QT Dynamics from Holter Recordings: A Comparison of Two Averaging Methods

Abstract

Background: QT dynamics is the adaptation of repolarization duration on heart rate. There are several automatic computer algorithms for Holter analysis to describe this process. Our study was performed to compare results of two averaging algorithms inherent in an automatic Holter QT module.Methods: Two different methods of the automatic QT module of the ELATEC system were applied to digitized Holter ECGs of 50 healthy men. The first method, “QT/RR,” calculates the linear regression up to 2880 mean QT intervals (values over 30 s) and corresponding RR intervals containing the preceding 60 seconds of the QT value and the 30 seconds while QT averaging. The second method, “QT/RR class,” correlates the averaged QT duration over the corresponding 25‐ms RR interval classes. Possible differences in rate adaptive behavior between two portions of QT duration were of further interest.Results: The main result of the study was that the linear regression obtained by the “QT/RR” method was slightly, but significantly, steeper than those obtained by the “QT/RR class” method.Conclusion: Rate adaptation of QTe and QTa is the same if measured by one particular method. Studying the same population using different averaging methods leads to different results. In contrast to the “QT/RR” method, “QT/RR class” method leads to an overestimation of extreme and rare RR values. Therefore, results of “QT/RR class” method cannot be used as a surrogate for “QT/RR” methods.