Increased Monday incidence of life-threatening ventricular arrhythmias. Experience with a third-generation implantable defibrillator.

BACKGROUND: Examination of the timing of cardiac events provides important pathophysiological information. Previous studies have shown that the onset of acute myocardial infarction occurs most frequently on Monday. The septadian (day of the week) pattern of occurrence of sudden cardiac death and lethal ventricular arrhythmias has not been examined previously. METHODS AND
RESULTS: We examined the septadian distribution of life-threatening (cycle length < 280 ms) ventricular arrhythmias in 683 consecutive patients receiving a Ventak PRx, a third-generation implantable defibrillator with an event recorder. There was a prominent Monday peak, with a midweek decline and a secondary peak later in the week. A marked trough is apparent on both weekend days. The observed pattern was independent of age, sex, ejection fraction, NYHA functional class, type of heart disease, and the use of antiarrhythmic drugs but was not observed in patients receiving beta-blockers.
CONCLUSIONS: Potentially lethal arrhythmias are not random events but occur in a daily pattern suggesting a relationship to the beginning and end of the work week. The absence of a Monday peak in patients receiving beta-blockers suggests that the pattern may be influenced by beta-blockers. This information may be useful in devising strategies to prevent sudden cardiac death.