Exercise capacity in atrial fibrillation: a substudy of the Sotalol-Amiodarone Atrial Fibrillation Efficacy Trial (SAFE-T).
BACKGROUND
Therapy for chronic atrial fibrillation (AF) focuses on rate versus rhythm control, but little is known about the effects of common therapeutic interventions on exercise tolerance in AF.


METHODS
Six hundred fifty-five patients with chronic AF underwent maximal exercise testing at baseline and 8 weeks, 6 months, and 1 year after randomization to sotalol, amiodarone, or placebo therapy and attempted direct current cardioversion. Analyses of baseline determinants of exercise capacity, predictors of change in exercise capacity at 6 months and 1 year, and the short- and long-term effects of cardioversion on exercise capacity were made.


RESULTS
Age, obesity, and presence of symptoms accompanying AF were inversely associated with baseline exercise capacity, but these factors accounted for only 10% of the variance in exercise capacity. Patients most likely to benefit from cardioversion were those most limited initially, younger, not obese or hypertensive, and with an uncontrolled ventricular rate at baseline. Conversion to sinus rhythm (SR) resulted in significant reductions in resting (approximately 25 beat/min) and peak exercise (approximately 40 beat/min) heart rates at 6 months and 1 year (P < .001). Successful cardioversion improved exercise capacity by 15% at 8 weeks, and these improvements were maintained throughout the year. This improvement was observed both among those who maintained SR and those with intermittent AF.


CONCLUSIONS
Cardioversion resulted in a sustained improvement in exercise capacity over the course of 1 year, and this improvement was similar between those in SR and those with SR and recurrent AF. Patients most likely to improve with treatment tended to be younger and nonobese and have the greatest limitations initially.
Atwood
J Edwin
JE
Cardiology Division, Walter Reed Army Medical Center, 6900 Georgia Ave NW, Washington, DC 20307, USA. john.atwood@amedd.army.mil
Myers
Jonathan N
JN
Tang
X Charlene
XC
Reda
Domenic J
DJ
Singh
Steven N
SN
Singh
Bramah N
BN
D000368:Aged; D000638:Amiodarone / Q000627:therapeutic use*; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy*; D004311:Double-Blind Method; D004554:Electric Countershock; D017079:Exercise Tolerance; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D013015:Sotalol / Q000627:therapeutic use*
D000889:Anti-Arrhythmia Agents; D013015:Sotalol; D000638:Amiodarone