Artificial Valves May Be Answer for Vein Diseases
01/22/02 Portland, Ore.
It is amazingly simple, yet it could alter the lives of millions of Americans who suffer from poor blood flow in their veins.
The artificial venous valve, invented at Oregon Health & Science University's Dotter Interventional Institute, in collaboration with Cook Inc., starts as a square of stainless steel wire that frames a skin-like membrane slit on the diagonal. Folded and inserted into a patient's vein, where it partially reopens, it transforms elegantly into the sleek shape and function of a one-way valve.
Inventor Dusan Pavcnik, M.D., Ph.D., research professor of interventional therapy at the Dotter Institute, OHSU School of Medicine, will present the valve on Monday, Jan. 21, at the 14th Annual International Symposium on Endovascular Therapy in Miami Beach. Pavcnik also holds the Josef Rösch Chair of Interventional Radiology Research at OHSU.
The device has been licensed by OHSU to Cook Inc. of Bloomington, Ind., and is expected to be ready for clinical trials this spring.
Venous disease ranges in severity from the unsightly, such as spider and varicose veins, to the life-altering, such as chronic venous insufficiency. In the latter, failing valves in leg veins can't do their job of pushing blood up against the forces of gravity toward the heart. As a result, blood pools in the lower legs and may cause pain, swelling, skin discoloration or ulcers.
Pavcnik first developed the square wire device, or stent, and later combined it with a biomaterial called small intestinal submucosa (SIS), a collagen-based product derived from the small intestines of pigs and manufactured by Cook Biotech of Lafayette, Ind. "When you add the biomaterial," Pavcnik said, "you are able to mimic the natural valve."
The valve does not require surgery. It is introduced with a catheter inserted into a neck vein or groin vein, and steered under imaging guidance to the problem vein deep in the leg. Folded for introduction, it self-expands inside the vein. It is likely that two or three valves would be placed in each leg over the natural but failing valves.
The stent's barbed corners anchor the artificial valve inside the veins. The divided membrane takes the form of two "wings" that enable blood to flow up between them, but not back down. Over time, the body grows new tissue that replaces the membrane naturally.
People with venous diseases currently have few options other than supportive treatment, such as special boots or stockings, or resting with their legs elevated. The artificial venous valve could be a major breakthrough. It has been tested successfully in animals. The forthcoming clinical trials will determine not only its effectiveness in people, but also how long it remains effective. "It has good potential to last a long time," Pavcnik said. It also has potential to treat testicular and ovarian vein problems that can cause infertility.
OHSU's Office of Technology and Research Collaborations worked with Cook Inc. to protect the patent. "This complete package of technology, patents and license to an industry leader such as Cook Inc. represents a near-perfect combination of business opportunity for our industrial partner and the best means of moving OHSU's invention through the federal approval process so it can be made available as therapy for venous disorders," said Bill Thompson, Ph.D., senior licensing associate at OHSU. Eventual sale of the licensed venous valves is expected to generate royalties for the university, which will be shared with the OHSU inventors.
Other artificial valves have been developed elsewhere, but most require surgery. The critical problem Pavcnik was able to solve was to construct a device small enough to be inserted without surgery, but strong enough to withstand the considerable downward pressure of blood through the veins when a person is upright.
The square stent itself has other potential applications to improve minimally invasive treatment as a vascular stent, endograft or occluder for diseased veins or arteries. It could be used as well as an aortic or pulmonary valve.
About the Dotter Interventional Institute
The Dotter Interventional Institute has a history of innovation, in keeping with the spirit of its founder, Charles Dotter, M.D. He is considered the father of interventional radiology, a less-invasive alternative to surgery that embraces such now-common treatments as balloon catheter angioplasty and uterine artery embolization for fibroids. Among the institute's many inventions are procedures for peripheral vascular disease, esophageal stenting, transjugular intrahepatic portosystemic shunt (TIPS) placement, and stent-grafts.
The Dotter Interventional Institute was established by the Oregon State Board of Higher Education in April 1990, as an independent, freestanding division of the Oregon Health & Science University School of Medicine. The institute was charged with developing a multidisciplinary program in interventional therapy with emphasis on interventional education, research and patient care.