Which electrocardiographic finding is commonly seen before arrest in hypokalemia?

Which electrocardiographic finding is commonly seen before arrest in hypokalemia?

• A. Flat T waves
• B. Prominent U waves
• C. Prolonged QT intervals
• D. ST-segment elevation

Answer: (B)

In hypokalemia, the heart’s repolarization is altered because there’s less potassium outside the cells. The most characteristic ECG finding as potassium drops is a prominent U wave—the small deflection after the T wave that becomes obvious as potassium falls. This happens because late repolarization of ventricular tissue (including Purkinje components) is exaggerated when extracellular potassium is low, so the U wave becomes large. This sign often accompanies other repolarization changes like flattening or inversion of the T wave and sometimes a longer QT interval, but the prominent U wave is the hallmark feature that suggests severe hypokalemia and electrical instability. That instability is what raises the risk of dangerous rhythms and potential arrest. Other options don’t fit as well: flat T waves can occur with hypokalemia but are less specific; ST-segment changes aren’t a hallmark of hypokalemia; a prolonged QT can occur but the most distinctive and commonly seen clue before arrest is the prominent U wave.

In hypokalemia, the heart’s repolarization is altered because there’s less potassium outside the cells. The most characteristic ECG finding as potassium drops is a prominent U wave—the small deflection after the T wave that becomes obvious as potassium falls. This happens because late repolarization of ventricular tissue (including Purkinje components) is exaggerated when extracellular potassium is low, so the U wave becomes large.

This sign often accompanies other repolarization changes like flattening or inversion of the T wave and sometimes a longer QT interval, but the prominent U wave is the hallmark feature that suggests severe hypokalemia and electrical instability. That instability is what raises the risk of dangerous rhythms and potential arrest.

Other options don’t fit as well: flat T waves can occur with hypokalemia but are less specific; ST-segment changes aren’t a hallmark of hypokalemia; a prolonged QT can occur but the most distinctive and commonly seen clue before arrest is the prominent U wave.