Atrial Fibrillation After Cardiac Surgery: Electrophysiological Mechanism and Outcome

Background Postoperative atrial fibrillation (POAF) is common after cardiac surgery and is associated with an inferior outcome. The high cure rate compared with non-POAF raises questions regarding the electrophysiologic mechanism. Despite being common, until now the electrophysiologic mechanism of POAF was never assessed. Methods Ten patients (5 men; mean age, 75 ± 5 years) with POAF underwent noninvasive 3-dimensional beat-by-beat mapping and were compared with 10 patients (6 men; mean age, 70 ± 10 years) with preoperative persistent AF (PEAF) undergoing open heart procedures. Three-dimensional mappings were compared by the nature and location of focal and rotor activity using the validated Bordeaux classification. Results Rotor activity was present in both atria of all patients; 299 rotors (mean, 30 ± 12) were mapped in the POAF group and 289 (mean, 29 ± 22) in the PEAF group. The most common region for macro reentry in both groups was the pulmonary vein area. Left atrium and left atrial appendage activity accounted for 59% (177/299 POAF group) and 62% (180/289 PEAF group) of all drivers. Rotor activity in the right atrium was documented in all patients. Focal activity was captured in only 2 patients in the POAF group and in 6 patients in the PEAF group. Conclusions The mechanism of POAF is comparable with that of PEAF. Rotor activity was similar in both groups, but focal activity was numerically less common in the POAF group, which may be related to differences in atrial tissue remodeling. In POAF, transient substrate changes seem to facilitate the development of AF. A better understanding of atrial tissue changes by mapping and tissue analysis should lead to better preventive approaches.