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

BACKGROUND: Incidence 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 RESULTS: Prospective, 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 (1-8days), 2 (9-20days), 3 (21-60days) and quartile 4 (>60days). During median follow-up of 35months 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.

CONCLUSIONS: Daily 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 3years. Cumulative low CRT% burden (in days) independently predicts mortality before mean CRT% drop.