In testimony before the Food and Drug Administration (FDA), Gregory J. Dehmer, MD, president of the Society for Cardiovascular Angiography and Interventions (SCAI), today urged a review panel to evaluate new data on the safety of drug-eluting stents (DES) from the perspective of prior developments in the history of coronary intervention, and with an appreciation for the balance of benefits and risks that guides all clinical decision-making.
As president of SCAI, Dr. Dehmer spoke on behalf of the professional organization representing the vast majority of physicians who perform invasive cardiac procedures, including the placement of coronary artery stents. “SCAI has been ? and will continue to be ? at the forefront in providing guidance to physicians regarding the use of drug-eluting stents,” said Dr. Dehmer, who cited the Society?s proactive role in publishing clinical alert documents on drug-eluting stents and other therapies for patients with heart disease.
Drug-eluting stents were approved by the FDA in 2003. These devices, which prop open narrowed arteries in the heart, are coated with a medication that prevents the build-up of scar tissue inside the stent. Drug-eluting stents have proven so successful in preventing renarrowing of the artery ? or restenosis ? they were being used in 80 to 90 percent of stent procedures, thereby sparing patients the need for a repeat procedure to restore blood flow through a constricted artery.
A new concern has arisen, however. Several recent analyses that tracked patient outcomes for four to five years after stent placement showed that blood clots appear slightly more likely to form inside a drug-eluting stent than in a bare metal stent. When this occurs, the patient may suffer a heart attack or even die. “Clearly, this unexpected new observation is worrisome, but it must be evaluated in the proper context,” said Dr. Dehmer, who has practiced as an interventional cardiologist for more than 25 years and is a professor of medicine at the Texas A&M University College of Medicine and director of the Cardiology Division at the Scott & White Clinic.
Because data are limited, the precise rate of delayed blood clot formation?known as late stent thrombosis?is unknown. Current information suggests it is small, however, representing 1 additional case of late stent thrombosis per every 200 to 500 patient-years in those treated with a drug-eluting stent, over what would be expected with a bare metal stent.
This must be weighed against the substantial benefits of drug-eluting stents, Dr. Dehmer said. Simply put, patients who avoid renarrowing of their coronary arteries as a result of drug-eluting stent placement avoid the need for repeat procedures, which themselves have small but definite risks.
Dr. Dehmer pointed out that it is common for challenges to arise after introduction of a new medical technology, and for its use to evolve over time. Bare metal stents, for example, reduced the risk of restenosis by half, as compared to conventional balloon angioplasty, and were greeted with widespread enthusiasm. But restenosis within a stent was very difficult to treat, prompting the introduction of internal radiation of the coronary arteries, a technique that had its own set of problems, including late stent thrombosis.
“It is difficult to think of any area in medical care where challenges ? and solutions ? did not occur during introduction of a new therapy into practice,” Dr. Dehmer said. “We are now faced with a possible problem with drug-eluting stents ? late stent thrombosis. Like all of the problems that preceded it, this too will have a solution.”
Finally, medical decision-making has always been guided by the balance between benefit and risk, Dr. Dehmer said. As an example, he pointed to the well-established benefits of aspirin for preventing heart attack and stroke in patients with heart disease. Aspirin can cause gastrointestinal complications, including death in a very small percentage of patients. “However, for the vast majority of patients, the benefits of aspirin therapy outweigh the risks,” Dr. Dehmer said. “Likewise, with drug-eluting stents we now need a thoughtful assessment of the risks versus the benefits.”
SCAI has previously published a position paper on drug-eluting stents followed by a task force report and is developing a third?a clinical alert to be released later this month. For now, the Society has developed the following recommendations:
A drug-eluting stent should be used only when, in the judgment of the interventional cardiologist, the benefits of preventing restenosis in a particular lesion outweigh the risks of late stent thrombosis;The patient must be an appropriate candidate for drug-eluting stent therapy; specifically, being willing and able to take two different anti-clotting medications for a minimum of six months after stent implantation;The drug-eluting stent must be implanted properly, with particular attention to stent sizing, expansion, and fit against the artery wall; and Both patients and physicians must be educated as to the importance of adhering to therapy with dual anti-clotting medications.
Further research is needed to determine the exact incidence of late stent thrombosis in patients treated with drug-eluting stents, Dr. Dehmer said. It is also important to determine why some patients develop this problem but many others do not, so physicians can better understand how to care for their patients.