[Significance of prolonged PR interval in patients with His bundle branch block, bifascicular type].

PURPOSE

Evaluation of the prolonged PR interval and its predictive value for trifascicular block in individuals with bifascicular His bundle branch block.

PATIENTS AND METHODS

55 patients, 36 male and 19 female aged 57 + 15.8 years with bifascicular bundle branch block type have been studied. 11 cases had complete left bundle branch block and 44 cases had complete right bundle branch block with left anterior and superior division block. His bundle electrogram and atrial stimulation were performed in all patients. The atrial stimulation rate originating the Wenckebach phenomenon (SP) of the A-V conduction, and the A-H and H-V intervals were compared with the PR interval of the surface electrocardiogram. Patients were divided into three groups according to the PR interval: group I, Pr less than 200 ms, group II, PR between 190-280 ms and group III, PR greater than or equal to 280 ms.

RESULTS

There was not linear correlation between the PR interval and WP in the three groups. There was a weak linear ascending correlation between the PR and A-H intervals in groups I and II (r + 0.59 and + + 0.43, respectively) and there was a descending correlation in the group III (r. - 0.64, P less than 0.05). In relation to the H-V interval there was not linear correlation with the PR interval in groups I and II, but there was a good ascending linear correlation in the group III (r 0.84, P less than 0.01). The incidence of prolonged A-H and H-V intervals increased as the PR interval was larger.

CONCLUSION

The prolonged PR interval with bifascicular bundle branch block means, in the majority of cases, diffuse damage of the conduction system involving the A-V node and the infranodal region; starting from 280 ms, the delayed PR interval suggests involvement predominantly below the A-V node: to a higher PR interval corresponds a higher H-V interval and also, to a relatively shortest A-H interval.