The purpose of the study was to define of the particularities of the morphology of platelets according to electron microscopy in patients with acute coronary syndrome without ST segment elevation with biochemical aspirin resistance. Among 140 patients with ACS without ST segment elevation after the determination of platelet aggregation with arachidonic acid (AA) aspirin resistance (AR) was determined in 15 patients (10.7 %).
Ultrastructure of platelets was studied in randomly selected 5 patients with and 5 without AR. Methods included the assessment of resistance and sensitivity to aspirin by identifying aggregation ability of platelets. We
determined morphometric platelet parameters, such as average area of platelet glycogen volume density, volume density of granules, numerical density of granules and their average area. It was established that
platelets of patients with AR compared with those of aspirin-sensitive patients had more average area, numerical density of granules at a lower volume density of the latter, which may be associated with less inhibition of thrombocytopoesis and increased functional activity of platelets.