Background: The past literature has long ago identified painless myocardial infarction as a clinical entity; however, the term has been applied, often loosely, to denote diagnosis of infarction made at autopsy, or during routine electrocardiography, or at presentation with atypical symptoms. Many of the old studies were retrospective or included patients who could not contribute a reliable history.
Methods: Systematic interviews of 517 consecutive patients with an acute myocardial infarction admitted to the Coronary Care Unit were carried out; a large array of data was collected prospectively while the patients were taken care of in the hospital.
Results: A reliable history of symptoms at the inception of the clinical episode could be provided by 501 patients; 40 patients (8.0%) presented with painless (not silent) infarction, while the remaining 461 had pain. Multivariate analysis revealed that painless presentation of myocardial infarction correlated positively with age (OR 1.05, CI 1.02-1.08) and admission Killip class (OR 2.58, CI 2.16-2.97), and negatively with history of prior angina (OR 0.16, CI 0.15-064); also it was not a predictor of increased rate of mortality or life-threatening arrhythmias.
Conclusions: Presentation with painless myocardial infarction occurs in older patients with increased degrees of pulmonary congestion on admission, and less frequent rate of prior angina than the ones encountered in patients with pain; however such presentation is not an independent predictor of worse than expected in-hospital outcome.