Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
2003-03-06
2004-07-27
Gartenberg, Ehud (Department: 3742)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S095030
Reexamination Certificate
active
06767338
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related generally to medical devices. More specifically, the present invention is related to catheters for performing percutaneous myocardial revascularization (PMR) which is also referred to as transmyocardial revascularization (TMR). The present invention includes atraumatic tips for limiting unwanted penetration into the endocardium by outer tubes housing therapeutic tips within.
BACKGROUND OF THE INVENTION
A number of techniques are available for treating cardiovascular disease such as cardiovascular bypass surgery, coronary angioplasty, coronary atherectomy, and stent placement. These techniques are generally performed to bypass or open lesions in coronary vessels to restore patency and increase blood flow to the heart muscle. In some patients, the number of lesions are so great, or the locations so remote in the coronary vasculature, that restoring coronary artery blood flow to the heart is difficult. Transmyocardial revascularization (TMR), also known as percutaneous myocardial revascularization (PMR), has been developed as an alternative to these techniques which are directed to bypassing or removing lesions.
Heart muscle may be classified as healthy, hibernating, and “dead.” Dead tissue is not dead but is scarred, no longer contracting, and no longer capable of contracting even if adequately supplied with blood. Hibernating tissue is not contracting muscle tissue but is capable of contracting again, provided it is once more adequately supplied with blood. PMR is performed by wounding the myocardium of the heart, often forming and leaving patent holes, and sometimes injecting angiogenic substances in the process.
PMR was inspired in part by observations that reptilian hearts are largely supplied by blood directly from within the heart chambers. In contrast, mammalian hearts are supplied by blood pumped from the heart, through the aorta, and back to the heart muscle through the coronary arteries. Positive results have been observed in some patients receiving PMR treatments. The positive results may be due in part to blood being perfused into the myocardium from within the heart chambers through holes into the myocardium. The positive results are believed to be due in part to a wound healing response of the myocardium which includes formation of new blood vessels in the heart wall, which are believed to connect with the heart chamber interior and/or other coronary blood vessels. The PMR procedure can include cutting into the myocardium with therapeutic tips or burning holes with therapeutic tips having laser or radio-frequency current tips. PMR therapeutic tips can also be used to inject angiogenic substances such as growth factors or genes selected to induce angiogenesis.
The PMR procedure generally involves insertion of a therapeutic tip such as a sharp cutting tip into the heart chamber or chambers selected for treatment. The cutting tip and associated inner shaft can be guided into the chamber within a guide catheter, which may have been inserted into the vasculature a long distance from the heart. After the inner shaft distal end exits the guide catheter, the cutting tip is preferably steered to several positions for formation of several holes in a pattern across the endocardium. In order to steer the inner shaft and cutting tip, an outer shaft or tube is sometimes disposed coaxially about the inner shaft and within the guide catheter. The outer tube can have structural features at the distal end for bending to various angles to reach various locations in the heart wall. The outer tube and inner shaft can be cooperatively advanced to bring the cutting tip into contact with the heart wall.
To allow passage through the guide catheter, the outer tube should have a sufficiently small radial or transverse profile over its length. As with many catheter devices, a small profile is desirable to allow passage through tortuous and narrow vessels. At the outer tube distal end however, a small profile can also mean a small profile presented to the heart wall when inserting a cutting tip. It may be desirable to bring the outer tube very close or even into contact with the heart wall. While inserting a cutting tip into the heart wall may be desirable, inserting the larger outer tube distal end into the heart wall may be undesirable.
What is desirable is an improved guide device for steering inner shaft cutting tips into position within the heart myocardium. The improved guide device would preferably include a distal end having a small profile for passage through a guide catheter, yet having a larger profile for presentation to the heart inner wall to limit undesirable penetration by the guide device distal end.
SUMMARY OF THE INVENTION
The present invention includes devices for performing percutaneous myocardial revascularization (PMR) that can lessen the likelihood of a shaft distal end penetrating undesirably into the myocardium. In one application, PMR devices are used to penetrate the endocardium and myocardium to a controlled depth. One group of devices according to the present invention includes an inner shaft having a therapeutic tip, for example, a distal cutting tip. The inner shaft can be disposed within an outer tube or shaft lumen, and the outer shaft can be disposed within the lumen of a guide catheter. Preferably, the myocardium is penetrated by the cutting tip of the inner shaft but not by any larger profile outer shafts or tubes disposed about the inner shaft. The outer shaft distal region preferably has a first configuration having a small radial extent or profile allowing disposition of the outer shaft within a small guide catheter. The outer shaft distal region preferably also has a second configuration having a larger radial extent or profile for presentation against the endocardium. While having the larger profile, the outer tube distal end has increased resistance to penetrating the heart wall. The larger surface presented to the heart wall while in the radially expanded position forms a more atraumatic distal end for the outer tube distal end.
The outer tube distal end can have an atraumatic distal hood or tip that is formed of an elastic material that can be benignly forced against an obstacle such as the heart chamber inner wall, the endocardium. The atraumatic hood allows passage of the therapeutic tip therethrough to contact the heart wall. The atraumatic hood preferably has a sufficiently small profile so as to fit within an enclosing guide catheter in a first configuration. In one embodiment, the atraumatic hood is sufficiently elastic to longitudinally foreshorten and radially expand to attain a larger profile or radial extent when forced against the endocardium. The radially enlarged hood presents a larger transverse surface area to the heart wall and inhibits penetration of the heart wall by the outer shaft distal end. In one embodiment, the atraumatic hood has a bulbous shape and has a distal-most orifice for receiving the cutting tip of a slidably disposed inner therapeutic shaft.
One outer shaft atraumatic tip includes a distally disposed elastic member having a first, constrained configuration, and a second, unconstrained configuration. In a constrained configuration, which may occur when the tip is constrained within an enclosing guide catheter, the tip has a radial extent or profile that fits within the guide catheter. In an unconstrained configuration, the tip can expand to a larger radial extent or profile, where the radial extent is preferably larger than the outer diameter of the guide catheter. One atraumatic tip includes an elastomeric disk or washer transversely disposed to the longitudinal axis of the catheter. Another atraumatic tip includes several radially disposed segments or arms. In use, the atraumatic tip can expand radially outward when advanced from a guide catheter, and can radially contract when retracted back within the guide catheter.
Another outer shaft atraumatic distal end or stop includes a spring wound about the outside of the outer shaft distal region. The spring pref
Harris Chad
Hawk Matthew
Larson Scott
Mickley Timothy J.
Fastovsky Leonid
Gartenberg Ehud
Kenyon & Kenyon
Sci-Med Life Systems, Inc.
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