Heart Rate in Afib No Guarantee for Quality of Life
By Crystal Phend, Senior Staff Writer,
Published: October 11, 2011
Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston and
Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner
Action Points
Explain that a study randomizing patients with permanent atrial fibrillation to lenient or strict rate control did not result in differences in perceived quality of life between the groups.
Note that many patients were not symptomatic at baseline in either group and that quality of life was determined by answers to a questionnaire.
Stricter rate control for patients with permanent atrial fibrillation doesn't improve quality of life, a clinical trial showed.
More lenient control to a resting heart rate under 110 beats per minute showed no difference on any quality-of-life measure compared with strict control to less than 80 bpm, Isabelle C. Van Gelder, MD, of the University Medical Center Groningen, the Netherlands, and colleagues found.
Factors that did matter for well-being were symptoms, sex, age, and underlying disease severity, they reported in the Oct. 18 issue of the Journal of the American College of Cardiology.
These substudy results from the RACE II (Rate Control Efficacy in Permanent Atrial Fibrillation II) trial add to the primary endpoint showing no advantage to strict control for adverse outcomes.
Those findings go against common clinical assumptions, noted Paul Dorian, MD, MSc, of St. Michael's Hospital, and Andrew C.T. Ha, MD, of Toronto General Hospital, both in Toronto.
"For example, many physicians may assume that a rapid and irregular heart rate is undesirable, and implicitly subjectively undesirable, compared with a slower, more well-controlled rate," they wrote in an accompanying editorial.
That this wasn't the case for the study population -- largely those with "long-standing and not terribly symptomatic atrial fibrillation" -- points to the need to individualize decisions to intensify rate control, Dorian and Ha argued.
"Clinicians need to be aware that patient personality, treatment expectations, and factors unrelated to the arrhythmia itself will have important, potentially determining influences on the extent to which atrial fibrillation causes suffering," they wrote.
The researchers agreed that different groups, such as highly symptomatic patients, might feel better with tighter rate control.
RACE II included 614 permanent atrial fibrillation patients randomized to rate control classified as lenient or strict based on a target of less than 110 bpm at rest versus less than 80 bpm or less than 110 bpm if exercising moderately.
The substudy included the 437 who completed quality-of-life questionnaires at baseline, one year, and at the end of study after a median of three years.
The prevalence of symptoms -- largely dyspnea, fatigue, and palpitations -- declined somewhat during follow-up to 48% from 58% at baseline, though without a difference between rate control groups.
Initial heart rate didn't predict quality of life at baseline, nor did change in quality-of-life correlate with heart rate.
The strict and lenient rate control groups came out similar for all quality of life measures at 12 months and at the end of the study on the Medical Outcomes Study 36-item Short-Form Health Survey (SF-36) questionnaire.
The atrial fibrillation severity scale and the Multidimensional Fatigue Inventory-20 likewise showed no differences between rate control strategies at any point and a lack of correlation with heart rate.
The lack of relative improvement with stricter control of heart rate may have reflected that patients were already at a relatively low symptom level at baseline and so had little room for improvement whatever the treatment strategy, the researchers noted.
Indeed one of the determinants of improvement on the SF-36 and atrial fibrillation severity scale was symptoms at baseline.
Other predictors of improvement on the SF-36 included absence of symptoms at the end of the study, higher left ventricular ejection fraction, younger age, and a thinner septum, and younger age alone for the atrial fibrillation severity scale.
Possible explanations for the findings also may have been that symptoms driven more by underlying heart disease or by ventricular irregularity weren't impacted by degree of rate control or that the higher doses of rate control drugs in the strict control group actually adversely affected quality of life.
Van Gelder's group cautioned that the results could not be generalized to patients without permanent atrial fibrillation or who are highly symptomatic.
Other limitations were that strategies to achieve heart rate targets differed between groups and the quality of life questionnaires may not have been sensitive enough, they added.