Repeat blood clots more common with stents: study

CHICAGO (Reuters) - Treating a stent-related blood clot with an additional stent in an emergency procedure sharply raises the risk that a patient will get a second clot and should be avoided, Dutch researchers said on Saturday.

One in six patients who suffer a potentially deadly clot inside a coronary stent risk developing another clot, especially if they had a second stent implanted during emergency treatment for the first clot, the Dutch Stent Thrombosis Study said.

The study, led by Dr. Jochem Wouter van Werkum of St. Antonius Hospital in Nieuwegein, the Netherlands, was presented at a joint meeting of the American College of Cardiology and the Society for Cardiovascular Angiography and Interventions in Chicago.

Stents are wire mesh tubes inserted into the coronary arteries that supply blood to the heart. They help keep the vessels from reclogging after they have been cleared of blockages in an angioplasty procedure.

Clots that form inside a stent, also known as stent thrombosis, can block blood flow to the heart and cause a heart attack or even death.

Use of an additional stent during emergency treatment of a stent-related blood clot is a strong predictor of repeat stent thrombosis, the researchers said.

Patients in the study who had a second stent implanted during emergency treatment for their first clot were 4.2 times as likely as other patients to endure another episode of stent thrombosis.

Patients who previously had a heart attack were 2.6 times as likely, and those who developed a clot long after stent implantation, known as late stent thrombosis, were 2.1 times as likely to suffer a repeat episode.

The study looked at 437 patients with various kinds of stents who had stent thrombosis between January 2004 and February 2007.

It found 16.9 percent of the patients had multiple episodes of stent thrombosis -- 61 patients had two episodes, 12 had three episodes and one had four episodes.

(Reporting by Susan Kelly; Editing by Xavier Briand)