Mutual Information Reveals Non-linear Relationships between Electrocardiographic Conduction or Repolarization Indices and Mechanical Dispersion by Speckle-Tracking Echocardiography in the General Population

Abstract

Electrical inhomogeneities can lead to regional heterogeneity in left ventricular contraction. We investigated the correlation between electrocardiographic parameters of conduction and/or repolarization and myocardial longitudinal strain-derived parameters in a general population. Mean and dispersion (maximum-minimum) values were calculated for the electrocardiographic indices: QT interval, T_peak-T_end interval (Tpe), JT_peak interval (JTp), JT_end interval (JTe), QT_peak interval (QTp). Mechanical dispersion was assessed using the standard deviation (SD) of time-to-peak longitudinal strains (MD_SD) and the difference between the longest time and shortest time to peak strain (MD_delta) by speckle-tracking echocardiography. A total of 59 patients, 60 ± 12 y, were included. Tpe, Tpe/QT, Tpe/JTp and Tpe/JTe correlated well with MD_SD and MD_delta (r ≥ 0.43, p < 0.001). Mutual information revealed significant non-linear relationships between most of the electrocardiographic indices measured and mechanical dispersion. In conclusion, there is a moderate linear correlation between electrocardiographic indices reflecting repolarization heterogeneities and speckle tracking-assessed mechanical dispersion.

Keywords: Index of electrophysiological balance; Longitudinal strain;Mechanical dispersion; Speckle-tracking echocardiography; T(peak)–T(end) interval.