The QT interval of the ECG is the duration of time from the onset of ventricular depolarization (QRS onset) to the end of ventricular repolarization (T wave offset).  Measurement of the QT interval is strongly dependent on ECG methodology and evolving ECG technology.  A recent AHA/ACC/HRS document has reviewed in detail the often profound effect of changing digital ECG methodology on measurements and diagnostic statements.1

Other presentations in this symposium address why we need to measure the QT interval.  This presentation addresses the methodological questions and choices that affect QT measurement outcome.1,2  What do we measure to derive a QT interval?  This varies, from a single lead individual QT d