Which ECG change is most indicative of hyperkalemia?

The characteristic ECG changes associated with hyperkalemia primarily include wide QRS complexes and peaked T waves. These changes occur due to the elevated potassium levels affecting myocardial depolarization and repolarization.

In hyperkalemia, increased extracellular potassium concentration leads to alterations in the resting membrane potential of cardiac myocytes, which slows down conduction through the His-Purkinje system and the myocardium. The peaked T waves are especially prominent as they reflect a change in the action potential duration and repolarization process. The widening of the QRS complex indicates a loss of the normal rapid conduction through the ventricles, which is a critical finding that signals severe hyperkalemia and potential progression to more severe arrhythmias or asystole if not treated.

Other options, while relevant to various cardiac pathologies, do not specifically indicate hyperkalemia. For example, a prolonged QT interval may suggest other electrolyte imbalances or drug effects, inverted T waves can be associated with ischemia, and ST segment depression typically points to myocardial ischemia. None of these changes are as specific or as characteristic of hyperkalemia as the combination of wide QRS complexes and peaked T waves. Thus, the wide QRS and peaked T waves are the most indicative ECG