Aims: Uncontrolled ventricular rate (VR) during atrial fibrillation (AF) may cause clinical deterioration in heart failure (HF) patients who need continuous biventricular pacing to achieve cardiac resynchronization therapy (CRT). We aimed at evaluating the association between AF, uncontrolled VR, and sub-optimal CRT, defined as low biventricular pacing percentage (BIVP%).
Methods and results: All 1404 patients had HF, New York Heart Association (NYHA) ≥II, left ventricular ejection fraction (LVEF) ≤35%, and QRS ≥120 ms, and received an implantable CRT defibrillator (CRT-D). Occurrence of AF, VR during AF and lifetime BIVP% were estimated from device data. Ventricular rate during AF was defined as uncontrolled in patients with mean VR>80 bpm and maximum VR>110 bpm. Over a median follow-up of 18 months, AF was detected in 443 of 1404 patients (32%). In this sub-group of AF patients, VR during AF was uncontrolled in 150 of 443 patients (34%). Multivariate Cox regression analysis showed that age [hazard ratio (HR) = 1.03, 95% confidence interval (CI) = 1.00-1.06, P= 0.028], and uncontrolled VR [HR = 1.69 (CI = 1.01-2.83), P= 0.046] were the only independent predictors of clinical outcome, assessed by HF hospitalizations and death. The median lifetime BIVP% was 95% (25-75 percentile range 91-99%). Biventricular pacing percentage was significantly and inversely correlated to VR, decreasing by 7% for each 10 bpm increase in VR. Sub-optimal CRT, defined as BIVP% <95%, was predicted by the occurrence of persistent or permanent AF [odds ratio (OR) = 3.77, CI = 2.44-5.82, P< 0.001], and uncontrolled VR [OR = 2.25, CI = 1.35-3.73, P= 0.002].
Conclusion: Uncontrolled VR occurs in one-third of CRT-D patients, who experience AF, and is associated with HF hospitalizations and death and with sub-optimal CRT (lifetime BIVP%<95%).