Ultrastructural studies of unstable angina in living man.

Nineteen patients with refractory unstable angina who were undergoing aortocoronary bypass were studied to assess the extent of platelet aggregation present in the microvasculature. Ultrastructural findings on the morphology of cardiac muscle and microvasculature were correlated with the findings on coronary angiograms and thallium scans. There were no significant correlations. The presence of platelet aggregates was identified in four biopsies, two of which had thrombus by angiographic criteria. Biopsy in areas with thallium defects revealed an increased prevalence of white blood cells without acute myocardial infarction. This study confirms the presence of platelet aggregates in patients with unstable angina, albeit at a reduced frequency when compared with autopsy studies.