Let's analyze the ECG. It comes from a pacemaker patient whose pacemaker was briefly switched to VVI at 30 bpm due to a stimulation threshold test. The first 3 beats show a sinus rhythm with a frequency of approx. 40 bpm. This is followed by a premature ventricular contraction (PVC). The P wave of the next sinus node beat lands exactly on the T of the PVC. This cannot be conducted to the ventricles, either because the ventricular myocardium is still unexcitable or the PVC has conducted retrogradely into the AV node and this is therefore still refractory.
Amongst the computer's several statements was the interpretation of "Undetermined rhythm". To the computer's statement, the reviewing cardiologist added the freehand text of "Abnormally slow" but failed to provide a diagnosis.
This week, in addition to my own blog, I'm going to feature a guest case study by Guru member Vince DiGiulio, EMT-CC. This past Monday, Vince messaged me (along with Dr. Ken Grauer) on Facebook and requested my input and opinion on these serial ECGs. With Vince's blessing, he gave me permission to use any of his original 12-lead ECGs here on the Guru. Of his 6 ECGs, I've decided to post 4 of them here.