April 2019

Presenting EGM in a patient with known atrial arrhythmias

Jason Collinson – Chief Cardiac Physiologist
Essex Cardiothoracic Centre, Basildon and Thurrock University Hospital


A 68 year old male with a history of Mitral valve replacement, atrial arrhythmias and dual chamber pacemaker implantation for intermittent AV block attended a routine device clinic. He reported a 2 week history of palpitations and breathlessness on exertion.  Figure 1 shows the presenting EGM recorded on initial interrogation. The device settings are displayed below.

Mode: DDDR
LR/UR: 50/130 bpm.
Paced/Sensed AV delay: 200/150 ms
PVARP: 275ms
Mode switch: On
A. Tachycardia detection rate: 180bpm

Figure 1

Presenting EGM. Channel 1 displays the atrial EGM. Channel 2 the RV ventricular EGM. Channel 3 is the marker channel with intervals displayed.


What is observed in the trace?

  • Normal pacemaker function

  • Atrial undersensing

  • Failure to mode switch

  • Ventricular non-capture