Data_Sheet_3_Model-based analysis of myocardial strains in left bundle branch block.PDF

IntroductionAlthough observational studies of patients with left bundle branch block (LBBB) have shown a relation between strain morphologies and responses to cardiac resynchronization therapy (CRT), the evaluation of left ventricle (LV) dyssynchrony from echocardiography remains difficult. The objective of this article is to propose a patient-specific model-based approach to improve the analysis and interpretation of myocardial strain signals.
MethodsA system-level model of the cardiovascular system is proposed, integrating: (i) the cardiac electrical system, (ii) right and left atria, (iii) a multi-segment representation of the RVs and LVs, and (iv) the systemic and pulmonary circulations. After a sensitivity analysis step, model parameters were identified specifically for each patient. The proposed approach was evaluated on data obtained from 10 healthy subjects and 20 patients with LBBB with underlying ischemic (n = 10) and non-ischemic (n = 10) cardiomyopathies.
ResultsA close match was observed between estimated and observed strain signals, with mean RMSE respectively equal to 5.04 ± 1.02% and 3.90 ± 1.40% in healthy and LBBB cases. The analysis of patient-specific identified parameters, based on bull's-eye representation, shows that strain morphologies are related to both electrical conduction delay, and heterogeneity of contractile levels within the myocardium.
DiscussionThe model-based approach improve the interpretability echocardiography data by bringing additional information on the regional electrical and mechanical function of the LV. The analysis of model parameters show that septal motion and global strain morphologies are not only explained by electrical conduction delay but also by the heterogeneity of contractile levels within the myocardium. The proposed approach represents a step forward in the development of personalized LV models for the evaluation of LV dyssynchrony in the field of CRT.

引言
尽管针对左束支传导阻滞（left bundle branch block, LBBB）患者的观察性研究已揭示心肌应变形态与心脏再同步治疗（cardiac resynchronization therapy, CRT）应答之间存在关联，但通过超声心动图评估左心室（left ventricle, LV）不同步仍颇具挑战。本文旨在提出一种基于患者特异性模型的方法，以优化心肌应变信号的分析与解读。

方法
本文提出一种心血管系统的系统级模型，其整合了以下模块：（i）心脏电生理系统，（ii）左右心房，（iii）右心室与左心室的多节段表征，以及（iv）体循环与肺循环。在完成敏感性分析步骤后，针对每位患者特异性识别模型参数。本研究采用10名健康受试者以及20名LBBB患者的数据对所提方法进行评估，其中20例患者分别合并缺血性（n=10）与非缺血性（n=10）心肌病。

结果
估算所得应变信号与实测应变信号之间吻合度极佳，健康受试者组与LBBB患者组的平均均方根误差（root mean square error, RMSE）分别为5.04±1.02%与3.90±1.40%。基于牛眼图（bull's-eye representation）的患者特异性识别参数分析显示，心肌应变形态既与电传导延迟相关，也与心肌内收缩水平的异质性存在关联。

讨论
该基于模型的方法可通过提供左心室局部电生理与机械功能的额外信息，提升超声心动图数据的可解读性。对模型参数的分析表明，室间隔运动与整体应变形态不仅可由电传导延迟解释，还与心肌内收缩水平的异质性相关。本研究所提方法为心脏再同步治疗领域中用于评估左心室不同步的个性化左心室模型开发迈出了重要一步。