Hypokalemia and hypomagnesemia produce similar affects on the EKG and will be discussed together. They both prolong the QT. This is because they produce a U wave, which appears after the T wave. Additionally, they cause T wave inversion, making the ST segment look like it has scooping depressions. This may confuse some providers into suspecting ischemia, though the scooping ST segment points more to the direction of electrolyte derangement than ischemia. Sometimes, large T waves when combined with U waves and a prolonged QTc are called Himalayan T waves.

Patients with hypokalemia and hypomagnesemia are particularly prone to malignant ventricular arrhythmias, particularly torsades des pointes, if the QTc>500ms.

Examples:

Further Reading:

https://litfl.com/hypokalaemia-ecg-library/

http://hqmeded-ecg.blogspot.com/search/label/hypokalemia