Peaked T-waves on an ECG most commonly indicate which electrolyte disturbance?

• A. Hyperkalemia
• B. Hypokalemia
• C. Hyponatremia
• D. Hypercalcemia

Answer: (A)

Peaked T waves reflect changes in ventricular repolarization caused by elevated potassium. Potassium controls the resting membrane potential and the speed of repolarization in cardiac cells; when extracellular potassium rises, repolarization occurs more rapidly, producing tall, narrow T waves on the ECG. This is an early and classic sign of hyperkalemia and can progress to wider QRS complexes and dangerous rhythms if not addressed promptly.

In contrast, low potassium tends to flatten T waves and create U waves, hyponatremia doesn’t have a distinctive T-wave signature, and hypercalcemia shortens the QT interval rather than producing peaked T waves.