Check Up: Study: Have a stent? Take aspirin, and don't smoke

The seven patients all had had successful surgery to prop open a blocked coronary artery with a stent.

Yet more than five years later, all seven developed dangerous blood clots and came to Thomas Jefferson University Hospital with heart attacks.

The common thread? All of them either had stopped taking aspirin, were actively smoking, or both, according to a new report by Jefferson physicians.

Not a good idea, the doctors wrote in September's Journal of Invasive Cardiology.

"Even years later, you have to do the right thing and take care of yourself," said cardiologist Michael P. Savage, the report's senior author.

The seven patients all had been implanted with drug-eluting stents - the kind coated with material that releases medicine internally to minimize the formation of harmful scar tissue.

The potential pitfall in such cases is that because the artery heals more gradually, the stent remains exposed in the bloodstream for a longer period, said Savage, a professor of cardiology at Jefferson and director of the hospital's cardiac catheterization lab.

"Foreign materials in blood vessels tend to be magnets for blood clots," Savage said.

This is why patients are commonly instructed to take the anti-clotting drug clopidogrel, marketed as Plavix, for at least one year following the implantation.

In addition, they are advised to take aspirin indefinitely, as it, too, has an anti-clotting effect, and they are told not to smoke. Smoking appears to make the blood more likely to form clots, and can trigger an arterial spasm that leads to blockage, Savage said.

Six of the patients were active smokers, according to case histories presented in the paper. Five of the patients had stopped taking aspirin, although two of those had a valid reason: they were scheduled for unrelated surgery, and their physicians had told them to stop aspirin in order to prevent excessive bleeding.

Due to the potential for blood clots, however, orthopedic surgeons are increasingly performing surgery while the patient remains on aspirin, Savage said.

None of the seven was still taking Plavix at the time of the heart attack, though Savage said that was not surprising, given the professional guidelines that mandate its use for just one year.

In an accompanying commentary in same issue of the journal, another team of physicians urged research to determine if certain patients might be candidates for indefinite use of both aspirin and Plavix.

One way to tell if a stent remains exposed in a particular patient is to use a type of imaging called optical coherence tomography, said Renu Virmani, one of the commentary authors. She is a pathologist at CVPath Institute, a nonprofit research organization in Gaithersburg, Md.

The formation of clots on stents is called stent thrombosis. This phenomenon has previously been observed within the first few months or years after stent placement, but the Jefferson team said it was the first to document a whole series of patients with clots that occurred more than five years afterward.

Savage cautioned that the stents in this study were first-generation. Newer models are made with different metals and coatings that appear to reduce the risk of clots.

Whatever the type of stent, aspirin is a wise idea unless a patient has some other medical reason to avoid it, Savage said. Especially with the older stents, some may never be fully covered by new tissue, he said.

"Our series suggests we can never assume that it's safe" to stop taking aspirin, he said. "Don't think that you're cured. Continue to do the right thing."

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