Upsloping ST depression of more than 1 mm at the J point in the chest leads, running into tall, symmetric T waves, with no ST elevation there and slight ST elevation in aVR.
An acute occlusion of the left anterior descending artery (proximal to the first diagonal, in LITFL's examples) that shows no ST elevation in the chest leads. Instead you see upsloping ST depression of more than 1 mm at the J point across the chest leads, running into tall, prominent, symmetric T waves, and 0.5-1 mm of ST elevation in aVR. It shows up in about 2% of acute LAD occlusions. It's a STEMI equivalent: these patients need immediate reperfusion, the same as a STEMI, and typical STEMI changes may come before or after it. No ST elevation doesn't mean no occlusion.
Each is a standard 12-lead: 2.5 seconds of each lead in four columns, with 10 seconds of lead II along the bottom, drawn to scale (25 mm a second, 10 mm a millivolt). The measurements are under each one.
T waves that are tall, narrow at the base and peaked, best seen in the chest leads. As potassium rises, the P wave flattens, the PR lengthens and the QRS widens.
ST elevation across V1-V4, from an occluded left anterior descending artery.
Horizontal ST depression in V1-V3 with tall R waves and upright T waves, and ST elevation in the posterior leads V7-V9.
The ECG tool in the app gives you a new 12-lead every time and walks you through reading it: rate, QRS, axis, then where the ST is up and down. It's part of the Paramedic level, and you can try 5 ECGs a day free.
Try the 12-lead drill
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