Hypercalcemia

Hypercalcemia causes shortening of the QT interval, particularly the ST segment. This can cause a pseudoOMI pattern as the beginning of the T wave may be mistaken for ST elevation when the ST segment becomes very short. Note, however, that the J point is unaffected. The quickest clue to the fact that it is hypercalcemia and not an OMI is the short QTc as ischemia tends to produce a prolonged QTc. Severe hypercalcemia can also cause Osborn waves. Patients with severe hypercalcemia have higher risk for ventricular arrhythmias. 

Examples:

Further Reading:

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

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