Intraoperative mapping of the right atrial free wall during sinus rhythm: variety of activation patterns and incidence of postoperative atrial fibrillation.

OBJECTIVE The atrial conduction properties associated with cardiac disease are speculated as the background of postoperative atrial fibrillation (POAF). We examined the atrial conduction patterns and conduction properties during sinus rhythm (SR) in patients that had undergone cardiac operations and evaluated the incidence of POAF in all patients. METHODS Fifty-two patients with stable SR who underwent cardiac surgery, with a diagnosis of valvular disease in 25, ischemic heart disease in 24, and others in 3, were enrolled in this study. The epicardial recordings were made using a mapping system with 60 unipolar electrodes placed on the right atrium (RA) intraoperatively. The activation patterns of the RA were assessed, and the longitudinal, transverse and oblique conduction velocity and max anisotropic ratio were also examined. RESULTS Sinus activation was initiated from various sites (single origin at the high-lateral RA in 40, mid-lateral RA in 4, low-lateral RA in 2, and multiple origins in 6 patients) and it demonstrated anisotropic conduction (1.8+/-0.6) with the longitudinal conduction being more rapid than transverse and oblique conduction. Fifteen patients demonstrated non-uniform activation patterns such as, a localized conduction delay in seven, functional conduction block in two and mosaic-activation pattern associated with multiple origins in six. A total of 21 patients (44%) developed POAF. A conduction delay and mosaic activation pattern was found significantly more often in patients with POAF than in patients who remained in sinus rhythm. Multivariate analysis revealed that non-uniform activation pattern (odds ratio=8.71; 95% confidence interval [CI]=1.74-43.67; p=0.008) and TR (odds ratio=4.95; 95% CI=1.14-21.37; p=0.032) were independently associated with the development of POAF. Although all patients had converted to SR at the time of discharge, the administration of antiarrhythmic drugs caused sinus bradycardia in two patients who demonstrated a mosaic activation pattern in RA. CONCLUSIONS Cardiac surgery patients exhibited a variety of sinus activation patterns, which also provided an arrhythmogenic substrate for POAF. A better understanding of the sinus activation using an intraoperative mapping system may provide benefit in the clinical management of POAF.