Which electrolyte disturbance is characteristically associated with 'peaked T waves' on the electrocardiogram?

- The characteristic electrocardiogram (ECG) finding of peaked T waves is most commonly associated with hyperkalemia.

- In hyperkalemia, the elevated serum potassium levels alter the cardiac membrane potential, leading to changes in the repolarization phase of the cardiac cycle.
- This causes the T waves to become tall, narrow, and peaked.
- As potassium levels increase further, other ECG abnormalities may develop, such as widening of the QRS complex, loss of P waves, and eventually a sine-wave pattern, which can be life-threatening.

In contrast, the other electrolyte disturbances mentioned do not typically cause peaked T waves:
- Hypocalcemia generally prolongs the QT interval.
- Hyponatremia usually has no direct characteristic ECG changes.
- Hypomagnesemia may cause arrhythmias but does not cause peaked T waves.

Therefore, when faced with the finding of peaked T waves on an ECG, the clinician should immediately consider hyperkalemia and take steps for urgent assessment and management.

Reference: Harrison's Principles of Internal Medicine, 20th Edition, Cardiovascular System, Chapter 188, Page 1342