Understanding proarrhythmic potential in therapeutic drug development: alternate strategies for measuring and tracking repolarization

In summary, the RMS R- to T-peak interval and RMS TW provide a means to measure and track, on a beat-to-beat basis, the mean action ventricular APD and the range (dispersion) of action potential downstroke times, respectively, regardless of activation sequence. These are 2 of the most important electrophysiologic parameters known to relate to increased risk of arrhythmia. There are no equivalent measurements using the QT interval. Furthermore, we have demonstrated a new statistical methodology for comparing repolarization and its rate dependency on subjects for which multiple recordings during differing conditions are made. © 2006 Elsevier Inc. All rights reserved.