Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
2001-08-17
2004-02-03
Rollins, Rosiland Kearney (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S104000, C607S106000, C607S113000, C606S020000, C606S021000, C606S024000, C128S898000
Reexamination Certificate
active
06685732
ABSTRACT:
CROSS-REFERENCE TO MICROFICHE APPENDIX
(none)
BACKGROUND OF THE INVENTION
Balloon angioplasty, or the technology of reshaping of a blood vessel for the purpose of establishing vessel patency using a balloon tipped catheter, has been known since the late 1970's. The procedure involves the use of a balloon catheter that is guided by means of a guidewire through a guiding catheter to the target lesion or vessel blockage. The balloon typically is equipped with one or more marker bands that allow the interventionalist to visualize the position of the balloon in reference to the lesion with the aid of fluoroscopy. Once in place, i.e., centered with the lesion, the balloon is inflated with a biocompatible fluid, and pressurized to the appropriate pressure to allow the vessel to open.
Typical procedures are completed with balloon inflation pressures between 8 and 12 atmospheres. A percentage of lesions, typically heavily calcified lesions, require much higher balloon inflation pressures, e.g., upward of 20 atmospheres. At times, the balloon inflation procedure is repeated several times before the lesion or blockage will yield. The placement of stents after angioplasty has become popular as it reduces the rate of restenosis.
Restenosis refers to the renarrowing of the vascular lumen following vascular intervention such as a balloon angioplasty procedure or stent insertion. Restenosis is clinically defined as a greater than 50% loss of initial lumen diameter. The mechanism or root causes of restenosis are still not fully understood. The causes are multifactorial, and are partly the result of the injury caused by the balloon angioplasty procedure and stent placement. With the advent of stents, restenosis rates have dropped from over 30% to 10-20%. Recently, the use and effectiveness of low-dose radiation administered intravascularly following angioplasty is being evaluated as a method to alter the DNA or RNA of an affected vessel's cells in the hope of reducing cell proliferation.
Another cardiological malady is atrial fibrillation. Atrial fibrillation refers to very rapid irregular contractions of the atria of the heart resulting in a lack of synchronization between the heartbeat and the pulse. The irregular contractions are due to irregular electrical activity that originates in the area of the pulmonary veins. A proposed device, currently under development, for treating atrial fibrillation is a balloon filled with saline that can be ultrasonically agitated and heated. This device is inserted in the femoral vein and snaked into the right atrium. The device is then poked through the interatrial septum and into the left atrium, where it is then angled into the volume adjoining the suspect pulmonary vein with the left atrium.
Research in atrial fibrillation indicates that substantially complete circumferential necrosis is required for a therapeutic benefit. The above technique is disadvantageous in that circumferential portions of the tissue, desired to be necrosed, are not in fact affected. Other techniques, including RF ablation, are similarly inefficient. Moreover, these techniques leave the necrosed portions with jagged edges, i.e., there is poor demarcation between the healthy and the necrosed tissue. These edges can then cause electrical short circuits, and associated electrical irregularities, due to the high electric fields associated with jagged edges of a conductive medium.
The above technique is also disadvantageous in that heating is employed. Heating is associated with several problems, including increased coagulum and thrombus formation, leading to emboli. Heating also stimulates stenosis of the vein. Finally, since tissues can only safely be heated to temperatures of less than or about 75° C.-85° C. due to charring and tissue rupture secondary to steam formation. The thermal gradient thus induced is fairly minimal, leading to a limited heat transfer. Moreover, since heating causes tissues to become less adherent to the adjacent heat transfer element, the tissue contact with the heat transfer element is also reduced, further decreasing the heat transfer.
Another disadvantage that may arise during either cooling or heating results from the imperfections of the surface of the tissue at or adjacent to the point of contact with the cryoballoon (in the case of cooling). In particular, surface features of the tissue may affect the local geometry such that portions of the balloon attain a better contact, and thus a better conductive heat transfer, with the tissue. Such portions may be more likely to achieve cell necrosis than other portions. As noted above, incomplete circumferential necrosis is often deleterious in treating atrial fibrillation and may well be further deleterious due to the necessity of future treatments. Accordingly, a method and device to achieve better conductive heat transfer between tissue to be ablated and an ablation balloon is needed.
SUMMARY OF THE INVENTION
The present invention provides an enhanced method and device to inhibit or reduce the rate of restenosis following angioplasty or stent placement. The invention is similar to placing an ice pack on a sore or overstrained muscle for a period of time to minimize or inhibit the bio-chemical events responsible for an associated inflammatory response. An embodiment of the invention generally involves placing a balloon-tipped catheter in the area treated or opened through balloon angioplasty immediately following angioplasty. A so-called “cryoplasty” balloon, which can have a dual balloon structure, may be delivered through a guiding catheter and over a guidewire already in place from a balloon angioplasty. The dual balloon structure has benefits described below and also allows for a more robust design. The balloon is porous so that an amount of ablation fluid is delivered to the tissue at the ablation site.
The balloon may be centered in the recently opened vessel with the aid of radio opaque marker bands, indicating the “working length” of the balloon. In choosing a working length, it is important to note that typical lesions may have a size on the order of 2-3 cm. In the dual balloon design, biocompatible heat transfer fluid, which may contain contrast media, may be infused through the space between the dual balloons. While this fluid does not circulate in this embodiment, once it is chilled or even frozen by thermal contact with a cooling fluid, it will stay sufficiently cold for therapeutic purposes. Subsequently, a biocompatible cooling fluid with a temperature between about, e.g., −40° C. and −60° C., may be injected into the interior of the inner balloon, and circulated through a supply lumen and a return lumen. The fluid exits the supply lumen through a skive in the lumen, and returns to the refrigeration unit via another skive and the return lumen.
The biocompatible cooling fluid chills the biocompatible heat transfer fluid between the dual balloons to a therapeutic temperature between about, e.g., 0° C. and −50° C. The chilled heat transfer fluid between the dual balloons transfers thermal energy through the balloon wall and into the adjacent intimal vascular tissue for the appropriate therapeutic length of time.
To aid in conduction, a small portion of the chilled heat transfer fluid between the dual balloons may contact the adjacent intimal vascular tissue for the appropriate therapeutic length of time due to the porosity or microporosity of the outer balloon.
Upon completion of the therapy, the circulation of the biocompatible cooling fluid is stopped, and the remaining heat transfer fluid between the dual balloons withdrawn through the annular space. Both balloons may be collapsed by means of causing a soft vacuum in the lumens. Once collapsed, the cryoplasty catheter may be withdrawn from the treated site and patient through the guiding catheter.
In more detail, in one aspect, the invention is directed to a device to treat tissue, including an outer tube, an inner tube disposed at least partially within the outer tube, and a dual balloon including an inner balloon
Innercool Therapies, Inc.
Rollins Rosiland Kearney
Wieczorek Mark D.
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