Platelet Responsiveness to Aspirin Loading in Patients with ST Elevation MI Undergoing Primary Percutaneous Intervention Is Associated with Myocardial Reperfusion and Clinical Outcome.

Background: In patients with stable coronary artery disease, and patients undergoing elective percutaneous coronary intervention (PCI), laboratory resistance to aspirin is associated with a higher incidence of adverse events. Nevertheless, the responsiveness to aspirin in acute myocardial infarction (AMI) and its implications have not yet been investigated.

Methods: The study comprised 76 aspirin naïve patients who underwent primary PCI (PPCI) for ST-elevation MI (STEMI). Platelet reactivity was assessed 30–60 mins after a loading dose of 300mg chewable aspirin, by conventional aggregometry and Impact R, where platelet reactivity to arachidonic acid (AA) was expressed by platelet deposition under flow conditions.

Results: Patients were stratified using the median value of AA-induced platelet aggregation (PA) (49%) to good responders to aspirin (n=38), who had a median AA-induced PA of 33% (25–41), and poor responders to aspirin (n=38), who had a median AA-induced PA of 77% (70–84). Similarly, good compared with poor responders had higher surface coverage by Impact R (3.9±2.6 vs. 2.2±1.3, p=0.003). Good versus poor responders were similar regarding baseline demographic, clinical and angiographic characteristics. However, good responders were more likely to demonstrate early ST-segment resolution ≥ 70% after PPCI (84% vs 54%, p <0.01), suggestive of better myocardial reperfusion. Good compared to poor responders had a lower incidence of adverse cardiovascular events (re-infarction, need for re-intervention, congestive heart failure and/or death) throughout a 6-month follow-up (11% vs 24%, respectively; p<0.05).

Conclusions: Ex vivo poor platelet responsiveness to aspirin loading in STEMI patients is associated with a worse prognosis in patients