Irrigated ablation catheter with multiple sensors

Systems and methods are disclosed for providing and using an irrigated ablation catheter. The catheter may include a distal shell electrode having irrigation apertures. An insert disposed within the electrode has protrusions that mate with orifices in the shell of the electrode. Each protrusion has a port communicating with at least one interior lumen in the insert and a sensor is disposed in each port. A support seals the proximal end of the electrode and engages the insert. The plurality of sensors may be used to measure electrical and thermal characteristics surrounding the electrode and may help assess contact between the electrode and tissue and/or determine movement of the electrode during ablation.

FIELD OF THE PRESENT DISCLOSURE

This disclosure relates generally to methods and devices for percutaneous medical treatment, and specifically to catheters, in particular, irrigated ablation catheters. More particularly, this disclosure relates to irrigated ablation catheters designs that support and stabilize micro-elements for accurate thermal and/or electrical sensing properties while providing reduced interference with irrigation of the ablation electrode.

BACKGROUND

Radiofrequency (RF) 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. Specifically, targeted ablation may be performed for a number of indications. For example, ablation of myocardial tissue is well known as a treatment for cardiac arrhythmias by using a catheter to apply RF energy and create a lesion to break arrhythmogenic current paths in the cardiac tissue. As another example, a renal ablation procedure may involve the insertion of a catheter having an electrode at its distal end into a renal artery in order to complete a circumferential lesion in the artery in order to denervate the artery for the treatment of hypertension.

In such procedures, a reference electrode is typically provided and may be attached to the skin of the patient or by means of a second catheter. RF current is applied to the tip electrode of the ablating catheter, and current flows through the media that surrounds it, i.e., blood and tissue, toward the reference electrode. The distribution of current depends on the amount of electrode surface in contact with the tissue as compared to blood, which has a higher conductivity than the tissue. Heating of the tissue occurs due to its electrical resistance. The tissue is heated sufficiently to cause cellular destruction in the target tissue resulting in formation of a lesion which is electrically non-conductive. The lesion may be formed in tissue contacting the electrode or in adjacent tissue. During this process, heating of the electrode also occurs as a result of conduction from the heated tissue to the electrode itself.

Correspondingly, irrigation of the ablation catheter may provide many benefits including cooling of the electrode and tissue to prevent overheating of tissue that can otherwise cause the formation of char and coagulum and even steam pops. Therefore, an irrigated ablation catheter may include one or more temperature sensors, such as thermocouples, thermistors or the like, to assess tissue temperature during an ablation procedure for avoiding such adverse occurrences. It is desirable that the sensed temperature accurately reflects the real temperature of the tissue and not merely tissue temperature which has been biased by the cooling irrigation fluid from the catheter. Moreover, an irrigated ablation catheter may alternatively or in addition include electrical sensors for multiple purposes, including measuring impedance to help determine lesion size, depth and transmurality, performing mapping functions or assessing tissue contact with the RF electrode.

Further, the distal end of an irrigated ablation catheter is subject to significant spatial and design constraints. Since the catheter gains access via an intravascular route, the overall diameter is limited and must be sufficiently flexible to navigate the tortuous anatomy. There must also be an irrigation conduit system to supply the cooling fluid. The distal end also needs to accommodate the above noted RF electrode, temperature sensors and electrical sensors, and the associated electrical connections as well as other functional components that may be included, such as contact force sensor systems, safety wires or other structures.

Accordingly, it would be desirable to provide an irrigated ablation catheter that has one or more temperature and/or electrical sensors positioned at the distal end. It is also desirable to reduce interference between such elements and the irrigation system. For example, it would be desirable to provide the sensors in a manner that increases the surface area of the RF electrode exposed to the irrigation fluid. Likewise, it would be desirable to provide the sensors in a manner that reduces the effect of the irrigation fluid on the measurements. As will be described in the following materials, this disclosure satisfies these and other needs.

SUMMARY

The present disclosure is directed to a catheter having an elongated body, an electrode mounted at a distal end of the elongated body, wherein the electrode is configured as a shell defining an interior space, a plurality of irrigation apertures formed in the shell and communicating with the interior space, an insert disposed within the interior space having a plurality of protrusions configured to mate with a corresponding plurality of orifices in the shell of the electrode, wherein each protrusion extends at least flush with an exterior surface of the electrode and has a port communicating with at least one interior lumen in the insert, a plurality of sensors, wherein each sensor is disposed within one of the ports of the protrusions and a support which forms a fluid tight seal with a proximal end of the electrode and engages a proximal end of the insert to stabilize the insert against rotational motion.

In one aspect, the insert may have at least one longitudinally extending arm with at least one protrusion. Further, the at least one arm may have an interior lumen in communication the port of the at least one protrusion. Still further, the at least one arm may have a plurality of protrusions, such that the interior lumen of the at least one arm is in communication with a plurality of ports. As desired, at least one guide tube may be provided to extend from a through-hole in the support to the interior lumen of the at least one arm.

In one aspect, each protrusion may have a shoulder positioned radially outwards from a surface of the arm, such that the shoulder engages an interior surface of the electrode surrounding the orifice. A minimum separation may be provided between the insert and an interior surface of the electrode, wherein the minimum separation is defined by a distance from the surface of the arm and the shoulder.

In one aspect, the insert may have a plurality of arms. Further, at least one passageway may be provided between the plurality of arms to allow circulation of irrigation fluid within the interior space.

In one aspect, the insert may be formed by an outer portion and an inner portion and wherein the outer portion and the inner portion mate to form the at least one interior lumen. The inner portion may support the outer portion against inward deflection.

In one aspect, at least some of the plurality of sensors may be temperature sensors. In another aspect, at least some of the plurality of sensors may be electrical sensors. Alternatively or in addition, at least one of the plurality of sensors may be a combined temperature and electrical sensor.

This disclosure is also directed to a method for the ablation of a portion of tissue of a patient by an operator. One suitable method includes inserting a catheter into the patient, wherein the catheter has an elongated body, an electrode mounted at a distal end of the elongated body, wherein the electrode is configured as a shell defining an interior space, a plurality of irrigation apertures formed in the shell and communicating with the interior space, an insert disposed within the interior space having a plurality of protrusions configured to mate with a corresponding plurality of orifices in the shell of the electrode, wherein each protrusion extends at least flush with an exterior surface of the electrode and has a port communicating with at least one interior lumen in the insert, a plurality of sensors, wherein each sensor is disposed within one of the ports of the protrusions and a support which forms a fluid tight seal with a proximal end of the electrode and engages a proximal end of the insert to stabilize the insert against rotational motion, then connecting the catheter to a system controller capable of receiving signals from the plurality of sensors and delivering power to the electrode and subsequently controlling the power to the electrode to ablate tissue.

In one aspect, power to the electrode to ablate tissue may be controlled based at least in part on measurements from the plurality of sensors.

In one aspect, irrigation fluid may be delivered to the interior space based at least in part on measurements from the plurality of sensors.

In one aspect, contact of the electrode with tissue may be distinguished from contact of the electrode with blood based at least in part on measurements from the plurality of sensors.

In one aspect, a degree of contact of the electrode with tissue may be estimated based at least in part on measurements from the plurality of sensors.

In one aspect, movement of the electrode during ablation may be determined based at least in part on measurements from the plurality of sensors.

DETAILED DESCRIPTION

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

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

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

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

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

Finally, as used in this specification and the appended claims, the singular forms “a, “an” and “the” include plural referents unless the content clearly dictates otherwise.

As illustrated inFIG. 1, the present disclosure includes irrigated ablation catheter10with a distal tip section that includes electrode12adapted for contact with target tissue. Catheter10according to the disclosed embodiments comprises an elongated body that includes an insertion shaft or catheter body14having a longitudinal axis, and an intermediate section16distal of the catheter body that optionally may be uni- or bi-directionally deflectable off-axis from the catheter body as indicated. Proximal of catheter body14is control handle18that allows an operator to maneuver the catheter, including by deflecting intermediate section14when a steerable embodiment is employed. For example, control handle18may include deflection knob20that is pivoted in a clockwise or counterclockwise direction for deflection in the respective direction. In other embodiments, other steerable designs may be employed, such as the control handles for manipulating multiple control wires as described, for example, in U.S. Pat. Nos. 6,468,260, 6,500,167, and 6,522,933 and U.S. patent application Ser. No. 12/960,286, filed Dec. 3, 2010, the entire disclosures of which are incorporated herein by reference.

Catheter body14is flexible, i.e., bendable, but substantially non-compressible along its length and may be of any suitable construction and made of any suitable material. In one aspect, an outer wall made of polyurethane or PEBAX may have an imbedded braided mesh of stainless steel or the like, as is generally known in the art, to increase torsional stiffness of catheter body14so that, when the control handle20is rotated, the intermediate section16will rotate in a corresponding manner. Depending upon the intended use, the outer diameter of catheter body14may be approximately 8 french, and in some embodiments, may be 7 french. Likewise the thickness of the outer wall of catheter body14may be thin enough so that a central lumen may accommodate any desired wires, cables and/or tubes, as will be described in further detail below. The useful length of the catheter, i.e., that portion that can be inserted into the body may vary as desired. In exemplary embodiments, the useful length may range from about 110 cm to about 120 cm. The length of the intermediate section16may correspond to a relatively small portion of the useful length, such as from about 3.5 cm to about 10 cm, and in some embodiments, from about 5 cm to about 6.5 cm.

Details regarding one embodiment of the distal tip of catheter10are illustrated inFIGS. 2-5. Referring now toFIG. 2, electrode12is configured as an elongated, generally cylindrical portion22and an atraumatic dome-shaped portion24at the distal end. The shell of electrode12defines an interior cavity that is in fluid communication with a lumen extending the length of catheter body14to supply irrigation fluid. A plurality of irrigation apertures26are distributed substantially evenly across the surface of electrode12, through which fluid entering and filling the cavity may exit to outside of the electrode12, to provide cooling of electrode12and the environment adjacent electrode12as desired. The shell of electrode12may be made of any suitable electrically-conductive material, such as palladium, platinum, gold, iridium and combinations and alloys thereof, including, Pd/Pt (e.g., 80% Palladium/20% Platinum) and Pt/Ir (e.g., 90% Platinum/10% Iridium).

Disposed within electrode12is insert28, schematically shown in phantom, and configured to position a plurality of sensors at desired locations with respect to electrode12. Insert28has multiple protrusions30that align with sensor orifices32formed in electrode12. Each protrusion30has a port34configured to receive a sensor (not shown in this view). Insert28may be formed from any suitable material having appropriate electrical and thermal insulating properties, such as PEEK. The number of protrusions30may correspond to the number of sensors being employed. In this embodiment, three proximal protrusions are radially spaced by approximately 120 degrees about cylindrical portion22and three distal protrusions are radially spaced by approximately 120 degrees about dome-shaped portion24. This allows insert28to have a substantially triangular configuration, such that protrusions30are positioned at the apexes of the insert. In other embodiments, other suitable configurations may be employed. Protrusions30may be sized to either extend beyond or to be flush with the shell of electrode12as desired. For example, protrusions30extend from the shell a distance ranging from 0.05-0.3 mm and in one embodiment may extend between about 0.07 and 0.13 mm.

In one aspect, insert28may be configured to exhibit reduced contact with electrode12. For example, in the embodiment shown, insert28contacts electrode12only through protrusions30. Accordingly, a minimum separation36may be maintained between the body of insert28and the inner surface of electrode12. As will be appreciated, this facilitates circulation and even distribution of irrigation fluid, that may be supplied through lumen38(shown in phantom), as well as reducing interference with the exit of the irrigation fluid through apertures26. Additionally, passageways40formed in insert28may also facilitate irrigation.

Additional details regarding insert28are depicted inFIG. 3. In this view, electrode12has been removed to help show aspects of insert28. As can be seen, protrusions30include annular shoulders42configured to engage the inner surface of electrode12. Shoulders42may have a surface that is complimentary to the cylindrical portion22or dome-shaped portion24of electrode12as appropriate. The width of shoulders42may be defined by the difference between the diameter of a base portion44and the diameter of inner portion46. The diameter of inner portion46is sized to mate with sensor orifices32(shown inFIG. 2) in electrode12. Further, the depth of inner portion12, together with the thickness of the shell of electrode12results in protrusions30that either extend outward from or are flush with the outer surface of electrode12. Similarly, annular shoulder42extends radially outward from the surface of insert28, such that the depth of base portion44establishes the minimum separation36shown inFIG. 2between the inner surface of electrode12and surface48on the body of insert28.

In this embodiment, insert28includes three longitudinally extending arms50, each having a hollow interior portion that communicates with ports34to allow routing of leads and wires to sensors52. Arms50are connected at distal crown portion54. Passageways40as described above may be formed between arms50as well as by a central opening in crown portion54. Depending on the intended use and the number of sensors being provided, the configuration of insert28may be adapted as desired, such as by featuring two or four arms, for example. In one aspect, each arm50may include at least two protrusions30to accommodate at least two sensors, such as one proximal and one distal.

Sensors52may be any combination of temperature sensors, e.g., thermistor, thermocouple, fluoroptic probe, and the like, or electrical sensors, e.g., micro-electrodes. Any temperature sensor junctions located at or near the end of protrusions30and may be potted with a thermally conductive adhesive. Any wires or leads associated with sensors52may be routed through arms50and ports34as appropriate. As will be appreciated, this configuration isolates sensors52from electrode12and the irrigation fluid. In one aspect, insert28serves to thermally insulate sensors52. Accordingly, a more accurate measurement of tissue and environmental temperature may be obtained by reducing biasing from electrode12or the circulating irrigation fluid. In another aspect, insert28also serves to electrically insulate sensors52to allow more accurate measurement. Similarly, any wires and/or leads are also thermally and electrically insulated, as well as being sealed against corrosion from the irrigation fluid. In one aspect, each sensor52positioned by a respective protrusion30may be configured to sense a plurality of measurements. For example, one or more sensors52may function both as a micro-thermistor and a micro-electrode. According to one embodiment, thermistor wires as well as an electrode lead wire may be connected to a shell cap electrode of sensor52. Each wire may be isolated from each other by any suitable technique, such as by employing a suitable electrically nonconductive and non-thermally insulative material to fill the interior of arm50after placement of sensor52.

Insert28is stabilized within electrode12by support54, which includes a disc-shaped base56and a distally projecting key58. Base56may have a diameter corresponding to the inner diameter of electrode12and may be secured in any suitable manner, such as by welding60. Key58is configured to fit within recess62of insert28, formed by the proximal portions of arms50, to stabilize insert28against axial rotation and possible displacement of sensors52. Support54may provide a fluid tight seal with electrode12while routing leads and wires associated with electrode12and sensors52and irrigation fluid from lumens extending through catheter body14. For example, central conduit64may be in communication with lumen38(shown inFIG. 2), to conduct irrigation fluid to passageways40, for circulation within the interior of electrode12and eventual exit through apertures26. As shown inFIG. 5below, through-holes in support54may align with the interior of arms50to accommodate passage of wires to sensors52. Support54may also include one or more radial conduits66(one shown inFIG. 3) to accommodate leads for energizing electrode12, leads for position sensors, a safety wire to prevent loss of the distal end of catheter10, or other suitable purposes. Support54may be formed of any suitable electrically- and thermally-conductive material, such as palladium, platinum, gold, iridium and combinations and alloys thereof, including, Pd/Pt (e.g., 80% Palladium/20% Platinum) and Pt/Ir (e.g., 90% Platinum/10% Iridium).

Turning now toFIG. 4, an axial cross sectional view taken along line A-A indicated inFIG. 2is shown. The inner surface of electrode12defines irrigation reservoir68, which may be supplied with irrigation fluid through conduit64. Proximal portions70of arms50are positioned apart from the interior surface of electrode12by minimum separation36, defined by the depth of base portion44of protrusions30as described above. In this embodiment, proximal portions70do not have the hollow interior, which is formed distally. Rather, proximal portions70receive guide tubes72and direct them towards the interiors of arms50as shown below in the context ofFIG. 5. Guide tubes72generally extend from through-holes in support54to the interiors of arms50to seal, insulate and/or protect wires74which connect sensors52. Guide tubes72may be formed of any suitable material that is fluid-tight, electrically-nonconductive, thermally-insulating, and sufficiently flexible, e.g., polyimide, to form a thin-walled tubing.FIG. 4also illustrates the cooperation between recess62(schematically represented by dashed lines) and key58of support54to stabilize against axial rotation. Key58also may engage proximal portions70to prevent or reduce deflection inwards of arms50.

As noted above, support54may include one or more radial conduits66as desired. In this embodiment, one conduit66receives RF coil76used to energize electrode12. Other conduits66may be used for any suitable purpose, including routing and/or anchoring safety wire78to facilitate retrieval of the electrode assembly or other distal portions of catheter10should they become detached during a procedure. Safety wire78may be formed from Vectran™ or other suitable materials. In other embodiments, one or more of radial conduits66may accommodate electromagnetic position sensors that may be used in conjunction with a mapping system to aid visualization of the placement of the distal end of catheter10within a patient's anatomy and/or a force or contact sensing system. Details regarding such aspects may be found in U.S. patent application Ser. Nos. 11/868,733 and 13/424,783, both of which are incorporated herein by reference in their entirety.

Further details of one embodiment of the distal tip of catheter10are shown inFIG. 5, which is a longitudinal cross-sectional view taken at line B-B indicated inFIG. 4. As described above, electrode12may be secured to disc-shaped portion56of support54. Insert28is positioned within the interior of electrode12, with protrusions30mating with sensor orifices32. Inner portion46of protrusion30extends through orifice32, while shoulder42engages the inner surface of electrode12. As described above, the surfaces of arms50may be recessed as defined by the depth of base portion44to maintain spacing between insert28and electrode12, thereby improving exposure to irrigation fluid. Guide tube72extends between interior lumen80of arm50and through-hole82of support54to route wires74from sensor52(only distal sensor52is shown for clarity, with the sensor removed from proximal port34). Wires and leads84may similarly be routed through radial conduit66to couple RF coil76. In this embodiment, safety wire78may extend through and be anchored to support54. Alternatively, safety wire78may be anchored in a suitable manner to insert28.

A different embodiment according to the techniques of this disclosure is schematically depicted inFIG. 6. In a similar manner toFIG. 3, electrode12has been removed to show details regarding insert90and support92. Insert90may be formed from outer portion94and inner portion96. In a similar manner to the other disclosed embodiments, outer portion94has a plurality of protrusions30, each having a port34to accommodate a sensor (not shown in this view, but may incorporate any of the features described above). Outer portion94may include longitudinally extending arms98, each having one or more protrusions30, and inner portion96may have corresponding longitudinally extending arms100. After outer portion94is positioned within electrode12, inner portion96may be fit to prevent inward deflection of arms98. In one aspect, outer arms98may be somewhat flexible to facilitate manufacture, so that the arms may be biased inwards when positioned within electrode12and then allowed to return to a native configuration when protrusions30are properly aligned with sensor orifices32in electrode12, as described above. As shown, this embodiment includes three radial protrusions and three distal protrusions, respectively spaced radially at about 120 degrees with respect to each other. Each protrusion30on one arm98may communicate with an interior lumen102(one shown in phantom), formed when inner portion96is mated with outer portion94.

Support92may include disc-shaped portion104to be secured to electrode12and key106to stabilize insert90against rotation. Guide tubes108may extend through support92to the respective interior lumens102. Central conduit110may deliver irrigation fluid to the interior space defined by electrode12. In this embodiment, the surfaces of arms98are configured to rest against the interior surface of electrode12. Accordingly, contact between insert90is confined to longitudinal regions adjacent protrusions30, leaving substantial portions of the interior surface of electrode12exposed to irrigation fluid. In other embodiments, protrusions30may include shoulders as described above to increase exposure of the interior surface of electrode12. Further, spacing between each pair of arms98and100facilitates circulation of irrigation fluid within the interior of electrode12. As in the other embodiments of this disclosure, insert90may be formed from a suitable electrically- and thermally-insulative material, to help increase the accuracy of sensors disposed within ports34. Support92and electrode12to be used in this embodiment may be formed from a suitable electrically- and thermally-conductive material, such as palladium, platinum, gold, iridium and combinations and alloys thereof as described above.

An axial cross-sectional view of the embodiment shown inFIG. 6, taken along line C-C, is depicted asFIG. 7. At least a portion of interior lumen102may be formed by complimentary surfaces of outer arm98and inner arm100as shown. As discussed above, portions of key106fit between the proximal ends of arm pairs98and100to stabilize insert90against rotational motion.

According to the techniques of this disclosure, protrusions30may be used to provide catheter10with multiple sensors52. In one aspect, each sensor may measure temperature and electrical characteristics as described above, to allow for direct monitoring of micro ECG signals and/or micro impedance values using each sensor52. As will be appreciated, use of either, or both, ECG and impedance provide the ability to determine the contacting tissue at the location of each sensor and help distinguish between blood and tissue. This information may be utilized to confirm sufficient tissue coupling prior to delivery of RF ablation. This may be employed alternatively or in addition to the use of contact force sensors. Additionally, monitoring of electrical feedback from a plurality of sensors52distributed across electrode12may allow for estimation of a degree of contact between electrode12and tissue. For example, the measurements may be used to estimate the percentage of the surface of electrode12that is coupled with tissue. In turn, this may be used to better characterize the efficacy of RF delivery by determining what portion of the energy is delivered to tissue as compared to the surrounding blood.

In another aspect, the array of sensors52according to the techniques of this disclosure may provide improved temperature response to facilitate determination of catheter movement. As will be appreciated, dragging catheter10along tissue may result in frequent rise and fall of temperature response from tissue contacting sensors52. For example, ablations at a first position followed by movement to a new location may correspond to temperature increase during RF delivery followed by an abrupt decrease in interface temperature at the time of movement, and then by a temperature increase when RF delivery occurs at the new location. Consequently, the ability to quickly detect catheter movement using sensed temperature in this manner may allow for lesion assessment algorithms to “reset” mid ablation and account for detected movement.

In comparison to conventional RF ablation catheters, the techniques of this disclosure represent notable benefits. Prior to ablation, tissue and blood are at a similar temperature preventing use of temperature sensors from being utilized to determine contact, or more specifically areas of an electrode in contact. Contact force catheters are capable of demonstrating contact with tissue but do not provide an indication as to how much of the electrode is in contact with tissue. Further, such conventional contact force technologies may provide information regarding the contact with tissue. However, they do not provide an indication of movement during RF delivery by using the temperature sensing described above. The use of protrusions30to accommodate multiple sensors52provides sufficient resolution and response time to indicate ablation site movement.

Use of catheter10in an ablation procedure may follow techniques known to those of skill in the art.FIG. 8is a schematic, pictorial illustration of a system200for renal and/or cardiac catheterization and ablation, in accordance with an embodiment of the present invention. System200may be based, for example, on the CARTO™ mapping systems, produced by Biosense Webster Inc. (Diamond Bar, Calif.) and/or SmartAblate or nMarq RF generators. This system comprises an invasive probe in the form of catheter10and a control and/or ablation console202. An operator204, such as a cardiologist, electrophysiologist or interventional radiologist, inserts ablation catheter10into and through the body of a patient206, such as through a femoral or radial access approach, so that a distal end of catheter10, in particular, electrode12, engages tissue at a desired location or locations, such as a chamber of heart208of patient206. Catheter10is typically connected by a suitable connector at its proximal end to console202. Console202comprises a RF generator208, which supplies high-frequency electrical energy via the catheter for ablating tissue210at the locations engaged by electrode12.

Console202may also use magnetic position sensing to determine position coordinates of the distal end of catheter10inside the body of the patient206. For this purpose, a driver circuit in console202drives field generators to generate magnetic fields within the body of patient206. Typically, the field generators comprise coils, which are placed below the patient's torso at known positions external to the patient. These coils generate magnetic fields in a predefined working volume that contains the area of interest. A magnetic field sensor within distal end of catheter10, such as position sensor78, generates electrical signals in response to these magnetic fields. A signal processor in console202may process these signals in order to determine the position coordinates of the distal end, typically including both location and orientation coordinates. This method of position sensing is implemented in the above-mentioned CARTO system and is described in detail in U.S. Pat. Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612 and 6,332,089, in PCT Patent Publication WO 96/05768, and in U.S. Patent Application Publications 2002/0065455 A1, 2003/0120150 A1 and 2004/0068178 A1, whose disclosures are all incorporated herein by reference.

Console202may include system controller212, comprising a processing unit216communicating with a memory214, wherein is stored software for operation of system200. Controller212may be an industry standard personal computer comprising a general purpose computer processing unit. However, in some embodiments, at least some of the functions of the controller are performed using custom designed application specific integrated circuits (ASICs) or a field programmable gate array (FPGA). Controller212is typically operated by the operator204using suitable input peripherals and a graphic user interface (GUI)218which enable the operator to set parameters of the system200. GUI218typically also displays results of the procedure to the operator. The software in memory214may be downloaded to the controller in electronic form, over a network, for example. Alternatively or additionally, the software may be provided on non-transitory tangible media such as optical, magnetic or electronic storage media. In some embodiments, one or more position sensors may send signals to console202to provide an indication of the pressure on electrode12. Signals from wires74may be provided to system controller212to obtain measurements from sensors52. Such signals may be used to provide impedance and/or ECG readings at the location corresponding to sensor52. Similarly, such signals may be used to provide a temperature reading at the location of sensor52.

Typically, during an ablation, heat is generated by the RF energy in the tissue of the patient to effect the ablation and some of this heat is reflected to the electrode12causing coagulation at and around the electrode. System200irrigates this region through irrigation apertures26and the rate of flow of irrigation is controlled by irrigation module220and the power (RF energy) sent to electrode12is controlled by ablation module222. As noted above, system controller212may use electrical and thermal characteristics measured by the plurality of sensors52to characterize aspects of the ablation process. For example, measurements from sensors52may be used to determine the contacting tissue at the location of each sensor and help distinguish between blood and tissue. Further, the percentage of the surface of electrode12that is coupled with tissue may be estimated. As another example, measurements from sensors52may help determine movement of electrode12during an ablation. Still further, information from sensors52may be used to determine the lesion size and depth. Details regarding this aspect may be found in U.S. patent application Ser. No. 13/113,159, entitled “Monitoring Tissue Temperature Using an Irrigated Catheter” the teachings of which is hereby incorporated by reference in its entirety. As yet another example, sensors52may also provide intracardiac electrocardiograms to system controller212, to be used for determining when the tissue site being ablated is no longer conducting arrhythmogenic currents.

Described herein are certain exemplary embodiments. However, one skilled in the art that pertains to the present embodiments will understand that the principles of this disclosure can be extended easily with appropriate modifications to other applications.