RNRVAS, AHRE, Atrial overdrive pacing
The study of Kohno et al 7 evaluated AHRE
recordings for diagnosis of atrial tachyarrhythmias. Our results support
their findings. They studied 39 patients with St. Jude DDD pacemakers
for 16.7 ± 9.8 months. In half of the patients, atrial overdrive pace
(AOP) algorithm was turned on and the patients were followed. AHRE was
observed in 20 of 39 patients (51%) and among these 257 AHRE, 148 were
AF and 109 were RNRVAS. There was a total of 257 AHRE attacks amongst
51% of the 39 patients, where 148 of the attacks were AF and 109 were
RNRVAS. In this study, patients with RNRVAS or RNRVAS and AF were all in
the group assigned to AOP “ON” (P = .0020). In all the patients
that developed RNRVAS, atrial pacing ratio was significantly higher
(92.2% vs. 49.9%, P < .0001).
In our study, atrial pacing ratio was significantly higher in the
subgroup of patients with pacemakers (P = .030) compared to
patients with patients with ICDs, although this was not statistically
significant in the whole study population (P = .928). The reason
for the atrial pacing ratio being lower in our study may be because
patients with ICDs and CRTs were also included. Both in the ASSERT sub
study 14, and the study by Kohno et al7, RNRVAS was four times more frequent in patients
with AOP turned on.
In general practice, in case of atrial premature beats, AOP is activated
to prevent induction of atrial fibrillation. If some atrial premature
beats are not sensed during AOP, then loss of atrial capture may be seen
resulting in RNRVAS in presence of VA conduction.
In ASSERT study3, which included 2343 patients with
DDD pacemakers, erroneous AHRE recordings were numerous mostly due to
the presence of RNRVAS (13.9%). These data prove RNRVAS is under
reported and in fact more frequently encountered than currently
estimated. In ASSERT study, all the pacemakers were of St Jude Medical
and atrial arrhythmia recognition algorithms of St Jude Medical devices
are thought to be more sensitive in recognizing RNRVAS3,11,15. In St Jude Medical devices, AHRE algorithms
use both sensed and paced atrial signal for recognition, therefore
RNRVAS attacks are recorded as AHRE 11. The actual
incidence of RNRVAS is unknown due to the absence of specific algorithms
for recognizing RNRVAS in CIEDs. However, in the patient who experiences
RNRVAS at low heart rates, like in the case of our patient (Figure 5),
SJM algorithms are unable to diagnose the problem.