For several years, crippling leg pain has prevented Joan Erickson from walking more than a block. If she paused to rest, she could walk a little more, but not enough to continue playing golf, her favorite pastime.
An ultrasound and CT scan early this year showed that an artery in Erickson'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.
This week at Stanford University Medical Center, Erickson became the first patient 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 Erickson'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, a former Stanford faculty member 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 placed in Joan Erickson, on the other hand, 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 Erickson's leg was made by Cook, Inc., a large medical-device manufacturer that is sponsoring the clinical trial. It 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."
Erickson is the first of 60 patients to enroll in the clinical trial that will take place at 10 centers across the country. Stanford is currently recruiting patients for the study. Eligible participants who have crampy calf pain after walking, relieved by rest, will be tested to see if they have a blockage in the superficial femoral artery - the most common cause of such pain and the target of this clinical trial. Those interested in participating may contact the research coordinators of the Division of Interventional Radiology at 650-725-9810.
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 the 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.
It will be six months to a year before Joan Erickson knows whether the blockage in her leg artery is recurring, but a day after the stent was in place, she was already walking with greater ease. "I want to get back to playing golf as soon as possible," she said.