Optimal platelet function test for in-stent tissue protrusion following carotid artery stenting

PURPOSE: To determine the best platelet function test for in-stent tissue protrusion following carotid artery stenting (CAS). METHODS: Patients who underwent CAS were recruited prospectively in this observational study. Combination of aspirin 100 mg/day and clopidogrel 75 mg/day was administered for a minimum of 7 days prior to procedure. Platelet aggregation was measured by light transmittance aggregometry (LTA) following stimulation by adenosine diphosphate (ADP), collagen, and thrombin receptor activating peptide (TRAP) and by the point of care assay, VerifyNow which measures aspirin and thienopyridine reaction units. RESULTS: In-stent tissue protrusion with maximum projection area of ≥1 mm(2) was detected by optical coherence tomography (OCT) in 10/28 (36%) patients. Baseline characteristics were not significantly different between the two in-stent size groups (i.e., ≥1 mm(2) vs. <1 mm(2)) but after stimulation by collagen at 10 and 20 μg/ml, platelet reactivity as measured by LTA was significantly higher in the ≥1 mm(2) group compared with the <1 mm(2) group. No other differences in platelet function were detected. CONCLUSIONS: Collagen-induced platelet reactivity was related to in-stent tissue protrusion size following CAS.