BIOTRONIK Evia HF - PMT Detection and Termination

Chapter 5 Programmable Parameters
Evia HF / HF-T Technical Manual
PAGE 47
To prevent occurrence of a PMT, Evia CRT-Ps start an atrial PMT protection interval after each
ventricular paced event. If an atrial event is sensed within this PMT protection interval, this will neither
start an AV delay nor a basic interval.
PMT Protection is an On/Off feature and is found on the Refractory Period / Blanking Screen. However,
it can only be programmed OFF when Auto PVARP is programmed OFF. Once activated, the VA
Criterion, nominally set to 350 ms, is programmable from 250...(10)...500 ms.
NOTE:
The initial values of the PMT protection interval in the automatic setting at 250 ms after a Vp, and 400
ms after PVC.
5.11.2.1 PMT Detection and Termination
In addition to PMT prevention, Evia CRT-P contains a programmable PMT detection and termination
algorithm. The termination feature will take action in case the prevention was not effective and a PMT is
detected. The PMT detection constantly monitors for the presence of a PMT.
The Evia CRT-P PMT detection/termination algorithm consists of suspicion, conrmation and
termination components and is described as follows.
Suspicion
A PMT is suspected when the following criteria are met:
• The heart rate is greater than 100 bpm.
• 8 successive V pace-A sense (Vp-As) sequences have occurred with a length shorter than the VA
criterion. This VA criterion is programmable between 250 and 500 ms.
• The mean deviation of these 8 Vp-As intervals is less than the Stability criterion parameter, defined
as less than 25 ms.
Conrmation
In order to conrm PMT, one of two actions is taken:
• If the suspected PMT is occurring at the Upper Tracking Interval (UTI), which occurs in most cases,
the UTI is increased to the next programmable length by 50 ms.
• If the suspected PMT is occurring at a rate that is slower than the UTI, the programmed AV Delay
is shortened to the next programmable length by 50 ms.
In either case, if the measured VA interval remains constant, PMT is conrmed, moving the algorithm to
the next phase, PMT Termination.
Interval Length AV Delay Test Method:
Atrial Tracked Rate Interval AV Delay Test Method
> UTI ≤ 200 ms Increase AV Delay by 50 ms
> UTI + 50 ms > 200 ms Decrease AV Delay by 50 ms
≤ UTI Any Increase UTI by 50 ms
> UTI and ≤ UTI + 50 ms > 200 ms
Set UTI = Atrial Tracked
Rate Interval + 50 ms