Prophylaxis to Reduce Postoperative Atrial Fibrillation in Cardiac Surgery

Overview

Atrial Fibrillation (AF) is a common postoperative complication of cardiac surgery, occuring in approximately 25-30% of coronary artery bypass graft (CABG) patients and 35-40% of heart valve repair/replacement patients. Efforts to decrease the high rates of AF have not made great inroads to the problem. The current standard of care is the use of preoperative and postoperative beta blockers. We propose to compare the use of prophylactic oral ascorbic acid with and without prophylactic oral amiodarone, in combination with oral beta blockers, for the prevention of atrial fibrillation after open heart surgery. The hypothesis is that either drug, or a combination of the two drugs, will be superior and safe when compared to beta blockers alone.

Atrial fibrillation is a common complication of cardiac surgery which is associated with increased morbidity, length of stay and cost. Efforts to mitigate this problem with beta blockers and amiodarone have been met with limited success. Observational data suggests that prophylactic amiodarone has been helpful in decreasing the incidence of AF as well as increasing its ease of management. The opportunity to use ascorbic acid for AF prophylaxis is attractive because of its low side effect profile, wide acceptance and low cost. We have designed a prospective, randomized, controlled trial using a 2 X 2 factorial design to determine whether prophylactic ascorbic acid alone, ascorbic acid with amiodarone, or amiodarone alone, when given along with beta blockers will decrease the incidence of postoperative AF in adult cardiac surgery in all comers as compared with beta blockers alone. Patients will be randomized into four groups, A, B, C, and D. All groups will receive beta blockers, Group A will receive beta blockers, ascorbic acid, and amiodarone, Group B will receive ascorbic acid and Beta blockers, Group C will receive amiodarone and beta blockers and Group D will receive only beta blockers. Success of randomization will be assessed by comparing treatment groups with respect to baseline characteristics, using t-tests or their nonparametric equivalent (as appropriate) for continuous variables and chisquare tests or Fisher's exact tests for categorical variables. The primary hypotheses of the effects of ascorbic acid and amiodarone on incidence of atrial fibrillation will be tested using chisquare tests for differences in proportions. No adjustment will be made for multiple comparisons since both hypotheses are pre-specified. We will use exploratory analyses including stratification to assess for the possibility of effect modification between ascorbic acid and amiodarone. If an interaction is suggested by these analyses, we will use logistic regression with a cross-product term as a formal statistical test for interaction.