Incessant PMT

Tracing
N° 14
Manufacturer Biotronik Device PM Field Refractory periods
Patient

81-year-old man implanted with an Evia DR-T pacemaker for sinus dysfunction; hospitalization for cardiac decompensation; recording of this EGM tracing on arrival.

 

Graph and trace

Tracing 14a

  1. permanent tachycardia at the programmed maximum rate (120 bpm) with succession of AS-VP cycles;

Tracing 14b

The PMT termination algorithm had been deprogrammed. Programming of this algorithm and recording of this EGM;

  1. new PMT;
  2. operation of the algorithm with confirmation phase; prolongation of the AV delay for one cycle (+ 50 ms);
  3. retrograde conduction time remains constant confirming the PMT;
  4. prolonging of the PVARP over one cycle (programmed VA criterion + 50 ms);
  5. PMT termination and atrial pacing; inefficient pacing since occurring during the refractory period of the atrial myocardium;
  6. this inefficient pacing favors retrograde conduction and the resumption of PMT;
  7. the sequence repeats itself.
Comments

These tracings illustrate 2 causes of incessant PMT. On the first tracing, the PMT detection and termination algorithm was deprogrammed, thus explaining the persisting tachycardia. On the second tracing, the algorithm was reprogrammed, the device diagnoses the PMT, terminates it efficiently although the PMT immediately resumes. Indeed, atrial pacing occurs in the myocardial refractory period and is therefore ineffective and favors the occurrence of retrograde conduction. In this patient, it is necessary to diagnose the initial triggering mechanism of the PMT. Consideration should also be given to programming a PVARP that is longer than the retrograde conduction time, even if it appears relatively long (in the order of 400 ms) and that such prolongation may limit 1:1 tracking upon exertion. However, the exercise capacity of this 81-year-old patient is considerably reduced.

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