Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
1999-04-15
2001-07-10
McDermott, Corrine (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
C623S001310, C623S001360, C606S108000
Reexamination Certificate
active
06258119
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention is generally directed to the fields of cardiac surgery and interventional cardiology, and particularly, to mechanical devices and methods suited for improving blood flow to a heart muscle by Trans Myocardial Revascularization (TMR).
2. Description of Related Art
Symptomatic occlusive coronary artery disease that does not respond to medical or interventional treatment is a major challenge for cardiac surgeons and cardiologists. The discovery of sinusoidal communications within the myocardium (Wearns, 1993) has motivated researchers to attempt various methods for myocardial revascularization based on the existence of this vascular mesh network. These methods aimed at the delivery of oxygenated blood to the vicinity of the sponge-like sinusoidal plexus in order to restore blood flow to the ischemic myocardium. Several investigators have attempted to deliver oxygenated blood directly from the left ventricle into the myocardial sinusoids by employing needle acupuncture to create transmural channels. Trans Myocardial Revascularization (TMR) has been employed clinically (Mirhoseini, 1991) by utilizing a CO2 laser for creating transmural channels in the left ventricular myocardium. These channels are typically 1 mm in diameter and extend throughout the wall thickness (15 to 20 mm) of the ventricle. It has been hypothesized that TMR works by providing a fluid conduit for oxygenated blood to flow from the endocardiac surface (heart chamber) to the mycardium inner layers thus providing oxygenated blood to myocardial cells without requiring coronary circulation; as in reptiles. Animal studies in the canine model have demonstrated the feasibility of this approach. In these studies, an increase in survival rate was demonstrated in dogs that had transmural channels and ligated coronary arteries.
While clinical studies have demonstrated improvements in patient status following TMR, histological studies indicate that the channels created for TMR tend to close shortly after the procedure. Randomized, prospective clinical trials are underway to examine the merit of TMR compared to medical treatment. In the meantime, research studies are being initiated to provide an understanding of the mechanism by which TMR actually works.
It would be desirable to develop means for maintaining the patency of TMR channels within the myocardium. Furthermore, it would be desirable to create channels for TMR without requiring the use of an expensive and bulky laser system, such as currently available CO2 laser systems. This invention provides the desired means for producing trans myocardial channels that are likely to remain patent, and that do not require laser application for generating these channels.
Specifically, the objective of the present invention is to generate needle-made channels or space in the ischemic heart wall, and to deliver or place in these channels (or space) an array of implants or stents in order to provide improved means for supplying blood nutrients to ischemic myocardial tissue. Nutrients flow to the stented channels from the ventricular cavity, and diffuse from the side ports of the stent to the myocardial tissue through the needle-made channels. Our disclosed TMR approach of producing stented, needle-made, channels is supported by the recent scientific evidence (Whittaker et al, 1996) that needle-made transmural channels can protect ischemic tissue. Whittaker et al. assessed myocardial response at two months to laser and needle-made channels in the rat model which has little native collateral circulation. They found that channels created by a needle can protect the heart against coronary artery occlusion, and that these channels provide greater protection to ischemic tissue than channels created by laser. The limitation of needle-made channels is early closure (Pifarre, 1969). The disclosed implant approach offers a possible solution to the early closure problem, while taking advantage of simple and effective needle-made channels for TMR.
SUMMARY OF THE INVENTION
This invention provides implant and needle means for creating and maintaining a patent lumen in the diseased myocardium. This implant provides a conduit for the flow of blood nutrients from the ventricular chamber to the intramyocardial vascular network. This implant can be used as the sole therapy or as an adjunctive therapy to other forms of TMR. Revascularization of the myocardium can be achieved and maintained by creating implanted, needle-made, channels within the myocardial tissue. These channels can allow blood nutrients within the left ventricular cavity to find direct access to ischemic zones within the ventricular wall independent of access through the coronary arteries.
Various configurations of implants are disclosed; including flexible and rigid implants, screw implants, sleeve implants, and others. Manual or powered devices are disclosed for the delivery or placement of implants into a heart wall. The proximal end of each implant terminates at the epicardial surface and provides mechanical holding means to prevent implant detachment and leakage of blood from the ventricle. Each implant is designed so as to maintain an adequate pressure gradient between the left ventricle and the myocardial tissue in order to maintain the flow from the ventricular cavity to the myocardial tissue of blood nutrients.
Furthermore, the disclosed TMR implants may define a cavity, which can be pressurized during operation so as to enhance the flow of blood to myocardial tissue. Each such implant can essentially operate as a mini-pump that is activated by myocardial contraction or by an external energy source.
Several embodiments of the implant and delivery systems therefor are proposed. The implants include the following: flexible spring, rigid sleeve, hollow screw, helical screw, and pumping (active) implants. The implants can be prestressed or made from memory metal in order to minimize the size of the implant during the insertion process. The various delivery systems are described below.
REFERENCES:
patent: 5466242 (1995-11-01), Mori
patent: 5500013 (1996-03-01), Buscemi et al.
Hussein Hany
Sulek Stanislaw
Koh Choon P.
McDermott Corrine
Myocardial Stents, Inc.
O'Neill James G.
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