Device algorithms to prevent RNRVAS

Accessed under parameters; additional feature; non-comp atrial pacing

•Non-comp atrial pacing  on  off

•NCAP interval  300ms

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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

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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.

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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.

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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.

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Considerations

•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.

•When a relatively high Lower Rate and long PVARP are programmed, NCAP operation may result in ventricular pacing slightly below the Lower Rate.