Antiarrhythmic drugs are used to treat cardiac arrhythmia. The principle behind their use is the treatment of precipitating factors, such as hypokalemia, hypomagnesemia, ischemia, and hypoxia. Some drugs actually contribute to arrhythmias (e.g., digoxin, antiarrhythmics, or QT prolonging drugs such as erythromycin and some antipsychotics). The ultimate goal of treatment is to prolong the life of the patient. As such, it is not always wise to treat all arrhythmiasv The Cardiac Arrhythmia Suppression Trial (CAST) showed that treating asymptomatic preventricular contractions (PVCs) with a class I antiarrhythmic actually increased mortality.