Optimal heart rate in patients with atrial fibrillation: insights from the COOL-AF registry

Heart rate control is an important strategy for the management of patients with atrial fibrillation (AF). However, there remains some uncertainty for the optimal target heart rate of AF patients. COOL-AF was a prospective multicenter registry of patients with non-valvular AF. Patients were followed-up every 6 months until 3 years. The primary outcome was the composite of cardiovascular death, heart failure, and ischemic stroke/systemic embolism (SSE). A total of 3405 patients were studied (mean age 67.8 ± 11.3 years; 41.8% female). Mean heart rate was 77.4 ± 16.2 bpm. Number of patients with baseline heart rate < 60, 60-80, 80-100, and ≥ 100 bpm was 371 (10.9%), 1616 (47.4%), 1116 (32.8%), and 302 (8.9%), respectively. The overall incidence rates of the composite outcome, heart failure event, CV death, and SSE were 4.97 (4.51-5.47), 2.84 (2.49-3.21), 1.34 (1.11-1.60), and 1.51 (1.26-1.78) per 100 person-years, respectively. When compared to those with heart rate in the range 60-80 bpm, AF patient with heart rate > 100 bpm had the highest incidence rate of the composite outcome (7.06 per 100 person-years) with the unadjusted and adjusted hazard ratios (95%CI) of 1.59 (1.17, 2.16) (p = 0.003) and 1.51 (1.11-2.07) (p = 0.009), respectively. The analysis of dynamic changes in heart rate demonstrated more prominent results with the unadjusted and adjusted hazard ratios (95%CI) of 1.84 (1.40, 2.40) (p < 0.001) and 1.76 (1.34-2.37) (p < 0.001), respectively. In conclusion, there is a J-curve pattern for the relation of baseline resting heart rate and the composite outcome in patients with AF. Patients with heart rate greater than 100 are the highest risk group.