Pacemaker mediated tachycardia

Fig. 3.23 Pacemaker mediated tachycardia (PMT). In this case, a premature ventricular contraction (second QRS complex) leads to retrograde ventriculo-atrial (VA) conduction. The atrial activity occurs after the PVARP has expired, is sensed, and leads to ventricular pacing, which again is associated with VA conduction. An incessant tachycardia can be initiated and sustained in this way.

Pacemaker-mediated tachycardia arises from retrograde conduction via the normal conduction system of the heart of a paced or intrinsic ventricniar event to the atrium. The tracking of the retrogradely conducted atrial complex must occur for PMT to occur. The successive ventricular-paced event that tracks this atrial complex also results in retrograde conduction to the atrinm. 

Levine PA, Postventricular atrial refractory periods and pacemaker mediated tachycardias, Clin Prog Pacing Electrophysiol 1983 1 394-401. 

Levine PA, Selznick L, Prospective management of the patient with retrograde ventriculo-atrial conduction, prevention and management of pacemaker mediated endless loop tachycardias. Syhnar, CA, Pacesetter, Inc., 1990. 

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