Background: Numerous trials have reported on the morning increase in the occurrence of myocardial infarction, stroke and sudden cardiac death. Similarly, enhanced morning platelet aggregation has been observed in healthy individuals and in subjects with coronary artery disease without adequate antiplatelet treatment. The purpose of the study was to assess circadian variation in platelet aggregation in patients with first ST-elevation myocardial infarction (STEMI) treated with primary percutaneous coronary interventions (pPCI) and dual antiplatelet therapy.
Methods: Fifteen consecutive patients (12 men and 3 women) were prospectively recruited into the study. Blood samples were collected at 6.00 a.m., 10.00 a.m., 2.00 p.m. and 7.00 p.m. on the third day of hospitalization. Aggregation in response to arachidonic acid and adenosine diphosphate (ADP) was assessed in the whole blood on a new generation impedance aggregometer.
Results: A morning increase of 75% in ADP-dependent platelet aggregation was noted in the study population (p < 0.04). In contrast, we failed to show any significant diurnal variation in arachidonic acid-mediated platelet aggregation. The magnitude of the morning surge in platelet aggregation after ADP stimulation did not correlate with its baseline level.
Conclusions: Increased morning ADP-dependent platelet aggregation persists despite dual antiplatelet therapy in patients with first STEMI undergoing pPCI. The clinical significance of this finding remains to be demonstrated.