Opening Blocked Arteries with Drug Coating but No Stent

Newswise — In a new twist on combining drugs and minimally invasive therapy, early research suggests drug-coated angioplasty balloons keeps narrowed leg arteries open, avoiding the use of a stent altogether. Early multi-center data on the use of angioplasty balloons sprayed with a chemotherapeutic agent are being presented for the first time in the United States at the 18th Annual International Symposium on Endovascular Therapy (ISET).

The use of drug-coated stents to open narrowed and blocked heart arteries has skyrocketed and the devices are now used in the majority of such minimally invasive procedures. The drug coating is intended to reduce the incidence of restenosis, or renarrowing of the artery. Restenosis is common after conventional balloon angioplasty or placement of bare metal (non-drug-coated) stents, tiny mesh tubes that are left behind in the artery as scaffolding to prop it open. The drug-coated balloon concept has proven effective in opening previously stented coronary arteries. The balloon is coated with paclitaxel, which is used in the treatment of breast and other cancers and also one of the drugs used to coat stents.

"The drug prevents the growth of scar tissue that can cause the vessels to renarrow," said Gunnar Tepe, M.D., an assistant professor of radiology at the University of Tuebingen, Germany, who is presenting the data at ISET. "We're employing the same drug concept used in drug-coated stents, except the drug is delivered in a much shorter period of time and we don't leave behind a foreign object, a coated stent, which itself can cause problems down the road. Also, the drug is embedded in a coating material on the stent, which remains after the drug has been completely delivered to the vessel wall. This coating material may cause undesired effects later, as well."

Narrowed and blocked leg arteries are a common symptom of peripheral arterial disease (PAD). Like heart arteries, leg arteries can become clogged by plaque (fatty deposits) that slows or stops the flow of blood. From 8 to 12 million people in the United States have PAD, according to the American Heart Association. PAD can cause pain while walking and, in extreme cases, lead to gangrene, amputation of the toes, feet or legs or even death.

In conventional balloon angioplasty, a small cut is made in the groin and a thin tube, called a catheter, is advanced through the arteries to the site of the blockage, whether in the neck, heart, abdomen or legs. A tiny balloon is advanced to the blockage through the catheter and then inflated, compressing the plaque against the artery wall and opening it to allow better blood flow.

In the new procedure, the drug is sprayed onto a conventional angioplasty balloon. When the balloon is inflated, the drug is transferred from the balloon to the plaque.

Studies have shown that, within a year, about 4 in 10 conventional angioplasty procedures in the legs need to be repeated because the blood vessels have renarrowed, in part due to a bodily reaction to the trauma of the procedure. To improve results, physicians in recent years have tested other minimally invasive methods, including balloon angioplasty followed by placement of a stent, and more recently, coating those stents with drugs to prevent renarrowing.

In heart arteries, drug-coated stents have been very successful, but in limited early research, they have not worked well in narrowed and blocked leg arteries because leg arteries are larger than heart arteries and the clogs are longer, requiring excessive amounts of the drug. Also, depending on the location of the blockage, stents can become twisted and bent due to leg movement, leading to breakage and clotting. However, non-drug-coated stents have been shown to be useful in certain cases in the treatment of PAD, including: the repair of arteries that are torn (dissected) during treatment; opening completely blocked vessels; managing heavily calcified arteries; and treating vessels for prevention of early renarrowing.

The study includes 150 patients treated at three centers in Germany. The patients were evenly divided among three groups: those who received treatment with drug-coated balloon angioplasty, those who had conventional angioplasty with a non-coated balloon, and those who had conventional angioplasty with the drug in the contrast media, the solution that allows the arteries to show up on X-ray and helps the physician locate the blockage.

At ISET, Dr. Tepe is presenting early results on a portion of the patients in first two groups: 20 who received angioplasty with the drug-coated balloon and 25 who received conventional angioplasty with non-coated balloons. Preliminary research shows that after six months, the drug-coated balloons were significantly more effective than the non-coated balloons at preventing the treated arteries from renarrowing.

Researchers will continue to follow the patients for two years to determine if the incidence of renarrowing remains reduced.

"Our early results suggest the effects of drug-coated balloons are by far superior to uncoated balloons. Careful analysis of data and more research are required to confirm the findings and explore additional applications," said Dr. Tepe. "If research bears out, drug-coated balloons could be a very useful option for treating blocked arteries. In particular, they could play a major role in the peripheral arteries, because the incidence of restenosis is higher than in all other parts of the body. In addition, all other successful methods used to gain a better long-term benefit in the coronary arteries failed in the peripheral arteries."

Coating the balloon with the drug allows more of the drug to come in contact with the plaque than is the case with stents, notes Dr. Tepe. The drug covers the balloon and is then transferred to the entire artery surface that comes in contact with it. Because stents are mesh, not solid, drug concentration is highest on their struts. Tissue that comes in contact with the struts receives much more of the drug than the tissue that doesn't.

Drug-coated stents are also called drug-eluting stents, because the stent continues to release the drug for about 30 days after placement. In the case of drug-coated balloons, the drug is delivered to the vessel wall immediately, in one dose. Early research on animals suggests that the effect persists in spite of rapidly decreasing drug concentration.

The lengthier drug delivery period is of greater importance for procedures involving stents because reclogging is due in part to the body's reaction to the stent, said Dr. Tepe. That reaction takes place gradually over a period of months as the stent " a foreign object " remains in place.

Considered to be the premier meeting on endovascular therapy, the International Symposium on Endovascular Therapy (ISET) is attended by more than 2,000 physicians, scientists and industry professionals from around the world. The meeting is well known for its multidisciplinary approach to and live case demonstrations of procedures and devices for the diagnosis, treatment and prevention of cardiac and vascular disease. ISET is presented by the Baptist Cardiac & Vascular Institute, Miami.