Pin-port misconnection induced endless loop tachycardia.

Whereas a pacemaker‐mediated tachycardia (PMT), technically, could be a period of rapid ventricular pacing while tracking an intrinsic atrial tachyarrhythmia such as atrial fibrillation or atrial flutter, the usual PMT is associated with “retrograde conduction” from the ventricular paced beat to the atrium where the P wave is sensed by the pacemaker to trigger the next ventricular paced beat. A more precise term for this form of PMT is endless loop tachycardia (ELT). The pacemaker actively participates in the tachycardia circuit. This occurs only in dual chamber or VDD pacemakers.

Sixty‐two years old patient with dual chamber pacemaker due to sick sinus syndrome presented to emergency department with narrow QRS tachycardia (Figure 1) 2 days after elective replacement of pulse generator (Medtronic RELIA REDR01 DDDR, 60‐130 bpm; sensed AV:150 msec; PVARB:auto; PVAB:180 msec; PAVB: 28 msec; PMT Intervention: Off) After the administration of intravenous beta blocker by emergency physician, the heart rate slowed down (Figure 2), and finally turned to normal sinusal rhythm with inappropriate spiking on T wave leading to atrial premature beat appearance (stars in Figure S1) with deeper negative P waves (arrows in Figure S1) compared to sinusal one. These tracings are considered to be related concomitant undersensing caused by connection problem and cross‐stimulation from lead reversal due to misconnection of the leads in the port during generator replacement procedure. Indeed, the ventricular spike on T wave causes premature atrial depolarization (arrows in Figure S1) following narrow QRS response (stars in Figure S1). However, this does not occur with each and every beat/spike (as did in first 3 spikes in Figure S1) because normal atrial depolarization and the normal AV nodal conduction render both those tissues physiologically refractory. Therefore, the usual trigger for an ELT is a premature atrial or ventricular complex but it could also be an atrial premature beat that coincides with a unique timing period in the pacemaker termed the post‐ventricular atrial refractory period. We confirmed the misconnection of the leads in the port during the re‐operation. Care should be exercised to avoid misconnection of the leads in the port during replacement procedure1, 2.

Figure 1

12‐lead electrocardiogram showing narrow QRS tachycardia with spikes on T waves

Figure 2

12‐lead electrocardiogram showing pacemaker spikes leading to prominent negative P wave following narrow QRS response

CONFLICT OF INTEREST

Authors declare no conflict of interests for this article.

Click here for additional data file.