Variation in the time and day of onset of myocardial infarction and sudden death.

AIM

To examine circadian and weekly variation in the onset of acute myocardial infarction and sudden cardiac death.

METHOD

A large population based coronary heart disease register, the ARCOS Study, which is collaborating in the WHO MONICA Project carried out in Auckland, New Zealand, 1983-90. There were 4983 patients aged 25-64 with definite myocardial infarction or coronary death. Main outcome measures--circadian and weekly variation in onset of symptoms of definite myocardial infarction and sudden cardiac death.

RESULTS

Surviving patients showed a circadian pattern with a single morning peak in symptom onset (30.0%) while sudden death patients exhibited an afternoon peak (32.5%) and a secondary morning peak (27.6%). Within these two subgroups the circadian pattern was analysed by various risk factors and medications. A weekly variation was found with an increased incidence of onset of symptoms during the weekend and on Monday for surviving patients and a Saturday high (18.6%) for sudden death patients.

CONCLUSIONS

Further investigation of physiological changes within subgroups during the key periods may provide insight into triggering mechanisms and lead to better means for prevention.