Effect of intravenous diltiazem and digoxin on atrial fibrillation after on-pump coronary artery bypass surgery

Abstract

Atrial fibrillation (AF) occurs in 10–40% of patients undergoing coronary artery bypass surgery (CABG). The purpose of this study is to determine predictors of the time to occurrence of AF after CABG and the impact of intravenous diltiazem and digoxin on acutely (<6 hours) controlling heart rate (≤ 100/minute) and converting AF to normal sinus rhythm (NSR). We performed a retrospective review of 151 consecutive patients who had undergone CABG during a four-month period at our institution. Patients who developed AF postoperatively were treated at the discretion of the attending physician with the combination of IV diltiazem and digoxin, as per an approved protocol by a hospital committee. Univariate analysis using chi-square and Student’s t-test was performed. Cox Proportional Hazards Model was performed to determine variables that predicted the time to occurrence of AF. Time to achieve rate control (≤ 100/minute) was recorded in patients who did not convert to NSR. Arrhythmia control was defined as either conversion to NSR or rate control within six hours of initiation of treatment. AF occurred in 59 patients (39%) at a mean of 2.17 days following surgery, and 29 patients received immediate IV diltiazem (bolus 0.25 mg/kg followed by 5 mg/hr incremental drip) and digoxin (0.75 mg IV load). Acute conversion to NSR occurred in 21/29 (72%) patients. Arrhythmia control was achieved in 24/29 (83%) patients. Patients who developed AF and were on beta-blockers (BB) derived no incremental benefit from the addition of IV diltiazem and digexin in converting to NSR (p = NS). Using Cox Proportional Hazards Model, history of AF (p < 0.0001), age (p < 0.001), and chronic obstructive pulmonary disease (COPD) (p = 0.028) were significant variables in predicting the time to occurrence of AF. AF occurs frequently after CABG, and the combination of IV diltiazem and digoxin appears to be effective in rate control and was associated with a high conversion rate to NSR. History of AF, age, and COPD predicted the time to occurrence of AF.