Method for treatment of aneurysms

A method is disclosed for treating an aneurysm or vascular defect by cooling a target tissue region of the aneurysm or vascular defect to a temperature below body temperature for a preselected time period. The method entails thickening, strengthening, or increasing the density of a blood vessel wall by cooling the blood vessel wall with a cryogenically cooled device. The method also includes irradiating the inner wall of a blood vessel around an aneurysm or vascular defect with various forms of energy to delay or halt aneurysm or vascular defect formation. An energy-emitting element is disposed on the distal end portion of a catheter device to be disposed proximate the aneurysm. Various forms of energy, including visible light energy, laser light energy, ultrasound, microwave and radiofrequency sources may be used to irradiate and treat the aneurysm. In addition, the method may include irradiating a tissue site concomitantly with other treatments, including the delivery of vaso-occlusive compounds, mechanical intravascular devices, or an endovascular graft to the target tissue region.

FIELD OF THE INVENTION

The present invention relates to a method and device for treating vascular defects such as aneurysms, dissections, arterio-venous malformation and vulnerable plaque, and in particular, to a method involving the use of a catheter and thermo-cryogenic, electromagnetic, and ultrasonic energy sources concomitantly with an additional treatment to treat tissue.

BACKGROUND OF THE INVENTION

Aneurysms are distensions formed by the localized dilation of the wall of an artery, a vein, or the heart. An aneurysm balloons due to the pressure of blood flowing through an area weakened due to disease, injury, or congenital defect. A “true” or common aneurysm results from the formation of a sac by the arterial wall, or tunica media, which remains unbroken, and may be associated with atherosclerosis. In a “false” or dissecting aneurysm, usually caused by trauma, a fissure in the wall of a blood vessel allows blood to escape into surrounding tissues and form a clot.

Doctors typically monitor the inflammation and progression of aneurysms using devices known in the art such as MRI and CT scanners and by observation of known patient symptoms. Typically, however, early stage aneurysms do not warrant dangerous surgical procedures, even if minimally invasive, due to the associated morbidity risk. Accordingly, the doctors choose a “wait and see” approach. Because surgery for aneurysms is risky, the surgeon may wait for the aneurysm to expand to a certain size before operating, when the risk of complications exceeds the risk of surgery. Accordingly, it would be desirable to treat aneurysms upon early detection rather than wait until they progress to a stage that requires dangerous, expensive surgery, or become life-threatening conditions.

In addition to aneurysms, certain other vascular defects are of interest, such as a dissection. Vascular dissections are similar to aneurysms in that the vessel wall integrity is compromised. However a dissection consists of a laceration of a portion of the vessel wall. Both dissections and lacerations are associated risks stemming from arterial disease.

Therefore, it would be desirable to have a device, coupled with a minimally invasive method, to retard, arrest and even reverse, the processes that lead to vascular defects such as dissections or aneurysm formation, and arterio-venous malformation or vulnerable plaque.

SUMMARY OF THE INVENTION

A method for treating a vascular defect is disclosed. A catheter having an energy-transfer element is positioned and disposed proximate a target tissue region including the vascular defect. Energy is transferred between the energy-transfer element and the target tissue region. The energy may be emitted as a treatment energy from the energy-transfer element, and further directed to be in part absorbed by the target tissue region. The treatment energy may be any of the following group: visible light energy, laser light energy, ultrasonic periodic mechanical vibrational, or ultrasound, energy, and microwave or radiofrequency electromagnetic energy. Alternatively, the energy-transfer element is a heat-absorbing device, and heat is transferred from the target tissue region to the heat-absorbing device. The heat transfer element can include an expansion chamber, wherein a coolant is injected into the expansion chamber. In addition, the treatment method may include providing energy transfer paired with an additional treatment method, including drug delivery, the use of an implanted medical device, a biological filler material, or an endovascular graft.

In another embodiment, a method is provided for thickening, strengthening, or increasing the density of a blood vessel wall. A catheter is provided having an energy-transfer element. The catheter is positioned such that the energy-transfer element is disposed proximate the blood vessel wall. A flow of treatment energy is transferred between the energy-transfer element and the blood vessel wall.

In yet another embodiment, a method is provided for enhancing collagen production in blood vessels proximate a vascular defect. Collagen inducing growth factors are injected into a target tissue region proximate the vascular defect. A device having a discrete light energy-emitting element is provided. The element is disposed proximate to the target tissue region. The energy-emitting element is directed to emit light energy and to irradiate the target tissue region with said light energy. The collagen inducing growth factors are activated with the light energy.

In still yet another embodiment, a method is provided for cryotreating vulnerable plaque. The method provides for the treatment of plaque formed on an interior lumenal surface of a body or blood lumen. A cooling device is positioned at the interior lumenal surface at a point proximate to a plaque formation. The lumenal surface is cooled at the point proximate to the plaque formation to inhibit the progression of plaque formation in which the lumenal surface is cooled to a temperature of less than about zero degrees Celsius.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, a “vascular defect” shall mean an aneurysm, a dissection, or vulnerable plaque as further described and set forth herein. An aneurysm is typically characterized by a localized dilatation in a blood vessel, while a dissection occurs when a defect in the lining of a blood vessel allows an opening or tear to develop in the vessel wall.

Vascular or vulnerable plaque is typically caused by coronary artery disease, and involves the formation of plaque, a combination of cholesterol and cellular waste products that form on the interior wall of an artery. Eventually, the plaque deposit can develop a thin covering called a fibrous cap. With plaque progression, the vessel wall can experience inflammation, leading to the erosion of the fibrous cap. The erosion may cause the plaque cap to crack, allowing the underlying plaque elements to come in contact with the blood stream. Exposure of these elements to the blood stream can cause clot formation, leading to coronary artery occlusion, myocardial ischemia and infarction. This particular type of lipid-rich plaque, having active inflammation and the potential to erode the overlying fibrous cap, which in turn can lead to thrombosis and myocardial infarction is called unstable or vulnerable plaque.

Catheter based devices enable access to the weakened arterial wall around an aneurysm, a dissection or venerable plaque, are minimally invasive, and may be employed for a variety of diagnostic and therapeutic functions. Localized application of cold temperatures to the blood vessel wall may serve to strengthen and thicken the distended and dilated tissue of an aneurysm, and make such tissue layers increasingly dense, as well as inhibit the progression of plaque formation. Accordingly, by applying such cold, or cryotreatment, to the aneurysm, dissection or vulnerable plaque site, the aneurysm, dissection or vulnerable plaque may be effectively treated without major surgery.

FIG. 1illustrates a blood vessel and a device during a procedure for cryotreatment of an aneurysm. InFIG. 1, a balloon catheter, labelled generally as10, is disposed inside of a blood vessel11proximate to an aneurysm12. The balloon catheter10includes a flexible, expandable membrane or balloon13coupled to a catheter tube14, wherein the catheter10is guided to the desired treatment site via a guidewire15. In this procedure, the balloon catheter10is percutaneously inserted into the vasculature and advanced to the locus of the aneurysm12. The specific size and shape of the balloon13and catheter tube14may be determined a priori in order to best fit the targeted artery or blood vessel where an aneurysm has formed. The balloon13is thereby inflated to appose the inner walls of the blood vessel proximate the aneurysm12, so as to enable cryotreatment of the aneurysm12tissue.

However, contrary to conventional angioplasty procedures, the dilatation and apposition of the balloon13versus the inner walls of the aneurysm is not meant to dilate the blood vessel walls. Rather, the device employed in this procedure uses a balloon-tipped catheter configured to receive the flow of a coolant, or cryogenic fluid, therein. High-pressure coolant fluid is connected to the proximal section of the catheter tube14, which contains several tubes and lumens (not shown) adapted to contain the flow of coolant therein. The coolant used may be any stable working fluid capable of being compressed to high pressure, pumped though small diameter devices, and expanded to produce endothermic cooling at a desired location. Examples of such coolants are nitrogen, nitrous oxide, or any conventionally used refrigerant. The coolant may be in liquid, gaseous, or mixed phase form. The flow system inside of the catheter may be either closed loop, wherein the injected coolant is returned to the source for recycling and re-entry into the device, or open loop, wherein the coolant is pumped through the device only once, whereupon it exits outside the body and is discarded.

The coolant flows through the catheter tube14and is injected, generally along coolant flow lines F, into the balloon13at the distal tip of the catheter10, whereupon the balloon13expands as the coolant is both vaporized and expanded inside the balloon. The combined evaporation and expansion of the coolant creates endothermic cooling in the near field of the balloon13. The process is endothermic in that heat, or thermal energy, is absorbed by the balloon13, and flow of coolant therein, from the surrounding environment: the aneurysm and targeted tissue of the blood vessel wall which forms the aneurysm. This cooling draws heat from the adjacent aneurysm tissue in the coolant flow inside of balloon13, thereby cooling the aneurysm tissue to temperatures in the range of +20 to −20 degrees Centigrade.

The particular shape of the expanded balloon13may be predetermined by the use of a preformed balloon membrane, a memory retaining material, or other structural attribute wherein the expanded balloon13is configured to form a particular shape, yet also remain somewhat conformable. The balloon13may also be totally conformable, such that the expanded membrane fits to conform to the particular contours of the blood vessel wall of the aneurysm12, for optimal contact therewith.

Alternatively, the distal tip of the catheter10may also include multiple expandable membranes or chambers (not shown), wherein different injection fluids are pumped into separate chambers within a single membrane, or multiple outer membranes. One injection fluid may be used to expand a first chamber, while another cooling fluid may be used to create endothermic cooling in the same or another chamber, as discussed above.

Any tissue near or adjacent to the balloon and flow of coolant therein may be cooled to temperatures below body temperature. The duration of cooling may vary from 15 seconds to up to 20 minutes, depending on the application, and the particular aneurysm targeted. Part or the entire surface of the balloon may be specially treated or affixed with heat conductive elements to create a pattern of cooling on the tissue surfaces targeted. An example of such an endovascular balloon catheter used to cold treat tissues is disclosed in U.S. Pat. No. 6,283,959 B1, the entirety of which is incorporated herein by reference. The tissue forming the aneurysm12is thus cold-treated by the catheter device10, whereupon the balloon13is contracted or evacuated, and withdrawn from the treatment site.

The cryotreatment of aneurysm tissue in the prescribed time and temperature ranges discussed above may, among other effects, stimulate a tissue response which results in myointimal thickening of the blood vessel wall and anvential tissue. This thickening helps to minimize the incidence of aneurysm rupture, which can be fatal. Cryotreatment may also result in reparative regeneration of the endothelium, in addition to accelerated myointimal thickening. These overall effects serve to treat and possibly reverse the formation of an aneurysm, leading to significant therapeutic results.

Aneurysmal enlargement results in part from degradation of the extracellular matrix and other structural elements of the blood vessel wall. This in turn is related to an increased activity of proteolytic enzymes such as collagenase and elastase, resulting in destruction of collagen and elastin forming the blood vessel wall. Macrophages and inflammatory cells may also be sources of enzymes, which have a capacity to degrade all the major connective tissues forming the blood vessel wall, including collagen and elastin, all of which contribute to aneurysms. The application of cold temperatures to such tissues may slow or retard the action of such macrophages, proteolytic enzymes, thus diminishing the destruction of collagen and elastin that is vital to the structural integrity of the blood vessel wall. In such a way, cryotreatment may effectively treat aneurysms.

Furthermore, for large blood vessels such as the aorta, aneurysms also exhibit the synthesis and accumulation of new collagen and elastin in the expanding aorta. However, these newly synthesized proteins often lack the intricate fibrillar structure and mature cross-linking necessary to maintain the normal tensile strength of the cellular matrix of the aortic wall. Cryotreatment of such areas may show the ability to compensate for such an effect, allowing the enlarged aortic wall to retain its normal extra-cellular matrix characteristics. In a similar fashion, the application of the cryotreatment to vulnerable plaque sites reduces the inflammation of the blood vessel while increasing the collagen synthesis, to effectively treat vascular plaque.

In general, the balloon13as used for cryotreatment, is an apposition device, and not a dilatation device. Accordingly, the strength of materials forming the balloon13itself, as well as the fluid pressures therein, are generally not required to be as high as a conventional blood vessel-dilating angioplasty balloon.

The catheter10itself may also be combined with an injection element, wherein a therapeutic drug or medication is infused in the target area around the aneurysm12in conjunction with the use of the balloon13to effect cryotreatment.

In another procedure, a fixed diameter catheter device is used, as illustrated inFIG. 2.FIG. 2shows an endovascular catheter20disposed inside of a blood vessel21near an aneurysm22. The catheter20includes a catheter tube23having a cooling segment24disposed at its distal end portion. The catheter20may include one or more injection lumens26, as well as several tubes and lumens (not shown) adapted to contain the flow of coolant therein. Although the distal end of the catheter20is shown in a substantially linear or straight configuration, the distal tip can be configured or commanded to assume an annular or helical shape. The catheter20is percutaneously inserted into the vasculature and advanced to the aneurysm site22. A guidewire, rapid-exchange system, or other catheter positioning device may be employed to position the catheter tip at the desired location. Coolant is injected into the catheter20via injection lumen26, and flows through to the distal tip of the catheter, which contains the cooling segment24. The cooling segment24is any heat conductive element, which defines a closed volume expansion chamber25, wherein coolant may be expanded to low temperatures after it exits the injection lumen26. The coolant, which may be in mixed liquid or gaseous phase, is injected into the expansion chamber25, whereby it undergoes both evaporative cooling through a change in phase from liquid to gas, and expansive cooling through a Joule-Thomson throttling process, similar to the those thermodynamic changes discussed with respect to the balloon catheter device10ofFIG. 1. As with the balloon catheter device10embodiment above, these gas-dynamic processes are generally endothermic with respect to the surrounding environment, in that heat is drawn from the tissue forming the surrounding aneurysm22so as to cool such tissue to temperatures below normal human body temperature, and indeed below the freezing point of water and beyond. The strength of cooling may be controllably varied by the user by controlling the pressure and flow of coolant in the catheter device. The size and particular shape of the cooling segment24may be varied to best fit the contours of the particular aneurysm to be treated, such as a berry aneurysm in the brain, a saccular aortic aneurysm just above the heart, or a fusiform aneurysm in the lower aorta, as is illustrated inFIG. 1.

AlthoughFIGS. 1 and 2illustrate an approach to treating an aneurysm from within a blood vessel,FIG. 3shows another embodiment wherein an aneurysm can be approached from the exterior of a blood vessel. In these procedures, the device can be a fixed diameter catheter, a probe, an inflatable device, which is applied to the surface of the aneurysm, or even a fixed, compliant, or inflatable cuff which partially or completely encircles the vessel in the location of the aneurysm, as shown inFIG. 3.

FIG. 3illustrates a cryotreatment device30, externally disposed adjacent to or proximate a blood vessel31having an aneurysm32. The device30includes a coolant source element33having an expandable, inflatable membrane, such as the cuff34shown inFIG. 3. The cuff34may have a U-shape in order to conformably fit around one hemisphere of a rounded aneurysm32, as shown inFIG. 3. Alternatively, the cuff34may be highly compliant and conformable such that when apposed against an aneurysm of any shape, the outer surface of such cuff34conformably rests in contact with such surface and envelops a significant surface area of the aneurysm.

The device30includes at least one injection lumen (not shown) in the source element33to carry the flow of coolant into the interior of cuff34. The coolant may then be injected into the cuff34, such as along the flow lines F shown inFIG. 3. As with the balloon catheter device10shown inFIG. 1, the cuff34is inflatably expandable by the action of a gas or liquid which may include the coolant or a completely separate source. The cuff34may be a preformed balloon membrane, or may include a memory retaining material or other structural attribute wherein the expanded form is configured to form a particular shape, yet also remain somewhat conformable.

Once inflated, the cuff34is externally applied in proximity to, or in apposition against, the desired aneurysm treatment site, such as in the direction of arrows A shown inFIG. 3. The flow of coolant in the cuff34endothermically cools the target tissue of the aneurysm32, in accordance with the previous two embodiments of the present invention. The flow of coolant may result in the target tissue being cooled to a temperature between about 0° C. to about −200° C. This approach may be combined with conventional surgery to treat the aneurysm, wherein the cold treatment of the arterial wall is used with other treatment techniques and therapies.

In addition to the methods involving cryogenic thermal cooling, non-thermal energy sources may be used to treat the blood vessel wall proximate an aneurysm, including, among others, visible light energy of a particular wavelength, laser light energy, ultrasound, and microwave and radiofrequency electromagnetic energy. In addition to heat energy transferred by cooling, all such sources of “treatment” energy may have beneficial effects in counteracting the disorders of collagen and elastin synthesis characteristic of aneurysm formation, in addition to being able to create lesions and scar tissue within the walls of blood vessels such as the aorta.

FIG. 4illustrates a catheter40disposed inside a blood vessel11proximate an aneurysm12. The catheter40includes an energy-transfer device or element42disposed at its distal end portion43. As used herein, an “energy-transfer” device shall mean any device that transfers energy between the device and its environment, wherein energy may flow either to or from the device. In this sense, an energy-transfer device may be either an energy-emitting device or an energy-absorbing device. One example of an energy-absorbing device would be the catheter10with balloon13in the embodiment shown inFIG. 1, the catheter20with cooling segment24in the embodiment shown inFIG. 2, or the cryotreatment device30with source element33and cuff34in the embodiment shown inFIG. 3.

In the embodiment illustrated inFIG. 4, the energy-transfer device42includes (not shown) a suitable device for emitting energy (labelled inFIG. 4as dashed lines45) in the form of waves or particles flowing from the distal end portion43of catheter40towards the inner wall48of the blood vessel11proximate the aneurysm12. Upon contacting the inner wall48, the cellular structure of the blood vessel11absorbs the energy45, thereby triggering various therapeutic reactions and treating the aneurysm12.

FIG. 4illustrates the use of photodynamic visible light energy45to treat the aneurysm12. Such light energy may be anywhere in the visible range, having a wavelength of between 300 to 800 nanometers, or may be tuned to a particular frequency. Photodynamic light energy may be used in conjunction with various collagen inducing growth factors that are either systemically or locally injected into the vasculature and blood stream. When such light energy is thereafter used to irradiate the blood vessel11and aneurysm12, it triggers a reaction in the vasculature with the injected collagen inducing growth factors so as to delay or halt aneurysm formation. Examples of such collagen inducing growth factors are TGF-beta 1, which acts to regulate connective tissue growth factors. The particular wavelength of light, which may be used for such a purpose, depends on the penetration required and the particular photosensitivity. Light penetration in turn increases with increasing wavelength. One example of a wavelength suitable for the methods described herein is approximately 500 nanometers, although other wavelengths may be equally well suited.

In accordance with the preceding method,FIG. 5illustrates the use of a laser light emitting energy source52disposed at the distal end portion53of a catheter50introduced into a blood vessel11proximate aneurysm12. The laser light is emitted in the direction of one of the arrows54inFIG. 5, and thus may be used to target a specific localized region of tissue. The laser light emitting energy source52may be fitted with beam direction optics (not shown) to focus and steer the emitted beam in any direction around the distal end portion53of catheter50, as shown by the multi-directional arrows54. Alternatively, the emitted laser light may be optically directed, using prisms or other optical elements, to be emitted in a diffuse, spherical, or other non-linear three-dimensional waveform to impinge on larger areas of the interior of blood vessel11proximate aneurysm12. Thus, the laser light may be used to create both small, localized treatment areas as well as larger, circumferential lesions, as may be required.

Because laser light is easily tuned to a precise frequency, the light emitted54by the laser light emitting energy source52can be accurately tuned to trigger exactly the desired response in the cells of the blood vessel11near the aneurysm12. As illustrated byFIG. 5, the distal end portion53of the catheter50may be easily positioned around the interior of the blood vessel11, such that the emitted laser light54is accurately spatially positioned to affect a specific target region of the aneurysm12.

The entire process may utilize varying laser wavelengths to achieve varying results. Often the treatment desired is purely for biostimulus, involving effects, which have a lesser permanent effect on tissue. Other times the treatment desired is less mild and seeks to ablate tissue. Examples of the particular laser light wavelengths used for biostimulus are approximately 1,000 nanometers, while that used for ablation is in the neighborhood of approximately 1250 nanometers, as may be delivered by a YAG (Yttrium Aluminum Garnet) laser.

FIG. 6shows an alternative embodiment of the present invention, wherein a catheter60is disposed inside of a blood vessel11proximate an aneurysm12, having an energy-emitting element62disposed at the distal end portion64of said catheter60. In this embodiment, the energy-emitting element includes a device, which generates periodic mechanical vibrations in the form of sound waves66. Such sound waves66may be anywhere in the sonic, infrasonic, or ultrasonic range, both audible and non-audible. Although generally, ultrasonic energy is preferred to create the desired therapeutic effects on the aneurysm12. As with the preceding embodiments, the energy emitted by the energy-emitting element62propagates though the interior of the blood vessel, through any blood flow, which may be present (not shown) and impinges upon the aneurysm12. This in turn generates the desired therapeutic reactions in treating the aneurysm12.

FIG. 7illustrates still another embodiment of the present invention, wherein a catheter70having an energy-emitting element72disposed at its distal end portion74is introduced into a blood vessel11proximate an aneurysm12. In this embodiment, electromagnetic energy (as labelled by waves76inFIG. 7) is emitted from the energy-emitting element72to irradiate the inner wall48of the blood vessel11around the aneurysm12. The electromagnetic energy may take several forms and frequencies, including both microwave and radiofrequency waves.

All forms of energy as discussed herein trigger some thermal reactions with the blood flow inside the blood vessel11. In particular, radiofrequency (RF) waves significantly heat up the blood flow. As such, it is desirable to position the catheter70as closely as possible to the inner wall48of blood vessel11, as is illustrated inFIG. 8. In this fashion, the energy76emitted from the energy-emitting element72is better suited to irradiate the aneurysm12as desired. The use of microwave, ultrasound or laser light is advantageous over RF energy in that the former three forms of energy are not inhibited by blood flow, and may be readily conducted thereby.

Additionally, all of the foregoing methods may be equally applied to certain other vascular defects, including vascular dissections as well as aneurysms.FIG. 9illustrates a catheter device as in the previously shown embodiments disposed inside a vessel proximate a dissection. The catheter90, having a treatment tip section92is positioned inside the vessel93proximate a dissection95. The methods discussed hereinabove are thus applied to treat the tissue, or a tissue region, around and including the lacerated vessel wall of the dissection. The therapeutic effects of the methods disclosed herein apply in much the same manner as with other vascular defects such as aneurysms.

In addition, the foregoing energy-transfer methods involving cryogenic thermal cooling, visible light energy, laser light energy, ultrasound, and microwave and radiofrequency electromagnetic energy may be combined with other treatments for vascular defects, including the use of pharmaceutically active compounds, vaso-occlusive materials, as well as implanted medical devices such as coils, stents, or grafts. Such combined treatments may be delivered to an aneurysm region by a single medical device, or alternatively, through separate medical instruments. Furthermore, the treatments may be applied concurrently, sequentially, or cyclically within a predetermined time period.

FIG. 10shows a step of an alternative method of the present invention, wherein a catheter100is disposed inside of a blood vessel102proximate an aneurysm104. The catheter includes an energy-transfer element106disposed at the distal end portion and the energy-transfer element may employ any of the above-mentioned energies. In addition to treating the aneurysm tissue region through energy-transfer, the method further may include the dispersion of a vaso-occlusive or pharmaceutically active compound108within a close proximity of the aneurysm or vascular defect, such as through a series of apertures110in the catheter. A vaso-occlusive compound may include injectable fluids or suspensions, such as microfibrillar collagen, thrombogenic fluids, or polymeric compositions. After such introduction to a tissue site, the vaso-occlusive compounds form a substantially solid space-filling mass, which provides some relief of vessel wall pressure in the region of an aneurysm. Such agents are often introduced into the vasculature through a catheter and are known in the art. Alternatively, a pharmaceutically or biologically active compound may be introduced through the catheter to the region of the aneurysm, including, but not limited to anti-proliferative agents, anti-inflammatory agents, anti-mitotic agents, or anaesthetic agents.

FIG. 11illustrates a step of still another alternative method of the present invention, wherein a catheter112having an energy-transfer element114disposed at its distal end portion is introduced into a blood vessel116proximate an aneurysm118, where energy-transfer treatment may be provided in addition to the delivery of a mechanical intravascular device120. The mechanical device120may be delivered through a designated lumen122within the energy-transfer catheter, or through an additional medical device. A typical mechanical intravascular device is a wire coil or braid, which can be introduced through a catheter in a stretched linear form, which then assumes an irregular shape upon discharge of the device from the end of the catheter. The detached coil is intended to block or impede the flow path of blood into the aneurysm, resulting in the blood being forced past the defect. Moreover, implanted coils may enhance the formation of a clot within the aneurysm, thereby aiding in the prevention of rupture and providing for the eventual sealing of the aneurysm. In addition, the mechanical intravascular device120may be coated with a pharmaceutically-active agent, providing a synergistic effect through both mechanically impeding flow into the aneurysm as well as providing drug therapy to the tissue region. By applying an energy-transfer treatment, the collagen content of the surrounding vessel may be increased, thereby enhancing tissue in-growth of the coil to reduce the probability of recanalization to the aneurysm.

Now referring toFIG. 12, a step of yet another method of the present invention provides a catheter124having an energy-transfer element126disposed at its distal end portion being introduced into a blood vessel128proximate an aneurysm130in addition to the placement of an endovascular graft132at the aneurysm tissue site. Endovascular grafts commonly include a tubular collapsible mechanical framework that can be delivered by catheter to the aneurysm site. Moreover, the graft132may also have barb-like anchors that fasten the graft to the walls of the vessel. The endovascular graft132is intended to exclude blood flow from reaching the aneurysm while reinforcing the surrounding wall of the vessel, and such endovascular grafts are known in the art. By applying an energy-transfer treatment, the collagen content of the surrounding vessel may be increased, thereby enhancing the attachment of the vascular graft. Moreover, the energy-transfer treatment may be applied to side branch vasculature to induce stenosis and mitigate backflow into the aneurysm, further enhancing the ability of an implanted graft to seal the aneurysm and isolate the defect from blood flow.

An alternate embodiment, as shown inFIG. 13, a vessel region140treated with a balloon catheter142and the balloon catheter142is infused with a cryogenic fluid and maintained in contact with tissue for a period of time as described above with respect to the cryotreatment of an aneurysm. A balloon catheter is useful in situations where occlusion reduction is necessary and/or where a large area is being treated. In the latter case, the large contact area provided between the outer balloon surface and the vascular wall inner surface makes thermal energy transfer more efficient. In another exemplary procedure, a balloon dilated region of a vessel is cooled prior to implantation of a vascular stent.

As stated above, the combination of the energy-transfer treatment with the additional treatment methods may be applied to a tissue region at substantially the same time through a single medical device. Alternatively, the treatment combinations may be applied sequentially, that is to say, one treatment followed by another treatment shortly thereafter, i.e., in a single medical procedure.