Morphological and Immunoenzymatic Characteristics of Aspirated Thrombi in Patients with ST-Elevation Myocardial Infarction

The aim of the study was to evaluate the morphological and immunohistochemical characteristics of aspirated thrombi in patients with ST-elevation myocardial infarction undergoing percutaneous coronary intervention to find the possible platelet activation and inflammatory cell involvement in coronary thrombi.
Thrombi collected from 67 patients were studied. Macroscopic analysis was performed and immunoenzymatic methods were used to reveal the cellular components of thrombi. The peroxidase-antiperoxidase immunohistochemical method was applied with monoclonal antibodies to CD4, CD8, CD15, CD63 and CD105 using diaminobenzidine as a visualization agent to investigate the potential involvement of different cellular subpopulations.
The macroscopic examination revealed friable thrombi with apparent laminations (lines of Zahn), which represent pale platelet and fibrin deposits alternating with darker red blood cellrich layers. The microscopic examination of thrombi revealed a loose meshwork of fibrin fibers, with compact accumulation of activated platelets. The platelets were surrounded by neutrophil granulocytes. The immunophenotyping analysis confirmed cell aggregates consisting of CD63+ activated platelets. The surrounding neutrophils were also CD63+. The granulocytes also tested positive for CD15 antigen. The immunohistochemical analysis revealed the presence of CD8+
cytotoxic T-lymphocytes and CD4+ helper T-lymphocytes. No expression of iNOS, CD105 and VEGF was revealed in the analyzed thrombi.
The histopathological evaluation of thrombi in patients with acute ST-elevation myocardial infarction revealed the presence of activated CD63+ platelets and CD15+ neutrophilic granulocytes. Activated platelets and neutrophils may play a role in thrombo-inflammatory activation process leading to destabilization of atherosclerotic plaque and development of acute thrombosis in the patients with ST-elevation myocardial infarction.