The value of vectorcardiographic T-wave area in assessing repolarization heterogeneity: insights from ECG-imaging

Abstract Background Repolarization abnormalities play an important role in arrhythmogenesis in patients with and without structural heart disease. In clinical practice, the QT interval from the 12-lead ECG is commonly used to assess arrhythmic risk; however, it primarily reflects the duration from the earliest intra-cardiac activation to the latest repolarization, rather than dispersion. Purpose This study aims to investigate whether the vectorcardiographic (VCG) T-wave area is superior to the conventional QT interval in identifying repolarization dispersion using ECG-imaging data. Methods 28 patients who underwent ECG-imaging (11 patients with no history of structural heart disease and 17 patients with dyssynchronous heart failure) were studied. The QT interval was derived from the 12-lead ECG and the T-wave area from the synthesized VCG using the Kors transformation matrix. Dispersion of repolarization on ECG-imaging was defined as the average of the interventricular difference in repolarization times (inter-RT) and the standard deviation of repolarization times (SD-RT) for approximately 2000 virtual epicardial nodes. Pearson correlation analyses between the T-wave area, QT interval, and ECG imaging measures of repolarization heterogeneity were performed for the entire cohort. Furthermore, sub-analyses were performed across patients with similar conduction patterns (LBBB [n=6], IVCD [n=8], and control [n=11]). Results In the overall cohort, vectorcardiographic T-wave area showed a significant but weak association with ECG-imaging inter-RT, while no significant association was observed with SD-RT. For the QT interval, there was no significant association with ECG-imaging inter-RT, though a significant but weak association was found with SD-RT. In subgroup analyses, no significant correlations were observed between either T-wave area or QT interval and ECG-imaging measures of repolarization heterogeneity. An overview of the scatterplots and correlation analyses is presented in Figure 1. Conclusion Vectorcardiographic T-wave area is significantly but only weakly associated with interventricular repolarization, while QT interval is significantly but only weakly associated with diffuse repolarization. The extent to which the T-wave area may be superior in predicting arrhythmogenic risk compared to the QT interval remains to be investigated.