Right axis deviation (+110° or more), a dominant R in V1, deep S waves in V5-V6, a narrow QRS, and T inversion in V1-V3 and the inferior leads (RV strain).
A thick right ventricle pulls the forces right and forward. The axis swings past +110°, V1 gets a dominant R (taller than its S, or over 7 mm), and V5-V6 keep deep S waves. The QRS stays narrow, which is what keeps it from being RBBB. RV strain adds T inversion in V1-V3 (sometimes V4) and the inferior leads, often deepest in III. Think pulmonary hypertension, chronic lung disease, mitral stenosis or congenital heart 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.
A QRS of 0.12 s or more with rSR' (an 'M') in V1-V3 and a wide, slurred S in I, aVL, V5 and V6.
Horizontal ST depression in V1-V3 with tall R waves and upright T waves, and ST elevation in the posterior leads V7-V9.
Sinus tachycardia with T inversion in V1-V3 and III together, often an S wave in I, a Q wave in III and an inverted T in III (S1Q3T3).
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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