To analyze abnormal ventricular activation in childhood congenital heart disease induced by postoperative changes in ventricular volume and pressure and ventricular scar formation using signal-averaged electrocardiography (SAECG).

Fifty-two patients who had undergone open heart surgery (OHS) were enrolled. Patients were divided into the following 3 groups: right ventricular volume overload (atrial septal defect, group1), left ventricular volume overload (ventricular septal defect, group2), and right ventricular pressure overload (tetralogy of Fallot, group 3). The patients were monitored by standard 12-lead ECG and SAECG before and 2 months after the operation. QRS duration, QT and QTc intervals, filtered QRS (f-QRS), high frequency low amplitude potential (HFLA), and root mean square (RMS) voltage in the terminal 40 ms of SAECG were determined.

In the preoperative period, group1 showed significant increase in QRS ( P =0.011) compared to those of the other 2 groups. In the postoperative period, group3 showed significant increase in the QTc interval ( P =0.004) compared to those in the other 2 groups. SAECG parameters showed no significant differences among the groups in the pre- or postoperative period. Of the 52 patients, 12 (23%) in the preoperative period and 21 (40%) in the postoperative period had at least 1 SAECG abnormality. The prevalence of SAECG abnormalities was significantly higher in the postoperative group 2 and group 3 (preoperative: 20% versus postoperative: 28%, P <0.001, preoperative: 14% versus postoperative: 64%, P <0.001, respectively).

Abnormal SAECG patterns may be attributed to postoperative scars, OHS itself, and/or ventricular overload.