Voir la suite de cet article sur Cursus ECG
Patient
74-year-old woman treated with amiodarone for atrial arrhythmias;
Trace
Sinus rhythm with a rate of 60 bpm; normal P-wave: positive in leads I, II, V5, V6 and negative in aVR, with no sign of atrial enlargement; normal PR-interval; narrow QRS (98 ms); wide U-wave, maximal in V4 to V5, positive in all leads except for aVR;
Patient
17-year-old adolescent with no prior history, asymptomatic;
Trace
This tracing shows an irregular atrial sinus activity with successive accelerations and slowdowns; probable physiological sinus arrhythmia in an adolescent patient; a supplementary positive deflection of low voltage (< 1 to 2 mm) and maximum in V2, V3, V4 is noted following the T-wave and after a return to the isoelectric line; this is a physiological U-wave without pathological significance;
Exergue
A positive, low amplitude U-wave is most often physiological. On the other hand, the presence of a prominent U-wave should evoke bradycardia or hypokalemia, while the presence of a negative T-wave is evocative of an ischemic origin.
On a normal electrocardiogram, an additional deflection is often seen at the end of repolarization. The U-wave is an electrical signal of low amplitude and low frequency which occurs after the T-wave.