[Evaluation of the response to the ajmaline test in the diagnosis of paroxysmal atrioventricular blocks].

Between October 1973 and December 1981, 31 symptomatic patients who underwent pacemaker therapy on the results of a positive Ajmaline test alone, showing infrahisian AV block, were followed up clinically and electrocardiographically. The mean follow up from the date of implantation was 30 months. Two groups of patients were identified according to the results of electrophysiological investigations and clinical and electrocardiographic follow-up: --group I: 13 patients with either infrahisian AV block or an HV interval greater than or equal to 120 ms after Ajmaline; --group II: 18 patients with an HV interval less than 120 ms after Ajmaline. During follow-up, the 5 AV blocks observed out of the 7 documented at inhibition of the pacemaker and the only two cases of deterioration of the intraventricular conduction during sinus rhythm occurred in Group I. The only discriminating variable between the two groups before the implantation of a pacemaker was the response to the Ajmaline test. The difference of the results of the electrical outcome between the two groups was statistically significant (p less than 0,03). During the same study period this critical value was observed in 49 other patients with a basal HV greater than or equal to 70 ms. In this group, 20 developed infrahisian AV block after Ajmaline, 26 had a HV interval greater than or equal to 120 ms and only 3 cases had HV intervals of 100 ms. These results suggest that a HV interval greater than or equal to 120 ms after Ajmaline has the same significance as infrahisian block produced by the drug.