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.