[Atrioventricular conduction in the Lown-Ganong-Levine syndrome].

In 18 patients with LGL-syndrome His bundle electrography and atrial pacing were performed. In all cases the atrial conduction time was normal, the H-V interval within the lower limit (36 msec). The A-H interval was significantly shortened (58 msec). During rapid atrial pacing four different patterns of reaction could be distinguished: 1) A-H interval unchanged (1 case). 2) Sudden prolongation of the A-H interval at a critical rate (4 cases). 3) Continuous prolongation of the A-H time according to the driving frequency (9 cases). 4) Marked delay and block (4 cases). Verapamil had only little or no effect on the A-H interval in these patients. The results indicate, that only in a few cases with LGL-syndrome the shortened A-H time is due to a James bundle bypassing completely the A-V node.