Electrocardiographic T Wave and its Relation With Ventricular Repolarization Along Major Anatomical Axes

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Background—The genesis of the electrocardiographic T wave is incompletely understood and subject to controversy. We have correlated the ventricular repolarization sequence with simultaneously recorded T waves.Methods and Results—Nine pig hearts were Langendorff-perfused (atrial pacing, cycle length 650 ms). Local activation and repolarization times were derived from unipolar electrograms sampling the ventricular myocardium. Dispersion of repolarization time was determined along 4 anatomic axes: left ventricle (LV)–right ventricle (RV), LV:apico-basal, LV:anterior-posterior, and LV:transmural. The heart was immersed in a fluid-filled bucket containing 61 electrodes to determine Tp (Tpeak in lead of maximum integral), TpTe (Tp to Tend), and TpTe_total (first Tpeak in any lead to last Tend in any lead). Repolarization was nonlinearly distributed in time. RT25 (time at which 25% of sites were repolarized, 288±26 ms) concurred with Tp. TpTe was 38±8 ms, and TpTe_total was 75±9 ms. TpTe_total correlated with dispersion of repolarization time in the entire heart (73±18 ms), but not with dispersion of repolarization times along individual axes (LV–RV, 66±17 ms; LV:apico-basal, 51±18 ms; LV:anterior-posterior, 51±27 ms; mean LV:transmural, 14±7 ms; all n=9).Conclusions—We provide a correlation between local repolarization and T wave in a pseudo-ECG. Repolarization differences along all anatomic axes contribute to the T wave. TpTe_total represents total dispersion of repolarization. At Tp, ≈25% of ventricular sites have been repolarized.

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