The spatial heterogeneity of ventricular repoalarization (SHVR) is an important factor in arrhythmogenesis and it is related to increased vulnerability to fatal arrhythmia. The V-index is a non-invasive estimator of SHVR based on the analysis of the surface ECG. A significant correlation between the V-index and SHVR has been previously demonstrated theoretically and by means of numerical simulations. Also, the V-index has been shown to track expected changes in SHVR after infusion of drugs that

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... al- ter the cardiac electrophysiology. In this study, we compare for the first time estimates from the V-index with direct measures of SHVR derived from unipolar elecrograms simultaneously recorded in the left and right ventricular endocardium and in the left ventricular epicardium. In 22 recordings collected in 14 patients with normal ventricles, the V-index showed a tight and significant correlation with directed measures of SHVR, with correlation coefficients as high as r = 0.80, whereas other ECG-derived estimates of SHVR based on T-peak and T-peak to T-end measures showed lower correlations (r ≤ 0.41 and r ≤ 0.36, respectively). The results of this study suggest that the Vindex provides reliable estimates of SHVR.