Atrial fibrillation in the immediate post-operative period following cardiac surgery is a common clinical problem, occurring in 10-40% of patients.  As with atrial fibrillation in any clinical setting, post-operative atrial fibrillation is associated with rapid ventricular response, congestive heart failure, and arterial embolization and stroke.  Independent of these complications, post-operative atrial fibrillation is also an important cause of increased hospital length of stay and increased hospital costs in these patients.  Its prevention would be of obvious benefit. This issue of the Arrhythmia News will discuss recent reports in the literature describing its occurrence and possible strategies for its prevention. 

Risk Factors 

 Several studies have attempted to assess risk factors that are associated with the post-operative development of atrial fibrillation. In the largest of these studies, which evaluated 2417 patients, increasing age, male gender, a history of pre-operative atrial fibrillation, and pre-operative congestive heart failure were associated with an increased incidence of post-operative atrial fibrillation.  In this study, various cannulation techniques and longer  cross-clamp times during surgery were also associated with a higher incidence of atrial fibrillation.  Studies from our institution have also shown that prolonged atrial activation (abnormal pre-operative p-wave signal-averaged ECG) is also associated with post-operative atrial fibrillation (Circulation 1993;88:2618-22). 

Prophylaxis 

 Increased sympathetic activation appears to be important in the pathogenesis of post-operative atrial fibrillation.  As such, several studies have suggested that beta-blocker therapy is successful in preventing post-operative atrial fibrillation, reducing the incidence as much as 55%.  Optimally, beta-blocker therapy is initiated pre-operatively and re-initiated immediately after surgery as an intravenous medication.  However, some studies have offered conflicting results regarding the preventative effects of beta-blockers.  In addition, conditions such as obstructive lung disease and congestive heart failure limit the use of beta-blockers. 

 Several studies have also suggested that Type 3 antiarrhythmic agents may be valuable in preventing post-operative atrial fibrillation.  Sotalol, a type 3 agent with beta-blocking properties, has been shown to significantly reduce the incidence of post-operative atrial fibrillation when administered pre-and post-operatively.  However, in these studies its use has also been limited by side effects associated with its beta-blocking.  In addition, sotalol may carry with it a significant risk of ventricular pro-arrhythmia, making it less than ideal in patients with coronary artery disease. 

 A study recently published in the New England Journal of Medicine (NEJM 1997;337:1785-91), suggests significant promise for amiodarone as a prophylactic agent for post-operative atrial fibrillation. In this study, 124 patients undergoing non-emergent cardiac surgery were randomized to either amiodarone (200 mg tid x 7 days, then 200 mg qd until discharge) or placebo. Patients on amiodarone were hospitalized for significantly fewer days (6.5 days vs. 7.9 days for the placebo group). In addition, the total cost of hospitalization was significantly lower in the amiodarone group ($18,375 vs. $26,491 for the placebo group). Complication rates and mortality outcomes were similar between the two groups.  However, in this study, amiodarone was started an average of 13 days prior to the hospitalization for cardiac surgery.  The efficacy of prophylactic amiodarone when given for shorter durations prior to the cardiac surgery is unclear. 

 Clearly prophylactic treatment with beta-blockers and possibly amiodarone is well tolerated and may be highly effective in the prevention of peri-operative atrial fibrillation. The benefits of prophylactic therapy include significant reductions in morbidity (but not necessarily mortality), hospital length of stay and overall costs. This therapy should be considered in all patients, especially those at highest risk for peri-operative atrial fibrillation. 

Reproduced with permission. Published by the Arrhythmia Service of St. Luke's-Roosevelt Hospital Center, New York, New York.