Journal of Atrial Fibrillation – Journal of Atrial Fibrillation & Electrophysiology (JAFIB-EP)

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Questions : What is happening in this EGM?


This is an example of a PMT episode that is successfully terminated with the algorithm AP on PMT (Abbott). The PMT detection rate is 120bpm.

The device detected eight consecutive VP-AS intervals with a rate higher than the PMT detection rate (appx. 120), the device then calculated the stability of the eight VP-AS intervals.

The device averages eight VP-AS intervals and compares that average to each of the individual intervals.

In this example, all VP-AS intervals are within 16 ms of the average, therefore considered stable. When the VP-AS are considered stable, the device modifies the AV delay for the ninth interval to confirm the diagnosis of PMT. If one of the eight intervals varied by >16 ms from the average, the VP-AS intervals are considered unstable and the next eight beats are monitored.

  • The sensed AV delay is shortened by 50 ms if the programmed Sensed AV (AS-VP) interval is ≥100 ms.

  • The sensed AV delay is lengthened by 50 ms if the programmed Sensed AV (AS-VP) interval is <100 ms.

The next VP-AS interval is then analyzed. If the VP-AS is unchanged, the P-wave is considered retrograde with suspicion of PMT, (as shown in this example)

  • If the e next VP-AS was different than >16ms, the P wave is not considered retrograde (no PMT). The algorithm may be repeated after 256 beats.

PMT was suspected, therefore the next ventricular pulse (10th cycle) is inhibited.

An atrial pulse is delivered 330 ms after the detected retrograde P wave.

The atrial pulse is followed by ventricular pacing at the end of the AV delay if needed.

The atrial pulse is inhibited if a P wave is sensed (AS) within a 210 ms alert period following the absolute atrial refractory period.

The AP on PMT treatment algorithm was successful, and normal AP with conduction followed.