Background: Conventional Deceleration Capacity (DC) method is an established total mortality predictor in post-myocardial infarction patients. We introduced a new DC variant based on a Beat to Beat DC (BBDC) calculation algorithm.
Purpose: The circadian properties of the BBDC were investigated and assessed for possible risk stratification application.
Methods: Twenty four hour Holter ECG signals from 220 Heart failure patients (age=65±13 years, male=84%, LVEF=32±10%) were analysed for: Entire 24 hours (08.00–08.00), Day (06.00–23.00), Night (23.00–06.00). BBDC were calculated for each period. The difference between night (BBDCnight) and day (BBDCday) accepted as the Circadian BBDC (Circ. BBDC). After 41 months, 57 patients had Sudden Cardiac Death (SCD) end-points.
Results: From univariate analysis for SCD+ and SCD- groups: BBDC24h: 6.4±1.7ms vs 7.0±2.0ms, (p=0.03). BBDCday:6.2±1.7ms vs 6.7±1.9ms, (p=0.1). BBDCnight:6.6±1.9 ms vs 7.5±2.3 ms (p=0.03). Circ. BBDC: 0.3±1.4ms vs 0.7±1.2ms, (p=0.03). After Cox regression analysis adjusted for Circ.BBDC, Gender, QRS duration, QTc interval (Fridericia), Circ.BBDC was an independent SCD predictor (HR: 0.768, 95% CI: 0.601–0.981, p=0.03). Circ BBDC values distribution across the percentiles were: 1st: -2ms, 25th: -0.2ms, 50th: 0.6ms, 75th: 1.4ms, 90th: 2.5 ms, 99th: 4.2 ms. The cut off point of -0.2 ms (25th percentile) in the same Cox regression model presented HR: 1.843 for SCD (95% CI: 1.031–3.293, p=0.03).
Conclusions: BBDC Circardian properties are impaired in patients prone to SCD. Patients with absence of circadian adaptation and Circ BBDC values less than -0.2 ms, present Hazard Ratio 1.843 for SCD. Further clinical investigation is needed.