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.