A 45-year-old woman with chronic kidney disease presents with muscle weakness. Her serum potassium is 7.2 mEq/L. Which ECG change appears earliest in progressive hyperkalemia?
- A Peaked, narrow-based T waves ✓
- B Widening of the QRS complex
- C Loss of P waves with a sine wave pattern
- D ST segment elevation
Correct answer: A. Peaked, narrow-based T waves
Explanation
Hyperkalemia progresses sequentially: tall peaked narrow T waves appear first, then PR prolongation and P wave flattening, then QRS widening, and finally a sine wave pattern preceding ventricular fibrillation. Peaked T waves reflect accelerated phase 3 repolarisation caused by increased potassium conductance. QRS widening and sine wave morphology are late changes, and ST elevation is not a feature of hyperkalemia, making option D the clearly wrong distractor while B tempts those who recall only the advanced stages.
Reference: Ganong Review of Medical Physiology, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.