Which description best represents the sequence of ECG changes in hyperkalemia?

• A. ST-segment elevation in contiguous leads
• B. PR prolongation
• C. Tall, peaked T waves; progression to widened QRS and sine wave at severe levels; PR prolongation.
• D. Q waves in abnormal leads

Answer: (C)

Hyperkalemia alters the heart’s electrical activity by affecting the resting membrane potential and how fast impulses travel. The ECG changes follow a recognizable sequence: initially you see tall, peaked T waves from faster repolarization; as potassium rises further, conduction through the AV node slows, producing PR prolongation; with even higher levels, ventricular conduction slows enough to widen the QRS complex; in severe cases the QRS widens further and can merge with the T wave to form a sine-wave pattern, signaling a high risk of life-threatening arrhythmias. The description that mentions tall, peaked T waves, progression to a widened QRS and sine wave at severe levels, with PR prolongation, best captures these characteristic changes and their progression. ST-segment elevation points to ischemia or infarction, not hyperkalemia; Q waves in abnormal leads suggest a prior infarct; PR prolongation alone misses the later QRS widening and sine-wave phase.