BIOTRONIK Evia HF - Timing Features; Refractory Periods; Atrial Refractory Period; Pvarp

Chapter 5 Programmable Parameters
Evia HF / HF-T Technical Manual
PAGE 29
5.5 Timing Features
Features related to pulse generator timing cycles.
5.5.1 Refractory Periods
Immediately upon sensing or pacing, the pulse generator starts a refractory period in the same channel.
During the refractory period, intracardiac signals are ignored. This prevents the pulse generator from
responding to the depolarization signal or the repolarization signal (T-wave) that might otherwise result
in inappropriate inhibition or triggering.
If the pulse generator is programmed to dual chamber sensing, the refractory periods are independently
programmable for each sensing channel. There are two refractory periods in the atrium:
• Regular atrial refractory period, which is automatically adjusted by the Auto Aref functionality
• PVARP is started with each ventricular pace outside of the AV delay. In DDI mode, PVARP is also
started with a regular ventricular sense or
• PVARP after PVC is started after a premature ventricular sensed event (PVC)
CAUTION
Short Pacing Intervals Use of short pacing intervals (high pacing
rates) with long atrial and/or ventricular refractory periods may
result in intermittent asynchronous pacing and, therefore, may be
contraindicated in some patients.
5.5.2 Atrial Refractory Period
The atrial refractory period is set by default to Auto. This means the atrial refractory period is equal
to 225 ms, which is automatically extended if the AV Delay is programmed longer than 225 ms to the
programmed AV Delay value.
5.5.3 PVARP
The Post Ventricular Atrial Refractory Period (PVARP) is a function in the pacemaker to help prevent
Pacemaker Mediated Tachycardia (PMT), by preventing false classication of a retrograde conduction
as an atrial event.
There are 2 different behavior modes of PVARP based on programmed mode, which is
described below.
• In P-synchronous modes(e.g. DDD), the PVARP timer is started after : Vp, Vp(WKB),
Vp(SW), Vp(BU)
• In R-synchronous modes (e.g. DDI), the PVARP timer is started after: Vp, PVC, VS.
• After a VES, the parameter PVARP after PVC is automatically extended to PVARP + 150ms, up to
a maximum of the user programmable “PMT VA Criterion limit” + 50 ms. This parameter was
formerly known as PMT protection after PVC.
This behavior is shown in Figure 15.