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.
Tricyclics, and other drugs that block sodium channels, slow conduction through the ventricles, the right side most. The QRS widens past 100 ms and its last part swings right and up, so aVR grows a tall terminal R. Over 100 ms predicts seizures; over 160 ms, ventricular arrhythmias. The anticholinergic effect drives a sinus tachycardia. In an overdose or unexplained coma, a wide QRS with that aVR R is the trigger for sodium bicarbonate under your protocol. Check lead I: its P wave stays upright, which tells you it isn't swapped arm leads.
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.
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.
In V1-V2, the ST rises over 2 mm at the J point and falls in a coved, convex curve straight into an inverted T wave.
A QRS of 0.12 s or more with a deep, broad S (QS or rS) in V1 and a broad R with no Q wave in I, aVL, V5 and V6.
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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