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New Treatment for Peripheral Arterial Disease

Researchers hope that Implanting a drug-coated, flexible, metal-mesh tube called a drug-eluting stent into the superficial femoral artery of the thigh, that the drug coating will make it more likely to prevent the blockage from recurring, as compared with uncoated stents, which fail to do so in about one-quarter of the cases.

An ultrasound and CT scan early this year showed that an artery in a patient’s thigh was almost completely blocked, confirming that her troubles were caused by peripheral arterial disease, or PAD — a condition in which arteries to the arms, legs or internal organs are hardened and narrowed or obstructed.

Last week at Stanford University Medical Center, a patient became the first in the United States to receive a new treatment for PAD as part of a clinical trial. On March 21, Stanford researchers implanted a drug-coated, flexible, metal-mesh tube called a drug-eluting stent into the superficial femoral artery in the patient’s thigh. Researchers hope the drug coating will make it more likely to prevent the blockage from recurring, as compared with uncoated stents, which fail to do so in about one-quarter of the cases.

"We already know the benefits of drug-coated stents for the treatment of coronary artery disease," said Michael Dake, MD, who recently became chair of radiology at the University of Virginia and is the principal investigator of the multi-center study. "We’re hoping to translate that success to the peripheral circulation, especially in the legs where blockages can be disabling."
Peripheral arterial disease afflicts 8 million to 12 million Americans, many of whom have not been diagnosed, according to the American Heart Association. The most common symptoms are pain in the legs or buttocks while walking or climbing stairs. Risk factors for PAD are the same as for heart disease: smoking, diabetes, high blood pressure and a high cholesterol level. People with PAD are also at high risk for heart attacks and strokes. The disease can be treated with diet, exercise and some medications, but an angioplasty or a stent may be required to pop open a blocked artery.

When uncoated stents are used to open blocked arteries in the legs, about 20 to 30 percent of patients’ vessels become blocked again within a year, said Daniel Sze, MD, PhD, associate professor of radiology and principal investigator for Stanford’s portion of the multi-center trial. "Ideally with the drug-eluting stent, we’re hoping for that rate to drop to zero, but realistically we simply hope to see a significant improvement for patients."

The success in using drug-eluting stents for coronary artery disease suggests they should work for PAD. Still, said Sze, the challenges are greater when placing stents in leg arteries, which are much longer and wider than coronary arteries. A typical coronary stent is no bigger than a piece of dry macaroni and about as stiff. The leg stent used in the patient, was about the size of a crayon and extremely pliable.

"For the leg," said Sze, "a stent must be fatter, longer, more flexible and more resilient. It has to be designed to be crushed, bent, telescoped and twisted yet capable of popping open and straightening out again without breaking. That’s not necessary for the heart. In addition, the total dosage of the drug coating must be higher on the long leg stent than in a small stent in the heart."
The stent used in this patient is coated with an anti-cancer agent called paclitaxel, which has been used on drug-eluting stents for treating coronary artery disease. "Of course, we’re not treating cancer here," said Sze, "but cancer and re-narrowing of blood vessels have in common the uncontrolled growth of tissue. We’re hoping to control the growth of tissue that would re-block that artery."

This is the first phase of clinical trials for the drug-eluting stent. If proven safe and effective in this phase — expected to be completed in a little more than a year after 60 patients have been treated — a second, larger trial will look more closely at the long-term success of the stent in a larger population.

For more information, please visit the Web site of the medical center’s Office of Communication & Public Affairs at http://mednews.stanford.edu.

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