Background Electrical activity underlying the T-wave is less well understood than the QRS-complex. This study investigated the relationship between normal T-wave morphology and the underlying ventricular repolarization gradients using the equivalent dipole layer (EDL).

Methods Body-surface-potential-maps (BSPM, 67‑leads) were obtained in nine normal cases. Subject specific MRI-based anatomical heart/torso-models with electrode positions were created. The boundary element method was used to account for the volume conductor effects. To simulate the measured T-waves, the EDL was used to apply different ventricular repolarization gradients: a) transmural, b) interventricular c) apico-basal and d) all three gradients (a-c) combined. The combined gradient (d) was optimized using an inverse procedure (Levenberg-Marquardt). Correspondence between simulated and measured T-waves was assessed using correlation coefficient (CC) and relative difference (RD).

Results Realistic T-waves were simulated if repolarization times of: (a) the epicardium were smaller than the endocardium; (b) the left ventricle were smaller than the right ventricle and (c) the apex increased towards the base. The apico-basal gradient resulted in the highest correspondence between measured and simulated T-waves (CC = 0.84(0.81–0.91);RD = 0.68(0.60–0.71)) compared to a transmural gradient (CC = 0.77(0.71–0.80);RD = 1.46(0.82–1.75)) and an interventricular gradient (CC = 0.71(0.67–0.80);RD = 0.85(0.75–0.87)). All three gradients combined further improved the correspondence between measured and simulated T-waves (CC = 0.83(0.82–0.89);RD = 0.60(0.51–0.63)), especially after optimization (CC = 0.96(0.94–0.98);RD = 0.27(0.22–0.34)).

Conclusion The application of all repolarization gradients combined resulted in the largest agreement between simulated and measured T-waves, followed by the apico-basal repolarization gradient. With these findings, we will optimize our EDL-based inverse procedure to assess repolarization abnormalities.

背景T 波背后的电活动不如 QRS 复合波那么了解。本研究使用等效偶极层 (EDL) 研究了正常 T 波形态与潜在心室复极梯度之间的关系。

方法获得 9 个正常病例的体表电位图（BSPM，67 导联）。创建了具有电极位置的基于受试者特定 MRI 的解剖心脏/躯干模型。边界元法用于解释体积导体效应。为了模拟测量的 T 波，EDL 用于应用不同的心室复极梯度：a) 跨壁梯度，b) 室间梯度，c) 心尖-基底梯度和 d) 所有三个梯度 (ac) 的组合。使用逆过程（Levenberg-Marquardt）优化组合梯度（d）。使用相关系数 (CC) 和相对差值 (RD) 评估模拟 T 波和测量 T 波之间的一致性。

结果如果复极时间满足以下条件，则可模拟真实的 T 波： (a) 心外膜小于心内膜；(b) 左心室小于右心室，(c) 心尖向基底部增大。与透壁梯度 (CC = 0.77(0.71–0.80)) 相比，顶端基底梯度导致测量和模拟 T 波 (CC = 0.84(0.81–0.91);RD = 0.68(0.60–0.71)) 之间的最高对应性;RD = 1.46(0.82–1.75)) 和室间梯度 (CC = 0.71(0.67–0.80);RD = 0.85(0.75–0.87))。所有三个梯度相结合进一步改善了测量和模拟 T 波之间的对应关系 (CC = 0.83(0.82–0.89);RD = 0.60(0.51–0.63))，特别是在优化之后 (CC = 0.96(0.94–0.98);RD = 0.27(0.22–0.34))。

结论所有复极梯度的组合应用导致模拟和测量的 T 波之间的一致性最大，其次是顶端-基底复极梯度。有了这些发现，我们将优化基于 EDL 的逆过程来评估复极异常。