Abstract
Left bundle branch block (LBBB) is associated with specific septal-to-lateral wall activation patterns which are strongly influenced by the intrinsic left ventricular (LV) contractility and myocardial scar localization. The objective of this study was to propose a computational-model-based interpretation of the different patterns of LV contraction observed in the case of LBBB and preserved contractility or myocardial scarring. Two-dimensional transthoracic echocardiography was used to obtain LV volumes and deformation patterns in three patients with LBBB: (1) a patient with non-ischemic dilated cardiomyopathy, (2) a patient with antero-septal myocardial scar, and (3) a patient with lateral myocardial scar. Scar was confirmed by the distribution of late gadolinium enhancement with cardiac magnetic resonance imaging (cMRI). Model parameters were evaluated manually to reproduce patient-derived data such as strain curves obtained from echocardiographic apical views. The model was able to reproduce the specific strain patterns observed in patients. A typical septal flash with pre-ejection shortening, rebound stretch, and delayed lateral wall activation was observed in the case of non-ischemic cardiomyopathy. In the case of lateral scar, the contractility of the lateral wall was significantly impaired and septal flash was absent. In the case of septal scar, septal flash and rebound stretch were also present as previously described in the literature. Interestingly, the model was also able to simulate the specific contractile properties of the myocardium, providing an excellent localization of LV scar in ischemic patients. The model was able to simulate the electromechanical delay and specific contractility patterns observed in patients with LBBB of ischemic and non-ischemic etiology. With further improvement and validation, this technique might be a useful tool for the diagnosis and treatment planning of heart failure patients needing CRT.
Highlights
Cardiac resynchronization therapy (CRT) is an established therapy for patients with systolic heart failure and widened QRS (>130 ms) who remain symptomatic despite optimized medical therapy [1]
Several measurements of left ventricular (LV) dyssynchrony have been proposed, but none of them have been shown to significantly improve responders’ rate [1]. This might be because only specific mechanical substrates associated with LV electrical delay are amenable to be responsive to CRT [3]
The aim of this study was to propose a model-based interpretation of the different patterns of LV contraction observed in patients with Left bundle branch block (LBBB) in case of myocardial scarring and non-ischemic cardiomyopathy
Summary
Cardiac resynchronization therapy (CRT) is an established therapy for patients with systolic heart failure and widened QRS (>130 ms) who remain symptomatic despite optimized medical therapy [1]. Several measurements of LV dyssynchrony have been proposed, but none of them have been shown to significantly improve responders’ rate [1] This might be because only specific mechanical substrates associated with LV electrical delay are amenable to be responsive to CRT [3]. The identification of these substrates is challenging because it should consider the specific electro-mechanical properties of Patient 1 Patient 2 Patient 3 the myocardium, which are highly patient-specific. Alternative approaches have been proposed to overcome this computational cost by simplifying the patient anatomy [7,8] These models successfully represented a patient diversity in LV dyssynchrony and proposed keys to understand CRT response, patient specification with real and non-invasive clinical data must be made to propose a personalized medicine
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