Association between activity at onset of symptoms and outcome of acute myocardial infarction.

Objectives: This study sought to compare the clinical features and outcome of a first myocardial infarction with onset of symptoms during or within 30 min of exercise, at rest and in bed.

Background: It is not known whether activity at onset influences outcome of acute myocardial infarction.

Methods: Information collected using a standard questionnaire was used to relate activity at the onset of symptoms to in-hospital outcome in 2,468 consecutive patients admitted to a coronary care unit with a first myocardial infarction between 1975 and 1993.

Results: Patients with exercise-related onset were more likely to be younger and male. Those with onset in bed were more likely to be older and have a history of stable or unstable angina. Compared with patients whose symptoms began at rest, those with exercise-related onset had a lower in-hospital mortality rate after adjusting for age, gender and year of admission (odds ratio [OR] 0.60, 95% confidence interval [CI] 0.40 to 0.89), and patients with onset in bed had a higher mortality rate (OR 1.38, 95% CI 1.03 to 1.85). The incidence of cardiac failure requiring diuretic therapy was also lower for exercise-related onset (OR 0.83, 95% CI 0.67 to 1.04) and higher when onset was in bed (OR 1.36, 95% CI 1.11 to 1.66).

Conclusions: There is an association between activity at onset and outcome of acute myocardial infarction. Differences in pathophysiology or in the population at risk could explain this observation.