[Conduction of disorders after total correction of Fallot's tetralogy. Electrocardiographic and electrophysiological study].

The conduction defects observed after total correction of Fallot's tetralogy in 133 children, and their association with the long term outcome were studied with comparison of pre and postoperative electrocardiograms and, in 26 cases, His bundle recording. 23 early complete heart blocks were recorded which were nearly always transient. Only 4 (3.6%) became permanent. 58 had a right bundle branch block (48.4%) and 19 a bifascicular block (15.8%). The early operative mortality (9.7%) appeared to be related to transient complete heart block with 26% deaths in this group. Late mortality was high in patients with permanent heart block (2 out of 4) and also with bifascicular block (3 out of 17). His Bundle recordings showed lengthened H-V intervals in 3 patients, all of whom had transient complete heart block early post-operatively. In conclusion, complete heart block, even when transient, and bifascicular blocks are related to early and late mortality. The indications of permanent pacing, formal for patients with permanent complete heart block, are arguable for patients with bifascicular blocks preceded by postoperative complete heart blocks with long H-V intervals.