WO2022187096A1

WO2022187096A1 - Catheter for ablating tissue within a human or animal body

Info

Publication number: WO2022187096A1
Application number: PCT/US2022/017917
Authority: WO
Inventors: Alan De La Rama; Cary Hata
Original assignee: CRC EP, Inc.
Priority date: 2021-03-01
Filing date: 2022-02-25
Publication date: 2022-09-09

Abstract

The present invention relates to a catheter for ablating tissue within a human or animal body, comprising an elongated catheter shaft (2) extending along a catheter axis (A) and an irrigation liquid space (13) arranged inside the catheter shaft (2), wherein a distal end portion of the catheter shaft (2) is configured as a tip electrode (3). The tip electrode (3) comprises at least in a section shaped as a first helix (5) around the catheter axis (A), the tip electrode (3)) being configured to deliver energy to the tissue to be ablated and having a plurality of first windings (4) and at least one first vent (6) between two axially adjacent first windings (4) in each case, wherein the at least one first vent (6) enables a flow connection between the irrigation liquid space (13) and an outside of the catheter (1), wherein at least one first distance element (7) is arranged between two axially adjacent first windings (4), the at least one first distance element (7) preventing a complete closure of the at least one first vent (6).

Description

CATHETER FOR ABLATING TISSUE WITHIN A HUMAN OR ANIMAL BODY

Description

The present invention relates to a catheter for ablating tissue within a human or animal body according to the preamble of claim 1.

During electrophysiology mapping and ablation procedures, a physician maneuvers the tip of an ablation catheter through various tissue surfaces. Some cardiac tissues have a smooth surface while other areas have ridges, valleys, and acute contours, as well as trabeculations. With a typical solid tip ablation electrode, it may sometimes be challenging to achieve adequate tissue contact due to the varying anatomic topography. Consistent tissue contact is one of the most important factors for the creation of effective lesions during radiofrequency (RF) ablation. Recently, a flexible tip ablation catheter was introduced into the electrophysiology market, allowing a physician to produce linear lesions by dragging the tip electrode over ridges and valleys inside the beating heart. The flexible tip is able to synchronize with the heart beats and improve catheter stability. However, this tip can still be challenged over some surfaces such as a trabeculated surface with many small pockets where the tip cannot sit appropriately to make good contact. Smooth cardiac tissue surfaces may also be challenging and may be prone to tip movement and slippage during ablation. Catheter sliding can result in poor tissue contact and lead to unpredictable lesion dimensions. Furthermore, ablations are performed at various tip orientations, ranging from parallel to perpendicular orientations as well as in-between angled orientations. Especially at an angled orientation, the electrode-tissue contact area would be more variable with each beat. Hence, there is still a clinical need for an ablation catheter with enhanced electrode-tissue contact that can navigate and touch all types of cardiac surfaces in a healthy or diseased beating heart.

US 5,676,662 A describes a catheter for mapping and ablating cardiac tissue, wherein the catheter comprises a helical electrode. US 5,865,843 A describes a medical, neurological lead including a helical anchor that is raised or channeled into the exterior of the lead. Soft tissue and a fibrotic sheath form about a valley of the helical anchor of the lead such that the lead is fixed longitudinally and laterally, acutely and chronically, by the anchor.

US 5,871,523 A describes a device for ablating tissue within the body having an element with an energy emitting region helically wound about and along the axis of the element.

US 6,090,104 A describes an electrode catheter comprising a tubular body with a distal section having a flexible tubular portion, wherein the flexible tubular distal section is covered by at least one spirally wrapped flat ribbon electrode.

US 6,458,123 B1 describes an ablation catheter carrying an ablation electrode at its distal portion. The ablation electrode can be made from a helically shaped hypodermic tube. This tube is wound so that each turn of the tubing touches neighboring turns.

US 7,048,734 B1 describes a system for ablating tissue within a body comprising a plurality of longitudinally spaced electrodes on a guide element and a controller for selectively disconnecting at least one of the electrodes from the source of tissue ablating energy.

US 7,229,450 B1 discloses an introducer system for use with a pacemaker lead including a plastic sheath, wherein a central lumen of the sheath is configured to permit introduction of the lead and includes a flexible, kink-resistant section having a helical pleat defining a helical groove. The helical groove is intended to house a conductor extending from a mapping probe to a pacing system analyzer.

US 2005/0055020 A1 discloses a helical ablation electrode including a fluid lumen for delivering an irrigation fluid to the electrode for cooling the electrode.

US 2007/0005053 A1 discloses an array of ring electrodes mounted about the outside surface of the distal end of an ablation catheter. An insulating surface coating on each ring comprises a contoured opening that exposes the conductive band beneath. The insulating coating mitigates potential edge effects that create hotspots and can result in unwanted tissue damage during an ablation procedure.

Based on the above background, it is an objective of the present invention to provide an ablation catheter with an enhanced electrode-tissue contact that safely enables cooling of the electrode and irrigation of the tissue to be ablated.

This objective is achieved with a catheter for ablating tissue within a human or animal body having the features of claim 1. Such a catheter comprises an elongated catheter shaft extending along a catheter axis, wherein a distal end portion of the catheter shaft is configured as a tip electrode. Furthermore, it comprises an irrigation liquid space arranged inside the catheter shaft.

According to the presently claimed invention, the tip electrode is constructed with or comprises at least in a section shaped as a first helix around (and along) the catheter axis. Particularly, the tip electrode, is configured to deliver energy to the tissue to be ablated. For this purpose, energy is transferred to the tip electrode which, in turn, transfers this energy to the tissue to be ablated. Often, radiofrequency energy, i.e. a high frequent current, is used for ablating purposes. But also, electroporation andpulsed field ablation, are typically applied ablation techniques that generally can be performed with the aid of the presently described ablation catheter. In an embodiment, the tip electrode has a helical form and thus builds the first helix. This first helix has a plurality of first windings and at least one first vent between two axially adjacent first windings in each case. The at least one first vent enables a flow connection between the irrigation liquid space to an outside of the catheter, particularly to an outside of the tip electrode. Thus, if an irrigation liquid is provided to the irrigation liquid space, it can exit the irrigation liquid space and flow through the at least one first vent to an outside of the catheter and thus cool the tip electrode. In one embodiment, tip electrode, particularly the first helix, essentially consists of a biocompatible, electrically conductive material, such as for example gold or platinum-iridium alloy, or comprises such biocompatible, electrically conductive material, e.g. in form of a coating. To prevent a complete closure of the at least one first vent, at least one first distance element is arranged between two axially adjacent first windings in an embodiment. Expressed in other words, the at least one first distance element guarantees that the at least one first vent remains always open to such an extent that an irrigation liquid can pass from the irrigation liquid space to an outside of the catheter shaft through the at least one first vent.

The helical shape of the tip electrode in connection to a radially oriented first vent guarantees that the tip electrode is, on the one hand, very flexible to contact different types of tissue and, on the other hand, is able to deliver the irrigation liquid exiting through the at least one vent, thereby cooling the tip electrode.

The tissue to be ablated is, in an embodiment, cardiac tissue such as atrial tissue, ventricular tissue, myocardium, pericardium, or epicardium, in particular scarred tissue.

Ventricular fibrillation is a common arrhythmia that can lead to sudden cardiac death (SCD). Patients with implantable cardioverter defibrillator (ICD) for prevention of SCD can be exposed to inappropriate ICD activations or shocks, which in turn can correlate with worse outcomes including pain, anxiety, depression, post-traumatic stress disorder, myocardial injury, and increased mortality. Catheter ablation has emerged as an effective therapy in select patients with ICDs to reduce the risk of SCD (1). However, there is a lack of appropriate high-resolution mapping tools to better understand the initiation and mechanism for VTs. The present catheter with microelectrodes can be used to delineate the scar regions inside the heart of these ICD patients for targeting the appropriate ablation sites.

In an embodiment, the at least one first distance element forms an integral part of one of the first windings, i.e. the at least one first distance element and one of the first windings are formed as one piece. Thus, it is not necessary to design and construct individual first distance elements, but rather to design the individual windings of the helix such that they automatically comprise the at least one first distance element.

In an embodiment, the at least one first distance element is shaped as an axial protrusion extending from a first of the first windings towards a second of the first windings along the catheter axis. Thus, the at least one first distance element can be constructed in the form of a crest, a stand or a projection. Since the at least one first distance element only forms part of one of two adjacent windings but is not connected with the other of the two adjacent windings, the flexibility between the individual windings is still given. Thus, the at least one first distance element does not impair any movement between two adjacent windings of the first helix aside from the avoidance of a total closure of the at least one first vent formed between the two windings.

In an embodiment, the at least one first distance element does not radially protrude from the first windings to an outside of the catheter shaft. Thus, the at least one first distance element does not extend over an outer envelope of the catheter shaft or the tip electrode, respectively. In an embodiment, the at least one first distance element is flush with the remainder of the first helix. Thus, the first helix with its individual windings and the at least one distance element can have a (totally) flush outer appearance. In another embodiment, an undulating outer surface of the helical section of the tip electrode is provided; this will be explained in more detail below.

In an embodiment, a distal end portion of the irrigation liquid space is at least in sections shaped as a second helix winding around the catheter axis. The second helix has a plurality of second windings and at least one second vent. The at least one second vent enables a flow connection between an inside of the irrigation liquid space to an outside of the irrigation liquid space. Thus, an irrigation liquid that is provided to an interior of the irrigation liquid space can exit the irrigation liquid space through the second vent and can subsequently exit the tip electrode through the at least one first vent. In this context, it is not necessary that the at least one first vent and the at least one second vent are (in a flush manner) adjusted to each other since the irrigation liquid can also flow through an interspace arranged between an outside of the irrigation liquid space and the helical section of the tip electrode or the at least one first vent formed in this helical section.

Thus, it is possible that the ablation catheter according to the invention, particularly the tip electrode, comprises two helices, one inside the other, wherein the first helix surrounds the second helix. In an embodiment, the first helix and the second helix have the same or different pitch and/or the same or different numbers of windings. In an embodiment, the first helix and the second helix have opposite winding directions. In an embodiment, the at least one first vent and the at least one second vent have similar or identical dimensions. In an embodiment, the at least one second vent is realized in the form of a plurality of micro holes. Thereby, the individual micro-holes may be equally spaced over the distal end portion of the irrigation liquid space, wherein particularly the distal end portion of the irrigation space extends through distal end portion of the catheter shaft being configured as tip electrode as described above. In an embodiment, the size of the micro-holes varies along the distal end portion of the irrigation space, and particularly increases with decreasing distance of the micro-holes to a distal end of the irrigation liquid. It is possible in this embodiment that a larger volume of irrigation liquid can exit from the irrigation liquid space at least in some sections, e.g. at a distal end of the distal end portion of the irrigation liquid space rather than at a proximal end of the distal end portion of the irrigation liquid space.

In an embodiment, the at least one second vent is arranged between two axially adjacent second windings in each case. In this case, the second vent is similarly or identically constructed like the first vent. In an embodiment, at least one second distance element is arranged between two axially adjacent second windings. In this context, the at least one second distance element prevents a complete closure of the at least one second vent. Thus, the at least one second distance element has the same purpose for the second helix as the at least one first distance element has for the first helix. Furthermore, the at least one second distance element can be constructed in the same way as the at least one first distance element is. All embodiments of the first distance element can be directly transferred to the second distance element. If the at least one first distance element and the at least one second distance element are provided, it is always guaranteed that an irrigation liquid can exit the irrigation liquid space to an outside of the tip electrode, irrespective of the amount of bending of the tip electrode.

In one embodiment, the second helix essentially consists of or comprises biocompatible, particularly super-elastic, material, such as nitinol. Generally, it is possible that both the first helix and the second helix are constructed as a right-handed helix or a left-handed helix. In an embodiment, the first helix is a right-handed or left-handed helix and the second helix is oriented in the opposite direction. Thus, one of the helices is a right-handed helix and the other is a left-handed helix in this embodiment. Then, a particularly high stability of the ablation catheter is possible, while the ablation catheter has at the same time a sufficiently high degree of flexibility.

In an embodiment, the tip electrode has a circular or elliptical cross-section. Then, it can particularly well abut against (cardiac) tissue to be ablated, particularly against acute contours of the tissue to be ablated.

In an embodiment, the tip electrode comprises at least one proximal temperature sensor at the proximal end of the tip electrode. By such a proximal temperature sensor, the influence of an ablation process to tissue regions somewhat remote from the ablation site can be detected. Particularly due to edge effects, the proximal temperature sensor can measure the highest temperature along the tip electrode. Dependent on the temperature measurement by the proximal temperature sensor, the amount of irrigation liquid provided through the irrigation liquid space to the tissue surrounding the tissue to be ablated can be controlled. If the temperature of the tip electrode increases, the amount of cooling irrigation liquid may also be increased. This will finally lead to a temperature decrease at the tip electrode.

In an embodiment, the tip electrode comprises at least one distal temperature sensor and/or at least one microelectrode and/or at least one distal irrigation vent at the distal end of the tip electrode. In this context, the at least one irrigation vent enables a flow connection between the irrigation liquid space and an outside of the catheter, particularly an outside of the tip electrode. By a distal temperature sensor, the tip electrode temperature directly underneath the tissue to be ablated or at the tissue directly surrounding the tissue to be ablated can be particularly measured more accurately and quickly. Comparing the results of a proximal temperature sensor and a distal temperature sensor can give a local temperature information along the ablating tip electrode and thus enable improved temperature- controlled energy delivery during the ablation procedure. One or more microelectrodes at the distal end of the tip electrode may be used mainly for high resolution mapping of specific target areas, such as detecting scar borders in the cardiac tissue. Energy can also be delivered through the microelectrodes only for localized ablations.

In an embodiment, the catheter tip electrode comprises at least one microelectrode at the distal end of the tip electrode. In an embodiment, the at least one microelectrode is partially arranged at a lateral outside or outer surface of the tip electrode and partially arranged at the distal end face of the tip electrode. Thus, the microelectrode has a bent outer shape and extends both over the lateral outside or outer surface and the end face of the tip electrode. Then, tissue to be ablated can be particularly well contacted by this microelectrode in all catheter tip orientations in a beating heart, particularly during ablation procedure

In an embodiment, the irrigation liquid space, particularly configured as a tubing, surrounds a wiring compartment, particularly in form of a channel, through which at least one wiring, particularly in form of one or more electrically conductive wires, is guided towards the distal end of the tip electrode. The wiring, is used to provide the tip electrode, a microelectrode and/ a temperature sensor arranged at the distal end of the tip electrode with electric energy and/or to transmit electric signals detected by the microelectrode and/or generated by the temperature sensor and/or the temperature sensor towards a control unit connected to the ablation catheter or a catheter handle connected to the catheter, particularly at the proximal end of the catheter. The wiring may comprise one or more electrically conductive wires, wherein each of the tip electrode, microelectrode(s) and temperature sensor(s) may be individually electrically contacted by an electrically conductive wire and connected to a voltage source and to the control unit, respectively. As described above the one or more electrically conductive wires are arranged in the wiring compartment, particularly in form of a channel, wherein the channel particularly extends to the proximal end of the catheter or to the above described handle.

It is possible that the irrigation liquid space is designed as hollow cylinder or that it surrounds the irrigation liquid space in form of a helix or helical tube. Other geometric arrangements are also generally possible. With the wiring compartment or channel surrounded by but separated from the irrigation liquid space (without fluid communication to an inside of the irrigation liquid space), the irrigation liquid can safely exit the irrigation liquid space through the at least one second vent and subsequently the tip electrode through the at least one first vent. Thus, the wiring necessary for electrically contacting the tip electrode, the microelectrode or the temperature sensor at the distal end of the tip electrode will not hinder such flow of irrigation liquid.

The wiring compartment or channel may be realized in form of a flexible inner tube. In an embodiment, this flexible inner tube extends loosely inside a space surrounded by the irrigation liquid space. Then, the movement of the irrigation liquid space and the distal end portion of the catheter shaft in general are not impeded by the flexible inner tube, guiding the aforementioned wiring towards the distal end face of the tip electrode.

In an embodiment, the tip electrode has, in its helical section, an undulating surface comprising hills valleys, wherein the at least one first vent is arranged in one of the valleys If a plurality of first vents is provided, all of them are arranged in the valleys in this embodiment. Such an arrangement facilitates an exit of irrigation liquid through the at least one first vent and enhances the catheter-tissue contact due to radially protruding contact portions of the tip electrode. In an aspect, the present invention relates to a method for ablating tissue within the body of a human or animal in need of such ablation. This method comprises the steps explained in the following.

First, a catheter is advanced towards a tissue site at which an ablation of tissue is to be carried out. This catheter comprises an elongated catheter shaft extending along (and around) a catheter axis and an irrigation liquid space arranged inside the catheter shaft, wherein a distal end portion of the catheter shaft is configured as a tip electrode. The tip electrode is at least in sections shaped as a first helix around (and along) the catheter axis. The tip electrode, particularly this first helix is configured to deliver energy to the tissue to be ablated and has a plurality of first windings and at least one first vent between two axially adjacent first windings in each case. The at least one first vent enables a flow connection between the irrigation liquid space to an outside of the catheter, particularly to an outside of the tip electrode. To prevent a complete closure of the at least one first vent, at least one first distance element or stand is arranged between two axially adjacent first windings in an embodiment. Afterwards, an irrigation liquid is provided to the irrigation liquid space of the catheter shaft, particularly of the tip electrode. Furthermore, it is allowed that the irrigation liquid exits the tip electrode through the at least one first vent.

Furthermore, energy is applied to the tip electrode, particularly to the first helix, and optionally to the at least one microelectrode arranged at the distal end of the tip electrode.

Afterwards, energy is introduced from the tip electrode, particularly from the first helix, and optionally from the at least one microelectrode into the tissue to be ablated. This results in an ablation of the tissue to be ablated. At the same time, the tip electrode and the tissue, particularly to be ablated, - is provided with the irrigation liquid.

The steps explained in the preceding paragraphs do not necessarily need to be performed in the explained order. Rather, any other order leading to generally the same effect (ablation of tissue to be ablated and irrigating the tip electrode and its surrounding tissue) is also encompassed from the claimed method.

In an embodiment, the energy introduced into the tissue to be ablated comprises radiofrequency energy or electric current. Particularly, the electric current is preferably introduced with a pulsed field i.e. ultrarapid (<ls) electrical fields are applied to the tissue to be ablated, which results in poration of cell membranes and apoptosis or cell death within the tissue (electroporation).

The presently described ablation catheter has, in certain aspects or embodiments, the following properties: • The compliant, undulating tip of the ablation catheter improves electrode-tissue contact in a beating heart with various tissue surfaces including trabeculations and valleys with small pockets where the corrugated section can potentially fit into the tissue pockets for a more efficient energy transfer into the tissue.

• The corrugated tip design enhances the tissue gripping capability to minimize catheter slipping in smooth tissue areas for a more consistent contact area during ablation, resulting in more predictable lesion dimensions.

• Increased surface area resulting from the helical gaps and corrugated tip design lowers current density during energy delivery and provides a broader range of safe ablation parameters than existing high power-short duration (HP-SD) catheters.

• The catheter enables creation of predictable lesions in the atria and ventricles using HP- SD ablation for shallow lesions, as well as conventional ablation parameters for deeper lesions in a single catheter.

• The corrugated, compliant tip addresses the challenges of ablating different cardiac surfaces such as trabeculations and smooth surfaces. It enables good catheter stability and tissue contact with various cardiac surfaces in a beating heart, especially when the catheter tip orientation is angled.

• The dual-layer, dual helix tip design increases the range of movement to achieve consistent tissue contact and better temperature-controlled irrigated ablation.

• It has mapping and ablation capability for pulmonary vein isolation (PVI) and allows ablating non-PV triggers for atrial fibrillation (AF) patients, thereby eliminating the need for a second ablation catheter.

• It has mapping and ablation capability for ventricular tachycardia, especially the microelectrodes to delineate ischemic scar borders and to collect electrograms to determine tip-tissue contact. All embodiments described with respect to the catheter can be combined in any desired way and can be transferred either individually or in any desired combination to the described method, and vice versa.

Further details of aspects of the present invention will be described in the following making reference to exemplary embodiments and accompanying Figures. In the Figures:

Figure 1A shows a lateral view from the outside onto a first embodiment of an ablation catheter tip electrode;

Figure IB shows a front view onto the distal end face of the ablation catheter tip electrode of Figure 1A; Figure 1C shows a first partially cut lateral view of the ablation catheter tip electrode of Figure 1A;

Figure ID shows a second partially cut lateral view of the ablation catheter tip electrode of Figure 1A;

Figure 2 shows another lateral view onto the ablation catheter tip electrode of Figure 1 A while abutting cardiac tissue;

Figure 3A shows a lateral view onto a second embodiment of an ablation catheter tip electrode;

Figure 3B shows a front view onto the distal end face of the ablation catheter tip electrode of Figure 3 A; Figure 3C shows a partially cut lateral view of the ablation catheter tip electrode of Figure 3 A; Figure 3D shows another lateral view onto the ablation catheter tip electrode of Figure 3 A to illustrate its bending capability;

Figure 4 A shows a front view onto the distal end face of a third embodiment of an ablation catheter tip electrode; and

Figure 4B shows a front view onto the distal end face of a fourth embodiment of an ablation catheter tip electrode. Figure 1 A shows a lateral view of a first embodiment of distal end of an ablation catheterl comprising a catheter shaft 2, wherein a distal end portion is configured as a tip electrode 3. The tip electrode 3 comprises a plurality of windings 4 forming a first helix 5. The tip electrode 3, particularly the first helix 5, is configured to deliver energy to the tissue to be ablated, e.g. a high frequency current. Thus, the tip electrode 3, particularly the first helix 5, acts as an electrode for ablation. Between two windings 4 in each case, a first vent 6 is formed. For better illustration purposes, only some of the first vents 6 are marked with the respective numeral reference. Also, only some of many of other elements in this and the following Figures will be marked with the respective numeral reference to allow a better understanding of the respective Figures.

Furthermore, a plurality of stands 7 is formed at the windings 4. These stands 7 serve as first distance elements. The stands 7 prohibit a complete closure of the first vents 6 so that the first vents 6 always remain open to at least a small extent so that an irrigation liquid can pass the first vents 6 from an inside of the catheter shaft 2 to an outside of the tip electrode 3.

At the proximal end of the tip electrode 3 of the catheter shaft 2, a plurality of proximal thermocouples 8 serving as proximal temperature sensors is arranged. These proximal thermocouples 8 enable a localized temperature measurement of the tip electrode, particularly at typical “hot spots” of ablation tip electrode 3.

At the distal end of the distal end portion 3, three microelectrodes 9 are arranged which are configured to detect electrophysiological signals from the tissue, e.g. in a condensed area, and may additionally serve for ablating tissue by, e.g., radiofrequency, electroporation, or pulsed electric field.

The tip electrode 3 of the catheter shaft 2 forms a corrugated, compliant ablation electrode being constructed with a helical, undulating surface with first vents 6 for the delivery of irrigation fluid. The undulating surface enhances the electrode-tissue contact area particularly in tissue areas with ridges, valleys, and trabeculated surfaces where small pockets exist. The corrugated section of the tip may partially fit into these small pockets of trabeculations for better contact and therefore improved energy transfer into the tissue to create contiguous lesions. Also, the corrugated electrode surface minimizes slipping or undesirable movement of the catheter tip in smooth tissue areas. Another feature of this novel ablation electrode is the plurality of first vents 6, providing compliance for the entire tip to move synchronously with the beating heart tissue. A plurality of stands 7 maintains the first vents 6 open at all times for irrigation purposes. The tip can be composed of gold, platinum- iridium, or other alloys with high electrical and thermal conductivity.

Figure IB shows the distal end face of the tip electrode 3 of the ablation catheter 1 of Figure 1 A. In this and all following Figures, similar elements will be denoted with the same numeral references. Besides the three microelectrodes 9 already known from Figure 1 A, the depiction of Figure 1 B also illustrates three distal thermocouples 10 arranged in between the three microelectrodes 9. These three distal thermocouples 10 enable a tip electrode temperature measurement directly at the location where ablation is carried out, particularly when the tip electrode 3 is oriented perpendicularly or angled to the tissue. Furthermore, a distal vent 11 is arranged in a central area of the tip electrode 3. This distal vent 11 allows irrigation liquid to exit an inside of the tip electrode 3 in the direction of the catheter axis extending along the ablation catheter 1. In contrast, the first vents 6 shown in Figure 1 A allow a radial outflow of irrigation liquid from an inside of the catheter shaft 2. When taking Figure 1 A and Figure IB together, it can be seen that the three microelectrodes 9 extends both to an outside or outer (lateral) surface on the lateral side of tip electrode 3 (cf. Figure 1A) and on the distal end face of the tip electrode 3 of the catheter shaft 2 (cf. Figure IB). This arrangement allows a particularly good electrode-tissue contact between the microelectrodes 9 and the tissue to be ablated in all tip electrode orientations.

The proximal thermocouples 8 and the distal thermocouples 10 provide immediate temperature feedback to a software-controlled RF generator for adjusting ablation parameters such as power and irrigation liquid flow. With multiple temperature sensors 8, 10 embedded in the corrugated tip, this will enable RF ablations using the recently reported high-power short-duration (HP-SD) approach for producing shallow lesions safely, as well as ablations using conventional energy levels for creating deeper lesions. Also a plurality of microelectrodes 9 are embedded on the distal end of the tip to allow the collection of high resolution, localized electrograms which may help delineate scar borders of the heart where sources of arrhythmias can originate, and can also be used to capture near-field electrogram signals to determine catheter contact. Each of the three microelectrodes 9 is configured in such a way so that at least one of the three microelectrodes 9, and most likely two of the three microelectrodes 9, will stay in tissue contact at any tip orientation (perpendicular, parallel, or any angle in-between).

Figure 1C shows the ablation catheter 1 of Figure 1A in a partially cut side view. In this view, it can be seen that a plurality of second windings 12 is arranged inside the catheter shaft 2. These second windings 12 form a helical irrigation liquid space 13. With the help of a plurality of second vents 14, an irrigation liquid can exit the irrigation liquid space 13 and can enter an intermediate space 15 between an outside of the irrigation liquid space 13 and an inside of the catheter shaft 2 to afterwards exit the tip electrode 3 through the first vents 6

Figure ID shows another partially cut side view of the ablation catheter 1 of Figure 1 A, wherein even more elements are cut than in the depiction of Figure 1C.

In the depiction of Figure ID, an interior 16 of the irrigation liquid space 13 is visible. Furthermore, a flexible tube 17 serving as wiring compartment is arranged inside the irrigation liquid space 13 without, however, having fluid communication with the interior 16 of the irrigation liquid space 13. By this arrangement, it is possible to guide a plurality of wiring 18 towards the distal end of the tip electrode 3 and thus to connect the microelectrodes 9 and the distal thermocouples 10 with a corresponding control unit (not shown).

Figure 2 shows the ablation catheter 1 of Figure 1A during intended operation, i.e., when contacting an atrial wall 19 as an exemplary embodiment of (cardiac) tissue to be ablated. Due to the helical arrangement of the tip electrode 3, the ablation catheter 1 can directly lean against the atrial wall 19, even if this atrial wall 19 is (irregularly) curved. In doing so, the first vents 6 form big gaps at a convex side of the tip electrode 3, wherein only small gaps are formed by the first vents 6 on a concave side of the tip electrode 3. The stands 7 avoid a complete closure of the gaps between the individual first windings 4 of the first helix 5 so that also on the concave side of the tip electrode 3 an exit of irrigation liquid to the surrounding tissue is possible. However, much more irrigation liquid can exit the catheter shaft 2 on the convex side of the tip electrode 3. This guarantees for a safe and efficient cooling of the atrial wall 19.

The undulating electrode surface can “grip” onto a smooth tissue area in the atria to limit potential tip slippage. With the tip flexed, the helical first vents 6 open up further on the tissue contacting surface of the tip electrode 3, providing more flow for enhanced electrode cooling. Unlike solid tip irrigated ablation catheters where some of the irrigation ports can be blocked by tissue depending on the tip’s location within the heart, this corrugated design helps keeping the irrigation fluid flowing out at all times. Moreover, the electrode-tissue contact area is increased by the irrigation fluid, providing a virtual electrode effect and carrying RF current into the tissue. This can reduce the current density and enable the application of higher power safely. Additionally, the compliant tip can move in unison with the beating heart and respiration cycles, producing a consistent electrode-tissue contact area during ablation for a more consistent and efficient energy delivery. This results in more predictable lesion dimensions.

Figure 3 A shows another embodiment of an ablation catheter 1. The general setup of this ablation catheter 1 is similar to the setup of the ablation catheter 1 shown in Figure 1A. However, the ablation catheter 1 of the embodiment shown in Figure 3 A does not comprise an undulated lateral surface of the tip electrode 3. Rather, first windings 4 form once again a helix 5 which has, however, a flush outer surface. Stands 7 serve once again that first vents 6 remain open to at least a small extent all the time. Thus, also the embodiment of the ablation catheter 1 shown in Figure 3 A enables an outflow of irrigation liquid from an inside of the catheter shaft 2 to an outside thereof. Also the ablation catheter 1 of Figure 3 A comprises proximal thermocouples 8 arranged at a proximal end of the tip electrode 3. Furthermore, it comprises microelectrodes 9 arranged on the distal end face of the tip electrode 3. In contrast to the embodiment shown in Figures 1 A to ID, the microelectrodes 9 of the ablation catheter 1 of Figure 3 A are only arranged on a distal end face of the distal end portion 3, but do not extend on a lateral outside of the distal end portion 3.

This can be seen in more detail in Figure 3B, illustrating besides the microelectrodes 9 also distal thermocouples 10 and distal irrigation vents 11.

Figure 3C shows a partially cut view of the ablation catheter 1 of Figure 3A. Also, this ablation catheter 1 comprises a plurality of second windings 12 forming and irrigation liquid space 13. And irrigation liquid provided to an interior of the irrigation liquid space 13 can exit from this irrigation liquid space 13 through a plurality of second vents 14 that are arranged between individual second windings 12. In order to avoid complete closure of these second vents 14, a plurality of second stands 20 is provided at the individual windings 12. These second stands 20 have the same purpose and the same function as the stands 7 that can also be denoted as first stands.

The arrangement of an interior helical irrigation liquid space 13 and an exterior helix 5 of the tip electrode 3 can also be denoted as dual layer helix so that the ablation catheter 1 comprises a dual layer helical tip. If both helices are oriented in opposite direction as shown in Figures 1C and 3C, this leads to a particularly stable, yet sufficient flexible arrangement of the distal end portion 3 of the ablation catheter 1.

Figure 3D illustrates the bendability of the tip electrode 3 of the ablation catheter 1. The tip electrode 3 of the ablation catheter 1 can be bent radially away from a catheter axis A along which the catheter shaft 2 extends. This is illustrated by two arrows in Figure 3D directing towards possible bent orientations of the distal end portion 3 of the ablation catheter 1. The bent orientations of the tip electrode 3 of the ablation catheter 1 are also illustrated in figure 3 D.

The helical arrangement of the tip electrode 3 enables 360° bending freedom. Due to the possibility of irrigation liquid to exit through the first vents 6 formed between the individual windings 4 of the helix 5 to an outside of the catheter shaft 2, also a 360° surface irrigation is made possible. Thus, the concrete orientation of the ablation catheter 1 with respect to the tissue to be ablated is no longer of importance for the ablation success. Rather, the fully symmetric design of the tip electrode 3 of the ablation catheter 1 enables in any orientation successful and reliable tissue ablation.

The first stands 7 and the second stands 20 can vary in shape and size to control the gap size between adjacent spiral cuts. The outer layer (i.e., the helix 5) can be made of gold, platinum- iridium, or other alloys conducive for catheter ablation. The inner layer (i.e., the irrigation liquid space 13) can be made out of Nitinol for its preferred mechanical properties. The combined dual layers provide structural integrity and 360 degrees of bending freedom about the central longitudinal axis of the tip. This dual helix type tip can move synchronously with the beating heart in any catheter orientation for a consistent electrode-tissue contact throughout the entire duration of RF ablation therapy. The tip’s compliant property enables the catheter to produce predictable lesions, a feature that may be somewhat lacking in catheters with a standard, solid, irrigated tip. A plurality of distal thermocouples 10 are attached on the distal end and a plurality of proximal thermocouples 8 are attached on the proximal end of the tip where the highest temperatures are expected to be found during application of RF energy. Also included in this embodiment is the plurality of micro- electrodes 9 at the distal end of the tip which may help to map and ablate sensitive tissue areas such as the Purkinje fibers.

Figure 4A shows a front view onto the distal end face of the tip electrode 3 of another embodiment of an ablation catheter 1. Thereby, this distal end face resembles the distal end face of the ablation catheter shown in Figure IB. However, the catheter shaft 2 and tip electrode 3 of the ablation catheter shown in Figure 4A does not necessarily need to have the same design as the catheter shaft and tip electrode 3 of the ablation catheter 1 shown in Figures lAto ID.

A round cross-section of the tip electrode 3 of the ablation catheter 1 enables a tight catheter- tissue interaction with fine structures of, e.g., the tissue of an atrial wall 19.

Structures with acute contours such as the exterior of an organ, can be even better contacted if the distal end portion of the ablation catheter 1 has an elliptical cross-section, as illustrated in Figure 4B. In this context, the general elements, i.e., microelectrodes 9, distal thermocouples 10 and a distal irrigation vent 11 remain the same also with an elliptical cross- section of the tip electrode3 of the ablation catheter 1.

The elliptical tip profile may be especially useful for epicardial ablation where the tip is deployed between the pericardium and the epicardium.

Claims

1. Catheter for ablating tissue within a human or animal body, comprising an elongated catheter shaft (2) extending along a catheter axis (A) and an irrigation liquid space (13) arranged inside the catheter shaft (2), wherein a distal end portion (3) of the catheter shaft (2)is configured as a tip electrode (3), characterized in that the tip electrode (3) comprises at least in a section shaped as a first helix (5) around the catheter axis (A), the tip electrode (3), particularly the first helix (5), being configured to deliver energy to the tissue to be ablated, wherein the first helix (5) comprises a plurality of first windings (4) and at least one first vent (6) between two axially adjacent first windings (4) in each case, wherein the at least one first vent (6) enables a flow connection between the irrigation liquid space (13) and an outside of the catheter (1), and wherein at least one first distance element (7) is arranged between two axially adjacent first windings (4), the at least one first distance element (7) preventing a complete closure of the at least one first vent (6).

2. Catheter according to claim 1, characterized in that the at least one first distance element (7) forms an integral part of one of the first windings (4).

3. Catheter according to claim 1 or 2, characterized in that the at least one first distance element (7) is shaped as an axial protrusion extending from a first of the first windings (4) towards a second of the first windings (4) along the catheter axis (A).

4. Catheter according to any of the preceding claims, characterized in that the at least one first distance element (7) does not radially protrude from the first windings (4) to an outside of the tip electrode (3).

5. Catheter according to any of the preceding claims, characterized in that a distal end portion of the irrigation liquid space (13) is at least in a section shaped as a second helix around the catheter axis (A), the second helix having a plurality of second windings (12) and at least one second vent (14), wherein the at least one second vent (14) enables a flow connection between an inside (16) of the irrigation liquid space (13) and an outside of the irrigation liquid space (13).

6. Catheter according to claim 5, characterized in that at least one second distance element (20) is arranged between two axially adjacent second windings (12), the at least one second distance element (20) preventing a complete closure of the at least one second vent (14).

7. Catheter according to claim 5 or 6, characterized in that the first helix (5) is a right- handed or a left-handed helix and in that the second helix is oriented in the opposite direction.

8. Catheter according to any of the preceding claims, characterized in that the tip electrode (3) has a circular or elliptical cross-section.

9. Catheter according to any of the preceding claims, characterized in that the tip electrode (3) comprises at least one proximal temperature sensor (8) at a proximal end of the tip electrode (3).

10. Catheter according to any of the preceding claims, characterized in that the tip electrode (3) comprises at least one of a distal temperature sensor (10), a microelectrode (9) and a distal irrigation vent (11) enabling a flow connection between the irrigation liquid space (13) and an outside of the catheter (1), particularly an outside of the tip electrode (3).

11. Catheter according to any of the preceding claims, characterized in that the tip electrode (3) comprises at least one microelectrode (9) at a distal end of the tip electrode (3), wherein the at least one microelectrode (9) is partially arranged at a lateral outside of the tip electrode (3) and partially arranged at a distal end face of the tip electrode (3)

12. Catheter according to any of the preceding claims, characterized in that the irrigation liquid space (13) surrounds a wiring compartment (17) through which at least one wiring (18) is guided towards a distal end of the tip electrode (3)

13. Catheter according to any of the preceding claims, characterized in that the tip electrode (3) has, in its helical section, an undulating surface comprising hills and valleys, wherein the at least one first vent (6) is arranged in at least one of the valleys.

14. Method for ablating tissue within a body of a human or animal in need of such ablation, the method comprising the following steps: a) advancing a catheter (1) towards a tissue site at which an ablation of tissue is to be carried out, wherein the catheter (1) comprises an elongated catheter shaft (2) extending along a catheter axis (A) and an irrigation liquid space (13) arranged inside the catheter shaft (2), wherein a distal end portion is configured as a tip electrode (3), wherein the tip electrode (3) comprises at least in sections shaped as a first helix (5) around the catheter axis (A), the tip electrode (3), particularly the first helix (5), being configured to deliver energy to the tissue to be ablated and having a plurality of first windings (4) and at least one first vent (6) between two axially adjacent first windings (4) in each case, wherein the at least one first vent (6) enables a flow connection between the irrigation liquid space (13) and an outside of the catheter (1), particularly an outside of the tip electrode (3), wherein at least one first distance element (7) is arranged between two axially adjacent first windings (4), the at least one first distance element (7) preventing a complete closure of the at least one first vent (6), b) providing irrigation liquid to the irrigation liquid space (13) and allowing the irrigation liquid to exit the tip electrode (3)) through the at least one first vent (6), c) applying energy to the tip electrode (3), particularly to the first helix (5), and optionally to the at least one microelectrode (9) arranged at a distal end of the tip electrode (3), d) introducing energy from the tip electrode (3), particularly from the first helix (5), and optionally from the at least one microelectrode (9) into the tissue to be ablated and thus ablating the tissue to be ablated, e) cooling the tip electrode (3) and the immediate electrode-tissue interface with the irrigation liquid.

15. Method according to claim 14, characterized in that the energy is introduced into the tissue to be ablated comprises radiofrequency energy, pulsed field energy, or an electric current.