Atrial Preference Pacing (APP) Feature
Atrial Preference Pacing (APP) is designed to maximize atrial pacing percentage to reduce the incidence of atrial tachyarrhythmias. When enabled, it can be programmed to provide continuous pacing that slightly exceeds the intrinsic sinus rate whenever the patient is not in an atrial tachyarrhythmia.
This feature can be found in some Medtronic Pacemaker, ICD, and CRT-D devices. Please go to manuals.medtronic.com or consult with your local Medtronic representative regarding device models available in your geography.
Atrial Preference Pacing is nominally Off and is operational when the device is operating in the DDDR, DDD, AAIR, or AAI modes.
Additional programming parameters include (nominal settings are shown in image below):
- Maximum Rate – Sets a maximum rate for Atrial Preference Pacing.
- Interval Decrement – In response to an atrial sensed event, the atrial pacing interval decreases by this value, per beat, to accelerate the pacing rate.
- Search Beats – After this number of consecutive paces, the atrial rate decelerates in search of sinus activation.
To program this feature in pacemakers, go to Params -> Arrhythmia Interventions.
To program this feature in ICDs, go to Pacing -> Params -> Arrhythmia/Post Shock...
Note: This screen may appear slightly different depending on the device.
When APP is enabled, the device tends to provide a higher ratio of paced to sensed events, which may decrease the service life of the device.
APP responds to changes in the atrial rate by accelerating the pacing rate until it reaches a steady paced rhythm that is slightly faster than the intrinsic rate, up to a programmed maximum rate.
After each nonrefractory atrial sensed event, the device decreases the atrial pacing interval by the programmed Interval Decrement value. Beats continue at this elevated rate until the pacing rate exceeds the intrinsic rate, resulting in an atrial paced rhythm.
The increased rate is sustained for the number of beats programmed as the Search Beats parameter. APP then decreases the pacing rate slightly (by 20 milliseconds; nonprogrammable) to search for the next intrinsic beat. This results in a dynamic, controlled, stairstep increase or decrease in the pacing interval, maintaining a pacing rate slightly above the intrinsic rate.
This diagram illustrates the operation of Atrial Preference Pacing (APP):
- Annotated on Marker Channel™ with Proactive Pace (PP).
- APP is suspended during Mode Switch (including PMOP) during detected tachyarrhythmia episodes.
- The Non-Competitive Atrial Pacing (NCAP) feature may delay an atrial pace that results from APP.
- APP will not increase the pacing rate if an atrial sense occurs during either Atrial CaptureManagement™ or Ventricular Capture Management.
The diagram below displays an example of APP in action:
Interval 1: Measure AS to AS = 1000 ms.
Interval 2: Calculate: Pacing Escape Interval = (AS-AS) – Interval Decrement; i.e. 1000 ms – 30 ms (nominal) = 970 ms. Note: an AS occurs at 960 ms, so the pacing escape is inhibited.
Interval 3: Subtract another 30 ms from previous pacing interval = 940 ms. AP occurs.
Interval 4 – 23: AP occurs at the atrial escape interval of 940 ms.
Interval 24: Search beats are reached so a new atrial escape interval is calculated by adding 20 ms. (940 ms + 20 ms = 960 ms).
Interval N: This process is continued until:
- The pacing rate reaches the lower rate.
- The pacing rate reaches the sensor-indicated rate.
- Pacing is interrupted by intrinsic atrial activity.
Sources: Medtronic Adapta™/Versa™/Sensia™ Reference Guide; Medtronic Protecta™ XT DR Clinician Manual;Medtronic Protecta™ XT CRT-D Clinician Manual.