Physical exertion as a trigger of acute myocardial infarction. Triggers and Mechanisms of Myocardial Infarction Study Group.
Level 4 - case-series / case-control
Case-control and case-crossover observational study
PubMed 8232457 · doi:10.1056/NEJM199312023292302
What was done
Consecutive patients with acute myocardial infarction were identified from hospital admissions in Berlin and a monitored population of 330,000 residents in Augsburg, Germany, between 1989 and 1991. Standardized interviews were conducted (mean 13 ± 6 days post-infarction) to assess circumstances before onset. The investigators performed both a matched case-control analysis and a self-matched case-crossover analysis assessing strenuous physical exertion (≥6 metabolic equivalents) within one hour prior to infarction onset.
What was found
Among 1,194 patients (74% men, mean age 61 ± 9 years), 7.1% had engaged in strenuous exertion at symptom onset compared with 3.9% of matched controls, yielding an adjusted relative risk of 2.1 (95% CI, 1.1 to 3.6). The case-crossover analysis also showed a relative risk of 2.1 (95% CI, 1.6 to 3.1) for exertion within one hour prior to infarction. Stratification by baseline exercise frequency revealed that the relative risk was 6.9 for patients exercising fewer than four times per week versus 1.3 for those exercising four or more times per week (P < 0.01).
Why it matters
This study provides quantitative evidence that heavy physical exertion can transiently trigger myocardial infarction, while indicating that habitual physical activity largely blunts this acute trigger effect.
Limits
Data collection relied entirely on self-reported recall obtained nearly two weeks after the cardiac event, introducing potential recall bias. The abstract does not provide absolute risk calculations, and findings are limited to surviving patients able to complete an interview.
Cited by
- supports The transient risk of a cardiac event during a burst of acute exercise increases up to 100-fold above baseline in unfit individuals, but only 10% to 20% in very fit individuals.