BIOTRONIK Evia DR, Technical Manual

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86 Evia Technical Manual
Suspicion
A PMT is suspected when two criteria are met:
•
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.
Confirmation
When the suspicion criterion has been met, the Evia slightly
modifies the AV delay interval (+ or - 50 ms) or the upper
tracking rate (+50ms) for one cardiac cycle. If the Vp-As interval
remains stable, a PMT is confirmed. Otherwise, a PMT is not
confirmed and the algorithm restarts. Once the PMT algorithm
has confirmed a PMT, the cycle is broken as follows:
Termination
Evia extends PVARP (Post Ventricular Atrial Refractory Period)
to the VA in 50 ms
7.12 Adjustment of the PMT Protection
Window
The PMT protection window can be automatically adjusted. This
automatic adjustment functions in the following manner:
When the PMT is detected and terminated, the PMT protection
interval is extended by 50 ms. If no additional PMTs arise within
seven days, the length of the PMT protection interval is reduced
by 50 ms. The initial values of the PMT protection interval in the
automatic setting at 250 ms after Vp and 400 ms after a PVC.