MONDAY, Sept. 3, 2001 (HealthDayNews) -- Clotting in the wake of a procedure to widen clogged blood vessels may be three times more common than doctors previously estimated, a new study says.
Researchers say the risk of potentially life-threatening thrombosis after the placement of a stent to improve blood flow is as high as 3.5 per 100 operations. Earlier estimates put that rate at about 1 percent to 1.5 percent.
The new research, by Duke University researchers, was presented today at a meeting of the European Society of Cardiology in Stockholm.
Stents, wire mesh sleeves that help restore normal blood flow in blocked vessels, are becoming increasingly common in the United States. Nearly 500,000 are installed each year, usually after angioplasty to open a narrowed channel.
But the devices are prone to two serious complications. One is restenosis, when the vessel narrows and again crimps blood flow. The other is the formation of blood clots that can break off and lead to heart attacks. The clots generally occur within two weeks to a month after the stent procedure and are thought to be a direct result of trauma to the vessel lining when doctors install the device.
Dr. Thaddeus Tolleson, leader of the Duke team, says prior estimates of stent-related clotting are based on studies that excluded patients with acute coronary syndrome, a condition marked by critically impaired blood flow to the heart muscle that produces serious chest pain and can even lead to a small heart attack. Yet the condition is relatively common and accounts for as much as 40 percent to 60 percent of the caseload for the average cardiologist, Tolleson says.
So the researchers looked at data from two large trials that included subjects with acute coronary syndrome. Both trials compared sibrafiban, the so-called "super aspirin," with regular aspirin to prevent recurrent heart attacks.
Of the nearly 16,000 patients in the two studies, 4,641 underwent angioplasty followed by the placement of a stent. They were also given an anti-platelet drug to reduce the risk of clotting.
In the first trial, 2.1 percent of patients suffered clots at the stent site. The number was 4.7 percent in the second trial. Diabetics, women, the elderly, those who've suffered at least one heart attack and those who already had angioplasty were more at risk of clots, Tolleson says. Patients with more than one of these risk factors had an even greater chance of clotting.
Tolleson says the findings shouldn't be interpreted as a reason to discourage stenting. "That should definitely not be the take-home message because there's not an alternative that's better," he says. And although the risk of clotting may be higher than previously believed. "the chances are still 97 percent that you'd fly through [a stent installation] without any problems," he says.
However, the researchers say the results should encourage cardiologists to look for ways to drive down the likelihood of stent-related clots, especially in patients with one or more risk factors for the complication. Such work already is well under way, as doctors now commonly pre-treat stent patients with anti-platelet drugs and stents that are coated with clot-busting compounds.
Dr. Spencer King of the Fuqua Heart Center in Atlanta, past-president of the American College of Cardiology, is somewhat skeptical of the latest findings, which he says might be due to differences in anti-platelet therapy from what's now the standard of care.
But if the work does hold up, King says it might make cardiologists think twice about placing stents in patients at high risk of clotting, since the complication is extremely serious. "You have to reopen the artery" immediately, which is a somewhat more dangerous procedure than the initial angioplasty, he says.
What To Do: For more on stenting and other heart-related therapies, visit the American Heart Association or the Heart Information Network.
