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Electrocardiographic Quantitation of Heterogeneity of Ventricular Repolarization

Background:QT interval dispersion (QTd) measured from the surface ECG has emerged as the most common noninvasive method for assessing heterogeneity of ventricular repolarization. Although QTd correlates with dispersion of monophasic action potential duration at 90% repolarization and with dispersion of recovery time recorded from the epicardium, total T‐wave area, representing a summation of vectors during this time interval, has been shown to have the highest correlation with these invasive measures of dispersion of repolarization. However, recent clinical studies suggest that the ratio of the second to first eigenvalues of the spatial T‐wave vector using principal component analysis (PCA ratio) may more accurately reflect heterogeneity of ventricular repolarization.