[Action of chloro-acetyl-ajmaline on the electrical properties of the human heart].

The electrophysiological changes caused by the intra-atrial injection of 1.5 mg/kg of chloro-acetyl-ajmaline were studied in 23 patients by recording the His potential and by the stimulustest method. The length of the basal cycle being kept constant by atrial stimulation, measurements were made before and after the injection, on the one hand of the -VA node conduction time (A-H interval) and the infra-His conduction time (H-V interval) and on the other of the refractory periods of the right auricle, A-V node, and the His-Purkinje system. The effective refarctory period of the right ventricle was determined under pace-making of the ventricle. Finally, the variability of the sinus rate was measured. The results were as follows: 1. The sinus cycle was significantly shortened after administration of the drug (p 0.001); 2. The conduction time and refractory periods of the A-V node were not influenced by this substance; 3. The H-V interval was increased in 20 patients by an average of 11 ms (p less than 0.001). The relative refractory period of the His-Purkinje system was reduced in 4 cases out of 7 by 21 ms (p less than 0.05); the effective refractory period in one case showed a reduction of more than 45 ms. These findings will serve as a base line for assessing the anti-arrhythmic action of chloro-acetyl-ajmaline.