Power-law properties of nocturnal arrhythmia avalanches: a novel marker for incident cardiovascular events

BACKGROUND: Bursting non-sustained cardiac arrhythmia events, are a common observation during sleep. OBJECTIVES: We hypothesized nocturnal arrhythmia episode durations could follow a power-law, whose exponent could predict long-term clinical outcomes. METHODS: We defined 'nocturnal arrhythmia avalanche' (NAA) as any instance of a drop in electrocardiogram (ECG) template-matched R-R intervals =30% of R-R baseline, followed by a return to 90% of the baseline. We studied NAA in ECG recordings obtained from the Sleep Heart Health Study (SHHS), the Osteoporotic Fractures in Men Study (MrOS) Sleep and Multi-Ethnic Study of Atherosclerosis (MESA) studies. The association of the nocturnal arrhythmia durations with a power-law distribution was evaluated, and the association of derived power-law exponents (a) with major adverse cardiovascular events and mortality assessed with multivariable Cox regression. RESULTS: n=9176 participants were studied. NAA episodes distribution was with a consistent power-law versus comparator distributions in all datasets studied (Positive log likelihood ratio of power-law vs. exponential in MESA: 83%; SHHS: 69%; MrOS: 81%; power-law vs. log-normal in MESA: 95%; SHHS: 35% and MrOS: 64%). The NAA power law exponent (a) showed a significant association of with adverse CV outcomes (Association with CV mortality: SHHS (HR = 1.39[1.07-1.79], p=0.012); MrOS (HR = 1.42[1.02-1.94], p=0.039; Association with CV events: MESA (HR = 3.46[1.46-8.21], p=0.005)) in multivariable Cox regression, after adjusting for conventional CV risk factors and nocturnal ectopic rate. CONCLUSION: The NAA power-law exponent is a reproducible, predictive marker for incident cardiovascular events and mortality.