[Interventricular communication, aneurysm of the membranous septum and acquired atrioventricular block].

Over a ten year period of a man 40 had a progressively increasing atrioventricular conduction defect, resulting from a ventricular septal defect with eventual cardlac failure due to persistant bradycardia. Intracavitary recordings showed the block to be situated distally, below the bundle of His. Cineaarteriography, and subsequent operation, showed an aneurysm of the membranous septum lying above a fibrous-edged ventricular septal defect. The aetiology of the block is discussed in the light of these defects; Haemodynamic trauma to the conduction pathways exposed in the inferior edge of the septal defect seems to be the most likely cause.