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).