Echocardiographic Characteristics of Electrocardiographically Unrecognized Myocardial Infarctions in a Community Population

Unrecognized myocardial infarction (UMI) as diagnosed by surveillance electrocardiography has been shown to carry the same poor prognosis as recognized myocardial infarction (RMI). The echocardiographic characteristics of UMI have never been studied before. Due to a similar prognosis, we hypothesized that UMI and RMI would exhibit similar degrees of echocardiographic ventricular dysfunction. We studied a random community cohort of 2,042 adults who were ≥45 years of age in a cross-sectional setting in Olmsted County, Minnesota. RMI was diagnosed by review of medical records and UMI was diagnosed if the electrocardiogram met MI criteria without a previous MI recorded in the medical record. All subjects underwent transthoracic echocardiography. We identified 80 patients who had UMI and 101 who had RMI. In bivariate analyses, a stepwise increase in echocardiographic abnormalities was observed from participants who had no MI to UMI to RMI: respective mean ejection fractions were 63%, 61%, and 55; prevalences in left ventricular enlargement were 13%, 22%, and 52%; mean left ventricular mass indexes were 98, 103, and 118 g/m2; prevalences in regional wall motion abnormality were 2%, 13%, and 42%; and prevalences in diastolic dysfunction were 25%, 56%, and 65% (p for trend <0.0001 for all comparisons). After adjusting for standard coronary risk factors, patients who had UMI continued to exhibit significant abnormalities in systolic dysfunction, diastolic dysfunction, and regional wall motion abnormality, although to a lesser extent than patients who had RMI. In conclusion, patients who have UMI manifest structural abnormalities more commonly than do patients who have no MI but less commonly than do those who have RMI. The similar prognosis after UMI and RMI cannot be explained by comparable degrees of ventricular damage.