January 2019

Pacemaker follow up in a patient with congenitally corrected transposition of the great arteries

Holly Daw – Chief Cardiac Physiologist
Barts Heart Centre, West Smithfield, London EC1A 7BE


A 34 year old male with a history of congenitally corrected transposition of the great arteries (ccTGA) had a dual chamber pacemaker implanted for complete heart block (CHB) in 2012.  Since implant pacemaker follow-ups have been unremarkable. The underlying rhythm has been consistently reported as complete heart block (CHB) with a junctional escape rhythm.  The most recent follow-up showed 27 mode switch (MS) episodes with no recorded electrograms (EGMs) available for review.  When performing routine testing to assess for an underlying rhythm the episode below occurred and was stored.

Figure 1

Stored electrogram – atrial electrogram and marker channel.  No ECG attached.


a) What does the electrogram show?

  • Atrial bigeminy

  • Far field R wave (FFRW) atrial oversensing

  • Junctional rhythm with T wave oversensing

  • Junctional rhythm with FFRW atrial oversensing


a) What programming changes would you make?

  • Increase atrial sensitivity

  • Decrease atrial sensitivity

  • Increase LRL / atrial preference pacing / rate response on

  • Mode to VVI