Several drug and device makers are participating in a $100 million, 20,000-patient study to figure out how to protect heart patients from blood clots after being treated with stents, The Wall Street Journal reports. At issue is whether patients can safely stop using blood thinners one year after a procedure or if they should take such a med for at least two and a half years.

Current guidelines call for patients who get a drug-coated stent to remain on the med for at least a year. But concern that, in rare instances, clots can form in the devices well over a year after they are implanted, with potentially lethal consequences, has left doctors and patients in a quandary over how long treatment should be prescribed, the Journal writes.

“It’s created a lot of anxiety in patients’ and physicians’ minds, not knowing the answer to the long-term safety question,” Laura Mauri, a cardiologist at Brigham and Women’s Hospital, Boston, who is co-principal investigator for the study, tells the paper. She is also chief scientific officer at Harvard Clinical Research Institute, which has been chosen by the companies to run the study, and here is her presentation at the Transcatheter Cardiovascular Therapeutics conference yesterday.

The companies involved are three stent makers - Boston Scientific, Johnson & Johnson and Medtronic - and four drugmakers - Bristol-Myers Squibb and Sanofi-Aventis, which currently market Plavix; and Eli Lilly and Daiichi Sankyo, which are developing prasugrel. The study stems from an FDA request for the companies to determine the optimal duration for blood thinning. “The results will lead to greater clarity of an extremely important problem,” Bram Zuckerman, an FDA official, tells the Journal.