Impaired functional status and echocardiographic abnormalities signifying global dysfunction enhance the prognostic significance of previously unrecognized myocardial infarction detected by electrocardiography
Background: The relationship between electrocardiographic unrecognized myocardial infarction (UMI), abnormal functional status, echocardiographic abnormalities, and mortality has not been evaluated. Methods: A population-based random sample of 2042 Olmsted County residents, age ≥45 years, was studied by self-administered questionnaire, chart review, ECG and echocardiogram, and 5 year follow-up for all-cause mortality. UMI (n = 81) was diagnosed if ECG-MI criteria were met without previous documented myocardial infarction. Functional Status was assessed by the Goldman Specific Activity Scale. Results: UMI subjects had an increased prevalence of abnormal functional status compared to no MI controls (22% vs 11%, P < 0.05). This association was independent of sex, obesity, smoking, diabetes, and pulmonary disease. It became insignificant after stratifying for echocardiographic abnormalities. Compared to no MI controls, UMI subjects with impaired functional status had a higher mortality hazard ratio (HR 7.2; P<0.0001) than those without impaired functional status (HR 2.7; P = 0.02). In UMI subjects with impaired functional status and any echocardiographic abnormality signifying global ventricular dysfunction (systolic or diastolic dysfunction, left atrial or left ventricular enlargement), the mortality risk was even higher (HR 9.5; P<0.001) and persisted in multivariate analyses. This increased mortality risk was unaffected by adjustment for regional wall motion abnormalities. Conclusions: The assessment of impaired functional status and echocardiographic abnormalities improves the prognostic significance of UMI. Even in the absence of regional wall motion abnormalities, structural abnormalities of global dysfunction may play a role in mediating the increased mortality associated with UMI.