Objective To examine the association between unrecognised myocardial infarction (MI) as detected by electrocardiography and the long-term risk of heart failure. Design The Rotterdam Study is a prospective population-based cohort study of the general population of a suburb of the city of Rotterdam, The Netherlands. Participants At baseline 2581 men and 3724 women aged $55 years were classified on the basis of electrocardiography, interview and clinical data into those with recognised MI, those

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... th ECG-based unrecognised MI and those without MI. The participants were followed-up for incident heart failure, death or end of the study period on 12 October 2006. Results During a median follow-up time of 13.2 years, 823 cases of heart failure occurred, of which 403 in men. Independently of cardiovascular risk factors, recognised and unrecognised MIs yielded HRs of developing heart failure in men of 2.6 (95% CI 2.0 to 3.3) and 2.1 (95% CI 1.5 to 2.9), respectively. In women, recognised MI was associated with heart failure (HR¼2.8; 95% CI 1.9 to 4.1), whereas unrecognised MI was not significantly related to the risk of heart failure (HR¼1.1; 95% CI 0.7 to 1.7). Conclusion Unrecognised MI detected by electrocardiography yields a long-term risk of heart failure equivalent to recognised MI in men, but is not significantly related to heart failure in women. In the light of the high incidence of both unrecognised MI and heart failure in the elderly, it may be worthwhile for both doctors and patients to improve responsiveness to typical and atypical symptoms of MI.