Stent thrombosis rates increase over time.

VIENNA -- The incidence of stent thrombosis following placement of drug-eluting coronary stents suggested a possibly rising, curvilinear incidence during 3 years of follow-up of more than 5,000 patients treated at one center.

However, it's unclear whether late stent thrombosis rates increased at a linear rate or accelerated in a curvilinear way, Dr. Gregory J. Mishkel said while presenting a poster at the annual congress of the European Society of Cardiology.

Almost half of the stent thromboses occurred a year or more after stent placement while patients were still on dual antiplatelet therapy, which suggests that extended treatment with aspirin and clopidogrel provides only partial, long-term protection, said Dr. Mishkel, codirector of the coronary catheterization lab at the Prairie Heart Institute at St. John's Hospital, Springfield, Ill.

The review included 5,342 patients at Prairie Heart who received their first drug-eluting coronary stent during May 2003--December 2006. Follow-up data were available for 5,173 (97%) of the patients; the average duration of follow-up was 1.8 years. Patients received an average of about 1.5 stents each; about 80% received sirolimus-eluting stents (Cypher) and about 20% received a paclitaxel-eluting stent (Taxus).

During follow-up, 50 patients had a definite stent thrombosis, 13 had a probable event, and 54 had a possible stent thrombosis. Among the 50 definite thromboses, 34 (68%) occurred a year or more after placement; 15 (44%) occurred while the patients were on dual antiplatelet therapy.

After the first 30 days, the rate of definite or probable stent thrombosis during the next 11 months was 0.2%. During the second 12 months of follow-up, the rate increased by 0.6%. During the last 12 months, the rate increased by another 0.7%, to a cumulative rate of 1.5%.

BY MITCHEL L. ZOLER

Philadelphia Bureau