Pacemaker Tachycardia: Is it Pacemaker‐Mediated Tachycardia or Sinus Tachycardia?

Abstract

A 38-year-old woman received a transvenous St. Jude Atlas + HF V-340 biventricular implantable cardioverter defibrillator (ICD; Sylmar, CA, USA) for a nonischemic dilated cardiomyopathy associated with drug-refractory congestive heart failure, left bundle branch block, and a left ventricular ejection fraction of 20%. About a year later she was referred to our center for the first time after sustaining 2 shocks related to supraventricular tachycardia at a rate of 210 bpm, which was documented in stored electrograms. There was no evidence of congestive heart failure. Upon interrogation of the device, we retrieved only one memorized episode labeled as a pacemaker-mediated tachycardia (PMT). The programmed parameters were as follows: Base rate = 70 ppm, maximum tracking rate = 140 ppm, Atrial pacing-ventricular pacing/atrial sensing-ventricular pacing (AV/PV) delay = 120/90 ms (A = atrial paced event, V = ventricular paced event, P = atrial sensed event), PMT option = A Pace on PMT (detection rate = 100 bpm), and a rate-responsive postventricular atrial refractory period. Ventricular fibrillation detection interval = 280 ms for 12 intervals but ventricular tachycardia was turned off. Testing the device revealed normal pacing, sensing, high and low voltage impedances, and battery function. Did the device make the correct diagnosis of PMT in the stored electrograms shown in Fig. 1? DiscussionThe St. Jude algorithm uses modulation of the AV (PV) delay for one cardiac cycle regardless of the pacing rate to detect PMT. 1-3 The pacemaker identifies PMT if the same ventricular paced event (V) gives rise to a stable unchanged ventricular pacing (VP) interval because in PMT the retrograde ventriculoatrial conduction almost always remains constant. In a supraventricular tachycardia (SVT) or sinus tachycardia the change of the AV delay will alter the VP interval to the same degree. When the atrial rate becomes equal to or exceeds the programmed PMT detection rate for 8 consec-Address for reprints: S. utive PV cycles with VP variation not greater than 16 ms, the device modifies the PV interval by 31 ms. If the previous PV interval was ≥100 ms, the PV interval is shortened by 31 ms. If the previous PV was <100 ms, the PV is lengthened by 31 ms. Then, the device compares the new or modified VP interval with the average VP interval before the single altered PV interval AV delay. If the VP interval remains within 16 ms of the average VP interval, the device makes the diagnosis of PMT. When the PMT algorithm is set to A (Atrial) Pace on PMT, the pulse generator withholds a ventricular output and releases an atrial output pulse 330 ms after the detected P wave in an attempt to terminate the PMT. The atrial pulse is inhibited if a P wave or an R wave is detected during the 330 ms window before the scheduled atrial stimulus.In Fig. 1 the VP intervals can be calculated from the annotated data showing atrial and ventricular intervals. The VP interval becomes equal to the interventricular (VV) interval minus the AV delay (PV interval), whi...

Device Diagnosis of Pacemaker‐Mediated Tachycardia: True or False?

“…The mathematical constraints of the traditional PMT detection algorithm make a false positive response of a PMT highly unlikely. However, rare cases of sinus tachycardia have been reported to activate the PMT termination algorithm . In the present case, the episodes of Wenckebach upper rate behavior ruled out the clinical diagnosis of PMT.…”

Unusual Manifestation of Upper Rate Limitation in a Dual‐Chamber ICD

“…However, rare cases of sinus tachycardia have been reported to activate the PMT termination algorithm. 2,3 Figures 2A and B show a PMT in a patient with a St. Jude Promote implantable cardioverterdefibrillator (ICD). 1 At the time of follow-up, stored data revealed a PMT that was terminated automatically by the PMT-terminating algorithm but the test AV delay lengthened by about 50 ms.…”