Time-Warping Analysis of the T-Wave Peak-to-End Interval to Quantify Ventricular Repolarization Dispersion During Ischemia

Variations in the dispersion of ventricular repolarization can be quantified by T-wave time-warping based index, <tex-math notation="LaTeX">dw</tex-math> . However, the early phase of the T-wave can be affected by ST-segment changes during ischemia. We hypothesized that restricting <tex-math notation="LaTeX">dw</tex-math> to the T-wave peak-to-end ( <tex-math notation="LaTeX">Tₚₑ</tex-math> ) would circumvent this limitation while still quantifying variations in repolarization dispersion. A total of 101 ECG recordings from patients undergoing coronary occlusion, together with their control recordings, were analyzed. A series of <tex-math notation="LaTeX">dw</tex-math> values was calculated by quantifying the <tex-math notation="LaTeX">Tₚₑ</tex-math> morphological variations between the T-waves at different occlusion stages and a baseline T-wave. We introduced a normalized version of <tex-math notation="LaTeX">dw</tex-math> , <tex-math notation="LaTeX">Rd</tex-math> , reflecting variations of <tex-math notation="LaTeX">dw</tex-math> during occlusion relative to control recordings ( <tex-math notation="LaTeX">Rd = 1</tex-math> corresponds to the same level of variation). The <tex-math notation="LaTeX">dw</tex-math> series followed a gradually increasing trend with occlusion time, reaching median [range] <tex-math notation="LaTeX">Rd</tex-math> values of 9.44 [1.01, 80.74] at the occlusion end. <tex-math notation="LaTeX">Rd</tex-math> at occlusion end was significantly higher than threshold values of 1, 2, 5, and 10 in 94.1%, 85.11%, 64.4% and 48.5% of patients, respectively. The spatial lead-wise analysis of <tex-math notation="LaTeX">dw</tex-math> showed distinct distributions depending on the occluded artery, suggesting a relation with the ischemia location. The relative variation <tex-math notation="LaTeX">R</tex-math> with ischemia of index <tex-math notation="LaTeX">dw</tex-math> (9.4) is greater than that of the T-wave amplitude (7.7), <tex-math notation="LaTeX">Tₚₑ</tex-math> interval (2.7) and T-wave width (3.0). In conclusion, <tex-math notation="LaTeX">dw</tex-math> tracks ischemic-induced variations in repolarization dispersion in a more robust manner than classical indexes, avoiding the impact of ST segment elevation/depression or early T-wave distortions, thus warranting further clinical studies.