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90 Stratos LV/LV-T Technical Manual
To prevent occurrence of a PMT, Stratos CRT-Ps start an atrial
PMT protection interval after each ventricular paced event (right
or left). If an atrial even is sensed within this PMT protection
interval, this will neither start an AV delay nor a basic interval.
The length of the PMT protection can be set to automatic (Auto).
In this case, the PMT protection window can be automatically
extended after the PMT is detected and terminated.
NOTE:
The initial values of the PMT protection interval in the
automatic setting at 175 ms after a Vp, and 400 ms after
VES.
2.9.2 PMT Detection
It is the objective of PMT detection to identify ongoing PMTs, to
distinguish them from the sinus rhythm and to terminate them.
The detection of a PMT starts by measuring the Vp-As intervals.
If these lie below the programmable PMT VA criterion
(programming depends on the retrograde conduction time of the
patient), the measurement of the stability of the Vp-As interval is
started.
The Stratos CRT-P’s PMT detection/termination algorithm
consists of suspicion, confirmation and termination components
and is described as follows.
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 with
respect to upper and lower values is ±25 ms.