Circadian periodicity affects the type of ventricular arrhythmias and efficacy of implantable defibrillator therapies.

ABSTRACT

INTRODUCTION: Factors influencing malignant arrhythmia onset are not fully understood. We explored the circadian periodicity of ventricular arrhythmias (VAs) in patients with implantable cardioverter and cardiac resynchronization defibrillators (ICD/CRT-D). METHODS: Time, morphology (monomorphic/polymorphic), and mode of termination (anti-tachycardia pacing [ATP] or shock) of VAs stored in a database of remote monitoring data were adjudicated. Episodes were grouped in six 4-h timeslots from 0000 to 2400. Circadian distributions and adjusted marginal odds ratios (ORs), with 95% confidence interval (CI), were analyzed using mixed-effect models and logit generalized estimating equations, respectively, to account for within-subject correlation of multiple episodes. RESULTS: Among 1303 VA episodes from 446 patients (63% ICD and 37% CRT-D), 120 (9%) self-extinguished, and 842 (65%) were terminated by ATP, 343 (26%) by shock. VAs clustered from 0800 to 1600 with 44% of episodes, as compared with 22% from 0000 to 0800 (p < .001) and 34% from 1600 to 2400 (p = .005). Episodes were more likely to be polymorphic at night with an adjusted marginal OR of 1.66 (CI, 1.15-2.40; p = .007) at 0000-0400 versus other timeslots. Episodes were less likely to be terminated by ATP in the 0000-0400 (success-to-failure ratio, 0.67; CI, 0.46-0.98; p = .039) and 0800-1200 (0.70; CI, 0.51-0.96; p = .02) timeslots, and most likely to be terminated by ATP between 1200 and 1600 (success-to-failure ratio 1.42; CI, 1.06-1.91; p = .02). CONCLUSION: VAs did not distribute uniformly over the 24 h, with a majority of episodes occurring from 0800 to 1600. Nocturnal episodes were more likely to be polymorphic. The efficacy of ATP depended on the time of delivery.