Which ECG finding is a major sign of hyperkalemia?

Which ECG finding is a major sign of hyperkalemia?

• A. Flattened T waves
• B. Broadened QRS complex
• C. Tall, peaked T waves
• D. Shortened QT interval

Answer: (C)

Elevated potassium speeds up ventricular repolarization, which makes the T waves become tall and peaked—the classic early ECG sign of hyperkalemia. This change reflects how potassium levels affect the cardiac action potential, with less negative resting potential and faster repolarization producing that distinctive tall T wave pattern. As potassium rises further, conduction slows, leading to a prolonged PR interval and widening of the QRS complex, and can progress to a sine-wave pattern. The tall, peaked T waves are the most characteristic and immediate indicator of hyperkalemia on ECG.

Elevated potassium speeds up ventricular repolarization, which makes the T waves become tall and peaked—the classic early ECG sign of hyperkalemia. This change reflects how potassium levels affect the cardiac action potential, with less negative resting potential and faster repolarization producing that distinctive tall T wave pattern. As potassium rises further, conduction slows, leading to a prolonged PR interval and widening of the QRS complex, and can progress to a sine-wave pattern. The tall, peaked T waves are the most characteristic and immediate indicator of hyperkalemia on ECG.