Surgery – Instruments
Reexamination Certificate
1999-06-21
2001-10-23
Dvorak, Linda C. M. (Department: 3739)
Surgery
Instruments
C604S059000, C604S117000, C604S144000
Reexamination Certificate
active
06306125
ABSTRACT:
This invention pertains generally to the treatment of living tissue and, more particularly, to a system for inserting an implant in tissue in order to enhance blood flow in that tissue as, for example, in the treatment of ischemic heart disease.
Coronary by-pass surgery, balloon angioplasty, and stenting are now well-developed procedures for correcting reduced blood supply due to arterial blockage. Such procedures target large vessels and are not as effective in treating ischemic diseases where the pathology is centered in the small vessels, or where procedures such as coronary artery bypass grafting (CABG) or percutaneous transluminal coronary angioplasty (PTCA) are not medically indicated. New technologies are emerging for enhancing blood flow in the peripheral vascular system at the level of capillaries and arterioles. One of the most promising of these technologies is interventional angiogenesis in which the patient's own body is stimulated to grow new capillary beds or vessels and thereby improve the blood supply to the ischemic region. Interventional angiogenesis is a treatment for addressing small vascular disease, and can be used in conjunction with large vessel procedures such as CABG and PTCA.
Two basic interventional angiogenesis technologies which have been developed in recent years are transmyocardial revascularization (TMR) and
angiogenic agent therapy. TMR involves the creation of channels in the myocardium to promote the release of the body's own angiogenic agents, and angiogenic agent therapy involves the injection of growth factors or growth vectors into the myocardium or vasculature.
TMR is used primarily in the treatment of patients with ischemic heart disease. In TMR, a number of small channels are created in the ischemic area of the myocardium to elicit a therapeutic response by stimulating angiogenic capillary formation, and thereby increase blood flow to the ischemic region. In clinical trials, TMR has shown new vessel growth in an ischemic region within a few weeks of treatment. As a result, many patients have experiences an immediate and dramatic reduction in angina symptoms and an improvement in cardiac function over time.
Laser TMR systems using CO
2
and YAG lasers, which recently received FDA approval for the treatment of Class IV angina, have demonstrated dramatic relief of Class III and Class IV angina along with new capillary growth. However, current laser-based systems have significant clinical and cost disadvantages which may prevent them from enjoying long-term market acceptance. Since the channels are created by ablation of the tissue, laser cutting can result in significant ancillary tissue damage to the myocardium. In addition, and possibly even more significant, laser treatment is not readily used in conjunction with new drug treatments which are currently under development and are expected to be available in a few years. Laser systems are also relatively expensive, and require special facilities and safety precautions.
There have also been some efforts to create revascularization channels in the myocardium by other means such as RF ablation and by the use of mechanical cutters. However, each of these techniques has its own limitations and disadvantages.
The direct application of growth factors into the myocardium is currently undergoing intensive early clinical investigation. Growth factors have been delivered (a) directly into the myocardium during coronary by-pass surgery or through a mini-thoracotomy, (b) intra-coronarally using a catheter, (c) intravenously via infusion, and (d) in laser TMR channels via syringe.
Various growth factors have been used, including FGF-1 from strains of
E. Coli
(Cardio Vascular Genetic Engineering, Inc.), naked plasmid DNA encoding VEGF-165 (Human Genome Sciences, Inc.), adenovirus VEGF-121 (Gen Vec, Inc.), recombinant human VEGF-165 (Genentech, Inc.), human adenovirus-5 expressing human FGF-4 (Collateral Therapeutics, Inc.), bFGF incorporated into heparin-alginate microspheres, and hypoxiainducible factor (HIF-1) (Genzyme).
Although the angiogenesis due to the application of growth factors can be demonstrated by imaging techniques, it is still uncertain whether any significant improvement in myocardial function will result. The process of angiogenesis is such a complex series of events that a one-time application of growth factor is not likely to yield optimal angiogenesis. There are also concerns that the direct application of growth factor may have negative side effects such as accelerating atherosclerosis, facilitating latent malignancy, hypotensive effects and others.
A variety of implantable drug delivery devices have heretofore been provided for use in controlled and sustained delivery of a medication in vivo to humans as well as to animals. Such implants have often been made from permeable, biodegradable and/or bioerodable materials, such as synthetic polymers. They are generally macroscopic in size and scale and are typically on the order of 3-10 mm in diameter and about 1-3 cm in length. They are typically designed to be sleek to allow ready insertion through an incision in the skin, and they have a tendency to migrate due to normal muscle contraction.
It is in general an object of the invention to provide a new and improved implant delivery system for inserting an implant in tissue in order to enhance blood flow in the tissue
Another object of the invention is to provide an implant delivery system of the above character which overcomes the limitations and disadvantages of the prior art.
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Joslyn Danforth
Nikolic Serjan D.
Parker Theodore L.
Dvorak Linda C. M.
Flehr Hohbach Test Albritton & Herbert LLP
Neovasys, Inc.
Ram Joslyn Debra
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