Drug-eluting stents are small metal tubes implanted in blood vessels to help prop open clogged arteries after they have been cleared. Coating the stents with a drug can reduce the growth of scar tissue that can gradually clog arteries and lead to a heart attack. Yet recently, researchers are finding that drug-coated stents increase the odds of a blood clot when compared with bare metal ones.

In response, the FDA convened a panel in Washington to look at recent data surrounding the more than $5 billion drug-coated-stent industry. In particular, research is pointing to a small but significant increase in the rate of death and heart attack that might be caused by stent thrombosis -- a blood clot in the stent -- in patients with drug-coated stents.

The panel's conclusions about the stents were mixed, however. The studies show that most patients with drug-coated stents have some increased risk of heart attacks and death, but it's unclear whether this is because of poor health or the devices themselves.

It seems that for about 40% of those using the stents, the blockage involves just one artery, and the patient's heart is not significantly damaged. That's what the FDA envisioned when it approved the stents. And in those cases, the panel says the benefits of the stents outweigh any clotting danger.

But the remaining 60% are cases in which multiple arteries are blocked, the patient has already suffered a serious heart attack, or other complications are involved. In these more complex cases, the panelists were not confident that the benefits outweigh the risk of blood clots. These included cases not originally studied before the devices received FDA approval, such as patients whose arteries are narrower or more damaged, or who receive overlapping or multiple stents in a single blood vessel -- so-called off-label uses.

The panel concluded that the drug-coated stents are safe when used with healthier patients who have less complex problems but may put patients at risk for blood clots. Therefore, the panelists recommended that stent patients take blood-thinning drugs for at least a year. They also recommended that the labels on the devices should be updated to warn doctors that off-label use won't give the same results as seen in generally simpler cases involving healthier patients.

In the end, Boston Scientific (NYSE:BSX) and Johnson & Johnson (NYSE:JNJ), should not see a significant change in their sales of the stents as a result of the recommendations. Because the panel also recommended that the FDA require companies looking to bring new drug-coated stents to market to carry out longer and larger clinical trials, things may slow down at Medtronic (NYSE:MDT) and Abbott Laboratories (NYSE:ABT). There's one more concern, though: the increase of class action lawsuits against companies involved in making the stents.

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Fool contributor Stephen Albainy-Jenei is a patent attorney serving up chat at PatentBaristas.com. Stephen does not own shares of any company mentioned in this article. The Fool has an ironclad disclosure policy.