Stent thrombosis is relatively common, and treatment that includes placement of another stent increases the risk for further thrombosis, according to a late-breaking clinical trial presented at the meeting of the American College of Cardiology.

Jochem Wouter van Werkum, MD, a cardiologist at St Antonius Hospital, Nieuwegein, the Netherlands, led the Dutch Stent Thrombosis Study. He and his colleagues enrolled a total of 437 consecutive patients who had stent thrombosis confirmed by angiography between January 2004 and February 2007.

The researchers collected data on clinical characteristics (for example, diabetes, age and duration of antiplatelet therapy), angiographic characteristics (for example, undersizing of the stent, dissection and whether the lesion was located at an arterial branchpoint), and procedural characteristics (for example, whether a drug-eluting or bare-metal stent was used and the length and diameter of the stent).

The researchers found that 74 of the 437 patients (16.9 percent) experienced multiple episodes of stent thrombosis. Of these, 61 patients had two episodes of stent thrombosis, 12 patients had three episodes and one patient had four episodes.

Further analysis revealed three independent predictors of repeat stent thrombosis. Patients who had an additional stent implanted during emergency treatment for the first episode of stent thrombosis were 4.2 times as likely as other patients to experience a repeat episode of stent thrombosis. Patients with a previous myocardial infarction faced 2.6 times the usual risk of repeat stent thrombosis, and patients who developed thrombosis long after stent implantation (late stent thrombosis) faced 2.1 times the usual risk of a repeat episode.

Dr. van Werkum and his colleagues concluded that additional stent placement at the time of emergency treatment for the first stent thrombosis should be avoided.