Circadian chaos of ventricular tachyarrhythmia: a novel digital phenotype predicts mortality in high-risk SCD patients

Background While ventricular tachyarrhythmias (VTAs) exhibited circadian variation at the population level, the prognostic significance of individual VTA onset circadian patterns recorded via home monitoring in patients with high-risk SCD remains poorly defined. Methods This secondary analysis of the SUMMIT registry retrospectively evaluated archived remote monitoring data. Patients were categorized into four groups based on the diurnal distribution of their VTA episodes: no VTA, daytime VTA (> 70% of episodes between 06: 00-21: 59), nocturnal VTA (> 70% between 22: 00-05: 59), and mixed VTA (no predominant pattern). Results Among 756 included patients (mean follow-up 48.8 months), 443 (58.6%) experienced at least one VTA. Dominant daytime VTA onset occurred in 292 patients (65.9%), dominant nocturnal onset in 57 (12.9%), and mixed diurnal pattern in 94 (21.2%). The mixed VTA group had the highest mortality risks across four VTA groups, which demonstrated 4.4- and 2.5-fold higher risks of cardiac death (hazard ratio (HR): 4.42; 95% CI: 2.52–7.76; P < 0.001) and all-cause mortality (HR: 2.51; 95% CI: 1.69–3.73; P < 0.001) when compared to the no-VTA group, respectively. This association persisted even after excluding patients with electrical storms, with the mixed VTA group remaining an independent predictor of both cardiac death (adjusted HR: 2.61; P = 0.017) and all-cause mortality (adjusted HR: 2.27; P = 0.002). Conclusions A mixed VTA circadian pattern, characterized by the absence of a dominant diurnal rhythm, is a strong, independent predictor of increased mortality in high-risk SCD patients, highlighting its value for risk stratification.