Abrupt shifts in behavioral routine and sleep-wake timing decoupled sinoatrial and atrioventricular node rhythms, revealing distinct circadian mechanisms governing cardiac conduction.
Observational (n=39)
Randomized for shift-work simulation
Yes
Circadian clocks in the brain and heart differentially regulate SA and AV node activity, creating a vulnerability to arrhythmias during abrupt shifts in sleep-wake cycles.
Electrical activity in the heart exhibits 24-hour rhythmicity, and potentially fatal arrhythmias are more likely to occur at specific times of day. Here, we demonstrate that circadian clocks within the brain and heart set daily rhythms in sinoatrial (SA) and atrioventricular (AV) node activity, and impose a time-of-day dependent susceptibility to ventricular arrhythmia. Critically, the balance of circadian inputs from the autonomic nervous system and cardiomyocyte clock to the SA and AV nodes differ, and this renders the cardiac conduction system sensitive to decoupling during abrupt shifts in behavioural routine and sleep-wake timing. Our findings reveal a functional segregation of circadian control across the heart's conduction system and inherent susceptibility to arrhythmia.
Hayter et al. (Fri,) conducted a observational in Healthy volunteers (n=39). Total sleep deprivation and simulated shift work vs. Baseline / Day shift routine was evaluated on Changes in ECG characteristics (RR, QT, PR segment intervals). Abrupt shifts in behavioral routine and sleep-wake timing decoupled sinoatrial and atrioventricular node rhythms, revealing distinct circadian mechanisms governing cardiac conduction.