Boston Scientific Corp. says a new internal analysis of its clinical data confirms an increased risk of blood clots with its drug-coated cardiac stent, the Wall Street Journal reported Thursday.

The company said there is a statistically significant difference in the rates of blood clots appearing in a stent months after implantation, when comparing its Taxus stent with earlier-generation, bare-metal stents, the newspaper reported.

Boston Scientific's Canadian partner on stents is Angiotech Pharmaceuticals Inc.

The Journal said the acknowledgment was the first by a stent maker of an increased risk of the side-effect and that it came just days after experts meeting at the World Cardiology Congress in Barcelona, Spain, expressed concerns that drug-coated heart stents may in rare instances lead to potentially fatal blood clots.

The drug-coated stents — metal-mesh tubes used to prop open coronary arteries — were introduced in 2000 as an improvement on bare-metal stents.

Nearly six million people worldwide now have the drug-lined versions from the two dominant drug-coated stent makers, Boston Scientific, which is based in Natick, and New Jersey-based Johnson & Johnson. The devices are intended to keep arteries open after having been cleared of fatty deposits and are often credited with saving patients from future heart attacks or bypass surgery.

"The right thing for us to do as responsible manufacturers is, when we have evidence of an issue, to go forward with regulators," Donald Baim, Boston Scientific's chief medical officer, told the Journal.

The company says it believes the clot problem, known as "late stent thrombosis," isn't unique to its product and that recent studies suggest that both its Taxus brand of stent and J&J's Cypher stent have a similar additional risk of late blood clots. The Journal said J&J has said it sees no statistically significant risk of late thrombosis in Cypher.

According to Boston Scientific, its internal analysis was done June 24 and the "significant finding" of added clotting risk prompted officials to seek a meeting with the Food and Drug Administration, which took place Aug. 1. The findings were also shared with European regulators last week, Baim said.

An FDA spokeswoman said in an e-mail to the Journal that the agency couldn't "confirm or discuss or even acknowledge confidential discussions with regulated firms."