Intracardiac conduction intervals in children with congenital heart disease: comparison of His bundle studies in 41 normal children and 307 patients with congenital cardiac defects.

His bundle electrograms were recorded in 348 patients aged 2 months to 24 years following routine diagnostic cardiac catheterization. Among 41 children found to be free of anatomic or hemodynamic abnormality the following mean values were obtained: P-H interval, 93.4 +/- 15.3 msec; P-A time, 21.2 +/- 7.1 msec; A-H interval, 72.2 +/- 15.9 msec; and H-V interval, 39.8 +/- 5.2 msec. The remaining 307 patients were analyzed by diagnosis of congenital heart disease. The mean P-H interval was found to be significantly increased in both ostium primum and secundum atrial septal defect (ASD) with A-H prolongation in primum ASD and P-A prolongation in secundum ASD. The mean H-V interval was significantly prolonged in ostium primum ASD and in patients with severe aortic stenosis, aortic insufficiency. and mitral regurgitation. Grouping of the patients physiologically revealed that patients with moderate-to-severe right ventricular volume overload had P-H prolongation, and patients with severe left ventricular volume or pressure overload had H-V prolongation. The clinical implications of these findings are discussed.