A New QT Interval Correction Formulae to Adjust for Increases in Heart Rate

Abstract

A new QTc formula was developed which eliminates the relationship between QT and HR. At faster HRs, the 2 most commonly used QTcs provide numerical values at the extremes of QTc. Compared to existing formulae, the new formula had the best performance.

Value of a New QT Interval Correction Formula in Adjusting for Increases in Heart Rate

“…The basis for the formulation of the new QTc has been presented in detail [6]. Briefly, a spline correction function, modeled using a cubic regression spline with four knots and an adjustment for gender was fit to the QT and heart rate ECG data from 13,600 individuals in the US National Health and Nutrition Examination Survey (NHANES) II and III studies, conducted by the Center for Disease Control (CDC) of the US [6].…”

“…Assessment of the QT interval on the ECG has attracted considerable attention as a marker for potential drug-induced cardiac toxicity or drug-induced sudden cardiac death [1][2][3], electrolyte abnormalities [4], as well as the NHANES sampling weight with spline parameters selected as those that minimized the least squares estimate fit of the QT-heart rate relationship [6]. The ECG exclusion criteria were abnormalities that made calculation of the QT interval difficult such as right or left bundle branch block, myocardial infarction left ventricular hypertrophy or rhythm not being sinus [6].…”

“…The ECG exclusion criteria were abnormalities that made calculation of the QT interval difficult such as right or left bundle branch block, myocardial infarction left ventricular hypertrophy or rhythm not being sinus [6].…”

“…A new QT-heart rate correction formula (QTc) has been developed based on ECGs from about 13,600 individuals in the NHANES US population study [6]. This QTc was shown to be was superior to other formulae [6,7]. The value of this approach, however, has not been tested in the same individual under different conditions of heart rate stress.…”

Commentary on: Gibbons J, Mojica A, Peele M. Human electrical muscular incapacitation and effects on QTc interval. J Forensic Sci https://doi.org/10.1111/1556‐4029.13490. Epub 2017 April 17

“…One of our concerns with this paper centers around the ongoing controversy not only with respect to determining normal and abnormal QTc limits (1-2), but also regarding the validity of the generally utilized Bazett's method for calculating the QTc, and the need to dissociate QT measurement from heart rate (3)(4)(5). While an in-depth review is beyond the scope of this letter, there are literally scores of publications that question the accuracy of current measurement standards even including how to measure QT intervals (6)(7)(8).…”