I think they were talking about from epicardial wires and the atrial EKG from the wire attached to the atria, correct? Post-operative CVICU patients frequently come back with epicardial wires and you can get an atrial EKG to help identify the cause of dysrhythmia (Aflutter, why is there AV block etc..)
There are a few papers specifically on epicardial wires if this is what you were looking for
Temporary epicardial pacing after cardiac surgery: a practical review: part 1: general considerations in the management of epicardial pacing.
Temporary epicardial pacing after cardiac surgery: a practical review: part 2: