Which ECG feature is most characteristic of hypokalemia?

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Multiple Choice

Which ECG feature is most characteristic of hypokalemia?

Hypokalemia most often shows prominent U waves on the ECG. When potassium is low, ventricular repolarization is slowed, which flattens or inverts the T wave and depresses the ST segment; a distinct U wave then appears after the T wave. As potassium falls further, these U waves become more marked, and the QT interval can be prolonged. This combination—prominent U waves with accompanying T-wave changes and possible QT prolongation—is the classic, most characteristic sign of hypokalemia. The other options point to different conditions: a sine-wave QRS pattern occurs with severe hyperkalemia; delta waves indicate preexcitation (WPW); a prolonged PR interval can occur with various AV conduction issues and isn’t specific to potassium levels.

Hypokalemia most often shows prominent U waves on the ECG. When potassium is low, ventricular repolarization is slowed, which flattens or inverts the T wave and depresses the ST segment; a distinct U wave then appears after the T wave. As potassium falls further, these U waves become more marked, and the QT interval can be prolonged. This combination—prominent U waves with accompanying T-wave changes and possible QT prolongation—is the classic, most characteristic sign of hypokalemia.

The other options point to different conditions: a sine-wave QRS pattern occurs with severe hyperkalemia; delta waves indicate preexcitation (WPW); a prolonged PR interval can occur with various AV conduction issues and isn’t specific to potassium levels.

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