WO2018150314A1 - Capteur de force pour bout distal de cathéter - Google Patents

Capteur de force pour bout distal de cathéter Download PDF

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Publication number
WO2018150314A1
WO2018150314A1 PCT/IB2018/050857 IB2018050857W WO2018150314A1 WO 2018150314 A1 WO2018150314 A1 WO 2018150314A1 IB 2018050857 W IB2018050857 W IB 2018050857W WO 2018150314 A1 WO2018150314 A1 WO 2018150314A1
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WO
WIPO (PCT)
Prior art keywords
catheter
strain sensitive
force
electrical signal
sensitive element
Prior art date
Application number
PCT/IB2018/050857
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English (en)
Inventor
Troy T. Tegg
Original Assignee
St. Jude Medical International Holding S.À R.L
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by St. Jude Medical International Holding S.À R.L filed Critical St. Jude Medical International Holding S.À R.L
Publication of WO2018150314A1 publication Critical patent/WO2018150314A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6846—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive
    • A61B5/6885—Monitoring or controlling sensor contact pressure
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/12—Surgical 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
    • A61B18/14—Probes or electrodes therefor
    • A61B18/1492—Probes or electrodes therefor having a flexible, catheter-like structure, e.g. for heart ablation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6846—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive
    • A61B5/6847—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive mounted on an invasive device
    • A61B5/6852—Catheters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/14—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators
    • G01L1/142—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators using capacitors
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00315—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for treatment of particular body parts
    • A61B2018/00345—Vascular system
    • A61B2018/00351—Heart
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2018/00571—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body for achieving a particular surgical effect
    • A61B2018/00577—Ablation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/06—Measuring instruments not otherwise provided for
    • A61B2090/064—Measuring instruments not otherwise provided for for measuring force, pressure or mechanical tension
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B90/00—Instruments, implements or accessories specially adapted for surgery or diagnosis and not covered by any of the groups A61B1/00 - A61B50/00, e.g. for luxation treatment or for protecting wound edges
    • A61B90/06—Measuring instruments not otherwise provided for
    • A61B2090/064—Measuring instruments not otherwise provided for for measuring force, pressure or mechanical tension
    • A61B2090/065—Measuring instruments not otherwise provided for for measuring force, pressure or mechanical tension for measuring contact or contact pressure
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2218/00—Details of surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B2218/001—Details of surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body having means for irrigation and/or aspiration of substances to and/or from the surgical site
    • A61B2218/002—Irrigation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/021—Measuring pressure in heart or blood vessels
    • A61B5/0215—Measuring pressure in heart or blood vessels by means inserted into the body

Definitions

  • the instant disclosure relates to electrophysiology catheters with force sensors integrated near a distal tip.
  • the instant disclosure relates to
  • the human heart experiences electrical impulses traversing from the sinus node to the ventricles. Cardiac contraction is driven by a cycle of polarization and depolarization as electrical currents spread across the heart.
  • Cardiac contraction is driven by a cycle of polarization and depolarization as electrical currents spread across the heart.
  • the heart will experience an orderly progression of depolarization waves called sinus rhythm.
  • atrial arrhythmia including for example, ectopic atrial tachycardia, atrial fibrillation, and atrial flutter
  • Arrhythmias may persist as a result of scar tissue or other obstacles to rapid and uniform depolarization. These obstacles may cause depolarization waves to electrically circulate through some parts of the heart more than once.
  • Atrial arrhythmia can create a variety of dangerous conditions, including irregular heart rates, loss of synchronous atrioventricular contractions, and blood flow stasis.
  • Catheters are used in a variety of diagnostic and/or therapeutic medical procedures to diagnose and correct conditions such as atrial arrhythmia.
  • a catheter is manipulated through a patient's vasculature to the patient's heart carrying one or more electrodes which may be used for mapping, ablation, diagnosis, or other treatment.
  • the ablation catheter imparts ablative energy to cardiac tissue to create a lesion in the cardiac tissue.
  • the lesioned tissue is less capable of conducting electrical signals, thereby disrupting undesirable electrical pathways and limiting, or preventing, stray electrical signals that lead to arrhythmias.
  • the ablation catheter may utilize ablative energy including, for example, radio-frequency (RF), cryoablation, laser, chemical, and high-intensity focused ultrasound.
  • RF radio-frequency
  • cryoablation laser
  • chemical chemical
  • high-intensity focused ultrasound ablative energy
  • Ablation therapies often require precise positioning of the ablation catheter, as well as precise pressure exertion for optimal ablative-energy transfer into the targeted myocardial tissue. Excess force between the ablation catheter tip and the targeted myocardial tissue may result in excessive ablation which may permanently damage the cardiac muscle and/or surrounding nerves. When contact force between the ablation catheter tip and the targeted myocardial tissue is below a target force, the efficacy of the ablation therapy may be reduced, or entirely negated.
  • Ablation therapies are often delivered by making a number of individual ablations in a controlled fashion in order to form a lesion line.
  • Catheter localization systems, in conjunction with mapping systems, have vastly improved a clinician's ability to precisely position the ablation catheter tip for an ablation and determine the efficacy of a treatment.
  • ablation controller circuitry has improved the consistency of individual ablation therapies.
  • force sensors or load cells
  • the two basic components of a force sensor are sensing element(s) and circuitry.
  • the sensing element is often times one or more strain gauges.
  • the circuitry connects these strain gauges throughout the force sensor. While conventional force sensors are well-suited for many applications, the inability to miniaturize such force sensors has limited adoption for many applications.
  • Many surgical procedures entail introduction of a surgical instrument into the patient's anatomy.
  • a distal end of the surgical instrument is inserted into and/or through various portions of the anatomy, and in some instances purposefully brought into contact with an anatomical target site.
  • the clinician may desire to know the forces being experienced by the distal end (e.g., as the distal end is inserted into the patient, various anatomical structures may be encountered; upon contact of the distal end with an anatomical structure and with further attempts to distally maneuver the surgical instrument, resistance of the anatomical structure to further movement of the distal end creates or applies a force onto the distal end).
  • These minimally invasive and similar procedures greatly limit the sensory feedback a surgeon receives during the procedure.
  • the instant disclosure relates to an electrophysiology catheter tip including embedded force sensors (also referred to as pressure sensors).
  • the instant disclosure relates to catheters for treating cardiac arrhythmias.
  • Each of the embedded force sensors produces an output that varies based on a pressure exerted on the sensor.
  • the output of each sensor is received by a force sensor subsystem that determines a magnitude and vector of a force exerted on the catheter tip.
  • a catheter system that includes a catheter shaft with proximal and distal ends, a catheter tip coupled to the distal end of the catheter shaft, and a strain sensitive element coupled between the catheter shaft and the catheter tip.
  • the catheter tip may conduct diagnostics or therapies within a patient's vasculature.
  • the strain sensitive element deforms in response to a force exerted on the catheter tip.
  • the deformation of the strain sensitive element modulates at least one electrical characteristic of the strain sensitive element, and the change in the electrical characteristic of the strain sensitive element affects a first electrical signal transmitted by the strain sensitive element.
  • the strain sensitive element comprises a material, or composition of materials, that is resilient to stiffness degradation in response to an elevated temperature.
  • the catheter system may further include a flexible electrical circuit, where the flexible electrical circuit includes the strain sensitive element.
  • the three or more resonant circuits include a resistor, an inductor, and a capacitor in series.
  • the capacitor of each resonant circuit deforms in response to a force exerted on the catheter.
  • the deformation of each of the capacitors is associated with a magnitude of the force exerted on the catheter, and the change in the capacitance of each of the resonant circuits may be measured to determine the force exerted on the catheter.
  • the force sensor subsystem is electrically coupled to each of the three or more resonant circuits, and generates a first electrical signal that induces an oscillatory voltage in each of the three or more resonant circuits.
  • the three or more resonant circuits in response to receiving the first electrical signal, induces an oscillatory voltage that facilitates the transmission of a second electrical signal that has an induced resonant frequency associated with the deformation of the capacitor - thereby the induced resonant frequency is indicative of the force exerted on the catheter.
  • FIG. 1 is a schematic and diagrammatic view of a catheter system for performing a therapeutic medical procedure, consistent with various aspects of the present disclosure.
  • FIG. 2 is an isometric side view of a distal portion of an ablation catheter, consistent with various aspects of the present disclosure.
  • FIG. 3 is an isometric top view of a force sensor, consistent with various aspects of the present disclosure.
  • FIG. 4A is an isometric top view of a force sensor, consistent with various aspects of the present disclosure.
  • FIG. 4B is an isometric bottom view of the force sensor of FIG. 4 A, consistent with various aspects of the present disclosure.
  • FIG. 4C is an isometric top view of a printed circuit board layer of the force sensor shown in FIGs. 4A-B, consistent with various aspects of the present disclosure.
  • FIG. 4D is an isometric top view of an adhesive sheet adhered to a top surface of the printed circuit board layer of FIG. 4C, consistent with various aspects of the present disclosure.
  • FIG. 4E is an isometric cross-sectional top view (section A- A) of the force sensor of FIGs. 4A-B, consistent with various aspects of the present disclosure.
  • FIG. 4F is a cross-sectional side view (section B-B) of the force sensor of FIGs. 4A- B, consistent with various aspects of the present disclosure.
  • FIG. 5A is a top view of a force sensor probe, consistent with various aspects of the present disclosure.
  • FIG. 5B is a side view of the force sensor probe of FIG. 5 A, consistent with various aspects of the present disclosure.
  • FIG. 5C is a top view of a printed circuit board layout of the force sensor probe of FIGs. 5A-5B, consistent with various aspects of the present disclosure.
  • FIG. 6 is a simplified, cross-sectional side view of an electrophysiology catheter tip including a force sensor, consistent with various aspects of the present disclosure.
  • FIGs. 7A-7B are diagrammatic cross-sectional side views of an electrophysiology catheter tip including a force sensor, consistent with various aspects of the present disclosure.
  • FIG. 8 is a cross-sectional isometric side view of an electrophysiology catheter tip, consistent with various aspects of the present disclosure.
  • the instant disclosure relates to force sensors; in particular, some embodiments are directed to medical catheters with embedded capacitive pressure sensors.
  • electrophysiology catheters for treating cardiac arrhythmias are disclosed.
  • the embedded capacitive pressure sensors may be positioned near a distal tip of the electrophysiology catheter to detect pressure exerted through a deformable body. Controller circuitry may then determine a magnitude and vector of a force exerted upon the catheter tip using calibration algorithms and the detected pressures.
  • Various aspects of the present disclosure are directed to a force sensor for minimally invasive catheter applications.
  • the force sensors are low cost, easy to manufacture, and reduce complexity of the electrophysiology catheter assembly.
  • the force sensor includes a first sensor part (e.g., a stainless steel substrate) with a plurality of first electrode plates surrounded by an electrically non- conductive material (e.g., dielectric material/gap), with the first electrode plates being circumferentially spaced from one another about a ring-shaped substrate.
  • the sensor further includes a second sensor part with a plurality of second electrode plates (e.g., a common plate) positioned opposite the first electrode plates relative to the dielectric material/gap.
  • the second electrode plates are identical to the first electrode plates at least in terms of circumferential spacing about the ring- shaped force sensor.
  • the first sensor part is coupled to the second sensor part such that respective ones of the first electrode plates are aligned and parallel to, yet spaced from (by virtue of the dielectric gap), respective ones of the second electrode plates to establish a plurality of capacitive sensing components.
  • the first and second electrode plates may form sensing components that measure a force via capacitance, and/or one or more other electrical characteristics (e.g., resistance, inductance, etc.).
  • the second electrode plates of each of the sensing components, or the common plate are movable relative to the corresponding first electrode plate to establish a variable gap there between.
  • the sensor is ring-shaped, with the sensor defining a central bore.
  • the sensor parts are formed via one or more micro-electro-mechanical-system (“MEMS”) techniques (e.g., photo lithography, chemical processing, micro-machining/micro-fabrication, thin film deposition such as spin sputtering, and various other semiconductor fabrication techniques), with the non- conductive substrate being stainless steel.
  • MEMS micro-electro-mechanical-system
  • the system includes a sensor, an energy source, and a detector.
  • the sensor includes a housing and at least three capacitive sensing components.
  • the housing is adapted for assembly into an electrophysiology catheter, and the three capacitive sensing components are retained by the housing.
  • each of the sensing components includes first and second electrode plates arranged parallel to one another in a spaced-apart fashion to form a capacitor.
  • the housing maintains the electrode plates such that the electrode plates are movable or deflectable relative to the other/paired electrode plate in response to a force placed upon the housing, establishing a variable gap there between.
  • the energy source is electrically connected to the sensing components, as is the detector.
  • the energy source delivers energy to the sensing components, and the detector receives an output signal affected by the sensing components.
  • the output signal varies as a function of a size of the gap associated with each of the sensing components and is indicative of a magnitude and direction (vector) of a force placed upon the housing.
  • EP catheter electrophysiology catheter
  • Energy is applied to a sensor embedded within the EP catheter, with the sensor including a housing and at least three capacitive sensing components (also referred to as force sensors).
  • the EP catheter is subjected to a force of unknown magnitude and direction, with the force being transferred to the sensor housing via a deformable body.
  • the force causes a change in gap size associated with at least one of the sensing components.
  • An output signal is received from the sensor, with this output signal being affected by the sensing components.
  • the output signal from each of the sensing components is analyzed to determine a magnitude and direction of the force exerted on the catheter.
  • Fig. 1 is a schematic and diagrammatic view of an electrophysiology catheter system 100 for performing diagnostics and therapies within a cardiac muscle of a human body 140, for example, ablation therapy of tissue 120. It should be understood, however, that catheter systems consistent with aspects of the present disclosure may find application in connection with a variety of other locations within human and non-human bodies, and therefore, the present disclosure is not meant to be limited to the use of the system in connection with only cardiac tissue and/or human bodies, or in regard to ablation therapies.
  • Electrophysiology catheter system 100 may include a catheter 160, and an ablation subsystem 180 for controlling an ablation therapy conducted by an ablation catheter tip 130 at a distal end of the catheter.
  • the ablation subsystem may control the application of and/or generation of ablative energy including, for example, radio frequency (RF), cryoablation, laser, chemical, and high-intensity focused ultrasound, among others.
  • the catheter system may further include a force sensor subsystem 185 for determining and indicating to a clinician when the ablation catheter tip comes into contact with myocardial tissue within the cardiac muscle (among other impediments), and how much force is exerted upon the myocardial tissue by the ablation catheter tip.
  • the force sensor subsystem 185 receives electrical signals, from a force sensor near a distal tip 128 of the catheter 160, indicative of a force sensed.
  • Ablation therapies often require precise force exertion for optimal ablative-energy transfer into targeted myocardial tissue (e.g., in a pulmonary vein isolation procedure). Excess force between ablation catheter tip 130 and the targeted myocardial tissue may result in undue ablation - which may permanently damage the cardiac muscle and/or surrounding nerves.
  • contact force below a target force between the ablation catheter tip 130 and the targeted myocardial tissue may reduce the efficacy of the ablation therapy, as insufficient ablative energy is transferred to the myocardial tissue to cause necrosis.
  • myocardial tissue receiving the ablative therapy may regenerate and continue conducting stray electrical impulses from the pulmonary veins to the cardiac muscle leading to cardiac arrhythmias. Accordingly, it is desirable for a clinician performing the ablation procedure to receive feedback from the distal tip 128 of the catheter 160, including the force exerted by the catheter 160 on myocardial tissue being ablated.
  • catheter 160 is provided for examination, diagnosis, and/or treatment of internal body tissue such as cardiac tissue 120 (e.g., myocardial tissue).
  • the catheter may include a cable connector or interface 121, a handle 122, a shaft 124 having a proximal end 126 and a distal end 128 (as used herein, "proximal” refers to a direction toward the end of the catheter 160 near the handle 122, and “distal” refers to a direction away from the handle 122), and an ablation catheter tip 130 coupled to the distal end of the catheter shaft.
  • the handle may include inputs for a clinician to control the function of catheter tip (e.g., ablation) and/or exert steering inputs on the catheter shaft.
  • ablation catheter tip 130 may be manipulated through vasculature of a patient 140 using handle 122 to steer one or more portions of shaft 124 and position the ablation catheter tip at a desired location within heart 120.
  • the ablation catheter tip includes ablation elements (e.g., ablation electrodes, high intensity focused ultrasonic ablation elements, etc.) that when operated by ablation subsystem 180 ablates the tissue in contact with the ablation catheter tip (and in some cases tissue in proximity to the ablation catheter tip may be ablated by conductive energy transfer through the blood pool and to the proximal tissue).
  • ablation elements e.g., ablation electrodes, high intensity focused ultrasonic ablation elements, etc.
  • a force sensor near the ablation catheter tip 130 measures a force exerted on the tip 130 by tissue in contact therewith and transmits an electrical signal indicative of the sensed force to the force sensor subsystem 185.
  • the electrical signal is received by the force sensor subsystem 185 which may conduct signal processing as well as analog-to-digital conversion of the signal before associating the electrical signal with an exerted force.
  • the force sensor subsystem 185 may transmit activation signals to the force sensor (e.g., an RLC oscillator circuit within the force sensor).
  • the force sensor subsystem may further display the calculated force for the clinician or otherwise intervene during the ablation therapy where necessary to maintain the efficacy of the therapy.
  • the force sensor subsystem 185 may communicate with ablation subsystem 180 to intervene in the therapy.
  • the ablation subsystem 180 may increase the duration of the therapy or the intensity, for example.
  • the ablation subsystem 180 may decrease the duration or the intensity of the therapy, or end the therapy.
  • catheter 160 may include electrodes and one or more positioning sensors (e.g., magnetic sensors) at a distal end 128 of catheter shaft 124.
  • the electrodes may acquire electrophysiology data (also referred to as "EP data") relating to cardiac tissue within heart 120, while the positioning sensor(s) generates positioning data indicative of a 3-D position of the ablation catheter tip 130.
  • the catheter may include other conventional catheter components such as, for example and without limitation, steering wires and actuators, irrigation lumens and ports, contact sensors, temperature sensors, additional electrodes, and corresponding conductors or leads.
  • Connector 121 provides mechanical and electrical connection(s) for one or more cables 132 extending, for example, from ablation subsystem 180 to ablation catheter tip 130 mounted to a distal end 128 of catheter shaft 124.
  • the connector may also provide mechanical, electrical, and/or fluid connections for cables extending from other components in catheter system 100, such as, for example, a fluid source (when the catheter 160 includes an irrigated catheter tip).
  • a force sensor an RLC force sensor, by way of example
  • lead wires may extend from the RLC force sensor, through a length of the catheter shaft 124, to the force sensor subsystem 185.
  • Handle 122 provides a location for a clinician to operate catheter 160 and may further provide steering or guidance inputs for catheter shaft 124 while inserted within a patient's body 140.
  • the handle may include means to manipulate one or more steering wires extending through the catheter to a distal end 128 of the shaft - thereby facilitating steering the shaft.
  • the handle is conventional in the art and it will be understood that the construction of the handle may vary.
  • control of the catheter may be automated by robotically driving or controlling the catheter shaft, or driving and controlling the catheter shaft using a magnetic-based guidance system.
  • Catheter shaft 124 is an elongated, tubular, and flexible member configured for movement within a patient's body 140.
  • the shaft supports an ablation catheter tip 130 at a distal end 128 of catheter 160.
  • the shaft may also permit transport, delivery and/or removal of fluids (including irrigation fluids, cryogenic ablation fluids, and body fluids), medicines, and/or surgical tools or instruments.
  • the shaft which may be made from conventional materials used for catheters, such as polyurethane, defines one or more lumens configured to house and/or transport electrical conductors, fluids, surgical tools, and/or steering cables.
  • the catheter may be introduced into a blood vessel or other structure within the body through a conventional introducer sheath.
  • the introducer sheath is introduced through a peripheral vein (typically a femoral vein) and advanced into a right atrium of a patient's cardiac muscle 120.
  • the introducer sheath then makes an incision in the fossa ovalis (the tissue wall between the left and right atriums), and extends through the incision in the fossa ovalis to anchor the introducer sheath in the fossa ovalis - in what is referred to as a transseptal approach.
  • the ablation catheter 160 may then be extended through a lumen of the introducer sheath into the left atrium.
  • Catheter shaft 124 may then be steered or guided through the left atrium to position an ablation catheter tip 130 into a desired location within the left atrium such as in proximity to a pulmonary vein where an ablation therapy is to be applied.
  • a force sensor coupled near a distal portion 128 of the catheter shaft 124 may transmit signals to force sensor subsystem 185 indicative of a force exerted on the ablation catheter 160 by myocardial tissue in proximity to one or more of the pulmonary veins. Accordingly, the clinician may adjust the force exerted to best suit a particular ablation therapy.
  • aspects of the present disclosure improve the efficacy of ablation therapy by more effectively maintaining a consistent force between ablation catheter tip 130 and myocardial tissue being ablated during a single-point ablation, as well as along a lesion line comprising a number of individual ablations.
  • a force sensing schema as disclosed herein, may also be readily implemented in ablation balloon catheters.
  • a force sensor consistent with the present disclosure, reduces the complexity of the catheter assembly, and associated cost.
  • a force sensor subsystem 185 receives signals from a force sensor coupled to the catheter shaft 124 near a distal end 128 of the catheter 160, which is located within a cardiac muscle 120 of a patient 140.
  • the force sensor subsystem 185 may transmit activation signals to the force sensor (e.g., an embedded RLC oscillator).
  • the distal end 128 of the catheter 160 is positioned within the cardiac muscle 120 to conduct an ablation therapy.
  • Ablation therapies are commonly used to necrose myocardial tissue in a cardiac muscle, which may alleviate symptoms associated with epicardial ventricular tachycardia, atrial fibrillation, and other cardiac arrhythmia conditions.
  • One source of such electrical impulses is from arrhythmiatic foci located in the pulmonary veins.
  • myocardial tissue in a cardiac muscle forms a conductive pathway for electrical signals traveling through pulmonary venous tissue.
  • the electrical signals from the pulmonary veins disrupt the electrical signals that trigger the orderly pumping motion of the cardiac muscle 120, resulting in an irregular, and often rapid heart rate that commonly causes poor blood flow.
  • the ablation therapy electrically isolates the sources of such unwanted electrical impulses from the cardiac muscle 120 by effecting necrosis of myocardial tissue between the pulmonary veins and the right atrium.
  • the necrosed myocardial tissue (scar tissue) exhibits increased resistance to the electrical impulses, isolating the cardiac muscle from the stray electrical signals, and relieving symptoms relating to atrial fibrillation.
  • a force sensor subsystem may include both a transmitter for activating the force sensor, and a receiver to capture the subsequent resonant signal(s) transmitted by the RLC circuit in response.
  • the RLC circuit in response to a force that changes the dielectric gap between the conductive plates of the capacitor, modulates one or more electrical characteristics of the received signal from the force sensor subsystem and transmits the modulated signal back to the force sensor subsystem.
  • the modulated return signal is therefore indicative of the force exerted on the catheter tip.
  • the RLC circuit may further indicate various other aspects about the applied force/strain on the catheter tip based upon, for example, peak frequency, bandwidth, and characteristic dissipation times of the return signal from the force sensor.
  • the force sensor subsystem may also utilize a Sll measurement method, CardioMEMS method (see, e.g., U.S. Patent No. 7,245,117, which is hereby incorporated by reference as though fully set forth herein), or a more basic communication method (e.g., ping and listen).
  • a Sll measurement method e.g., CardioMEMS method
  • CardioMEMS method see, e.g., U.S. Patent No. 7,245,117, which is hereby incorporated by reference as though fully set forth herein
  • a more basic communication method e.g., ping and listen
  • a flexible structure may be attached to the ablation tip such that a significant amount of the catheter tip applied load is transferred from the ablation tip 130 to the flexible structure (and not transferred down a non-conforming portion of the catheter shaft).
  • a force sensor coupled between the flexible shaft portion and the non- conforming portion of the shaft may then receive a majority, if not all, of the force exerted on the catheter tip.
  • FIG. 2 is an isometric side view of a distal portion 205 of an ablation catheter 200, consistent with various aspects of the present disclosure.
  • Catheter 200 may include an RF electrode within the distal portion 205 for ablating tissue in contact therewith.
  • the RF electrode can be powered by a signal generator near a proximal end of the catheter 200 that is
  • an irrigant lumen may deliver irrigant fluid to a distal tip 205.
  • the irrigant fluid may also facilitate cooling of the distal tip 205 during ablation therapy, which may prevent blood charring onto an exterior surface of the distal tip 205.
  • distal tip 205 When distal tip 205 is placed into contact with tissue in preparation for conducting an ablation therapy, a force is exerted upon the tissue. In ablation therapy applications, the force exerted by the distal tip 205 of catheter 200 is directly associated with a therapy outcome. For example, a force above or below a threshold force may result in an undesirable therapy outcome - such as over-ablation, or failure to necrose the tissue.
  • a force sensor 215 for sensing a force exerted by, or on, a distal tip 205 of catheter 200.
  • a deformable body 220 within the distal tip 205 may be compressed and/or deflected relative to a longitudinal axis of the catheter in response to a force exerted on the distal tip 205 by tissue in contact therewith.
  • the deformable body 220 facilitates relative movement of the distal tip 205 without affecting the rest of the catheter shaft.
  • a force transmitter 210 within the distal tip 205 translates the exerted force on the tip to the force sensor 215.
  • the deflection of the tip 205 is associated with a force exerted on the tip, by way of the known spring constant of deformable body 220 (e.g., via calibration of the force transmitter 210 and force sensor 215).
  • the force sensor 215 transmits electrical signals, to a force sensor subsystem at a proximal end of the catheter 200, indicative of a magnitude and direction of the force exerted on the catheter tip 205.
  • a force sensor 215 is configured for use within a non-invasive cardiac catheter device 200.
  • the force sensor 215 may consist of one or more pressure or force sensitive capacitive elements 210 which reside within a resonant LC Circuit (such a combination of circuitry also referred to herein as a CardioMEMS sensor, or RLC circuit).
  • the LC resonance may be measured remotely using a force sensor subsystem - which uses a communications protocol between the LC resonance circuit and the force sensor subsystem.
  • the capacitive element may be used to measure intravascular blood pressure.
  • the capacitive element may be used to measure catheter tip contact force in a cardiac ablation catheter.
  • the force sensor may include three or more RLC circuits facilitating determination of both magnitude, and the directionality of the force applied on the catheter tip 205.
  • force sensors including stress/strain type load cells on a flexible shaft, are disclosed. Force sensors fall into three categories: piezo-resistive, piezo-electric and capacitive. While aspects of the present disclosure may be amenable to any of the three types of force sensors - many of the embodiments disclosed herein are presented with capacitive RLC force sensors. However, use of the various other types of force sensors are readily envisioned in the embodiments disclosed herein.
  • force sensor 215 may include three or more strain sensitive resistive, capacitive, or inductive elements coupled between a conforming and non-conforming portion of the catheter shaft adjacent to the catheter tip.
  • the strain sensitive elements are electrically coupled to an induction coil to form an RLC-type force sensor circuit.
  • the conforming portion of the catheter shaft which may extend distal force sensor 215, deflects in response to a force exerted on the distal tip 205 of the catheter. Force applied to the catheter tip 205 and translated through the force transmitter 210 generates a strain across the strain sensitive elements of the force sensor 215, resulting in a change of capacitance, resistance, or inductance.
  • This change in capacitance, resistance, or inductance is sensed by driving the force sensor with a current and measuring the emitted resonant frequency response of the activated RLC circuit.
  • a known calibration relates an applied tip force (and direction) to the resulting transmitted frequency response from each of the RLC circuits within the force sensor 215.
  • an activation signal transmitted by a force sensor subsystem may be in proximity to the resonant frequency of an RLC circuit of the force sensor to induce an oscillatory voltage.
  • the frequency, bandwidth, and attenuation of the subsequent induced resonant frequency may depend on the values of one or more of the capacitance, resistance, or inductive of the strain sensitive element within the force sensor. For example, a decrease in capacitance will result in an increase in the LC resonant frequency. Alternately, a change in resistance is expected to result in a change of fractional bandwidth or quality factor - resulting in an output signal of the RLC circuit associated with an applied tip force.
  • FIG. 3 is an isometric top view of a force sensor 324, consistent with various aspects of the present disclosure.
  • more than one force sensing element 342 can be printed around the circumference of the force sensor 324.
  • Such an implementation may be advantageous for determining the directionality of the applied force on the distal tip.
  • the multiple force sensing elements 342 may be used for improved signal stability.
  • the multiple force sensing elements 342 may comprise orthogonal capacitive or piezo-resistive strain sensitive elements for compensating for temperature variations during use. In such multiple force sensing element embodiments, both axial and non-axial forces exerted on the distal tip of the catheter may be sensed.
  • the force sensor 324 includes a housing 340 and three force sensing elements 342 - with paired capacitive sensing components (e.g., conductive plates spaced apart by a dielectric gap/flexible material).
  • a top plate of the pair also referred to as capacitive sensing components 300, are shown in FIG. 3.
  • the capacitive sensing components 300 are maintained within the housing 340, and thus are generally referenced in the view of FIG. 3.
  • the force sensor 324 can assume a variety of shapes and/or sizes differing from those implicated by the illustrations of FIGS. 2-7B.
  • the housing 340 is generally comprised of a non- conductive material into which the capacitive sensing components 300, as well as other components as described below, are embedded or otherwise maintained.
  • the housing is comprised of a stainless steel alloy.
  • the housing 340 exhibits at least a small degree of elastic or substantially elastic flexibility so as to permit alteration of an arrangement of each of the capacitive sensing components 300 in response to expected forces imparted upon the sensor 324 as described below.
  • the housing structure 340 can be formed from a variety of materials.
  • the material(s) selected for the housing structure 340 is conducive to MEMS construction (e.g., amenable to receiving sputter deposited metals).
  • the housing structure 340 can be constructed of silicon.
  • the material of the housing structure 324 can alternatively be a polymer or polymeric resin exhibiting biologically inert characteristics.
  • the material of the housing structure 340 can be a photosensitive or general thermoplastic resin, such as a negative, epoxy-type, near-UV photoresist material available under the trade designation SU-8 from Shell Chemical. Other materials are also acceptable.
  • the housing structure 340 should be elastically deformable (or substantially elastically deformable) in the presence of forces expected to be encountered during use.
  • the material selected for the housing structure 340 in conjunction with the corresponding dimensions must permit inward deflection of an upper portion of the housing relative to a lower portion of the housing in response to an externally applied force, and return to the natural state of FIG. 3 upon removal of the force.
  • the housing structure 340 may be comprised of a metal alloy (such as a stainless steel alloy) to mitigate stiffness degradation associated with material fatigue during use.
  • the force sensor 324 includes six of the capacitive sensing components 300 (in paired configurations).
  • the capacitive sensing components 300 are isolated from one another, via a dielectric gap, with the cross-sectional view of FIGs. 4E and 4F illustrating one of the sensing components 300. While FIG. 3 has been described as generally reflecting provisioning for three force sensing elements 342, in other embodiments, four or more force sensing elements 342 may be fitted within the housing 340. Regardless of the number of force sensing elements 342 provided, the capacitive sensing components 300 may be identical for each force sensing element 342, and include a first electrode plate and a second electrode plate vertically oriented one above the other.
  • FIGs. 4A and 4B are isometric top and bottom views, respectively, of a force sensor 400, consistent with various aspects of the present disclosure.
  • the force sensor 400 includes a ring-shaped, stainless steel substrate 410 upon which a dielectric layer 415 is deposited.
  • Three capacitive sensing elements are circumferentially distributed about the force sensor 400.
  • the capacitive sensing elements each include a copper bottom plate coupled to the dielectric layer 415.
  • An adhesive layer 430 is deposited between the dielectric layer 415 and a common plate 405, which facilitates an air gap between each of the common plate 405 and the corresponding copper bottom plate of the capacitive sensing elements.
  • the air gap between each of the plates of the capacitive sensing elements and the common plate 405 functions as a dielectric layer.
  • the force sensor 400 may be embedded within a cardiac catheter and
  • a clinician may activate the force sensor subsystem which transmits an activation signal to induce resonance within an RLC circuit including the force sensor 400.
  • the capacitive sensing element(s) Based on the strain induced on the force sensor by a force translated to the force sensor from the catheter tip, the capacitive sensing element(s) transmits a response based on the sensed strain.
  • the sensor may also include transmission elements that facilitate the transmission of a strain dependent emission signal back to the force sensor subsystem.
  • the force sensor subsystem may associate the strain dependent emission signal with a calibrated, or otherwise associated, force exerted upon a distal tip of the catheter. Based on the signals received by the force sensor subsystem from three or more capacitive sensing elements, a magnitude and vector of the force exerted on the catheter tip may be determined.
  • a non-conforming, proximal, portion of a catheter shaft is coupled to a stainless steel substrate 410 of the force sensor 400.
  • a conforming, distal, portion of the catheter shaft is coupled to common plate 405.
  • the force is translated through the conforming portion of the catheter shaft, and into contact with the common plate 405 of each of the capacitive sensing elements.
  • the deflection of the common plate in proximity to a corresponding opposite pole is indicative as to both a magnitude of the force, and whether the force placed on each of the individual strain sensitive elements are tension or compression.
  • the opposite pole may be a copper sensor.
  • the deflection of the common plate relative to one of the copper sensors results in a change in the capacitance (resistance, or inductance of the strain sensitive element). This change in capacitance (resistance, or inductance) induces a resonant frequency response in the resulting strain dependent emission signal.
  • circuitry within the subsystem associates each of the signals with a force, and the cumulative magnitude and vector of the force exerted on the catheter tip may be determined.
  • the association between the output signal(s) from each of the capacitive sensing elements and the force exerted on the distal tip of the catheter may be based on, for example, a look-up table, formula, or other calibration means.
  • a dielectric medium of a capacitive strain sensitive element 342 may include any material which is not electrically conducting.
  • a dielectric medium of the capacitive strain sensitive element 342 may include very high permittivity materials and which will deform under an applied load associated with a specific application (e.g., ablation therapy).
  • various embodiments of the present disclosure are directed to strain sensitive elements 342 that are capable of operating in elevated temperature environments (e.g., greater than 80 degrees Celsius), while maintaining their mechanical characteristics - particularly, stiffness. Where the mechanical characteristics of the strain sensitive element 342 is subject to stiffness degradation over a useable temperature range, the precision of the force sensor may be reduced.
  • the strain sensitive components such as substrate 410 and common plate 405 (as shown in FIGs. 4A and 4B), include a stainless steel alloy which does not suffer from stiffness degradation within a useable range of an ablation catheter (e.g., between 0-105° Celsius), for example.
  • Graph 1 shows a digital output (y-axis) of a strain sensitive element over a period of time (x-axis, units: 1/16 seconds). The strain sensitive element initially experiences no force, followed by a 40 gram force for 10 seconds, and then removal of the force. Graph 1 shows the resulting digital output when the strain sensitive element is operating at 25° Celsius. Repeating the test with strain sensitive element operating temperatures of 45° Celsius and 65° Celsius, the strain sensitive element produces substantially the same digital output. In all three tests the digital output essentially returns to a base-line (zero) after the force applied to the strain sensitive element is removed.
  • Graph 2 shows a digital output (y-axis) of a strain sensitive element over a period of time (x-axis, units: 1/16 seconds). The strain sensitive element initially experiences no force, followed by a 40 gram force for 10 seconds, and then removal of the force. Graph 2 shows the resulting digital output when the strain sensitive element is operating at 85° Celsius. In the present test, the digital output never returns to its base-line output after the force has been removed from the sensor. Any force readings conducted thereafter will have a large error (e.g., up to 50%, or more).
  • the strain sensitive elements tested in Graphs 1 and 2 have a common plate and a substrate comprised of a polymer.
  • the common plate deflects in response to the force exerted on a catheter tip.
  • many polymers begin to experience mechanical break-down as they approach temperatures of 100° Celsius. Accordingly, the stiffness of the common plate may be negatively impacted, and may even be permanently degraded (e.g., due to material fatigue). With the common plate being unable to return to an initial at-rest position, the strain sensitive element will fall out of calibration - rendering a known association between a digital output of the strain sensitive element and an exerted force inaccurate.
  • aspects of the present disclosure are directed toward implementing metal alloys, such as stainless steel, for the common plate and the substrate to produce a strain sensitive element that is not susceptible to stiffness degradation over the temperature range associated with tissue ablation.
  • FIG. 4C is an isometric top view of a printed circuit board layer 401 (also referred to as PCB layer) which is printed on a polymer substrate 415 of force sensor 400 (shown in FIGs. 4A-B), consistent with various aspects of the present disclosure.
  • the PCB layer 401 includes three copper sensors 420 A , 420 B , 420c (also referred to as opposite poles) circumferentially distributed thereon.
  • the copper sensors 420A, 420B, 420C may be gold plated to prevent corrosion.
  • Each of the copper sensors 420A, 420B, 420c are communicatively coupled to a common power source via an electrical trace (e.g., 421).
  • each of the strain sensitive elements deforms at least one of substrate 410 and/or common plate 405, thereby changing the electrical capacitance of the resulting signal output from the strain sensitive element.
  • Separate electrical traces 421 from each of the strain sensitive elements may transport the resulting signal output to a force sensor subsystem.
  • FIG. 4D is an isometric top view of an adhesive sheet 430 adhered to a top surface of PCB layer 401 of FIG. 4C, consistent with various aspects of the present disclosure.
  • the adhesive sheet 430 has cut-outs above each of the copper sensors 420A, 420B, 420C to facilitate a dielectric gap (air/vacuum) between the copper sensors 420A, 420B, 420C and common plate 405.
  • the adhesive sheet 430 is comprised of a dielectric material.
  • FIG. 4E is an isometric cross-sectional top view (section A- A) of the assembled force sensor 400 of FIGs. 4A-B.
  • Common plate 405 and substrate 410 sandwich together polymer substrate 415 (with the three copper sensors 420A, 420B, 420C and traces 421 coupled to a surface thereof) and adhesive sheet 430.
  • the adhesive sheet 430 adheres all the components of force sensor 400 together.
  • FIG. 4F is a partial cross-sectional side view (section B-B) of the force sensor 400 of FIGs. 4A-B, showing a close-up of one of the strain sensitive elements.
  • the common plate 405 deflects relative to substrate 410.
  • the deflection of the common plate 405 changes the dimensional characteristics of the strain sensitive element. Specifically, the distance between the common plate and copper sensor 420A is decreased under compression, or increased under tension. Due to the resulting change in relative dielectric gap 425, the capacitance between the common plate 405 and copper sensor 420A changes. Traces 421 feed a common electrical signal to the common plate 405 of each of the strain sensitive elements.
  • Other traces 421 may deliver a modified signal (due to the relative capacitance of the strain sensitive element) from each of the strain sensitive elements back to a force sensor subsystem.
  • the force sensor subsystem may associate the modified output signal to an exerted force on the individual strain sensitive element. Once the magnitude and direction (compression/tension) of the force exerted on each strain sensitive element is determined, a magnitude and direction of the force exerted on the catheter tip may be determined.
  • Some embodiments may utilize a stainless steel alloy, or other materials (or compositions of materials) which maintain mechanical characteristics (including stiffness) at high temperatures for common plate 405 and/or substrate 410. In various embodiments, due to the stiffness of a stainless steel common plate 405, the strain sensitive element is relatively insensitive to vacuum or atmospheric pressure differences in the dielectric gap region 425.
  • the determined force exerted on a distal tip of the catheter may be communicated to the clinician.
  • the force exerted on the catheter may be visually indicated on a dial, gauge, display, a varying audible tone, or tactile feedback - such as a vibration in the handle, among other well-known sensory communication techniques.
  • FIG. 5A is a top view of a force sensor probe 500, consistent with various aspects of the present disclosure.
  • Strain sensitive elements 555 A- c located on a distal tip 551 of the probe 500, are electrically coupled to solder pads 554A-D on a proximal end 553 of the probe 500 via electrical traces the extend a length of shaft 552.
  • the length of the probe 500 is approximately 2.5 inches in length, with the entire probe located within a distal portion of a catheter.
  • Four leads are soldered on to solder pads 554A-D and extend the length of the catheter shaft.
  • the force sensor probe 500 includes analog-to-digital circuitry and/or signal condition circuitry. By positioning such circuitry near the strain sensitive elements 555 A- c, the signal-to-noise ratio of the signals received by the force sensor subsystem may be greatly reduced. This is because digital signals are less susceptible to the magnetic and electrical noise which is picked-up by the extended electrical leads extending through the catheter shaft.
  • FIG. 5B is a side view of force sensor probe 500 of FIG. 5 A, consistent with various aspects of the present disclosure.
  • Distal tip 551 of the force sensor probe 500 is built on a stainless steel substrate 510.
  • a polymer substrate 515, adhesive sheet 521 and common plate 505 are respectively stacked upon the stainless steel substrate 510.
  • the length of shaft 552 and proximal end 553 are built upon the polymer substrate 515 alone. Accordingly, the length of shaft 552 and the proximal end 553 are flexible (e.g., flex circuitry), facilitating installation of the force sensor probe 500 into a catheter tip assembly.
  • Fig 5B shows some example layer thicknesses for a specific
  • the stainless steel substrate 510 being approximately 0.0020" thick
  • the polymer substrate 515 being approximately 0.0004" thick
  • the adhesive sheet 521 being approximately 0.0009" thick
  • the common plate 505 being approximately 0.0004" thick.
  • FIG. 5C is a top view of the printed circuit board layout of the force sensor probe 500 of FIGs. 5A-5B. Copper sensors 520 A- c on a distal portion 551 of the force sensor probe are electrically coupled to traces 521A-D- The traces 521A-D electrically couple the copper sensors 520A-C to solder pads 554A-D at a proximal end 553 of the force sensor probe via a shaft 552 there between. A first solder pad 554A may receive a common input signal from a lead wire soldered thereto.
  • the common input signal may then be transmitted from the first solder pad 554A, through a series of electrical traces 521 A to each of the copper sensors 520 A- c- Based on the deflection of the common plate relative to each of the copper sensors 520 A- c, the strain sensitive elements modulate the received signal based on a change in the resistance, impedance, and/or capacitance associated with the change in distance between the common plate and the copper sensors.
  • the adjusted signals from each of the strain sensitive elements are then transmitted via independent traces 521B-D to solder pads 554B-D, and through individual leads to a force sensor subsystem for signal filtering and analysis.
  • a single trace, solder pad, and lead wire may be used to transmit all three of the adjusted signals from the three strain sensitive elements.
  • Such specific embodiments may utilize frequency modulation, time modulation, or other signal transmission methods that facilitate transmission of multiple signals simultaneously, while facilitating individual analysis of each signal at an end point (e.g., force sensor subsystem).
  • FIG. 6 is a simplified, cross-sectional side view of a force sensing electrophysiology catheter tip 20' including a force sensor 24' , consistent with various aspects of the present disclosure.
  • the present embodiment by virtue of having a varying inductor coupled to each of the outputs from the strain sensitive element (facilitating frequency modulation of each of the outputs of the three strain sensitive elements into a single line) requires only a single output wire.
  • three output wires, one for each strain sensitive element 42a' may be used - with no frequency or time modulation utilized.
  • the force sensor 24' either uses discrete lead wires for each strain sensitive element 42a' , or the inductors are located out of view (proximal the force sensor 24' ). With such a construction, three or more wires may be required to transmit the adjusted signals from each of the strain sensitive elements 42a' within the force sensor 24' .
  • the force sensor 24' includes individual strain sensitive elements 42a' assembled to the catheter tip 22'.
  • the force sensor 24' includes a housing 40' and three or more capacitive sensing components 42a' and 42b' (two of which are illustrated in FIG. 6).
  • a first wire 270 electrically connects the common electrode 90 of the force sensor 24' with an energy source.
  • a separate wire 272' is provided for each of the capacitive sensing components 42' (e.g., wire 272a' is electrically connected to the first capacitive sensing component 42a' and wire 272b' is electrically connected to the second capacitive sensing component 42b').
  • the capacitor wires 272' extend from the catheter tip 22' and are electrically connected to a respective one of the inductors (not shown) otherwise provided apart from the force sensor 24' .
  • the inductors are, in turn, electrically connected to a detector (also referred to as a force sensor subsystem), with signals from the inductors combining to provide the output signal analyzed by the detector.
  • the system 20' operates in a manner similar to those described above, with the capacitance associated with one or more of the capacitive components 42' changing in response to a force applied to the catheter tip 22', and thus to the housing 40'. That is to say, a size of the gap 84' defined between electrode plates 80', 82' of one or more of the capacitive sensing components 42' changes in response to the force F; this change is size alters the impedance value associated with the corresponding LC circuit. This alteration is indicative of a magnitude of the applied force F, and the changes in each of the capacitive sensing component outputs collectively indicate a direction of the force F. Based upon these same principles, in other embodiments, the inductors can be omitted.
  • the force detection systems and methods of the present disclosure provide a marked improvement over previous designs.
  • the sensors are highly amenable to small scale applications (e.g., on the order of 5 mm or less), and can be employed with surgical instrumentation (e.g., catheters). Further, testing has confirmed that even at small scale constructions (e.g., on the order of 5 mm or less), the sensors of the present disclosure generate reliable force-related results at temperatures exceeding 65° C, and can withstand and continue to generate reliable results (e.g., sensing forces in the range of 1-200 grams) after experiencing shock forces on the order of 200 grams. Further, the sensors can be fabricated on a mass-production (and thus low cost) basis utilizing MEMS technology, with multiple flexible, tri-axes force sensors being generated on a single silicon wafer.
  • FIGs. 7A-7B are diagrammatic cross-sectional side views of a distal portion of an electrophysiology catheter 700 including a force sensor 710, consistent with various aspects of the present disclosure.
  • the force sensor 710 is coupled between catheter tip 705 and catheter shaft 760.
  • a force exerted on the catheter tip 705 is transposed through three force transmitters 711A-C that impress the force onto a top surface of a strain sensitive element.
  • force sensor 715 includes three strain sensitive elements that interface with the force transmitters 711A-C-
  • Fig. 7B shows an example force 712A exerted on catheter tip 705 of an
  • the example force 712A includes forces in both longitudinal and radial vectors relative to a length of catheter shaft 760.
  • Deformable body 720 facilitates the misalignment of the catheter tip 720 relative to the catheter shaft 760 in response to the example force 712A.
  • a compressional force component 712c is transported through force transmitter 711 A to a surface of a first strain sensitive element of force sensor 715.
  • the force transmitter 711A presses downward on a common plate of the first strain sensitive element changing the dielectric air/vacuum gap between the common plate and a copper sensor of the first strain sensitive element.
  • force transmitter 711 B transmits a small compressional force component 712 D to a second strain sensitive element of the force sensor 715 - the small decrease in the dielectric gap between the common plate and the copper sensor slightly alters the impedance value associated with the corresponding LC circuit of the second strain sensitive element.
  • a force transmitter 711c nearest the surface where the force 712A is exerted on the catheter tip 705 is placed into tension in response to a tension force component 712B of the force 712A.
  • force transmitter 71 lc pulls up on a common plate of a third strain sensitive element - increasing the dielectric gap between the common plate and the copper sensor thereby altering the impedance value associated with the corresponding LC circuit of the third strain sensitive element (the change being of an opposite magnitude to those of the first and second strain resistive elements).
  • the resulting impedance values of all of the strain sensitive elements are collectively indicative of a magnitude and direction of the force 712A.
  • FIG. 8 is a cross-sectional isometric side view of an electrophysiology catheter tip 800, consistent with various aspects of the present disclosure.
  • the electrophysiology catheter tip 800 is an ablation catheter including an ablation tip 805 with an irrigation passage 820 extending co-axially along a longitudinal axis 801 of the catheter 800.
  • the ablation tip 805 is coupled to a shaft coupler 810, and thereby the catheter shaft (not shown), via a force sensor housing 827.
  • the force sensor housing 827 includes a bottom portion 825 and a top cover 830.
  • the force sensor housing 827 is a metallic structure.
  • the force sensor housing 827 houses a force sensor (not shown) consistent with the various embodiments disclosed herein.
  • the force sensor is mounted within the force sensor housing 827 at mounting surfaces 826 and 831.
  • the force sensor housing 827 may be hermetically sealed at the junction between the bottom portion 825 and the top cover 830 via a laser weld, or other well-known hermetic sealing methodologies (e.g., adhesive, ultrasonic welding, fasteners and gaskets, etc.).
  • the force sensor housing 827 is coupled to the shaft coupler 810, for example, via a laser weld that provides a hermetical seal therebetween.
  • the top cover 830 and the shaft coupler 810 coupled thereto is coupled to the ablation tip 805 via a number or welding protrusions 832 on a top surface of the top cover 826 and circumferentially distributed about the longitudinal axis 801.
  • the welding protrusions 832 are mated with a proximal surface of the ablation tip 805 and coupled, for example, using spot welds.
  • the top cover 830 may first be coupled to the ablation tip 805 via one or more welds. Then the bottom portion 825 of the force sensor housing 827 (with a force sensor mounted therein) may be laser welded, for example, to the top cover 830. Finally, the shaft coupler 810 may be coupled to a proximal portion of the bottom portion 825 of the force sensor housing 827 to complete the electrophysiology catheter tip assembly 800.
  • Welding protrusions 832 in FIG. 8, may also be positioned directly over each force sensor element of the force sensor to facilitate the translation of forces from the ablation tip 805 to the force sensing elements within the force sensor housing 827.
  • An opening along a longitudinal axis 801 and through the force sensor housing 827 and force sensor itself facilitates an irrigation lumen 815 to fluidly couple the irrigation passage 820 within the ablation tip 805 to an irrigation passage within the shaft coupler 810 and the catheter shaft.
  • Various embodiments of the present disclosure are directed to force sensors with dedicated lead wires to output the signals from each strain sensitive element within the force sensor.
  • embodiments consistent with the present disclosure may also readily utilize a two-lead approach. Such embodiments may rely on frequency modulation to transmit signals from two or more strain sensitive elements to a force sensor subsystem.
  • the force sensor subsystem including an impedance meter, interprets the amplitudes of each of the strain sensitive elements to determine the amplitude and the direction of the force applied on the catheter tip.
  • each of the output signals from the strain sensitive elements are coupled to an inductor.
  • Each inductor has a different micro-Henry value, which excites the output signal from that particular strain sensitive element at a desired frequency.
  • each of the strain sensitive elements may be electrically coupled to a 1 , 2, and 5 micro-Henry inductor, respectively.
  • Each of the inductors exciting the impedance values at approximately, 30, 60, and 90 MHz, respectively.
  • the capacitance of each of the strain sensitive elements, at rest is 5 picofarads
  • the output signals from each inductor may then be merged onto a single lead wire and delivered to a force sensor subsystem. Signal analysis at the force sensor subsystem may then be used to unpack each of the impedance values associated with the strain sensitive elements.
  • Graph 3 as shown below, exemplifies how back-end signal analysis may be used to unpack each of the individual impedance signals from the merged signal.
  • Graph 3 shows an image from an oscilloscope charting the Voltage (y-axis) compared to the frequency in Hz (y-axis) of the merged signal of the three strain sensitive elements. The amplitudes of each of the valleys are associated with the force exerted on each of the strain sensitive elements.
  • a common plate of each of three strain sensitive elements are electrically coupled to a force sensor subsystem (which may include a frequency generator) operating at 1 V/l OOMHz via a 20 Ohm resistor.
  • the common plates of each of the strain sensitive elements are also electrically coupled to a force sensor subsystem to interpret the resulting frequency modulated signal and determines a magnitude and vector of a cumulative force exerted on the force sensor.
  • Opposite the common plates of each of the strain sensitive elements are copper sensors electrically coupled to a ground via an inductor.
  • Each of the inductors may have varying inductance (e.g., 1, 2, and 5 micro-Henry) to facilitate excitation of the capacitance of each of the strain sensitive elements at varying frequencies (see, e.g., Graph 3, above).
  • the force sensor may be configured for use within an intravascular blood pressure (IVP) catheter, an introducer sheath (such as an AgilisTM introducer sheath, produced by St. Jude Medical, Inc.) to eliminate the need for an IVP catheter entirely, among other minimally invasive catheter applications.
  • IVP intravascular blood pressure
  • an introducer sheath such as an AgilisTM introducer sheath, produced by St. Jude Medical, Inc.
  • a force sensor consistent with the present disclosure may include powered and/or un-powered (e.g., active and passive, respectively) circuitry.
  • powered and/or un-powered circuitry e.g., active and passive, respectively.
  • force sensor circuitry is passive and merely modulates a received frequency from a force sensor subsystem.
  • the force sensor circuitry may be an active system with a power source (e.g., capacitor) that facilitates regular wake-ups of an integrated circuit to measure a strain on a strain sensitive element, and to transmit signals to the force sensor subsystem indicative of the strain.
  • the force sensor circuitry may receive a (ultra-high frequency) power signal from the force sensor subsystem that facilitates charging of the power source to maintain operation of the force sensor.
  • the deformation of the strain sensitive element may modulate the resulting signal transmission, or transmit a digital signal based on the modulation of a signal through the strain sensitive element.
  • the force sensor circuitry at a distal end of a catheter shaft may be electrically coupled with a power source at a proximal end of the catheter shaft to provide continuous power to the force sensor circuitry, while mitigating the need for power supply storage and other driver circuitry at the distal tip of the catheter shaft.
  • electrical signals indicative of the strain on the strain sensitive element may still be communicated with the force sensor subsystem.
  • embodiments means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment.
  • appearances of the phrases “in various embodiments,” “in some embodiments,” “in one embodiment,” “in an embodiment,” or the like, in places throughout the specification are not necessarily all referring to the same embodiment.
  • the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
  • the particular features, structures, or characteristics illustrated or described in connection with one embodiment may be combined, in whole or in part, with the features structures, or characteristics of one or more other embodiments without limitation.
  • proximal and distal may be used throughout the specification with reference to a clinician manipulating one end of an instrument used to treat a patient.
  • proximal refers to the portion of the instrument closest to the clinician and the term “distal” refers to the portion located furthest from the clinician.
  • distal refers to the portion located furthest from the clinician.
  • spatial terms such as “vertical,” “horizontal,” “up,” and “down” may be used herein with respect to the illustrated embodiments.
  • surgical instruments may be used in many orientations and positions, and these terms are not intended to be limiting and absolute.

Abstract

Certains aspects de la présente invention, concernent un système de cathéter électrophysiologique permettant de réaliser des diagnostics et des traitements dans un système cardiovasculaire ; plus particulièrement, l'invention concerne un capteur de force intégré à un cathéter qui détecte une force exercée sur un bout distal du cathéter et transmet un signal indiquant l'amplitude et la direction détectées de la force à un sous-système de capteur de force.
PCT/IB2018/050857 2017-02-15 2018-02-12 Capteur de force pour bout distal de cathéter WO2018150314A1 (fr)

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WO2020154592A1 (fr) * 2019-01-24 2020-07-30 Icahn School Of Medicine At Mount Sinai Dispositif de mesure de coaptation et ses procédés d'utilisation
EP3705030A1 (fr) * 2019-03-04 2020-09-09 Silicon Microstructures, Inc. Détection de force de contact 3d
US10806428B2 (en) 2015-02-12 2020-10-20 Foundry Innovation & Research 1, Ltd. Implantable devices and related methods for heart failure monitoring
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US10905393B2 (en) 2015-02-12 2021-02-02 Foundry Innovation & Research 1, Ltd. Implantable devices and related methods for heart failure monitoring
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