Platelet Reactivity Status Predicts Ischemic Event Risk

High residual platelet activity after clopidogrel loading predicts post-PCI risk of ischemic events

TUESDAY, Sept. 20 (HealthDay News) -- High residual platelet reactivity (HRPR) after clopidogrel loading is significantly associated with an increased risk of short- and long-term ischemic events in patients receiving platelet reactivity-guided antithrombotic medication after percutaneous coronary intervention (PCI), according to a study published in the Sept. 21 issue of the Journal of the American Medical Association.

Guido Parodi, M.D., from the Careggi Hospital in Florence, Italy, and colleagues investigated whether HRPR after clopidogrel loading independently predicts the risk of long-term thrombotic events in 1,789 patients with acute coronary syndrome undergoing PCI from April 2005 to April 2009. Participants received 325 mg of aspirin, a loading dose of 600 mg of clopidogrel, and a subsequent maintenance dosage of 325 mg/day of aspirin and 75 mg/day of clopidogrel for at least six months. Based on adenosine diphosphate testing, patients identified with HRPR received 150 to 300 mg/day clopidogrel or 500 to 1000 mg/day ticlopidine. A composite of cardiac death, myocardial infarction, any urgent coronary revascularization, and stroke at two-year follow-up was the primary end point, and stent thrombosis and each component of the primary end point were the secondary end points.

The investigators found a primary end point rate of 14.6 and 8.7 percent in patients with HRPR and low residual platelet reactivity, respectively (absolute risk increase, 5.9 percent). The HRPR group had higher stent thrombosis than the low residual platelet reactivity group (6.1 versus 2.9 percent; absolute risk increase, 3.2 percent). HRPR correlated independently with the primary end point and with cardiac mortality (hazard ratio, 1.49 and 1.81, respectively), in multivariable analysis.

"HRPR status was significantly associated with increased risk of ischemic events at short- and long-term follow-up," the authors write.

Several of the study authors disclosed financial ties to the pharmaceutical and medical device industries.

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