INCIDENCE AND PREVENTION OF VENTRICULO-ATRIAL CONDUCTION IN PATIENTS WITH COMPLETE HEART BLOCK BEFORE AND AFTER PACEMAKER IMPLANTATION

Abstract

The prevalence of retrograde VAC in patients with total atrio-ventricular block is reported to be about 15%, while it is 20-36% in second degree AV block. Among the patients with VVI pacemakers and VAC, pacemaker syndrome has been reported to occur in up to 40%.

The VAC time is primarily dependent on the site of measurement of the atrial and ventricular electrograms and the baseline autonomic tone. Retrograde conduction is dynamic, and the patients may have absent VAC during pacemaker implantation but demonstrate VAC during exercise.

During programmed electrical stimulation, retrograde VAC may occur. Many factors may affect the presence or absence of retrograde VAC.

An important hemodynamic consequence of VAC is the production of VA "dyssynchrony". In patients with intact VAC, compared to those in whom it is absent, there is a greater decrease in COP and BP as well as a greater increase in right atrial, pulmonary artery and pulmonary capillary wedge pressures during ventricular pacing.

It is evident that properly timed atrial systole has the following advantages:-

!-Maintains a low mean atrial pressure, thus facilitating venous return.