Enhanced Shear-Induced Platelet Aggregation in Patients Who Experience Subacute Stent Thrombosis

OBJECTIVES: The goal of this study was to identify differences in shear-induced platelet aggregation (SIPA) between patients who did or did not experience subacute stent thrombosis (SAT). BACKGROUND: Despite dual antiplatelet therapy, SAT after coronary stenting occurs in approximately 1% of patients. There is no accepted platelet function test to identify patients at risk. METHODS: We analyzed platelet aggregation in 10 patients who had experienced SAT (cases), 22 stented patients without SAT (controls), and 17 healthy volunteers (normals). All patients except normals were treated with both aspirin and clopidogrel. RESULTS: Shear-induced platelet aggregation was higher in cases than in controls at both shear rates of 200 s(-1) (40.9 +/- 12.2% vs. 18.2 +/- 18%, p = 0.013) and 4,000 s(-1) (57.4 +/- 16.4% vs. 23.4 +/- 21.2%, p = 0.009). Moreover, SIPA in cases was significantly higher than in normals both at 200 s(-1) (p = 0.013) and 4,000(-1) (p = 0.009). CONCLUSIONS: Shear-induced platelet aggregation is increased in patients experiencing SAT compared with controls receiving dual antiplatelet therapy and to normals receiving no antiplatelet therapy, which suggests increased intrinsic patient-related platelet reactivity in patients with SAT. The predictive value of SIPA for SAT requires prospective investigation.