February 9, 2007

Extending therapy boosts drug-eluting stents’ benefits

Featured Image

Robert Piana, M.D., talks with patient Nelson Short about the stent that was recently placed in Short’s coronary artery. (photo by Dana Johnson)

Extending therapy boosts drug-eluting stents’ benefits

When coronary arteries become clogged there are several non-surgical options available to help clear the way for normal blood flow — revascularization procedures ranging from angioplasty to stenting.

In recent months, the clinical benefit of using the latest coronary revascularization procedure — drug-eluting stents — was under close scrutiny and led to a national discussion among the advisory panel for the U.S. Food and Drug Administration to resolve the issue.

While these newest therapeutic tools have showed a marked reduction in the need for repeat revascularization procedures, a slightly increased risk of in-stent thrombosis or clotting has been observed in the first few years following the procedure.

“Basically, the problem was you traded one concern for another,” said David Zhao, M.D., director of the Cardiac Catheterization Laboratory and Interventional Cardiology.

“Once we looked at the situation, the bottom line was clear,” said Zhao. “We felt the benefit was very clear and wanted to tackle the potential high mortality rate with clotting in drug-eluting stents. Based on what we knew, we decided to extend the dual anti-platelet therapy. As soon as we recognized the issue, we made the change. And now it's an FDA recommendation. We took the initiative ourselves.

Dual anti-platelet therapy, or blood-thinning agents, is a part of the standard treatment for stent patients to reduce the risk of a blood clot forming in the artery and causing a heart attack. Previously, a patient would take plavix and aspirin for six months. Now patients take it for at least 12 months.

“The clotting events were very, very low, like 1 percent to 2 percent of patients. Statistically, the benefit from reducing restenosis outweighs the risk of a small percentage of clotting inside the stent,” said Zhao, associate professor of Medicine.

Restenosis, or renarrowing, has historically been a limitation of catheter-based coronary revascularization treatments. Early on with balloon angioplasty, rates of recurrence were as high as 40 percent within six months of performing the procedure. Bare metal stents significantly reduced restenosis rates to 20 percent to 30 percent. Now, drug-eluting stents have dramatically lowered the chance of renarrowing to less than 10 percent, according to Rob Piana, M.D., associate chief of the Division of Cardiovascular Medicine and director of the Vanderbilt Cardiovascular Network.

Stents are a wire mesh tube, placed over a balloon and inserted into a coronary artery via a catheter. When the balloon expands, the stent is then pushed into place, adhering to the artery walls, opening up the vessel. But because renarrowing or restenosis can occur when using bare metal stents, more advanced, drug-eluting stents were introduced a few years ago. These innovative stents slowly discharge medication that prevents the formation of scar tissue, which can block an artery.

“Last year, drug-eluting stents were used in 90 percent of procedures in most labs,” said Piana, director of the Adult Congenital Interventional Program and associate professor of Medicine. “There has been a small reduction after the recent findings and the FDA advisory panel report were released about drug-eluting stents. We have chosen to carefully evaluate every patient to determine if a drug-eluting stent is the best option, as well as each patient's suitability for long-term dual anti-platelet therapy.

“Vanderbilt has led the way in advancing the need for long-term anti-platelet therapy and it has been evident on all levels in the hospital, especially with personalized patient education by our nurse practitioners.”

Piana stresses that patients should consult with their cardiologist before stopping the dual anti-platelet therapy. This is especially important for patients who might be asked to discontinue these drugs in preparation for surgical procedures, such as hip replacement and dental extractions. The risk of in-stent thrombosis is worth possibly delaying the procedure until the therapy is safe to discontinue, said Piana.