Circadian variation of ventricular tachycardia in acute myocardial infarction

Circadian rhythms have been described both for acute myocardial infarction (AMI) and sudden death. In this study the diurnal distribution of ventricular tachycardia (VT) in patients with AMI was analyzed. Ninety-four AMI patients with greater than or equal to 1 VT on Holter electrocardiographic monitoring who were not taking antiarrhythmic drugs were studied. Forty-seven patients had a recent AMI (group A) and 47 an old AMI (group B). Chronobiologic analysis was made by single cosinor method. There were 157 VTs (mean 1.67 VTs/patient, range 1 to 10) in the 94 patients: 70 in group A and 87 in group B. A significant circadian rhythm of VT was found in the total population with acrophase at 2:29 P.M. The hourly distribution of VT showed a tendency to bimodality, which seemed due to a different time of peak VT occurrence in group A (significant rhythm with acrophase at 4:40 P.M.) and group B (significant rhythm with acrophase at 12:39 P.M.). Thus, the hourly VT frequency in patients with AMI has a significant circadian variation with the highest occurrence in the awake hours, similar to the rhythms described for AMI and sudden death.