Main findings:
In this study, patients with two chamber pacemakers, ICDs and CRT
devices were evaluated for development of RNRVAS during atrial threshold
test upon loss of capture under certain predisposing CIED settings. We
demonstrated that loss of atrial capture results in RNRVAS in more than
one third of patients with a CIED in DDD mode, and in more than three
fourths of those with VA conduction. To the best of our knowledge, this
is the first study in literature demonstrating the relationship between
loss of atrial capture and systematic RNRVAS development.
Several clinically important results were revealed by this study:
1. In patients with DDD pacemakers/ICDs and CRTs, RNRVAS developed in
39% during atrial threshold test. When patients with VA conduction were
considered, RNRVAS was observed in 76.7%.
2. The presence of AV block or a high ventricular pacing ratio are
independent predictors of low RNRVAS observance.
3. VA conduction was present in 21.2% of patients with AV block 7.6%
of whom developed RNRVAS during atrial threshold test.
4. In univariate analysis, age, presence of ELT, the device being DDD
pacemaker or ICD were related to the detection of RNRVAS. However, in
multivariate analysis these parameters were not independent predictors
of RNRVAS.
5. In one patient with severe sinus node dysfunction and nodal rhythm,
loss of atrial capture was observed to trigger RNRVAS even in very low
heart rates (50-60 bpm) and caused pacemaker syndrome-like symptoms.
This finding suggests that RNRVAS may be more frequent and more easily
triggered than previously reported.
In our study, we showed that in the presence of predisposing conditions
such as long AV delay, short lower rate interval and presence of VA
conduction; RNRVAS can be triggered easily with loss of atrial capture.
This is the first study demonstrating this finding in the literature.