We all know that the ST segment on the ECG elevates when there is myocardial infarction and depresses in the face of myocardial ischemia. But why? I’m a big physiology nerd so it surprised me that I not only didn’t know the answer, but hadn’t even asked the question. I like to understand the why of things to help me remember the what. I can explain why the QRS complex is wide in a bundle branch block (and why you get the “rabbit ears” specifically in a RBBB). Why p waves are bigger in atrial enlargement and why the PR interval is long in AV blocks and short in WPW. So, when I was recently explaining 12-lead ECG interpretation to a group of students, I found myself stumped when I wanted to explain the pathophysiology behind the variations in the ST segment during myocardial ischemia and infarction.
So, I turned to Google and found this article from the Curious Clinicians, a medical podcast that I’ve listened to before (but not this particular episode, apparently) where they discuss the whys of ST elevation and depression. And it turns out, it’s even stranger than I thought…
critical care notes 