Efficacy of intraoperative mapping to optimize the surgical ablation of atrial fibrillation in cardiac surgery

Background. Observation during open heart surgery in patients with chronic atrial fibrillation (AF) showed that the activation sequence of the left atrium was regular and that of the right atrium chaotic in most patients. We speculate that the left atrium plays a role as an important electrical driving chamber for AF and by mapping preoperatively, optimal sites for the cryoablation can be determined to minimize the extensiveness of the cryolesions. Methods. Forty patients who underwent cardiac surgery and cryoablation guided by epicardial mapping data to eliminate AF originating from the left atrium were included in this study. Results. Sustained reentrant movement or repetitive firing from foci located in the right atrium was never observed. Foci or reentry circuits located in the left atrium were clearly identified in 11 cases. Nine of the 11 cases resumed sinus rhythm by placing cryolesions at these sites. Two cases needed a pacemaker implantation. The exact site had not been identified in the 29 remaining cases. In these 29 cases a left atrial posterior longitudinal linear cryoablation was placed. Sinus rhythm resumed in 22 cases. Six cases still remained in AF and a pacemaker was implanted in 1 case. Ultimately, in this series of operations sinus rhythm was resumed in 31 of 40 cases; AF remained in 6 of them and pacemaker implantation was required in 3 cases. Conclusions. Mapping was useful to distinguish the two etiologies of the AF to facilitate optimal placement of the cryolesions. Sustained reentrant movement or repetitive firing from foci located in the right atrium was never observed and the left atrium played an important role as the electrical driving chamber for AF.