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.

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Radiofrequency catheter ablation is an important therapeutic option for patients with recurrent ventricular tachycardia (VT). The procedure aims at cauterizing regions of the ventricle. A good knowledge of anatomical structures and tissues properties can improve procedure safety and efficacy. This work aimed at analysing the feasibility of a workflow based on multimodal image integration to assist the intervention. We focused here on a model including myocardial thickness and fibrosis extracted from late gadolinium enhanced MRI (LGE-MRI) sequence, and left ventricular anatomy segmented from multiphase computed tomography (CT). The produced model can be imported within Carto-3 c system (Biosense Webster Inc, Diamond Bar, CA), the software used during the ablation procedure. Four patients cases have been included in this preliminary study. The four produced patient specific models have been validated by a clinician, and two of them have been integrated within Carto-3 c system and used during the intervention. IntroductionCatheter ablation, used for 30 years, aims at cauterizing ventricle's regions responsible for VT initiation and maintenance. To do so, a localized delivery of radiofrequency energy is applied. It's an important therapeutic option for patients suffering of recurrent VT resistant to antiarrythmic drugs. Depending on the needs, an endocardial or an epicardial approach can be considered. Ablation of ventricle regions is not an innocuous procedure, and it raises important questions to proceed safely and efficiently. During the procedure, the physician has to know (i) the catheter's position against the VT sources, (ii) which spots to avoid (arteries, phrenic nerve), (iii) which regions could be potential targets, and (iv) what constraint can the catheter apply on the cardiac wall without perforating it (myocardium thickness).Answers have been found to these different requirements. Electroanotomical mapping systems have been early recognized as a powerful assistance tool for VT ablation [1]. Studies such as [2] have shown the benefit of visualizing structures at risk during VT ablation, segmented from CT series. A multimodal model integration has been proposed in [3], including both CT and MRI enhanced sequences. It contains wall thining (WT) zones, defined as zones where myocardium wall's thickness is less than 5 mm [4] segmented from CT, and scare core and grey zone, defined as more than 50% and 35-50% of maximal myocardial signal [5] respectively. The interest of such informations has been later confirmed in [6], as a good predictor of local abnormal ventricular activity (LAVA).Multimodality has been recognized in different heart surgery as a powerful tool to plan and guide interventions [7][8] [9]. We propose here a patient specific multimodal model built from CT and LGE-MRI, images including the left endocardium segmented on CT, and fibrosis and myocardium's thickness segmented on LGE-MRI. LGE-MRI is registered on CT in a process including Cine-MRI as an intermediate step. The objective is ...

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