An open-irrigated catheter system includes a catheter body and a tip assembly, coupled to a distal end of the catheter body. The tip assembly includes an exterior wall that is conductive for delivering radio frequency (RF) energy for an RF ablation procedure, and that defines an interior region. The exterior wall includes a number of proximal irrigation ports and a number of distal irrigation ports. At least one fluid chamber is defined within the interior region and is in fluid communication with at least one of the proximal irrigation ports and the distal irrigation ports. At least one fluid lumen extends from a fluid source, through the catheter body, to the tip assembly, and is in fluid communication with the at least one fluid chamber.

TECHNICAL FIELD

The present disclosure relates to medical devices. More specifically, the invention relates to devices and systems for performing ablation and mapping functions.

BACKGROUND

Aberrant conductive pathways disrupt the normal path of the heart's electrical impulses. For example, conduction blocks can cause the electrical impulse to degenerate into several circular wavelets that disrupt the normal activation of the atria or ventricles. The aberrant conductive pathways create abnormal, irregular, and sometimes life-threatening heart rhythms called arrhythmias. Ablation is one way of treating arrhythmias and restoring normal conduction. The sources of the aberrant pathways (called focal arrhythmia substrates) are located or mapped using mapping electrodes situated in a desired location. After mapping, the physician may ablate the aberrant tissue. In radio frequency (RF) ablation, RF energy is directed from the ablation electrode through tissue to an electrode to ablate the tissue and form a lesion.

SUMMARY

In an Example 1, an open-irrigated catheter system comprises a catheter body; a tip assembly, coupled to a distal end of the catheter body, and having an exterior wall that defines an interior region within the tip assembly, wherein the exterior wall includes a plurality of proximal irrigation ports and a plurality of distal irrigation ports, and wherein the exterior wall is conductive for delivering radio frequency (RF) energy for an RF ablation procedure; at least one fluid chamber defined within the interior region, wherein the at least one fluid chamber is in fluid communication with at least one of the plurality of proximal irrigation ports and the plurality of distal irrigation ports; and at least one fluid lumen extending from a fluid source, through the catheter body, to the tip assembly, wherein the at least one fluid lumen is in fluid communication with the at least one fluid chamber.

In an Example 2, the system of Example 1, wherein the plurality of proximal irrigation ports comprises at least 12 irrigation ports.

In an Example 3, the system of Example 2, wherein the plurality of proximal irrigation ports comprises at least 36 irrigation ports.

In an Example 4, the system of any of Examples 1-3, wherein the plurality of proximal irrigation ports is arranged in an evenly-spaced array positioned circumferentially around a proximal portion of the tip assembly.

In an Example 5, the system of Example 4, wherein the array comprises at least one row.

In an Example 6, the system of Example 5, the array comprising a first row of irrigation ports and a second row of irrigation ports, wherein the second row is aligned with the first row to form a plurality of pairs of longitudinally-aligned irrigation ports.

In an Example 7, the system of Example 5, the array comprising a first row of irrigation ports and a second row of irrigation ports, wherein the second row is offset from the first row.

In an Example 8, the system of any of Examples 1-7, wherein the at least one fluid chamber comprises a proximal fluid chamber and a distal fluid chamber, wherein the proximal fluid chamber is in fluid communication with the plurality of proximal irrigation ports, and wherein the distal fluid chamber is in fluid communication with the plurality of distal irrigation ports.

In an Example 9, the system of Example 8, wherein the at least one fluid lumen comprises a first fluid lumen and a second fluid lumen, wherein the first fluid lumen is in fluid communication with the proximal fluid chamber and wherein the second fluid lumen is in fluid communication with the distal fluid chamber.

In an Example 10, the system of Example 9, wherein the fluid source provides a first stream of fluid to the proximal fluid chamber and a second stream of fluid to the distal fluid chamber, wherein the second stream of fluid is provided at a greater flow rate than the first stream of fluid.

In an Example 11, the system of Example 8, wherein the at least one fluid lumen comprises a single fluid lumen that is in fluid communication with the proximal fluid chamber, the system further comprising a fluid path extending between the proximal fluid chamber and the distal fluid chamber such that the proximal fluid chamber is in fluid communication with the distal fluid chamber.

In an Example 12, the system of Example 11, further comprising a distal insert, wherein the fluid path is defined within the distal insert.

In an Example 13, the system of any of Examples 1-12, wherein the external wall includes a plurality of mapping-electrode openings, and wherein the system further comprises a plurality of mapping electrodes, wherein each of the plurality of mapping electrodes is positioned within one of the plurality of mapping-electrode openings.

In an Example 14, the system of any of Examples 1-13, wherein the plurality of distal irrigation ports comprises six distal irrigation ports, wherein the six distal irrigation ports are evenly-spaced circumferentially around a distal portion of the tip assembly.

In an Example 15, the system of any of Examples 1-14, wherein each of the proximal irrigation ports includes a diameter of between 0.00254 cm (0.001 in.) and 0.01016 cm (0.004 in.).

In an Example 16, an open-irrigated catheter system comprises a catheter body; a tip assembly, coupled to a distal end of the catheter body, and having an exterior wall that defines an interior region within the tip assembly, wherein the exterior wall includes a plurality of proximal irrigation ports and a plurality of distal irrigation ports, and wherein the exterior wall is conductive for delivering radio frequency (RF) energy for an RF ablation procedure; at least one fluid chamber defined within the interior region, wherein the at least one fluid chamber is in fluid communication with at least one of the plurality of proximal irrigation ports and the plurality of distal irrigation ports; and at least one fluid lumen extending from a fluid source, through the catheter body, to the tip assembly, wherein the at least one fluid lumen is in fluid communication with the at least one fluid chamber.

In an Example 17, the system of Example 16, wherein the plurality of proximal irrigation ports comprises at least 12 irrigation ports.

In an Example 18, the system of Example 17, wherein the plurality of proximal irrigation ports comprises at least 36 irrigation ports.

In an Example 19, the system of Example 16, wherein the plurality of proximal irrigation ports is arranged in an evenly-spaced array positioned circumferentially around a proximal portion of the tip assembly.

In an Example 20, the system of Example 19, wherein the array comprises at least one row.

In an Example 21, the system of Example 20, the array comprising a first row of irrigation ports and a second row of irrigation ports, wherein the second row is aligned with the first row to form a plurality of pairs of longitudinally-aligned irrigation ports.

In an Example 22, the system of Example 20, the array comprising a first row of irrigation ports and a second row of irrigation ports, wherein the second row is offset from the first row.

In an Example 23, the system of Example 16, wherein the at least one fluid chamber comprises a proximal fluid chamber and a distal fluid chamber, wherein the proximal fluid chamber is in fluid communication with the plurality of proximal irrigation ports, and wherein the distal fluid chamber is in fluid communication with the plurality of distal irrigation ports.

In an Example 24, the system of Example 23, wherein the at least one fluid lumen comprises a first fluid lumen and a second fluid lumen, wherein the first fluid lumen is in fluid communication with the proximal fluid chamber and wherein the second fluid lumen is in fluid communication with the distal fluid chamber.

In an Example 25, the system of Example 24, wherein the fluid source provides a first stream of fluid to the proximal fluid chamber and a second stream of fluid to the distal fluid chamber, wherein the second stream of fluid is provided at a greater flow rate than the first stream of fluid.

In an Example 26, the system of Example 23, wherein the at least one fluid lumen comprises a single fluid lumen that is in fluid communication with the proximal fluid chamber, the system further comprising a fluid path extending between the proximal fluid chamber and the distal fluid chamber such that the proximal fluid chamber is in fluid communication with the distal fluid chamber.

In an Example 27, the system of Example 26, further comprising a distal insert, wherein the fluid path is defined within the distal insert.

In an Example 28, the system of Example 16, wherein the external wall includes a plurality of mapping-electrode openings, and wherein the system further comprises a plurality of mapping electrodes, wherein each of the plurality of mapping electrodes is positioned within one of the plurality of mapping-electrode openings.

In an Example 29, the system of Example 16, wherein the plurality of distal irrigation ports comprises six distal irrigation ports, wherein the six distal irrigation ports are evenly-spaced circumferentially around a distal portion of the tip assembly.

In an Example 30, the system of Example 16, wherein each of the proximal irrigation ports includes a diameter of between 0.00254 cm (0.001 in.) and 0.01016 cm (0.004 in.).

In an Example 31, an open-irrigated catheter comprises a tip assembly having an exterior wall that defines an interior region within the tip assembly, wherein the exterior wall includes a plurality of proximal irrigation ports and a plurality of distal irrigation ports, and wherein the exterior wall is conductive for delivering radio frequency (RF) energy for an RF ablation procedure; at least one fluid chamber defined within the interior region, wherein the at least one fluid chamber is in fluid communication with at least one of the plurality of proximal irrigation ports and the plurality of distal irrigation ports; and at least one fluid lumen extending from a fluid source, through the catheter body, to the tip assembly, wherein the at least one fluid lumen is in fluid communication with the at least one fluid chamber.

In an Example 32, the catheter of Example 31, wherein the at least one fluid chamber comprises a proximal fluid chamber and a distal fluid chamber, wherein the proximal fluid chamber is in fluid communication with the plurality of proximal irrigation ports, and wherein the distal fluid chamber is in fluid communication with the plurality of distal irrigation ports.

In an Example 33, the catheter of Example 32, wherein the at least one fluid lumen comprises a first fluid lumen and a second fluid lumen, wherein the first fluid lumen is in fluid communication with the proximal fluid chamber and wherein the second fluid lumen is in fluid communication with the distal fluid chamber.

In an Example 34, the catheter of Example 33, wherein the fluid source provides a first stream of fluid to the proximal fluid chamber and a second stream of fluid to the distal fluid chamber, wherein the second stream of fluid is provided at a greater flow rate than the first stream of fluid.

In an Example 35, the catheter of Example 31, wherein the plurality of distal irrigation ports comprises six distal irrigation ports, wherein the six distal irrigation ports are evenly-spaced circumferentially around a distal portion of the tip assembly.

DETAILED DESCRIPTION

Embodiments of the disclosure relate to a radiofrequency (RF) ablation catheter system. In embodiments, the catheter may be a hybrid catheter, which may be configured to be used for both localized mapping and ablation functions. The hybrid catheter may be configured to provide localized, high resolution ECG signals during ablation. This localized mapping may enable the ablation procedure to be more precise than that which can be achieved with conventional, non-hybrid ablation catheters. The catheter has an open-irrigated catheter design. A cooling fluid, such as a saline, is delivered through the catheter to a tip assembly having a tissue ablation electrode, where the fluid exits through irrigation ports defined in the tissue ablation electrode to cool the electrode and surrounding tissue during ablation. Clinical benefits of such a catheter may include, but are not limited to, controlling the temperature and reducing coagulum formation on the tip of the catheter, preventing impedance rise of tissue in contact with the catheter tip, and maximizing potential energy transfer to the tissue. Additionally, the localized intra cardiac electrical activity can be recorded in real time or near-real time at the location of energy delivery.

A number of adverse effects may be encountered with open-irrigated RF ablation catheters and may include, for example, excessive heating of a proximal portion of the tissue ablation electrode (e.g., due to edge effect), current density concentrations (e.g., due to geometric discontinuities, radius changes, etc.), and/or the like. Some developments to address these issues have included the addition of proximal irrigation ports similar in size to the distal irrigation ports, and the replacement of larger distal irrigation ports with a large number of very small irrigation ports dispersed throughout the ablation electrode. Both of these solutions may provide some mitigation of proximal heating due to edge effect, but have a tendency to change the current pathway due to the cloud of cooling fluid that forms around the electrode. This can either result in current loss, as the current shunts through the ionic fluid and away from the target tissue, or result in excessive tissue heating, which may be a byproduct of a localized saline cloud driving too much current into the tissue.

Embodiments of the invention provide an open-irrigated catheter design that includes distal irrigation ports and much smaller proximal irrigation ports (that may be referred to as “micro-holes”), thereby providing cooling fluid flow to cool the proximal portion of the electrode, while maintaining the desired current pathways due to the more forceful flow of fluid from the larger distal irrigation ports.FIG. 1depicts a mapping and ablation system100that includes an open-irrigated ablation catheter102, according to embodiments of the invention. The illustrated catheter102includes a tip assembly104having a tissue ablation electrode105, with mapping microelectrodes106, proximal irrigation ports108, and distal irrigation ports110. The catheter102includes a catheter body112and a proximal catheter handle assembly114, having a handle116, coupled to a proximal end118of the catheter body112. The tip assembly104is coupled to a distal end120of the catheter body112.

In some instances, the mapping and ablation system100may be utilized in ablation procedures on a patient and/or in ablation procedures on other objects. In various embodiments, the ablation catheter102may be configured to be introduced into or through the vasculature of a patient and/or into or through any other lumen or cavity. In an example, the ablation catheter102may be inserted through the vasculature of the patient and into one or more chambers of the patient's heart (e.g., a target area). When in the patient's vasculature or heart, the ablation catheter102may be used to map and/or ablate myocardial tissue using the microelectrodes106and/or the tissue ablation electrode105. In embodiments, the tissue ablation electrode105may be configured to apply ablation energy to myocardial tissue of the heart of a patient.

According to embodiments, the tissue ablation electrode105may be, or be similar to, any number of different tissue ablation electrodes such as, for example, the IntellaTip MiFi,™ or the Blazer™ Ablation tip, both of which are available from Boston Scientific of Marlborough, Mass. In embodiments, the tissue ablation electrode105may have any number of different sizes, shapes, and/or other configuration characteristics. The tissue ablation electrode105may be any length and may have any number of the microelectrodes106positioned therein and spaced circumferentially and/or longitudinally about the tissue ablation electrode105. In some instances, the tissue ablation electrode105may have a length of between one (1) mm and twenty (20) mm, three (3) mm and seventeen (17) mm, or six (6) mm and fourteen (14) mm. In one illustrative example, the tissue ablation electrode105may have an axial length of about eight (8) mm. In another illustrative example, the tissue ablation electrode105may include an overall length of approximately 4-10 mm. In embodiments, the tissue ablation electrode105may include an overall length of approximately 4 mm, 4.5 mm, and/or any other desirable length. In some cases, the plurality of microelectrodes106may be spaced at any interval about the circumference of the tissue ablation electrode105. In one example, the tissue ablation electrode105may include at least three microelectrodes106equally or otherwise spaced about the circumference of the tissue ablation electrode105and at the same or different longitudinal positions along the longitudinal axis of the tissue ablation electrode105.

In embodiments, the catheter102may include a deflectable catheter region124configured to allow the catheter102to be steered through the vasculature of a patient, and which may enable the tissue ablation electrode105to be accurately placed adjacent a targeted tissue region. A steering wire (not shown) may be slidably disposed within the catheter body112. The handle assembly114may include one or more steering members126such as, for example, rotating steering knobs that are rotatably mounted to the handle116. Rotational movement of a steering knob126relative to the handle116in a first direction may cause a steering wire to move proximally relative to the catheter body112which, in turn, tensions the steering wire, thus pulling and bending the catheter deflectable region124into an arc; and rotational movement of the steering knob126relative to the handle116in a second direction may cause the steering wire to move distally relative to the catheter body112which, in turn, relaxes the steering wire, thus allowing the catheter102to return toward its original form. To assist in the deflection of the catheter102, the deflectable catheter region124may be made of a lower durometer plastic than the remainder of the catheter body112.

According to embodiments, the catheter body112includes one or more cooling fluid lumens (not shown) and may include other tubular element(s) to provide desired functionality to the catheter102. The addition of metal in the form of a braided mesh layer sandwiched in between layers of plastic tubing may be used to increase the rotational stiffness of the catheter102.

The illustrated system100includes an RF generator128used to generate RF energy for use during an ablation procedure. The RF generator128may include an RF source130that produces the RF energy and a controller132for controlling the timing, level, and/or other characteristics of the RF energy delivered through the tip assembly104. The RF generator128may be configured to deliver ablation energy to the ablation catheter102in a controlled manner in order to ablate the target tissue sites. Ablation of tissue within the heart is well known in the art, and thus for purposes of brevity, the RF generator128will not be described in further detail. Further details regarding RF generators are provided in U.S. Pat. No. 5,383,874, which is expressly incorporated herein by reference in its entirety for all purposes.

The illustrated system100also includes a fluid source134, having a fluid reservoir136and a pump138for providing cooling fluid, such as a saline, through the catheter102and out through the irrigation ports108and110. A mapping signal processor140may be connected to the electrodes106, also referred to herein as microelectrodes. The mapping signal processor140and electrodes106may be configured to detect electrical activity of the heart. This electrical activity may be evaluated to analyze an arrhythmia and to determine where to deliver the ablation energy as a therapy for the arrhythmia. Although the mapping processor140and RF generator128are shown as discrete components, they can alternatively be incorporated into a single integrated device.

One of ordinary skill in the art will understand that various components such as, for example, aspects of the RF generator128, the fluid source,134, and/or the mapping signal processor140, may be implemented using software, hardware, and/or firmware. Various methods of operation may be implemented as a set of instructions contained on a computer-accessible medium capable of directing a processor to perform the respective method.

The RF ablation catheter102as described may be used to perform various diagnostic functions to assist the physician in an ablation treatment. For example, in some embodiments, the catheter102may be used to ablate cardiac arrhythmias, and at the same time provide real-time assessment of a lesion formed during RF ablation. Real-time assessment of the lesion may involve any of monitoring surface and/or tissue temperature at or around the lesion, reduction in the electrocardiogram signal, a drop in impedance, direct and/or surface visualization of the lesion site, and imaging of the tissue site (e.g., using computed tomography, magnetic resonance imaging, ultrasound, etc.). In addition, the presence of the microelectrodes within the RF tip electrode can operate to assist the physician in locating and positioning the tip electrode at the desired treatment site, and to determine the position and orientation of the tip electrode relative to the tissue to be ablated.

Illustrative catheters that may be used as the catheter102may include, among other ablation and/or mapping catheters, those described in U.S. patent application Ser. No. 12/056,210 filed on Mar. 26, 2008, and entitled HIGH RESOLUTION ELECTROPHYSIOLOGY CATHETER, and U.S. Pat. No. 8,414,579 filed on Jun. 23, 2010, entitled MAP AND ABLATE OPEN IRRIGATED HYBRID CATHETER, which are both hereby incorporated herein by reference in their entireties for all purposes. Alternatively, or in addition, catheters that may be used as the catheter102may include, among other ablation and/or mapping catheters, those described in U.S. Pat. No. 5,647,870 filed on Jan. 16, 1996, as a continuation of U.S. Ser. No. 206,414, filed Mar. 4, 1994 as a continuation-in-part of U.S. Ser. No. 33,640, filed Mar. 16, 1993, entitled MULTIPLE ELECTRODE SUPPORT STRUCTURES, U.S. Pat. No. 6,647,281 filed on Apr. 6, 2001, entitled EXPANDABLE DIAGNOSTIC OR THERAPEUTIC APPARATUS AND SYSTEM FOR INTRODUCING THE SAME INTO THE BODY, and U.S. Pat. No. 8,128,617 filed on May 27, 2008, entitled ELECTRICAL MAPPING AND CRYO ABLATING WITH A BALLOON CATHETER, which are all hereby incorporated herein by reference in their entireties for all purposes.

FIGS. 2A-2Dillustrate a hybrid catheter200, according to embodiments of the invention, having proximal and distal irrigation ports and three microelectrodes used to perform a mapping function. The illustrated catheter200includes a tip assembly202, having a tip body204, and an open-irrigated ablation electrode206used to perform mapping and ablation functions. In embodiments, the ablation functions may be performed, in part, by the ablation electrode206, which may function as an RF electrode. The mapping functions may be performed, at least in part, by mapping electrodes208.

With particular reference toFIG. 2B, the illustrated tip assembly202includes a generally hollow ablation electrode206having a distal insert210disposed therein and configured to separate a proximal fluid chamber212and distal fluid chamber214. The tip assembly202has an open interior region216defined by an exterior wall218of the tip assembly202. Fluid flow through the chambers212and214may be used to provide internal, targeted cooling of portions of the ablation electrode206. In the illustrated embodiments, the hollow tip body204has a generally cylindrical shape, but in other embodiments, the tip body204may have any number of different shapes such as, for example, an elliptical shape, a polygonal shape, and/or the like. By way of an example and not limitation, embodiments of the tip assembly202may have a diameter on the order of about 0.08-0.1 inches, a length on the order of about 0.2-0.3 inches, and an exterior wall218with a thickness on the order of about 0.003-0.004 inches.

As the terms are used herein with respect to ranges of measurements (such as those disclosed immediately above), “about” and “approximately” may be used, interchangeably, to refer to a measurement that includes the stated measurement and that also includes any measurements that are reasonably close to the stated measurement, but that may differ by a reasonably small amount such as will be understood, and readily ascertained, by individuals having ordinary skill in the relevant arts to be attributable to measurement error, differences in measurement and/or manufacturing equipment calibration, human error in reading and/or setting measurements, adjustments made to optimize performance and/or structural parameters in view of differences in measurements associated with other components, particular implementation scenarios, and/or the like.

According to embodiments, the distal insert210may be made of plastic components such as, for example, Ultem. Various distal insert embodiments include design elements configured for self-positioning the distal insert during manufacturing. Such embodiments may facilitate reducing the number of processing steps to join the distal insert to the tip electrode. Additionally, various distal insert embodiments may be configured for self-alignment and configured to isolate electrical components from the irrigation fluid. Some embodiments are configured for self-alignment, some embodiments are configured to isolate electrical components from the irrigation fluid, and some embodiments are configured for both self-alignment and for isolating electrical components from the irrigation fluid. Various designs of distal inserts as described above are described in U.S. Pat. No. 8,414,579, the entirety of which is hereby incorporated by reference herein for all purposes.

In embodiments, the ends of the distal insert210may be encapsulated with adhesives to provide a seal between the proximal and distal chambers212and214. In embodiments, the distal insert210may include openings or apertures220, each opening220sized to receive a microelectrode208and a corresponding noise artifact isolator222. These microelectrodes208may be used to image localized intra-cardiac activity. The microelectrodes208may, for example, be used to record high resolution, precise localized electrical activity, to prevent excessive heating of the ablation electrode206, to allow greater delivery of power, to prevent the formation of coagulum and to provide the ability to diagnose complex ECG activity. In embodiments, the microelectrodes208are small, independent diagnostic sensing electrodes embedded within the walls of the ablation electrode206of the RF ablation catheter200. The noise artifact isolator222electrically isolates the small electrodes208from the conductive exterior wall218of the ablation electrode206. According to embodiments, the noise artifact isolator222may be a polymer-based material sleeve and/or adhesive that encapsulates the microelectrodes208. The isolator222isolates the noise entrance creating a much cleaner electrogram during an RF ablation mode. These electrically-isolated microelectrodes208are able to sense highly localized electrical activity, avoid a far-field component, and simultaneously achieve the ability to ablate tissue without noise artifact during RF mode.

The illustrated distal insert210also includes a fluid conduit or passage224to permit fluid to flow from the proximal fluid reservoir212to the distal fluid reservoir214, a thermocouple opening226sized to receive a thermocouple228, and openings230sized to receive electrical conductors232used to provide electrical connections to the microelectrodes208. Also illustrated is a thermocouple wire234connected to the thermocouple228. According to embodiments, the distal insert210may be fabricated from stainless steel, a polymer, and/or the like. In embodiments, a proximal insert (not shown) may be disposed in an interior region236of a proximal portion238of the tip body204. The proximal insert may, in embodiments, prevent fluid from flowing back out of the proximal fluid chamber212, and may include apertures for the wires, conductors, and one or more fluid conduits.

According to embodiments, the ablation electrode206may be formed from a conductive material. For example, some embodiments use a platinum-iridium alloy. Some embodiments use an alloy with approximately90% platinum and10% iridium. The conductive material of the ablation electrode206is used to conduct RF energy used to form legions during the ablation procedure. In embodiments, the ablation electrode206includes a plurality of distal irrigation ports240near the distal end242of the ablation electrode206, and a plurality of proximal irrigation ports244near the proximal end246of the ablation electrode206. By way of example and not limitation, in embodiments, the distal irrigation ports240may each have a diameter approximately within a range of 0.01 to 0.02 inches. Fluid, such as a saline solution, flows from the distal fluid reservoir214, through these ports240, to the exterior of the catheter200. This fluid is used to cool the ablation electrode206and the tissue near the electrode206. This temperature control may facilitate reduction of coagulum formation on the tip of the catheter200, prevents impedance rise of tissue in contact with the catheter tip, and increases energy transfer to the tissue because of the lower tissue impedance.

According to embodiments, the proximal irrigation ports244are configured to facilitate a fluid flow out of the ablation electrode206to minimize char formation on the proximal region of the ablation electrode206. Providing proximal irrigation ports may also facilitate minimizing risk of thrombus and the potential for emboli. According to embodiments, the proximal irrigation ports are relatively small as compared, for example, to the distal irrigation ports. For example, in embodiments, each of the proximal irrigation ports244may have a diameter of approximately 0.00254 cm (0.001 in.) to 0.01016 cm (0.004 in.). In this manner, conventional flow characteristics associated with distal irrigation ports may be maintained, so as to maintain effective RF conduction for ablation. That is, for example, the proximal irrigation ports may be configured to provide a flow rate sufficient for achieving desired cooling results external to the ablation electrode206, while maintaining desired flow characteristics from the distal irrigation ports. The arrangement, size, and/or number of proximal irrigation ports may be adjusted based on the characteristics of the distal irrigation ports, the fluid chambers, the tip, and/or the like. In embodiments, the catheter200may include 6 distal irrigation ports240and between 12 and 36 proximal irrigation ports244. In other embodiments, the catheter may include more than 36 proximal irrigation ports244such as, for example, 54 ports, 72 ports, and/or the like.

Various embodiments isolate the microelectrode signal wires from the cooling fluid circulating in the proximal chamber of the hollow ablation electrode, and thus are expected to reduce the noise that is contributed form the internal cooling fluid circulation. The fluid seal can be provided without bonding or adhesive. The electrical components within the tip are isolated form the cooling flow of irrigation fluid while the irrigation fluid maintains internal cooling of the proximal and distal portions of the tip electrode. Further, such designs may have the potential of increasing the accuracy of the temperature readings from the thermocouple, and are described in U.S. Pat. No. 8,414,579, incorporated above.

FIGS. 3A and 3Billustrate a hybrid catheter300, according to embodiments of the invention, having a plurality of distal irrigation ports302and a plurality of proximal irrigation ports304. The hybrid catheter300includes a tip assembly306, having an ablation electrode308. The ablation electrode308includes an external wall310that encloses an interior region312. The interior region includes a proximal fluid chamber314and a distal fluid chamber316, separated by a distal insert318. A plurality of mapping electrodes320may be disposed in the external wall310. A cooling lumen322extends from a fluid source (not shown) to the distal fluid chamber316, and provides fluid to the proximal and distal fluid chambers314and316. As shown, for example, the cooling lumen322includes holes324to enable a portion of the fluid that is provided to the cooling lumen322to pass into the proximal fluid chamber314to cool a proximal portion326of the ablation electrode308. The fluid from the proximal chamber314also is passed out of the ablation electrode308via the proximal irrigation ports304. The remainder of the fluid provided to the cooling lumen322passes to the distal fluid chamber316and at least a portion of that fluid is passed out of the ablation electrode308via the distal irrigation ports302.

According to embodiments, a catheter may include a separate cooling lumen for providing fluid to each of the proximal and distal fluid chambers. In embodiments, both cooling lumens may be coupled to the same fluid source and/or a separate fluid source.FIG. 4illustrates a perspective cutaway view of a hybrid catheter tip assembly400, according to embodiments of the invention, having an ablation electrode402. The ablation electrode402includes an external wall404that encloses an interior region406. The interior region406includes a proximal fluid chamber408and a distal fluid chamber410, separated by a distal insert412. A plurality of mapping electrodes414may be disposed in the external wall404. The external wall404may also include a plurality of distal irrigation ports416and a plurality of proximal irrigation ports418. A first cooling lumen420extends from a fluid source (not shown) to the proximal fluid chamber408, and provides fluid to the proximal fluid chamber418. A second cooling lumen422extends from a fluid source (not shown) to the distal fluid chamber410, and provides fluid to the distal fluid chamber410. The fluid from the proximal chamber408is passed out of the ablation electrode402via the proximal irrigation ports418and the fluid from the distal fluid chamber410is passed out of the ablation electrode402via the distal irrigation ports416.

Electrical signals, such as electrocardiograms (ECGs), are used during a cardiac ablation procedure to distinguish viable tissue from not viable tissue. If ECG amplitudes are seen to attenuate during the delivery of RF energy into the tissue, the delivery of RF energy into that specific tissue may be stopped. However, noise on the ECG signals makes it difficult to view attenuation. It is currently believed that internal cooling fluid circulation, cooling fluid circulating externally in contact with other electrodes, and/or fluid seepage in between the electrodes and their housing may cause the noise on this type of ablation catheter.

FIG. 5depicts a hybrid catheter500in accordance with embodiments of the invention. The catheter500may be, include, or be similar to, the catheter102depicted inFIG. 1, the catheter200depicted inFIGS. 2A-2D, the catheter300depicted inFIGS. 3A and 3B, and/or the catheter tip assembly400depicted inFIG. 4. The illustrated catheter500includes a tip assembly502coupled to a distal end504of a catheter body506. The catheter body506includes a plurality of ring electrodes508. In embodiments, the catheter body506may include three ring electrodes508or any other desirable number of ring electrodes508. As illustrated, the tip assembly502includes an ablation electrode510having a plurality of mapping electrodes512, a plurality of distal irrigation ports514, and a plurality of proximal irrigation ports516. The proximal irrigation ports516are arranged in a first row518and a second row520. Each row518and520may include a plurality of proximal irrigation ports516evenly spaced circumferentially around the ablation tip electrode510. In embodiments, the ablation electrode510may include one row of proximal irrigation ports516, two rows of proximal irrigation ports516, three rows of proximal irrigation ports516, four rows of proximal irrigation ports516, or any other desired number of rows, each row having any number of proximal irrigation ports that may, for example, be evenly spaced circumferentially.

The proximal irrigation ports516depicted inFIG. 5, and described above, may be arranged in multiple rows, where each row is offset from an adjacent row. According to embodiments, proximal irrigation ports may be arranged in circumferential rows that are aligned to form multiple longitudinal columns of at least two irrigation ports.FIG. 6depicts a hybrid catheter600in accordance with embodiments of the invention. The catheter600may be, include, or be similar to, the catheter500depicted inFIG. 5. The illustrated catheter600includes a tip assembly602coupled to a distal end604of a catheter body606. The catheter body606includes a plurality of ring electrodes608. In embodiments, the catheter body606may include three ring electrodes608or any other desirable number of ring electrodes608. As illustrated, the tip assembly602includes an ablation electrode610having a plurality of mapping electrodes612, a plurality of distal irrigation ports614, and a plurality of proximal irrigation ports616. The proximal irrigation ports616are arranged in a first row618and a second row620. Each row618and620may include a plurality of proximal irrigation ports616evenly spaced circumferentially around the ablation electrode610. The proximal irrigation ports616may be arranged in circumferential rows618and620that are aligned to form multiple longitudinal columns622of at least two irrigation ports616each. The ablation electrode610may include any desired number of rows and/or columns of proximal irrigation ports616.