Abstract 39: Platelet Reactivity to Prostaglandin E2 is a Novel Modifiable Risk Factor for St-Elevation Myocardial Infarction

Background: Patients with lower thresholds for platelet activation are at increased risk for primary and recurrent myocardial infarction (MI) and overall cardiovascular (CV) mortality. We have demonstrated that there are two phenotypes of platelet response to Prostaglandin E 2 (PGE 2 ), such that it increases threshold for aggregation in 45% of individuals (inhibitory) and lowers threshold for aggregation in 55% (potentiating). As PGE 2 is present in atherosclerotic plaques, and its receptors are present on platelets, biologic variability in PGE 2 responses may have clinical implications. We hypothesized that patients with higher thresholds for platelet activation would have a lower risk of thrombotic CV events, specifically ST-Elevation MI (STEMI). Methods: 85 patients undergoing percutaneous coronary intervention for stable or unstable coronary disease were phenotyped for PGE 2 response. Platelet rich plasma was treated with various concentrations of U46,619 (thromboxane agonist) with or without PGE 2 100 nM, and phenotype determined by light aggregometry. Analysis of the maximum PGE 2 effect (maximum aggregation with PGE 2 minus maximum aggregation without it) was performed using linear and non-linear statistical methods. Results: Traditional cardiovascular risk factors were similar between groups. A higher percentage of patients with the potentiating phenotype had a history of STEMI than those with the inhibitory phenotype. Logistic regression using restricted cubic spline showed that the predicted probabilities of STEMI increased from 0.04 (at the strongest inhibitory phenotype) to 0.43 (at the median phenotype). The OR of phenotype at the median relative to that at the 10th quantile was 7.4 (95 % CI=1.6, 34.8). Conclusions: PGE 2 inhibitory phenotype confers a decreased lifetime risk of STEMI in individuals at high risk for CV events. We have previously shown that an EP3 receptor antagonist converts the potentiating to the inhibitory phenotype. Thus, the PGE2 phenotype may be a novel marker of cardiovascular risk that may also identify patients who would benefit from an EP3 antagonist.