Systematic electrocardioversion for atrial fibrillation and role of antiarrhythmic drugs: a substudy of the SAFE-T trial.

BACKGROUND

Energy levels for electrocardioversion in atrial fibrillation (AF) have been empiric, and the influence of antiarrhythmic therapy compared with placebo is largely unknown.

OBJECTIVE

The purpose of this study was to determine systematically the energy levels for electrocardioversion in patients with persistent AF and to define the influence of antiarrhythmic therapy.

METHODS

Patients (n = 665) with persistent AF were randomized to amiodarone, sotalol, or placebo. Rate control, if necessary, was achieved with digoxin, diltiazem, or verapamil. Among the 665 patients, 504 who did not achieve sinus rhythm at day 28 had electrocardioversion systematically by a prespecified four-step protocol as follows: monophasic shocks-100, 200, 360, 360 J; or biphasic shocks-150, 175, 200, 200 J sequentially. Energy levels and shock waveforms (monophasic/biphasic) for successful electrocardioversion (sinus rhythm for at least 1 minute) and use of antiarrhythmic therapy and calcium channel blockers were recorded.

RESULTS

Electrocardioversion was successful in 371 (71.6%) of 504 patients: 72%, 73.5%, and 67.9% for patients assigned to amiodarone, sotalol, and placebo, respectively. Overall, after adjustments for age, body mass index (BMI), history of AF, shock waveforms, left atrial size, and ejection fraction, both amiodarone (odds ratio [OR]: 2.16, 95% confidence interval [CI]: 1.24-3.77, P <.01) and sotalol (OR: 1.92, 95% CI: 1.11-3.33, P = .02) significantly facilitated successful electrocardioversion compared with placebo. Calcium channel blockers had no effect on the success rate of electrocardioversion. Success of electrocardioversion was associated with lower BMI, AF history < or =1 year, and older age. Compared with placebo, patients taking amiodarone were significantly more likely to achieve successful electrocardioversion in step 1 (OR: 2.73, 95% CI: 1.11-6.74, P = .03) and step 3 (OR: 1.86, 95% CI: 1.00-3.44, P = .05) but not in steps 2 and 4. Sotalol was superior to placebo in step 4 (OR: 2.58, 95% CI: 1.02-6.52, P = .05) and trended in step 2 (OR: 1.7, 95% CI: 0.98-3.07, P = .06). Successful electrocardioversion was seen in 11%, 29%, 38%, and 29% in steps 1, 2, 3, and 4, respectively. Compared with monophasic shocks, biphasic shocks achieved higher success rates for step 1 (P <.001) and step 2 (P <.01), respectively. Antiarrhythmic therapy did not influence the total number of energy steps used for the patients with successful electrocardioversion. However, biphasic shocks, lower BMI, and AF duration < or =1 year were associated with less energy step used for successful cardioversion.

CONCLUSION

Amiodarone and sotalol facilitated successful electrocardioversion, which could be achieved in a stepwise fashion. Upon achievement of successful electrocardioversion, amiodarone is superior to placebo, and sotalol has a lesser effect. Antiarrhythmic drugs had no effect on the total number of energy step use in patients who had successful electrocardioversion. Calcium channel blockers had no influence on the success rate in achieving sinus rhythm. Successful electrocardioversion was associated with lower BMI and AF history < or =1 year. Lower energy use was associated with biphasic shocks, lower BMI, and AF duration < or =1 year.