ECG of the Week 21st December 2022 – Interpretation

Looking at the rhythm strip, there is sinus rhythm, interspersed with wide complexes. There is evidence of pacing spikes at a defined rate, approximately 80bpm. At first glance it appears as if some of these pacing spikes are resulting in capture with a ventricularly paced wide complex beat, but on closer scrutiny, these may in fact coincide with the patient throwing off ventricular ectopic beats rather than representing electrical capture.

When there are pacing spikes, it is important to consider if the pacemaker is sensing appropriately (ie: no pacing spike when it detects an appropriate P wave or QRS complex depending if atrial sensing or ventricular sensing) and capturing appropriately (atrial pacing is resulting in a P wave, ventricular pacing is resulting in a QRS complex).

In this instance, the pacemaker is neither sensing appropriately nor capturing appropriately. This is potentially dangerous as there is evidence of pacemaker spikes occurring on T waves, and should the pacemaker result in electrical capture during a T wave, an R on T phenomenon could result in ventricular tachycardia.

Appropriate actions at this point would be to set the pacemaker to sense appropriately by reducing the sensing threshold (making the pacemaker more sensitive). If the patient was pacemaker dependent (they are not), then it would be prudent to increase the capture current to ensure appropriate capture occurs as well.