In 1989, results of the Cardiac Arrhythmia Suppression Trial, also known as the CAST trial, revealed that certain class I antiarrhythmics, when given to patients post–myocardial infarction (MI) who were at risk for ventricular arrhythmias, increased mortality.

Therefore, it became important not only to evaluate the efficacy of an antiarrhythmic, but also to determine its safety profile.