Atrial threshold test
In order to demonstrate that loss of atrial capture may trigger RNRVAS,
a specific atrial threshold test was designed. Atrial threshold test was
done in DDD mode at a rate at least 10 beats above the basal heart rate
(maximum 80 - 100 bpm), with an AV delay of 300 ms (range 250 - 350) in
all but LivaNova - Sorin devices, which were set to DAO mode as the
closest possible setting. The pace amplitude was decreased every 4 to 10
beats, while the pulse width was kept constant in all devices.
The PVARP settings of the patients were not changed during atrial
threshold tests. Only in case of PMT induction during atrial threshold
test, PVARP duration was increased.
Upon the loss of atrial capture, the EGM recordings were examined for
appearance and duration of RNRVAS as explained below. Loss of atrial
capture was confirmed with loss of P waves on surface ECG or loss of
atrial signal after pace stimulus on ECM as recorded by the programmer
device. In case of development of ELT with loss of atrial capture, PVARP
was lengthened, and test was repeated.