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 m yocardial infarction and sudden cardiac death. Method. A large populat ion based coronary heart disease register, the ARCOS Study, which is c ollaborating in the WHO MONICA Project carried out in Auckland, New Ze aland, 1983-90. There were 4983 patients aged 25-64 with definite myoc ardial infarction or coronary death, Main outcome measures - circadian and weekly variation in onset of symptoms of definite myocardial infa rction 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 circadi an pattern was analysed by various risk factors and medications. A wee kly variation was found with an increased incidence of onset of sympto ms during the weekend and on Monday for surviving patients and a Satur day high (18.6%) for sudden death patients. Conclusions. Further inves tigation of physiological changes within subgroups during the key peri ods may provide insight into triggering mechanisms and lead to better means for prevention.