Which ECG finding is most consistent with hyperkalemia?

• A. Prolonged QT interval.
• B. Delta wave.
• C. Peaked T waves.
• D. Prominent U waves.

Answer: (C)

Hyperkalemia primarily speeds up and then disrupts ventricular repolarization, so the earliest and most recognizable ECG change is tall, peaked T waves. As potassium rises further, conduction slows, leading to PR interval prolongation and widening of the QRS complex; severe hyperkalemia can produce a sine-wave pattern and dangerous arrhythmias. Other findings point to different problems: a delta wave indicates preexcitation (WPW), prominent U waves appear with hypokalemia, and a prolonged QT is more typical of hypo- or other electrolyte disturbances. Thus, the tall peaked T waves are the most characteristic sign of hyperkalemia.