EDIT: Please refer to the comments below this text. The second ECG in this series shows unexpected QRS and ST-T morphology changes, which I tried to explain by way of the patient's long anterior descending coronary artery. However, Dave Richley, who is a very well-known cardiac physiologist and ECG Guru took the time to analyze these morphologies and realize they can be explained by an inadvertent ECG LEAD MISPLACEMENT. This patient does have a proximal lesion of the LAD, proven and repaired in the cath lab. But the inferior wall does not have the injury it appears to have in this second ECG. Thanks to Dave for reminding us to slow down and look closely when things don't look "right".
The Patient: These two ECGs, taken 26 minutes apart, were obtained from a 50-year-old man who complained of sudden onset of chest pain. He denied history of coronary artery disease. He was Covid-positive, and the rest of his medical history was unremarkable.
ECG No. 1: This ECG was obtained by paramedics enroute to the hospital. For your beginner-level students, it will be easy to demonstrate the large ST elevations in V3 through V6. The machine’s measurements at the bottom confirm that this ECG meets any field criteria for ST elevation M.I. “STEMI”.
But there is so much more to see! Taking a methodical approach, and starting with rate and rhythm, we see sinus bradycardia at 57 bpm. Intervals and frontal plane axis are within normal limits. R wave progression in the chest leads is stalled in V1- V3 due to loss of initial r waves (narrow QS). The transition to positive deflections in V4 – V6 is abrupt. These q waves in the V1 and V2 appear narrow, but V3 appears to have a Q wave that is almost wide enough to be considered pathological. Narrow Q waves may be a transient sign of injury, while wide ones (>40 ms) are an ECG sign of necrosis.