4 12-leads to read, drawn to scale: 25 mm a second, 10 mm a millivolt. Read each one the same way every time: rate, rhythm, QRS width, axis, then the ST segments and T waves lead by lead. Then open the answer to check yourself.
Lateral STEMI
ST elevation in I, aVL, V5 and V6, with reciprocal depression in III and aVF.
Extreme axis deviation
A QRS axis between -90° and 180° (the 'northwest'): lead I and aVF both negative, aVR positive.
Sodium-channel blocker toxicity (tricyclic overdose)
Sinus tachycardia with a QRS over 100 ms and a tall terminal R in aVR (over 3 mm, or R/S over 0.7): the end of the QRS swings right.
More on this finding: Sodium-channel blocker toxicity (tricyclic overdose)
Left ventricular hypertrophy with strain
Huge voltage (deep S in V1 plus tall R in V5 or V6 adding to 35 mm or more), with lateral ST depression and asymmetric T inversion, and ST elevation in V1-V3 that matches the deep S waves.
More on this finding: Left ventricular hypertrophy with strain
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 drillEach page shows what to look for, worked examples and the findings it's often confused with.
Reading rhythm strips? Practice those here.
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