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

Objective-To evaluate the effect of cardioversion on peak oxygen consumption (peak Vo(2)) 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 combination of both to attain a resting heart rate less than or equal to 100 beats per minute.Interventions-Electrical cardioversion.Main outcome measures-Peak Vo(2) 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 Vo(2) 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 Vo(2) was unchanged. In patients who were in sinus rhythm both those with and without underlying heart disease improved, and improvement was not related to funct ional capacity or left ventricular function before cardioversion. Baseline peak Vo(2) was not a predictive factor for longterm arrhythmia outcome.Conclusion-Restoration of sinus rhythm improved peak Vo, in patients with atrial fibrillation, irrespective of the presence of underlying heart disease. Peak Vo(2) 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.