Automatic PVARP Feature

Automatic PVARP is an adaptive setting for the post ventricular atrial refractory period (PVARP) that varies its value based on the mean atrial rate. Automatic PVARP enhances protection against pacemaker-mediated tachycardia (PMT) by lengthening PVARP at lower tracking rates and provides a higher 2:1 block rate by shortening PVARP and SAV (if necessary) at higher rates.

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.

PVARP is nominally programmed to Auto with a programmable Minimum PVARP value, nominally 250 ms. Auto PVARP is available when the device is operating in AAI <=> DDD, AAIR <=> DDDR, DDD, DDDR, DDI and DDIR modes.

To program this feature in pacemakers and CRT-P devices, go to Params -> PVARP.

To program this feature in ICDs and CRT-D devices go to Params -> Pacing -> PVARP.

Automatic PVARP is not available in Adapta™,Versa™,Sensia™ pacemakers when:

  • the pacemaker is programmed in a non-tracking mode, such as DDI or DDIR.
  • Rate Drop Response is programmed On.
The programmable Minimum PVARP parameter value sets a limit on the shortest PVARP that is allowed. If the programmed Minimum PVARP value is reached and the Rate Adaptive AV (RAAV) parameter is programmed to On, the Sensed AV (SAV) interval is shortened to help maintain 1:1 tracking.
 
When Advisa™ pacemakers, ICDs, and CRT devices are programmed to a tracking mode, Automatic PVARP makes the adjustment based on the patient’s current heart rate as measured by the RR median interval. When the heart rate is low, PVARP is longer to prevent PMT. As the heart rate increases, PVARP shortens to maintain 1:1 tracking. Auto PVARP allows 1:1 tracking of atrial events up to 30 bpm above the heart rate or up to 100 bpm, whichever is greater.
 
Adapta™,Versa™,Sensia™ pacemakers use the mean atrial rate (MAR) to determine a value for the PVARP. The MAR is an average of all A-A intervals except those starting with an atrial sense or atrial refractory sense and ending with an atrial pace. In addition to DDD and DDDR tracking modes, automatic PVARP also functions in VDD mode in Adapta/Versa/Sensia pacemakers. The maximum adjustable 2:1 block rate is the Upper Tracking Rate plus 35 bpm. If Mode Switch is On, the maximum 2:1 block rate can be the Detect Rate if this rate is less than the value (Upper Tracking Rate plus 35 bpm) calculation.
 
Operation of Automatic PVARP in a Tracking Mode

*MAR – mean atrial rate is a running average of the atrial rate based on all A-A intervals except AS-AP or AR-AP.

In Advisa™ pacemakers, ICDs, and CRT devices programmed in a non-tracking mode (DDIR or DDI), PVARP varies with the current pacing rate to be long enough to promote AV synchrony at a low pacing rate and short enough to prevent atrial competitive pacing at a high pacing rate. The device calculates PVARP to attempt to maintain a 300 ms window of time between the end of PVARP and the next scheduled atrial pace. PVARP is limited to be no shorter than the programmed interval for the Post-Ventricular Atrial Blanking (PVAB) parameter.

Operation of Auto PVARP in a non-Tracking Mode

Consideration:

In Adapta™/Versia™/Sensia™ pacemakers:
  1. When automatic PVARP is active and Search AV+ is set to On, the pacemaker will ignore conduction times that are the result of automatic PVARP shortening of the SAV interval.
  2. If the pacemaker is in ModeSwitch, PVARP is calculated based on the sensor varied rate.

 

References

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, Evera™ DR Reference Manual.

Last updated: 
02 Dec 2016