Patent Description:
Mapping of electrical potentials in the heart is now commonly performed, using cardiac catheters comprising electrophysiological sensors for mapping the electrical activity of the heart. Typically, time-varying electrical potentials in the endocardium are sensed and recorded as a function of position inside the heart, and then used to map a local electrogram or local activation time. Activation time differs from point to point in the endocardium due to the time required for conduction of electrical impulses through the heart muscle. The direction of this electrical conduction at any point in the heart is conventionally represented by an activation vector, which is normal to an isoelectric activation front, both of which may be derived from a map of activation time. The rate of propagation of the activation front through any point in the endocardium may be represented as a velocity vector. Mapping the activation front and conduction fields aids the physician in identifying and diagnosing abnormalities, such as ventricular and atrial tachycardia and ventricular and atrial fibrillation, which may result from areas of impaired electrical propagation in the heart tissue.

Localized defects in the heart's conduction of activation signals may be identified by observing phenomena such as multiple activation fronts, abnormal concentrations of activation vectors, or changes in the velocity vector or deviation of the vector from normal values. Examples of such defects include re-entrant areas, which may be associated with signal patterns known as complex fractionated electrograms. Once a defect is located by such mapping, it may be ablated (if it is functioning abnormally) or otherwise treated so as to restore the normal function of the heart insofar as is possible. As an illustration, cardiac arrhythmias including atrial fibrillation, may occur when regions of cardiac tissue abnormally conduct electric signals to adjacent tissue, thereby disrupting the normal cardiac cycle and causing asynchronous rhythm. Procedures for treating arrhythmia include disrupting the origin of the signals causing the arrhythmia, as well as disrupting the conducting pathway for such signals, such as by forming lesions to isolate the aberrant portion. Thus, by selectively ablating cardiac tissue by application of energy via a catheter, it is sometimes possible to cease or modify the propagation of unwanted electrical signals from one portion of the heart to another. The ablation process destroys the unwanted electrical pathways by formation of non-conducting lesions.

Accordingly, a suitable EP catheter may have one or more sensor electrodes for measuring electrical signals and/or delivering ablation energy. Each electrode requires its own lead to conduct the received electrical signals through the catheter for recording and processing by instrumentation coupled to the catheter or to transmit the energy for ablation. Further, the EP catheter may also employ one or more location sensors to help track the position of the catheter and determine placement of the electrodes within the patient. Thus, a number of leads may also be required for the location sensors. The multiplicity of leads are typically routed through a lumen in the polymeric tube forming the catheter and must be connected to their respective electrode or location sensor, which represents a significant investment of time and labor as well as being subject to a high failure rate. For example, each lead is fished out through an opening made in the catheter wall, stripped of insulation and welded or soldered to the component and the process is repeated. Moreover, the typical materials used for electrodes, such as platinum or iridium, contribute significantly to the overall cost of the catheter.

Accordingly, it would be desirable to provide a sensor construction that reduces or avoids the use of dedicated electrode materials. Similarly, it would be desirable to provide a more reliable connection between the leads and the components. Further, it would be desirable to deploy such components on a variety of electrophysiologic devices, including catheters, guiding sheaths and others. The techniques of this disclosure as described in the following materials satisfy these and other needs.

<CIT> describes a method and apparatus for manufacturing implantable electrodes having a controlled surface area and integral conductors. <CIT> describes field concentrating antennas for magnetic position sensors. <CIT> describes a catheter positioning system. <CIT> describes a cardiac electrode catheter and a method of manufacturing the same. <CIT> describes an electrophysiology catheter design. <CIT> describes a multilumen body for an implantable medical device. <CIT> (cited under Article <NUM>(<NUM>) EPC) and <CIT> both describe a catheter with improved position and/or location sensing with the use of single axis sensors that are mounted directly along a length or portion of the catheter whose position/location is of interest. The magnetic based, single axis sensors are provided on a single axis sensor (SAS) assembly, which can be linear or nonlinear as needed. A catheter thus includes a catheter body and a distal member of a particular 2D or 3D configuration that is provided by a support member on which at least one, if not at least three single axis sensors, are mounted serially along a length of the support member. The magnetic-based sensor assembly including at least one coil member that is wrapped on the support member, wherein the coil member is connected via a joint region to a respective cable member adapted to transmit a signal providing location information from the coil member to a mapping and localization system. The joint region advantageously provides strain relief adaptations to the at least one coil member and the respective cable member from detaching. In <CIT>, the wire distal and proximal portions of each coil may extend proximally through a lumen of the catheter shaft. A through-hole is formed into the lumen through the sidewall of the catheter shaft portion (through a first layer, a braided mesh and a second layer) for each wire portion. As such, sleeves are not needed. The extruded first layer may be formed as a multi-lumened tubing with lumens (with use of one or more suitable mandrels). The through-hole may be formed to communicate with the lumen, such that the wire portions all pass through the dedicated lumen along the length of the catheter shaft.

Further features and advantages will become apparent from the following and more particular description of the preferred embodiments of the disclosure, as illustrated in the accompanying drawings, and in which like referenced characters generally refer to the same parts or elements throughout the views, and in which:.

At the outset, it is to be understood that this disclosure is not limited to particularly exemplified materials, architectures, routines, methods or structures as such may vary. Thus, although a number of such options, similar or equivalent to those described herein, can be used in the practice or embodiments of this disclosure, the preferred materials and methods are described herein.

It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments of this disclosure only and is not intended to be limiting.

The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of the present disclosure and is not intended to represent the only exemplary embodiments in which the present disclosure can be practiced. The term "exemplary" used throughout this description means "serving as an example, instance, or illustration," and should not necessarily be construed as preferred or advantageous over other exemplary embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary embodiments of the specification. It will be apparent to those skilled in the art that the exemplary embodiments of the specification may be practiced without these specific details. In some instances, well known structures and devices are shown in block diagram form in order to avoid obscuring the novelty of the exemplary embodiments presented herein.

For purposes of convenience and clarity only, directional terms, such as top, bottom, left, right, up, down, over, above, below, beneath, rear, back, and front, may be used with respect to the accompanying drawings. These and similar directional terms should not be construed to limit the scope of the disclosure in any manner.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one having ordinary skill in the art to which the disclosure pertains.

As noted above, certain types of electrical activity within a heart chamber are not cyclical. Examples include arterial flutter or arterial fibrillation, and ventricular tachycardia originating in scars in the wall of the ventricle that have resulted from infarcts. Such electrical activity is random from beat to beat. To analyze or 'map' this type of electrical activity, it is desirable to provide an electrophysiologic catheter with one or more electrodes to measure the electrical signals. Further, RF energy may be delivered to selected treatment areas for ablation based therapies, including for example, isolation of a source of irregular electrical signals by blocking electrical conduction. Correspondingly, one or more electrodes may be used to deliver ablation energy. Still further, the catheter may employ one or more location sensors to help visualize or otherwise determine the relative position of the catheter within the patient. According to the techniques of this disclosure, one or more of the electrodes and/or location sensors may be formed from a coil of wire wound around the elongated body of the electrophysiologic catheter. In some embodiments, the electrophysiologic catheter may be advanced through a guiding sheath to facilitate positioning the electrodes at a desired position within the patient. Notably, the positioning of the electrophysiologic catheter within a guiding sheath may block one or more electrodes or location sensor of the catheter depending on the relative longitudinal positioning of the catheter within the guiding sheath, hindering visualization or otherwise reducing the effectiveness of recording or delivering electrical signals. As such, one or more of the electrodes and/or location sensors may also be formed from a coil of wire wound around the elongated body of the guiding sheath. Deploying electrodes and/or location sensors on the guiding sheath permits their use regardless of the relative position of the catheter.

To provide a context for the disclosure, an exemplary catheter having a lasso-shaped electrode assembly coaxially disposed within a guiding sheath is shown schematically in <FIG>. As will be appreciated, the techniques of this disclosure may be applied to any other catheter configurations having one or more electrodes and/or location sensors. Electrophysiologic catheter <NUM> comprises an elongated body <NUM> having proximal and distal ends, with control handle <NUM> at the proximal end of the catheter body and lasso electrode assembly <NUM> at the distal end. Lasso electrode assembly <NUM> may form a generally known or range-restricted angle that is substantially transverse to the longitudinal axis of elongated body <NUM>.

Lasso electrode assembly <NUM> may be of a known fixed length, and comprises material that preferably is twistable but not stretchable when subjected to typical forces. In one aspect, lasso electrode assembly <NUM> may be sufficiently resilient so as to assume a predetermined, curved form, when no force is applied thereto, and to be deflected from the predetermined curved form when a force is applied thereto. For example, lasso electrode assembly <NUM> may have an elasticity that is generally constant over at least a portion of its length, for example, because of internal reinforcement of the curved section with a resilient longitudinal member, such as a shape memory material (e.g. a nickel-titanium alloy) as is known in the art. Lasso electrode assembly <NUM> may form a complete or partial lasso, i.e., as a preformed arcuate structure, which typically subtends between <NUM>° and <NUM>°. In one aspect, lasso electrode assembly <NUM> may form a substantially complete circle so as to allow mapping and/or ablation around or substantially around the circumference of a vessel. The radius of curvature of lasso electrode assembly <NUM>, when unconstrained, may be typically between <NUM> and <NUM>. Because the arc structure is resilient and, possibly, slightly helical, when lasso electrode assembly <NUM> is positioned in the heart (against the ostium of pulmonary vein <NUM>, for example),it will press against the heart tissue over the entire length of the arc, thus facilitating good tissue contact.

Lasso electrode assembly <NUM> may have one or more electrodes <NUM>, configured as ring electrodes, and one or more location sensors <NUM>. Conventionally, ring electrodes are rings formed from a suitable material, such as platinum or iridium, and positioned at various intervals along the length of a distal portion of elongated body <NUM>. The ring electrodes are electrically connected, via electrode lead wires which extend through a lumen in the catheter, to electrical instruments, e.g., a monitor, stimulator or source of energy, e.g., RF energy, for ablation. Such conventional ring electrodes are connected to their lead wire by drawing the wire out of a lumen through an exit hole that extends from the lumen to the side surface of the catheter body. As noted above, the distal end of the electrode lead wire may be stripped of any nonconductive coating or insulation and then welded or soldered onto the inner surface of a ring electrode. The ring electrode is then slipped over the tip shaft to a position directly over the exit hole while drawing the electrode lead wire back into the lumen. The ring electrode is then secured in place, e.g., by swaging or by the application of an appropriate adhesive. A resin, e.g., polyurethane resin, is often applied to the margins or edges of the ring electrode to assure a smooth transition between the outer circumferential surface of the ring electrode and the outer circumferential surface of the catheter shaft. In contrast, one or more of electrodes <NUM> and location sensors <NUM> may be formed from a continuous length of wire extending from a proximal end and helically wrapped to form a coil around a distal portion of elongated body <NUM> as described in further detail below.

Further, <FIG> depicts electrophysiologic catheter <NUM> advanced coaxially within a deflectable guiding sheath <NUM>, having a control handle <NUM> and an elongated body <NUM> with at least one inner lumen <NUM> sized to accommodate elongated body <NUM> of catheter <NUM>. Guiding sheath <NUM> may also have one or more electrodes <NUM> and/or location sensors <NUM>. In this embodiment, elongated body <NUM> of guiding sheath <NUM> may be deflectable to impart control over the advancement of guiding sheath <NUM> through the vasculature of the patient and/or to help control which areas of the patient's anatomy are contacted by lasso electrode assembly <NUM>. At least one puller wire <NUM> may be secured at its distal end to an anchor within elongated body <NUM> at a distal portion of guiding sheath <NUM> and at its proximal end to actuator <NUM> on control handle <NUM>. Rotating, or otherwise manipulating actuator <NUM> may place puller wire <NUM> under tension, producing a deflection of elongated body <NUM> away from its longitudinal axis. One puller wire may be employed to impart a uni-directional deflection, while an additional puller wire may provide bi-directional deflection. Further details regarding deflectable guiding sheaths may be found in <CIT>, entitled "Deflecting Guide Catheter For Use In A Minimally Invasive Medical Procedure For The Treatment Of Mitral Valve Regurgitation". In other embodiments, electrophysiologic catheter <NUM> may also be deflectable. Examples of suitable construction details for deflectable catheters for are described in <CIT>, entitled "Steering Mechanism For Bi-Directional Catheter," and <CIT>, entitled "Catheter With Adjustable Deflection Sensitivity". Other suitable techniques may also be employed to provide deflection as desired.

According to the techniques of this disclosure, the need to use a separate metallic component to form the ring electrode may be avoided. As schematically shown in <FIG>, ring electrodes <NUM> and/or location sensors <NUM> may be constructed from a helical coil <NUM> of a suitable length of lead wire <NUM>. Lead wire <NUM> may be made of any suitable electrically conductive material, such as a non-oxidizing metal and may have any suitable diameter. In one embodiment, lead wire <NUM> may be <NUM> inch (approx. <NUM>) MONEL® <NUM> wire, a high tensile strength nickel-copper alloy coated with a nonconductive coating. Notably, these techniques allow electrode <NUM> and/or location sensor <NUM>, as well as the associated lead wire <NUM>, to be formed from a single, continuous length of wire so that no separate electrical connection, such as a weld or solder joint, between the component and lead wire is necessary, facilitating manufacture and improving reliability.

Initially, lead wire <NUM> may be routed through lumen <NUM> of elongated body <NUM> with respect to electrophysiologic catheter <NUM> as shown in <FIG> and in the corresponding cross sectional view of <FIG>. These techniques may also be applied with respect to elongated body <NUM> of guiding sheath <NUM>. As will be appreciated, lead wire <NUM> may extend proximally through the length of elongated body <NUM> to control handle <NUM>, where a suitable coupling may be provided to create connection to the appropriate equipment to receive or transmit electrical signals. A distal length of lead wire <NUM> is pulled to extend from opening <NUM> in the side wall of elongated body <NUM> that communicates with lumen <NUM>. The distal length of lead wire <NUM> may be of sufficient length to form a desired number of wraps around elongated body <NUM> as depicted in <FIG>. Opening <NUM> may be formed, for example, by inserting a needle through the wall of elongated body <NUM> and heating the needle sufficiently to form a permanent hole. Opening <NUM> may be sufficiently large to enable lead wire <NUM> to be pulled through, such as by a microhook or the like, and yet sufficiently small to be easily sealed. In some embodiments, opening <NUM> may be filled with a suitable material, such as a polyurethane resin, to seal elongated body <NUM>.

The number of wraps may be selected to form coil <NUM> with properties as warranted to function as an electrode <NUM> or as a location sensor <NUM> according to the description below. Notably, to form electrode <NUM>, any insulation may be stripped from the distal portion of lead wire <NUM> so that adjacent turns are electrically coupled. Alternatively, the insulation may be left intact when forming location sensor <NUM>, so that coil <NUM> may generate or respond to a magnetic field for use in an impedance-based positioning system as described below. As indicated in <FIG>, the wraps of lead wire <NUM> may be tightened to remove any slack and to cause the turns to abut each other, thereby completing coil <NUM>. As desired, an area of elongated body <NUM> may be heated to a temperature sufficient to soften the material, so that further tightening of lead wire <NUM> may help embed the wire in the side wall of catheter body <NUM>.

As noted, the number of wraps used in coil <NUM> may be tailored to provide either an electrode <NUM> or a location sensor <NUM> having desired properties. For example, the number of wraps of lead wire <NUM> used to form coil <NUM> having sufficient surface area when functioning as electrode <NUM>. In one embodiment, longitudinal length of coil <NUM> may be in the range of approximately <NUM> to <NUM> and it will be appreciated that the number of wraps depends at least in part on the diameter of lead wire <NUM>. The desired characteristics of coil <NUM> may also be adjusted depending on whether the resulting electrode <NUM> is intended to function as a diagnostic electrode for measuring electrical signals, to function as an ablation electrode for delivering energy, or to function as both. Any suitable number of electrodes <NUM> may be formed by separate coils <NUM>, and they may be distributed in a desired position along the length of elongated body <NUM>. Further, electrodes <NUM> may be configured as electrode pairs to function as bipolar electrodes, such that they may be constructed from two coils <NUM>. Therefore, by following the techniques of this disclosure, coil <NUM> may be formed as electrode <NUM> in a manner that permits opening <NUM> to be sealed and its integrity confirmed as compared to conventional methods for mounting ring electrodes, which require the lead wire to be drawn back into the lumen the ring electrode is position, preventing sealing and inspection of the opening. Further, since coil <NUM> is formed from separate wraps of lead wire <NUM>, it may accommodate bends and other deformations in elongated body <NUM> more readily than a conventional monolithic ring electrode. Alternatively or in addition, one or more electrodes <NUM> may be formed from coils <NUM> around elongated body <NUM> of guiding sheath <NUM>.

Similarly, a suitable number of wraps may be formed when coil <NUM> is intended to function as location sensor <NUM>. As will be appreciated, coil <NUM> may be used with a system for generating three-dimensional position information regarding catheter. For example, coil <NUM> may be configured to generate electrical signals in response to an externally applied magnetic field, such as by responding to specific frequency of the field. Exemplary details regarding certain embodiments of location sensors <NUM> may be found in commonly-assigned <CIT>, entitled "Catheter With Single Axial Sensors". As with electrodes <NUM>, one or more location sensors <NUM> formed from coils <NUM> may be positioned as desired on elongated body <NUM> of catheter <NUM>, on elongated body <NUM> of guiding sheath <NUM>, or both.

The elongated body <NUM> is flexible, i.e., bendable, but substantially non-compressible along its length. The elongated body <NUM> can be of any suitable construction and made of any suitable material. One construction comprises an outer wall made of polyurethane or PEBAX® (polyether block amide). The outer wall comprises an imbedded braided mesh of stainless steel or the like to increase torsional stiffness of the elongated body <NUM> so that, when the control handle <NUM> is rotated, the distal end of the elongated body will rotate in a corresponding manner. In other embodiments, an inner stiffening tube may be coaxially disposed within a lumen of elongated body <NUM>, forming an annular lumen <NUM> through which lead wires <NUM> for electrodes <NUM> and/or location sensors <NUM> may be routed. In some embodiments, elongated body <NUM> may be steerable and/or deflectable using any suitable technique, which are known to those of ordinary skill in the art. The outer diameter of the elongated body <NUM> is not critical, but generally should be as small as possible and may be no more than about <NUM> french depending on the desired application. For example, for use in the mapping and ablation for isolation of a pulmonary vein, elongated body may have an outer diameter of about <NUM> to <NUM> french. Likewise the thickness of the outer wall is not critical, but may be thin enough so that the central lumen can accommodate lead wires <NUM> and any other necessary components. If desired, the inner surface of the outer wall is lined with a stiffening tube (not shown) to provide improved torsional stability. An example of a elongated body construction suitable for use in connection with the present invention is described and depicted in <CIT>.

In one aspect, an electrophysiologist may introduce guiding sheath <NUM>, a guidewire and a dilator into the patient, as is generally known in the art. As an example, guiding sheath <NUM> may be similar to a PREFACE™ Braided Guiding Sheath (commercially available from Biosense Webster, Inc. , Diamond Bar, CA). The guidewire is inserted, the dilator is removed, and catheter <NUM> is introduced through the guiding sheath <NUM>. In one exemplary procedure as depicted in <FIG>, the catheter <NUM> is first introduced through guiding sheath <NUM> to the patient's heart (H) through the right atrium (RA) via the inferior vena cava (IVC), where it passes through the septum (S) in order to reach the left atrium (LA). Depending on how far catheter <NUM> is advanced through guiding sheath <NUM>, electrodes and/or location sensors on elongated body <NUM> may be blocked by guiding sheath <NUM>. Correspondingly, providing one or more electrodes and/or location sensors on elongated body <NUM> of guiding sheath <NUM> may permit their use regardless of the relative positioning of catheter <NUM>. In one aspect, this may facilitate visualization of guiding sheath <NUM> within the patient before catheter has been fully advanced.

As will be appreciated, lasso electrode assembly <NUM> may be deflected into a straightened configuration and constrained within guiding sheath <NUM> to allow catheter <NUM> to be passed through the patient's vasculature to the desired location. Once the distal end of the catheter reaches the desired location, e.g., the left atrium, guiding sheath <NUM> is withdrawn to expose the lasso electrode assembly <NUM>, where it recoils into its arcuate configuration. With the lasso electrode assembly <NUM> then positioned in the ostium of a pulmonary vein (PV), electrodes <NUM> contact the ostial tissue and may be used to map electrical signals in this area. In other embodiment, different electrode configuration may be used to access other areas of a patient's anatomy as desired.

To help illustrate use of catheter <NUM> and guiding sheath <NUM>, <FIG> is a schematic depiction of an invasive medical procedure, according to an embodiment of the present invention. Catheter <NUM>, with the lasso electrode assembly <NUM> (not shown in this view) at the distal end and/or guiding sheath <NUM> may have a connector <NUM> at the proximal end for coupling the lead wires <NUM> and/or others from their respective electrodes <NUM> formed from coils <NUM> (not shown in this view) to a console <NUM> for recording and analyzing the signals they detect as well as for supplying ablating energy. An electrophysiologist <NUM> may insert the catheter <NUM> through guiding sheath <NUM> into a patient <NUM> in order to acquire electropotential signals from the heart <NUM> of the patient. The electrophysiologist <NUM> uses control handles <NUM> and <NUM> to perform the insertion. Console <NUM> may include a processing unit <NUM> which analyzes the received signals, and which may present results of the analysis on a display <NUM> attached to the console. The results are typically in the form of a map, numerical displays, and/or graphs derived from the signals. Processing unit <NUM> may also control the delivery of energy to one or more electrodes <NUM> for creating one or more lesions.

Further, the processing unit <NUM> may also receive signals from location sensors <NUM> (not shown in this view). As noted, the sensor(s) may each comprise a magnetic-field-responsive coil or a plurality of such coils, each formed by coil <NUM>. Using a plurality of coils enables six-dimensional position and orientation coordinates to be determined. The sensors may therefore generate electrical position signals in response to the magnetic fields from external coils, thereby enabling processor <NUM> to determine the position, (e.g., the location and orientation) of the distal end of catheter <NUM> and/or guiding sheath <NUM> within the heart cavity. The electrophysiologist may then view the position of the lasso electrode assembly <NUM> on an image the patient's heart on the display <NUM>. By way of example, this method of position sensing may be implemented using the CARTO™ system, produced by Biosense Webster Inc. (Diamond Bar, Calif. ) and is described in detail in <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>, in <CIT>, and in <CIT>,<CIT>and <CIT>. As will be appreciated, other location sensing techniques may also be employed. The coordinates of location sensor <NUM> may be determined and, with other known information pertaining to the configuration of lasso electrode assembly <NUM>, used to find the positions of each of the electrodes <NUM>.

Claim 1:
A electrophysiologic device comprising:
an elongated body (<NUM>) having proximal and distal ends and at least one lumen (<NUM>) therethrough;
a first coil (<NUM>) configured as a location sensor (<NUM>) and wound around a side wall of a distal portion of the elongated body, wherein the first coil comprises a plurality of helical wraps of a first continuous wire (<NUM>) that extends to the proximal end of the elongated body through the at least one lumen, wherein the first wire is routed through a first opening (<NUM>) in the side wall of the distal portion of the elongated body, and wherein the first opening communicates with the at least one lumen; and
a second coil (<NUM>) configured as a ring electrode (<NUM>) and wound around the side wall of the distal portion of the elongated body, wherein the second coil comprises a plurality of helical wraps of a second continuous wire (<NUM>) that extends to the proximal end of the elongated body through the at least one lumen, wherein the second wire is routed through a second opening (<NUM>) in the side wall of the distal portion of the elongated body, and wherein the second opening communicates with the at least one lumen.