Artificial valves for malfunctioning leg veins may provide a treatment option for people with chronic venous insufficiency. Dr Dusan Pavcnik, Research professor of interventional therapy at Charles Dotter Institute, School of Medicine, Oregon Health and Science University, Portland, has developed a prosthetic vein valve that can be placed in the leg without surgery.
"We have been working since 1999 on a new type of bicuspid venous valve consisting of a small sheet of porcine small intestinal submucosa [SIS] attached to a square stent frame. We completed a long-term study in sheep with bioprosthetic venous valve (BVV) placement in jugular veins, studied its endothelization, and then placed it in three patients to evaluate its safety. We found it very promising," stated Pavcnik.
The stainless steel square stent with four barbs becomes a venous valve consisting of a small sheet of SIS attached to a square stent frame.
This artificial valve has already been successfully tested in animals. At ISET 2004, Pavcnik said that three patients with severe DCVI ranging in age from 38 to 64 years were treated with a square stent based SIS BVV as part of a safety trial. The patients began a three-month course of Coumadin therapy two days prior to BVV implantation, starting at 5mg/day. Immediately prior to BVV implantation, 5000 units of heparin were added.
The valves were implanted percutaneously by right internal jugular approach. The valve was selected using a size similar to the vein diameter measured with the Valsalva maneuver - about 1-2mm larger than the vein diameter without increased pressure. The selected lyophilized bioprosthetic venous valve was rehydrated with injection 10cc heparinized saline through the side arm of the guide catheter 15 minutes before delivery. The bioprosthetic venous valve was implanted into proximal femoral vein just below the confluence with the profunda femoral vein.
Patient 1: 38-year old male with post-thrombotic deep venous insufficiency of the left leg had severe venous claudication and an active ulcer (CEAP classification C-6). Edema of the left leg improved, the left thigh circumference decreased from 63.8cm before valve replacement to 58.5 at one-year follow-up.
Patient 3: 40-year old man with DVIS due to post-thrombotic syndrome has severe venous claudication with CEAP C-4) skin changes, edema, pain) in his left leg. These symptoms were due to severe reflux in the left femoral and valve-less popliteal veins. At one year, the patients' symptoms are decreased, and the bioprosthetic venous valve is functioning well as a monocusp valve (due to tilting) with a minimal leak.
According to Pavcnik, "Although a great deal of work remains to be done, these very promising early results indicate that the development of a bioprosthetic venous valve for transcatheter placement is more than just feasible."
A second-generation bioprosthetic venous valve is in testing to eliminate the occasional tilting. Pavcnik concluded by saying that a manufactured percutaneously implantable nonimunogneic bioprosthetic venous valve that remains patent and competent over time is an attractive alternative to direct venous valvular reconstruction or transplantation.
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