Premature ventricular beats: variations of periodicity and coupling interval during atrial pacing, exercise and sleep

pp 121-129

Abstract

Background

Antegrade and retrograde refractory periods and conduction times in the reentry circuit occuring during sleep and exercise test, in patients with frequent monomorphic ventricular premature beats were analized.

Methods and results

In 32 patients with frequent monomorphic ventricular premature beats the antegrade and retrograde refractory periods and conduction time, and their modifications during exercise testing and sleep were evaluated. The antegrade refractory period was determined by the minimum postextrasystolic interval that turns bigeminy into type I trigeminy; the retrograde refractory period by the maximum postextrasystolic interval that converts bigeminy into type II trigeminy and the conduction time changes were evaluated through the modifications ofpremature beats coupling interval during bigeminy.These data were compared with control values obtainedduring atrial pacing. The statistical analysis was per-formed using the Student's test for paired data. During the exercise test, both refractory periods shortened: the antegrade one between 4to 56% in 14 patients, p<0.05; the retrograde changed from 16 to 60% in 26cases, p < 0.05; and the conduction time decresed between 2.5 and 22% in 20. During sleep both refractory periods increased: the antegrade between 7-38%in 21 cases, p<0.05, and the retrograde between 2 to139% in21 patients, p<0.05; the conduction time increased between2-23%in 18. Although conversion of bigeminy into type I and II trigeminy was not obtained in every case during the exercise test and sleep, a shortening of both refractory periods and the conduction time during exercise was observed. In contrast, during sleep there was a prolongation of the refractory periods and conduction time.

Conclusions

Modifications of the autonomic tone may be responsible for these changes, with sympathetic predominance during daytime and a parasympathetic predominance during sleeping. These findings could be related to circadian arrhythmias variations and to the incidence of sudden cardiac death.