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12. Nice Seeing "U" Again


The U wave is the only remaining enigma of the ECG, and probably not for long. The origin of the U wave is still in question, although most authorities correlate the U wave with electrophysiologic events called "afterdepolarizations" in the ventricles. These afterdepolarizations can be the source of arrhythmias caused by "triggered automaticity" including torsade de pointes. The normal U wave has the same polarity as the T wave and is usually less than one-third the amplitude of the T wave. U waves are usually best seen in the right precordial leads especially V2 and V3. The normal U wave is asymmetric with the ascending limb moving more rapidly than the descending limb (just the opposite of the normal T wave).

image 01-03

Differential Diagnosis of U Wave Abnormalities

Prominent upright U waves

Negative or "inverted" U waves

Ischemic heart disease (often indicating left main or LAD disease)

Nonischemic causes

Test your knowledge on lesson 12

I would like to thank Intermountain Healthcare for its support in allowing me to create this educational material to improve patient care.