Background an Objective Antiplatelet therapy with clopidogrel and aspirin is the current standard of care for patients undergoing PCI. However, recurrent ischemic event occurrence during dual antiplatelet therapy, including stent thrombosis, remains a major concern. We sought to determine whether clinical characteristics will be associated with high on-treatment platelet reactivity receiving clopidogrel measured by thrombelastography.

Methods A total of 362 consecutive patients undergoing non-emergent PCI were enrolled in this prospective observational study. A 300mg clopidogrel loading dose was administered on the day before procedure ( > 12h). Blood samples were analysed using a computerised TEG analyser for platelet aggregation. The cut points for high on-treatment platelet reactivity (HPR) were defined as ≥60% ADP-induced aggregation with 2-μmol ADP. All patients below the cut point were defined as exhibiting normal on-treatment platelet reactivity (NPR).

Results The prevalence of HPR was 33% measured by TEG. There were more female (41.7% vs 22.3%, P = 0.007), more diabetes mellitus (41.7% vs 24.2%, P = 0.0024) and more smoking patients (12.3% vs 2.6%, P = 0.012) in HPR group than in NPR group, respectively. Meanwhile, elevated plasma triglyceride was common in HPR group than in NPR group (2.5 ± 0.9mmol/L vs 1.9 ± 0.3mmol/L, P = 0.019). Patients with HPR exhibited a higher level of cardiac enzyme including CK-MB (3.1 ± 1.3ng/mL vs 1.8 ± 1.6ng/mL, P = 0.013) and troponin I (0.9 ± 0.3ng/mL vs 0.2 ± 0.4ng/mL, P = 0.01).

Conclusions Despite adequate pretreatment with clopidogrel, 33% patients undergoing non-emergent PCI exhibited high on-treatment ADP-induced platelet aggregation measured by thrombelastography. We found that current smoking, high level of HbA1C and TnI, and female gender independently predicted the risk of HPR.