Further information: Atrial Fibrillation and Flutter (see p1955) and Antiarrhythmic Drugs (see p2085) from Cardiovascular Medicine, 3rd Edn*

In order to compare two heart rate control strategies in patients with permanent atrial fibrillation, a randomized, multicenter, open-label, prospective, noninferiority trial was conducted at 33 centers in the Netherlands. Recruitment for the Rate Control Efficacy in Permanent Atrial Fibrillation: A Comparison Between Lenient versus Strict Rate Control II (RACE II) trial began in January of 2005 and ended in June of 2007 [1]. Eligible patients were 80 years of age or younger, had permanent atrial fibrillation for up to 12 months, had a mean resting heart rate above 80 beats per minute, and had a medical regimen that included the use of oral anticoagulation therapy. A total of 614 patients were recruited. The patients were randomized to undergo either a lenient rate-control strategy with a resting heart rate <110 beats per minute, or a strict rate-control strategy with a resting heart rate <80 beats per minute, to determine which strategy reduced the incidence of heart failure and stroke. Because prior studies had shown that strict rate control reduced symptoms, improved quality of life and exercise capacity, reduced heart failure, and improved survival, it has been the preferred strategy. However, strict control could also cause drug-related adverse effects, such as bradycardia, syncope, and the need for a pacemaker, and the study was conducted to test the hypothesis that lenient rate control is not inferior to strict rate control.

Primary outcome was a composite of death from cardiovascular causes, heart failure-induced hospitalization, stroke, systemic embolism, major bleeding, and arrhythmic events. Secondary outcomes included all of the primary outcomes plus death from any cause, symptoms, and functional status. The follow-up period was a maximum of 3 years, and at the end of that time, the estimated cumulative incidence of the primary outcome was 12.9% in the lenient rate-control group and 14.9% in the strict rate-control group. There was an absolute difference in the lenient rate-control of 2.0 percentage points (90% CI, -7.6 to 3.5; P<0.001 for the prespecified noninferiority margin). The frequencies of symptoms and adverse events were similar in the two groups, and the investigators concluded that lenient rate-control is as effective as strict rate-control, which should prove helpful to patients being treated for permanent atrial fibrillation.

[1] Van Gelder IC, Groenveld HF, Crijins HJGM, et al. Lenient versus strict rate control in patients with atrial fibrillation (RACE II). N Engl J Med 2010;362:1439-41

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