BOSTON (Reuters) – Heart stents coated with drugs are just as safe as uncoated ones and appear to keep blood flowing to the heart muscle longer, dispelling earlier concerns about their safety, Swedish researchers said this week. A study by the same researchers in December 2006 found people who got the so-called drug-eluting stents were 18 percent more likely to die within three years.

That sent sales of the devices, made by Boston Scientific and Johnson & Johnson, into a tailspin.

In September 2007, the Swedish team reported the safety difference between drug-eluting and bare-metal stents had evaporated. But the damage had been done as sales had slumped by $1 billion.

Now, long-term results from the study, led by Dr. Stefan James of Uppsala University Hospital in Sweden and published in the New England Journal of Medicine, confirm that the risk of death or heart attack is no greater among those who got drug-eluting stents or older, bare-metal stents.

Stents are tiny, mesh tubes used to prop open diseased heart arteries. Drug-eluting stents have medicine added to them to prevent scar tissue from clogging up the device, a common problem with the older, bare-metal variety. Results from the Swedish study of nearly 48,000 patients now suggest the devices work as promised, especially in high-risk patients, who had a 74 percent lower risk of having a clogged stent compared with similar patients who got a bare metal stent.

Professor Franz Eberli from the University Hospital Zurich in Switzerland, said the original study caused "a huge fire storm" when it was first presented at a cardiology meeting in Barcelona in 2006. "The immediate impact was a decrease in the use of drug-eluting stents and a lot of scrutiny on safety," he said in a statement. Eberli said the latest paper looking at the same group of patients "provides a lot of reassurance."

A smaller study in the same journal looking at how the devices performed in heart attack patients showed no difference in the risk of death or heart attack.

That study found the drug-eluting stent did a better job than bare-metal stents of keeping blood vessels flowing freely.

"Our study is in the highest-risk patients and it's a randomised trial. The Swedish study is important because it's a 'real-world' study that included all comers," Dr. Gregg Stone of Columbia University Medical Center said. Stone's study, supported in part by a grant from Boston Scientific, involved 3,602 people at 123 medical centres in 11 countries who used the company's Taxus-brand stents.