The ECG and Electrolyte Abnormalities

Cardiac electrical activity depends on transmembrane ionic gradients and the time‐and voltage‐dependent alterations of their conductance. The presence of a J wave, or early repolarization, is characterized by an elevation at the junction between the end of the QRS complex and the beginning of the ST segment (J point) in a 12‐lead electrocardiogram (ECG). It has been associated with an increased risk of ventricular irritability and ventricular fibrillation. Hypothermia should also be considered with the presence of J point elevation. The two may be difficult to differentiate based on ECG appearance alone. A broad variety of clinical conditions can lead to low plasma magnesium concentrations, such as decreased intake, redistribution, gastrointestinal losses, and renal losses. Hypermagnesemia is an uncommon condition, and concentrations resulting in ECG changes are even more rare, with most causes resulting from iatrogenic or intentional exposure to excess magnesium salts.