315Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for treatment of particular body parts
    • A61B2018/00434Neural system
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    • A61B2018/00315Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for treatment of particular body parts
    • A61B2018/00505Urinary tract
    • A61B2018/00511Kidney
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
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    • A61B2018/00571Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for achieving a particular surgical effect
    • A61B2018/00577Ablation
    • AHUMAN NECESSITIES
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    • A61B18/00Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/12Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
    • A61B18/14Probes or electrodes therefor
    • A61B2018/1405Electrodes having a specific shape
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    • AHUMAN NECESSITIES
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    • A61B18/00Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/12Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by passing a current through the tissue to be heated, e.g. high-frequency current
    • A61B18/14Probes or electrodes therefor
    • A61B2018/1467Probes or electrodes therefor using more than two electrodes on a single probe
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M25/00Catheters; Hollow probes
    • A61M25/0021Catheters; Hollow probes characterised by the form of the tubing
    • A61M25/0041Catheters; Hollow probes characterised by the form of the tubing pre-formed, e.g. specially adapted to fit with the anatomy of body channels
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61MDEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M25/00Catheters; Hollow probes
    • A61M25/01Introducing, guiding, advancing, emplacing or holding catheters
    • A61M25/0105Steering means as part of the catheter or advancing means; Markers for positioning
    • A61M25/0133Tip steering devices

Abstract

Catheter apparatuses, systems, and methods for achieving renal neuromodulation by intravascular access are disclosed herein. One aspect of the present technology, for example, is directed to a treatment device having a multi-electrode array configured to be delivered to a renal blood vessel. The array is selectively transformable between a delivery or low-profile state (e.g., a generally straight shape) and a deployed state (e.g., a radially expanded, generally helical shape). The multi-electrode array is sized and shaped so that the electrodes or energy delivery elements contact an interior wall of the renal blood vessel when the array is in the deployed (e.g., helical) state. The electrodes or energy delivery elements are configured for direct and/or indirect application of thermal and/or electrical energy to heat or otherwise electrically modulate neural fibers that contribute to renal function or of vascular structures that feed or perfuse the neural fibers.

Description

    CROSS-REFERENCE TO RELATED APPLICATION(S)
  • This application claims the benefit of the following pending applications:
  • (a) U.S. Provisional Application No. 61/406,531, filed Oct. 25, 2010;
  • (b) U.S. Provisional Application No. 61/406,960, filed Oct. 26, 2010;
  • (c) U.S. Provisional Application No. 61/572,290, filed Jan. 28, 2011;
  • (d) U.S. Provisional Application No. 61/528,001, filed Aug. 25, 2011;
  • (e) U.S. Provisional Application No. 61/528,086, filed Aug. 26, 2011;
  • (f) U.S. Provisional Application No. 61/528,091, filed Aug. 26, 2011;
  • (g) U.S. Provisional Application No. 61/528,108, filed Aug. 26, 2011;
  • (h) U.S. Provisional Application No. 61/528,684, filed Aug. 29, 2011; and
  • (i) U.S. Provisional Application No. 61/546,512, filed Oct. 12, 2011.
  • All of the foregoing applications are incorporated herein by reference in their entireties. Further, components and features of embodiments disclosed in the applications incorporated by reference may be combined with various components and features disclosed and claimed in the present application.
  • TECHNICAL FIELD
  • The present technology relates generally to renal neuromodulation and associated systems and methods. In particular, several embodiments are directed to multi-electrode radio frequency (RF) ablation catheter apparatuses for intravascular renal neuromodulation and associated systems and methods.
  • BACKGROUND
  • The sympathetic nervous system (SNS) is a primarily involuntary bodily control system typically associated with stress responses. Fibers of the SNS innervate tissue in almost every organ system of the human body and can affect characteristics such as pupil diameter, gut motility, and urinary output. Such regulation can have adaptive utility in maintaining homeostasis or in preparing the body for rapid response to environmental factors. Chronic activation of the SNS, however, is a common maladaptive response that can drive the progression of many disease states. Excessive activation of the renal SNS in particular has been identified experimentally and in humans as a likely contributor to the complex pathophysiology of hypertension, states of volume overload (such as heart failure), and progressive renal disease. For example, radiotracer dilution has demonstrated increased renal norepinephrine (NE) spillover rates in patients with essential hypertension.
  • Cardio-renal sympathetic nerve hyperactivity can be particularly pronounced in patients with heart failure. For example, an exaggerated NE overflow from the heart and kidneys to plasma is often found in these patients. Heightened SNS activation commonly characterizes both chronic and end stage renal disease. In patients with end stage renal disease, NE plasma levels above the median have been demonstrated to be predictive for cardiovascular diseases and several causes of death. This is also true for patients suffering from diabetic or contrast nephropathy. Evidence suggests that sensory afferent signals originating from diseased kidneys are major contributors to initiating and sustaining elevated central sympathetic outflow.
  • Sympathetic nerves innervating the kidneys terminate in the blood vessels, the juxtaglomerular apparatus, and the renal tubules. Stimulation of the renal sympathetic nerves can cause increased renin release, increased sodium (Na+) reabsorption, and a reduction of renal blood flow. These neural regulation components of renal function are considerably stimulated in disease states characterized by heightened sympathetic tone and likely contribute to increased blood pressure in hypertensive patients. The reduction of renal blood flow and glomerular filtration rate as a result of renal sympathetic efferent stimulation is likely a cornerstone of the loss of renal function in cardio-renal syndrome (i.e., renal dysfunction as a progressive complication of chronic heart failure). Pharmacologic strategies to thwart the consequences of renal efferent sympathetic stimulation include centrally acting sympatholytic drugs, beta blockers (intended to reduce renin release), angiotensin converting enzyme inhibitors and receptor blockers (intended to block the action of angiotensin II and aldosterone activation consequent to renin release), and diuretics (intended to counter the renal sympathetic mediated sodium and water retention). These pharmacologic strategies, however, have significant limitations including limited efficacy, compliance issues, side effects, and others. Accordingly, there is a strong public-health need for alternative treatment strategies.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on illustrating clearly the principles of the present disclosure.
  • FIG. 1 illustrates an intravascular renal neuromodulation system configured in accordance with an embodiment of the present technology.
  • FIG. 2 illustrates modulating renal nerves with a multi-electrode catheter apparatus in accordance with an embodiment of the present technology.
  • FIG. 3A is a view of a distal portion of a catheter shaft and a multi-electrode array in a delivery state (e.g., low-profile or collapsed configuration) within a renal artery used in conjunction with a guide catheter in accordance with an embodiment of the present technology.
  • FIG. 3B is a view of the distal portion of the catheter shaft and the multi-electrode array of FIG. 3A in a deployed state (e.g., expanded configuration) within a renal artery in accordance with an embodiment of the technology.
  • FIG. 3C is a partially cutaway, isometric view of a treatment device in a deployed state within a renal artery in accordance with an embodiment of the technology.
  • FIG. 4A is a plan view of a treatment assembly for use in a treatment device in accordance with an embodiment of the technology.
  • FIG. 4B is an isometric view of the treatment assembly of FIG. 4A.
  • FIG. 4C is an end view of the helical structure of FIG. 4B showing the angular offset of energy delivery elements in a treatment assembly in accordance with an embodiment of the technology.
  • FIG. 4D is a side view of a vessel with lesions prophetically formed by a treatment assembly that circumferentially and longitudinally overlap but do not overlap along a helical path.
  • FIG. 5A-5D illustrate various embodiments of energy delivery elements or devices for use with the treatment assembly of FIGS. 4A and 4B.
  • FIG. 5E illustrates an embodiment of a treatment assembly in which the support structure is electrically conductive and serves as the energy delivery element.
  • FIG. 6A illustrates an embodiment of a treatment device including an elongated shaft having different mechanical and functional regions configured in accordance with an embodiment of the technology.
  • FIG. 6B is a plan view of a slot pattern for use in the treatment device of FIG. 6A.
  • FIG. 6C is a perspective view of a distal portion of the treatment device of FIG. 6A in a delivery state (e.g., low-profile or collapsed configuration) outside a patient in accordance with an embodiment of the technology.
  • FIG. 6D is a perspective view of the treatment device of FIG. 6C in a deployed state (e.g., expanded configuration) outside a patient.
  • FIG. 6E is a partially schematic plan view of a distal region of the support structure of FIG. 6A in a generally helically-shaped deployed state.
  • FIG. 6F is a partially schematic plan view of a distal portion of a treatment device of in a polygon-shaped deployed state in accordance with another embodiment of the technology.
  • FIG. 6G is a plan view of a slot pattern for use in the treatment device of FIG. 6A in accordance with another embodiment of the technology.
  • FIG. 6H is a perspective view of a support structure for use in a treatment device configured in accordance with another embodiment of the technology.
  • FIG. 6I is a plan view of an embodiment of a slot pattern for use in the support structure of FIG. 6H.
  • FIG. 6J is a plan view of a slot pattern for use with a treatment device configured in accordance with an embodiment of the technology.
  • FIGS. 6K and 6L illustrate deformed slots of the support structure of FIG. 6H in a deployed state in accordance with an embodiment of the technology.
  • FIG. 6M is a plan view of a slot pattern for use with a treatment device configured in accordance with an embodiment of the technology.
  • FIG. 6N is a plan view of a slot pattern for use with a treatment device configured in accordance with an embodiment of the technology.
  • FIG. 6O is a schematic illustration of a portion of a treatment device having a support structure including the slot pattern of FIG. 6N in a deployed state within a renal artery of a patient.
  • FIG. 7A is a plan view of a hole pattern for use with a treatment device configured in accordance with an embodiment of the technology.
  • FIG. 7B is a perspective view of a distal portion of a treatment device including a flexible region having the hole pattern of FIG. 7A in a delivery state outside a patient.
  • FIG. 8A is a broken perspective view in partial section of a treatment device including the slot pattern of FIG. 6I configured in accordance with an embodiment of the technology.
  • FIGS. 8B-8D illustrate various configurations of a distal end of a support structure configured in accordance with embodiments of the present technology.
  • FIG. 9A illustrates a treatment device configured in accordance with an embodiment of the present technology in a deployed state (e.g., expanded configuration) outside a patient.
  • FIG. 9B illustrates the treatment device of FIG. 9A in a delivery state (e.g., low-profile or collapsed configuration).
  • FIG. 9C illustrates another embodiment of a treatment device configured in accordance with an embodiment of the present technology in a deployed state.
  • FIG. 9D illustrates yet another embodiment of a treatment device in a delivery state.
  • FIG. 9E illustrates the device of FIG. 9D in a deployed state.
  • FIG. 10A is broken plan view of another treatment device in a delivery state outside a patient in accordance with an embodiment of the technology.
  • FIG. 10B is a detailed view of a distal portion of the device of FIG. 10A in a deployed state.
  • FIG. 11A is a broken side view in part section of a treatment device in a delivery state in accordance with another embodiment of the technology.
  • FIG. 11B is a broken side view in part section of the treatment device of FIG. 11A in a deployed state.
  • FIG. 11C is a longitudinal cross-sectional view of a handle assembly for use in the device of FIG. 11A in accordance with an embodiment of the present technology.
  • FIG. 11D is a longitudinal cross-sectional view of another handle assembly for use in the device of FIG. 11A in accordance with an embodiment of the present technology.
  • FIG. 12A is a side view of a distal portion of a treatment device in a delivery state (e.g., low-profile or collapsed configuration) outside a patient in accordance with an embodiment of the present technology.
  • FIG. 12B is a side view of the distal portion of the treatment device of FIG. 12B in a deployed state (e.g., expanded configuration) outside the patient.
  • FIG. 13A is a broken side view in part section of a treatment device in a delivery state in accordance an embodiment of the present technology.
  • FIG. 13B is a broken side view in part section of the embodiment of FIG. 13A in a deployed state within a renal artery.
  • FIG. 14A is a broken longitudinal cross-sectional view of another embodiment of a treatment device in a delivery state in accordance an embodiment of the present technology.
  • FIG. 14B is a broken side view in part section of the embodiment of FIG. 14A in a deployed state within a renal artery.
  • FIG. 14C is a longitudinal cross-sectional view of a distal portion of another embodiment of a treatment device in a delivery state in accordance an embodiment of the present technology.
  • FIG. 14D is a broken longitudinal cross-sectional view of the embodiment of FIG. 14C in a deployed state within a renal artery.
  • FIG. 15A is a longitudinal cross-sectional view of a distal portion of another embodiment of a treatment device in a delivery state in accordance an embodiment of the present technology.
  • FIG. 15B is a broken side view in part section of the embodiment of FIG. 15A in a deployed state within a renal artery.
  • FIG. 16A is a cross-sectional view of one embodiment a treatment device in a delivery state within a patient's renal artery in accordance an embodiment of the present technology.
  • FIG. 16B is a cross-sectional view of one embodiment a treatment device in a deployed state within a patient's renal artery in accordance an embodiment of the present technology.
  • FIG. 17A is a broken side view in part section of a distal portion a rapid-exchange type of a treatment device configured in accordance an embodiment of the present technology.
  • FIG. 17B is a broken side view in part section of a distal portion of a rapid-exchange type of a treatment device in a delivery state in accordance an embodiment of the present technology.
  • FIG. 17C is a broken side view of a distal portion of the treatment device of FIG. 17B in a deployed state.
  • FIG. 17C is a broken side view in part section of a distal portion of another embodiment of a rapid-exchange type of a treatment device in accordance an embodiment of the present technology.
  • FIG. 17D is a broken side view in part section of a distal portion of another rapid-exchange type of a treatment device in accordance an embodiment of the present technology.
  • FIG. 17E is a broken side view in part section of a distal portion of yet another embodiment of a rapid-exchange type of a treatment device in accordance an embodiment of the present technology.
  • FIG. 18 is an illustration of theoretical blood flow in a renal artery in accordance with an embodiment of the technology.
  • FIG. 19A is a cross-sectional view of a treatment assembly including a fluid redirecting element within a renal artery in accordance with an embodiment of the present technology.
  • FIG. 19B is a side view of a support structure with a schematic illustration of a fluid redirecting element in a delivery state (e.g., low-profile or collapsed configuration) outside a patient in accordance with an embodiment of the present technology.
  • FIG. 20 is a graph depicting an energy delivery algorithm that may be used in conjunction with the system of FIG. 1 in accordance with an embodiment of the technology.
  • FIGS. 21 and 22 are block diagrams illustrating algorithms for evaluating a treatment in accordance with embodiments of the present technology.
  • FIG. 23 is a block diagram illustrating an algorithm for providing operator feedback upon occurrence of a high temperature condition in accordance with an embodiment of the present technology.
  • FIG. 24 is a block diagram illustrating an algorithm for providing operator feedback upon occurrence of a high impedance condition in accordance with an embodiment of the present technology.
  • FIG. 25 is a block diagram illustrating an algorithm for providing operator feedback upon occurrence of a high degree of vessel constriction in accordance with an embodiment of the present technology.
  • FIG. 26A is a block diagram illustrating an algorithm for providing operator feedback upon occurrence of an abnormal heart rate condition in accordance with an embodiment of the present technology.
  • FIG. 26B is a block diagram illustrating an algorithm for providing operator feedback upon occurrence of a low blood flow condition in accordance with an embodiment of the present technology.
  • FIGS. 27A and 27B are screen shots illustrating representative generator display screens configured in accordance with aspects of the present technology.
  • FIG. 28 is an illustration of a kit containing packaged components of the system of FIG. 1 in accordance with an embodiment of the technology.
  • FIG. 29 is a conceptual illustration of the sympathetic nervous system (SNS) and how the brain communicates with the body via the SNS.
  • FIG. 30 is an enlarged anatomic view of nerves innervating a left kidney to form the renal plexus surrounding the left renal artery.
  • FIGS. 31A and 31B provide anatomic and conceptual views of a human body, respectively, depicting neural efferent and afferent communication between the brain and kidneys.
  • FIGS. 32A and 32B are, respectively, anatomic views of the arterial and venous vasculatures of a human.
  • DETAILED DESCRIPTION
  • The present technology is directed to apparatuses, systems, and methods for achieving electrically- and/or thermally-induced renal neuromodulation (i.e., rendering neural fibers that innervate the kidney inert or inactive or otherwise completely or partially reduced in function) by percutaneous transluminal intravascular access. In particular, embodiments of the present technology relate to apparatuses, systems, and methods that incorporate a catheter treatment device having a multi-electrode array movable between a delivery or low-profile state (e.g., a generally straight shape) and a deployed state (e.g., a radially expanded, generally helical shape). The electrodes or energy delivery elements carried by the array are configured to deliver energy (e.g., electrical energy, radio frequency (RF) electrical energy, pulsed electrical energy, thermal energy) to a renal artery after being advanced via catheter along a percutaneous transluminal path (e.g., a femoral artery puncture, an iliac artery and the aorta, a radial artery, or another suitable intravascular path). The multi-electrode array is sized and shaped so that the electrodes or energy delivery elements contact an interior wall of the renal artery when the array is in the deployed (e.g., helical) state within the renal artery. In addition, the helical shape of the deployed array allows blood to flow through the helix, which is expected to help prevent occlusion of the renal artery during activation of the energy delivery element. Further, blood flow in and around the array may cool the associated electrodes and/or the surrounding tissue. In some embodiments, cooling the energy delivery elements allows for the delivery of higher power levels at lower temperatures than may be reached without cooling. This feature is expected to help create deeper and/or larger lesions during therapy, reduce intimal surface temperature, and/or allow longer activation times with reduced risk of overheating during treatment.
  • Specific details of several embodiments of the technology are described below with reference to FIGS. 1-32B. Although many of the embodiments are described below with respect to devices, systems, and methods for intravascular modulation of renal nerves using multi-electrode arrays, other applications and other embodiments in addition to those described herein are within the scope of the technology. Additionally, several other embodiments of the technology can have different configurations, components, or procedures than those described herein. A person of ordinary skill in the art, therefore, will accordingly understand that the technology can have other embodiments with additional elements, or the technology can have other embodiments without several of the features shown and described below with reference to FIGS. 1-32B.
  • As used herein, the terms “distal” and “proximal” define a position or direction with respect to the treating clinician or clinician's control device (e.g., a handle assembly). “Distal” or “distally” are a position distant from or in a direction away from the clinician or clinician's control device. “Proximal” and “proximally” are a position near or in a direction toward the clinician or clinician's control device.
  • I. RENAL NEUROMODULATION
  • Renal neuromodulation is the partial or complete incapacitation or other effective disruption of nerves innervating the kidneys. In particular, renal neuromodulation comprises inhibiting, reducing, and/or blocking neural communication along neural fibers (i.e., efferent and/or afferent nerve fibers) innervating the kidneys. Such incapacitation can be long-term (e.g., permanent or for periods of months, years, or decades) or short-term (e.g., for periods of minutes, hours, days, or weeks). Renal neuromodulation is expected to efficaciously treat several clinical conditions characterized by increased overall sympathetic activity, and in particular conditions associated with central sympathetic over stimulation such as hypertension, heart failure, acute myocardial infarction, metabolic syndrome, insulin resistance, diabetes, left ventricular hypertrophy, chronic and end stage renal disease, inappropriate fluid retention in heart failure, cardio-renal syndrome, and sudden death. The reduction of afferent neural signals contributes to the systemic reduction of sympathetic tone/drive, and renal neuromodulation is expected to be useful in treating several conditions associated with systemic sympathetic over activity or hyperactivity. Renal neuromodulation can potentially benefit a variety of organs and bodily structures innervated by sympathetic nerves. For example, a reduction in central sympathetic drive may reduce insulin resistance that afflicts patients with metabolic syndrome and Type II diabetics. Additionally, osteoporosis can be sympathetically activated and might benefit from the downregulation of sympathetic drive that accompanies renal neuromodulation. A more detailed description of pertinent patient anatomy and physiology is provided in Section IX below.
  • Various techniques can be used to partially or completely incapacitate neural pathways, such as those innervating the kidney. The purposeful application of energy (e.g., electrical energy, thermal energy) to tissue by energy delivery element(s) can induce one or more desired thermal heating effects on localized regions of the renal artery and adjacent regions of the renal plexus RP, which lay intimately within or adjacent to the adventitia of the renal artery. The purposeful application of the thermal heating effects can achieve neuromodulation along all or a portion of the renal plexus RP.
  • The thermal heating effects can include both thermal ablation and non-ablative thermal alteration or damage (e.g., via sustained heating and/or resistive heating). Desired thermal heating effects may include raising the temperature of target neural fibers above a desired threshold to achieve non-ablative thermal alteration, or above a higher temperature to achieve ablative thermal alteration. For example, the target temperature can be above body temperature (e.g., approximately 37° C.) but less than about 45° C. for non-ablative thermal alteration, or the target temperature can be about 45° C. or higher for the ablative thermal alteration.
  • More specifically, exposure to thermal energy (heat) in excess of a body temperature of about 37° C., but below a temperature of about 45° C., may induce thermal alteration via moderate heating of the target neural fibers or of vascular structures that perfuse the target fibers. In cases where vascular structures are affected, the target neural fibers are denied perfusion resulting in necrosis of the neural tissue. For example, this may induce non-ablative thermal alteration in the fibers or structures. Exposure to heat above a temperature of about 45° C., or above about 60° C., may induce thermal alteration via substantial heating of the fibers or structures. For example, such higher temperatures may thermally ablate the target neural fibers or the vascular structures. In some patients, it may be desirable to achieve temperatures that thermally ablate the target neural fibers or the vascular structures, but that are less than about 90° C., or less than about 85° C., or less than about 80° C., and/or less than about 75° C. Regardless of the type of heat exposure utilized to induce the thermal neuromodulation, a reduction in renal sympathetic nerve activity (“RSNA”) is expected.
  • II. SELECTED EMBODIMENTS OF CATHETER APPARATUSES HAVING MULTI-ELECTRODE ARRAYS
  • FIG. 1 illustrates a renal neuromodulation system 10 (“system 10”) configured in accordance with an embodiment of the present technology. The system 10 includes an intravascular treatment device 12 operably coupled to an energy source or energy generator 26. In the embodiment shown in FIG. 1, the treatment device 12 (e.g., a catheter) includes an elongated shaft 16 having a proximal portion 18, a handle 34 at a proximal region of the proximal portion 18, and a distal portion 20 extending distally relative to the proximal portion 18. The treatment device 12 further includes a therapeutic assembly or treatment section 21 at the distal portion 20 of the shaft 16. As explained in further detail below, the therapeutic assembly 21 can include an array of two or more electrodes or energy delivery elements 24 configured to be delivered to a renal blood vessel (e.g., a renal artery) in a low-profile configuration. Upon delivery to the target treatment site within the renal blood vessel, the therapeutic assembly 21 is further configured to be deployed into an expanded state (e.g., a generally helical or spiral configuration) for delivering energy at the treatment site and providing therapeutically-effective electrically- and/or thermally-induced renal neuromodulation. Alternatively, the deployed state may be non-helical provided that the deployed state delivers the energy to the treatment site. In some embodiments, the therapeutic assembly 21 may be placed or transformed into the deployed state or arrangement via remote actuation, e.g., via an actuator 36, such as a knob, pin, or lever carried by the handle 34. In other embodiments, however, the therapeutic assembly 21 may be transformed between the delivery and deployed states using other suitable mechanisms or techniques.
  • The proximal end of the therapeutic assembly 21 is carried by or affixed to the distal portion 20 of the elongated shaft 16. A distal end of the therapeutic assembly 21 may terminate the treatment device 12 with, for example, an atraumatic rounded tip or cap. Alternatively, the distal end of the therapeutic assembly 21 may be configured to engage another element of the system 10 or treatment device 12. For example, the distal end of the therapeutic assembly 21 may define a passageway for engaging a guide wire (not shown) for delivery of the treatment device using over-the-wire (“OTW”) or rapid exchange (“RX”) techniques. Further details regarding such arrangements are described below with reference to FIGS. 9A-17E.
  • The energy source or energy generator 26 (e.g., a RF energy generator) is configured to generate a selected form and magnitude of energy for delivery to the target treatment site via the energy delivery elements 24. The energy generator 26 can be electrically coupled to the treatment device 12 via a cable 28. At least one supply wire (not shown) passes along the elongated shaft 16 or through a lumen in the elongated shaft 16 to the energy delivery elements 24 and transmits the treatment energy to the energy delivery elements 24. In some embodiments, each energy delivery element 24 includes its own supply wire. In other embodiments, however, two or more energy delivery elements 24 may be electrically coupled to the same supply wire. A control mechanism, such as foot pedal 32, may be connected (e.g., pneumatically connected or electrically connected) to the energy generator 26 to allow the operator to initiate, terminate and, optionally, adjust various operational characteristics of the generator, including, but not limited to, power delivery. The system 10 may also include a remote control device (not shown) that can be positioned in a sterile field and operably coupled to the energy delivery elements 24. The remote control device is configured to allow for selectively turning on/off the electrodes. In other embodiments, the remote control device may be built into the handle assembly 34. The energy generator 26 can be configured to deliver the treatment energy via an automated control algorithm 30 and/or under the control of the clinician. In addition, the energy generator 26 may include one or more evaluation or feedback algorithms 31 to provide feedback to the clinician before, during, and/or after therapy. Further details regarding suitable control algorithms and evaluation/feedback algorithms are described below with reference to FIGS. 20-27.
  • In some embodiments, the system 10 may be configured to provide delivery of a monopolar electric field via the energy delivery elements 24. In such embodiments, a neutral or dispersive electrode 38 may be electrically connected to the energy generator 26 and attached to the exterior of the patient (as shown in FIG. 2). Additionally, one or more sensors (not shown), such as one or more temperature (e.g., thermocouple, thermistor, etc.), impedance, pressure, optical, flow, chemical or other sensors, may be located proximate to or within the energy delivery elements 24 and connected to one or more supply wires (not shown). For example, a total of two supply wires may be included, in which both wires could transmit the signal from the sensor and one wire could serve dual purpose and also convey the energy to the energy delivery elements 24. Alternatively, a different number of supply wires may be used to transmit energy to the energy delivery elements 24.
  • The energy generator 26 may be part of a device or monitor that may include processing circuitry, such as a microprocessor, and a display. The processing circuitry may be configured to execute stored instructions relating to the control algorithm 30. The monitor may be configured to communicate with the treatment device 12 (e.g., via cable 28) to control power to the energy delivery elements 24 and/or to obtain signals from the energy delivery elements 24 or any associated sensors. The monitor may be configured to provide indications of power levels or sensor data, such as audio, visual or other indications, or may be configured to communicate the information to another device. For example, the energy generator 26 may also be configured to be operably coupled to a catheter lab screen or system for displaying treatment information.
  • FIG. 2 (with additional reference to FIG. 30) illustrates modulating renal nerves with an embodiment of the system 10. The treatment device 12 provides access to the renal plexus RP through an intravascular path P, such as a percutaneous access site in the femoral (illustrated), brachial, radial, or axillary artery to a targeted treatment site within a respective renal artery RA. As illustrated, a section of the proximal portion 18 of the shaft 16 is exposed externally of the patient. By manipulating the proximal portion 18 of the shaft 16 from outside the intravascular path P, the clinician may advance the shaft 16 through the sometimes tortuous intravascular path P and remotely manipulate the distal portion 20 of the shaft 16. Image guidance, e.g., computed tomography (CT), fluoroscopy, intravascular ultrasound (IVUS), optical coherence tomography (OCT), or another suitable guidance modality, or combinations thereof, may be used to aid the clinician's manipulation. Further, in some embodiments, image guidance components (e.g., IVUS, OCT) may be incorporated into the treatment device 12 itself. After the therapeutic assembly 21 is adequately positioned in the renal artery RA, it can be radially expanded or otherwise deployed using the handle 34 or other suitable means until the energy delivery elements 24 are in stable contact with the inner wall of the renal artery RA. The purposeful application of energy from the energy delivery elements 24 is then applied to tissue to induce one or more desired neuromodulating effects on localized regions of the renal artery and adjacent regions of the renal plexus RP, which lay intimately within, adjacent to, or in close proximity to the adventitia of the renal artery RA. The purposeful application of the energy may achieve neuromodulation along all or at least a portion of the renal plexus RP.
  • The neuromodulating effects are generally a function of, at least in part, power, time, contact between the energy delivery elements 24 and the vessel wall, and blood flow through the vessel. The neuromodulating effects may include denervation, thermal ablation, and non-ablative thermal alteration or damage (e.g., via sustained heating and/or resistive heating). Desired thermal heating effects may include raising the temperature of target neural fibers above a desired threshold to achieve non-ablative thermal alteration, or above a higher temperature to achieve ablative thermal alteration. For example, the target temperature may be above body temperature (e.g., approximately 37° C.) but less than about 45° C. for non-ablative thermal alteration, or the target temperature may be about 45° C. or higher for the ablative thermal alteration. Desired non-thermal neuromodulation effects may include altering the electrical signals transmitted in a nerve.
  • In some embodiments, the energy delivery elements 24 of the therapeutic assembly 21 may be proximate to, adjacent to, or carried by (e.g., adhered to, threaded over, wound over, and/or crimped to) a support structure 22. The proximal end of the support structure 22 is preferably coupled to the distal portion 20 of the elongated shaft 16 via a coupling (not shown). The coupling may be an integral component of the elongated shaft 16 (i.e., may not be a separate piece) or the coupling may be a separate piece such as a collar (e.g., a radiopaque band) wrapped around an exterior surface of the elongated shaft 16 to secure the support structure 22 to the elongated shaft 16. In other embodiments, however, the support structure 22 may be associated with the elongated shaft 16 using another arrangement and/or different features.
  • In still another embodiment, the energy delivery elements 24 may form or define selected portions of, or the entirety of, the support structure 22 itself. That is, as is described in further detail below, the support structure 22 may be capable of delivering energy. Moreover, although in some embodiments the therapeutic assembly 21 may function with a single energy delivery element, it will be appreciated that the therapeutic assembly 21 preferably includes a plurality of energy delivery elements 24 associated with or defining the support structure 22. When multiple energy delivery elements 24 are provided, the energy delivery elements 24 may deliver power independently (i.e., may be used in a monopolar fashion), either simultaneously, selectively, or sequentially, and/or may deliver power between any desired combination of the elements (i.e., may be used in a bipolar fashion). Furthermore, the clinician optionally may choose which energy delivery element(s) 24 are used for power delivery in order to form highly customized lesion(s) within the renal artery having a variety of shapes or patterns.
  • FIG. 3A is a cross-sectional view illustrating one embodiment of the distal portion 20 of the shaft 16 and the therapeutic assembly 21 in a delivery state (e.g., low-profile or collapsed configuration) within a renal artery RA, and FIGS. 3B and 3C illustrate the therapeutic assembly 21 in a deployed state (e.g., expanded or helical configuration) within the renal artery. Referring first to FIG. 3A, the collapsed or delivery arrangement of the therapeutic assembly 21 defines a low profile about the longitudinal axis A-A of the assembly such that a transverse dimension of the therapeutic assembly 21 is sufficiently small to define a clearance distance between an arterial wall 55 and the treatment device 12. The delivery state facilitates insertion and/or removal of the treatment device 12 and, if desired, repositioning of the therapeutic assembly 21 within the renal artery RA.
  • In the collapsed configuration, for example, the geometry of the support structure 22 facilitates movement of the therapeutic assembly 21 through a guide catheter 90 to the treatment site in the renal artery RA. Moreover, in the collapsed configuration, the therapeutic assembly 21 is sized and shaped to fit within the renal artery RA and has a diameter that is less than a renal artery inner diameter 52 and a length (from a proximal end of the therapeutic assembly 21 to a distal end of the therapeutic assembly 21) that is less than a renal artery length 54. Further, as described in greater detail below, the geometry of the support structure 22 is also arranged to define (in the delivery state) a minimum transverse dimension about its central axis that is less than the renal artery inner diameter 52 and a maximum length in the direction of the central axis that is preferably less than the renal artery length 54. In one embodiment, for example, the minimum diameter of the therapeutic assembly 21 is approximately equal to the interior diameter of the elongated shaft 16.
  • The distal portion 20 of the shaft 16 may flex in a substantial fashion to gain entrance into a respective left/right renal artery by following a path defined by a guide catheter, a guide wire, or a sheath. For example, the flexing of distal portion 20 may be imparted by the guide catheter 90, such as a renal guide catheter with a preformed bend near the distal end that directs the shaft 16 along a desired path, from the percutaneous insertion site to the renal artery RA. In another embodiment, the treatment device 12 may be directed to the treatment site within the renal artery RA by engaging and tracking a guide wire (e.g., guide wire 66 of FIG. 2) that is inserted into the renal artery RA and extends to the percutaneous access site. In operation, the guide wire is preferably first delivered into the renal artery RA and the elongated shaft 16 comprising a guide wire lumen is then passed over the guide wire into the renal artery RA. In some guide wire procedures, a tubular delivery sheath 1291 (described in greater detail below with reference to FIGS. 16A and 16B) is passed over the guide wire (i.e., the lumen defined by the delivery sheath slides over the guide wire) into the renal artery RA. Once the delivery sheath 1291 (FIG. 16A) is placed in the renal artery RA, the guide wire may be removed and exchanged for a treatment catheter (e.g., treatment device 12) that may be delivered through the delivery sheath 1291 into the renal artery RA. Furthermore, in some embodiments, the distal portion 20 can be directed or “steered” into the renal artery RA via the handle assembly 34 (FIGS. 1 and 2), for example, by an actuatable element 36 or by another control element. In particular, the flexing of the elongated shaft 16 may be accomplished as provided in U.S. patent application Ser. No. 12/545,648, “Apparatus, Systems, and Methods for achieving Intravascular, Thermally-Induced Renal Neuromodulation” to Wu et al., which is incorporated herein by reference in its entirety. Alternatively, or in addition, the treatment device 12 and its distal portion 20 may be flexed by being inserted through a steerable guide catheter (not shown) that includes a preformed or steerable bend near its distal end that can be adjusted or re-shaped by manipulation from the proximal end of the guide catheter.
  • The maximum outer dimension (e.g., diameter) of any section of the treatment device 12, including elongated shaft 16 and the energy delivery elements 24 of the therapeutic assembly 21 can be defined by an inner diameter of the guide catheter 90 through which the device 12 is passed. In one particular embodiment, for example, an 8 French guide catheter having, for example, an inner diameter of approximately 0.091 inch (2.31 mm) may be used as a guide catheter to access the renal artery. Allowing for a reasonable clearance tolerance between the energy delivery elements 24 and the guide catheter, the maximum outer dimension of the therapeutic assembly 21 is generally less than or equal to approximately 0.085 inch (2.16 mm). For a therapeutic assembly having a substantially helical support structure for carrying the energy delivery elements 24, the expanded or helical configuration preferably defines a maximum width of less than or equal to approximately 0.085 inch (2.16 mm). However, use of a smaller 5 French guide catheter may require the use of smaller outer diameters along the treatment device 12. For example, a therapeutic assembly 21 having a helical support structure 22 that is to be routed within a 5 French guide catheter preferably has an outer dimension or maximum width of no greater than about 0.053 inch (1.35 mm). In still other embodiments, it may be desirable to have a therapeutic assembly 21 with a maximum width substantially under 0.053 inch (1.35 mm) provided there is sufficient clearance between the energy delivery elements and the guide catheter. Moreover, in some embodiments it may be desirable to have an arrangement in which the guide catheter and the therapeutic assembly 21 define a ratio of diameters of about 1.5:1. In another example, the helical structure and energy delivery element 24 that are to be delivered within a 6 French guide catheter would have an outer dimension of no great than 0.070 inch (1.78 mm). In still further examples, other suitable guide catheters may be used, and outer dimensions and/or arrangements of the treatment device 12 can vary accordingly.
  • After locating the therapeutic assembly 21 at the distal portion 20 of the shaft 16 in the renal artery RA, the therapeutic assembly 21 is transformed from its delivery state to its deployed state or deployed arrangement. The transformation may be initiated using an arrangement of device components as described herein with respect to the particular embodiments and their various modes of deployment. As described in greater detail below and in accordance with one or more embodiments of the present technology, the therapeutic assembly may be deployed by a control member, such as for example a pull- or tension-wire, guide wire, shaft or stylet engaged internally or externally with the support structure of the therapeutic assembly to apply a deforming or shaping force to the assembly to transform it into its deployed state. Alternatively, the therapeutic assembly 21 may be self expanding or deploying such that removal of a radial restraint results in deployment of the assembly. Further, the modality used to transform the therapeutic assembly 21 from the delivery state into the deployed state may, in most embodiments, be reversed to transform the therapeutic assembly 21 back to the delivery state from the deployed state.
  • Further manipulation of the support structure 22 and the energy delivery elements 24 within the respective renal artery RA establishes apposition of the energy delivery elements 24 against the tissue along an interior wall of the respective renal artery RA. For example, as shown in FIGS. 3B and 3C, the therapeutic assembly 21 is expanded within the renal artery RA such that the energy delivery elements 24 are in contact with the renal artery wall 55. In some embodiments, manipulation of the distal portion 20 will also facilitate contact between the energy delivery elements 24 and the wall of the renal artery. Embodiments of the support structures described herein (e.g., the support structure 22) are expected to ensure that the contact force between the renal artery inner wall 55 and the energy delivery elements 24 does not exceed a maximum value. In addition, the support structure 22 or other suitable support structures described herein preferably provide for a consistent contact force against the arterial wall 55 that may allow for consistent lesion formation.
  • The alignment may also include alignment of geometrical aspects of the energy delivery elements 24 with the renal artery wall 55. For example, in embodiments in which the energy delivery elements 24 have a cylindrical shape with rounded ends, alignment may include alignment of the longitudinal surface of the individual energy delivery elements 24 with the artery wall 55. In another example, an embodiment may comprise energy delivery elements 24 having a structured shape or inactive surface, and alignment may include aligning the energy delivery elements 24 such that the structured shape or inactive surface is not in contact with the artery wall 55.
  • As best seen in FIGS. 3B and 3C, in the deployed state, the therapeutic assembly 21 defines a substantially helical support structure 22 in contact with the renal artery wall 55 along a helical path. One advantage of this arrangement is that pressure from the helical structure can be applied to a large range of radial directions without applying pressure to a circumference of the vessel. Thus, the helically-shaped therapeutic assembly 21 is expected to provide stable contact between the energy delivery elements 24 and the artery wall 55 when the wall moves in any direction. Furthermore, pressure applied to the vessel wall 55 along a helical path is less likely to stretch or distend a circumference of a vessel that could thereby cause injury to the vessel tissue. Still another feature of the expanded helical structure is that it may contact the vessel wall in a large range of radial directions and maintain a sufficiently open lumen in the vessel allowing blood to flow through the helix during therapy.
  • As best seen in FIG. 3B, in the deployed state, the support structure 22 defines a maximum axial length of the therapeutic assembly 21 that is approximately equal to or less than a renal artery length 54 of a main renal artery (i.e., a section of a renal artery proximal to a bifurcation). Because this length can vary from patient to patient, it is envisioned that the deployed helical-shaped support structure 22 may be fabricated in different sizes (e.g., with varying lengths L and/or diameters D as shown in FIG. 4A) that may be appropriate for different patients. Referring to FIGS. 3B and 3C, in the deployed state, the helical-shaped therapeutic assembly 21 provides for circumferentially discontinuous contact between the energy delivery elements 24 and the inner wall 55 of the renal artery RA. That is, the helical path may comprise a partial arc (i.e., <360°), a complete arc (i.e., 360°) or a more than complete arc (i.e., >360°) along the inner wall of a vessel about the longitudinal axis of the vessel. In some embodiments, however, the arc is not substantially in one plane normal to the central axis of the artery, but instead preferably defines an obtuse angle with the central axis of the artery.
  • A. The Helical Structure
  • FIG. 4A is a plan view of an embodiment of a therapeutic or treatment assembly 21 for use with a treatment device (e.g., treatment device 12) in accordance with an embodiment of the technology, and FIG. 4B is an isometric view of the therapeutic assembly 21 of FIG. 4A. The energy delivery elements 24 depicted in FIGS. 4A and 4B are merely for illustrative purposes, and it will be appreciated that the treatment assembly 21 can include a different number and/or arrangement of energy delivery elements 24.
  • As shown in FIGS. 4A and 4B, a helix may be characterized, at least in part, by its overall diameter D, length L, helix angle α (an angle between a tangent line to the helix and its axis), pitch HP (longitudinal distance of one complete helix turn measured parallel to its axis), and number of revolutions (number of times the helix completes a 360° revolution about its axis).
  • In particular, the deployed or expanded configuration of the helix may be characterized by its axial length L along the axis of elongation in free space, e.g., not restricted by a vessel wall or other structure. As the helical support structure 22 radially expands from its delivery state, its diameter D increases and its length L decreases. That is, when the helical structure deploys, a distal end 22 a moves axially towards the proximal end 22 b (or vice versa). Accordingly, the deployed length L is less than the unexpanded or delivery length. In certain embodiments, only one of the distal end portion 22 a or the proximal end portion 22 b of the support structure 22 is fixedly coupled to the elongated shaft 16 or an extension thereof. In other embodiments, the support structure 22 may be transformed to its deployed or expanded configuration by twisting the distal and proximal end portions 22 a and 22 b relative to one another.
  • Referring to FIG. 4B, the deployed helically-shaped support structure 22 optionally comprises a distal extension 26 a distal to the helical portion that is relatively straight and may terminate with an atraumatic (e.g., rounded) tip 50. The distal extension 26 a including the tip 50 may reduce the risk of injuring the blood vessel as the helical structure is expanding and/or as a delivery sheath is retracted, and may facilitate alignment of the helical structure in a vessel as it expands. In some embodiments, the distal extension 26 a is generally straight (but flexible) and has a length of less than about 40 mm (e.g., between 2 mm and 10 mm). The tip 50 can be made from a polymer or metal that is fixed to the end of the structural element by adhesive, welding, crimping, over-molding, and/or solder. In other embodiments, the tip 50 may be made from the same material as the structural element and fabricated into the tip 50 by machining or melting. In other embodiments, the distal extension 26 a may have a different configuration and/or features. For example, in some embodiments the tip 50 may comprise an energy delivery element or a radiopaque marker. Further, the distal extension 26 a is an optional feature that may not be included in all embodiments.
  • The helical structure may also optionally have a proximal extension 26 b that is relatively straight compared to the helically shaped region of the support structure 22. The proximal extension 26 b, for example, may be an extension of the support structure 22 and may have a length between 0 mm and 40 mm (e.g., between about 2 and 10 mm). Alternatively, the proximal extension 26 b may be comprised of a separate material (e.g., a polymer fiber) with more flexibility than the rest of the support structure 22. The proximal extension 26 b is configured to provide a flexible connection between the helical region of the support structure 22 and the distal end of the elongated shaft 16 (FIG. 1). This feature is expected to facilitate alignment of the deployed helical support structure 22 with the vessel wall by reducing the force transferred from the elongated shaft 16 to the helical region of the helical structure 22. This may be useful, for example, when the elongated shaft is biased toward a side of the vessel wall or if the elongated shaft moves relative to the vessel wall allowing the helical structure to remain positioned.
  • Referring back to FIGS. 4A and 4B together (and with reference to FIGS. 3A and 3B), the dimensions of the deployed helically-shaped structure 22 are influenced by its physical characteristics and its configuration (e.g., expanded vs. unexpanded), which in turn may be selected with renal artery geometry in mind. For example, the axial length L of the deployed helical structure may be selected to be no longer than a patient's renal artery (e.g., the length 54 of renal artery RA of FIGS. 3A and 3B). For example, the distance between the access site and the ostium of the renal artery (e.g., the distance from a femoral access site to the renal artery is typically about 40 cm to about 55 cm) is generally greater than the length of a renal artery from the aorta and the most distal treatment site along the length of the renal artery, which is typically less than about 7 cm. Accordingly, it is envisioned that the elongated shaft 16 (FIG. 1) is at least 40 cm and the helical structure is less than about 7 cm in its unexpanded length L. A length in an unexpanded configuration of no more than about 4 cm may be suitable for use in a large population of patients and provide a long contact area when in an expanded configuration and, in some embodiments, provide a long region for placement of multiple energy delivery elements; however, a shorter length (e.g., less than about 2 cm) in an unexpanded configuration may be used in patients with shorter renal arteries. The helical structure 22 may also be designed to work with typical renal artery diameters. For example, the diameter 52 (FIG. 3A) of the renal artery RA may vary between about 2 mm and about 10 mm. In a particular embodiment, the placement of the energy delivery elements 24 on the helical structure 22 may be selected with regard to an estimated location of the renal plexus RP relative to the renal artery RA.
  • In another specific embodiment, a section or support structure of the therapeutic assembly 21, when allowed to fully deploy to an unconstrained configuration (i.e., outside of the body as shown in FIGS. 4A and 4B), comprises a helical shape having a diameter D less than about 15 mm (e.g., about 12 mm, 10 mm, 8 mm, or 6 mm); a length L less than or equal to about 40 mm (e.g., less than about 25 mm, less than about 20 mm, less than about 15 mm); a helix angle α of between about 20° and 75° (e.g., between about 35° and 55°); a range of revolutions between 0.25 and 6 (e.g., between 0.75 and 2, between 0.75 and 1.25); and a pitch HP between about 5 mm and 20 mm (e.g., between about 7 mm and 13 mm). In another example, the therapeutic assembly 21 may be configured to expand radially from its delivery state with a diameter about its central axis being approximately 10 mm to a delivery state in which the energy delivery elements 24 are in contact with the artery wall. The foregoing dimensions/angles are associated with specific embodiments of the technology, and it will be appreciated that therapeutic assemblies configured in accordance with other embodiments of the technology may have different arrangements and/or configurations.
  • In some embodiments, the deployed helically-shaped support structure 22 may be generally cylindrical (i.e., a helical diameter can be generally consistent along a majority of its length). It is also contemplated, however, that the structure 22 may have variations such as a conical helical shape, a tapered structural element, clockwise or counterclockwise pathway, consistent or varied pitch.
  • In one embodiment, the support structure 22 can include a solid structural element, e.g., a wire, tube, coiled or braided cable. The support structure 22 may be formed from biocompatible metals and/or polymers, including polyethylene terephthalate (PET), polyamide, polyimide, polyethylene block amide copolymer, polypropylene, or polyether ether ketone (PEEK) polymers. In some embodiments, the support structure 22 may be electrically nonconductive, electrically conductive (e.g., stainless steel, nitinol, silver, platinum, nickel-cobalt-chromium-molybdenum alloy), or a combination of electrically conductive and nonconductive materials. In one particular embodiment, for example, the support structure 22 may be formed of a pre-shaped material, such as spring temper stainless steel or nitinol. Furthermore, in particular embodiments, the structure 22 may be formed, at least in part, from radiopaque materials that are capable of being fluoroscopically imaged to allow a clinician to determine if the treatment assembly 21 is appropriately placed and/or deployed in the renal artery. Radiopaque materials may include, for example, barium sulfate, bismuth trioxide, bismuth subcarbonate, powdered tungsten, powdered tantalum, or various formulations of certain metals, including gold and platinum, and these materials may be directly incorporated into structural elements 22 or may form a partial or complete coating on the helical structure 22.
  • Generally, the helical structure 22 may be designed to apply a desired outward radial force to the renal artery wall 55 (FIGS. 3A and 3B) when inserted and expanded to contact the inner surface of the renal artery wall 55 (FIGS. 3A and 3B). The radial force may be selected to avoid injury from stretching or distending the renal artery RA when the helical structure 22 is expanded against the artery wall 55 within the patient. Radial forces that may avoid injuring the renal artery RA yet provide adequate stabilization force may be determined by calculating the radial force exerted on an artery wall by typical blood pressure. For example, a suitable radial force may be less than or equal to about 300 mN/mm (e.g., less than 200 mN/mm). Factors that may influence the applied radial force include the geometry and the stiffness of the support structure 22. In one particular embodiment, the support structure 22 is about 0.003-0.009 inch (0.08-0.23 mm) in diameter. Depending on the composition of the support structure 22, the structural element diameter may be selected to facilitate a desired conformability and/or radial force against the renal artery when expanded. For example, a support structure 22 formed from a stiffer material (e.g., metal) may be thinner relative to a support structure 22 formed from a highly flexible polymer to achieve similar flexibilities and radial force profiles. The outward pressure of the helical support structure 22 may be assessed in vivo by an associated pressure transducer.
  • In addition, certain secondary processes, including heat treating and annealing may harden or soften the fiber material to affect strength and stiffness. In particular, for shape-memory alloys such as nitinol, these secondary processes may be varied to give the same starting material different final properties. For example, the elastic range or softness may be increased to impart improved flexibility. The secondary processing of shape memory alloys influences the transition temperature, i.e., the temperature at which the structure exhibits a desired radial strength and stiffness. In embodiments that employ shape memory properties, such as shape memory nitinol, this transition temperature may be set at normal body temperature (e.g., around 37° C.) or in a range between about 37° C. and 45° C. In other embodiments that comprise super elastic nitinol, a transition temperature can be well below body temperature, for example below 0° C. Alternatively, the helical structure may be formed from an elastic or super elastic material such as nitinol that is thermally engineered into a desired helical shape. Alternatively, the helical structure 22 may be formed from multiple materials such as one or more polymers and metals.
  • Referring back to FIGS. 3B and 3C together, it should be understood that the support structure 22 of the treatment assembly 21, when not inserted into a patient, is capable of deploying to a maximum diameter that is larger than the diameter in its delivery state. Further, the helically-shaped structure 22 may be sized so that the maximum diameter is larger than the lumen diameter 52 of the renal artery RA. When inserted into a patient and transformed to the deployed state, however, the helically-shaped structure 22 expands radially to span the renal artery lumen and, at its largest circumferential section, is approximately or slightly less than (e.g., in embodiments in which the energy delivery elements 24 fill some of the space) the diameter 52 of the renal artery RA. A slight amount of vessel distension may be caused without undue injury and the structure 22 may expand such that its largest circumferential section is slightly more than the diameter 52 of the renal artery RA, or such that one or more energy delivery elements 24 are slightly pressed into the wall 55 of the renal artery RA. A helically-shaped assembly or array that causes slight and non-injurious distension of an artery wall 55 may advantageously provide stable contact force between the energy delivery elements 24 and the artery wall 55 and/or hold the energy delivery elements 24 in place even as the artery moves with respiratory motion and pulsing blood flow. Because this diameter 52 of the renal artery RA varies from patient to patient, the treatment assembly 21 may be capable of assuming a range of diameters between the delivery diameter and the maximum diameter.
  • As provided above, one feature of the deployed therapeutic assembly 21 in the helical configuration is that the energy delivery elements 24 associated with the helical structure may be placed into stable contact with a vessel wall to reliably create consistent lesions. Further, multiple energy delivery elements 24 may be placed along the helical structure with appropriate spacing to achieve a desired lesion configuration within the target vessel. Another feature of several embodiments of the therapeutic assembly 21 having the helical configuration described above is that the assembly may be expanded to fit within a relatively wide range of different vessel diameters and/or with various tortuosities.
  • B. Size and Configuration of the Energy Delivery Elements
  • It should be understood that the embodiments provided herein may be used in conjunction with one or more energy delivery elements 24. As described in greater detail below, the deployed helically-shaped structure carrying the energy delivery elements 24 is configured to provide a therapeutic energy delivery to the renal artery without any repositioning. Illustrative embodiments of the energy delivery elements 24 are shown in FIGS. 5A-5D. The energy delivery elements 24 associated with the helical structure 22 may be separate elements or may be an integral part of the helical structure 22. In some patients, it may be desirable to use the energy delivery element(s) 24 to create a single lesion or multiple focal lesions that are spaced around the circumference of the renal artery. A single focal lesion with desired longitudinal and/or circumferential dimensions, one or more full-circle lesions, multiple circumferentially spaced focal lesions at a common longitudinal position, spiral-shaped lesions, interrupted spiral lesions, generally linear lesions, and/or multiple longitudinally spaced discrete focal lesions at a common circumferential position alternatively or additionally may be created. In still further embodiments, the energy delivery elements 24 may be used to create lesions having a variety of other geometric shapes or patterns.
  • Depending on the size, shape, and number of the energy delivery elements 24, the formed lesions may be spaced apart around the circumference of the renal artery and the same formed lesions also may be spaced apart along the longitudinal axis of the renal artery. In particular embodiments, it is desirable for each formed lesion to cover at least 10% of the vessel circumference to increase the probability of affecting the renal plexus. Furthermore, to achieve denervation of the kidney, it is considered desirable for the formed lesion pattern, as viewed from a proximal or distal end of the vessel, to extend at least approximately all the way around the circumference of the renal artery. In other words, each formed lesion covers an arc of the circumference, and each of the lesions, as viewed from an end of the vessel, abut or overlap adjacent or other lesions in the pattern to create either an actual circumferential lesion or a virtually circumferential lesion. The formed lesions defining an actual circumferential lesion lie in a single plane perpendicular to a longitudinal axis of the renal artery. A virtually circumferential lesion is defined by multiple lesions that may not all lie in a single perpendicular plane, although more than one lesion of the pattern can be so formed. At least one of the formed lesions comprising the virtually circumferential lesion is axially spaced apart from other lesions. In a non-limiting example, a virtually circumferential lesion can comprise six lesions created in a single helical pattern along the renal artery such that each lesion spans an arc extending along at least one sixth of the vessel circumference such that the resulting pattern of lesions completely encompasses the vessel circumference when viewed from an end of the vessel. In other examples, however, a virtually circumferential lesion can comprise a different number of lesions. It is also desirable that each lesion be sufficiently deep to penetrate into and beyond the adventitia to thereby affect the renal plexus. However, lesions that are too deep (e.g., >5 mm) run the risk of interfering with non-target tissue and tissue structures (e.g., a renal vein) so a controlled depth of energy treatment is also desirable.
  • As shown in FIGS. 4A and 4B, energy delivery elements 24 may be distributed on the helical structure 22 in a desired arrangement. For example, the axial distances between the energy delivery elements 24 may be selected so that the edges of the lesions formed by individual energy delivery elements 24 on the renal artery wall 55 are overlapping or non-overlapping. One or both of the axial distances xx or yy may be about 2 mm to about 1 cm. In a particular embodiment, the axial distances xx or yy may be in the range of about 2 mm to about 5 mm. In another embodiment, the energy delivery elements 24 may be spaced apart about 30 mm. In still another embodiment, the energy delivery elements 24 are spaced apart about 11 mm. In yet another embodiment, the energy delivery elements 24 are spaced apart about 17.5 mm. Further, the axial distance xx may be less than, about equal to, or greater than the axial distance yy.
  • Spacing of energy delivery elements 24 may be characterized by a helical length distance zz, that is, the distance between energy delivery elements along the path of the helical structure 22. The helical length distance zz may be chosen based on the size of lesions created by energy delivery elements 24 so the lesions either overlap or do not overlap. In some embodiments, the energy delivery elements 24 are both longitudinally and circumferentially offset from one another. FIG. 4C, for example, is an end view of the helical structure 22 showing the angular offset or separation of the energy delivery elements 24 from one another around the circumference of the deployed helical structure 22. In particular, energy delivery element 24 c is offset from energy delivery element 24 a by angle 150 and offset from energy delivery element 24 b by angle 152. The offset angles may be selected such that, when energy is applied to the renal artery via energy delivery elements 24 a, 24 b, and 24 c, the lesions may or may not overlap circumferentially.
  • FIG. 4D is a side view of a vessel with formed lesions 340 that circumferentially and/or longitudinally overlap, but do not overlap along a helical path. More specifically, lesions 340 can be formed by energy delivery elements 24 to have a circumferential overlap 341 as viewed from one end of the vessel (e.g., FIG. 4C) and/or a longitudinal overlap 342, but may not produce a helical length overlap, instead forming a helical length gap 343. For example, energy delivery elements 24 may take the form of electrodes for applying an electrical field of RF energy to a vessel wall and be configured to produce lesions that are about 5 mm in diameter with the electrodes spaced apart by helical length distance of about 6 to 7 mm. Depending on the number and positioning of the energy delivery elements 24, a helical lesion pattern with any suitable number of turns may be formed. As such, the treatment device 12 may employ a single energy application to form a complex lesion pattern. It should be noted that the embodiments illustrated in FIGS. 4A-4C are exemplary, may be schematic in nature, may not correlate exactly to one another, and are shown only for the purposes of clarifying certain aspects of the technology. As such, the number and spacing of energy delivery elements 24 are different in each of FIGS. 4A-4C, and lesions formed by the illustrated embodiments may not create a sufficiently overlapping pattern to achieve a virtually circumferential lesion as described above, particularly when applying energy in only one deployment of the treatment assembly 21 without repositioning.
  • Referring back to FIG. 3B, the individual energy delivery elements 24 are connected to energy generator 26 (FIG. 1) and are sized and configured to contact an internal wall of the renal artery. In the illustrated embodiment, the energy delivery element 24 may be operated in a monopolar or unipolar mode. In this arrangement, a return path for the applied RF electric field is established, e.g., by an external dispersive electrode (shown as element 38 in FIGS. 1 and 2), also called an indifferent electrode or neutral electrode. The monopolar application of RF electric field energy serves to ohmically or resistively heat tissue in the vicinity of the electrode. The application of the RF electrical field thermally injures tissue. The treatment objective is to thermally induce neuromodulation (e.g., necrosis, thermal alteration or ablation) in the targeted neural fibers. The thermal injury forms a lesion in the vessel wall. Alternatively, a RF electrical field may be delivered with an oscillating or pulsed intensity that does not thermally injure the tissue whereby neuromodulation in the targeted nerves is accomplished by electrical modification of the nerve signals.
  • The active surface area of the energy delivery element 24 is defined as the energy transmitting area of the element 24 that may be placed in intimate contact against tissue. Too much contact area between the energy delivery element and the vessel wall may create unduly high temperatures at or around the interface between the tissue and the energy delivery element, thereby creating excessive heat generation at this interface. This excessive heat may create a lesion that is circumferentially too large. This may also lead to undesirable thermal application to the vessel wall. In some instances, too much contact can also lead to small, shallow lesions. Too little contact between the energy delivery element and the vessel wall may result in superficial heating of the vessel wall, thereby creating a lesion that is too small (e.g., <10% of vessel circumference) and/or too shallow.
  • The active surface area of contact (ASA) between the energy delivery element 24 and the inner vessel wall (e.g., renal artery wall 55) has great bearing on the efficiency and control of the generation of a thermal energy field across the vessel wall to thermally affect targeted neural fibers in the renal plexus. While the ASA of the energy delivery element is important to creating lesions of desirable size and depth, the ratio between the ASA and total surface area (TSA) of the energy delivery element 24 and electrode 46 is also important. The ASA to TSA ratio influences lesion formation in two ways: (1) the degree of resistive heating via the electric field, and (2) the effects of blood flow or other convective cooling elements such as injected or infused saline. For example, an RF electric field causes lesion formation via resistive heating of tissue exposed to the electric field. The higher the ASA to TSA ratio (i.e., the greater the contact between the electrode and tissue), the greater the resistive heating, e.g., the larger the lesion that is formed. As discussed in greater detail below, the flow of blood over the non-contacting portion of the electrode (TSA minus ASA) provides conductive and convective cooling of the electrode, thereby carrying excess thermal energy away from the interface between the vessel wall and electrode. If the ratio of ASA to TSA is too high (e.g., more than 50%), resistive heating of the tissue may be too aggressive and not enough excess thermal energy is being carried away, resulting in excessive heat generation and increased potential for stenotic injury, thrombus formation and undesirable lesion size. If the ratio of ASA to TSA is too low (e.g., 10%), then there is too little resistive heating of tissue, thereby resulting in superficial heating and smaller and shallower lesions. In a representative embodiment, the ASA of the energy delivery elements 24 contacting tissue may be expressed as

  • 0.25TSA≦ASA≦0.50TSA
  • An ASA to TSA ratio of over 50% may still be effective without excessive heat generation by compensating with a reduced power delivery algorithm and/or by using convective cooling of the electrode by exposing it to blood flow. As discussed further below, electrode cooling can be achieved by injecting or infusing cooling liquids such as saline (e.g., room temperature saline or chilled saline) over the electrode and into the blood stream.
  • Various size constraints for an energy delivery element 24 may be imposed for clinical reasons by the maximum desired dimensions of the guide catheter, as well as by the size and anatomy of the renal artery lumen itself. In some embodiments such as those shown in FIGS. 13 and 25, the maximum outer diameter (or cross-sectional dimension for non-circular cross-section) of the energy delivery element 24 may be the largest diameter encountered along the length of the elongated shaft 16 distal to the handle assembly 34. As previously discussed, for clinical reasons, the maximum outer diameter (or cross-sectional dimension) of the energy delivery element 24 is constrained by the maximum inner diameter of the guide catheter through which the elongated shaft 16 is to be passed through the intravascular path 14. Assuming that an 8 French guide catheter (which has an inner diameter of approximately 0.091 inch (2.31 mm)) is, from a clinical perspective, the largest desired catheter to be used to access the renal artery, and allowing for a reasonable clearance tolerance between the energy delivery element 24 and the guide catheter, the maximum diameter of the electrode 46 is constrained to about 0.085 inch (2.16 mm). In the event a 6 French guide catheter is used instead of an 8 French guide catheter, then the maximum diameter of the energy delivery element 24 is constrained to about 0.070 inch (1.78 mm), e.g., about 0.050 inch (1.27 mm). In the event a 5 French guide catheter is used, then maximum diameter of the energy delivery element 24 is constrained to about 0.053 inch (1.35 mm).
  • Based upon these constraints and the aforementioned power delivery considerations, the energy delivery element 24 may have an outer diameter of from about 0.049 to about 0.051 inch (1.24 mm-1.30 mm). The energy delivery elements 24 also may have a minimum outer diameter of about 0.020 inch (0.51 mm) to provide sufficient cooling and lesion size. In some embodiments, the energy delivery element 24 may have a length of about 1 mm to about 3 mm. In some embodiments in which the energy delivery element 24 is a resistive heating element, the energy delivery element 24 have a maximum outer diameter from about 0.049 to 0.051 inch (1.24 mm-1.30 mm) and a length of about 10 mm to 30 mm. One embodiment of energy delivery elements 24, for example, provides for a multiple array of 4-6 electrodes disposed about a support structure (e.g., a tubular structure). The energy delivery elements 24, for example, may be gold electrodes or alternatively, platinum, platinum-iridium, or another suitable material. In one particular embodiment, the electrodes may measure about 0.030 inch ID×0.0325 OD inch×0.060 inch in length (0.76 mm×0.83 mm×1.52 mm). In still another particular embodiment, the electrodes may measure 0.029 inch ID×0.033 inch OD×0.060 inch length (0.72 mm×0.83 mm×1.52 mm). In yet another particular embodiment, the electrodes may measure 0.038 inch ID×0.042 inch OD×0.060 inch length (0.97 mm×1.07 mm×1.52 mm). Moreover, the electrodes may be appropriately electrically insulated from the support structure with the supply wire array of each of the electrodes jacketed in a polymer so as to provide for a compact packaged electrode array assembly about the support structure 22.
  • In other embodiments, the outer diameter of the treatment device 12 may be defined by the one or more energy delivery elements 24 and may be further defined by elements such as e.g., control wire 168 as shown in FIG. 8A. For example, particular embodiments may be used with an 8 French guide catheter and may comprise energy delivery element(s) 24 with a diameter between about 0.049 to 0.053 inch (1.24 mm to 1.35 mm) and a control wire with a diameter between about 0.005 to 0.015 inch (0.13 mm to 0.38 mm) in diameter. In other embodiments, however, the arrangement and/or dimensions of the energy delivery elements 24 and/or control wire may vary.
  • In certain embodiments, the helical structure 22 may be formed of an electrically conductive material. For example, the helical structure 22 may be made from nitinol wire, cable, or tube. As shown in FIG. 5E, wire leads 19 may connect the helical structure 22 to energy generator 26. The helical structure 22 forms a contact region with the renal artery wall and acts as the energy delivery element 24. In this configuration, the helical structure 22 is capable of producing a continuous helical lesion. A helical structure 22 that is configured to be an energy delivery element 24 may optionally comprise sensors 33 positioned on, in, and/or proximate to the helical structure 22 and may be electrically connected to supply wires 35.
  • In other embodiments, the electrically conductive helical structure 22 is insulated at least in part. That is, the conductive helical structure is partially covered with an electrically insulating material and the uncovered portions of the helical structure 22 serve as one or more conductive energy delivery elements 24. The energy delivery elements 24 may be any size, shape, or number, and may be positioned relative to one another as provided herein.
  • Energy delivery element 24 may be configured to deliver thermal energy, i.e., to heat up and conduct thermal energy to tissue. For example, energy delivery elements may be an electrically resistive element such as a thermistor or a coil made from electrically resistive wire so that when electrical current is passed through the energy delivery element heat is produced. An electrically resistive wire may be for example an alloy such as nickel-chromium with a diameter for example between 48 and 30 AWG. The resistive wire may be electrically insulated for example with polyimide enamel.
  • In certain embodiments, the energy delivery elements 24 may be angularly repositioned relative to the renal artery during treatment. Referring back to FIGS. 1 and 2, for example, this angular repositioning may be achieved by compressing the therapeutic assembly 21 and rotating the elongated shaft 16 of the treatment device 12 via the handle assembly 34. In addition to the angular or circumferential repositioning of the energy delivery elements 24, the energy delivery elements 24 optionally may also be repositioned along the lengthwise or longitudinal dimension of the renal artery. This longitudinal repositioning may be achieved, for example, by translating the elongated shaft 16 of treatment device 12 via handle assembly 34, and may occur before, after, or concurrent with angular repositioning of the energy delivery elements 24. With reference to FIG. 3B, repositioning the energy delivery elements 24 in both the longitudinal and angular dimensions places the energy delivery elements 24 in contact with the interior wall 55 of the renal artery RA at a second treatment site for treating the renal plexus RP. In operation, energy may then be delivered via the energy delivery elements 24 to form a second focal lesion at this second treatment site. For embodiments in which multiple energy delivery elements 24 are associated with the helical structure, the initial treatment may result in two or more lesions, and repositioning may allow additional lesions to be created.
  • In certain embodiments, the lesions created via repositioning of the helically-shaped support structure 22 are angularly and longitudinally offset from the initial lesion(s) about the angular and lengthwise dimensions of the renal artery RA, respectively. The composite lesion pattern created along the renal artery RA by the initial energy application and all subsequent energy applications after any repositioning of the energy delivery element(s) 24 may effectively result in a discontinuous lesion (i.e., it is formed from multiple, longitudinally and angularly spaced treatment sites).
  • In an alternative embodiment, the energy delivery element 24 may be in the form of an electrically conductive wire. As shown in FIG. 5D, for example, a conductive wire 500 may be wound about the helical structure 22 to form a coiled electrode 24′. The coiled electrode 24′ may provide increased surface area for delivering energy. For example, the coiled electrode 24′ may form a generally continuous helical lesion in a single energy application. The coiled electrode 24′ may be wound in any manner about the helical structure 22, depending on the desired lesion. For example, the coiled electrode 24′ may form a continuous path along a length of the helix or the coiled structure may form one or more short discrete electrodes separated by non-conducting sections. In other embodiments, portions of the coiled electrode 24′ may be positioned on the helical structure to come in contact with the vessel wall when the helical structure is expanded, while other portions of the coiled electrode 24′ may be positioned away from the vessel wall when the helical structure is expanded to allow lesions to be discontinuous. Further, in such an arrangement, regions of the coiled electrode 24′ that do not contact the renal artery may contribute to cooling of the energy delivery elements 24′, as described in greater detail below. The positioning and number of conductive portions forming the energy delivery elements 24′ may be selected according to a desired lesion pattern.
  • In the embodiments shown in FIGS. 5A and 5B, energy delivery elements 24 preferably comprise metal electrodes with rounded ends and a lumen. The nitinol helical support structure 22 is preferably electrically insulated (e.g., with PET) and the electrodes 24 are mounted over the insulation. Supply wires 25 connect the electrodes to an energy source (not shown) and deliver energy (e.g., RF electrical current) to the electrodes 24. The rounded ends reduce mechanical irritation to the vessel wall and provide a more consistent current density when energy is delivered compared to electrodes with square or sharper ends. The energy delivery elements 24 may alternatively comprise other forms as noted, such as a coil electrode 24′ described above with reference to FIG. 5D. In another embodiment, the structural element 510 that forms the helical structure 22 may be the energy delivery element 24′ itself, as seen, for example in FIG. 5C.
  • III. SELECTED EMBODIMENTS OF RENAL DENERVATION SYSTEMS
  • The representative embodiments provided herein include features that may be combined with one another and with the features of other disclosed embodiments. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions should be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another.
  • FIG. 6A illustrates an embodiment of a treatment device 112 including an elongated shaft 116 having different mechanical and functional regions configured in accordance with an embodiment of the technology. The elongated shaft 116 of the treatment device 112, for example, includes a distal region with a therapeutic or treatment assembly 121 for delivery and deployment at a renal artery site for treatment and, in particular, for renal denervation. Disposed at a proximal end of the elongated shaft 116 is a handle assembly 134 for manipulation of the elongated shaft 116 and the therapeutic assembly 121. More specifically, the handle assembly 134 is configured with an actuator 136 (schematically shown) to provide for remote operation of a control member (e.g., control wire 168 of FIG. 6E or 8A) for controlling or transforming the therapeutic assembly 121 between a delivery state and a deployed state. Further details regarding suitable handle assemblies may be found, for example, in U.S. patent application Ser. No. 12/759,641, “Handle Assemblies for Intravascular Treatment Devices and Associated System sand Methods” to Clark et al., which is incorporated herein by reference in its entirety.
  • The treatment device 112 is configured to deliver the therapeutic assembly 121 to a treatment site in a delivery (e.g., low-profile) state in which the assembly 121 is substantially linear (e.g., straight) such that energy delivery elements (not shown) carried by a support structure 122 of the treatment assembly 121 are substantially axially aligned along the support member 122. Once located at the treatment site within the renal artery, the handle assembly 134 is operated for actuation of a control member that transforms the therapeutic assembly 121 from the delivery state to a deployed state. In one embodiment, for example, the control member comprises a control wire 168 (FIG. 8A) disposed within an internal lumen of the tubular support structure 122. One end of the control wire 168 may be affixed at or near the distal end of the support structure 122, and the opposite end of the control wire 168 terminates within the handle assembly 134. As mentioned previously, the handle assembly 134 is configured for manipulating the control wire 168 to transform the therapeutic assembly 121 between the delivery and the deployed states. The tension in the control wire 168 provides for a proximally and axially directed force that acts on the support structure 122. Under the influence of the tension force in the control wire 168 and, in operation within a patient under the influence of a radial constraint of the patient's renal arterial wall, the support structure 122 deforms so as to deploy into the helical geometry to bring the energy delivery elements into stable contact with the wall of the renal artery.
  • To provide for the desired deformation upon deployment, the support structure 122 may be a tubular member having a plurality of slots, cuts, through holes, and/or openings selectively formed or disposed about the support structure 122. The tubular support structure 122 may have a number of features generally similar to the features of support structure 22 described above. For example, the support structure 122 may be formed from biocompatible metals and/or polymers, including PET, polyamide, polyimide, polyethylene block amide copolymer, polypropylene, or PEEK polymers, and the slots are preferably laser cut into the tubular structure in a desired configuration. In particular embodiments, the support structure 122 may be electrically nonconductive, electrically conductive (e.g., stainless steel, nitinol, silver, platinum nickel-cobalt-chromium-molybdenum alloy), or a combination of electrically conductive and nonconductive materials. In one particular embodiment, the support structure 122 may be formed of a pre-shaped material, such as spring temper stainless steel or nitinol. Moreover, in some embodiments the support structure 122 may be formed, at least in part, from radiopaque materials that are capable of being imaged fluoroscopically to allow a clinician to determine if the support structure 122 is appropriately placed and/or deployed in the renal artery. Radiopaque materials may include barium sulfate, bismuth trioxide, bismuth subcarbonate, powdered tungsten, powdered tantalum, or various formulations of certain metals, including gold, platinum, and platinum-iridium, and these materials may be directly incorporated into the support structure 122 or may form a partial or complete coating of the support structure 122.
  • The location, orientation and/or configuration of the slots, cuts, through holes, and/or openings formed or disposed about the support structure 122 define the deformation of the structure. Moreover, the slots, cuts, through holes, and/or openings can be varied along the tubular structure 122 so as to define varying regions of deformation along the structure. In the embodiment illustrated in FIG. 6A, for example, the tubular structure 122 includes a distal deflection region 122 a, an intermediate orientation region 122 b proximal to the distal deflection region 122 a, and a transition or flexible region 122 c proximal to the orientation region 122 b. As will be described in greater detail below, the deflection region 122 a is configured to have a substantially helical geometry upon deployment. The orientation region 122 b is configured to locate or bias the deflection region 122 a away from a longitudinal axis B of the elongated shaft 116 and toward a wall of the renal artery. The transition region 122 c is configured to provide flexibility to the treatment device 112 as the elongated shaft 112 is advanced through the sometimes tortuous intravascular path from the percutaneous access site to the targeted treatment site within the respective renal artery (as described above with reference to FIG. 2). Further details regarding various mechanical and functional aspects of the different regions of the treatment device 112 are described below.
  • FIG. 6B is a plan view of a slot pattern configured in accordance with one embodiment of the technology. Referring to FIGS. 6A and 6B together, for example, the deflection region 122 a may be defined by a plurality of substantially equal length transverse slots 128 arranged along the support structure 122 in a spiral fashion. The orientation region 122 b may be defined by a plurality of axially spaced transverse slots 130 in which at least two slots differ in length. Further, as best seen in FIG. 6A, the orientation region 122 b can have a smaller axial length than the deflection region 122 a. The transition region 122 c is located proximally of the orientation region 122 b and has an axial length greater than each of the deflection region 122 a and the orientation region 122 b. In the illustrated embodiment, the transition region 122 c can include a continuous spiral cut or slit 132 having a varying pitch along the support structure 122. In one embodiment, for example, the pitch of the spiral cut 132 can increase proximally along the elongated shaft 116. Further details regarding various mechanical and functional aspects of the regions of the treatment device 112 are described below.
  • FIG. 6C is a perspective view of the treatment device 112 including the support structure 122 in a delivery state (e.g., low-profile or collapsed configuration) outside of a patient in accordance with an embodiment of the present technology, and FIG. 6D is a perspective view of the support structure 122 in a deployed state (e.g., expanded configuration). For ease of understanding, the support structure 122 in FIGS. 6C and 6D is shown without energy delivery elements disposed about the support structure 122.
  • Referring to FIGS. 6C and 6D together, the support structure 122 comprises a tubular member having a central lumen to define a longitudinal axis B-B. As described above, the support structure 122 includes a proximal generally flexible transition region 122 c, an intermediate orientation region 122 b, and a distal deflection region 122 a. The support structure 122 is selectively transformable between the delivery state (FIG. 6C) and the deployed state (FIG. 6D) by application of a force having at least a proximally directed axial component and preferably applied at or near the distal end 126 a to transform distal deflection region 122 a and intermediate orientation region 122 b. In one embodiment, for example, an axial force applied at or near the distal end 126 a directed at least partially in the proximal direction deflects the distal deflection region 122 a of the support structure 122 such that it forms the helically-shaped support structure such as is shown in FIG. 6D (e.g., within the renal artery) to bring one or more energy delivery elements (not shown) into contact with the inner wall of the renal artery.
  • The Deflection Region
  • As mentioned above, to provide the support structure 122 with the desired deflection and deployment configuration, the deflection region 122 a includes a plurality of slots 128 a, 128 b, 128 c, . . . 128 n. Again, the plurality of slots 128 a-128 n are selectively formed, spaced, and/or oriented about the longitudinal axis B-B such that the distal deflection region 122 a deflects in a predictable manner to form a helical geometry in the deployed state within the renal artery. Outside of the renal artery or other lumen that may radially constrain deflection of the distal region 122 a, the distal region 122 a may define a non-helical geometry in its fully expanded configuration, such as, for example, a substantially circular geometry as shown in FIG. 6E. As shown therein, the control wire 168 is disposed in the central lumen of the support structure 122, and is anchored at or near the distal end 126 a. When the control wire 168 is placed under tension in the proximal direction, at least a portion of the deflection region 122 a (in the absence of any restriction in the radial direction) deflects from the substantially straight shape of FIG. 6C to form the substantial circular shape of FIG. 6E. More specifically, referring to FIGS. 6C-6E together, a portion of the deflection region 122 a deflects such that the deflection slots 128 a-n deform and close or approximately close (as shown schematically in FIG. 6E) and provide contact between the edges of the support structure 122 framing a central region in each slot 128. Further details regarding the configuration of the slots are described below.
  • The deflection region 122 a is arranged to deflect about a center of curvature Z to define a first radius of curvature r with respect to a first surface 122 d of the support member 122, and a second radius of curvature R with respect to a second surface 122 e. The second radius of curvature R is greater than the first radius of curvature r with the difference being the width or diameter d of the support member 122 measured at its outer surface. Under a radial constraint of, for example, the inner wall of a renal artery, the deflection region 122 a deforms to define a substantially helical deployed shape (as depicted in FIG. 6D) instead of the substantial circular shape defined in the absence of radial constraint (as depicted in FIG. 6E). Thus, the proportions of the substantially helical deployed shape (e.g., the diameter and pitch of the helix) can vary according to the inner diameter of the lumen (e.g., the renal artery lumen) within which the deflection region 122 a is deformed.
  • The arrangement and configuration of the slots 128 a-128 n (FIG. 6C) further define the geometry of the deflectable distal region 122 a. FIG. 6F, for example, schematically illustrates a slot pattern for slots 128 in accordance with one embodiment of the technology to illustrate the slot spacing and orientation about the deflection region 122 a of the support member 122. Although only four slots 128 a-d are shown in FIG. 6F, it will be appreciated that the deflection region 122 a can have any number of desired slots 128. Referring to FIGS. 6E and 6F together, the centers of the slots 128 are disposed and spaced along a progressive axis C-C. The progressive axis C-C defines a progressive angle θ with the longitudinal axis B-B of the support structure 122 (FIG. 6A) to define an angular spacing of y about the center of curvature Z (FIG. 6E) in the unconstrained deployed state. The centers of the slots 128 a-128 d are shown as substantially equidistantly spaced at a distance x. Alternatively, however, the center spacing between the slots may vary (x1, x2, etc.) along the progressive axis C-C. Each slot 128 further defines a maximum arc length L about the longitudinal axis B-B and a maximum slot width W in the direction of the longitudinal axis B-B.
  • The total number of slots 128 in the region 122 a under deflection multiplied by the slot width W populated in a specific length defines the first radius of curvature r in the deflected portion of the deflection region 122 a (when placed in an unconstrained deployed state). In one particular embodiment, for example, each slot ma have a width W ranging from about 0.0005 to 0.010 inch (0.01 to 0.25 mm) and a slot arc length L of about 0.0005 to 0.010 inch (0.01 to 0.25 mm) so as to define a first radius of curvature r in an unconstrained deflected state that ranges between about 3.5 to 6 mm (7 to 12 mm diameter). Minimizing the first radius of curvature r at a maximum application of axial force through the deflection region 122 a of the support member 122 defines the flexibility of the deflection region 122 a. Accordingly, the smaller the first radius of curvature r, the greater the flexibility; the greater the first radius of curvature r, the greater the stiffness. Thus, the flexibility and/or stiffness of the deflection region 122 a of the support member 122 can be defined by selecting the number and/or width of slots of the distal region 122 a. In one embodiment, for example, the deflection region 122 a can include approximately 2 to 100 slots, with each having a slot width W ranging from about 0.0005 to 0.010 inch (0.01 to 0.25 mm) and a slot arc length L of about 0.0005 to 0.010 inch (0.01 to 0.25 mm) so as to define a first radius of curvature r in an unconstrained deflected state that ranges between about 3.5 to 6 mm (7 to 12 mm diameter).
  • Because the first radius of curvature r of the deflection region 122 a is directly related to the number of slots 128, the number of slots 128 can be few in number so as to provide for a non-continuous radius of curvature in a segment of the deflection region 122 a such that the segment is substantially polygonal. FIG. 6G, for example, is a schematic plan view of a treatment device 112′ configured in accordance with another embodiment of the technology. A deflection region 122a of the treatment device 112′ may include a low or reduced number of deflection slots 128 (e.g., three slots 128 a-c are shown) such that the deflection region 122a defines a substantially polygonal geometry when under a tension load at its distal end (i.e., from control wire 168). In other embodiments, a different number of slots 128 may be used to selectively form a desired geometry for the treatment device 112′.
  • Referring back to FIGS. 6B and 6C and as noted previously, the deflection region 122 a is defined by a plurality of deflection slots 128 in which each slot 128 extends substantially transverse to the longitudinal axis B-B of the support structure 122 with the slots 128 being of substantially similar arc length. Moreover, with reference to FIG. 6F, the centers of the slots 128 of the deflection region 122 a are generally spaced apart along a progressive axis CC that is skewed from the longitudinal axis BB such that the slots 128 of the deflection region 122 a progress in a generally spiral fashion along the support structure 122 in the axial direction (as best seen in FIG. 6C). The plurality of slots 128 of the deflection region 122 a are selectively formed, spaced, and/or oriented about the longitudinal axis B-B such that the deflection region 122 a deflects or deforms in a predictable manner so as to preferably form a helical geometry when in a deployed state (e.g., within the renal artery).
  • Referring again to FIG. 6B, for example, the deflection region 122 a includes a pattern of deflection slots 128 arranged in accordance with one embodiment of the technology to illustrate the slot spacing and orientation about the support member 122 (FIG. 6A). The centers of the deflection slots 128 are disposed and spaced along progressive axis C-C. The progressive axis C-C defines a progressive angle θ1 with the longitudinal axis B-B of the support structure 122 (FIG. 6A). The progressive angle θ1 defines and, more particularly, directly corresponds to a pitch angle of the helical geometry defined by the support structure 122 when in a deployed state. The progressive angle θ1 can range from, for example, about zero degrees (0°) to about six degrees (6°), e.g., one-half degree, (0.5°), two degrees (2°), etc. The centers of the deflection slots 128 are shown as substantially equidistantly spaced apart. In other embodiments, however, the center spacing between slots 128 may vary along the progressive axis C-C. The total number of slots 128 defining the deflection region 122 a can be from about 2 to 100 slots (e.g., about 80 slots). In one particular embodiment, the total axial length of the deflection region 122 a is about one inch (2.54 cm). In other embodiments, however, the deflection region 122 a can have a different number of slots 128 and/or the slots can have different dimensions or arrangements relative to each other.
  • In one embodiment, each of the deflection slots 128 comprises a substantially rectangular central region 129 a that extends generally perpendicular to and about the central longitudinal axis B-B of the shaft 116. The elongate lateral walls of the central region 129 a define a slot width W therebetween (e.g., about 0.0015 inch (0.038 mm)) to define a maximum gap that may be closed when the slot 128 deforms during deflection of region 122 a. Each slot 128 further comprises lateral regions 129 b in communication or contiguous with the central region 129 a. In one embodiment, the lateral regions 129 b are substantially circular and have a diameter (e.g., 0.0060 inch (0.15 mm)) to define regions for stress relief at the ends of slots 128. The spacing between the centers of the substantially circular lateral regions 129 b define an arc length L (e.g., about 0.040 inch (1.02 mm)) about the longitudinal axis of the structure 122. In some embodiments, these lateral regions 129 b may be formed as elliptical cuts on a non-perpendicular angle relative to the longitudinal axis B-B of the support structure 122, 122′, 122″.
  • Alternate configurations of the deflection slots are possible. For example, the deflection slots can be more specifically formed to provide a desired flexibility and deflection in the deflection region 122 a of the support member 122. FIGS. 6H and 6I, for example, illustrate a deflection region 122 a″ having deflection slots 128′ configured in accordance with another embodiment of the technology. In this embodiment, the deflection slots 128′ extend substantially transverse to the progressive axis C-C and are substantially symmetrical about the progressive axis C-C. The slots 128′, for example, can be generally “I-shaped” and include a central region 129 a extending perpendicular to the progressive axis C-C with two enlarged lateral regions 129 b disposed about the central slot region 129 a. Further, the walls of the support structure 122″ forming the perimeter of each of the lateral regions 129 b define a substantially rectangular geometry preferably extending substantially parallel to the longitudinal axis B-B of the support structure 122″ with the corners of the rectangular-shaped openings being radiused. The central region 129 a of the slots 128′ can include a substantially circular cut-out region 129 c formed in communication with the lateral regions 129 b. Alternatively, in some embodiments the central region 129 c of the slots 128′ may be generally rectangular and not include a circular cut-out.
  • As best seen in FIG. 6I, the distal slots 128′ extend about the longitudinal axis B-B of the support structure 122″ at an arc length L′ of, for example, less than about 0.05 inch (1.27 mm), e.g., about 0.04 inch (1.02 mm). The lateral regions 129 b define the maximum width W′ of the deflection slot 128′ to be, for example, about 0.03 inch (0.76 mm). The circular portion 129 c of central region 129 a is contiguous with or in communication with the lateral regions and includes a central circular cut-out 129 c having a diameter of e.g., about 0.01 inch (0.25 mm). The central region 129 a defines a minimum width of, e.g., about 0.02 inch (0.51 mm) in the longitudinal direction of the support structure. In one particular embodiment, the total number of slots 128′ in the distal region is less than 30 slots (e.g., 25 slots), the slot spacing is about 0.03-0.04 inch (0.76-1.02 mm), and the slots are equally spaced apart in the distal deflection region 122″. In other embodiments, however, the distal region may have a different number of slots and/or the slots may have a different arrangement (e.g., different dimensions, different or non-equal spacing between slots, etc.).
  • Alternate slot, cut, and/or opening configurations can provide desired flexibility, stress-relief or other performance characteristics. FIG. 6J, for example, is an alternative slot arrangement 128″ that can be used, for example, in either the deflection region 122 a or the orientation region 122 b (described in greater detail below) of the support structure 122. The illustrative slot 128″ includes a central region 129a that extends substantially perpendicular and about the longitudinal axis B-B of the support structure 122. The opposed lateral walls of the central region 129a are generally arcuate, each defining a radius of curvature (e.g., about 0.06 inch (1.52 mm)) with a maximum gap WWW therebetween (e.g., about 0.005 inch (0.13 mm)) to define the maximum slot gap that may be partially or fully closed during deflection of the support structure 122. Further, disposed about the longitudinal axis B-B of the support structure 122 are lateral regions 129b in communication or contiguous with the central region 129a. The lateral regions 129b are substantially circular and each have a diameter (e.g., 0.005 inch (0.13 mm)) to define regions for stress relief. The spacing between the centers of the curved lateral regions 129b define a length LLL (e.g., about 0.04 inch (1.02 mm)) about the longitudinal axis B-B of the support structure 122. These lateral regions 129b may be formed, for example as elliptical cuts on a non-perpendicular angle relative to a longitudinal axis of the shaft.
  • The configuration of a slot in the deflection region 122 a and/or orientation region 122 b of the elongated shaft can impact the flexibility of the support structure 122. For example, as shown in FIGS. 6K and 6L, the inclusion (or absence) of the circular cut-out 129 c in the central region 129 a of a slot 128, 128′, 128″ can vary the number of contact points between the sidewalls of the slots disposed about the bisecting axis of the slot. FIG. 6K, for example, illustrates a portion of the distal region 122 a″ in a deflected or bent configuration. The central circular cut-out 129 c provides for two contact points 602 between the sidewalls of central region 129 a—one point of contact between each of the lateral regions 129 b and the central circular cut-out 129 c. In contrast and with reference to FIG. 6L, the absence of a central circular cut-out 129 c provides for a single contact point 602 between the walls of the central region 129 c when along a deflected portion of the distal region 122″.
  • It should also be noted that, in order to facilitate fabrication of the support members 122, 122′, 122″, the deflection slots 128, 128′, 128″ described above may be formed perpendicular or generally perpendicular to either the longitudinal axis B-B or the progressive axis C-C without impairing the ability of the support member 122, 122′, 122″ to form the desired helical geometry when in a deployed state.
  • Further, as described above with reference to FIG. 6E, when support structure 122 is transformed from the delivery state to the deployed state, slots 128, 128″, 128′″ are deformed such that the walls defining central regions 129 a, 129a (as shown, for example, in FIGS. 6B, 6I, and 6J) approach each other to narrow the corresponding gap widths W, WW, WWW up to and including fully closing the gap wherein one or more pairs of opposing contact points touch each other (as shown schematically in FIG. 6E and described above with reference to FIGS. 6K and 6L).
  • The Orientation Region
  • Referring back again to FIGS. 6A-6D and as discussed previously, disposed proximally of the deflection region 122 a is the orientation region 122 b defined by a plurality of orientation slots 130. It may be desirable to control the orientation of the helical axis relative to the longitudinal axis B-B of the support structure 122. For example, in a therapeutic assembly incorporating the support structure 122, it may be desirable to direct the therapeutic assembly in a selected direction away from the longitudinal axis B-B such that at least a portion of the deflection region 122 a is laterally off-set from the proximal end 126 b of the support structure 122 and/or a distal end of the elongated shaft 116. As best seen in FIG. 6D, for example, the orientation region 122 b can include orientation slots or openings 130 that are formed, spaced and/or oriented to provide for an orientation axis B-B that is skewed (e.g., from about 45 degrees (45°) to about 90 degrees (90°)) relative to the longitudinal axis B-B and orients the helically shaped geometry of the deflection region 122 a adjacent the renal artery wall with the helical axis directed axially along the renal artery.
  • The orientation slots 130 can have a variety of different arrangements/configurations. Referring to FIG. 6B (and with reference to FIG. 6M), for example, the centers of orientation slots 130 are disposed and spaced along an orientation axis D-D that is radially offset from the progressive axis C-C (e.g., by about 90° about the longitudinal axis B-B of the support structure 122). The orientation axis D-D may extend generally parallel to the longitudinal axis B-B or, alternatively, may be skewed at a selected angle relative to the longitudinal axis B-B (as described in greater detail below with reference to FIG. 6N). In the illustrated embodiment, the centers of the orientation slots 130 are shown as substantially equidistantly spaced apart. In other embodiments, however, the spacing between the individual slots 130 may vary along the orientation axis D-D. Each slot 130 defines a maximum arc length LL about the longitudinal axis B-B and a maximum slot width WW in the direction of the longitudinal axis B-B.
  • Referring to FIG. 6B, in one embodiment the orientation slots 130 can include groups of slots of varying arc length LL about the longitudinal axis B-B. For example, the orientation slots 130 can include a first group of orientation slots 130 a having a first arc length, a second group of orientation slots 130 b having a second arc length less than the first arc length of the first group of orientation slots 130 a, and a third group of orientation slots 130 c having a third arc length less than the second arc length of group 130 b. For example, in one particular embodiment, the first group of orientation slots 130 a has an arc length of about 0.038 inch (0.97 mm), the second group of orientation slots 130 b has an arc length of about 0.034 inch (0.86 mm), and the third group of orientation slots 130 c has an arc length of about 0.03 inch (0.76 mm). In other embodiments, however, the orientation slots 130 may have different sizes and/or arrangements relative to each other. For example, in some embodiments one or more groups of orientation slots 130 may have different slot widths (in addition to, or in lieu of, varying arc lengths).
  • In one embodiment, the total number of slots 130 defining the orientation region 122 b is less than 20 slots (e.g., about 5 to 15 slots, about 6 to 12 slots, etc.) equally spaced over the orientation region 122 b. Further, in one particular embodiment, the total axial length of the orientation region 122 b is about 0.2 to 0.25 inch (5.08 to 6.35 mm). In other embodiments, the orientation region 122 b may have a different number of slots and/or a different arrangement and/or dimensions.
  • Alternate configurations of the orientation slots are possible. For example, Referring back again to the pattern illustrated in FIG. 6I, orientation slots 130′ may be substantially elongated defining a preferably maximum arc length LL′ about the longitudinal axis B-B and a maximum slot width WW in the direction of the longitudinal axis B-B. In one particular embodiment, for example, each orientation slot 130′ has a width W′ ranging from about 0.0005 to 0.010 inch (0.01 mm to 0.03 mm) and a slot arc length LL′ of about 0.0005 to 0.010 inch (0.01 mm to 0.03 mm) so as to define a first radius of curvature r in an unconstrained deflected state that ranges between about 7 to 12 mm. In other embodiments, however, the orientation slots 130′ may have other dimensions and/or arrangements.
  • In the illustrated embodiment, the orientation slots 130′ extend generally perpendicular to the orientation axis D-D and are substantially symmetrical about the orientation axis D-D. The orientation slots 130′ are generally “I-shaped” having a central region 131 a extending perpendicular to the orientation axis D-D with two enlarged lateral regions 131 b disposed about the central slot region 131 a for stress relief. In this embodiment, the walls of the support structure 122″ forming the perimeter of each of the lateral regions 131 b can define, for example, a substantially rectangular geometry extending substantially parallel to the longitudinal axis B-B of the support structure 122″ with the corners of the rectangular-shaped openings being radiused (not shown). Further, central regions 131 a of the individual orientation slots 130′ may be generally rectangular, or may have another suitable shape.
  • Each of the orientation slots 130′ depicted in FIG. 6I can include a substantial rectangular central region 131 a that extends substantially perpendicular and about the longitudinal axis B-B of the support structure 122. The elongate lateral walls of the central region 131 a define a gap therebetween (e.g., about 0.0015 inch (0.038 mm)) to define the maximum closing gap of the slot during deflection of the structure 122. Each slot 130′ can also include lateral regions 131 b disposed about the longitudinal axis B-B and in communication or contiguous with the central region 131 a. The lateral regions 131 b define a substantially rectangular geometry preferably extending substantially parallel to the longitudinal axis B-B of the support structure 122″ with the corners of the rectangular-shaped openings being radiused to define regions for stress relief. The spacing between the centers of the substantially rectangular lateral regions 131 b define an arc length L (e.g., about 0.04 inch (1.02 mm)) about the longitudinal axis B-B of the support structure 122″. Alternatively, lateral regions 131 b may be formed as elliptical cuts on a non-perpendicular angle relative to the longitudinal axis B-B of the support structure 122, 122′, 122″.
  • In some embodiments, the total number of slots 130′ in the orientation region is generally less than ten slots, e.g., five slots, the slot spacing can be, e.g., about 0.03 to 0.04 inch (0.76 mm to 1.02 mm), and the slots 130′ can be equally spaced apart. Further, in some embodiments the orientation axis D-D can be generally parallel to the longitudinal axis B-B and radially offset from the progressive axis C-C at a minimum arc length distance of, e.g., about 0.01 inch (0.25 mm) over an angle ranging from about 50° to less than 90° about the longitudinal axis B-B of the support structure 122″.
  • In yet another embodiment, the orientation slots 130 may be disposed along an orientation axis that is substantially skewed with respect to the longitudinal axis B-B. FIG. 6N, for example, is a plan view of a slot pattern configured in accordance with another embodiment of the technology. In this embodiment, the orientation slots 130 are disposed on an orientation axis D2-D2 that may be skewed relative to the longitudinal axis B-B by an angle θ2 ranging from, e.g., about 0 degrees (0°) to about 45 degrees (45°). The angled orientation axis D2-D2 provides for an orientation region 122 b having a tapered helical geometry upon deployment of the support structure 122. FIG. 6O, for example, is a schematic illustration of a portion of a treatment device having a support structure including the slot pattern of FIG. 6N in a deployed state within a renal artery of a patient.
  • The Flexible/Transition Region
  • Referring again to FIG. 6A, disposed proximally of the orientation region 122 b is the flexible or transition region 122 c. As noted above, the flexible region 122 c can include, for example, the transitional helical or spiral slit or cut 132 having a variable pitch over its length. The variable pitch of the spiral cut 132 along the length of the flexible region 122 c provides the support structure 122 with variable flexibility along the length of the elongated shaft 116. In one embodiment, for example, the transitional cut 132 extends over an axial length of, e.g., about 170 mm initiating proximal to the orientation region 122 b. In other embodiments, however, the transitional cut 132 may have a different length.
  • As illustrated in FIGS. 6C and 6D, in some embodiments the pitch of the transition cut 132 may vary over the length of the transition cut to define multiple, different transition regions (four transition regions 132 a, 132 b, 132 c, and 132 d are shown in FIG. 6C). More specifically, in one embodiment, the cut 132 defines a first transitional portion 132 a having a first pitch by forming, e.g., five revolutions about the tubular support structure 122 at a spacing of 0.02 inch (0.51 mm) and transitions to a second transitional portion 132 b having a second pitch defined by, e.g., five revolutions at a spacing of 0.040 inch (1.02 mm). The cut 132 continues to define a third transitional portion 132 a having a third pitch defined by, e.g., ten revolutions at a spacing of 0.06 inch (1.52 mm) and transitions to a fourth pitch defined by, e.g., twenty revolutions at a spacing of 0.08 inch (2.03 mm). It should be appreciated in the above example that, considering each sequential transitional portion 132 in order from the distal end to the proximal end of transition region 122 c, the slit pitch spacing increases and the flexibility of tubular support structure 122 decreases.
  • The transitional cut 132 may have a generally constant width of, e.g., about 0.0005 inch (0.01 mm) over its length, or the width of the transitional cut 132 may vary over its length. The transitional cut 132 can also include at each end a substantially circular void contiguous with or in communication with the transitional cut. In other embodiments, however, the transitional cut 132 can have a different arrangement and/or different dimensions. For example, rather than having stepwise increases in pitch, the transitional cut 132 may have a continuously increasing pitch from the distal end to the proximal end of transition region 122 c.
  • Alternate slot, cut and/or opening configurations can provide for the desired flexibility, stress-relief or other performance characteristics in the flexible region 122 c in lieu of the transition cut 132. In some embodiments, for example, opening or apertures may be selectively formed in the elongated shaft 116 to provide the desired flexibility. The individual openings or apertures of the flexible region 122 c can, for example, have centers disposed along an axis that extends parallel to the central longitudinal axis B-B of the support structure 122. FIGS. 7A and 7B, for example, illustrate the support structure 122 with an alternate arrangement for the flexible region 122 c, having through holes or openings 132a, 132b, 132c that each extend through the tubular support structure 122. The openings 132′, for example, can be alternately disposed on axes that are angularly spaced from one another about the longitudinal axis B-B of the support structure 122. In the illustrated embodiment, for example, opening 132b is angularly disposed at 90° relative to the axially adjacent openings 132a and 132c. In other embodiments, however, the openings 132′ may have a different arrangement.
  • FIG. 8A is a broken perspective view in partial section of a treatment device 100 including a catheter having an elongated shaft 116 with a distal region 120 having a support structure 122 for delivery and deployment of a therapeutic or treatment assembly 121 at a target treatment site in a lumen and, in particular, for performing renal denervation within a renal artery. Disposed at a proximal end of the elongated shaft 116 is a handle assembly 134, shown schematically, for manipulation of the elongated shaft 116 and the therapeutic assembly 121. More specifically, the handle assembly 134 is configured to provide for remote operation of a control member 168 (e.g., a control wire) for controlling or transforming the therapeutic assembly 121 between a delivery state and a deployed state (shown in FIG. 8A).
  • The system 100 is configured to deliver the therapeutic assembly 121 to the treatment site in a delivery state (not shown) in which the therapeutic assembly 121 is substantially linear (e.g., straight) such that the energy delivery elements 124 are substantially axially aligned along the support member 122. Energy supply wires 25 may be disposed along an outer surface of the support member 122 and coupled to each of the energy delivery elements 124 for supplying treatment energy to the respective energy delivery elements 124. Once located at the treatment site within the renal artery, actuation of the control member 168 that transforms the therapeutic assembly 121 from the delivery state to the deployed state as shown. In the illustrated embodiment, the control wire 168 is disposed within the tubular support structure 122. One end of the control member 168 may be affixed at or near the distal end 126 a of the support structure 122 (e.g., terminating in a tip member 174). The opposite end of the control member 168 can terminate within the handle assembly 134 and be operably coupled to an actuator for transforming the therapeutic assembly 121 between the delivery and the deployed state.
  • The tension in the control member 168 can provide a proximal and/or axially directed force to the distal end 126 a of the support structure 122. For example, under the influence of the tension force in the control member 168, the distal region 122 b of the support structure 122 deflects. The distal deflection region 122 a preferably include a plurality of slots 128 (only two are shown as 128a and 128b). As described above, the slots 128a and 128b are disposed along a progressive axis. The slots 128a and 128b formed in the distal region 122 a of the support structure bias the deflection of the distal region 122 a so as to form one or more curved portions, each having a radius of curvature preferably defined by the number of deflection slots 128, the individual slot width, slot configuration, and/or slot arrangement. As the distal region 122 a continues to deflect, it radially expands placing one or more of the spaced-apart energy elements 124 into contact with the inner wall 55 of the renal artery. The support structure 122, when subject to the tension of the control wire 168 and the radial constraints of the vessel wall 55, is configured to form a substantially helical shape so as to axially space and radially offset the energy delivery elements 124 from one another. Moreover, because the deflection region 122 a of the support structure 122 is configured to form a helical geometry within the renal artery when under a tension load, the treatment assembly 121 is not expected to radially overload the wall 55 of the renal artery. Rather, the support structure 122 deforms to form the helix under a continuously increasing tension load.
  • As discussed above, the progressive angle of the axis (e.g., progressive axis C-C) along which the deflection slots 128, 128′, 128″ are disposed defines the helical angle of the resulting deployed arrangement. In one embodiment, an amount of tension to fully deploy the therapeutic assembly 121 is typically less than, for example, about 1.5 lbf (pound-force) (0.68 kgF) applied at the distal end 126 a of the therapeutic assembly 121, e.g., between about 1 lbf (0.45 kgF) to about 1.5 lbf (0.68 kgF). In the helically shaped deployed state of FIG. 8A, the slots 128′ are disposed along the interior surface of the helix with the supply wires 25 for the energy delivery elements 24 disposed on an outer surface of the helix so as to form a “spine” of the assembly. The supply wires 25 can extend along the length of the treatment device 112 to an appropriately configured energy generator (not shown).
  • The support structure 122 of the therapeutic assembly 121 includes a proximal portion that defines an orientation region 122 b of the assembly for locating the therapeutic assembly adjacent to the wall of the renal artery. As shown in FIG. 8A, the proximal region of the support structure 122 includes a plurality of orientation slots 130′. In operation, upon actuation of the handle assembly 134 to place the control wire 168 under tension, the orientation region 122 b deflects in a radially outward direction within the renal artery to locate the therapeutic assembly 121 into contact with the arterial wall 55. More specifically, the slots 130′ deform under the tension force so as to deflect the orientation region 122 b radially outward from the longitudinal axis B-B of the support structure 122. In the fully deployed state, the resultant helical geometry of the therapeutic assembly 121 at the distal end of the support structure 122 is preferably offset from the longitudinal axis B-B at the proximal end of the support structure 122 such that the helical axis H-H and the longitudinal axis B-B of the support structure 122 are non-coaxial. The axes H-H, B-B may be parallel to one another or, alternatively, skewed with respect to one another.
  • The proximal end of the support structure 122 can be coupled to a separate member forming the elongated shaft 116 of the device 112. Alternatively, the support structure 122 and the elongated shaft 116 may be a single unitary member that extends proximally from the distal end 126 a into the handle assembly 134. In one embodiment, the tubular support structure 122 is formed from a metallic shape-memory material (e.g., nitinol). Further, in one embodiment the support structure 122 can have an axial length of less than five inches (12.7 cm) and, more specifically, about two inches (5.08 cm); an outer diameter of about 0.020 inch (0.57 mm) and, more specifically, ranging between about 0.016 inch (0.41 mm) to about 0.018 inch (0.46 mm); a tubular wall thickness of less than 0.005 inch (0.13 mm) and, more particularly, about 0.003 inch (0.08 mm). In several embodiments, the elongated shaft 116 can be formed from stainless steel metal tubing having an outer diameter of, e.g., about 0.020 (0.57 mm) to about 0.060 inch (1.52 mm). In coupling the proximal support structure 122 to the elongated shaft 116, a joint 119 may be provided therebetween to provide the desired transfer of torque from the elongated shaft 116 to the support structure 122 when navigating to the treatment site. More specifically, each end of the support structure 122 and the elongated shaft 116 may respectively include mating notches that permit the ends of the tubular members to interlock with one another as shown in the joint assembly 120. In some embodiments, disposed about the joint 119 is a stainless steel sleeve that is crimped about the juncture to provide additional support to the joint 119.
  • As noted above, the control member 168 can be a control rod or wire that extends the axial length of the catheter device 112 from at or near the distal end 126 a of the support structure 122 to the handle assembly 134. The control wire 168 can be comprised of ultra high molecular weight (UHMW) fiber, such as for example high strength, gel-spun fiber sold under the trademark SPECTRA or other sufficiently strong polyethylene fiber. Alternatively, nitinol, a para-aramid synthetic fiber sold under the trademark KEVLAR, or other mono- or multi-filament types can be used provided they are compatible with the application and can transfer the tensile force to the distal end of the therapeutic assembly 121 over the length of the treatment device 112.
  • To provide the desired tensile force at the distal end of the therapeutic assembly 121, the control wire 168 may be anchored at or near the distal end 126 a of the support structure 122. FIGS. 8B-8D, for example, illustrate various anchoring configurations for the control wire 168. More specifically, as shown in FIG. 8B, the distal end 126 a of the support structure includes a slot adjacent the axial opening to tie and anchor the control wire 168 therethrough. In an alternate anchoring arrangement shown in FIG. 8C, the control wire 168 extends through the axial opening at the distal end 126 a. The control wire 168 can be encased in a coil 174 material to stop the control wire 168 from sliding proximally into the distal portion of the support structure 122. FIG. 8D illustrates another tip 174 configured in accordance with an embodiment of the disclosure. In this arrangement, the control wire 168 can be tripled-knotted to provide an enlarged surface of the control wire 168 on which to coat the polymer material that is formed into a tip.
  • Referring back to FIG. 8A, the control wire 168 can extend through the elongated shaft 116 to the handle assembly 134. In operation of the handle assembly 134 to tension and release the control wire 168 when transforming the therapeutic assembly between deployed and delivered states, friction occurs between the moving control wire 168 and the i