Rate control efficacy in permanent atrial fibrillation: successful and failed strict rate control against a background of lenient rate control: data from RACE II (Rate Control Efficacy in Permanent Atrial Fibrillation).

Objectives: This study sought to investigate differences in outcome between patients treated with successful strict, failed strict, and lenient rate control.

Background: The RACE II (Rate Control Efficacy in Permanent Atrial Fibrillation) study showed no difference in outcome between lenient and strict rate control in patients with permanent atrial fibrillation (AF). However, in the strict group not all patients achieved the pre-defined heart rate target.

Methods: The primary outcome was a composite of cardiovascular morbidity and mortality. For the current analysis outcome events were analyzed from end of the dose-adjustment phase until end of follow-up (median 2.9 years [interquartile range: 2.4 to 3.0 years]). Of 614 patients, 608 completed the dose-adjustment phase-301 in the strict (resting heart rate <80 beats/min, and during moderate exercise <110 beats/min) and 307 in the lenient group (resting heart rate <110 beats/min). In the strict group, 203 of 301 patients achieved the rate control target, and 98 failed.

Results: Heart rate was different after the dose-adjustment phase between the successful strict (72 ± 7 beats/min), failed strict (86 ± 14 beats/min), and lenient (93 ± 8 beats/min) group (p < 0.001) and remained significantly different during follow-up. The primary outcome was reached in 27 of 203 (14.2% KM estimate) in the successful strict versus 14 of 98 (15%) in the failed strict versus 35 of 307 (12.1%) in the lenient group (p = 0.5). The components of the primary outcome and quality of life were similar in the groups.

Conclusions: In patients with permanent AF, successful strict rate control does not improve outcome. Therefore, lenient rate control might be frontline therapy.