Which electrolyte disturbance is most likely indicated by tall peaked T waves and wide QRS intervals?

Tall peaked T waves and wide QRS intervals on an electrocardiogram (ECG) are indicative of hyperkalemia, which is an elevated level of potassium in the blood. As potassium levels rise, they begin to affect the electrical activity of the heart. The peaked T waves occur because increased extracellular potassium alters the cardiac myocyte repolarization processes, leading to a quicker rise in the T wave. Additionally, the widening of the QRS complex reflects impaired conduction in the ventricular myocardium due to the effects of high potassium concentration on the cardiac action potentials, which can lead to more severe arrhythmias if not addressed promptly.

Hypokalemia typically presents with flattened or inverted T waves and the presence of U waves, not peaked T waves. Hyponatremia is more associated with changes in mental status and fluid balance rather than direct ECG changes, while hypercalcemia can cause shortened QT intervals rather than the specific changes seen in hyperkalemia. Therefore, the presence of tall peaked T waves and wide QRS complexes strongly points to hyperkalemia as the electrolyte disturbance in question.