Effect of pre-infarction angina on platelet reactivity in acute myocardial infarction

Background: Previous studies demonstrated that patients with PIA have a smaller infarct and better in-hospital outcome after acute myocardial infarction, than those without angina. This protective effects has been attributed to ischemic preconditioning (PC), to earlier reperfusion after fibrinolysis or its better collateral circulation development. In this study we aimed at assessing platelet reactivity in patients with history of pre-infarction angina (PIA) in the acute phase of ST segment elevation myocardial infarction (STEMI) and 1 month later. Methods: 85 consecutive patients (63 ± 10.5 years, 60 male) with a first STEMI treated by primary percutaneous coronary intervention (PCI) were studied at admission and 1 month later. Platelet reactivity was evaluated by flow cyometry with and without adenosine diphosphate (ADP) stimulation, by measuring monocyte-platelet aggregates (MPAs) and glycoprotein IIb/IIIa (CD41) expression in the MPA gate, and CD41 and fibrinogen receptor (PAC-1) expression in the platelet gate. Results: MPAs and expression of platelet receptors CD41 and PAC-1 were significantly lower in patients with than patients without PIA, both with and without ADP stimulation. After 1 month, all cytometry variables both with and without ADP stimulation were similar in the two groups. Conclusions: This study shows, for the first time, that patients with a first STEMI who experience PIA show a lower platelet reactivity as compared with those without history of PI