Patent Description:
Cardiac arrythmias are commonly treated by ablation of myocardial tissue in order to block arrhythmogenic electrical pathways. For this purpose, a catheter is inserted through the patient's vascular system into a chamber of the heart, and an electrode or electrodes at the distal end of the catheter are brought into contact with the tissue that is to be ablated with a suitable energy. In some cases, high-power radio-frequency (RF) electrical energy is applied to the electrodes in order to ablate the tissue thermally. Alternatively, high-voltage pulses may be applied to the electrodes in order to ablate the tissue by irreversible electroporation (IRE) also known as pulse field ablation.

Some ablation procedures use basket catheters, in which multiple electrodes are arrayed along the spines of an expandable basket assembly at the distal end of the catheter. The spines bend outward to form a basket-like shape and contact tissue within a body cavity. For example, <CIT> describes devices and methods for electroporation ablation therapy, with the device including a set of spines coupled to a catheter for medical ablation therapy. Each spine of the set of spines may include a set of electrodes formed on that spine. The set of spines may be configured for translation to transition between a first configuration and a second configuration.

<CIT> provides systems for nerve modulation through the wall of a blood vessel. An example system for nerve modulation may include an elongate member extending along a central elongate axis and having a proximal end and a distal end. The elongate member may have a radially expandable member disposed proximate the distal end. A tubular sheath may be cooperatively engaged with the expandable member such that the expandable member is collapsed when in the sheath and can expand when moved distally relative to and past a distal end of the sheath. The expandable member may include a plurality of electrodes and a plurality of spacer struts.

The invention provides a medical probe according to claim <NUM>. Embodiments are provided by the dependent claims.

Certain methods which do not form part of the invention, are described with reference to the medical probe of the present invention. Whilst no claim is directed to these methods per se, the medical probe is capable of being used and is intended to be used in such methods. For instance, there is provided a method including inserting, into a cavity of an organ of a patient, a medical probe including a shaft and a basket assembly connected at a distal end of the shaft. The basket assembly includes (i) multiple electrically-conductive spines that are electrically-connected to one another so as to form a distributed electrode, and (ii) a plurality of spine mounted electrodes disposed along the spines. Using the plurality of spine mounted electrodes, electrical activity is sensed in the cavity while the distributed electrode is prevented from indenting tissue in the cavity.

There is additionally provided a method for producing a medical probe. The method includes producing a basket assembly, including multiple electrically-conductive spines that are electrically-connected to one another so as to form a distributed electrode, and a plurality of spine mounted electrodes, which are disposed along the spines and are configured to (i) sense electrical activity in the cavity, and (ii) prevent the distributed electrode from indenting tissue in the cavity. The basket assembly is connected to a shaft configured for insertion into a cavity of an organ of a patient.

A multi-electrode cardiac catheter typically comprises a distal-end assembly disposed with multiple electrodes. For example, a basket catheter typically comprises an expandable frame of spines which is coupled to the distal end of a shaft for insertion into a cavity of an organ of a patient.

Basket catheters are useful to perform ablation procedures rapidly and efficiently, since the spines of the basket catheter (and thus the electrodes on the spines) are able to contact and ablate the tissue at multiple locations concurrently. These spine mounted electrodes, however, can indent the tissue during the procedure, which can lead to local overheating, resulting in charring and/or other trauma, in particular with RF ablation. The use of electrodes having smooth, rounded profiles can be helpful in mitigating these effects, but by itself its use does not eliminate the problems of tissue damage.

Embodiments of the present invention that are described herein provide a basket catheter with a distributed electrode configured to apply ablative signal safely. The distributed electrode is made of the basket spines wired to deliver RF and/or IRE in unipolar mode against an indifferent electrode (e.g., a back patch). In addition, multiple spine mounted electrodes are disposed on the spines, for performing electrophysiological (EP) sensing or ablating. The spines are electrically-conductive and are typically electrically uninsulated (exposed) except for small regions around each of the spine mounted electrodes. The spines are electrically-connected to one another (e.g., by contacting each other at the distal end of the basket and/or shorting connecting wires together), so the spines together form the distributed electrode (e.g., for use in RF ablation in a unipolar mode, but other possible usages are described below). The insulation typically covers short sections of the spines, just enough to prevent sparking between a spine mounted electrode and a spine, or between electrodes on adjacent spines. In some configurations, where the spines are configured as a single electrode, the mounted electrode (or electrodes) can be the indifferent electrode(s).

The distributed electrode spreads the ablation (RF or IRE) energy in a way that can reduce thermal hazard to tissue, such as charring. Typically, the spine mounted electrodes are made thicker than the spines, causing the basket assembly to act as a mechanical barrier that prevents the distributed electrode from burying into the tissue (e.g., identing the tissue). In other words, the thick spine mounted electrodes act as "bumpers" to prevent the spines (the distributed electrode) from pressing too strongly against the tissue during the RF ablation. At the same time, the spine mounted electrodes can be used to acquire electrograms to verify an efficacy of the ablation, such as in an arrhythmia-treatment procedure of pulmonary vein isolation.

<FIG> is a schematic pictorial illustration of a catheter-based electrophysiological procedure utilizing an ablation system <NUM> comprising a basket catheter <NUM>, in accordance with an embodiment of the present invention. Elements of system <NUM> may be based on components of the CARTO® system, produced by Biosense Webster, Inc. (Irvine, California). Spines of a basket assembly <NUM> connected at the distal end of catheter <NUM> contact each other at a distal end of the basket, so the spines form a distributed electrode <NUM>, as further described in <FIG>.

In one embodiment, distributed electrode <NUM> is used for RF ablation. In another embodiment, distributed electrode <NUM> may be used as a reference electrode for electrophysiological mapping done using the mounted electrodes <NUM>. In yet another embodiment, distributed electrode <NUM> may serve as a shared reference electrode during IRE ablation by spine mounted electrodes <NUM>. For all the above purposes, the spines are electrically shortcircuited and connected to a single wire (not shown) running in shaft <NUM> to a console <NUM>. Alternatively, each spine may be individually wired and all wires are electrically shorted together within ablation system <NUM>. Spine mounted electrodes <NUM> are individually wired and can each be used separately.

A physician <NUM> navigates a catheter <NUM> through the vascular system of a patient <NUM> into a chamber of a heart <NUM> of the patient, and then deploys basket catheter assembly <NUM>. The proximal end of basket catheter assembly <NUM> is connected to the distal end of a shaft <NUM>, which physician <NUM> steers using a manipulator <NUM> near the proximal end of catheter <NUM>. Basket catheter assembly <NUM> is inserted in a collapsed configuration through a tubular sheath <NUM>, which passes through the vascular system of patient <NUM> into the heart chamber where the ablation procedure is to be performed.

Once inserted into the heart chamber, basket catheter assembly <NUM> is deployed from the tubular sheath and allowed to expand within the chamber. Catheter <NUM> is connected at its proximal end to a control console <NUM>. A display <NUM> on console <NUM> may present a map <NUM> or other image of the heart chamber with an icon showing the location of basket catheter assembly <NUM> in order to assist physician <NUM> to position the basket assembly at the target location for the ablation procedure.

In one embodiment, once basket catheter assembly <NUM> is properly deployed and positioned in heart <NUM>, physician <NUM> actuates an electrical signal generator <NUM> in console <NUM> to apply electrical energy (such as RF waveforms or high voltage IRE pulses) to distributed electrode <NUM> in a unipolar mode, i.e., between the spine mounted electrodes on basket catheter assembly <NUM> and a separate external common electrode, for example a conductive back patch <NUM> which is applied to the patient's skin. During the ablation procedure, an irrigation pump <NUM> delivers an irrigation fluid, such as saline solution, through shaft <NUM> to basket catheter assembly <NUM>. In this embodiment, spine mounted electrodes <NUM> can be used as electro-physiologically sensing electrodes to acquire electrograms, as discussed in <FIG>.

Typically, catheter <NUM> comprises one or more position sensors (not shown in the figures), which output position signals that are indicative of the position (location and orientation) of basket catheter assembly <NUM>. For example, basket assembly <NUM> may incorporate one or more magnetic sensors which output electrical signals in response to an applied magnetic field. Processor <NUM> receives and processes the signals in order to find the location and orientation coordinates of basket catheter assembly <NUM>, using techniques that are known in the art and are implemented, for example, in the above-mentioned Carto system. Alternatively or additionally, system <NUM> may apply other position-sensing technologies in order to find the coordinates of basket catheter assembly <NUM>. For example, processor <NUM> may sense the impedances between the electrodes on basket catheter assembly <NUM> and body surface electrodes <NUM>, which are applied to the chest of patient <NUM>, and may convert the impedances into location coordinates using techniques that are likewise known in the art. In any case, processor <NUM> uses the coordinates to display the location of basket catheter assembly <NUM> on map <NUM>.

Alternatively, catheter <NUM> and the ablation techniques that are described herein may be used without the benefit of position sensing. In such embodiments, for example, fluoroscopy and/or other imaging techniques may be used to ascertain the location of basket catheter assembly <NUM> in heart <NUM>.

The system configuration that is shown in <FIG> is presented by way of example for conceptual clarity in understanding the operation of embodiments of the present invention. For the sake of simplicity, <FIG> shows only the elements of system <NUM> that are specifically related to basket catheter assembly <NUM> and ablation procedures using the basket assembly.

<FIG> is a schematic side view of basket catheter assembly <NUM> of <FIG>, in accordance with an embodiment of the invention. Basket catheter assembly <NUM> is drawn in expanded state outside sheath <NUM>.

As seen, basket catheter assembly <NUM> has a distal end <NUM> and a proximal end <NUM>, which is connected to a distal end of shaft <NUM>. The basket catheter assembly comprises multiple spines <NUM>, whose proximal ends are conjoined at proximal end <NUM>, and whose distal ends are conjoined at distal end <NUM>. Multiple thick rounded and spine mounted electrodes <NUM> are disposed externally on each of spines <NUM>.

Spines <NUM> are electrically conducting and are uninsulated so that these portions of spines <NUM> (as indicated by lead lines in <FIG>) are exposed to the ambient environment (or biological tissues and fluids). It should be noted that the spines <NUM> are provided with small insulated regions <NUM> around each of electrodes <NUM>. Electrically conducting spines <NUM> contact each other at the distal end <NUM> of the basket, so the exposed surface of the spines form distributed electrode <NUM>. Because of the spines <NUM> being electrically connected together to form the distributed electrode <NUM>, distributed electrode <NUM> can be thought of as a single large electrode.

In the shown expanded state, spines <NUM> bow radially outward. In the collapsed state (not shown), spines <NUM> are straight and aligned parallel to a longitudinal axis of shaft <NUM> to facilitate insertion of basket catheter assembly <NUM> into heart <NUM>.

In one embodiment, spines <NUM> are produced such that the stable state of basket catheter assembly <NUM> is the collapsed state. In this case, when basket catheter assembly <NUM> is pushed out of the sheath, it is expanded by drawing an actuator wire or rod (<NUM> in <FIG>) in the proximal direction through shaft <NUM>. Releasing the actuator rod or puller <NUM> wire allows basket catheter assembly <NUM> to collapse back to its original state. A reference electrode <NUM> can be provided on the actuator rod <NUM> so that far field tissue generated signals can be collected with the signals collected by the spine mounted electrodes <NUM> and used for noise reduction or cancellation.

In another embodiment, spines <NUM> are produced such that the stable state of basket catheter assembly <NUM> is the expanded state of <FIG>. In this case, basket catheter assembly <NUM> opens out into the expanded stated when it is pushed out of the sheath, and the puller wire may be replaced by a flexible pusher rod <NUM> for straightening spines <NUM> before withdrawing the basket catheter assembly back into the sheath.

<FIG> is illustrated in a schematic manner for ease of understanding. It is noted that, the actual shape of spine mounted electrodes <NUM> differs than shown. As another example, in some embodiments irrigation outlets in spines <NUM> allow irrigation fluid flowing within the spines to exit and irrigate tissue in the vicinity of electrodes <NUM>.

In the embodiment shown in <FIG> and <FIG> the spines are electrically in contact one with the other at a distal end of the basket catheter assembly. In another embodiment, the spines are electrically in contact one with the other at a proximal end of basket catheter assembly.

<FIG> is a schematic pictorial illustration of basket catheter assembly <NUM> of <FIG> positioned to ablate an ostium <NUM> of a pulmonary vein, in accordance with an embodiment of the invention. In this exemplary procedure, the catheter is first introduced to the right atrium (RA) via the inferior vena cava (IVC), where it passes through a puncture in the fossa ovalis of the interatrial septum in order to reach the left atrium (LA) <NUM>. Catheter assembly <NUM> is to be distally pressed against ostium <NUM>, with distributed electrode <NUM> conveying RF energy to ostium <NUM> tissue. At the same time spine mounted electrodes <NUM>, due to the electrodes being large and protruding outwards relative the spines of electrode <NUM>, prevent the RF-delivering spines from indenting ostium <NUM> tissue and causing mechanical or thermal damage to tissue during the RF ablation.

In this embodiment, when basket catheter assembly is pressed against tissue, the spine mounted electrodes prevent indentation of tissue by the distributed electrode by being surface mounted on the spines and having a minimal given thickness in the radial direction (e.g., mounted in a spatially biased way to be mostly external to the spines).

Bulky electrodes on a basket catheter, which are asymmetrically mounted on spines with most of the electrode thickness protruding radially outwards the spines, are described in <CIT>.

When pressed against ostium <NUM> tissue, spine mounted electrodes <NUM> acquire electrophysiological signals (e.g., electrograms), and processor <NUM> analyzes these signals to verify that arrhythmogenic electrical pathways are ablated over an entire circumference of ostium <NUM>, so an arrhythmia caused there is fully treated by the ablation.

<FIG> shows an alternative end effector <NUM>' extending along longitudinal axis A-A defined by the tubular shaft <NUM>. In this example, the electrodes <NUM> have a scarab like profile. Specifically, electrode <NUM> is provided with a hole <NUM> extending through the electrode <NUM>. The through hole <NUM> allows the spine <NUM> to be inserted into through hole <NUM> and secured by a suitable technique (e.g., adhesives, mechanical tabs or via welding) to the spine <NUM> where insulation material <NUM> is formed over the exposed surface of spine <NUM> where the spine mounted electrodes <NUM> are located. An irrigation tube <NUM> with irrigation holes <NUM> can be provided to allow for irrigation fluid to be dispersed around the single distributed electrode <NUM> (formed by the electrically shorted spines <NUM>) during ablation. A central electrode <NUM> can be provided to act as a reference electrode for noise reduction of ECG signals or as a return (or indifferent) electrode for ablation purposes.

As shown in the drawings herein, distributed electrode <NUM> (formed by spines <NUM> electrically shorted together) can be practiced in a method to deliver ablative energy in various modes. The ablation modes allow for delivering of ablative energy (RF or IRE) to either one or both of the distributed electrode <NUM> and at least one of the spine mounted electrodes <NUM>. In one mode, ablation energy (RF or IRE) can be provided to at least one of the spine mounted electrodes <NUM> and configuring the distributed electrode <NUM> to act as a return electrode for the ablative energy provided to the spine electrode(s) <NUM>. In another mode, the system can be configured for delivering ablative energy to distributed electrode <NUM> and configuring at least one of the spine mounted electrodes <NUM> as return electrodes. In yet a third mode, ablative energy can be provided in a unipolar mode to the distributed electrode <NUM> or at least one of the spine mounted electrodes <NUM> with the external body electrodes <NUM> acting as the return electrode.

To summarize, the single distributed electrode <NUM> can operate in the following modes: (<NUM>) bipolar ablation mode with one or more of the spine mounted electrodes <NUM> being the return or indifferent electrodes; (<NUM>) bipolar ablation mode with the central electrode (<NUM> or <NUM>) as the return or indifferent electrode; or (<NUM>) unipolar ablation mode with the indifferent electrode being the known electrode patches <NUM>.

On the other hand, spine mounted electrodes <NUM> can be used to: (<NUM>) map or collect electrical signal emanating from biological tissues; (<NUM>) deliver ablative energy in bipolar mode with the distributed electrode <NUM> acting as the return electrode; (<NUM>) deliver ablative energy in bipolar mode with the central electrode <NUM> or <NUM> as the return electrode; or (<NUM>) deliver ablative energy in unipolar mode with the body patch <NUM> as the indifferent electrode.

Moreover, it is noted that the distributed electrode <NUM> can deliver RF energy while the spine mounted electrodes can deliver IRE energy. This can be reversed in that the distributed electrode <NUM> can deliver IRE energy while the spine mounted electrodes <NUM> can deliver RF energy.

Claim 1:
A medical probe, comprising:
a shaft (<NUM>) defining a longitudinal axis, the shaft (<NUM>) configured for insertion into a cavity of an organ of a patient;
a basket assembly (<NUM>), which is connected at a distal end of the shaft (<NUM>) and extending along the longitudinal axis, the basket (<NUM>) comprises:
multiple electrically-conductive spines (<NUM>) that are electrically-connected to one another so as to form a distributed electrode;
characterized in that it comprises
a plurality of spine mounted electrodes (<NUM>), which are disposed along the spines (<NUM>), are electrically insulated from the spines (<NUM>), and are configured to (i) sense electrical activity in the cavity, and (ii) prevent the distributed electrode from indenting tissue in the cavity.