This study seeks to compare 4 known QT prolonging drugs versus placebo to determine their effects on electrophysiological and other clinical parameters. The underlying purpose is to determine if depolarization and repolarization effects caused by drugs with differing ionic channel mechanisms can be distinguished from one another, and to gauge the sensitivity and specificity of novel signal analyses for detection of depolarization and repolarization changes. Secondarily, to evaluate the exposure response relationship and drug induced effects on the heart rate biomarker relationship.