Post-CABG Atrial Fibrillation

Atrial fibrillation (Af) is the most common postoperative arrhythmic complication in patients undergoing coronary artery bypass grafting. The pathophysiological mechanism underlying the postoperative Af is not clearly understood. Although postoperative Af is generally considered to be paroxysmal and harmless, it may compromise hemodynamic conditions in patients with left ventricular dysfunction and possibly increases the risks of cerebrovascular accidents. Its prevention remains suboptimal and the rhythm disturbance itself is sometimes attributed to prolonged hospital stay and increased cost associated with Af. This study aims to evaluate clinical predictors of postoperative Af, the treatment effects of Amiodarone, and the prognosis of the patients with postoperative Af.
Methods:
Patients undergoing simple CABG in the absence of permanent Af (n = 250, between May 1999 and Dec. 2006) were recruited to the present case-control study. The techniques of CABG included on-pump arrest CABG, off-pump coronary artery bypass (OPCAB), and minimally invasive direct coronary bypass surgery (MIDCAB). The clinical risk factors were evaluated according to the triggers, the substance, and the modulators, which constitute the elements of atrial fibrillation. Patients who developed postoperative Af was treated with intravenous Amiodarone injection. The responders were identified as three groups: the immediate responders, recurrent Af and delayed responders. Further evaluations were made between the three groups. All the patients were followed up postoperatively after discharge from the hospital for ischemic events, fatal events, CVA and the incidence of permanent Af.
Results:
The incidence of postoperative Af in this study was 27%. Most of the AF occurred 1-3 day postoperatively (mean 2.4 days). The demographic data between the Af patients and NSR patients was comparable. In the analysis of risk factors, there were no statistically significant triggers related to postoperative Af. Logistic regression identified age (OR 1.057, 95% CI 1.057-1.090),male (OR 1.921,95% CI 1.019-3.621),and preoperative atrial arrhythmia (OR 13.435,95% CI 2.598-69.488) as major risk factors. As for the modulators, beta blockers taken preoperatively could lower the incidence of Af (OR 0.511,95% CI 0.274-0.954), while Amiodarone paradoxically increased the incidence of af (OR 4.563,95% CI 1.222-17.038). Both factors became obscure once entered the logistic regression. Amiodarone injection converted 79.4% Af to NSR within 24 hours. Two patients (2.94%) had bradycardia and needed to hold the drug or started Isoproterenol i.v. infusion. 39.7% patients got immediate response and regained NSR. In 29.4% patients, Af recurred and need another injections or continuous infusion.30.9% patients did not respond to the first injections and regained NSR after continuous i.v. infusion for some time. In the recurrent group, age, sex and preoperative atrial arrhythmia seemed to be significant risk factors, with age>70 OR 13.183,95% CI 2.428-71.577,female OR 0.227,95% CI 0.056-0.923,and atrial arrhythmia OR 8.264,95% CI 1.175-58.143. Significantly 3 patients contracted permanent Af late during follow up. Otherwise, postoperative Af did not affected CABG prognosis. The ischemic events, the fatal events and the incidence of CVA did not make significant differences between those who remained sinus rhythm postoperatively and those who did not.
Conclusions:
Postoperative Af is a common and benign complication after coronary bypass surgery. Advancing age and preoperative atrial arrhythmia seemed to be the most powerful contributing risk factors. Beta blocker remained the significant modulator. Although there are newer antiarrhythmic agents for the treatment or prevention of Af, Amiodarone could be used for postoperative Af in CABG with acceptable conversion rates and minimum complications. In usual conditions, it does not increase hospital stay and thus hospital cost. The mere occurrence of postoperative Af is not related to the prognosis of CABG. But there is chance that postoperative Af may predispose to permanent Af.