Tpeak-Tend interval as an index of global dispersion of ventricular repolarization:: Evaluations using monophasic action potential mapping of the epi- and endocardium in swine

The ECG interval from the peak to the end of the T wave (T-peak-T-end) has been used as an index of transmural dispersion of ventricular repolarization (DVR). The correlation between the T-peak-T-end interval and the global DVR, however, has not been well-evaluated. Methods: Monophasic action potentials (MAPs) were recorded from 51 +/- 10 epicardial and 64 +/- 9 endocardial sites in the left ventricles of 10 pigs, and from 41 +/- 4 epicardial and 53 +/- 2 endocardial sites in the right ventricles of 2 of the 10 pigs using the CARTO mapping system. The end of repolarization times over the epi- and endocardium were measured, and the end of repolarization dispersions over the epicardium (DVR-epi), over the endocardium (DVR-endo) and over both (DVR-total) were calculated. The QT(peak), QT(end) and T-peak-T-end intervals as well as the QT(peak) and QT(end) dispersions were obtained from the simultaneously recorded 12-lead ECG. Results: The maximal T-peak-T-end intervals (57 +/- 7 ms) were consistent with the DVR-total (58 +/- 11 ms, p > 0.05), and significantly correlated with the DVR-total (r = 0.64, p < 0.05). However, the mean T-peak-T-end intervals (44 +/- 5 ms), and T-peak-T-end intervals from lead II (41 +/- 6 ms) and V-5 (43 +/- 5 ms) were all significantly smaller than and poorly correlated with the DVR-total, as were the QT(peak) and QT(end) dispersions (15 +/- 2 ms vs. 21 +/- 4 ms). Conclusion: The maximal T-peak-T-end interval may be used as a noninvasive estimate for the global DVR, but not the QT(peak) and QT(end) dispersions, nor the mean T-peak-T-end interval and that from a single lead.