British Heart Journal, I973, 35, 805-8 I0. Bundle of His recordings in congenital heart disease'

Bundle of His recordings were obtained from 34 children with congenital heart disease. Except for patients with endocardial cushion defect or L-transposition of the great arteries recordings were obtained by usual methods. In endocardial cushion defect it was necessary to position the electrode catheter more posteriorly, and in L-transposition of the great arteries recordings were obtained in the subaortic region. Both instances reflect anatomical variations in the conduction system previously described. The recorded atrial to His depolarization time (AH interval) and the His to ventricular depolarization time (HV interval) were normal in all patients without heart block and tended to increase with age. Two patients with complete heart block after operation were found to have block distal to the His bundle record-ing site, while in the patients with congenital complete heart block it was proximal to this site. The recording of bundle of His electrograms had been reported in the intact human heart as early as I960 when Giraud et al. (I960) reported his findings in patients with atrial septal defect. However, it had not been employed widely until Scherlag et al. described the catheter technique in I969. Since that time, the method has been extensively used in the study of AV conduction in adults (Berkowitz e