Atrial fibrillation, the most common sustained clinical arrhythmia, is increasing in prevalence. In addition to impaired quality of life caused by symptoms, patients with atrial fibrillation are at risk of serious complications such as cardiomyopathy and embolism. Many treatments of atrial fibrillation aim to restore and maintain sinus rhythm. Because of the limited success with and the potential hazards of antiarrhythmia medications, an alternative management strategy of controlling ventricular rate has been advocated. Hohnloser and colleagues, acting with the Pharmacological Intervention in Atrial Fibrillation (PIAF) trial group, led a large European study to clarify the “rate or rhythm” controversy in the treatment of atrial fibrillation.
This randomized trial studied patients 18 to 75 years of age with established symptomatic atrial fibrillation that had lasted seven to 360 days. Patients were excluded from the study for several reasons, including unstable angina, advanced heart failure, bradycardia of fewer than 50 beats per minute, recent cardiac surgery and evidence of embolism. Patients were randomly assigned to rate control based on diltiazem therapy or antiarrhythmia treatment using pharmacologic and/or electric conversion. All patients received anticoagulation therapy and were followed for one year. The primary outcome monitored was improvement in symptoms.
The 125 patients who were assigned to rate control were comparable to the 127 patients assigned to rhythm control, including similar types of medications used at the beginning of the study. About 122 patients in the rate group and 120 patients in the rhythm group completed the study. In each group, over one half of the patients responded to therapy (76 patients in the rate group and 70 patients in the rhythm group). No baseline factors appeared to predict patients who responded. The two groups showed no significant differences in overall quality of life at the end of the study. Patients in the rhythm-control group experienced significantly more improvement in exercise tolerance as measured by the six-minute walk test. Conversely, these patients also had more hospital admissions, although many of them were related to cardioversion. Patients in the rhythm-control group also had more adverse effects related to medication. At least one drug-related adverse effect occurred in 64 percent of patients in the rhythm-control group compared with 47 percent of patients in the rate-control group. Because of adverse drug effects, therapy had to be changed in 25 percent of the rhythm-control patients and in 14 percent of those on rate-controlling therapy.
The authors conclude that, overall, both strategies lead to similar functional results. Exercise tolerance improved more with rhythm control, but this strategy is associated with more adverse drug effects and hospital admissions.