Patients fitted with heart stents may need to use blood thinner for longer

Millions of people with stents that prop open clogged heart arteries may need anti-clotting drugs much longer than the one year doctors recommend now.

A large study found that continuing for another 18 months lowers the risk of heart attacks, clots and other problems.

Even quitting after 30 months made a heart attack more likely, raising a question of when it's ever safe to stop. It's a big issue because the drugs can be expensive and bring risks of their own.

"It's a wake-up call. It's the opposite of where we've been going," said Dr Patrick O'Gara, clinical cardiology chief at Brigham and Women's Hospital in Boston and president of the American College of Cardiology.

Brigham's Dr Laura Mauri led the study at the request of the federal Food and Drug Administration. Results were discussed on Sunday at an American Heart Association conference in Chicago and published online by the New England Journal of Medicine.

The FDA says it is mulling the results and that doctors should not change practice yet.

The study concerns care after angioplasty, a procedure done on millions of people worldwide each year. Doctors push a tube through a blood vessel to the clog, inflate a tiny balloon to flatten it, and place a mesh tube called a stent to keep the artery open.