Usefulness of post-ventriculotomy signal averaged electrocardiograms in congenital heart disease.

Signal-averaged electrocardiography is a sensitive and specific technique for detecting the slow conduction electrophysiologic substrates of reentrant monomorphic ventricular tachycardia. Although well established, the method has not been used for electrophysiologic assessment after right ventriculotomy for the intracardiac repair of congenital heart disease. This 8-year prospective study provided this assessment. Recordings were obtained from 242 post-ventriculotomy patients with congenital heart disease aged 16 to 72 years (139 males, 103 females). Because ventricular volume or pressure overload can prolong the QRS duration, 40 unoperated patients with hemodynamic overload served as controls. Orthogonal X, Y, and Z body surface electrodes were used to detect ventricular late potentials by permitting the examination of portions of the electrocardiogram otherwise obscured by noise and artifacts. Positive signal-averaged electrocardiographic (SAECG) results were based on established criteria derived from 3 time-domain variables calculated by an automated algorithm. Late potentials were detected in 151 of 242 patients (62%) and were significantly higher than controls (p = 0.0001). Radiofrequency ablation of an inducible slow conduction substrate rendered 20 of 23 positive post-ventriculotomy SAECG results negative, and surgical revision of the ventriculotomy scar rendered 19 of 19 positive SAECG results negative. In conclusion, negative SAECG results connote the absence of a reentrant substrate, and therefore, the absence of risk for reentrant monomorphic ventricular tachycardia, whereas positive SAECG results connote the presence of a slow conduction substrate and the potential risk for monomorphic ventricular tachycardia.