Functional capacity before and after cardioversion of atrial fibrillation: a controlled study.

OBJECTIVE To evaluate the effect of cardioversion on peak oxygen consumption (peak VO2) in patients with long-standing atrial fibrillation, to assess the importance of underlying heart disease with respect to the response to exercise, and to relate functional capacity to long-term arrhythmia outcome. DESIGN Prospective controlled clinical trial. SETTING Tertiary referral centre. PATIENTS 63 consecutive patients with chronic atrial fibrillation accepted for treatment with electrical cardioversion. Before cardioversion all patients were treated with digoxin, verapamil, or a combination of both to attain a resting heart rate < or = 100 beats per minute. INTERVENTIONS Electrical cardioversion. MAIN OUTCOME MEASURES Peak VO2 measured before and 1 month after electrical cardioversion to compare patients who were in sinus rhythm and those in atrial fibrillation at these times. Maintenance of sinus rhythm for a mean follow up of 19 (7) months. RESULTS Mean (1SD) peak VO2 in patients in sinus rhythm after 1 month (n = 37) increased from 21.4 (5.8) to 23.7 (6.4) ml/min/kg (+11%, P < 0.05), whereas in patients with a recurrence of atrial fibrillation 1 month after cardioversion (n = 26) peak VO2 was unchanged. In patients who were in sinus rhythm both those with and without underlying heart disease improved, and improvement was not related to functional capacity or left ventricular function before cardioversion. Baseline peak VO2 was not a predictive factor for long-term arrhythmia outcome. CONCLUSION Restoration of sinus rhythm improved peak VO2 in patients with atrial fibrillation, irrespective of the presence of underlying heart disease. Peak VO2 was not a predictive factor for long-term arrhythmia outcome after cardioversion of atrial fibrillation. These findings suggest that cardioversion is the best method of improving functional capacity in patients with atrial fibrillation, whether or not they have underlying heart disease and whatever their functional state.