Patent Description:
Various medical probes with multiple electrodes disposed over their distal-end were proposed in the patent literature. For example, <CIT> describes an array of electrodes on a flexible scaffolding, with the ability to collapse into an axial configuration suitable for deploying through a narrow cylindrical channel. The electrode arrays can be placed into the ventricular system of the brain, constituting a minimally invasive platform for precise spatial and temporal localization of electrical activity within the brain, and precise electrical stimulation of brain tissue, to diagnose and restore function in conditions caused by abnormal electrical activity in the brain.

As another example, <CIT> describes system, devices and methods that integrate stretchable or flexible circuitry, including arrays of active devices for enhanced sensing, diagnostic, and therapeutic capabilities. The invention enables conformal sensing contact with tissues of interest, such as the inner wall of a lumen, the brain, or the surface of the heart. Such direct, conformal contact increases accuracy of measurement and delivery of therapy. Further, the invention enables the incorporation of both sensing and therapeutic devices on the same substrate allowing for faster treatment of diseased tissue and fewer devices to perform the same procedure.

<CIT>, which is prior art falling within the terms of <NPL>, describes an apparatus including a catheter and an end effector. At least a portion of the catheter is sized and configured to fit within a lumen of a cardiovascular system. The end effector is positioned at a distal end of the catheter. The end effector includes a panel, a plurality of mapping electrodes positioned on a first surface of the panel, and a plurality of ablation electrodes positioned on the first surface of the panel. The mapping electrodes are configured to sense electrical potentials in tissue contacting the mapping electrodes. The ablation electrodes are operable to ablate tissue contacting the ablation electrodes.

The present invention provides a medical probe including a shaft and an expandable flexible distal-end assembly. The shaft is configured for insertion into a cavity of organ of a patient. The expandable flexible distal-end assembly, which is fitted at a distal-end of the shaft, includes a flat flexible backing sheet, including irrigation channels, and two flexible substrates having respective arrays of electrodes disposed thereon, the substrates attached one on either side of the backing sheet, wherein the distal-end assembly is round or elliptic.

In some embodiments, the irrigation channels are in fluid communication with surrounding blood.

In some embodiments, the substrates have openings formed therein, for flowing coolant from the irrigation channels into the surrounding blood. In other embodiments, the irrigation channels are configured to flow a coolant in a closed loop.

In an embodiment, the flexible substrates are printed circuit boards (PCBs).

In some embodiments, at least one of the electrodes is configured to be interchangeably used as an ablation electrode or as a sensing electrode.

In an embodiment, the flat flexible backing sheet includes Nitinol.

In another embodiment, the distal-end assembly is rectangular.

There is additionally provided a manufacturing method of a medical probe, the method including preparing a flat flexible backing sheet, including irrigation channels. Two flexible substrates are fabricated, that have respective arrays of electrodes disposed thereon. The flexible substrates are attached one on either side of the backing sheet to form a round or elliptic expandable flexible distal-end assembly. The expandable flexible distal-end assembly is fitted at a distal-end of a shaft for insertion into a cavity of organ of a patient.

In some embodiments, fitting the distal-end assembly includes connecting the irrigation channels to a tube running in the shaft.

An expandable distal-end assembly of a probe, such as of a catheter disposed with multiple electrodes for insertion into a cavity of an organ of a patient, may be employed in various clinical applications, such as electro-anatomical mapping and ablation of the cavity walls. The expandable distal-end assembly is coupled to the distal end of a shaft of the catheter, and, in a typical procedure, the catheter is inserted into the cavity (e.g., into a cardiac chamber of a heart) through a sheath with the distal-end assembly in a collapsed configuration. After exiting the sheath inside the heart, the distal-end assembly assumes its expanded configuration.

In acquiring diagnostic electro-potentials from an inner surface of the heart chamber, the electrodes disposed over the distal-end assembly need to be positioned to contact the wall surface of the chamber. Moreover, as many electrodes as possible should be simultaneously positioned in contact with the surface in order to reduce the time taken for the acquisition, and, optionally, to identify propagation directions of electro-potentials. In cases where far-field potentials are to be measured, it is advantageous to have reference electrodes close to, but not touching, tissue, while the acquiring electrodes are in contact with tissue. Such reference electrodes can be used, for example, to subtract unrelated far-field potentials from the diagnostic electro-potentials.

In the present context, a far-field bio-electric signal comes from a region distant from the contacted tissue region. Typically, such far-field bio-electric signals propagate by conduction through blood, and are sensed both by the electrodes in contact with tissue (which, in parallel, sense a "near-field signal") and by the reference electrodes.

Furthermore, when tissue ablation of a heart chamber is required, the electrodes used for the ablation need to be positioned in contact with the surface. Using multiple electrodes that are simultaneously positioned in close proximity one to the other, and also in contact with the surface, can increase the effectiveness of the ablation. For example, in an irreversible electroporation (IRE) ablation mode, this configuration increases the strength of an applied electric field, and, optionally, locally controls a direction of the electric field to achieve better selectivity to irreversibly electroporating cardiac cells only.

While basket catheters and balloon catheters, among others, may have multiple disposed electrodes that can contact the surface simultaneously, the construction of a distal-end assembly for these catheters is complicated and costly.

Embodiments of the present invention that are described hereinafter provide an expandable flexible distal-end assembly configured for sensing and/or ablation comprising two flexible substrates, such as printed circuit boards (PCB), upon which an array of electrodes, together with conductors to the electrodes, are printed. The PCBs are attached (e.g., cemented) on either side of a flat flexible Nitinol backing sheet, within which irrigation channels are formed. The PCB/Nitinol combination may be formed with other elements, such as holes to permit blood flow.

While operating as sensing electrodes, once the distal-end assembly of the catheter has exited from a sheath, which is typically prepositioned in the heart chamber, one of the PCBs of the distal end may be pressed against heart chamber tissue so that its electrodes contact the tissue. The electrodes of the other PCB may be used for far-field acquisition.

In some embodiments, the set of electrodes in contact with tissue may be further used for ablation by switching the electrodes to an ablative power source, with the irrigation channels providing cooling. In one embodiment for IRE ablation, irrigation may be applied to cool electrode edges in order to avoid undesirable thermal effects such as charring or coagulum. In another embodiment, in an RF ablative mode, the irrigation is applied to cool the electrodes so as to maintain acceptable tissue temperature.

In one embodiment, the irrigation is performed by convection, by flowing a coolant (e.g., saline solution) into blood in the vicinity of the electrodes via openings (e.g., holes) in the PCBs connected to the channels. In another embodiment, the irrigation runs in the irrigation channels in a closed loop to cool the electrodes using heat conduction.

The disclosed flexible distal-end assemblies of catheters having double-sided electrode arrays may enable improved EP diagnostics and ablation with greater efficiency and accuracy and in a cost-effective manner.

<FIG> is a schematic, pictorial illustration of a catheter-based cardiac diagnostic and ablation system <NUM> comprising a double-sided electrode catheter <NUM>, in accordance with an embodiment of the present invention. System <NUM> is used to determine the position of a flexible distal-end assembly <NUM> of catheter <NUM>, seen in an inset <NUM> fitted at a distal end of a shaft <NUM>, and subsequently to ablate a target cardiac tissue of a heart <NUM>.

As seen in an inset <NUM>, a flexible distal-end assembly <NUM> of shaft <NUM> of the catheter is inserted through a sheath <NUM> into heart <NUM> of a patient <NUM> lying on a table <NUM>. The proximal end of catheter <NUM> is connected to a control console <NUM>.

In the embodiment described herein, flexible distal-end assembly <NUM> carries, on one facet of the distal-end assembly, electrodes <NUM> for electrophysiological diagnostic purposes, such as sensing arrhythmia activity in tissue inside heart <NUM> and subsequent IRE ablation of the arrhythmogenic tissue. A similar electrode array is disposed on the opposing facet of flexible distal-end assembly <NUM> (shown on <FIG>) and is used to acquire, in parallel, far-field electro-potentials. However, the two opposing facets may reverse functionally depending on which facet is deemed (e.g., by a system processor) to be in contact with tissue.

Expandable frames (e.g., of basket or balloon catheters) carrying diagnostic electrodes and far-field sensing electrodes are described in <CIT>, titled "Electrodes On double-Sided Printed Circuit Board (PCB) To Cancel Far-Field Signal," which is assigned to the assignee of the present patent application.

Physician <NUM> navigates distal-end assembly <NUM> of shaft <NUM> to a target location in heart <NUM> by manipulating shaft <NUM> using a manipulator <NUM> near the proximal end of the catheter and/or deflection from the sheath <NUM>. During the insertion of shaft <NUM>, distal-end assembly <NUM> is maintained in a collapsed or folded configuration by sheath <NUM>. By containing distal-end assembly <NUM> in a collapsed or folded configuration, sheath <NUM> also serves to minimize vascular trauma along the way to target location.

To track positions of diagnostic electrodes <NUM>, a plurality of external electrodes <NUM> is coupled to the body of patient <NUM>; for example, three external electrodes <NUM> may be coupled to the patient's chest, and another three external electrodes may be coupled to the patient's back. (For ease of illustration, only one external electrode is shown in <FIG>. ) In some embodiments, electrodes <NUM> sense potentials induced in heart <NUM> by applying voltages between pairs of external electrodes <NUM>.

A similar position tracking technique to the one described above, that can also be used for tracking the locations of diagnostic electrodes <NUM> inside heart <NUM>, is described in <CIT>, titled "Improved Active Voltage Location (AVL) Resolution," which is assigned to the assignee of the present patent application.

Based on the potentials sensed by electrodes <NUM>, and given the known positions of external electrodes <NUM> on the patient's body, a processor <NUM> calculates an estimated location of at least a portion of electrodes <NUM> within the patient's heart. Processor <NUM> may thus associate any given signal received from electrodes <NUM>, such as an electrophysiological signal, with the location at which the signal was acquired.

Processor <NUM> is comprised in control console <NUM>, and is typically a general-purpose computer, with suitable front end and interface circuits <NUM> for receiving signals from catheter <NUM>, as well as for applying treatment via catheter <NUM> in heart <NUM> and for controlling the other components of system <NUM>. Processor <NUM> typically comprises a general-purpose computer with software programmed to carry out the functions described herein. The software may be downloaded to the computer in electronic form, over a network, for example, or it may, alternatively or additionally, be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory.

In particular, processor <NUM> runs a dedicated algorithm that enables processor <NUM> to perform the disclosed steps, comprising calculations of the locations and respective proximities.

The example configuration shown in <FIG> is chosen purely for the sake of conceptual clarity. The disclosed techniques may similarly be applied using other system components and settings. For example, system <NUM> may comprise other components and perform non-cardiac diagnostics.

<FIG> are isometric views of flexible distal-end assemblies <NUM> and <NUM> of double-sided electrode catheter <NUM> of <FIG>, including a cross-sectional view of the assembly layers with irrigation in closed loop and irrigation by convection, respectively, in accordance with embodiments of the present invention. The shown embodiments depict only elements of the disclosed embodiments that enable the disclosed sensing and/or ablative functionalities. Therefore, additional elements, such as encapsulation of edges in soft material to avoid tissue injury, are not shown. Other features or devices that may be disposed on assemblies <NUM> and <NUM>, such as temperature sensors, are omitted for clarity. Finally, the proportions of assemblies <NUM> and <NUM> are distorted in order to better view the cross-section, where in practice flexible distal-end assemblies <NUM> and <NUM> are typically far thinner compared to their length and width. An actual assembly <NUM> or <NUM> design will balance flexibility (e.g., level of conformity to an anatomy) with contact force of the electrode array.

As <FIG> shows, assembly <NUM> comprises two PCBs <NUM> upon which are printed arrays of electrodes <NUM>. The electrodes are connected to conductors (e.g., wires or metal traces, neither shown) that are proximally connected to electrical wires (also not shown) passing in shaft <NUM>. The PCBs are cemented on either side of a flat flexible Nitinol backing sheet <NUM>, within which irrigation channels <NUM> are formed. The irrigation channels may be formed in various ways, either, for example, as bores surrounded entirely in Nitinol or as depressions in the Nitinol that are covered with one of the PCBs. The irrigation channels are typically connected to a tube running in shaft <NUM> (not shown).

As <FIG> shows, in assembly <NUM> irrigation is performed by convection, by flowing a coolant (e.g., saline solution) into blood in the vicinity of the electrodes via openings <NUM> in the PCBs connected to channels <NUM>. That is, irrigation channel <NUM> are connected to the surface of PCBs <NUM> with vertical fluid passages <NUM> extending from the PCB <NUM> to the channel <NUM> (top and bottom surfaces).

The configurations of distal-end assemblies <NUM> and <NUM> shown in <FIG> are example configurations, which are chosen purely for the sake of conceptual clarity. Any other suitable configuration can be used in alternative embodiments. In an example embodiment, each facet of assembly <NUM> comprises fifty electrodes <NUM> arranged in an array of <NUM>-by-<NUM> electrodes. The size of the array, in the expanded position, is <NUM>-by-<NUM>. The thickness of the assembly is on the order of <NUM>. In the collapsed position, within the sheath, distal-end assembly is typically rolled to assume a diameter of <NUM>. Alternatively, any other suitable sizes can be used. Moreover, the shape of distal-end assemblies <NUM> and <NUM> need not necessarily be rectangular. According to the presently claimed invention,round or elliptic shapes are used.

<FIG> is a flow chart that schematically illustrates a method for manufacturing flexible distal-end assembly <NUM> of <FIG>, in accordance with an embodiment of the present invention. The manufacturing process begins with printing electrodes <NUM> array on a flexible PCB, at an electrode printing step <NUM>. At a cutting PCB step <NUM>, the PCB is cut to fit the size of parts used for PCBs <NUM>.

Next, at an electrical wiring step <NUM>, electrodes <NUM> are wired. Alternatively or additionally, step <NUM> may include printing conductors to connect electrodes <NUM>.

At a flat backing sheet manufacturing step <NUM>, which can be performed in parallel to steps <NUM>-<NUM>, a flat flexible backing sheet <NUM> comprising irrigation channels <NUM> is manufactured.

At an assembling step <NUM>, the two PCB parts <NUM> are attached (e.g., cemented) to either side of the flat flexible backing sheet <NUM> to form the flexible distal-end assembly <NUM>, as described above.

Finally, at a fitting step <NUM>, flexible distal-end assembly <NUM> is fitted at a distal-end of shaft <NUM>, including performing the required electrical and mechanical connections so that assembly <NUM> can be medically used as described in <FIG>.

The example flow chart shown in <FIG> is chosen purely for the sake of conceptual clarity. Additional steps that may be included, such as polishing the edges or encapsulating them in soft material, are omitted for simplicity of presentation.

Although the embodiments described herein mainly address cardiac applications, the methods and systems described herein can also be used in other medical applications, such as in neurology, otolaryngology, and renal denervation.

Claim 1:
A medical probe, comprising:
a shaft (<NUM>) for insertion into a cavity of organ of a patient; and
an expandable flexible distal-end assembly (<NUM>), which is round or elliptic and which is fitted at a distal-end of the shaft (<NUM>) and comprises:
two flexible substrates having respective arrays of electrodes (<NUM>) disposed thereon;
characterised by
a flat flexible backing sheet (<NUM>), comprising irrigation channels (<NUM>), wherein the substrates are attached one on either side of the backing sheet.