Which ECG change corresponds to potassium levels 7.5-8.5 mmol/L?

Which ECG change corresponds to potassium levels 7.5-8.5 mmol/L?

• A. Tall tented T waves
• B. Loss of P waves
• C. Widening QRS
• D. Sine wave

Answer: (C)

Potassium at this high level slows conduction through the ventricles because it inactivates some sodium channels and raises the resting membrane potential toward threshold. That slowing manifests on the ECG as widening of the QRS complex, which is the hallmark of more severe hyperkalemia. Earlier changes you might see include tall, peaked T waves, and as potassium climbs further you can lose P waves, with sine waves typically appearing only at extreme levels. So the QRS widening best matches the 7.5–8.5 mmol/L range.

Potassium at this high level slows conduction through the ventricles because it inactivates some sodium channels and raises the resting membrane potential toward threshold. That slowing manifests on the ECG as widening of the QRS complex, which is the hallmark of more severe hyperkalemia. Earlier changes you might see include tall, peaked T waves, and as potassium climbs further you can lose P waves, with sine waves typically appearing only at extreme levels. So the QRS widening best matches the 7.5–8.5 mmol/L range.