Which electrocardiographic finding is associated with hypokalemia?

• A. Peaked T waves
• B. Shortened QT interval
• C. U waves
• D. ST segment depression

Answer: (C)

Hypokalemia alters ventricular repolarization, producing a characteristic pattern on the ECG: prominent U waves. As potassium levels fall, the outward K+ current during repolarization decreases, lengthening the repolarization phase and creating a small deflection after the T wave—the U wave. This finding is most clearly seen in the precordial leads and can be accentuated as potassium becomes more depleted.

Peaked T waves indicate hyperkalemia, not hypokalemia. Shortened QT interval is not typical for hypokalemia (in fact QT can be prolonged due to delayed repolarization), and ST segment depression can occur in various conditions but is not the hallmark change of low potassium. The presence of U waves best fits the scenario of hypokalemia.