Abstract & Commentary
Crystal and colleagues report a meta-analysis on the effects of pharmacologic or pacing therapy for the prevention of postoperative atrial fibrillation (AF) in patients undergoing heart surgery. Studies were included if they met all of the following criteria: randomized controlled trials of intervention vs. placebo or usual care; primary prevention of postoperative AF after coronary artery bypass surgery; treatment started immediately before, during the operation, or within the postoperative intensive care unit; a well-described intervention protocol; and adequate data on treatment efficacy. The primary outcome measure used for the meta-analysis was the incidence of postoperative AF or atrial flutter. Secondary outcome measures that were analyzed for selected studies were length of stay and the incidence of stroke.
There were 42 trials that evaluated the effects of beta-adrenergic blockers, sotalol or amiodarone, included in this series. The studies ranged between 36 and 1000 patients in size.
There were 27 trials that evaluated a beta blocker for prevention of postoperative AF. These trials included 3840 patients. In these trials, the AF incidence was 33% in the control group vs. 19% in the beta blocker group (odds ratio [OR], 0.39; 95% confidence interval [CI], 0.28-0.52). The test for heterogeneity in these trials was highly significant at P = 0.00001, and the reason for this was not explained. The test for overall effect was highly significant (P < 0.00001).
Eight trials were analyzed that evaluated the use of sotalol. These studies included 1294 patients. Sotalol reduced the incidence of AF from 37% in the control group to 17% in the treatment group (OR, 0.35; 95% CI, 0.26-0.49). There was no significant heterogeneity between the trials.
Nine trials evaluated the use of amiodarone. These trials included 1384 patients. Amiodarone reduced the incidence of AF from 37% in the control group to 22.5% in the amiodarone group (OR, 0.48; 95% CI, 0.37-0.61). There were 4 trials that compared sotalol and other beta blockers. These trials included 900 patients. Sotalol was associated with a decreased incidence of AF—22% vs. 12% (OR, 0.50; 95% CI, 0.34-0.74).
The effects of pacing on the incidence of postoperative AF were also examined. There were 10 trials that involved either right atrial pacing, left atrial pacing, or biatrial pacing. There was no standardization in the pacing algorithm used. Right atrial pacing was associated with an OR of 0.68 (95% CI, 0.39-1.19). Left atrial pacing was associated with an OR of 0.57 (95% CI, 0.28-1.16). Biatrial pacing was associated with an OR of 0.46 (95% CI, 0.30-0.71).
The effects of intervention on length of stay were reported by 2 beta blocker trials, 5 sotalol trials, and 5 amiodarone trials. Beta blockers and sotalol were associated with nonsignificant trends toward shortening of length of stay. Amiodarone reduced length of stay significantly by 0.91 days (95% CI, 1.59-0.24 days). Biatrial pacing also significantly reduced the length of stay.
The incidence of stroke was available only in 14 of the 52 trials, which covered 2877 patients. In these trials, the percentage of patients who developed AF was reduced from 38.6% in the control group to 23.7% in the treatment group. Despite this reduction, the incidence of stroke was 1.2% in the treatment group and 1.4% in the control group (OR, 0.90; 95% CI, 0.46-1.74). Crystal et al conclude that beta blockers, sotalol, and amiodarone are all effective for the prevention of postoperative atrial fibrillation. They recommend that beta blockers should be the first-line medication, with sotalol and amiodarone as appropriate alternatives (Crystal E, et al. Circulation. 2002;106:75-80).
Comment by John P. DiMarco, MD, PhD
Postoperative AF remains a frustrating problem for cardiologists and cardiovascular surgeons. In patients without a prior history of AF, postoperative AF usually occurs between the second and sixth postoperative day and usually will resolve within the first 2-4 weeks after the operation. As noted in this review, strategies to prevent postoperative AF have included beta blocker therapy, antiarrhythmic drugs, and pacing strategies.
The data here show that beta blockers remain the mainstay of the strategy for reducing the incidence of postoperative AF. Therapy with beta blockers is inexpensive, well tolerated, and easy to initiate. More powerful antiarrhythmic drugs or pacing strategies should be considered either in conjunction with beta blockers if beta blockers have failed or if there is a very high preoperative probability for developing AF. Patients with a prior history of AF or mitral valve disease would be candidates for a more aggressive approach.
It should be noted however that none of these strategies eliminate postoperative AF. The next step in trials might be a combination of beta blockers with either pacing or amiodarone to see if that would further reduce the incidence. It should also be remembered that left atrial radiofrequency lesions placed at the time of surgery could eliminate late AF in many patients. This latter procedure is becoming more widespread in patients undergoing mitral valve surgery.
Dr. DiMarco is Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville.