Hyperkalemia causes increased extracellular potassium concentration, which affects cardiac myocyte membrane potential and repolarization. This leads to accelerated repolarization of the ventricles, resulting in the characteristic peaked, tall, and narrow T waves on the ECG. These peaked T waves are often the earliest and most specific ECG sign of hyperkalemia. Recognizing this pattern is crucial for timely diagnosis and management to prevent severe arrhythmias.

Reference: Harrison's Principles of Internal Medicine, J. Larry Jameson et al., 20th Edition.