FIELD OF THE INVENTION

[001] The present invention relates to medical devices, particularly to an electrosurgical expandable member having one or more electrodes printed on an outer surface of the same. BACKGROUND

[002] Hypertension is a leading cause of cardiovascular morbidity and mortality worldwide. At present, a significant number of hypertensive patients have resistant hypertension. The sympathetic nervous system is a well-known contributor to the pathophysiology of resistant hypertension. The blocking of the sympathetic nervous system by renal denervation (ablation of sympathetic nerve present on the wall of a renal artery) has emerged as an effective procedure to treat resistant hypertension.

[003] The renal denervation is an endovascular catheter based ablation of sympathetic nerves using different (radiofrequency/ ultrasound etc.) radiations. In this ablation procedure, radiation is transferred to a target site (sympathetic nerves) through electrodes present on an expandable member of the catheter. During the ablation procedure, sometimes the nerves other than the target site like vagus or some surrounding tissues come under the radiation while in some cases the target site is left un-ablated. Further, if the time taken to ablate the target site is long then it can also adversely affect the performance of the ablation procedure. The same scenario might occure in the treatment of other diseases like cancer and diabetes etc. SUMMARY

[004] The invention discloses a radiofrequency ablation system which may be used to treat for example, medication resistant hypertension, diabetes, cancer, etc. The expandable member placed on the distal end of the ablation system denervates the sympathetic nerves by passing a radio frequency into the entire length and circumference of body passageways. The expandable member is made up of a non-conductive material. At least a pair of spiral shaped bipolar electrodes and at least one thermocouple is printed at a fixed distance on an outer surface of the expandable member. The process of printing electrodes on to the expandable member includes ethanol washing, drying, fixture treatment, conductor layering, curing conductor layer, Nickle (Ni) layering, curing Ni layer, overcoat layering and curing overcoat layer in succession. Saline is filled inside the expandable member to cool down the pair of bipolar electrodes. [005] In an embodiment, the invention can be implemented for the treatment of the high blood pressure, asthma, etc. through ablation in renal artery and bronchioles respectively.

BRIEF DESCRIPTION OF DRAWINGS

[006] While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.

[007] FIG. 1 illustrates an exploded (element wise) side view of the catheter assembly with an inflated expandable member in accordance with an embodiment of the present disclosure.

[008] FIG. 2 depicts a scaled view of an electrode assembly and thermocouple printing pattern on the expandable member in accordance with an embodiment of the present disclosure.

[009] FIG. 3 depicts a cross-sectional view of printed layers of the electrode assembly and thermocouples in accordance with an embodiment of the present disclosure. [0010] FIG. 4 illustrates a flow chart depicting step by step process of printing the expandable member in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0011] The following description should be read with reference to the drawings, which are not necessarily to scale, wherein like reference numerals indicate like elements throughout the several views. The detailed description and drawings are intended to illustrate but not limit the claimed invention. Those skilled in the art will recognize that the various elements described and/or shown may be arranged in various combinations and configurations without departing from the scope of the disclosure. The detailed description and drawings illustrate example embodiments of the claimed invention. [0012] All numeric values are herein assumed to be modified by the term "about," whether or not explicitly indicated. The term "about", in the context of numeric values, generally refe rs to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the term "about" may include numbers that are rounded to the nearest significant figure. Other uses of the term "about" (i.e., in a context other than numeric values) may be assumed to have their ordinary and customary definition(s), as understood from and consistent with the context of the specification, unless otherwise specified.

[0013] 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 used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

[0014] It is noted that references in the specification to "an embodiment", "some embodiments", "other embodiments", etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it would be within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described, unless clearly stated to the contrary. That is, the various individual elements described below, even if not explicitly shown in a particular combination, are nevertheless contemplated as being combinable or arrangable with each other to form other additional embodiments or to complement and/or enrich the described embodiment(s), as would be understood by one of ordinary skill in the art. [0015] FIG. 1 depicts a two-dimensional representation of a catheter assembly 100. The catheter assembly 100 comprises a catheter shaft 10, an inner tube 30, a guidewire tube 50, an expandable member 70 with printed electrode assembly 90, a three port hub 130, a male connecter 150, a plurality of strain relievers 170a and 170b and RF cables (not shown).

[0016] The catheter shaft 10 has a proximal end 12 and a distal end 14. The catheter shaft 10 has an elongated body with a lumen i.e. outer lumen 16. The outer lumen 16 extends from the proximal end 12 to the distal end 14 of the catheter shaft 10. The outer lumen 16 provides a passage for components like the inner tube 30, RF cables, etc. Several diameters of the catheter shaft 10 may be used as per the diameters of body passageways. The catheter shaft 10 can be made of any insulating material including without limitation Polyurethane (Pellethane). The three port hub 130 and the expandable member 70 are attached to the proximal end 12 and the distal end 14 of the catheter shaft 10 respectively. [0017] The inner tube 30 has a proximal end 32, a distal end 34 and an inner lumen 36. The inner tube 30 has an elongated body. The proximal end 32 may be coupled to a saline port 140 of the three port hub 130. The coupling may be for example, by way of fixed arrangement or glued arrangement between the two. The distal end 34 may be fixedly coupled to the proximal neck 74 of the expandable member 70. The inner lumen 36 runs across the entire length of the inner tube 30. The inner lumen 36 is provided to supply saline to the expandable member 70 and for the passage of guidewire tube 50. The inner tube 30 can be made of without limitation a non-conductive material.

[0018] The guide wire tube 50 has a proximal end 52, a distal end 54 and a lumen 56. The guide wire tube 50 has an elongated body. The proximal end 52 may be fixedly coupled to the tubing port 138 of the three port hub 130 (see below). Similarly, the distal end 54 may be fixedly coupled to an atraumatic tip at the end of the distal neck 74 of the expandable member 70. A guide wire (not shown) may be passed through the lumen 56 and from the tubing port 138 to a treatment site. The guide wire tube 50 can be made of without limitation a non-conductive material.

[0019] The expandable member 70 is provided to deliver RF energy to the target side. The expandable member 70 has a predefined length and may have a proximal neck 72, a distal neck 74, and a mid- portion 76. The proximal neck 72 and the distal neck 74 may be mounted on the distal portion of the guide wire tube 50. An atraumatic tip may be provided at the distal neck 74 for safe and smooth passage of the expandable member 70 into the body passageways. The expandable member 70 may be made up of a non-conductive material like plastic, rubber etc. Diameter of the expandable member 70 may be selected as per the application where the catheter assembly 100 is to be deployed. For example, the diameter of the expandable member 70 may range from 5mm to 7mm. In delivery configuration, the expandable member 70 is in collapsed state. However, upon injection of saline in the member 70 through the inner tube 30, it is inflated. The expandable member 70 maybe a balloon.

[0020] The expandable member 70 contains an electrode assembly 90 and one or more thermocouples which may be printed on its surface. The material used for printing may be a conductive ink, for example, Sliver or Nickel. In an embodiment, the printing pattern may be spiral in shape and distributed throughout the entire length of the expandable member 70. For example, printing pattern may be commence from the proximal neck 72 and extend to the distal end of the mid portion 76 of the expandable member 70. Further, the distance between two electrodes and/or thermocouples is fixed. This has certain advantages. For example, in RF treatments, variation in the gap between bipolar electrodes can vary RF application to the tissue therefore standardized fixed distance may reduce the chances of uneven treatment.

[0021] In an embodiment, the electrodes of the electrode assembly 90 have a bipolar configuration. The bipolar electrode configuration is advantageous over the monopolar electrode configuration because in bipolar system, current directly returns to a return electrode from an active electrode. Therefore, in bipolar configuration, minimal current is passed through the patient body in contrast to the monopolar electrode system where the return ground electrode is placed on the patient and current flows back to ground through patient body. Moreover, in the bipolar configuration, tissue penetration is also improved due to the presence of both the electrodes at the same place.

[0022] The three port hub 130 has a proximal end 132 and a distal end 134. The three ports of the three port hub 130 may be provided as three different openi ngs at the proximal end 132. The openings may be for example, a cable passage port 136, a tubing port 138 and a saline port 140. The cable passage port 136 may provide passage to the RF cables. The guide wire may be introduced into the lumen 56 of the guide wire tube 50 by the tubing port 138. The saline port 140 may be used to inject saline or a conductive fluid from a saline source (not shown) to the inner tube 30. The three port hub 130 can be made of without limitation a polymer or non- conductive material. [0023] The plurality of strain relievers may be optional attachments and include a first strain reliever 170a and a second strain reliever 170b. The strain relievers may provide strain minimization caused by the insertion of the catheter assembly 100 into the body passageway. The first strain reliever 170a may be attached to the proximal end 132 of the three port hub 130 and allow passage of the insulation tube (not shown) till the proximal end 132 of the three port hub 130. The second strain reliever 170b may be attached to the distal end 134 of the three port hub 130 and allow passage of the proximal end 12 of the catheter shaft 10 till the distal end 134 of the three port hub 130. The strain relievers can be made of without limitation a polymer or non-conductive material.

[0024] The male connector 150 may be attached to the proximal end 132 of the three port hub 130 by an insulating tube. The male connector 150 has a proximal end 152 and a distal end 154. The proximal end 152 of the male connector 150 may be attached to the energy source (not shown). The distal end 154 of the male connector 150 may be coupled to the proximal end 12 of the catheter shaft via cable passage port 136. The male connector 150 is provided to supply RF energy from an energy source (not shown) via RF cables to the electrode assembly 90. The RF cables extend from the male connector 150 and through the entire length of the outer lumen 16 to the electrode assembly 90. The male connector 150 can be made of without limitation any non-conductive material.

[0025] In use, the catheter assembly 100 may be advanced through a blood vessel to a position adjacent to a target tissue (e.g., within a renal artery). In some embodiments, the target tissue may be one or more renal nerves disposed about the renal artery. When suitably positioned, expandable member 70 may be expanded from a collapsed delivery configuration to an expanded configuration. Due to the expanded configuration of the expandable member, the first electrode 92 is positioned against the wall of the blood vessel. The first electrode 92 may be then activated. Ablation energy (RF) may be transmitted from the first electrode 92 to the target tissue (where renal nerves may be ablated, modulated, or otherwise impacted), and back through the second electrode 94 in a bipolar configuration. [0026] FIG. 2a illustrates a scaled image of the expandable member 70 depicting the printing pattern of electrode assembly 90 and thermocouples 120. The electrode assembly 90 and/or thermocouples 120 may be printed in the form of traces on the outer surface of the expandable member 70. The printed traces may extend to the entire/partial outer surface of the expandable member 70 by acquiring at least one complete rotation (spiral shaped circumferential loop) around it. Complete rotation may be of 360°. The traces may include a first electrode 92, a second electrode 94, and at least one thermocouple 120. In an embodiment, the bipolar electrodes 90 (namely, the first electrode 92 and second electrode 94) and thermocouple 120 traces may be printed as parallel traces at a fixed distance from each other. In an alternate embodiment, the traces of bipolar electrodes 90 and thermocouple 120 may be printed as vertical lines parallel to each other. The electrodes transfer heat at a location within the tissue surrounding the body passageway without damaging the wall of the body passageway. The spiral orientation is preferred to avoid an increased risk of stenosis.

[0027] The traces of the thermocouple 120 may be printed in between the first 92 and second 94 electrodes of the electrode assembly 90. In an embodiment depicted in FIG 2b, the traces of the thermocouple 120 may include a first thermocouple trace 120a, a second thermocouple trace 120b, a third thermocouple trace 120c and a fourth thermocouple 120d. For example, the first and second thermocouple traces (120a, 120b) may couple to form a thermocouple TCI while the first and third thermocouple traces (120a, 120c) couple to form a thermocouple TC2. Similarly, the first thermocouple trace 120a may couple with the fourth thermocouple trace 120d to form a thermocouple TC3.

[0028] The first 92 and second electrodes 94 may run in parallel orientation on the opposite exterior ends of the electrode assembly 90. Different length and width parameters may be used for printing electrode assembly 90 and thermocouples 120 on to the expandable member 70. For instance, as non-limiting examples, the overall length (G) of the electrode assembly 90 from proximal neck 72 of the expandable member 70 to the distal end of the mid portion 76 of the expandable member 70 may range from approximately 26mm to 29mm. Further, the length (B) of the mid portion 76 the electrode assembly 90 may range from 20mm to 23mm. The length of proximal minimum neck (H) and distal minimum neck (L) may be of 7mm. Similarly, the width (K) of first and second electrode traces 92, 94 may follow a range of 0.50mm to 0.70mm having a standard deviation of 0.05mm. The width of thermocouple (L) traces 120 may vary from 0.20 to 0.25 with a standard deviation of 0.05mm. Likewise, the pitch (M) between two nearby traces (electrode 92 and first thermocouple 120a trace; electrode 94 and fourth thermocouple 120d trace; first 120a and second thermocouple 120b trace; second 120b and third thermocouple 120c trace; third 120b and fourth thermocouple 120d trace) may be 0.24mm and 0.40mm with a standard deviation of 0.05mm. The pitch (N) between the two electrodes 92 and 94 may fall in 2 mm - 3mm range with a standard deviation of 0.10mm. [0029] FIG. 3 depicts a cross-sectional view of printed layers of the electrode assembly 90 and thermocouples 120. The electrode assembly 90 may be constructed as a trace having a plurality of layers. Such layers may be continuous or non-continuous, i.e., made up of discrete portions. In an embodiment, the bottom layer is a base conductive layer 310, a second layer 320 on top of the bottom layer is of Ni and the final layer is an overcoat layer 330. [0030] FIG. 4 illustrates a flow chart depicting step by step process of printing the expandable member 70. The printing process starts by mounting the expandable member 70 onto a writing mandrel. The expandable member 70 is washed with ethanol or other cleaning agent and then dried by for example, wiping from a soft cloth at step 410. The outer surface of the expandable member 70 is then treated with an automatic treatment fixture at step 420. A base conductive layer 310 is written onto the treated outer surface of the expandable member 70 at step 430. The conductive layer 310 is then cured at step 440 and a second layer 320 of Ni/Ag is then applied onto the base conductive layer 310 at step 450. The Ni/Ag layer 320 is cured at step 460 and an overcoat layer 330 may be applied onto the Ni/Ag layer 320 at step 470. At last, the overcoat layer 330 is cured at step 480 and resistance of the electrode assembly 90 and thermocouple 120 may be measured.

[0031] Teachings of the above disclosure find applications in the treatment of hypertension by placing the catheter assembly into a renal artery, in the treatment of asthma by placing the catheter assembly into the bronchioles and ablating them, etc. Via the teachings of the present disclosure, chances of sympathetic nerves being un-ablated, chances of affecting vagus nerve and other organs, etc. are eliminated.

[0032] While the devices and methods described herein are discussed relative to renal nerve ablation and/or modulation, it is contemplated that the devices and methods may be used in other treatment locations and/or applications where nerve modulation and/or other tissue modulation including heating, activation, blocking, disrupting, or ablation are desired, such as, but not limited to: blood vessels, urinary vessels, or in other tissues via trocar and cannula access. For example, the devices and methods described herein can be applied to treatment of cancer and diabetes. In addition to that the catheter can be used in hyperplastic tissue ablation, cardiac ablation, pulmonary vein isolation, pulmonary vein ablation, tumor ablation, benign prostatic hyperplasia therapy, nerve excitation or blocking or ablation, modulation of muscle activity, hyperthermia or other warming of tissues, etc.