Which ECG changes are associated with hyperkalemia?

• A. ST segment depression with U waves.
• B. Tall peaked T waves, widening of QRS, and potentially sine wave pattern.
• C. Shortened QT interval.
• D. Inverted T waves only.

Answer: (B)

When potassium rises, the heart’s electrical activity changes in a characteristic progression. Early on, you see tall, peaked T waves because ventricular myocytes repolarize more quickly. As potassium increases further, conduction slows, so the PR interval lengthens and the QRS complex widens. If hyperkalemia becomes severe, the QRS widening can progress to a sine-wave pattern, signaling a high risk of deadly arrhythmias. This sequence makes tall peaked T waves with widening of the QRS, and possibly a sine-wave pattern, the hallmark ECG finding of hyperkalemia. Other patterns described—such as ST depression with U waves, mere inverted T waves, or a shortened QT without the broader progression—do not align with the typical hyperkalemic changes.