A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:
The present invention provides a method for prophylactically treating a vessel region at risk for the development of vulnerable plaque with cryogenic energy. In general, a catheter is inserted into the patient's vascular network and manipulated towards a treatment site. The catheter is then activated so as to cool the tissue at the treatment site to a predetermined temperature for a desired amount of time in order to induce the formation of scar tissue, which may include collagen or smooth muscle cell formation. It is understood that a variety of cryogenic catheter configurations can be used to cool the treatment site.
Referring now to the drawing figures in which like reference designators refer to like elements, there is shown in
One or more temperature sensors (not shown) in electrical communication with the controller can be provided to regulate or terminate the flow of cryogenic fluid into the catheter 14 when a predetermined temperature at a selected point or points on or within the catheter is/are obtained. For example, a temperature sensor can be placed at a point proximate the distal end of the catheter and other temperature sensors can be placed at spaced intervals between the distal end of the catheter and another point that is between the distal end and the proximal end.
The catheter may include a flexible member having a thermally-transmissive region 18 and a fluid path through the flexible member to the thermally-transmissive region 18. A fluid path is also provided from the thermally-transmissive region 18 to a point external to the catheter, such as the proximal end. Exemplary fluid paths include one or more channels defined by the flexible member, and/or by one or more additional flexible members that are internal to the first flexible member. In addition, the catheter may include a guidewire lumen or similar structure to provide for over-the-wire use of the device. Also, even though many materials and structures can be thermally conductive or thermally transmissive if chilled to a very low temperature and/or cold soaked, as used herein, a “thermally-transmissive region” is intended to broadly encompass any structure or region of the catheter that readily conducts thermal energy.
Now referring to
Furthermore, while the thermally-transmissive region 18 can include a single, continuous, and uninterrupted surface or structure, it can also include multiple, discrete, thermally-transmissive structures that collectively define a thermally-transmissive region that is elongate or linear. For example, as shown in
In some embodiments, the thermally-transmissive region 18 of the catheter 14 may be deformable. An exemplary deformation is from a linear configuration to an arcuate configuration and is accomplished using mechanical and/or electrical devices known to those skilled in the art. For example, a wall portion of the flexible member can include a metal braid to make the catheter torquable for overall catheter steering and placement. Additionally, a cord, wire or cable can be incorporated with, or inserted into, the catheter for deformation of the thermally transmissive region.
With respect to the embodiments shown in both
In an exemplary procedure, as shown in
Once positioned, the tissue of the surrounding vessel wall is cooled by a cryogenic process to a desired temperature and for a time sufficient to inhibit the metabolic and/or disease processes responsible for the formation and progression of plaque and/or to induce the formation of scar tissue.
In the embodiment shown in
Irrespective of the particular device structure employed, the treatment site can be chilled in a wide range of temperatures and for various time intervals depending on the desired effect. For example, the tissue temperature can be held constant or it can vary. Further, the tissue can be chilled for one or more predetermined time intervals at the same or different temperatures. The time intervals can vary as well, so as to achieve a desired level of treatment for the target tissue. Also, certain areas of the treatment site may be cooled to a greater or lesser extent than surrounding target tissue.
During the cooling process as discussed above, a refrigerant such as nitrous oxide may be delivered under pressure such that expansion of the refrigerant occurs at a location within the catheter that is proximate to the target site, thereby cooling the tissue at and in the area near the target site. For example, treatment temperatures ranging from about ten degrees Celsius to about minus one hundred and twenty degrees Celsius, and preferably about zero degrees Celsius to about minus fifty degrees Celsius. The treatment may be applied for a duration lasting between approximately one second to about ten minutes.
In contrast with heat and radiation tissue treatments, cooling produces less damage to the arterial wall structure. The damage reduction occurs because a freeze injury does not significantly alter the tissue matrix structure as compared with the application of heat. Further, a freeze injury does not significantly reduce the reproductive/repair capability of the living tissue as compared with radiation treatments.
Positioning a catheter 14 inside the vascular vessel (i.e., the body lumen) 26, at approximately the point of the potential vulnerable plaque development, and cryogenically treating the region may advantageously arrest the metabolic process and/or disease responsible for the instability, as well as increase the thickness of the vessel wall by stimulating collagen synthesis and/or smooth muscle cell growth. The result may include the creation of a scar or other tissue formation which may significantly reduce the likelihood of subsequent plaque formation. It has been shown that a freeze injury will increase the level of collagen matrix within the treated segment. By applying such a cryogenic treatment to the vulnerable plaque that is at high risk of rupture, the plaque may be stabilized by increasing its collagen content and creating scar tissue that will make it less likely to rupture
It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.