Hyperkalemia is classically associated with which ECG finding?

• A. U waves
• B. Tall peaked T waves
• C. Shortened QT interval
• D. P wave flattening

Answer: (B)

Elevated potassium primarily alters ventricular repolarization, producing tall, peaked T waves on the ECG. This is the earliest and most characteristic sign of hyperkalemia because higher extracellular potassium speeds up repolarization, making these T waves become sharp and tall. As potassium rises further, conduction slows and other changes appear—PR interval lengthens, P waves flatten, and the QRS complex widens, eventually leading to a dangerous sine-wave pattern if levels are extreme. U waves are more typical of hypokalemia, not hyperkalemia, and a shortened QT interval is not the hallmark here. The key idea to recognize is the tall, peaked T waves as the classic clue to hyperkalemia.