VIENNA, Sep 3 (Reuters) Drug-coated stents -- tiny wire-mesh tubes used to prop open clogged heart arteries -- may not be as dangerous as previously thought, Swedish researchers who had earlier raised concerns over the devices said.

Fears that patients might do worse on so-called drug-eluting stents than on older bare metal ones have led to a 1 billion dollars slump in sales in the past year, hurting leading manufacturers like Boston Scientific and Johnson&Johnson.

But according to new four-year data from a 35,000-patient Swedish database of stent procedures, the largest in the world, patients receiving drug-coated stents are not at higher risk of dying or having a heart attack.

The new findings, presented at the annual meeting of the European Society of Cardiology, represent an about-turn by the Swedish research group.

''This is good news for patients,'' Stefan James of the Uppsala Clinical Research Centre in Sweden told reporters.

Last December, a three-year analysis of medical records of every patient who got a stent in Sweden in 2003 and 2004 had concluded that patients with drug stents were roughly 18 percent more likely to die within three years than those who got bare stents.

James said an analysis of additional data from 2005 had changed the picture and there was now no statistical difference between the two groups.

While drug stents do carry a small increased risk of blood clots after the first year -- something known as late stent thrombosis -- this was offset by better outcomes in the early months following implantation, James told reporters.

BETTER STENTS? The improvement in outcomes after four years compared with the picture at three years might be due to increased use of blood-thinning drugs, more careful implantation, better selection of patients or better stents, he said.

Some early stents had to be recalled due to manufacturing problems.

Worries over late stent thrombosis blew up a year ago at the European Society of Cardiology meeting in Barcelona, badly shaking confidence in the technology.

As a result, Bank of America analysts estimate the world market for drug-coated stents will plunge by more than 1 billion dollars this year to 4.3 billion dollars.

The latest more reassuring picture suggests the proportion of drug-coated stents, which help prevent arteries narrowing again, could now start to stabilise.

James's data showed the rate of late stent thrombosis with drug stents was 0.5 per cent a year, while the risk of arteries renarrowing at the end of the four-year period was reduced to around 3.5 per cent compared to 7 per cent for bare stents.

In Sweden, drug-eluting stents' share of the overall stent market fell from more than 50 per cent to current levels of just 15-20 per cent, James said. He predicted it could now level out at around 20 per cent.

CONTROVERSY Bob Bonow, head of cardiology at Northwestern University and a spokesman for the American Heart Association, said doctors were now being more selective about using drug stents.

''The use of drug-eluting stents on both sides of the Atlantic has declined somewhat,'' he said.

''There's probably more awareness among doctors that drug-eluting stents are not for everyone.'' Coated stents cost around three times more than bare metal ones.

The market leaders are Boston Scientific's Taxus stent and Cypher from Johnson &Johnson, while newer rivals include Medtronic's Endeavour and Abbott's Xience V.

In Europe the high cost of and mixed clinical outcomes for coated stents have caused a rethink by some regulators.

Britain's cost-effectiveness watchdog the National Institute of Health and Clinical Excellence last month proposed stopping payments for drug stents, to the concern of manufacturers. NICE argued the 1,212 dollars premium charged for drug stents as compared with bare ones was not justified by their benefits.

Reuters GL GC0900