Figure 74. Example of pacing at the 2:1 block rate
A
S
A
S
A
S
V
P
V
P
V
P
200 ms
A
R
A
R
A
R
ECG
Marker Channel
AV interval
PVARP
Lower Rate interval
1 One of every 2 atrial sensed events occurs during PVARP and is not tracked.
In some cases, the amount of rate drop is less severe because of pacing at the sensor rate
(in the DDDR mode) or because of various rate stabilization, smoothing, or overdrive pacing
features.
A common method to prevent 2:1 block at elevated exercise rates (for example, above
150 bpm) is to program shorter than nominal values for SAV and PVARP. Use of the Rate
Adaptive AV and Auto PVARP features dynamically shortens the operating SAV and
PVARP values during exercise. For more information about PVARP, see Section 7.7,
“Adjusting PVARP to changes in the patient’s heart rate”, page 253. These features can
prevent symptomatic 2:1 block during exercise while allowing nominal or longer SAV and
PVARP values at resting rates to help prevent rapid ventricular pacing rates during the onset
of AT/AF.
When programming the SAV or PVARP parameters, the programmer calculates and
displays the 2:1 block rate. When the 2:1 block rate is dynamic due to the Rate Adaptive
AV or Auto PVARP features, the programmer displays 2:1 block rates at both rest and
exercise.
7.2.8.2 Upper Tracking Rate
The programmable Upper Tracking Rate also places a limit on the fastest ventricular pacing
rate during atrial tracking. Typically, the Upper Tracking Rate is programmed to a rate that
is below the exercise 2:1 block rate. If not, the 2:1 block rate becomes the absolute limit and
the Upper Tracking Rate cannot be achieved.
Medtronic
PROTECTA™ XT DR D314DRG
Clinician Manual
221
Содержание PROTECTA XT DR D314DRG
Страница 2: ......
Страница 9: ...Index 488 Medtronic PROTECTA XT DR D314DRG Clinician Manual 9 ...
Страница 506: ......
Страница 507: ......