Patent Description:
Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. Atrial fibrillation is a common sustained cardiac arrhythmia and a major cause of stroke. This condition is perpetuated by reentrant wavelets propagating in an abnormal atrial-tissue substrate. Various approaches have been developed to interrupt wavelets, including surgical or catheter-mediated atriotomy. Prior to treating the condition, one has to first determine the location of the wavelets. Various techniques have been proposed for making such a determination, including the use of catheters with a mapping assembly that is adapted to measure activity within a pulmonary vein, coronary sinus or other tubular structure about the inner circumference of the structure. One such mapping assembly has a distal "lasso" structure comprising a generally circular main region generally transverse and distal to the catheter body, where the tubular structure comprises a non-conductive cover over at least the main region of the mapping assembly. A support member including shape-memory is disposed within at least the circular main region of the mapping assembly. A plurality of electrode pairs, each comprising two ring electrodes, are carried by the generally circular main region of the mapping assembly.

More recently, balloon catheter have been put into use to ablate pulmonary vein ostia. A balloon with electrodes on its outer surface is advanced into the left atrium where the balloon is inflated and positioned to nest in an ostium for simultaneous circumferential tissue contact around the ostium. However, depending on the size of the balloon and the ostium, the balloon can be dislodged from the ostium during an ablation procedure.

Applicants recognized that there is a need to provide a catheter with a distal "lasso" assembly that can serve as a guidewire and support a balloon nesting in an ostium, while also being capable of sensing electrical signals from tissue of a tubular region of the ostium and provide location signals for <NUM>-D mapping. <CIT> describes 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 of the present invention 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. In one embodiment, the magnetic-based sensor assembly includes 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. <CIT> describes a catheter with a variable circular loop responsive to a contraction wire for coiling that is supported by a member having a tapered distal section that transitions from a circular cross-section to a generally rectangular cross-section while maintaining a uniform cross-sectional area along the entire tapered length for improved coiling characteristics. A radially constrictive sleeve prevents separation of the contraction wire from the support member to minimize misshaping of the loop during contraction.

Embodiments of the invention are defined by the dependent claims.

These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. It is understood that selected structures and features have not been shown in certain drawings so as to provide better viewing of the remaining structures and features.

Referring to <FIG> and <FIG>, embodiments disclosed herein include a catheter <NUM> that is configured for use with a balloon catheter <NUM>, including an elongated support shaft <NUM> and a <NUM>-D distal or "lasso" assembly <NUM>. The distal assembly <NUM> carries one or more single axis sensors ("SASes") <NUM> configured to be responsive to external magnetic field generators (not shown) for generating signals representative of location of the distal assembly <NUM>, as well as one or more ring electrodes <NUM> configured sensing electrical signals from tissue. The distal assembly <NUM> includes a preformed support member <NUM> with shape-memory, e.g., a nitinol wire, which provides the <NUM>-D or loop configuration of the distal assembly <NUM>. In that regard, it is understood that describing the distal assembly <NUM> the shape-memory elongated support member <NUM> includes portions that impart shape to corresponding sections of the distal assembly <NUM>, including a curved portion 16C that corresponds with a curved section 15C of the distal assembly <NUM>, and an elbow portion 16E proximal of the curved portion 16C that corresponds with an elbow section 15E of the distal assembly <NUM>. In some embodiments, the curved (e.g., circular, helical or loop, all terms used interchangeably herein) portion 16C of the support member <NUM> is generally transverse to the shaft <NUM> that defines a longitudinal axis L of the catheter, and the curved portion 16C has a curved arc or length that spans at least <NUM> degrees, if not about <NUM> degrees with a distal overlapping tail portion 16T. Moreover, the curved portion 16C is configured relative to the shaft <NUM> such that the longitudinal axis L defined by the shaft <NUM> intersects the curved portion 16C and is offset from a center of a circle generally defined by curved portion 16C.

The elongated support shaft <NUM> of the catheter has a proximal section 12P of lesser flexibility and a distal section 12D of greater flexibility. The shaft <NUM> is configured to pass through a lumen of a balloon catheter <NUM> and aptly support the balloon <NUM> in an ostium <NUM> of a pulmonary vein <NUM>, as shown in <FIG>, with the distal lasso assembly <NUM> extending into the pulmonary vein for circumferential contact with tubular tissue of the pulmonary vein. Advantageously, the proximal section 12P of the shaft is configured with sufficient rigidity to transmit axial pushability and torque imparted by a user, for example, manipulating a connector handle <NUM> (<FIG>) at a proximal end of the shaft <NUM> and a torquer <NUM> (<FIG>) mounted on the proximal section 12P, while the distal section 12D of the shaft is configured with sufficient flexibility to accommodate an indirect approach angle between the distal lasso assembly <NUM> and the ostium <NUM> in which the supported balloon <NUM> sits.

In some embodiments, as shown in <FIG> and <FIG>, the shape-memory support member <NUM> of the distal assembly <NUM> has an elongated form with a sufficient length to extend through the entirety of the distal assembly <NUM> and the shaft <NUM> combined. As such, the elongated support member <NUM> includes the following:.

where diameter D1 > diameter D2 > diameter D3 such that the proximal portion 16P has the least flexibility, the distal portion 16D has more flexibility and the distal curved portion 16C has the greatest flexibility. In some embodiments, the diameter D1 is about <NUM> (<NUM> inch), the diameter D2 ranges from about <NUM> (<NUM> inch) to <NUM> (<NUM> inch) and the diameter D3 is about <NUM> (<NUM> inch). Between the proximal portion 16P and the distal portion 16D, the diameter of the wire <NUM> may have a step transition or a gradual transition between the diameters D1 and D2, as needed or appropriate. Between the distal portion 16D and the curved portion 16C, the elbow portion 16E is configured with a gradual transition between the diameters D2 and D3. In some embodiments, the gradual transition between diameters D2 and D3 occurs in a span of about <NUM> in the elbow portion 16E. The length of the proximal portion 16P of the support member <NUM> is not critical. However, in some embodiments, the length of the distal portion 16D is at least the longitudinal length of the balloon <NUM> so it can accommodate the balloon when it is supporting the balloon. In some embodiments, the length of the shaft <NUM> is about <NUM> meters, where the distal portion 12D (with the greater flexibility relative to the proximal portion 12P) has a length ranging between about <NUM> and <NUM>.

With reference to <FIG> and <FIG>, the distal curved portion 16C of the shape-memory support member <NUM> carries one or more SASes. It is understood that each SAS <NUM> has a respective wire coil sensor <NUM> and a cable <NUM>, where the wire coil sensor <NUM> is wrapped around a selected location on the distal curved portion 16C and the cable <NUM> includes a dedicated pair of wires <NUM>, <NUM>' that are encased along with shielding fibers <NUM> within an insulating sheath <NUM> generally coextensive with the wires <NUM>, <NUM>'. For simplicity in the description provided herein, wires <NUM>, <NUM>' of all SASes <NUM> carried on the distal assembly <NUM> are illustrated herein as passing through one common insulating sheath <NUM> with shared shielding fibers <NUM> in forming a single cable <NUM> for all SASes <NUM>.

In the illustrated embodiment of <FIG>, the distal assembly <NUM> carries three SASes, namely, proximal SAS 13A, middle SAS 13B and distal SAS 13C, including three wire coils 50A, 50B and 50C, referred to herein respectively as the proximal coil, the mid coil and the distal coil, that are arranged in equi-angular positions about the curved portion 16C, e.g., at about <NUM>, <NUM> and <NUM> degrees. The wire coil <NUM> of each SAS is connected to a dedicated pair of wires <NUM> and <NUM>', with the wire <NUM> connected to a distal end of the wire coil <NUM> and the wire <NUM>' connected to a proximal end of the wire coil <NUM>. Thus, in the illustrated embodiment, the distal coil 50C (best shown in <FIG>) is connected to wire pair 21C and 21C', the mid coil 50B is connected to wire pair 21B and 21B' and the proximal coil 50A is connected to wire pair 21A and 21A'. To assemble the SASes 13A, 13B and 13C on the curved portion 16C of the preformed support member <NUM>, a method making or assembling a preformed support member with SASes in some embodiments includes (i) wrapping the wire coil 50C on the preformed support member <NUM> at location <NUM> degrees to form SAS 13C, (ii) connecting the wire pair 21C and 21C' to the distal and proximal ends, respectively, of the wire coil 50C, and (iii) wrapping the wire pair 21C and 21C' around the curved portion 16C in a proximal direction. Different wrapping patterns may be employed to provide strain relief against wire breakage during use of the catheter.

The method of assembling also includes (iv) wrapping the wire pair 21C and 21C' at location <NUM> degrees, (v) wrapping the wire coil 50B over the wrapped wire pair 21C and 21C' to form SAS 13B, (vi) connecting the wire pair 21B and 21B' to the distal and proximal ends, respectively, of the wire coil 50B, and (vi) wrapping the wire pairs 21C and 21C' and 21B and 21B' around the curved portion 16D in a proximal direction.

The method of assembling further includes (vii) wrapping the wire pairs 21C and 21C' and 21B and 21B' at location <NUM> degrees, (viii) wrapping the wire coil 50A over the wrapped wire pairs 21C and 21C' and 21B and 21B' to form SAS 13A, (ix) connecting the wire pair 21A and 21A' to the distal and proximal ends, respectively, of the wire coil 50A, and (x) wrapping the wire pairs 21C and 21C', 21B and 21B', and 21A and 21A' around the curved portion 16C in a proximal direction. It is understood that one or more heat shrink sleeves may be over the formed SASes and the wrapped wire pairs between adjacent SASes.

It is also understood that the sequence of the actions recited above or the direction of wrapping (e.g., distal to proximal or proximal to distal) may be varied, as desired or appropriate and that a heat shrink sleeve can be placed over each SAS, the wire coils or wrapped wire pair(s) beneath the wire coils, as desired or appropriate. In any case, the distal SAS 13C includes the wire coil 50C with its distal end connected to the wire 21C and its proximal end connected to the wire 21C', the mid SAS 13B includes the wire coil 50B with its distal end connected to the wire 21B and its proximal end connected to the wire 21B', where the wire coil 50B is coiled over the wires 21C and 21C', and the proximal SAS 13A includes the wire coil 50A with its distal end connected to the wire 21A and its proximal end connected to the wire 21A', where the wire coil 50A is coiled over the wires 21C and 21C' and 21B and 21B'.

At the elbow portion 16E, the cable <NUM> housing the wire pairs <NUM> (e.g., 21A, 21A', 21B, 21B', 21C and 21C') advantageously lies on an inside surface <NUM> (inward facing toward the curvature) of the elbow portion 16E in minimizing the outer diameter of the distal assembly <NUM> in that region, as better shown in <FIG>, <FIG>. In that regard, the distal end of the insulating sheath <NUM> of the cable <NUM>, and the shielding fibers <NUM> therein are cut or otherwise terminated proximal of the elbow portion 16E to expose the various wire pairs <NUM>. Moreover, all of the wires <NUM> are spread or fanned out, laid against the inside surface <NUM>, and affixed by an adhesive <NUM> (<FIG>) to minimize the circumferential size and profile of the distal assembly <NUM> at its elbow portion 15E. The distal end portions of the shield fibers <NUM> may be wrapped around the wires <NUM> and the preformed support member <NUM> (<FIG>) to encircle them for a tighter profile around the preformed support member <NUM>. A heat shrink sleeve <NUM> may extend over the cable <NUM> and the shielding fibers <NUM> proximal of the elbow portion 16E, and the exposed wires <NUM> and safety fibers <NUM> in the elbow portion 16E. Proximal and terminal ends of the heat shrink sleeve may be at any location along the support member <NUM>, as needed or appropriate.

Accordingly, the method of assembling the preformed support member <NUM> with the SASes, includes (i) preparing the cable <NUM> for affixation to an elbow portion 16E; and (ii) affixing the prepared cable to the elbow portion, wherein the preparing the cable includes: (a) cutting or terminating a distal end of the outer insulating sheath <NUM> generally proximal of the elbow portion; (b) exposing the wires <NUM> in the cable; (c) spreading or fanning out the exposed wires <NUM>, and wherein the affixing the prepared cable includes: (a) laying the fanned out exposed wires onto an inside surface <NUM> of the elbow portion; (b) applying adhesive to the fanned out exposed wires <NUM> on the inside surface of the elbow portion; and (c) covering the affixed exposed wires and at least a distal portion of the insulating sheath <NUM> with a heat shrink sleeve. The preparing the cable may also include cutting or terminating distal ends of the shielding fibers <NUM>, and wrapping the distal ends around the exposed wires <NUM> and the preformed support member <NUM>. The affixing the prepared cable may also include covering a plurality of safety strands <NUM> (e.g., VECTRAN strands) whose proximal ends are anchored to the shaft <NUM> and whose lengths are coextensive with the wires <NUM> under the heat shrink sleeve <NUM> to tether the distal assembly <NUM> to the shaft <NUM> as a safety measure against detachment of the distal assembly <NUM>. Distal ends of the safety strands <NUM> may be anchored to a distal end of the preformed support member <NUM>. A description of suitable SASes is provided in <CIT>, the entire content of which is hereby incorporated by reference.

As previously mentioned, the distal assembly <NUM> not only carries one or more SASes <NUM>, it also carries one or more ring electrodes <NUM>. As shown in <FIG>, the distal assembly <NUM> includes an outer braided tubing <NUM> that has the ring electrodes <NUM> and conductive lead wires <NUM>. Although the tubing <NUM> has a lumen <NUM>, the conductive wires <NUM> are embedded in the side wall <NUM> as part of an extrusion manufacturing process of the tubing <NUM>, as understood by one or ordinary skill in the art. In some embodiments, the outer braided tubing <NUM> covers the entire length of the preformed support structure <NUM>, including the proximal portion 16P, the distal portion 16D, the elbow portion 16E, and the curved portion 16C. Of the portion of the braided tubing <NUM> that covers the curved portion 16C, the ring electrodes <NUM> carried thereon are formed by selective removal, e.g., laser cutting, of the outer side wall <NUM> to form recesses <NUM> at predetermined locations so as to expose selected individual wires <NUM>. Conductive epoxy <NUM>, for example, platinum conductive epoxy or gold conductive epoxy, is then applied to fill the recesses <NUM> and also along the circumference at the recess around the exterior of the side wall <NUM> to form a respective ring electrode <NUM> at each of the predetermined locations. Thus, a method of constructing an outer tubing <NUM> with ring electrodes <NUM> and embedded lead wires <NUM> includes: (i) extruding a tubing <NUM> with wires <NUM> embedded in side wall <NUM>, where the tubing has an exterior surface, and an interior surface defining a lumen; (ii) removing a portion of the side wall from the exterior surface to expose a wire <NUM> within a recess; (iii) applying conductive epoxy to fill the recess and a corresponding circumferential band around the recess to form a ring electrode <NUM>. Extruding the tubing <NUM> with the wires <NUM> may be accomplished with conventional wire extrusion machines. Braided wires <NUM> embedded in the side wall <NUM> of the tubing <NUM> may extend distal of their respective ring electrodes without any adverse impact on the function of the ring electrodes.

After the outer tubing <NUM> has been constructed with the ring electrodes <NUM> and the embedded wires <NUM>, the outer tubing <NUM> can be slipped on over the assembled distal assembly <NUM>. In some embodiments, a method of assembling includes: (i) the above-described method of making or constructing the outer tubing <NUM> with the ring electrodes <NUM> and embedded wires <NUM>; (ii) the above-described method of assembling the preformed support member <NUM> with the SASes <NUM>; and (iii) mounting the constructed outer tubing <NUM> onto the preformed support member <NUM> with the SASes <NUM>. Mounting may be accomplished by inserting the assembled preformed support member <NUM> into the lumen <NUM> of the constructed outer tubing <NUM>. As such, the construction of the catheter <NUM> is simplified by compartmentalization into construction of the outer tubing <NUM> which provides the ring electrodes, and construction of the underlying SAS-carrying support member <NUM>. Distal ends of the outer tubing <NUM> and the support structure <NUM> may be jointly plugged and sealed with a ball of sealant, e.g., polyurethane, to form an atraumatic bulbous distal end of the catheter <NUM>.

At the proximal end of the outer tubing <NUM> terminating near or in the connector handle <NUM>, proximal portions of the wires <NUM> may be exposed from the tubing <NUM> by selective removal of the side wall <NUM> for connection to suitable electrical terminals in the connector handle <NUM> in the transmission of sensed electrical signals to an electrophysiology workstation for processing, as known in the art. The cable <NUM> (including the wire pairs <NUM>, <NUM>' of each SAS carried on the distal assembly <NUM>) extends through the lumen <NUM> of the outer tubing <NUM>, coextensively with the distal and proximal portions 16D and 16P of the support member <NUM>, in passing through the shaft <NUM> of the catheter and into the connector handle <NUM> in the transmission of location signals to the electrophysiology workstation for processing, as known in the art.

In alternate embodiments, a shorter support member <NUM> is without the proximal portion 16P and has a proximal end that terminates at a suitable location proximal of the distal portion 16D and the elbow portion 16E. As shown in <FIG>, the shorter support member <NUM> has a proximal end 16PE at, for example, about <NUM> proximal of the elbow portion 16E and is connected via a lumened coupler <NUM> to a second support member <NUM>, e.g., a metal or stainless steel wire, that extends proximally toward the connector handle <NUM>, where the <NUM> is selected on the basis of the longitudinal length of the balloon <NUM> that is supported on the distal linear portion 12D of the shaft <NUM> when the distal assembly <NUM> is inside the tubular region <NUM> of the ostium <NUM> on which the distal surface of the balloon rests (<FIG>). The outer tubing <NUM> with the ring electrodes <NUM> and embedded wires <NUM> extends over the support member <NUM> and the second support member <NUM>, so as to cover the entirety of the distal assembly <NUM> and the shaft <NUM>. The SAS cable <NUM> extends in the lumen <NUM> of the tubing <NUM> coextensively with the support member <NUM> in the distal shaft portion 12D and with the second support member <NUM> in the proximal shaft portion 12P, and may be outside of the coupler <NUM>. To provide the different flexibilities in the shaft <NUM> and the distal assembly <NUM>, the second support member <NUM> has the diameter D1, the distal portion 16D of the support member <NUM> has the diameter D2, and the curved portion 16C of the support member <NUM> has the diameter D3, where D1 > D2 >D3 such that the second support member <NUM> has the least flexibility, the distal portion 16D has greater flexibility, and the curved portion 16C has the most flexibility. Again, the elbow portion 16E provides a gradual transition of diameter from D2 to D3, but there may be a step transition between the diameters D1 of the second support member <NUM> and D2 of the distal portion 16D at the coupler <NUM>.

In other alternate embodiments, as shown in <FIG>, the shorter support member <NUM> (without the proximal portion 16P) has a proximal end that is received in a distal end of a lumened structure, e.g., a hypotube <NUM> with lumen <NUM>, that extends proximally toward the connector handle <NUM>. The shorter support member <NUM> extends through an outer covering <NUM>, e.g., of PELLETHANE, whose lumen <NUM> receives the SAS-carrying curved portion 16C and the distal portion 16D, and whose proximal end 32P abuts with a distal end 18D of the hypotube <NUM>. As understood by one of ordinary skill in the art, conductive bands <NUM> are mounted over the outer covering <NUM> to form the ring electrodes <NUM> on the distal assembly <NUM>. Lead wires <NUM> connected to respective conductive bands <NUM> pass into the lumen <NUM> via through-holes <NUM> formed in side wall <NUM> of the outer covering <NUM>. Inside the lumen <NUM>, the lead wires <NUM>, along with the cable <NUM> for the SASes in the distal assembly <NUM>, extend proximally and pass through the lumen <NUM> of the hypotube <NUM> toward the connector handle <NUM>. In some embodiments, the hypotube <NUM> has an outer diameter ranging from about <NUM> (<NUM> inch) to <NUM> (<NUM> inch). As shown in <FIG>, a distal portion of the hyptube <NUM> may be configured with one or more spiral cuts <NUM> to increase flexibility.

In use, the catheter <NUM> is fed into and through a lumen <NUM> of the balloon catheter <NUM>, where the lumen <NUM> extends through a shaft <NUM> of the balloon catheter and the balloon <NUM> itself. To feed the distal assembly <NUM>, it is straightened so that the curved portion 15C first enters the lumen <NUM> followed by the elbow 15E, and so forth. The distal assembly <NUM> is advanced relative to the balloon catheter until the distal assembly <NUM> passes the distal end of the balloon catheter, upon which the distal assembly <NUM> is free to assume the <NUM>-D shape in the patient's left atrium pursuant to its underlying preformed shape-memory support member <NUM>. The catheter <NUM> is then maneuvered so as to insert the distal assembly <NUM> into a pulmonary vein where the ring electrodes <NUM> are in contact with tissue along an inner circumference of tubular region of the pulmonary vein. Using the shaft <NUM> and particularly the distal section 12D as a guidewire, the balloon catheter <NUM> is then advanced toward the ostium of the pulmonary vein until a distal surface of the balloon comes into contact with the ostium. The shaft <NUM> of the catheter <NUM> has a less flexible proximal section 12P so as to function as a guidewire for the balloon catheter <NUM> and a more flexible distal section 12D so as to allow flexure where the approach angle of the distal assembly <NUM> is not in alignment with the center of the ostium, yet have sufficient rigidity to aptly support the balloon thereon. The one or more SASes <NUM> in the distal assembly <NUM> respond to external magnetic field generators typically located under the patient's bed to provide location signals, and the ring electrodes <NUM> carried on the distal assembly <NUM> sense electrical signals from the tissue of the pulmonary vein, including electrical signals to assess whether PV isolation has been achieved by ablation of tissue of or adjacent the ostium.

Claim 1:
An electrophysiology catheter (<NUM>), comprising:
an elongated shaft (<NUM>) defining a longitudinal axis (L) of the catheter, the shaft (<NUM>) including a proximal portion (12P) with a first flexibility and a distal portion (12D) including a second flexibility greater than the first flexibility;
a distal assembly (<NUM>) including an elbow portion (15E) and a generally circular portion (15C) generally transverse to the longitudinal axis (L), the generally circular portion (15C) including a third flexibility greater than the second flexibility;
a single axis sensor (<NUM>) situated in the generally circular portion (15C);
a ring electrode (<NUM>) situated on the generally circular portion (15C); and
an elongated support member (<NUM>) with shape memory, the elongated support member (<NUM>) being coextensive with the distal portion (12D) of the shaft (<NUM>) and with the distal assembly (<NUM>);
wherein the elongated support member (16E) coextensive with the elbow portion (15E) of the distal assembly (<NUM>) includes a transition portion having a distal end with a smaller diameter and a proximal end with a larger diameter;
characterized in that the transition portion tapers from the proximal end with the larger diameter to the distal end with the smaller diameter.