The mechanism of RNRVAS and predisposing factors
RNRVAS was first described by Serge Barold in 19911.
Several studies showed that in two chamber devices, long AV delay, long
PVARP, short lower rate interval, presence of VA conduction and long VA
conduction periods were predisposing factors of RNRVAS1,2,11. A few studies described ventricular ectopic
beats and retrograde atrial conduction after ventricular pacing as a
trigger mechanism for RNRVAS1,8. Andric et aldescribed a patient with DDD Pacemaker implanted for AV block after
mitral valve replacement 12. The patient was admitted
for decompensated heart failure caused by ELT and RNRVAS with increased
atrial threshold. In this case report, the induction of RNRVAS due to
increased atrial threshold was not demonstrated, but was suggested as
the possible cause. There are no other cases in literature with evidence
showing the relationship between increased atrial threshold and RNRVAS.
In this study, we show that the absence of VA conduction accompanied by
presence of AV block decreases the risk of RNRVAS development in both
univariate and multivariate analyses.
VA conduction is mandatory for development of RNRVAS and AV block is
frequently accompanied by VA block. We showed that only 21.2% of the
patients with AV block had VA conduction. This number is consistent with
the findings of Richter et al 13.
The absence of VA conduction in the remaining 78.8% explains why
patients with AV block experience RNRVAS less. Av block results in
increased ventricular pacing ratio which was an independent predictor of
absence of RNRVAS development in univariate and multivariate analyses in
this study.