Sinus rhythm, a normal axis, normal intervals, R waves growing from V1 to V5, and no ST elevation or depression.
This is your reference picture, the one you hold every other tracing up against. Sinus rhythm at 60-100/min, PR 0.12-0.20 s, QRS under 0.12 s, and an axis between -30° and +90°. Across the chest, the R wave grows and the S shrinks from V1 (small r, deep S) to V5-V6 (tall R, small septal q), crossing over around V3-V4. T waves are upright in I, II and V3-V6 and inverted in aVR.
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 more negative than -30°: lead I positive, lead II and aVF mostly negative.
A QRS axis beyond +90°: lead I negative, aVF positive.
Left axis deviation (-45° to -90°) with qR in I and aVL, rS in II, III and aVF, and a QRS under 0.12 s.
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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