Do ventricular repolarization interval ratios depend on heart rate and should they be rate-corrected?

QT interval decreases with increasing heart rate (HR), hence to define normal values of QT interval for different heart rates requires the application of a QT interval rate correction formula. However, the influence of HR on the ratios between several ventricular repolarization intervals, that can be useful as risk predictors of malignant ventricular arrhythmias is unknown. This study analyzes the influence of HR on QTp/QT, JTp/JT, Tpe/JTp, and Tpe/JT ratios on a healthy subject during exercise. The intervals were measured in V3 lead and the characteristic points of QRS complex and T wave were detected by computer algorithms based on the wavelet transform (WT). Exercise stress was graded according to the four initial stages of the Bruce protocol. The heart rate was divided into two ranges: less than 100 beats/min and from 100 beats/min to 185 beats/min. When HR exceeded 100 beats/min, QTp/QT and JTp/JT ratios increased whereas Tpe/JTp and Tpe/JT ratios decreased for increasing HR. However, when HR was below 100 beats/min, those same four ratios were independent from HR. As opposed to the QT interval, there is no need to correct QTp/QT, JTp/JT, Tpe/JTp, and Tpe/JT ratios when HR is below 100 beats/min.