QT interval time lag in response to heart rate changes during stress test for Coronary Artery Disease diagnosis

•ECG delineation of a transformed lead can improve the identification of T-wave end.•The QT time lag measured from stress test is a marker of CAD severity.•The QT time lag measured from stress test can be useful for CAD diagnosis.•QT time lags in response to ramp-like and abrupt-like HR changes show similar ranges.