Non-Competitive Atrial Pacing (NCAP) Feature

Non-Competitive Atrial Pacing (NCAP) is intended to prevent triggering of atrial tachycardias by delaying the scheduled atrial pace from occurring within the atrium’s relative refractory period.

This feature can be found in some Medtronic Pacemaker, ICD, CRT-P, and CRT-D devices. Please go to or consult with your local Medtronic representative regarding device models available in your geography.

NCAP is nominally programmed On and is available in DDD, DDDR, AAI<>DDD, and AAIR<>DDDR modes.

To program this feature in pacemakers, go to Params -> Additional Features.

To program this feature in ICDs, go to Pacing -> Params -> Additional Features.

Programming for pacemakers (excluding Advisa DR MRI, Revo MRI and EnRhythm)

Programming for ICDs (and Advisa DR MRI, Revo MRI and EnRhythm)

For Managed Ventricular Pacing (MVP) modes (AAI<>DDD, and AAIR<>DDDR), NCAP only functions when the mode has switched to DDD or DDDR modes.

NCAP stops delivery of an atrial pace during the atrial refractory period because pacing in this vulnerable period may lead to an atrial arrhythmia. This can happen when the device is pacing at a high rate and a premature atrial contraction occurs during an atrial refractory period, followed quickly by an atrial pace.

How NCAP affects atrial timing
When NCAP is programmed to On, a refractory sensed atrial event falling in the PVARP starts a 300 ms NCAP period, during which no atrial pacing may occur:

  • If a sensor-driven or lower rate pacing stimulus is scheduled to occur during the NCAP period, the VA interval is extended until the NCAP period expires.
  • If no pacing stimulus is scheduled to occur during the NCAP period, timing is unaffected; pacing occurs at the end of the VA interval unless inhibited.
  • An atrial refractory-sensed event occurring during the NCAP period starts a new NCAP period.

How NCAP affects ventricular timing
When an atrial pacing stimulus is delayed by the NCAP operation, the pacemaker attempts to maintain a stable ventricular rate by shortening the PAV interval that follows. It will not, however, shorten the PAV interval to less than 30 ms. When a relatively high Lower Rate and long PVARP are programmed, NCAP operation may result in ventricular pacing slightly below the Lower Rate.

Non-Competitive Atrial Pacing becomes operational in DDDR and DDD pacing modes. It maintains an interval of 400 milliseconds for one pacing cycle whenever a PVC Response or a PMT Intervention occurs. Its availability is also dependent on the following:

  • When Mode Switch is programmed On, NCAP operations are temporarily disabled if the pacemaker mode switches to the non-atrial tracking mode. The NCAP feature is re-enabled upon return to the atrial tracking mode.
  • Even when NCAP is programmed Off, the NCAP operation is invoked automatically for cycles on which PMT Intervention or PVC Response operations occur.


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.

Last updated: 
27 Mar 2013