Hypomagnesemia often occurs with other electrolyte abnormalities, and these may overshadow its effects on the electrocardiogram.
Many patients with hypomagnesemia also have hypokalemia and/or hypocalcemia.
ECG changes that may be seen in a patient with hypomagnesemia:
(1) depression of the ST segment
(2) T wave changes (flattening or inversion)
(3) variation in the QT interval (may be prolonged or shortened)
(4) a prominent U wave
(5) atrial and/or ventricular arrhythmias