[Differential circadian rhythms in myocardial infarction according to its extent by electrocardiogram].

BACKGROUND AND OBJECTIVE

To determine the existence of circadian rhythm in the time of onset of acute myocardial infarction (AMI) according to their extension type (Q-wave vs. non-Q-wave).

PATIENTS AND METHOD

We studied a retrospective cohort of patients from a multicentre study of myocardial infarction (ARIAM study group). We collected information about 54,249 infarctions from the data base of the ARIAM (Analysis of Delay in AMI) Spanish multicentre study. The following variables were analysed: general variables --age, gender, previous ischemic heart disease, outcome at coronary care unit, infarction electrocardiograph type (Q wave or non-Q wave) and location of AMI--, cardiovascular risk factors, and previous drug treatment of the patients. To verify the presence of circadian rhythm we developed a simple test of equality of time series based on the multiple-sinusoid cosinor analysis. Three sinusoids (24-12-8 h periods) were used.

RESULTS

The time of pain onset shows circadian rhythm (p < 0.0000), which also is observed in both infarction electrocardiograph characteristics subgroups (Q-wave infarction and non-Q-wave infarction) (p < 0.0000). Q-wave infarction shows sinusoid curve with one maximum morning peak and non-Q-wave shows bimodal curve, with two peaks. Comparison between their curves shows statistical significance (p < 0.0000).

CONCLUSIONS

AMI onset follows a circadian rhythm pattern, which is also observed in analysed subgroups. Differences in the circadian rhythm according to the Q/non-Q wave infarction characteristics, could be determined by different physiopathologic mechanism. The cosinor model fit with three components (24, 12 and 8-hour-periods) show good sensitivity to determine circadian rhythm.