RNRVAS
When all patients were analyzed, the incidence of RNRVAS was 39%. However, if we consider the patients with only VA conduction, then the incidence of RNRVAS increases to 76.7% (69 of 90 patients). Out of 66 patients that displayed AV block, 5 of them developed RNRVAS (7.6), however this percentage went up to 35.7% (5 of 14 patients) in the presence of VA conduction. The RNRVAS incidence was 84.2% (64 of 76 patients) in patients who had VA conduction in the absence of AV block.
In 66 of the 69 patients with RNRVAS, the cycle ended when heart rate decreased at the end of the atrial threshold test (Figure 2 A-D). In 3 patients, RNRVAS converted to ELT after the atrial threshold test ended. (Figure 3).
One patient who was implanted a DDD pacemaker 17 months ago, for severe sinus node dysfunction, was found to be in RNRVAS at a heart rate of 60 bpm (Figure 4) and presented with pacemaker syndrome-like symptoms. When the device was interrogated, atrial pacing threshold was found to be increased to 2.5 V/0.4 s. As the atrial pace amplitude was previously set to 2.5 V/0.4 sec, increased atrial threshold resulted in intermittent loss of atrial capture leading to RNRVAS at a low heart rate (50 bpm) (Figure 5 A, B).
In the multivariate analysis, history of complete AV block (OR 0.15, 0.03 - 0.61; 95%CI, P = .009) and ventricular pacing ratio (OR 0.98, 0.96 - 0.99; 95%CI, P = .029) appeared as independent factors indicating lower risk of RNRVAS development (Table 2).