'If there were huge clinical differences between the two devices, I think at this point you'd know them already,' says a cardiac catheterization specialist.

An article in today's issue of the Journal of the American Medical Association that analyzed several previous studies said patients who received a Taxus drug-coated stent were 50 percent more likely to undergo another artery procedure than those who received the Cypher device made by Johnson & Johnson.

Two other studies to be published in tomorrow's issue of the New England Journal of Medicine also compare the stents head-to-head, with both reports showing a narrow advantage for Johnson & Johnson.

Because the articles are based on data already presented to cardiologists, they are more likely to nudge doctors toward Cypher than trigger a dramatic shift in practice, said several heart specialists.

Fiercely Contested Multibillion Dollar Market

"For the overwhelming majority of patients it shouldn't be an issue," said David J. Moliterno, a University of Kentucky cardiologist who wrote an editorial in the New England Journal of Medicine commenting on the two studies.

While Cypher might be used more often in complicated cases, Moliterno said, "for the common or everyday blockages, either stent would be adequate."

Stents are tiny wire mesh tubes designed to be inserted into coronary arteries that have been cleared of blockages. Cypher and Taxus devices are coated with a slow-leaking drug that helps keep arteries clear. But they use different drugs and come with different systems to help doctors place them in troubled vessels.

Other studies have shown both stents are far better than earlier devices at keeping patients out of the hospital after cardiac surgery.

"It's like wondering whether a 2006 Audi or BMW is better," said Moliterno, who said his lab usually uses Taxus stents because they are less expensive and more readily available.

But in the fiercely contested multibillion dollar market for one of the world's fastest-selling medical products, the articles in the two most prestigious American medical journals are likely to become part of Johnson & Johnson's sales pitches to doctors.

"It's kind of becoming a marketing war," said Dr. Carey Kimmelstiel, director of the cardiac catheterization lab at Tufts-New England Medical Center. "If there were huge clinical differences between the two devices, I think at this point you'd know them already."

Differences Were Small but Statistically Significant

The studies looked at the health of patients' arteries after the implant procedure and the likelihood that narrowing arteries would force a repeat procedure. Overall, the differences were small but statistically significant.

According to the Journal of the American Medical Association paper, in which a German research group analyzed six previous studies, patients with the Boston Scientific stent had a 7.8 percent chance of needing another procedure on the artery where the stent was installed. Patients with Cypher stents, made by the Cordis unit of Johnson & Johnson, had a 5.1 percent chance of needing another operation.

The New England Journal of Medicine published two studies that are included in the association's analysis, one looking at 250 diabetic patients and the other examining about 1,000 coronary patients who received stents.

In his accompanying editorial, Moliterno wrote that the Johnson & Johnson stents hold a "clinical edge" over the Boston Scientific stents, but pointed out that Boston Scientific "holds an edge on availability, deliverability, and cost."

The procedure to clear arteries and install stents is one of the most common surgeries performed in the United States. Johnson & Johnson introduced the first drug-coated stent in 2003 and the new generation of the devices now dominates the stent market. Boston Scientific introduced Taxus in 2004, taking advantage of supply problems at Johnson & Johnson to become the world's largest stent maker.

Taxus now holds about 60 percent of the $3.3 billion US market in drug-coated stents, according to analysis done by SG Cowen.

In a statement yesterday, Boston Scientific criticized the scientific standards of the studies published this week in the medical journals.

"Most of this data would not meet the top standard established by the major cardiology societies for determining treatment guidelines for interventional cardiology," said Boston Scientific spokesman Paul Donovan.