Do we need to monitor the percentage of biventricular pacing day by day?

BackgroundIncidence and clinical significance of transient, daily fluctuations of biventricular pacing percentage (CRT%) remain unknown. We assessed the value of daily remote monitoring in identifying prognostically critical burden of low CRT%.Methods and resultsProspective, single-centre registry encompassed 304 consecutive heart failure patients with cardiac resynchronization therapy defibrillators (CRT-D). Patients with 24-h episodes of CRT% loss < 95% were assigned to quartiles depending on cumulative time spent in low CRT%: quartile 1 (1-8 days), 2 (9-20 days), 3 (21-60 days) and quartile 4 (> 60 days). During median follow-up of 35 months 51,826 transmissions were analysed, including 15,029 in 208 (68.4%) patients with episodes of low CRT%. Overall, mean CRT% ≥ 95% vs. < 95% resulted in a 4-fold lower mortality (17.3 vs. 68.2%; p < 0.001). Fifty-four percent of patients experienced episodes of CRT% loss, despite 85.6% having mean CRT% ≥ 95%. Mortality was lowest in quartile 1 (7.7%), while longer periods of CRT% loss resulted in significantly higher death rates (25.0 vs. 34.6 vs. 57.7%; quartiles 2-4 respectively, p < 0.001), despite mean CRT% still being ≥ 95% in quartiles 1-3. Cumulative low CRT% burden was the independent risk factor for death (HR 1.013; 95% CI 1.006-1.021; p < 0.001). Mortality rose by 1.3 and 49% with every additional day and quartile of CRT% loss, respectively.ConclusionsDaily remote monitoring allows one to detect 24-h episodes of CRT% loss < 95% in over two-thirds of CRT-D recipients during median observation of 3 years. Cumulative low CRT% burden (in days) independently predicts mortality before mean CRT% drop.