Characteristics and periodicity of sustained ventricular tachyarrhythmia events in a population of military veterans with implantable cardioverter defibrillator

Purpose: Circadian patterns of ventricular tachyarrhythmias (VTAs) in ICD patients from SCD-HeFT and MADIT-CRT have yielded differing results. The aim was to investigate VTA patterns in a large population of military veterans with ICD. Methods: This retrospective study analyzed biorhythm periodicity of sustained VTAs (≤ 300 ms). Findings were derived from the Veterans Affairs (VA) National Cardiac Device Surveillance database encompassing January 1, 2005, to December 31, 2017. Results: The patient population comprised 1559 consecutive patients with 17,039 VTAs. There were 763 patients with clinical information with the mean age of 67.8 ± 9 years old and 99% male. An hourly non-uniform VTA distribution with a bimodal pattern and a predominant afternoon peak was seen (χ² = 5057, P < 0.0001). VTAs treated successfully by anti-tachycardia pacing (ATP) showed a bimodal pattern with even distributions. VTAs treated by ICD shocks showed a bimodal pattern with a predominant afternoon peak. The duration of VTA peaks was increased from 13.5 to 17 h with increasing daylight time from 9.9 to 14.5 h. The weekly VTA distribution showed a significant septadian pattern with lowest frequency on weekend and highest on weekdays (χ² = 4840, P < 0.0001). No annual periodicity and monthly periodicity were seen. Conclusions: Sustained VTA events exhibited a circadian rhythm in a large population of military veterans with ICD/CRT-D; specifically, a bimodal pattern with a predominant afternoon peak was observed. Further, the majority of VTA episodes treated by ICD shock occurred in the afternoon, and the duration of VTA peak lengthened with increased duration of daylight time.