Drug-eluting stents are safe and effective for use in patients who have had a severe heart attack, but the potential risk of blood clots needs more study before the devices are recommended for all heart attack patients, according to an editorial in a major medical journal.

The editorial, which will appear in The New England Journal of Medicine September 14 issue, accompanies two large studies that evaluated the benefits of newer, more expensive drug-eluting stents versus bare-metal stents as a treatment for patients with severe heart attacks.

Since their introduction in 2003, nearly 6 million heart patients worldwide have received a drug-eluting stent, a tiny wire-mesh tube infused with drugs to keep blood flowing through diseased heart arteries.

The studies and editorial come as companies defend their devices against evidence that drug-eluting stents may cause blood clots more than six months after stents are implanted, a complication called late-stent thrombosis.

Boston Scientific Corp. said last week that an internal analysis confirmed an increased risk of late-stent thrombosis with its Taxus drug-eluting stent, which the company said was a problem with the whole class of stents.

But the company said on Wednesday it found no link to more serious health problems.

“While we have seen a small increase in very late stent thrombosis with Taxus, we have seen no corresponding increase in heart attack or death,” Boston Scientific spokesman Paul Donovan said.

In a study funded by Johnson & Johnson appearing in the journal, the company’s Cypher stent was significantly better at keeping blood flowing through the arteries of a heart attack victim when compared with bare-metal stents.

A second independent journal study that used Taxus found no statistical benefit of drug-eluting stents over uncoated stents.

A second editor by Frans Van de Werf of the University of Leuven in Belgium cautioned that “it would be dangerous to conclude from these data that one drug-eluting stent is better than the other” because the two brands were not compared in head-to-head.

Van de Werf noted the rate of repeat procedures for patients with bare-metal stents was higher in the J&J trial than the trial involving the Boston Scientific stent, which might explain why the J&J’s Cypher stent met statistical significance while Boston Scientific’s Taxus did not.

Drug-eluting stents in both studies had “remarkably similar” rates of revascularization, or the need for a second procedure to open blockages, he noted.

In the study of the Boston Scientific device, the Taxus stent had one case of late-stent thrombosis versus none in the bare-metal stent arm. In the J&J trial, the Cypher stent had one case of late-stent thrombosis, compared with two in the bare-metal arm.

The full results of both large tests were released in March at a meeting of the American College of Cardiology.

SOURCE: The New England Journal of Medicine, September 14, 2006.