Key result
Symptom onset of acute myocardial infarction between 6:00 AM and noon significantly predicted greater infarct size, while onset between midnight and 6:00 AM had lower risk of circulatory arrest.
Why the study?
Does the circadian rhythm of acute myocardial infarction onset impact infarct size, risk of ventricular tachyarrhythmias, and in-hospital mortality?
Observational (n=10,791)
No
Does the circadian rhythm of acute myocardial infarction onset impact infarct size, risk of ventricular tachyarrhythmias, and in-hospital mortality?
The time of day of AMI symptom onset impacts not only the incidence but also the severity of the infarction, with morning onset predicting greater infarct size.
Morning-onset AMI may signal larger infarcts; hypothesis-generating for circadian effects and should not yet change practice or trial stratification.
In order to study whether the circadian rhythm of acute myocardial infarction (AMI) onset has any impact on the clinical outcome, in terms of enzymatically estimated infarct size, circulatory arrest from ventricular tachyarrhythmias, and in-hospital mortality, the authors studied a representative population of 10,791 AMIs treated in the same center between 1973 and 1987. In 6,763 cases (63%) the time of symptom onset was known. In these cases a major peak in AMI incidence was observed between 7:01 AM and 10:00 AM, and minor peaks at 12:01 noon, 3:01 PM-4:00 PM, and 8:01 PM-9:00 PM. In a set of multivariate analyses including several clinical characteristics, symptom onset between 6:00 AM and 12:00 noon significantly predicted a greater infarct size, and symptom onset between 12:00 AM and 6:00 AM was associated with a significantly lower risk of circulatory arrests from ventricular tachyarrhythmias. The time of symptom onset was not significantly associated with in-hospital mortality after adjustment for other clinical characteristics, including infarct size. The authors suggest that the time of day has an impact, not only on the incidence, but also on the severity of AMI and that the ability of beta blockers to blunt the morning increase in AMI incidence may possibly contribute to the beneficial secondary preventive effects of such drugs after AMI.
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Hansen et al. (1993) conducted an observational in Acute myocardial infarction (n=10,791). Time of symptom onset vs. Other times of day was evaluated on Enzymatically estimated infarct size, circulatory arrest from ventricular tachyarrhythmias, and in-hospital mortality. Symptom onset of acute myocardial infarction between 6:00 AM and noon significantly predicted greater infarct size, while onset between midnight and 6:00 AM had lower risk of circulatory arrest.
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