What is the U wave in an ECG?

What is the U wave in an ECG?

• A. Repolarization of the papillary muscle.
• B. Depolarization of the ventricles.
• C. Repolarization of the atria.
• D. Depolarization of the papillary muscle.

Answer: (A)

The U wave is a small deflection that appears after the T wave and is best explained by late repolarization of ventricular structures, most often the papillary muscles, following the main ventricular repolarization. This timing and small amplitude fit with the idea that these muscles repolarize later than the bulk of the ventricular tissue, producing a distinct after-T wave. Ventricular depolarization occurs during the QRS complex, not as a after-T event, so that option doesn’t fit. Atrial repolarization is typically masked by the QRS and isn’t seen as a separate wave. Depolarization of the papillary muscle would contribute to the QRS, not generate an after-T deflection.

The U wave is a small deflection that appears after the T wave and is best explained by late repolarization of ventricular structures, most often the papillary muscles, following the main ventricular repolarization. This timing and small amplitude fit with the idea that these muscles repolarize later than the bulk of the ventricular tissue, producing a distinct after-T wave. Ventricular depolarization occurs during the QRS complex, not as a after-T event, so that option doesn’t fit. Atrial repolarization is typically masked by the QRS and isn’t seen as a separate wave. Depolarization of the papillary muscle would contribute to the QRS, not generate an after-T deflection.