AF with failure to capture and intermittent undersening

A 75 yo with h/o DM, HTN, s/p PPM admitted for stroke. What is wrong in the ECG?

Figure 1 - ECG case

Figure 2 - ECG case marked (P - pacer spikes, i - intrinsic beat, ps - pseudofusion beat)

The intrinsic rhythm (labeled i)  is atrial fibrillation with intraventricular conduction delay (IVCD) or a wide QRS morphology that do not fit the left bundle branch block (LBBB) or right bundle branch block (RBBB) configuration. The narrower complexes are pacer spikes (labeled P) that are firing at about 85 beats per minute (cycle length of about 700 ms) which are not followed by a wide QRS complexes. However, spike #6 and 17 arrived earlier and must have not seen the intrinsic QRS (undersensing). Complex #9 is a timed pacer spike but the morphology of the QRS is the same with the intrinsic beat (pseudofused beat labeled ps). The inverted T waves which are best appreciated in the precordial leads could be T-wave memory/cardiac memory. So, this ECG is atrial fibrillation, failure to capture, intermittent undersensing, with pseudofused beat and T wave memory.

Interrogation of the device revealed lead fracture.

#344