Acquired causes of short QT interval — Secondary causes of short QT interval such as hyperkalemia, acidosis, hypercalcemia, hyperthermia, effect of drugs like digitalis, effect of acetylcholine or catecholamine, and abbreviation of QT interval related to activation of ATP-sensitive K+ current (IKATP) need to be ruled out (table 3). As with cases of QT prolongation, QT interval shortening may be caused by a combination of genetic and secondary causes, including hyperkalemia, hypercalcemia, acidosis, myocardial ischemia, and increased vagal tone.