Atrial fibrillation occurs in up to 40 percent of patients following open heart surgery and increases the risk of heart failure, ventricular arrhythmias, stroke and other complications. More than one half of the 598,000 coronary artery bypass graft surgeries performed in the United States every year involve patients 65 years of age and older, and age is the most powerful predictor of postoperative atrial fibrillation. Although beta blockers and amiodarone can reduce the occurrence of postoperative atrial fibrillation, most data have been collected on younger patients. Giri and colleagues studied the efficacy and safety of oral amiodarone in older patients receiving beta blockers as part of care following various forms of open heart surgery.
Patients scheduled for elective heart surgery were eligible for the study if they were at least 60 years of age, hemodynamically stable and in normal sinus rhythm, and had a baseline corrected QT interval of 440 ms or less. Patients with atrial fibrillation, bradycardia, advanced heart block, recent myocardial infarction or a pacemaker were excluded. Other reasons for exclusion were history of toxicity from amiodarone or use of interacting drugs, untreated thyroid disease and abnormal hepatic enzyme levels on screening.
All patients underwent physical examination and laboratory screening during preparation for surgery and inclusion in the study. The 220 eligible patients were randomly assigned to receive either amiodarone or placebo. If enrolled early, patients received 200 mg of amiodarone three times daily for five days before surgery, 400 mg twice daily on the day of surgery and 400 mg twice daily on the first four days after surgery. The 64 patients who followed this regimen were matched to 56 patients receiving placebo on the same schedule.
The 56 patients enrolled closer to the day of surgery were treated with 400 mg of amiodarone four times daily for one day, then 600 mg twice daily on the day of surgery and 400 mg twice daily on days 1 through 4 following surgery. These patients were matched to 44 similar patients who received placebo on the same schedule.
The average age of the patients was 73 years, and 196 (89 percent) of the 220 patients received beta blockers as part of the institutional critical pathway for postoperative care. Atrial fibrillation occurred in 22.5 percent of the patients receiving amiodarone compared with 38 percent of those taking placebo. The patients treated with amiodarone also showed significant benefit in the occurrence of symptomatic atrial fibrillation (4.2 percent versus 18.0 percent), cerebrovascular accidents (1.7 percent versus 7.0 percent) and ventricular tachycardia (1.7 percent versus 7.0 percent). The occurrence of atrial fibrillation was not significantly influenced by the preoperative loading schedule in patients treated with amiodarone. Four patients taking amiodarone and four patients taking placebo died during the study. Patients receiving amiodarone had higher rates of nausea (27 percent compared with 16 percent), but the difference in nausea and other side effects was not statistically significant. A cost estimate found that the total accrued costs were significantly lower for amiodarone therapy.
The authors conclude that oral amiodarone reduces atrial fibrillation and, hence, other complications of cardiac surgery in elderly patients already treated with beta blockers.