Reproducibility of local activation times during intraoperative epicardial mapping.

The reproducibility of the measurement of local epicardial activation times using in- traoperative epicardial mapping was studied in 10 patients. Two multipolar electrodes were used, one as a reference located on the anterior surface of the right ventricle, the other as a hand-held probe for depicting local activation times. During atrial pacing at 100 beats/min, activation times at various sites of the heart were measured consecutively using a grid system that defined 75 points on the surface of the heart. The surface of the heart was divided into three areas: the anterior wall of the right ventricle, the left lateral wall and the posterior wall of both ventricles. The measurements were repeated twice at the same paced atrial rate. From these data the mean absolute differences between the first and second measurements were calculated for each point.