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.

In use, the electrode catheter is inserted into a major vein or artery, e.g., femoral artery, and then guided into the chamber of the heart which is of concern. Once the catheter is positioned within the heart, the location of aberrant electrical activity within the heart is then located.

One location technique involves an electrophysiological mapping procedure whereby the electrical signals emanating from the conductive endocardial tissues are systematically monitored and a map is created of those signals. By analyzing that map, the physician can identify the interfering electrical pathway. A conventional method for mapping the electrical signals from conductive heart tissue is to percutaneously introduce an electrophysiology catheter (electrode catheter) having mapping electrodes mounted on its distal extremity. The catheter is maneuvered to place these electrodes in contact with the endocardium. By monitoring the electrical signals at the endocardium, aberrant conductive tissue sites responsible for the arrhythmia can be pinpointed.

For sensing by ring electrodes mounted on a catheter, lead wires transmitting signals from the ring electrodes are electrically connected to a suitable connector in the distal end of the catheter control handle, which is electrically connected to an ECG monitoring system and/or a suitable <NUM>-D electrophysiology (EP) mapping system, for example, CARTO, CARTO XP or CARTO <NUM>, available from Biosense Webster, Inc. of Irwindale, California.

The closely-spaced electrode pairs allow for more accurate detection of near-field potentials versus far-field signals, which can be very important when trying to treat specific areas of the heart. For example, near-field pulmonary vein potentials are very small signals whereas the atria, located very close to the pulmonary vein, provides much larger signals. Accordingly, even when the catheter is placed in the region of a pulmonary vein, it can be difficult for the electrophysiologist to determine whether the signal is a small, close potential (from the pulmonary vein) or a larger, farther potential (from the atria). Closely-spaced bipoles permit the physician to more accurately remove far field signals and obtain a more accurate reading of electrical activity in the local tissue. Accordingly, by having closely-spaced electrodes, one is able to target exactly the locations of myocardial tissue that have pulmonary vein potentials and therefore allows the clinician to deliver therapy to the specific tissue. Moreover, the closely-spaced electrodes allow the physician to determine the exact anatomical location of the ostium/ostia by the electrical signal.

However, manufacturing and assembling catheters with closely and precisely spaced ring electrodes pose many challenges. Accuracy and consistency in spacing between adjacent electrodes become critical to catheter manufacturing and assembly. Conventional methods often use adhesives such as polyurethane to seal each ring electrode, which creates a margin between adjacent electrode or electrode pairs that can limit how closely the electrodes can be spaced from each other. Typically, spacing of <NUM> or larger between electrode pairs can be achieved using such conventional methods. However, spacing smaller, especially <NUM> or <NUM> spacing is difficult to achieve. With such smaller spacing, there is the risk of adjacent electrodes coming in contact due to electrode tolerance specification or shifting of electrodes during assembly when medical grade adhesive such as Polyurethane is applied or when medical epoxy is curing.

Moreover, the conventional methods of attaching a lead wire to a ring electrode also typically require spacing tolerances between adjacent ring electrodes. Such attachment methods often result in an acute angle at which the lead wire must extend to reach the ring electrode which can cause stress leading to detachment or breakage.

Flexible electronics, also known as flex circuits, is a technology for assembling electronic circuits by mounting electronic devices on flexible plastic substrates, such as polyimide, PEEK or transparent conductive polyester film. Additionally, flex circuits can be screen printed silver circuits on polyester. Flexible printed circuits (FPC) are made with a photolithographic technology. An alternative way of making flexible foil circuits or flexible flat cables (FFCs) is laminating very thin (<NUM>) copper strips in between two layers of PET. These PET layers, typically <NUM> thick, are coated with an adhesive which is thermosetting, and will be activated during the lamination process. Single-sided flexible circuits have a single conductor layer made of either a metal or conductive (metal filled) polymer on a flexible dielectric film. Component termination features are accessible only from one side. Holes may be formed in the base film to allow component leads to pass through for interconnection, normally by soldering.

Accordingly, a need exists for an electrophysiological catheter with bipole microelectrode pairs that are very closely spaced to minimize detection of noise and/or far-field signals. There is also a need for a method of manufacture and assembly of such a catheter wherein very close spacing between electrodes can be achieved readily and consistently with improved precision and accuracy.

<CIT> relates to an electrode array catheter, typically used for mapping, pacing and ablation, which includes a flexible delivery sheath and an electrode assembly slidably mounted within the delivery sheath for movement between retracted and deployed positions.

<CIT> relates to a device for insertion into a body lumen.

<CIT> relates to an expandable electrode assembly for use in a cardiac mapping procedure includes multiple bipolar electrode pairs including a first electrode located on an outer surface and a second electrode located on an inner surface of the individual splines forming the expandable electrode assembly.

<CIT> relates to a flexible circuit electrode array with more than one layer of metal traces and polymer layers.

<CIT> relates to a catheter having a distal assembly with multiple spines and bipolar electrodes.

The present invention is directed to an electrophysiologic catheter with a distal electrode assembly carrying very closely-spaced bipole microelectrodes on a plurality of divergent spines that can flexibly spread over tissue surface area for simultaneously detecting signals at multiple locations with minimized detection of undesirable noise, including far-field signals. Specifically, the present invention is an electrophysiological catheter according to claim <NUM>. Further embodiments of the invention are described in the dependent claims.

The catheter of the invention includes an elongated body and a distal electrode assembly having a plurality of spines, with a flexible microelectrode panel on at least one spine. Each spine has a free distal end, and the panel has a substrate conforming to an outer surface of the spine, at least one pair of microelectrodes, a trace for each microelectrode, and a soldering pad for each microelectrode, wherein each trace electrically couples a respective microelectrode and a respective soldering pad.

In some detailed embodiments, adjacent microelectrodes of a bipole pair are separated by a space gap distance of about <NUM> microns or less, including about <NUM> microns or less. In some detailed embodiments, the space gap distance ranges between about <NUM> and <NUM> microns. In some detailed embodiments, the space gap distance is about <NUM> microns.

In some detailed embodiments, each microelectrode has a width of about <NUM> microns, a width of about <NUM> microns, or a width of about <NUM> microns.

In some detailed embodiments, each microelectrode has an enlarged portion configured to cover a trace electrical connection.

In some detailed embodiments, each spine has a circular cross-section.

In some detailed embodiments, each spine has a rectangular cross-section.

In other embodiments, the distal electrode assembly has a plurality of divergent spines, wherein the pair of microelectrodes are at least partially circumferentially wrapped around the spine, and microelectrodes of the pair are separated by a space gap distance ranging between about <NUM>-<NUM> microns.

In detailed embodiments, the spine has a planar surface configured to contact tissue surface, and the pair of microelectrodes are positioned on the planar surface.

In detailed embodiments, the entirety of the pair of microelectrodes is within the planar surface.

In detailed embodiments, each microelectrode has a width ranging between about <NUM>-<NUM> microns.

In additional embodiments, each spine has a preformed inward curvature toward a longitudinal axis of the assembly, wherein the pair of microelectrodes are at least partially circumferentially wrapped around the spine, and microelectrodes of the pair are separated by a space gap distance ranging between about <NUM>-<NUM> microns, <NUM>-<NUM> microns, or <NUM>-<NUM> microns.

In some detailed embodiments, the flexible panel has a longitudinal portion, at least a distal lateral portion, and a proximal base portion, wherein the trace is positioned in the longitudinal portion, the pair of microelectrodes are positioned in the distal lateral portion and the soldering pad is positioned in the distal base portion.

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>, a catheter <NUM> includes a catheter body <NUM>, an intermediate deflection section <NUM>, a distal electrode assembly <NUM>, and a control handle <NUM> proximal of the catheter body <NUM>. The distal electrode assembly <NUM> includes a plurality of spines <NUM>, each spine carrying at least one pair of closely-spaced bipole microelectrodes <NUM>, wherein the microelectrodes of a pair has a separation space gap distance therebetween of no greater than about <NUM> microns.

In some embodiments, the catheter body <NUM> comprises an elongated tubular construction, having a single, axial or central lumen <NUM>, as shown in <FIG>. The catheter body <NUM> is flexible, i.e., bendable, but substantially non-compressible along its length. The catheter body <NUM> can be of any suitable construction and made of any suitable material. A presently preferred construction comprises an outer wall <NUM> made of a polyurethane, or PEBAX. The outer wall <NUM> comprises an imbedded braided mesh of high-strength steel, stainless steel or the like to increase torsional stiffness of the catheter body <NUM> so that, when the control handle <NUM> is rotated, the deflection section <NUM> of the catheter <NUM> will rotate in a corresponding manner.

The outer diameter of the catheter body <NUM> is not critical, but is preferably no more than about <NUM> french (<NUM>), more preferably about <NUM> french (<NUM>). Likewise the thickness of the outer wall <NUM> is not critical, but is thin enough so that the central lumen <NUM> can accommodate components, including, for example, one or more puller wires, electrode lead wires, irrigation tubing, and any other wires and/or cables. The inner surface of the outer wall <NUM> is lined with a stiffening tube <NUM>, which can be made of any suitable material, such as polyimide or nylon. The stiffening tube <NUM>, along with the braided outer wall <NUM>, provides improved torsional stability while at the same time minimizing the wall thickness of the catheter, thus maximizing the diameter of the central lumen <NUM>. The outer diameter of the stiffening tube <NUM> is about the same as or slightly smaller than the inner diameter of the outer wall <NUM>. Polyimide tubing is presently preferred for the stiffening tube <NUM> because it may be very thin walled while still providing very good stiffness. This maximizes the diameter of the central lumen <NUM> without sacrificing strength and stiffness. As would be recognized by one skilled in the art, the catheter body construction can be modified as desired. For example, the stiffening tube can be eliminated.

In some embodiments, the intermediate deflection section comprises a shorter section of tubing <NUM>, which as shown in <FIG>, has multiple lumens, for example, off-axis lumens <NUM>, <NUM>, <NUM> and <NUM> and on axis lumen <NUM>. In some embodiments, the tubing <NUM> is made of a suitable non-toxic material more flexible than the catheter body <NUM>. A suitable material for the tubing <NUM> is braided polyurethane, i.e., polyurethane with an embedded mesh of braided high-strength steel, stainless steel or the like. The outer diameter of the deflection section <NUM> is similar to that of the catheter body <NUM>. The size of the lumens is not critical and can vary depending on the specific application.

Various components extend through the catheter <NUM>. In some embodiments, the components include lead wires <NUM> the distal electrode assembly <NUM>, one or more puller wires 32A and 32B for deflecting the deflection section <NUM>, a cable <NUM> for an electromagnetic position sensor <NUM> housed at or near a distal end of the deflection section <NUM>, and a guidewire tubing <NUM>. These components pass through the central lumen <NUM> of the catheter body <NUM>, as shown in <FIG>.

In the deflection section <NUM>, different components pass through different lumens of the tubing <NUM> as shown in <FIG>. In some embodiments, the lead wires <NUM> pass through first lumen <NUM>, the first puller wire 32A passes through second lumen <NUM>, the guidewire tubing <NUM> passes through third lumen <NUM>, the cable <NUM> passes through fourth lumen <NUM>, and the second puller 34B passes through fifth lumen <NUM>. The second and fourth lumens <NUM> and <NUM> are diametrically opposite of each other to provide bi-directional deflection of the intermediate deflection section <NUM>.

Distal of the deflection section <NUM> is the distal electrode assembly <NUM> which includes a mounting stem <NUM> in the form of a short tubing mounted on a distal end of the tubing <NUM> of the intermediate deflection section <NUM>. (In that regard, it is understood that where the catheter <NUM> is without a deflection section <NUM>, the mounting stem <NUM> is mounted on a distal end of the catheter body <NUM>. ) The stem <NUM> has a central lumen <NUM> to house various components. The intermediate section <NUM> and stem <NUM> are attached by glue or the like. The stem <NUM> may be constructed of any suitable material, including nitinol. As shown in <FIG>, the stem <NUM> houses various components, including the electromagnetic position sensor <NUM>, and a distal anchor for the puller wires 32A and 32B.

In the disclosed embodiment, the distal anchor includes one or more washers, for example, a distal washer 50D and a proximal washer 50P, each of which has a plurality of through-holes that allow passage of components between the deflection section <NUM> and the stem <NUM> while maintaining axial alignment of these components relative to a longitudinal axis <NUM> of the catheter <NUM>. The through-holes include holes <NUM> and <NUM> that are axially aligned with the second and fourth lumens <NUM> and <NUM> of the tubing <NUM>, respectively, to receive a distal end of puller wires 32A and 32B, respectively. It is understood that the puller wires may form a single tensile member with a distal U-bend section that passes through the holes <NUM> and <NUM>. With tension on the washers 50D and 50P exerted by the U-bend section of the puller wires, the washers firmly and fixedly abut against the distal end of the tubing <NUM> of the deflection section <NUM> to distally anchor the U-bend section.

Each washer includes through-hole <NUM> which is axially aligned with the first lumen <NUM> and allows passage of the lead wires <NUM> from the deflection section <NUM> and into the lumen <NUM> of the stem <NUM>. Each washer also includes through-hole <NUM> which is axially aligned with the fifth lumen <NUM> of the tubing <NUM> and allows passage of the sensor cable <NUM> from the deflection section <NUM> into lumen <NUM> of the stem <NUM> where the electromagnetic position sensor <NUM> is housed. Each washer further includes on-axis through-hole <NUM> which is axially aligned with the third lumen <NUM> and allows passage of the guidewire tubing <NUM> from the deflection section <NUM> and into the lumen <NUM> of the stem <NUM>. Marker bands or ring electrodes <NUM> may be carried on the outer surface of the catheter at or near the near the distal end of the intermediate deflection section <NUM>, as known in the art.

As shown in <FIG>, extending from the distal end of the stem <NUM> are elongated spines <NUM> of the distal electrode assembly <NUM>. Each spine has a support member <NUM>, a non-conductive covering <NUM> that extends along the each spine <NUM>. Each spine has a proximal portion that extends proximally into the lumen <NUM> of the stem <NUM>. The non-conductive coverings <NUM> of the spines may also extend proximally into the lumen <NUM>. Each spine <NUM> may be arranged uniformly about the distal opening of the stem <NUM> in equi-radial distance from adjacent spines <NUM>. For example, with five spines, each spine may be spaced apart at about <NUM> degrees from adjacent spines. Suitable adhesive, e.g., polyurethane, may be used to pot and anchor the proximal ends of the spines <NUM> and their nonconductive coverings <NUM>. The suitable adhesive seals the distal end of the stem <NUM>, which is formed to leave open the distal end of the guidewire tubing <NUM>.

Each spine support member <NUM> is made of a material having shape-memory, i.e., that can be temporarily straightened or bent out of its original shape upon exertion of a force and is capable of substantially returning to its original shape in the absence or removal of the force. One suitable material for the support member is a nickel/titanium alloy. Such alloys typically comprise about <NUM>% nickel and <NUM>% titanium, but may comprise from about <NUM>% to about <NUM>% nickel with the balance being titanium. A nickel/titanium alloy is nitinol, which has excellent shape memory, together with ductility, strength, corrosion resistance, electrical resistivity and temperature stability. The non-conductive covering <NUM> can be made of any suitable material, and is preferably made of a biocompatible plastic such as polyurethane or PEBAX.

Lead wires <NUM> for microelectrodes <NUM> carried on the spines <NUM> extend through the catheter body <NUM> and the deflection section <NUM> protected by a nonconductive sheath <NUM>. Toward the distal electrode assembly <NUM>, the lead wires <NUM> extend through a polytube <NUM>, as shown in <FIG>. The lead wires <NUM> diverge at the distal end of the polytube <NUM>, and extend toward their respective spine <NUM>.

As shown in <FIG>, each spine <NUM> includes a flexible microelectrode member in the form of a panel <NUM> that is affixed to the outer surface of spine <NUM>, conforming to the shape of the spine <NUM>. The flexible electrode panel <NUM>, as better shown in <FIG>, includes a biocompatible flexible plastic substrate <NUM> constructed of a suitable material, for example, polyimide or PEEK, at least one pair of close-spaced microelectrodes <NUM>, separated therebetween by a gap space S.

In some embodiments, the substrate <NUM> is generally elongated with a longitudinal (thinner "T") portion <NUM>, at least one distal lateral (wider "W") portion <NUM> traversing the longitudinal portion <NUM> at a generally perpendicular angle, and a proximal (less wide "LW") base portion <NUM> having a slightly greater lateral dimension than the longitudinal portion <NUM> (T, W and LW shown in <FIG>). The longitudinal portion <NUM> is configured to extend along the length of a spine <NUM> and the lateral portion <NUM> is configured to wrap circumferentially around a distal portion of the spine <NUM>. The base portion <NUM> is positioned on a proximal end portion of the spine <NUM> and is thus protected within the lumen <NUM> of the mounting stem <NUM>. On the base portion <NUM> are soldering patches <NUM>, one for each lead wire <NUM> whose distal end is soldered to a respective soldering patch <NUM>. The soldering patches <NUM> are therefore protected and insulated within the lumen <NUM> of the mounting stem <NUM>. It is understood that only one spine member <NUM> is shown in <FIG> for purposes of clarity, and that the polytube <NUM> may be sized appropriately to receive the proximal ends of all spine members <NUM> extending from the tubing <NUM>, where, in some embodiments of the present invention, the plurality of spine members <NUM> may range between about two and eight.

In other embodiment, the most proximal longitudinal portion <NUM> may be significantly elongated such that the base portion <NUM> is located further proximally in the deflection section <NUM>, the catheter body <NUM>, or even in the control handle <NUM>, as appropriate or desired.

On an outer surface of each lateral portion <NUM>, a respective pair of thin, elongated microelectrodes <NUM> (microelectrode strips) are affixed or otherwise provided in alignment with the lateral portion <NUM> so that each microelectrode generally forms a ring microelectrode R (<FIG>) when the lateral portion <NUM> is wrapped circumferentially around the spine <NUM>. It is understood that the longitudinal portion <NUM> may be as wide as the lateral portion <NUM> although the amount of surface area coverage and/or thickness of the substrate affects the flexibility of the spine <NUM>.

In some embodiments, the space gap distance S separating each microelectrode of a pair ranges between about <NUM> and <NUM> microns. In some embodiments, the space gap distance ranges between about <NUM>-<NUM> microns. In some embodiments, the space gap distance is about <NUM> microns. Moreover, in some embodiments, each microelectrode itself may have a width W ranging between about <NUM> -<NUM> microns. At least one pair of closely-spaced bipole microelectrodes <NUM> are provided on each spine <NUM>. In the illustrated embodiment, each spine carries four pairs of bipole pairs for a total of eight microelectrodes.

In some embodiments, a panel <NUM> has a length of about <NUM>, wherein the longitudinal portion <NUM> has a length of about <NUM> and a width no greater than about <NUM>, and the base portion <NUM> has a length of about <NUM> and a width of about <NUM>. Each pair of microelectrodes is spaced apart from an adjacent pair of microelectrodes by a distance of about <NUM>, with each microelectrode having a width of about <NUM> microns, and a length of about <NUM>.

In some embodiments, the substrate <NUM> comprises multiple layers, for example, first or outer layer 81a, second or middle layer 81b, and third or inner layer 81c, each having a first surface <NUM> and a second surface <NUM>. It is understood that the letters "a", "b" and "c" designate corresponding features in the layers 81a, 81b and 81c of the substrate <NUM>. The microelectrodes <NUM> are applied to or otherwise deposited on the first surface 91a of the outer layer 81a, to overlie through-holes 86a which are formed in the layer 81a to provide connection access for electrical traces 87b that extend along the first surface 91b of the longitudinal portion 82b of the second layer 81b between corresponding microelectrodes <NUM> and soldering pads <NUM> carried on the second surface 92c of the base portion 84c of the third layer 81c. Additional traces 87c run along the first surface 91c of the third layer 81c. Through-holes 86b, 89b (not shown) and 89c are formed in the layers 81b and 81c to provide connection access for the electrical traces 87b and 87c to more proximal microelectrodes <NUM>, and more proximal soldering pads (not shown in <FIG>). It is understood that the plurality of layers <NUM> depends on the amount of surface and space available thereon to accommodate the plurality of traces <NUM> connecting the microelectrodes <NUM> and the soldering pads <NUM>. It is also understood that with increasing layers flexibility of the spines can be reduced. Thus, the plurality of layers to accommodate the plurality of microelectrodes is balanced against the flexibility of the spines which enable conformity to tissue surface but decreases with increasing substrate thickness. In the illustrated embodiment of <FIG>, the substrate <NUM> has three layers with each layer <NUM> carrying four traces. It is understood that there is one corresponding trace <NUM> and one corresponding soldering pad <NUM> for each microelectrode <NUM>. Each lead wire <NUM> is soldered to a corresponding soldering pad. In that regard, it is also understood that the traces may be arranged differently, in different patterns and/or on different layers, as needed or appropriate.

As shown in <FIG>, the substrate <NUM> is affixed to the nonconductive covering <NUM> of the spine <NUM> with the longitudinal portion <NUM> extending longitudinally along the spine <NUM> and the lateral portions <NUM> wrapped circumferentially around the spine <NUM>. In that regard, the lateral dimension or width W of the lateral portions <NUM>, and more significantly of the microelectrodes <NUM>, is comparable to the circumference of the spine <NUM> such that opposing ends 85E of the microelectrodes can reach each other or at least come in close contact to generally form and function as ring microelectrodes R carried on the spine <NUM>. In the illustrated embodiment of <FIG>, the substrate <NUM> is affixed to the forward-facing or distal side of the spine that is adapted to contact tissue, although it is understood that the placement side of the substrate is less critical where the microelectrodes are long enough to wrap around the spine. In another embodiment discussed further below, placement side is more critical where the lateral dimension W is adjusted and decreased as desired or appropriate for lesser circumferential reach around the spine <NUM>.

As shown in <FIG>, each spine <NUM> is preformed with a slight inward curvature such that the distal electrode assembly <NUM> has a generally slightly concave configuration resembling an open umbrella. This preformed configuration enables each spine <NUM> to engage tissue surface <NUM> generally along its entire length when catheter is advanced distally against tissue surface, as shown in <FIG>. Without the preformed configuration, the distal electrode assembly <NUM> may tend to flip outwardly (much like an umbrella flipping inside out under strong wind) and lose tissue contact as the catheter is pushed distally against tissue surface.

As <FIG> illustrates, ends 85E of microelectrodes may not be in contact with tissue surface which exposes the microelectrodes to detecting undesirable noise, for example, far-field signals. Accordingly, <FIG> and <FIG> illustrate distal electrode assembly <NUM> of an alternate embodiment which provides a greater planar surface for tissue contact that minimizes exposure of the microelectrodes to noise and far-field signals. It is understood that similar components between the distal electrode assembly <NUM> and distal electrode assembly <NUM> are designated by similar reference numbers for ease of discussion herein.

Whereas the spine <NUM> of <FIG> has a more circular cross-section, spine <NUM> of <FIG> has a more rectangular cross section which provides the greater planar surface <NUM> on which flexible microelectrode member in the form of panel <NUM> can be selectively applied or affixed. Advantageously, the entirety of the microelectrodes <NUM> (including their ends 180E) is confined to the surface area of the planar surface <NUM> and therefore generally the entirety of microelectrodes <NUM> is in contact with tissue when the planar surface <NUM> is in contact with tissue <NUM>, as shown in <FIG>.

Support member <NUM> has a rectangular cross-section which is adopted by heat-shrink nonconductive covering <NUM> to provide the greater planar surface <NUM>. In some embodiments, the panel <NUM> as shown in <FIG> has substrate <NUM>, microelectrodes <NUM>, traces <NUM> and soldering pads <NUM> (not shown) having similar construction as their counterparts described above for panel <NUM>. The substrate <NUM> comprises multiple layers, for example, first or outer layer 181a, second or middle layer 181b, and third or inner layer 181c, each having a first surface <NUM> and a second surface <NUM>. However, as one difference, the substrate <NUM> is devoid of lateral portions, with a longitudinal portion182 having a lateral dimension W that is comparable or at least no greater than the lateral dimension of the planar surface <NUM> so that the substrate <NUM> remains confined on the planar surface <NUM>. The microelectrodes <NUM> are elongated and thin. To achieve a minimum space gap S between adjacent microelectrodes <NUM> of a pair while accommodating through-holes <NUM>, microelectrodes <NUM> have enlarged portions or ends <NUM>, as shown in <FIG>, that are sized larger than the through-holes <NUM> to span and overlie the through-holes <NUM> so that traces 187b and 187c can be connected to the microelectrodes <NUM>. In one embodiment, the microelectrode has a width of about <NUM> microns and the enlarged portion <NUM> has a width of about <NUM> microns.

The enlarged portion or end <NUM> of a microelectrode may extend to the right (forming a "right-handed microelectrode" 185R) or to the left (forming a "left-handed microelectrode" <NUM>), as shown in <FIG>. A pair may comprise a right-handed microelectrode 185R and a left handed microelectrode <NUM>, as shown in <FIG>, or two right-handed microelectrodes 185R-185R, as shown in <FIG>, or two left-handed microelectrodes <NUM>-<NUM>, as shown in <FIG>. The microelectrodes of a pair may be arranged in any formation, including, for example, a mirrored pairs (<FIG>), as upside down pairs (<FIG>), as side-by-side pairs (<FIG>, <FIG>), or as stacked pairs (<FIG>). In any case, the enlarged portions ends are turned outwardly away from each other so that the space gap distance as defined between adjacent linear edges can be minimized.

As described above in relation to <FIG>, the microelectrodes <NUM> of <FIG> and <FIG> are similarly affixed to the front surface 191a of the longitudinal portion 182a of the first layer 181a, and soldering pads <NUM> are affixed to the second surface 192c of the base portion 184c of the third layer 181c. Traces 187b and 187c run along the second and third layers 181b and 181c, respectively. Through-holes 186a, 189b and 189c are formed in the layers 181a, 181b and 181c, respectively, to provide the traces with connection access to the microelectrodes <NUM> and the soldering pads <NUM> (not shown). Again, it is understood that the plurality of layers <NUM> depends on the amount of surface and space available thereon to accommodate the plurality of traces <NUM> connecting the microelectrodes <NUM> and the soldering pads <NUM>, which accommodation is balanced against the desired flexibility of the spine <NUM> with the understanding that increasing thickness of the substrate can decrease the flexibility of the spine <NUM>. In the illustrated embodiments of <FIG> and <FIG>, each layer <NUM> accommodates four traces for a total of eight traces servicing eight microelectrodes and eight soldering pads.

With each spine <NUM> preformed with a slight inward curvature such that the distal electrode assembly <NUM> has a generally slightly concave configuration resembling an open umbrella, the planar surface <NUM> and the microelectrodes <NUM> thereon can fully engage and make contact with tissue surface so as to minimize exposure of the microelectrodes to noise and far-field signals without flipping inside out, as shown in <FIG>. The substrate <NUM> is selectively affixed to the forward-facing or distal side of the spine <NUM> where the planar surface <NUM> is adapted to contact tissue surface with minimal exposure of the microelectrodes <NUM> to noise and far-field signals.

Distal electrode assembly <NUM> having spines <NUM> with a rectangular cross-section wherein the X dimension along the planar surface <NUM> is greater than the Y dimension perpendicularly thereto, as shown in <FIG>, is also particularly adapted for minimizing kinking and stress to the spines at their area of greatest flexion or divergence D (see <FIG>) located slightly distal of the distal end of stem <NUM>.

It is understood that as the need or desire arises, any given spine may carry one or more flexible electrode panel of the same or different embodiments, as described above.

In some embodiments, the spine support members <NUM>/<NUM> are formed from a single elongated hollow cylinder or tube <NUM>, as shown in <FIG>, with an intact proximal cylindrical portion <NUM> (which may form the stem <NUM>/<NUM> of the distal electrode assembly), and a distal portion <NUM> with formed elongated extensions or fingers <NUM> that function as the plurality of support members <NUM>, separated by space gaps therebetween that are formed by longitudinal cuts in the sidewall of the cylinder <NUM>, or by removal, e.g., laser cutting, of elongated longitudinal strips <NUM> from the sidewall of cylinder <NUM>. Each finger <NUM> is shaped to diverge or splay outward at or near its proximal end and to have a slight inward curvature, as shown in <FIG>.

In the depicted embodiment, the lead wires <NUM> extending through the central lumen <NUM> of the catheter body <NUM> and the first lumen <NUM> in the deflection section <NUM> may be enclosed within a protective sheath <NUM> to prevent contact with other components in the catheter. The protective sheath <NUM> may be made of any suitable material, preferably polyimide. As would be recognized by one skilled in the art, the protective sheath can be eliminated if desired.

The microelectrodes <NUM> can be made of any suitable solid conductive material, such as platinum or gold, preferably a combination of platinum and iridium. The closely-spaced microelectrode pairs allow for more accurate detection of near field pulmonary vein potential versus far field atrial signals, which is very useful when trying to treat atrial fibrillation. Specifically, the near field pulmonary vein potentials are very small signals whereas the atria, located very close to the pulmonary vein, provides much larger signals. Accordingly, even when the mapping array is placed in the region of a pulmonary vein, it can be difficult for the physician to determine whether the signal is a small, close potential (from the pulmonary vein) or a larger, farther potential (from the atria). Closely-spaced bipole microelectrodes permit the physician to more accurately determine whether he/she is looking at a close signal or a far signal. Accordingly, by having closely-spaced microelectrodes, one is able to better target the locations of myocardial tissue that have pulmonary vein potentials and therefore allows the clinician to deliver therapy to the specific tissue. Moreover, the closely-spaced microelectrodes allow the physician to better determine the anatomical location of the ostium/ostia by the electrical signal.

As described above, the electromagnetic position sensor <NUM> is housed in the lumen <NUM> of the stem <NUM>, as shown in <FIG>. The sensor cable <NUM> extends from a proximal end of the position sensor, via through-hole <NUM> (not shown) of the washers 50D and 50P, the fifth lumen <NUM> of the tubing <NUM> of the deflection section <NUM> (see <FIG>), and the central lumen <NUM> of the catheter body <NUM> (see <FIG>). The cable <NUM> is attached to a PC board in the control handle <NUM>, as known in the art. In some embodiments, one or more distal electromagnetic position sensors may be housed in the distal electrode assembly, for example, in one or more distal portions of the spines <NUM>.

As shown in <FIG> and <FIG>, the puller wires 32A and 32B (whether as two separate tensile members or parts of a single tensile member) are provided for bi-directional deflection of the intermediate section <NUM>. The puller wires are actuated by mechanisms in the control handle <NUM> that are responsive to a thumb control knob or a deflection control knob <NUM> (see <FIG>). Suitable control handles are disclosed in <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT> and <CIT>. The puller wires 32A and 32B extend through the central lumen <NUM> of the catheter body <NUM> (see <FIG>) and through the second and fourth lumens <NUM> and <NUM>, respectively, of the tubing <NUM> of the deflection section <NUM> (see <FIG>). They extend through holes <NUM> and <NUM>, respectively of the washers 50D and 50P (see <FIG>). Where the puller wires are part of a single tensile member, the single tensile member has a U-bend at the distal face of the distal washer 50D which anchors the distal ends of the puller wires. In that regard, the U-bend extends through a short protective tubing <NUM>. Alternatively, where the puller wires are separate tensile members, their distal ends may be anchored via T-bars, as known in the art and described in, for example, <CIT>. In any case, the puller wires may be made of any suitable metal, such as stainless steel or Nitinol, and each is preferably coated with TEFLON or the like. The coating imparts lubricity to the puller wires. The puller wires preferably have a diameter ranging from about <NUM> to about <NUM> inch (about <NUM> to <NUM>).

A compression coil <NUM> is situated within the central lumen <NUM> of the catheter body <NUM> in surrounding relation to each puller wire 32A and 32B, as shown in <FIG>. Each compression coil <NUM> extends from the proximal end of the catheter body <NUM> to the proximal end of the intermediate section <NUM>. The compression coils <NUM> are made of any suitable metal, preferably stainless steel. Each compression coil <NUM> is tightly wound on itself to provide flexibility, i.e., bending, but to resist compression. The inner diameter of the compression coil <NUM> is preferably slightly larger than the diameter of its puller wire. The TEFLON coating on each puller wire allows it to slide freely within its compression coil.

The compression coil <NUM> is anchored at its proximal end to the outer wall <NUM> of the catheter body <NUM> by a proximal glue joint (not shown) and at its distal end to the intermediate section <NUM> by a distal glue joint (not shown). Both glue joints may comprise polyurethane glue or the like. The glue may be applied by means of a syringe or the like through a hole made the sidewalls of the catheter body <NUM> and the tubing <NUM>. Such a hole may be formed, for example, by a needle or the like that punctures the sidewalls which are heated sufficiently to form a permanent hole. The glue is then introduced through the hole to the outer surface of the compression coil <NUM> and wicks around the outer circumference to form a glue joint about the entire circumference of the compression coil.

Within the second and fourth lumens <NUM> and <NUM> of the intermediate section <NUM>, each puller wire 32A and 32B extends through a plastic, preferably TEFLON, puller wire sheath <NUM> (<FIG>), which prevents the puller wires from cutting into the sidewall of the tubing <NUM> of the deflection section <NUM> when the deflection section <NUM> is deflected.

Claim 1:
An electrophysiological catheter comprising:
an elongated body (<NUM>);
a distal electrode assembly (<NUM>, <NUM>) comprising:
a plurality of spines (<NUM>, <NUM>), each spine having a free distal end and a proximal end extending from a distal end of the elongated body; and
a flexible panel (<NUM>, <NUM>) wrapped around and affixed to an outer surface of at least one spine, the flexible panel having a substrate (<NUM>, <NUM>) conforming to the outer surface of the at least one spine, at least one pair of microelectrodes (<NUM>, <NUM>), a trace for each microelectrode (<NUM>, <NUM>), and a soldering pad (<NUM>,<NUM>) for each microelectrode,
wherein each trace electrically couples a respective microelectrode and a respective soldering pad,
wherein said substrate comprises a first layer (81a, 181a), a second layer (81b, 181b) and a third layer (81c, 181c), and
wherein said at least one pair of microelectrodes is disposed on the first layer, and wherein electrical traces are disposed on the second layer and the third layer, and wherein through holes (<NUM>, <NUM>) are formed in the first layer and second layer to provide connection access between the microelectrodes and the electrical traces.