A long QT made by a long, flat ST segment, with a normal-looking T wave at the end of it.
Low calcium stretches the ST segment. The T wave itself stays its normal size and shape; it just arrives late, at the end of a long flat line. That's the difference from drug-induced or congenital long QT, where the T itself is broad or odd, and from hypokalemia, where the T flattens and U waves appear. Torsades is possible but uncommon. Look for tetany, perioral numbness, carpopedal spasm, recent neck surgery or pancreatitis.
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.
Sinus rhythm with a QT too long for the rate: the T wave ends late, a QTc of 500 ms or more here, where the risk of torsades climbs.
Flattened T waves, ST depression and prominent U waves (best in V2-V3) that can merge with the T to look like a long QT.
A short QT (QTc under 350 ms): the ST segment almost disappears, so the T wave starts right off the QRS.
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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