Circadian Variations in the Occurrence of Ventricular Tachyarrhythmias in Patients with Implantable Cardioverter Defibrillators

Abstract

A circadian distribution has been demonstrated in episodes of sudden cardiac death, acute myocardial infarction, ventricular premature complexes, heart rate variability, and ventricular tachyarrhythmias. The aim of this study was to evaluate the circadian distribution of ventricular tachyarrhythmia episodes in a population of ICD patients. Data were gathered from 72 patients (55 men, 17 women; mean age 62.7 +/- 12.2 years, mean LVEF 0.0037 +/- 0.0011) with ICDs implanted for standard indications. Patients were followed every 3 months over a mean period of 21 +/- 12.8 months. At each examination, symptoms at arrhythmia onset and perception of ICD therapy were recorded, and the ICD memory was interrogated. During follow-up, 1,023 episodes' of malignant ventricular arrhythmias were detected and effectively terminated, 506 of which were fully analyzed. A morning peak in ventricular tachyarrhythmias was demonstrated between 7:00 and 11:00 AM, and an afternoon peak between 6:00 and 7:00 PM. A significantly lower occurrence of VT was observed at 1:00 AM and between 4:00 and 6:00 AM. A circadian distribution in the occurrence of ventricular tachycardias was found. The three striking features of the data are: the early morning peak (about three hours after waking up), relatively stable incidence throughout waking hours, and decline in incidence in the previous period.

Temporal Differences in Out-of-Hospital Cardiac Arrest Incidence and Survival

“…Fourth, as discussed previously, the use of 9-1-1 call time as a surrogate for actual time of cardiac arrest can be inaccurate and thus has the potential for misclassification bias, for example, by falsely classifying patients who died at night to have arrested (and died) in the morning. Although assessment of the time of arrest from implantable cardiac defibrillator electrograms may be more accurate, 32 these have limited generalizability because of selection bias in the type of patients who tend to have these devices implanted. Fifth, we were unable to relate timing of cardiac arrest to patient behaviors such as wake time, physical activities, or medication compliance or to the type of cardiac arrest (eg, myocardial infarction or primarily arrhythmic).…”

Driving and Implantable Cardioverter-Defibrillator Shocks for Ventricular Arrhythmias

“…To investigate the sensitivity of our result to repeated shocks in the same patient, we repeated the analysis only including the first shock experienced by each patient. Finally, because patients are unlikely to drive during the nighttime hours between 12 AM to 6 AM when the risk of an ICD shock is lowest (19,20), we performed a sensitivity analysis that excluded this nighttime period from the case-crossover analysis. In this analysis, we conservatively assume that none of the patients were exposed to driving during this time period.…”

Circadian variation in the occurrences of ventricular tachyarrhythmias: Differences between coronary artery disease and dilated cardiomyopathy

“…The analysis of ischemic patients with Implantable Cardioverter Defibrillators (ICDs) evidence a morning peak and a secondary afternoon peak [1,2]. Similar circadian pattern has been noted in acute myocardial infarction [3] and stroke [4].…”