Look closely at the rhythm strip – there are actually three separate (and unrelated) rhythms on this strip. There are P waves (↑) at 75/minute, QRS complexes (●) at 25/minute that are dissociated from the P waves, and pacer spikes (↓) at 70/minute which neither capture nor sense. This is an example of pacemaker failure and underlying complete heart block (the reason this patient had a pacemaker in the first place).

This pacemaker had failed to generate sufficient energy to capture or sense normally – the battery needed to be changed!