Lead I is upside down all the way through (inverted P, QRS and T), aVR looks upright, and the chest leads are normal: the arm electrodes are on the wrong arms.
Swap the left and right arm electrodes and lead I flips upside down: P, QRS and T all inverted. II and III trade places, aVR and aVL trade places, and aVR can look upright. The chest leads don't use the arm electrodes the same way, so they look normal, with the R wave growing across V1-V6. That normal R progression is what separates it from dextrocardia. You placed the electrodes, so this one is yours to catch: fix them and repeat the 12-lead before anyone reads it as disease.
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.
A QRS axis beyond +90°: lead I negative, aVF positive.
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.
ST elevation in I, aVL, V5 and V6, with reciprocal depression in III and aVF.
Sinus rhythm, a normal axis, normal intervals, R waves growing from V1 to V5, and no ST elevation or depression.
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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