Question

Which of the following is not associated with hyperkalemia?

• A. Tall T waves
• B. Prolonged QRS interval
• C. Short P.R. interval
• D. Sine waves

Hint:

Hyperkalemia prolongs the PR interval, it never shortens it.

Answer 1

The Correct Option is C

This question asks which ECG change does not belong to the usual list seen with a raised potassium level.

1. Tall T waves: This is the earliest and most classic hyperkalemia change, caused by faster repolarization of the ventricles.
2. Prolonged QRS interval: As potassium keeps rising, conduction through the ventricles slows, widening the QRS complex.
3. Short P.R. interval: Wrong direction. High potassium slows conduction through the atria and AV node, which stretches the PR interval, it does not shorten it.
4. Sine waves: In severe, life threatening hyperkalemia, the wide QRS blends into the T wave, giving a smooth sine wave shape on the strip.

Since three of the four choices are genuine hyperkalemia findings, the odd one out is the short PR interval, because the real effect of high potassium is to prolong, not shorten, that interval.

Let's summarize:

• Hyperkalemia gives tall T waves, then a wide QRS, then a sine wave pattern as it worsens.
• The PR interval gets longer with hyperkalemia, never shorter.

So a short PR interval is the feature that is not associated with hyperkalemia.