Atrial Rate Stabilization (ARS) Feature
Atrial Rate Stabilization (ARS) is a programmable feature designed to prevent the long sinus pause that commonly follows a premature atrial contraction (PAC).
This feature can be found in some Medtronic Pacemaker, ICD, CRT-P, and CRT-D devices. Please go to manuals.medtronic.com or consult with your local Medtronic representative regarding device models available in your geography.
ARS is nominally Off and is operational when the device is operating in the DDDR, DDD, AAIR, or AAI mode.
Additional programming parameters include (nominal settings are shown in image below):
- Maximum Rate – Sets a minimum limit on the pacing interval controlled by this feature.
- Interval Percentage Increment – The pacing interval increment per beat, as a percentage of the preceding interval.
To program this feature in pacemakers/CRT-P devices, go to Params -> Arrhythmia Interventions.
To program this feature in ICDs/CRT-D devices, go to Params -> Pacing -> Arrhythmia/Post Shock.
- To ensure reliable tachyarrhythmia detection, the system regulates the values that you can select for the Maximum Rate, Upper Rate, AT/AF Detection Interval, and Ventricular Monitor interval.
- Atrial Rate Stabilization and Rate Hysteresis cannot be enabled at the same time.
- ARS must be Off if the atrial sensing polarity is unipolar or if Lead Monitor is set to Adaptive for the atrial lead.
When ARS is enabled, at each atrial event (AS event, AP event, or pertinent AR event*), the device calculates a new pacing interval, which is equal to the current pacing interval increased by the Interval Percentage Increment.
If the current pacing interval ends before the device senses an atrial event, the device delivers an atrial pace and recalculates its interval using the current atrial interval. The current pacing interval will be the shorter of the sensor rate interval or the calculated interval. The programmed Maximum Rate value provides a rate limit for operation of the feature. After a PAC, the calculated escape interval stabilizes the atrial rate and gradually slows it to the intrinsic rate, sensor-indicated rate, or programmed Lower Rate (whichever is attained first). The following diagram illustrates ARS operation. ARS pacing begins when a premature beat occurs, and ends when the sensor rate or lower rate is reached.
This algorithm is suspended during Mode Switch or during the detection of an arrhythmia. If this algorithm and Atrial Preference Pacing (and Ventricular Rate Stabilization) are enabled, the most aggressive algorithm (shortest escape interval) is used for each atrial cycle. The Non-Competitive Atrial Pacing (NCAP) feature may delay an atrial pacing pulse that results from Atrial Rate Stabilization.
Marker Channel annotation: Atrial pacing pulses that are delivered under Atrial Preference Pacing or Atrial Rate Stabilization operation are annotated on the Marker Channel with PP (proactive pace) rather than AP.
- Pacing occurs at the programmed escape interval.
- The premature beat initiates a shorter escape interval. This interval ends with a programmed pace, which is determined by the maximum rate.
- The device uses this atrial interval to calculate the next escape level.
- This atrial interval is 25% longer than the preceding one. It ends with the second programmed pace.
- When the calculated pacing interval exceeds the programmed escape interval, normal pacing resumes.
Sources: Medtronic Adapta™/Versa™/Sensia™ Reference Guide; Medtronic Consulta™ CRT-P Clinician Manual;Medtronic Protecta™ XT DR Clinician Manual; Medtronic Protecta™ XT CRT-D Clinician Manual.