ATLANTA — A lenient heart rate target of less than 110 bpm at rest in patients with permanent atrial fibrillation is as effective in preventing cardiovascular morbidity and mortality as is the tight rate control strategy recommended in current guidelines, and requires less medication, according to a new study.
“Our study suggests that lenient rate control may be adopted as the first-choice rate control strategy … both for high- and low-risk patients. … If a patient comes into the office with permanent atrial fibrillation, a target resting heart rate just under 110 bpm on a 12-lead ECG is good enough,” Dr. Isabelle C. Van Gelder said in presenting the findings of the Rate Control Efficacy in Permanent Atrial Fibrillation: a Comparison Between Lenient Versus Strict Rate Control II (RACE II) trial at the annual scientific session of the American College of Cardiology.
Most physicians have adopted a strategy of rate control over rhythm control as initial therapy for patients with atrial fibrillation. The widely employed ACC/American Heart Association/European Society of Cardiology guidelines advise strict rate control with a resting heart rate below 80 bpm and a heart rate less than 110 bpm during moderate exercise.
The strict rate control strategy—which is not evidence based—assumes that a lower heart rate target will result in fewer symptoms and cardiovascular events. RACE II shows that assumption is incorrect, said Dr. Van Gelder of the University of Groningen (the Netherlands).
RACE II randomized 614 patients with permanent atrial fibrillation at 33 Dutch medical centers to strict or lenient rate control via beta-blockers, calcium channel blockers, and/or digoxin. At 3 years of follow-up, the primary end point—a composite of cardiovascular death, heart failure hospitalization, stroke, systemic embolism, life-threatening arrhythmia, and bleeding—occurred in 13% of the lenient rate control group and in 15% of the strict rate control group. The lenient rate control approach was statistically noninferior, and was as effective in patients at high baseline cardiovascular risk as in those at lower risk.
Of the patients in the lenient control group, 98% met their heart rate target, as did 67% in the strict control group. The lenient control group collectively had 75 outpatient visits related to atrial fibrillation; the strict control group had 684. A total of 207 (68%) of the 303 patients in the strict rate control group were treated with two or three rate control drugs, compared with 93 (30%) of the 311 patients in the lenient control arm. The dosages required in the strict control arm were about one-third higher.
At the end of follow-up, 46% of patients in each arm had atrial fibrillation symptoms: 70% were in NYHA functional class I, and 23% were in class II.
Dr. Van Gelder said that despite concern that the lenient rate control group would have a higher incidence of heart failure due to tachycardia-mediated cardiomyopathy, heart failure rates in the two study arms were similar.
“The explanation is that a resting heart rate just below 110 bpm is not high enough to cause tachycardia-mediated cardiomyopathy. Or else it may not be the higher heart rate but the irregular rhythm that's the major cause of heart failure, and the irregular rhythm rate was the same in both groups,” she noted.
Simultaneously with Dr. Van Gelder's presentation, the results were published online (N. Engl. J. Med. 2010 March 15 [doi:10.1056/NEJMoa1001337]).
Disclosures: RACE II was supported by the Netherlands Heart Foundation and unrestricted grants from seven pharmaceutical firms. Dr. Van Gelder has served as a consultant to Sanofi-Aventis, Boehringer Ingelheim, and Cardiome.
'A target resting heart rate just under 110 bpm on a 12-lead ECG is good enough.'
Source Dr. Van Gelder