Spokane radiologist Rod Raabe has begun implanting artificial veins inside blocked blood vessels in patients legs to help restore blood flow and eliminate leg pain that can be debilitating.
Raabe is working with the Heart Institute of Spokane on a study coordinated by W.L. Gore & Associates Inc., an Elkton, Md.-based company that developed the artificial vein, which also is called a vascular stent graft. The tubular device is made partly out of Gore-Tex, another W.L. Gore invention made popular as a breathable waterproof material in outdoor clothing.
Spokane is one of 20 sites nationwide involved in the study. Through the inquiry, Gore hopes to secure U.S. Food and Drug Administration approval to market the stent graft, Raabe says.
The noninvasive procedure is targeted at people who suffer leg pain because of a decreased blood supply caused by a constricted or obstructed blood vessel in the thigh area. When a blood vessel becomes blocked, the flow of blood is restricted and partially redirected through a number of smaller blood vessels, thereby limiting the supply of blood. The lack of blood supplied to the leg muscles can cause extreme pain for some people, resulting in an inability to walk and if left untreated possibly tissue loss and amputation.
Raabe says its estimated that more than 10 million people nationwide have peripheral arterial disease, which is a form of atherosclerosisa narrowing of the vessels due to deposits of fat and calciumin the arms and legs. Of those people, about 5 million have altered their lifestyles because of the affliction, and only 1.5 million of those 5 million people are receiving any type of systematic care. He adds that about 95 percent of people with peripheral arterial disease go undiagnosed.
Most people think the pain they feel is because theyre getting older and theyre out of shape, but they dont do anything about it. Others think it might be related to arthritis, and very few guess that its a vascular disease, Raabe says.
The conventional treatment for peripheral arterial disease has been an angioplasty, in which a balloon catheter is guided into a blocked blood vessel and then inflated to open the blood vessel, or bypass surgery, in which a vein is removed from elsewhere in the body and used to replace the blocked blood vessel. Raabe says that angioplasty has been a good alternative for those who, for health reasons, arent able to undergo bypass surgery.
Yet, only 20 percent of the blocked blood vessels that have been forced open by an angioplasty balloon remain open 12 months later. The remaining 80 percent collapse within the first year following the procedure. In preliminary results from the investigational stent grafts, 85 percent of the blood vessels that have been opened remain open 12 months after the procedure.
Raabe began performing the procedure here last month and has implanted stent grafts into two patients. One of the patients, prior to the procedure, had loved to play golf, but could no longer do so because pain in his leg prevented him from walking from a golf cart to the tee box. He also had lost his ability to work.
Immediately following the procedure, the patient said he was going to go buy some walking shoes, Raabe says. The results are immediate. As soon as the graft is in place, patients say they can feel the circulation in their leg improve.
The artificial vein essentially is a Gore-Tex tube surrounded by a metal mesh that gives the artificial vein flexibility, but prevents the tube from being pinched shut. The artificial vein varies in length, depending on the length of the blockage in a blood vessel, and in diameter, depending on the diameter of the original blood vessel. Once it is in place, it basically takes the place of the failed vein.
Some of the patients accepted into the study are randomly selected to receive stent grafts, while others undergo angioplasty, Raabe says. If a patient has an angioplasty and it fails, however, he or she then can receive a stent graft.
The stent graft procedure, which Raabe hopes to perform on 25 people here during the study, involves guiding a sheath through a blood vessel from the groin area to the site of the blockage. Inside the sheath is a catheter and a wire. Once the sheath has reached the area where the blood vessel is blocked, the wire is pushed through the blocked blood vessel and is used to help Raabe determine how long the artificial vein needs to be.
When the wire is in place, the catheter is removed, and a second catheter is inserted. The stent graft is fitted snuggly around the second catheter, and a fiber trails from the stent graft. The second catheter is placed over the top of the wire that has been pushed through the blocked blood vessel earlier. Once the stent graft is in place, the fiber that trailed behind the stent graft is pulled, allowing the stent graft to expand to the size of the blood vessel. Finally, the second catheter, the wire, and the sheath are removedleaving the stent graft in place.
One of the requirements for performing the procedure is that the physician must be able to squeeze the wire through the blockage in the blood vessel. If that cant be done, the patients other alternative would be to have bypass surgery, if he or she is able to undergo surgery.
During the stent procedure, the patients are awake, although they have been given a mild sedative to help them relax. After the procedure, patients take a daily dose of aspirin to help thin their blood, but dont take any other medications.
The stent graft procedure costs much less than surgery, but is slightly more expensive than an angioplasty, Raabe says. He adds, though, that the results from the procedure seem to be more long-lasting than those from angioplasty, although those findings are preliminary.
Raabe says that the Heart Institute has been at the forefront of stent therapy. He says that he and Dr. Katherine Tuttle, director of research at the Heart Institute, began studying the effects of stent therapy in the renal arterywhich is the main artery that leads from the aorta to the kidneysa few years ago.
I believe we were one of the first in Washington to place stents in renal arteries, Raabe says. The Heart Institute has delved into that area of research through the Renal Artery Stenting study.
Tuttle and Raabe expect that an article they have written about the findings from the study will be published early next month in the American Journal of Kidney Disease.
Raabe says that in the last five years or so, stent therapy also has become one of the leading treatments for heart disease, and now various types of stents are being implanted in blood vessels throughout the body. Studying the effects of stent therapy to treat a number of vascular diseases also has resulted in more cooperation between organ specialists, Tuttle says.
Vascular disease affects every part of the body, because the blood vessels go everywhere, she says.
The use of stents and artificial veins is providing a new option for treatment of patients, Tuttle says. She adds that if the study of implanting stent grafts in the leg is successful, she expects similar stent grafts to be tried in blocked blood vessels in the kidneys and the brain.
Such devices, however, might not be needed in the future if new research thats being conducted both at the Heart Institute and at other study sites is fruitful.
Scientists elsewhere are studying a biological molecule known as vascular endothelial growth factor (VEGF), which has been identified as causing blood vessels to grow. Tuttle says that in trials, VEGF has been injected directly into a blocked blood vessel, and a new vessel has grown in its place, eliminating the need to implant artificial veins. The molecule, however, still is being studied.
In Spokane, Tuttle and Rick Meek, a senior research scientist at the Heart Institute, are studying another molecule called transforming growth factor beta (TGF), which is believed to stimulate cells that create scar tissue. The Heart Institute is studying TGF to understand how it affects the development of scar tissue in the blood vessels within the kidneysassuming that results from the study would lead to insights that also could be applied to larger blood vessels elsewhere in the body. Specifically, the institute is looking at how TGF is affected by amino acids and glucose, which tend to be abundant in diabetics who have experienced kidney failure because of blood vessels and arteries that have become blocked by scar tissue.
Basically we want to learn how we can manipulate biological molecules so that we can maintain good results and prevent abundant scarring in arteries and blood vessels in the future, Tuttle says.
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