MEDICAL DEVICE COMPRISING A BALLOON-STENT ASSEMBLY AND METHODS OF USING THE SAME

The present invention provides a medical device with a balloon-stent assembly comprising a stent, a balloon within the stent, and an ablation member. The medical device can be useful for a combined procedure of balloon angioplasty, radiofrequency ablation, and stent placement. The invention exhibits numerous merits such as simpler and precise operation, and a single device for multiple applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application expressly claims the benefit of priority under the Paris Convention based on Chinese Application No. 201710077036.3, filed on Feb. 13, 2018, the entire disclosures of which is incorporated herein by reference.

Not applicable.

NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

REFERENCE TO AN APPENDIX SUBMITTED ON COMPACT DISC

Not applicable.

FIELD OF THE INVENTION

The present invention generally relates to a medical device comprising a balloon or a balloon-stent assembly and methods of using the same. Although the invention will be illustrated, explained and exemplified by embodiments in vascular and interventional radiology (VIR), it should be appreciated that the present invention can also be applied to other minimally invasive image-guided diagnosis and treatment of disease.

BACKGROUND OF THE INVENTION

Stenosis and stricture are an abnormal narrowing in a blood vessel or other tubular organ. For stenosis, the narrowing is caused by lesion that reduces the space of lumen (e.g. atherosclerosis). For stricture, the narrowing is caused by contraction of smooth muscle, e.g. achalasia, and prinzmetal angina. One way to solve the problem is angioplasty, also known as balloon angioplasty and percutaneous transluminal angioplasty (PTA). Balloon angioplasty is a minimally invasive, endovascular procedure to widen narrowed or obstructed arteries or veins, typically to treat arterial atherosclerosis. A deflated balloon attached to a catheter is passed over a guide-wire into the narrowed vessel and then inflated to a fixed size. The balloon forces expansion of the blood vessel and the surrounding muscular wall, allowing an improved blood flow. A stent may be inserted at the time of ballooning to ensure the vessel remains open, and the balloon is then deflated and withdrawn.

Take coronary angioplasty as an example. The therapeutic procedure can treat the stenotic (narrowed) coronary arteries of the heart found in coronary heart disease. These stenotic segments may be caused by the buildup of cholesterol-laden plaques from atherosclerosis. In a percutaneous coronary intervention (PCI), the blood stream is accessed through the femoral or radial artery, and then the procedure uses coronary catheterization to visualize the blood vessels on X-ray imaging. After this, an interventional cardiologist can perform a coronary angioplasty, using a balloon catheter as described above. Metallic scaffolds such as coronary stents may then be deployed within the coronary artery segment to maintain wide luminal patency. Coronary stents are designed as permanent endoluminal prostheses that can seal dissections, create a predictably large initial segment, and prevent early recoil and late vascular remodeling. Drug-eluting stents (DESs) elute medication to reduce restenosis (the recurrence of abnormal narrowing of a blood vessel) within the stents. Coronary stents are used in most interventional procedures. Stent-assisted coronary intervention has replaced coronary artery bypass graft (CABG) as the most common revascularization procedure in patients with coronary artery disease (CAD) and is used in patients with multi-vessel disease and complex coronary anatomy.

As mentioned above, restenosis is the recurrence of stenosis after a procedure. The main cause of restenosis following angioplasty procedures is due to vessel wall trauma created during the procedure. Evidence has shown that scar tissue forms as endothelial cells that line the inner wall of the blood vessel re-generate in response to the vessel wall injury created during angioplasty.

In radiofrequency ablation (RFA), part of the electrical conduction system of the heart, tumor or other dysfunctional tissue is ablated using the heat generated from medium frequency alternating current (in the range of 350-500 kHz). When the RF energy is delivered via catheter, it is called radiofrequency catheter ablation. One advantage of radio frequency current over low frequency AC and DC pulses is that it does not directly stimulate nerves or heart muscle and therefore can often be used without the need for general anesthetic. Another advantage is that it is very specific for treating the desired tissue without significant collateral damage.

Advantageously, the present invention provides a medical device comprising a balloon or a balloon-stent assembly and methods of using the device, which exhibit numerous improvements over three traditional areas combined: balloon angioplasty, radiofrequency ablation, and stent placement.

SUMMARY OF THE INVENTION

One aspect of the present invention provides a medical device having a balloon-stent assembly. The assembly includes a stent, a balloon within the stent, and an ablation member.

Another aspect of the invention provides a medical device comprising a balloon, an electrode, and a pedestal. The pedestal is located between (and contacts both) the electrode and an external surface of the balloon to increase a height of the electrode above said external surface, i.e. height along the normal direction of said external surface.

Still another aspect of the invention provides a medical process comprising providing a medical device comprising a balloon and an electrode; maneuvering the balloon and the electrode near a tissue; inflating or deflating the balloon so that the electrode contacts or presses the tissue with a controllable contacting pressure; and ablating the tissue only when the contacting pressure falls within a predetermined range. In many embodiments, inflating the balloon and ablating the tissue are carried out simultaneously.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It is apparent, however, to one skilled in the art that the present invention may be practiced without these specific details or with an equivalent arrangement.

Where a numerical range is disclosed herein, unless otherwise specified, such range is continuous, inclusive of both the minimum and maximum values of the range as well as every value between such minimum and maximum values. Still further, where a range refers to integers, only the integers from the minimum value to and including the maximum value of such range are included. In addition, where multiple ranges are provided to describe a feature or characteristic, such ranges can be combined.

It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the invention. For example, when an element is referred to as being “on”, “connected to”, or “coupled to” another element, it can be directly on, connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly on”, “directly connected to”, or “directly coupled to” another element, there are no intervening elements present.

With reference toFIG. 1, a medical device100(e.g. a catheter) includes a balloon-stent assembly101. Assembly101includes a stent110, a balloon120within the stent110, and an ablation member139. Stent110may be any suitable metal or plastic tube to be inserted into the lumen of an anatomic vessel or duct and to keep the passageway open. Typically, stent110has a stent longitudinal axis and a suitable diameter, and a length along the stent longitudinal axis. Made of metals such as stainless steel alloys, platinum iridium alloys, and cobalt chrome alloy, metallic stents110may be a scaffold for providing a structure with sufficient radial strength (crush resistance) to address recoil and hold the vessel open over time. Stents110may be made of wire(s), coils, braids, a sheet, and/or tubular bodies. Balloon expandable stents in assembly101may be made of patterned non-degradable metallic tubes, wires, or sheet with limited inward recoil, high strength (crush resistance or crush force), and limited axial shortening upon expansion. Examples of stent110include expandable coronary, vascular and biliary stents, and simple plastic stents. In preferred embodiments, stent110is a coronary stent for coronary angioplasty, such as a bare-metal stent, a drug-eluting stent, a bio-absorbable stent, a dual-therapy stent (combination of both drug and bioengineered stent), or a covered stent. However, it should be appreciated that stent110may be used in other applications such as peripheral artery angioplasty (carotid, iliac, and femoral arteries). Because of the external compression and mechanical forces, flexible stent materials such as nitinol are used in a majority of peripheral stent placements. Stent110may also be an esophageal stent for palliative treatment of advanced esophageal cancer, and other stents for different purposes.

In balloon angioplasty, the balloon120merely by itself can be involved in three events: plaque fracture, compression of the plaque, and stretching of the vessel wall. These lead to expansion of the external elastic lumina and axial plaque redistribution along the length of the vessel. The balloon120may have suitable diameter and length sized to fit within the lumen of a vessel. As will be shown inFIGS. 17 and 18, various shapes of balloon120include, but not limited to, a cylindrical shape, a spherical shape, an oval shape, a conical shape, a stepped shape, a tapered shape and a dog bone shape. The balloon ends can have shapes including, but not limited to, a conical sharp corner end, a conical radius corner end, an offset neck end, a spherical end and a square end. The balloon120may be made from material such as a polyamide, polyethylene terephthalate (PET), polyurethane, composites, engineered nylons and equivalent materials.

The ablation member139may be an electrode130(e.g. in vivo RF electrode) on an external surface of the balloon120, an ultrasonic wave generator132inside the balloon120, and/or an electrode130on an external surface of the stent110. In preferred embodiments of the invention, electrode130is a radiofrequency ablation (RFA) electrode. RFA is a known local treatment using a catheter to destroy tissue with heat generated by medium frequency alternating currents.

When electrode130is placed on an external surface of the balloon120, it may be optionally comprised of a conductive material which is flexible and generally conforms to an outer surface of the balloon120during expansion of the balloon. Another electrode (in vitro RF electrode, not shown) is placed on the patient's skin to form a current loop with in vivo RF electrode130. Alternatively or additionally, another in vivo RF electrode (not shown) is placed on an external surface of the balloon120to form a current loop with in vivo RF electrode130. The electrodes are positioned so that electrical current flows between the electrodes and through the target area.

The electrodes130may be made of suitable electrically conductive material including but not limited stainless steel, gold, silver and other metals including shape-memory materials such as nitinol. Nitinol is an alloy with super-elastic characteristics which enables it to return to a pre-determined expanded shape upon release from a constrained position.

In an example, medical device100may be a cutting wire balloon catheter, to “score” a stenotic lesion in a controlled and precise manner. Scoring a lesion can lead to less procedural vessel trauma, endothelial cell re-growth and re-stenosis.

Alternatively or additionally, an ultrasonic wave generator132may be used as the ablation member139. Microwave ablation (MWA) can destroy tissue with heat generated by microwaves. MWA uses electromagnetic waves in the microwave energy spectrum (300 MHz to 300 GHz) to produce tissue-heating effects. MWA can be performed using a single MW antenna or a cluster of three to achieve a greater ablation volume. Examples of MWA systems use either a 915 MHz generator or a 2450 MHz generator. The MW antennas used are straight applicators with active tips ranging in lengths from 0.6 to 4.0 cm. The antennas may be internally cooled with either room-temperature fluid or carbon dioxide to reduce conductive heating and to prevent possible thermal damage. MWA is generally used for the treatment and/or palliation of tissues such as solid tumors in patients. The oscillation of polar molecules produces frictional heating, ultimately generating tissue necrosis within solid tumors. Tumor temperatures during ablation can be measured with a separate thermal couple. Tumors may be treated to over 60° C. to achieve coagulation necrosis.

With reference toFIG. 2, assembly101may include a breakable tether140that links the stent110and the balloon120. During or after the stent110is properly placed, the doctor can pull/push the balloon120with the breakable tether140with a proper force, so as to break tether140apart without disrupting the position of already-placed stent110. To facilitate the “breaking”, breakable tether140may include a breakable point such as a weakened point141or a snap fastener142that is easier to break than any other points along tether140. The length from point141or snap fastener142to stent110along tether140may be less than 30%, 20%, 10% or 5% of the total length of tether140.

With reference toFIG. 3, the stent110may include an electrode extender111that functions as the ablation member139. Electrode130contacts the electrode extender111from inside the stent110. Electrode130electrically communicates to a tissue190outside the stent110through the electrode extender111. In an embodiment, the electrode extender11has an outward blade for cutting into or nailing into, and therefore anchoring to, the tissue190. The blade may have a hook to reinforce its anchoring to the tissue190. To facilitate a proper contact or engagement between electrode130and the electrode extender111, electrode130may be designed as a pyramid or a cone in which the smaller end is pointing to extender111. The base of extender111may have a cavity (like a negative pyramid or cone) for receiving the pyramid-shaped or cone-shaped electrode130. As a result, electrode130will easily slide into the cavity during the procedure and mate or engage to extender111with a defined spatial interrelationship.

In an embodiment, tether140is used to link electrode130on the balloon and extender111, and to establish electrical communication between them.

With reference toFIG. 4, the stent110includes a radial opening118, which may be like a “mesh hole” of stent that is made of wires, coils, and braids. Electrode130can extend beyond the stent110, or protrudes out from the stent110, through the radial opening118to contact a tissue190outside the stent110.

With reference toFIG. 5, a pedestal131may be located between the electrode130and an external surface of the balloon120to increase a height of the electrode130above said external surface. Without pedestal131, the height of the electrode130per se may be for example 0.05 mm as measured from the balloon surface. With pedestal131, the height of the electrode130may be for example 0.05 mm-2 mm (preferably 0.05 mm-2 mm) as measured from the balloon surface. The pedestal131may be a pressure sensor, or a simple conductor. The shape of electrode130may be designed as a blade for cutting into and anchoring to a tissue. To reinforce the anchoring, the blade may have one or more hooks. A pressure sensor may be useful to monitor and control the pressure that is applied to for example the stenosis, when the surface of inflated balloon120is compressing the lesion, pushing it radially outward and widening or restoring the luminal diameter of the vessel.

In various embodiments of the invention, stent110may be excluded from medical device100. As a result, device100may include a balloon120, an electrode130, and a pedestal131such as a pressure sensor. Similarly, pedestal131is located between the electrode130and an external surface of the balloon120to increase a height of the electrode130above said external surface. In a preferred embodiment, electrode130is a blade for cutting into and anchoring to a tissue, and the blade has one or more hooks to reinforce the anchoring to the tissue.

An example of the medical device according to the present invention is any known balloon catheter, for inserting into a tissue lumen or a channel within a tubular tissue structure, such as a blood vessel (including an artery or a vein), a cavity within a hollow portion of an organ, such as an intestine, an oral canal, a heart, a kidney, or auditory canal.FIG. 6shows a balloon catheter for radiofrequency ablation, and well-known components in such a balloon catheter are shown in simplified form, omitted, or merely suggested, in order to avoid unnecessarily obscuring the present invention. With reference to the plan view ofFIG. 6, the balloon and electrode assembly is configured at the distal end of the catheter1. Catheter1includes a handle4, a flexible long tube or shaft2extending distally from handle4to an expandable and inflatable balloon10and terminating at catheter distal tip, which may be a front image sensor50secured with a distal end connector51. As known in the art, tube or shaft2may include a lumen, one or more layers coaxially surrounding the lumen, and electrically conducting wire(s) wedged between layers for delivering RF energy. Electrically conductive wire may be made of material such as nitinol or copper. Depending on use, the catheter may have a single lumen (a “monoluminal catheter”) or multiple lumens. A catheter with two lumens is “biluminal”, three “triluminal”. Up to 4 or 5 lumens may be used, allowing multiple drugs and devices to be delivered and monitored simultaneously. Therefore, tube or shaft2may include one or more lumens for e.g. insertion of a guidewire to assist in advancing the catheter to the target site. At least one of the lumens is configured to receive inflation media and pass such media to balloon10for its expansion.

Handle4may connect to one or more suitable accessary devices, such as a source of inflation media (e.g., air, saline, or contrast media). Handle4may include a port opening25in communication with tube2for the injection and aspiration of fluid (from a liquid/gas source a shown) to inflate and deflate the balloon10during use under the control of pressure control3. Balloon10may be coaxially arranged around tube2near the distal end and is shown in an expanded state. The balloon catheter1may be a rapid exchange or over-the-wire catheter and made of any suitable biocompatible material. For example, handle4may include a side-arm extension on with an opening to allow the insertion of a guidewire to facilitate tracking through the vessel. Pull wire5(e.g. for controlling image sensor50) and push/pull button41may be constructed with the handle4. Electrode20and pressure sensor30may be placed on the surface of balloon10(either side-by-side or stacked as shown inFIG. 5), and thermal couple40is placed inside balloon10for measuring temperature. Thermal couple40is preferably placed near the RF electrode, either on the external or internal surface of the balloon.

With reference toFIG. 7, balloon10may be dressed or jacketed with a stent21consisting of stent wires211which can be maneuvered (e.g. expanded or shrunk) by adjusting wire158. Stent21may be self-expandable. Alternatively, stent21may not be self-expandable (inactive), but it can be expanded by the expanding balloon10. The balloon-stent assembly is placed in a vessel lumen which is narrowed due to hyperplasia (hypergenesis), neoplasia or benign tumor, and hypertrophy. Hyperplasia or hypergenesis is an increase in the amount of organic tissue that results from cell proliferation. Hyperplasia is a common preneoplastic response to stimulus, and the cells resemble normal cells but are increased in numbers, while the adaptive cell change in hypertrophy is an increase in the size of cells. Take smooth muscle hyperplasia as an example. Human arteries and veins are comprised of three layers: the intima which is the thinnest and innermost layer; the media which is the thickest and middle layer; and an outer adventitia layer comprised of connective tissue. The medial layer is comprised mainly of smooth muscle cells which play a prominent role in re-stenosis of previously treated vessels. In reaction to the vessel wall trauma associated with previous balloon angioplasty, the smooth muscle cells within the medial layer proliferate causing a thickening of the overall vessel wall and consequently, a reduction in the luminal diameter of the vessel.

Stent21may be a basket-type stent and expandable and shrinkable, and may be attached to balloon10. Alternatively, stent21may be detachable or separable from balloon10. As shown inFIG. 8, stent21may be attached to balloon10or detached from balloon10.

With reference toFIG. 9A, a few electrodes20are adhered to surface of balloon10, and wires for delivering ablation energy to electrodes are bundled into proximal end connector52. Stent21contacts at least some of electrodes20. As shown in the enlarged view ofFIG. 9B, a portion of stent wire211becomes electrode extender212for ablating nearby tissue, and they work together like130and111as shown inFIG. 3.

The medical device of the invention may be a stented or non-stented balloon catheter. As shown inFIG. 12andFIG. 13, electrodes20(with stent21or without stent21) may be built like cutting blades23. In an embodiment, cutting blades23may be tapered, with a sharp tip distal from the balloon10and a large base proximal to the balloon10. The base of electrode blade23may have a shape (e.g. triangle) conforming to the shape of the radial opening118(e.g. triangle). When the base of23is smaller than the radial opening118and when the balloon10is inflated, the entire electrode blade23can protrude through radial opening118without contacting/cutting stent wire211. When the base of23is bigger than the radial opening118and when the balloon10is inflated, the electrode blade23will be stuck by radial opening118at its base, and 1, 2, 3 or 4 blades of electrode23may be forced to cut into stent wire211. This is particular useful for stent wire211with a chemically inert sealing skin211a, a metal core211c, and a drug releasing shell211bbetween211aand211b. Blades of electrode23may cut skin211a, and make one or more openings on skin211a. Drug releasing shell211bcan then start to release pharmaceuticals through the one or more openings on skin211a. These pharmaceuticals can be any known drugs used in drug-eluting stents (DES), for example, to suppress growth of scar tissue along the inner vessel wall over an extended period of time. For example, anti-restenosis drug may be selected from the group consisting of paclitaxel and vasculant. The drug is slowly released or eluted, thus fighting fibrosis and reducing the occurrence and extent of re-stenosis when compared with bare stents. As compared to traditional “drug-eluting stents (DES)” that are coated in medication without skin211a, the drug releasing from the DES of the invention as shown inFIG. 13is even slower, due to a limited number exiting openings on skin211a.

It should be appreciated that ablation member139may be an ultrasonic wave generator80within balloon10, as shown inFIG. 14. Energy from ultrasonic wave generator80may be employed to accomplish denervation of the nerve tissues on a target blood vessel. Energy from ultrasonic wave generator80may also be employed to accomplish ablation of smooth muscle hyperplasia in a blood vessel, as shown inFIG. 15.

FIGS. 16-18show various shapes of balloon10/120. Fold balloons have folds in the compressed state of the balloon that open at least partially when expanding the balloon. For example, the inflatable body of balloon10/120can have a cylindrical morphology, a cone shaped morphology or dog-bone shaped morphology, an “onion”-shaped morphology, or a barrel-like morphology. In another embodiment, the inflatable body may have a compound shape. For example, the inflatable body may be rounded in shape in certain portions, and include at least one portion that is flattened. In another example, the inflatable body may be configured as a flattened stretchable portion that can be expanded or collapsed. In an implementation, such a flattened portion of the inflatable body may be deployed to make substantially full contact with a portion of a tissue, e.g., as part of a tissue lumen.

As show inFIGS. 17-18, balloon10/120in expanded state may have a few ridges and a few valleys, and electrode20/130may be placed on tips of the ridges.

The medical process of the invention may first involve diagnosing a human subject suffering from disease such as coronary artery disease and specifically identifying a target area of an artery in the subject which is partially blocked by plaque. A procedure is then planned whereby blockage in the target area is moved or removed from the artery so as to increase blood flow through the target area of the artery.

Various embodiments of the invention provide a medical process comprising these steps: providing a medical device100comprising a balloon120and an electrode130(as described above); maneuvering the balloon120and the electrode130near a target tissue; inflating or deflating the balloon120so that the electrode130contacts the tissue with a controllable contacting pressure; and ablating the tissue only when the contacting pressure falls within a predetermined range. In an example, inflating and ablating are carried out simultaneously, particularly when the contacting pressure is set as a specific value (not a range), in which situation the ongoing ablation keeps decreasing the contacting pressure, which in turn triggers continuous inflating of the balloon to meet the pressure requirement.

The method may be used in, for example, a central venous catheter (CVC) procedure. CVS can be placed in veins in the neck (internal jugular vein), chest (subclavian vein or axillary vein), groin (femoral vein), or through veins in the arms. Before insertion, the patient is first assessed by reviewing relevant labs and indication for CVC placement, in order to minimize risks and complications of the procedure. Next, the area of skin over the planned insertion site is cleaned. A local anesthetic is applied if necessary. The location of the vein is identified by landmarks or with the use of a small ultrasound device. A hollow needle is advanced through the skin until blood is aspirated. The color of the blood and the rate of its flow help distinguish it from arterial blood (suggesting that an artery has been accidentally punctured). A blunt guide wire is passed through the needle, and then the needle is removed. A dilating device may be passed over the guide wire to expand the tract. Finally, the central line itself is then passed over the guide wire, which is then removed. All the lumens of the line are aspirated (to ensure that they are all positioned inside the vein) and flushed with either saline or heparin. Electromagnetic tracking can be used to verify tip placement and provide guidance during insertion. The catheter is held in place by an adhesive dressing, suture, or staple which is covered by an occlusive dressing. Regular flushing with saline or a heparin-containing solution keeps the line open and prevents blood clots. Certain lines are impregnated with antibiotics, silver-containing substances (specifically silver sulfadiazine) and/or chlorhexidine to reduce infection risk.

The method may be used in, for example, percutaneous transluminal angioplasty (PTCA). Such minimally invasive procedure is designed to open blocked coronary arteries, allowing blood to circulate unobstructed to the heart muscle. The procedure begins with the injection of local anesthesia into the groin area and putting a needle into the femoral artery. A guide wire is placed through the needle and the needle is removed. An introducer is then placed over the guide wire, after which the wire is removed. A different sized guide wire is then put in its place. Next, a long narrow tube called a diagnostic catheter is advanced through the introducer over the guide wire, into the blood vessel. This catheter is then guided to the aorta and the guide wire is removed. Once the catheter is placed in the opening (or ostium) of one the coronary arteries, a contrast dye may be injected and an x-ray may be taken. If a treatable blockage is noted, the first catheter is exchanged for a guiding catheter. Once the guiding catheter is in place, a guide wire is advanced across the blockage, and then the balloon catheter is advanced to the blockage site. The balloon is inflated for a few seconds to compress the blockage against the artery wall.

The method may also be used in, for example, RFA or rhizotomy to treat severe chronic pain in e.g. the lower (lumbar) back, as shown inFIG. 14. Radio frequency waves are used to produce heat on specifically identified nerves surrounding the facet joints on either side of the lumbar spine. By generating heat around the nerve, the nerve gets ablated thus destroying its ability to transmit signals to the brain. The nerves to be ablated are identified through injections of local anesthesia (such as lidocaine) prior to the RFA procedure. If the local anesthesia injections provide temporary pain relief, then RFA is performed on the nerve(s) that responded well to the injections.

In some embodiments, the medical process of the invention includes steps of: providing a medical device100with a balloon-stent assembly101comprising a stent110, a balloon120within the stent110, and an electrode130(as described above); maneuvering the balloon-stent assembly101near a target tissue in a first location with a first orientation; inflating or deflating the balloon120so that the electrode130contacts the tissue with a controllable contacting pressure; ablating the tissue only when the contacting pressure falls within a predetermined range; withdrawing the balloon120from inside the stent110and leaving the stent110in said first location (or rotating the balloon120to a second orientation at the first location); maneuvering the balloon120to a tissue in a second location; and ablating the tissue in said second location. In an example, inflating and ablating are carried out simultaneously, particularly when the contacting pressure is set as a specific value (not a range), in which situation the ongoing ablation keeps decreasing the contacting pressure, which in turn triggers continuous inflating of the balloon to meet the pressure requirement. When tether140is present, the method will further include a step of breaking the tether when withdrawing the balloon120from inside the stent110.

With reference to the flow chart ofFIG. 10, a specific medical process using the medical device as described above and characterized by “constant balloon pressure” may include the following steps: at1001—start; at1002—set up balloon pressure range (e.g. 3-30 atmospheres (ATM), 5-7 ATM such as 6 ATM, or 4-6 ATM), temperature, impedance, resistance, power, and ablation time etc. The RFA is typically carried out using a voltage and a current with defined ranges over a defined period of time. At1003—inflate the balloon after it is inserted to and placed at a desired location. At1004—check if the balloon pressure is within the range; if yes, then goes to1005to activate the ablation process; if no, then go back to1003and continue to inflate the balloon.

After1005, recheck at1006if the balloon pressure is still within the range; if the balloon pressure at1006is higher than the range, then goes to1010to deflate the balloon and then proceed to1006again to recheck if the balloon pressure falls down into the range; if the balloon pressure at1006is within the range, then move to1007to determine if ablation time is satisfied; if not, then go back to1005and continue the ablation; if yes, then move forward to1008to determine if the ablation goal has been accomplished (e.g. by examining real-time X-ray imaging); if not, then move to1011and deflate (and/or withdraw) the balloon, and then at1012adjust the ablation to a new site/location or a new orientation at the same location. At the new site/location or new orientation, the process starts from1003. If at1008the ablation goal has been accomplished, the medical process is then ended at1009.

With reference to the flow chart ofFIG. 11, another specific medical process using the medical device as described above and characterized by “variable balloon pressure” or “increasing balloon pressure” may include the following steps: at2001—start; at2002—inflate the balloon to an initial pressure M0after it is inserted to and placed at a desired location; at2003—activate the ablation process; determine at2004if ablation time t1is satisfied; if t1is not satisfied, then move back to2003and continue the ablation; if t1is satisfied, then move to2005and inflate the balloon to pressure Mn, wherein Mn=Mn-1+N, N is the incremental increase of the balloon pressure and Mnshould not be higher than a predetermined pressure threshold Mmaxfor safety. N may be a constant value; or N may be decreasing as corresponding n is increasing. At2006, determine if Mn=Mmax. If Mnremains lower than Mmax, then move back to2003and continue the ablation; if Mnreaches Mmax, then determine whether the process needs to adjust the ablation to a new site/location or a new orientation at the same location. If it needs, then go to2010to adjust the ablation to a new site/location or new orientation, and start over from2002. If it does not need, then at2008deflate the balloon and withdraw it from the site, and the medical process is then ended at2009.

For multiple electrodes20, they may experience different contacting pressures. In this situation, each electrode may be individually controlled by the system to release RF energy when it is ready.

An advantage of the invention is that, with a single catheter of the invention, the doctor can treat vessels or vessel segments with a big range of diameters, for example from 4 mm to 12 mm, avoiding frequent change of catheters of different sizes.

When implemented in software or firmware, various elements of the systems described herein are essentially the code segments or executable instructions that, when executed by one or more processor devices, cause the host computing system to perform the various tasks. In certain embodiments, the program or code segments are stored in a tangible processor-readable medium, which may include any medium that can store or transfer information. Examples of suitable forms of non-transitory and processor-readable media include an electronic circuit, a semiconductor memory device, a ROM, a flash memory, an erasable ROM (EROM), a floppy diskette, a CD-ROM, an optical disk, a hard disk, or the like.

In the foregoing specification, embodiments of the present invention have been described with reference to numerous specific details that may vary from implementation to implementation. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the invention, and what is intended by the applicant to be the scope of the invention, is the literal and equivalent scope of the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction.