Venous valve aims for huge
market
Stent-based model enters clinical
trials
By Jane Lowers
Chronic venous insufficiency may lack the sudden-death risk of an aortic
aneurysm, but efforts to keep blood from pooling in the lower extremities have
met with major challenges.
Most patients are treated with little more than leg rest or compression
stockings. Success has been limited with valves imported from animals or
patients' arms, because they are prone to thrombosis or failure. A stent-based
model entering clinical trials this year offers a new approach, encouraging the
body to form a native valve. [Fig. 1]
Based on a thin, square wire stent, the artificial valve developed by Cook
Corp. provides a framework of collagen tissue in the form of small intestine
submucosa (SIS). Attracted to the collagen matrix, native cells gradually
colonize the stent, remodeling and replacing it, according to developer Dr.
Dusan Pavcnik of Oregon's Dotter Institute.
"The valve over time is not foreign. Instead, it provides a biological
framework for the body," he said. "It appears to undergo remodeling with the
recipient's own cells and function without the need for anticoagulants."
In a six-month sheep study, 22 of 25 valves remained functional at six
months. One developed thrombosis while two failed to perform. A 90-day human
trial outside the U.S. is scheduled for summer, and Cook expects to bring the
results to the FDA for a U.S. trial in 2002.
The market for a successful venous valve is huge, according to Pavcnik.
"In Europe and North America, 2% to 3% of the population has venous problems,
three times more patients than arterial disease," he said. "Four or five million
people could benefit from a simple procedure."
