Medtronic PROTECTA XT DR D314DRG, Руководство для клиницистов

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1:1 atrial tracking can occur for sinus rates at or below the programmed Upper Tracking
Rate. As the sinus rate increases beyond the Upper Tracking Rate, the ventricular pacing
rate remains at the Upper Tracking Rate, and the observed SAV interval (AS-VP interval)
lengthens with each subsequent pacing cycle. Eventually, after several pacing cycles, an
atrial sensed event occurs during PVARP and is not tracked, resulting in a dropped beat.
This pattern repeats itself as long as the sinus rate remains above the programmed Upper
Tracking Rate. The dropped beat occurs less often when the sinus rate is only slightly above
the Upper Tracking Rate (for example, every 7 or 8 beats) and more often as the sinus rate
exceeds the Upper Tracking Rate by larger amounts (for example, every 3 or 4 beats).
This Upper Tracking Rate behavior is known as pacemaker Wenckebach (see Figure 75).
Wenckebach behavior can be further defined by how often the dropped beat occurs,
typically as a ratio of the number of atrial sensed events compared to ventricular paced
events (for example, 8:7, 7:6, 6:5, or 3:2). Further increases in the atrial rate may eventually
reach the 2:1 block rate where the ratio becomes 2:1.
Figure 75. Example of Wenckebach pacing
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200 ms
SAV SAV SAV SAV SAV SAV
ECG
Marker Channel
AV interval
PVARP
Upper Tracking Rate
interval
1 SAV intervals extend so that ventricular paced events do not violate the Upper Tracking Rate.
2 An atrial event occurs during PVARP and is not tracked.
3 Tracking resumes on subsequent atrial events.
To provide proper tachyarrhythmia detection, the programmer forces the various
tachyarrhythmia detection rates to be programmed above the programmed Upper Tracking
Rate and prevents long blanking periods from being programmed along with high Upper
Tracking Rate values.
Medtronic PROTECTA™ XT DR D314DRG
222 Clinician Manual