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.