OBJECTIVE: Atrial fibrillation after coronary artery bypass operations remains frequent and increases morbidity, as well as resource use. Its cause remains unclear. The introduction of a minimally invasive technique provides an opportunity to evaluate the effect of intraoperative factors, such as cardiopulmonary bypass, global myocardial ischemia, and myocardial protection technique, on the occurrence of this arrhythmia. METHODS: All the patients undergoing isolated left internal thoracic artery-left anterior descending artery grafting between January 1994 and December 1999 were reviewed. Twenty possible risk factors for postoperative atrial fibrillation, including the choice of operative technique--minimally invasive technique was introduced in January 1997--were entered into univariate and multivariable logistic regression analysis. RESULTS: Postoperative atrial fibrillation occurred in 36 (20%) of 183 patients. On univariate analysis, age (P <.001) and a history of supraventricular arrhythmia (P <.001) were found to be risk factors. In particular, 15 (22%) of 69 patients operated on with the minimally invasive technique had postoperative atrial fibrillation versus 21 (18%) of 114 in the standard group (P =.58). On multivariable analysis, including the operative technique, the same variables (P =.001 and.01, respectively) were identified as independent risk factors. CONCLUSIONS: The introduction of a minimally invasive technique for coronary artery bypass operations did not reduce the occurrence of postoperative atrial fibrillation in this study population. This suggests that prophylactic measures to reduce this arrhythmia should be focused on factors unrelated to cardiopulmonary bypass or myocardial preservation technique.