Correlates of unrecognized acute myocardial infarction detected via perfusion imaging

Research using the electrocardiogram (ECG) indicates that about 1/3 of acute myocardial infarctions (AMIs) are unrecognized. To date, no studies of unrecognized AMIs have employed perfusion imaging, although it is more sensitive than the ECG and provides more information about infarct characteristics, such as size and location. In this study, 82 of 258 consecutive patients (31.8%) undergoing exercise testing with technetium-99m sestamibi perfusion imaging had fixed, nonartifactual perfusion defects, suggesting AMI. These patients were interviewed regarding their recognition of AMI; 27 patients (32.9%) had unrecognized AMI. Unrecognized AMI was significantly associated with (1) smaller infarcts, (2) infarcts not in the apical or septal regions, (3) diabetes mellitus, (4) lack of angina, (5) a negative family history for cardiac disease, and (6) being African-American. Many of these variables were significantly intercorrelated, and in multivariate analysis, unrecognized AMI remained significantly predicted by a smaller infarct and lack of angina. This study suggests that the incidence of unrecognized AMI detected via perfusion imaging on a clinic population is similar to that detected via electrocardiographic studies on community samples. This study also replicates prior findings of the medical history and demographic correlates of unrecognized AMI, and indicates that infarct size and location are also associated with unrecognized AMI.