Patent Description:
Arrhythmias are abnormal heart rhythms that are typically caused by a small area of cardiac tissue that produces irregular heartbeats. Cardiac ablation is a medical procedure that can be performed to treat an arrhythmia by destroying the area of the cardiac tissue causing the irregular heartbeats.

<CIT> describes a method for electrophysiologic measuring endpoints of ablation lesions created in fibrillating substrates. The method measures, during an ablation procedure that produces a lesion, electrical activity in cardiac tissue in proximity to the lesion, and then compares the measurements to determine if the lesion is able to block myocardial propagation.

<CIT> describes a method for using pacing to assess a lesion created by ablation. The method monitors intracardiac ablation progress by evaluating a pacing signal that is captured while ablation energy is directed to intracardiac tissue. The ablation is considered to be successful by failing to capture the signal while the signal is generated at a maximum predetermined pacing voltage.

<CIT> describes a system configured to assess the formation of lesions both during and after ablation of tissue. The system includes an emitter that conveys electromagnetic radiation to tissue, thereby causing the tissue to responsively generate a photoacoustic wave. The system also includes an ultrasound transducer that generates a signal indicative of a characteristic of the tissue responsive to the photoacoustic wave.

<CIT> describes a method for identifying and visualizing gaps between cardiac ablation sites. The method includes receiving location of the cardiac ablation sites, measuring distances between the sites, and identifying one or more gaps between the sites.

<CIT> discloses a method and system for visualization of electrophysiology information sensed by electrodes on a catheter. The disclosure included recording times of electrode signal acquisition, designating a reference electrode signal acquisition, assigning a relative time to each recorded time of electrode signal acquisition relative to the reference electrode signal acquisition, identifying the electrodes with signal acquisition, correlating assigned relative times to identified electrodes to generate a sequence of electrode signal acquisitions, and generating a visual representation of the sequence of electrode signal acquisitions generating a visual representation with a graphical image of the electrodes, wherein individual electrodes are visually marked to represent the sequence of electrode acquisitions.

There is provided, in accordance with the present invention, a system as claimed in claim <NUM> and a computer software product as claimed in claim <NUM>. Additional embodiments are provided in the dependent claims.

The disclosure is herein described, by way of example only, with reference to the accompanying drawings, wherein:.

During an ablation procedure, a lesion can be created on ostial tissue in order to prevent electrical signals from traveling between a heart (also referred to herein as a first region of tissue) and a blood vessel such as a pulmonary vein (also referred to herein as a second region of tissue). However, there may be instances when the lesion has a gap which enables electrical signals to travel from the heart to the blood vessel.

Embodiments of the present invention provide systems for assessing a lesion formed between first and second regions of tissue in a body cavity. As described hereinbelow, a first activation signal is applied to the tissue or is sensed in the tissue by a first probe in contact with the tissue at a stimulus location in the first region, the first activation signal having a first activation peak at a first time. While applying or sensing the first activation signal, second activation signals are received from a second probe having multiple electrodes in contact with the tissue at respective sensing locations in the second region, the respective second activation signals having respective second activation peaks sensed by the electrodes following the first activation signal. Based on a temporal relation between the first and second activation peaks and a spatial relation between the stimulus location and the sensing locations, one of the multiple electrodes proximal to a gap in the lesion can be identified, and a map of the body cavity with the identified electrode marked on the map can be displayed.

The identified electrode is typically proximal to an area of the tissue that was not successfully ablated. Therefore, systems implementing embodiments of the present invention can help a medical professional identify an area of body cavity tissue that can be targeted for re-ablation.

<FIG> is a schematic, pictorial illustration of a medical system <NUM> comprising medical probes <NUM>, <NUM> and a control console <NUM>, <FIG> is a schematic pictorial illustration of a distal end <NUM> of medical probe <NUM>, and <FIG> is a schematic pictorial illustration of a distal end <NUM> of medical probe <NUM>, in accordance with an embodiment of the present invention. Medical system <NUM> may be based, for example, on the CARTO® system, produced by Biosense Webster Inc. (Irvine, California, U. In embodiments described hereinbelow, medical probes <NUM> and <NUM> can be used for diagnostic or therapeutic treatment, such as for performing ablation procedures in a heart <NUM> of a patient <NUM>. Alternatively, medical probe <NUM> and <NUM> may be used, mutatis mutandis, for other therapeutic and/or diagnostic purposes in the heart.

Medical probe <NUM> may also be referred to as either a mapping catheter or a first probe, and medical probe <NUM> may be also referred to as either an integrated catheter or a second probe.

During a medical procedure, a medical professional <NUM> inserts medical probes <NUM> and <NUM> into respective biocompatible sheaths (not shown) that have been pre-positioned in a body cavity (e.g., a chamber of heart <NUM>) of the patient so that distal ends <NUM> and <NUM> of the medical probes enter the body cavity. By way of example, distal end <NUM> of probe <NUM> comprises a balloon <NUM> (<FIG>) that is typically formed from bio-compatible material such as polyethylene terephthalate (PET), polyurethane, Nylon, or Pebax.

Control console <NUM> is connected, by a cable <NUM>, to body surface electrodes, which typically comprise adhesive skin patches <NUM> that are affixed to patient <NUM>. Control console <NUM> comprises a processor <NUM> that, in conjunction with a current tracking module <NUM>, determines position coordinates of distal end <NUM> inside heart <NUM> based on impedances measured between adhesive skin patches <NUM> and one or more electrodes <NUM> (also referred to herein as microelectrodes <NUM>) that are attached to an exterior wall of balloon <NUM>. While embodiments herein describe using microelectrodes <NUM> as location sensors, the microelectrodes may perform other tasks (e.g., measuring electrical activity of heart <NUM>) during a medical procedure.

In conjunction with current tracking module <NUM>, processor <NUM> also determines position coordinates of distal end <NUM> inside heart <NUM> based on impedances measured between adhesive skin patches <NUM> and an electrode <NUM> that is coupled to distal end <NUM> and is configured to function as an impedance-based position transducer. In embodiments described herein, electrode <NUM> can be configured to apply a signal to tissue in heart <NUM>, and/or to measure a certain physiological property (e.g., the local surface electrical potential) at a location in heart <NUM>. Electrode <NUM> is connected to control console <NUM> by wires (not shown) running through medical probe <NUM>.

Processor <NUM> may comprise real-time noise reduction circuitry <NUM> typically configured as a field programmable gate array (FPGA), followed by an analog-to-digital (A/D) ECG (electrocardiograph) signal conversion integrated circuit <NUM>. The processor can pass the signal from A/D ECG circuit <NUM> to another processor and/or can be programmed to perform one or more algorithms disclosed herein, each of the one or more algorithms comprising steps described hereinbelow. The processor uses circuitry <NUM> and circuit <NUM>, as well as features of modules which are described in more detail below, in order to perform the one or more algorithms.

Although the medical system shown in <FIG>, <FIG> uses impedance-based sensing to measure a location of distal ends <NUM> and <NUM>, other position tracking techniques may be used (e.g., techniques using magnetic-based sensors). Impedance-based position tracking techniques are described, for example, in <CIT>, <CIT> and <CIT>. Magnetic position tracking techniques are described, for example, in <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, <CIT> and <CIT>. The methods of position sensing described hereinabove are implemented in the above-mentioned CARTO® system and are described in detail in the patents cited above.

Control console <NUM> also comprises an input/output (I/O) communications interface <NUM> that enables the control console to transfer signals from, and/or transfer signals to electrodes <NUM>, <NUM> and adhesive skin patches <NUM>. Based on signals received from electrodes <NUM>, <NUM> and adhesive skin patches <NUM>, processor <NUM> can generate a map <NUM> that shows the position of distal ends <NUM> and <NUM> in the patient's body. During the procedure, processor <NUM> can present map <NUM> to medical professional <NUM> on a display <NUM>, and store data representing the map in a memory <NUM>. Memory <NUM> may comprise any suitable volatile and/or non-volatile memory, such as random access memory or a hard disk drive. In some embodiments, medical professional <NUM> can manipulate map <NUM> using one or more input devices <NUM>. In alternative embodiments, display <NUM> may comprise a touchscreen that can be configured to accept inputs from medical professional <NUM>, in addition to presenting map <NUM>.

In embodiments of the present invention, balloon <NUM> comprises one or more electrodes <NUM>, that are typically used for ablation and so are also referred to herein as ablation electrodes <NUM>, attached to the exterior wall of balloon <NUM>. In the configuration shown in <FIG>, ablation electrodes <NUM> have non-polygonal shapes, and microelectrodes <NUM> are positioned in "islands" within the ablation electrodes. Electrodes <NUM> and <NUM> can be fabricated with the balloon and typically comprise gold overlaying the exterior wall of balloon <NUM>.

Control console <NUM> also comprises an ablation module <NUM>, and an inflation module <NUM>. Ablation module <NUM> is configured to monitor and control ablation parameters such as the level and the duration of ablation power (e.g., radio-frequency energy) conveyed to ablation electrodes <NUM>. Inflation module <NUM> is configured to monitor and control the inflation of balloon <NUM>.

In some embodiments, inflation module <NUM> can use irrigation fluid to inflate balloon <NUM>, and control the inflation of the balloon by controlling a flow rate of the irrigation fluid into the balloon. In these embodiments balloon <NUM> typically comprises multiple small fenestrations (not shown) that allow the irrigation fluid to exit the balloon. These fenestrations are typically <NUM>-<NUM> millimeters in diameter.

As shown in <FIG>, balloon <NUM> is formed around a tubular shaft <NUM> that can be manipulated by medical professional <NUM> in order to extend through the balloon. By way of example, tubular shaft <NUM> encompasses an end section <NUM> that is formed as a complete or partial lasso, i.e., as a preformed arcuate structure. In embodiments described herein, end section <NUM> may also be referred to as lasso <NUM>.

The radius of curvature of end section <NUM>, when unconstrained, is typically between <NUM> and <NUM>. Because the arc structure is resilient and, possibly, slightly helical, when end section <NUM> is positioned in heart <NUM> (or in a pulmonary vein, as described hereinbelow), the end section will press against the heart tissue or the blood vessel tissue over the entire length of the arc, thus facilitating good tissue contact. The arcuate and possibly helical shape of end section <NUM> may be maintained, for example, by incorporating a thin strut made from a shape memory material, such as Nitinol (not shown), in the desired shape within the end section. The strut is made sufficiently flexible to permit the end section to straighten during insertion and withdrawal through tubular shaft <NUM>, but to resume its arcuate form when it is unconstrained inside the heart chamber.

End section <NUM> comprises an array of electrodes <NUM> distributed along the end section. Electrodes <NUM> may also be referred to herein as lasso electrodes <NUM>, and have respective widths between <NUM> and <NUM>, and are spaced between <NUM> and <NUM> apart. Lasso electrodes <NUM> are typically used for sensing. Electrodes <NUM>, <NUM> and <NUM> are connected to control console <NUM> by wires (not shown) running through medical probe <NUM>.

<FIG> is a flow diagram that schematically illustrates a given algorithm for performing and verifying an ablation procedure in heart <NUM>, and <FIG> is a schematic detail view of distal ends <NUM> and <NUM> in heart <NUM> while performing and verifying the ablation procedure on ostial tissue <NUM> of pulmonary vein <NUM>, in accordance with an embodiment of the present invention. As described hereinbelow, processor <NUM> can analyze a first and second activation signal having respective first and second activation peaks in order to identify a gap in a lesion created during an ablation procedure.

In a first positioning step <NUM>, medical professional <NUM> positions distal end <NUM> in a chamber of heart <NUM>, and manipulates medical probe <NUM> so that end section <NUM> extends from shaft <NUM>. Upon extending from tubular shaft <NUM>, section <NUM> forms into a lasso shape, thereby pressing lasso electrodes <NUM> against sensing locations <NUM> on intravenous tissue <NUM>. In an inflation step <NUM>, medical professional <NUM> inflates balloon <NUM>, and manipulates medical probe <NUM> so that ablation electrodes <NUM> press against ostial tissue <NUM>. To inflate balloon <NUM>, medical professional <NUM> conveys an inflation signal (e.g., via a given input device <NUM>) to inflation module <NUM>, and upon receiving the inflation signal, the inflation module delivers an inflation fluid (e.g., irrigation fluid) to balloon <NUM>, thereby inflating the balloon.

In an ablation step <NUM>, medical professional <NUM> conveys an ablation signal to ablation module <NUM>, and in response, the ablation module delivers radio-frequency (RF) energy to ablation electrodes <NUM>, thereby performing an ablation procedure on ostial tissue <NUM> that creates a lesion <NUM>. In a second positioning step <NUM>, medical professional <NUM> positions distal end <NUM> in the chamber of heart <NUM>, and manipulates medical probe <NUM> so that electrode <NUM> presses against a stimulus location <NUM> on intracardiac tissue <NUM>. Electrode <NUM> may be used to inject a pacing signal into location <NUM> or to acquire a natural signal from the location. The pacing or natural signal is herein termed an activation signal. In a signal selection step <NUM>, if a first activation signal comprises a pacing signal, then in a pacing step <NUM>, medical console conveys, to stimulus location <NUM> on intracardiac tissue <NUM> (via electrode <NUM>), a pacing signal having a pacing signal peak. If the first activation signal comprises a natural signal, i.e., a signal generated by the heart, the flow diagram continues in a step <NUM>, described below.

In a comparison step <NUM>, if processor <NUM>, in conjunction with current tracking module <NUM> and while executing the given algorithm, receives second activation signals from lasso electrodes <NUM> (i.e., the lasso electrodes in contact with intravenous tissue <NUM>), control continues to a step <NUM> wherein the processor identifies a respective second activation peak for each of the second signals. Steps of the flow diagram subsequent to step <NUM> are described below. In embodiments described herein, the second activation signals comprise signals that lasso electrodes <NUM> detect at sensing locations <NUM> in response to electrode <NUM> delivering the first activation signal to stimulus location <NUM>.

<FIG> is a schematic detail view of lesion <NUM>, stimulus location <NUM> and sensing locations <NUM>, and <FIG> is a chart <NUM> showing a first activation signal <NUM> sensed or applied by electrode <NUM>, and second activation signals <NUM> detected by lasso electrodes <NUM>, in accordance with an embodiment of the present invention. In embodiments described herein, first activation signal <NUM> has a first activation peak <NUM> at a first time, and each second activation signal <NUM> has a respective second activation peak <NUM> at a respective second time subsequent to the first time. In some embodiments, processor <NUM> can present, in map <NUM>, the schematic detail view of lesion <NUM> (e.g., stimulus location <NUM> and sensing locations <NUM>) that is shown in <FIG>.

In <FIG>, sensing locations <NUM>, second activation signals <NUM> and second activation peaks <NUM> can be differentiated by appending a letter to the identifying numeral, so that the sensing locations comprise sensing locations 116A-116D, the second activation signals comprise second activation signals 144A-144D, and the second activation peaks comprise second activation peaks 148A-148D. In embodiments described herein, a first given lasso electrode <NUM> detects, at sensing location 116A, second activation signal 144A having second activation peak 148A, a second given lasso electrode <NUM> detects, at sensing location 116B, second activation signal 144B having second activation peak 148B, a third given lasso electrode <NUM> detects, at sensing location 116C, second activation signal 144C having second activation peak 148C, and a fourth given lasso electrode <NUM> detects, at sensing location 116D, second activation signal 144D having second activation peak 148D.

Returning to the flow diagram of the given algorithm, after step <NUM> processor <NUM> determines a temporal relation between first activation peak <NUM> and second activation peaks <NUM> in a first determination step <NUM>, and determines a spatial relation between stimulus location <NUM> and sensing locations <NUM> in a second determination step <NUM>. In a second identification step <NUM>, processor <NUM> identifies, based on the temporal and the spatial relations, a given lasso electrode <NUM> that is closest (i.e., of all the lasso electrodes) to a locus <NUM> (<FIG>) of a presumed gap <NUM>, i.e. a location of gap <NUM>, in lesion <NUM>.

In operation, processor <NUM> determines the spatial relation between stimulus location <NUM> and sensing locations <NUM> by first identifying stimulus location <NUM> and sensing locations <NUM>. In embodiments described herein, stimulus location <NUM> comprises a location of mapping electrode <NUM> and sensing locations <NUM> comprise respective locations of lasso electrodes <NUM>. In the configuration shown in <FIG>, processor <NUM> uses impedance-based position tracking techniques to determine the respective locations of mapping electrode <NUM> and lasso electrodes <NUM>. Examples of impedance-based position tracking techniques are described in <CIT>, <CIT> and <CIT> cited above.

In an alternative configuration, medical system <NUM> can use magnetic-based position tracking techniques to determine the respective locations of mapping electrode <NUM> and lasso electrodes <NUM>. Examples of magnetic-based position tracking techniques are described in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>and <CIT> cited above.

As described herein, an ablation procedure forms lesion <NUM> between a first region <NUM> and a second region <NUM>, and the lesion comprises gap <NUM> at locus <NUM>. As described supra, electrode <NUM> applies or senses the first activation signal to stimulus location <NUM>, and processor <NUM> receives the second activation signals from lasso electrodes <NUM> at respective sensing locations <NUM>.

As shown in <FIG>, the second activation signals detected at sensing locations <NUM> travel paths (i.e., from stimulus location <NUM>) that comprise path segments <NUM> and <NUM>. In the example shown in <FIG>, a first given second activation signal detected by a first given lasso electrode <NUM> travels from stimulus location <NUM> to sensing location 116A via path segments <NUM> and 134A, a second given second activation signal detected by a second given lasso electrode <NUM> travels from stimulus location <NUM> to sensing location 116B via path segments <NUM> and 134B, a third given second activation signal detected by a third given lasso electrode <NUM> travels from stimulus location <NUM> to sensing location 116C via path segments <NUM> and 134C, and a fourth given second activation signal detected by a fourth given lasso electrode <NUM> travels from stimulus location <NUM> to sensing location 116D via path segments <NUM> and 134D.

For purposes of visual simplicity, path segments <NUM> and <NUM> are shown as straight lines radiating from a single point in gap <NUM>. Additionally, while <FIG> shows, for purposes of visual simplicity, a single path segment <NUM> between locus <NUM> and stimulus location <NUM>, the second activation signals may comprise different paths from the stimulus location to the locus of the gap.

As shown in chart <NUM>, first activation peak <NUM> occurs at time <NUM>, second activation peak 144A occurs at time <NUM>, second activation peak 144B occurs at time <NUM>, second activation peak 144C occurs at time <NUM>, and second activation peak 144D occurs at time <NUM>. By determining a temporal relation between times <NUM>-<NUM>, and determining a spatial relation between locations <NUM> and <NUM>, processor <NUM> can determine the closest lasso electrode to locus <NUM>. In the example shown in chart <NUM>, determining the given lasso electrode may comprise identifying, as the temporal relation, that second activation peak 148C is closest in time to first activation peak <NUM>, and then determining, as the spatial relation, that locus <NUM> is in proximity to the given lasso electrode at sensing location 116C.

Returning to the flow diagram, in a presentation step <NUM>, processor <NUM> presents, in map <NUM> on display <NUM>, the given electrode, and the method ends. In one embodiment, processor <NUM> can overlay an icon (not shown) representing lasso <NUM> on map <NUM> and highlight a section of the icon, thereby identifying the given lasso electrode that is closest to the presumed gap in the lesion (i.e., the third given lasso electrode in the example shown in <FIG>). Medical professional <NUM> can then use the position of the identified lasso electrode to re-ablate a region, in proximity to the identified position, that typically includes gap <NUM>.

In some embodiments, the lasso electrodes are positioned at respective locations <NUM> on intravenous tissue <NUM>, and if processor <NUM> receives initial second activation signals <NUM> from the lasso electrodes (and therefore detects that gap <NUM> exists), medical professional <NUM> can reposition lasso <NUM> in pulmonary vein <NUM> so that the lasso electrodes are positioned at respective subsequent sensing locations on the intravenous tissue different from sensing locations <NUM>. Using embodiments described herein, electrode <NUM> may be used to inject (or detect) a subsequent pacing signal having a subsequent first activation peak into location <NUM>.

Once processor <NUM> receives subsequent second activation signals having respective subsequent second activation peaks from the repositioned lasso electrodes, the processor can determine a probable location of locus <NUM> (i.e., a probable location of the gap), based on (a) the temporal relation between first activation peak <NUM> and second activation peaks <NUM> and the spatial relation between stimulus location <NUM> and sensing locations <NUM>, and (b) a subsequent temporal relation between the subsequent first activation peak and the subsequent second activation peaks and a subsequent spatial relation between stimulus location <NUM> and the subsequent sensing locations.

In one embodiment the probable location of locus <NUM> is a position where a sum of a first distance, between sensing location <NUM> to a selected region of lesion <NUM>, and of a second distance, between a subsequent sensing location to the selected region, is a minimum. In an alternative embodiment, the sum is weighted according to a first time, between the first activation peak <NUM> and the closest in time second activation peak <NUM>, and a second time, between the subsequent first activation peak and the closest in time subsequent second activation peak.

In some embodiments, processor <NUM> can mark, in map <NUM>, the probable location of the locus, and present the updated (i.e., marked) map on display <NUM>.

Returning to step <NUM>, if the first activation signal comprises a natural signal, then in a receiving step <NUM>, processor <NUM>, operating in conjunction with current tracking module <NUM> and executing the given algorithm, receives a natural signal of heart <NUM> that was sensed by electrode <NUM>, and the method continues with step <NUM>. The natural signal has a natural signal activation peak, and in embodiments using a natural signal, the first activation peak comprises the natural signal activation peak.

Returning to step <NUM>, if processor <NUM> does not receive any second activation signals from lasso electrodes <NUM>, then the ablation procedure was successful, and the method ends.

While embodiments described herein use mapping catheter <NUM> and integrated catheter <NUM> to help identify locus <NUM> in ostial tissue <NUM> between a chamber of heart <NUM> and intravenous tissue <NUM> of pulmonary vein <NUM>, using any number of catheters to help identify the locus of the gap in the ablation lesion in the ostial tissue between any given cardiac chamber and any blood vessel (e.g., a pulmonary artery) emanating from the given cardiac chamber is considered to be within the scope of the present invention. For example, separate catheters can be used to perform the ablation and to sense the second activation signals.

Additionally, while embodiments described herein use ablation electrodes <NUM> on balloon <NUM> to create lesion <NUM> and use lasso electrodes <NUM> (i.e., on lasso <NUM>), using any type of ablation electrodes to create the lesion and using any type of catheter having multiple electrodes that can be simultaneously pressed against sensing locations <NUM> is also considered. Furthermore, while medical probe <NUM> comprises a single lasso <NUM> having electrodes <NUM> that detect the second activation signals, medical probe <NUM> may refer to more than one signal detection catheters, each of the signal detection catheters having respective subsets of electrodes <NUM>.

Claim 1:
An apparatus (<NUM>) configured to assess a lesion (<NUM>) formed to prevent electrical signals from travelling between a heart (<NUM>)and blood vessel emanating from the heart, the apparatus comprising:
a first medical probe (<NUM>) comprising a first electrode (<NUM>) adapted to contact tissue at a stimulus location in the heart;
a second medical probe (<NUM>) comprising multiple second electrodes (<NUM>) adapted to contact tissue at respective sensing locations in the blood vessel;
a display (<NUM>); and
a processor (<NUM>) configured:
to apply to or to sense from the first electrode in contact with the tissue at the stimulus location in the heart, a first activation signal (<NUM>) having a first activation peak (<NUM>) at a first time,
to receive, from the second electrodes in contact with the tissue at the respective sensing locations in the blood vessel, respective second activation signals (144A-D) having respective second activation peaks (148A-D) sensed by the electrodes following the first activation signal,
to identify one of the multiple electrodes proximal to a gap (<NUM>) in the lesion by finding a given electrode among the multiple electrodes that has a respective second activation peak closest in time after the first activation peak among the second activation signals, and
to present, on the display, a map (<NUM>) of the body cavity with the identified electrode marked on the map by presenting, on the map, an icon representing a distal end of the second medical probe, and highlighting the found electrode on the map.