Fully automated segmentation of the left atrium, pulmonary veins, and left atrial appendage from magnetic resonance angiography by joint‐atlas‐optimization

The objective of the study was to investigate the morphology, distribution, and electrophysiological profile of the autonomic fibers that innervate the ligament of Marshall (LOM). Gross anatomical dissections were performed in 10 dogs. Sections of the left vagus nerve, left stellate ganglion, and the LOM were immunostained to identify adrenergic and cholinergic nerves. Hearts were also stained for acetylcholinesterase to identify epicardial cholinergic nerves. In vivo electropyhsiological studies were performed in another 10 dogs before and after LOM ablation. The anatomical examination revealed that the LOM is innervated by a branch of the left vagus. Immunohistochemistry confirmed that these nerve bundles are predominantly cholinergic (cholinergic-to-adrenergic ratio of 12.6 ± 3.9:1). Cholinergic nerves originating in the LOM were found to innervate surrounding left atrial structures, including the pulmonary veins, left atrial appendage, coronary sinus, and posterior left atrial fat pad. Ablation of the LOM significantly attenuated effective refractory period shortening at distant sites, such as pulmonary veins and left atrial appendage, in response to vagal stimulation (vagal-induced ERP decrease in the left atrium: baseline vs. postablation = 17 vs. 4%; P = 0.0056). In conclusion, the LOM contains a predominance of cholinergic nerve fibers. Cholinergic fibers arising from the LOM innervate surrounding structures and contribute to the electrophysiological profile of the left atrium. These findings may provide a basis for the role of the LOM in the genesis and maintenance of atrial fibrillation.

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Fluid–structure interaction in a fully coupled three-dimensional mitral–atrium–pulmonary model

Biomechanics and Modeling in Mechanobiology ◽

10.1007/s10237-021-01444-6 ◽

2021 ◽

Author(s):

Liuyang Feng ◽

Hao Gao ◽

Nan Qi ◽

Mark Danton ◽

Nicholas A. Hill ◽

...

Keyword(s):

Mitral Valve ◽

Left Atrium ◽

Left Atrial ◽

Left Atrial Appendage ◽

Pulmonary Veins ◽

Three Dimensional ◽

Left Heart ◽

Structure Interaction ◽

Acute Mitral Regurgitation ◽

Reversal Flow

AbstractThis paper aims to investigate detailed mechanical interactions between the pulmonary haemodynamics and left heart function in pathophysiological situations (e.g. atrial fibrillation and acute mitral regurgitation). This is achieved by developing a complex computational framework for a coupled pulmonary circulation, left atrium and mitral valve model. The left atrium and mitral valve are modelled with physiologically realistic three-dimensional geometries, fibre-reinforced hyperelastic materials and fluid–structure interaction, and the pulmonary vessels are modelled as one-dimensional network ended with structured trees, with specified vessel geometries and wall material properties. This new coupled model reveals some interesting results which could be of diagnostic values. For example, the wave propagation through the pulmonary vasculature can lead to different arrival times for the second systolic flow wave (S2 wave) among the pulmonary veins, forming vortex rings inside the left atrium. In the case of acute mitral regurgitation, the left atrium experiences an increased energy dissipation and pressure elevation. The pulmonary veins can experience increased wave intensities, reversal flow during systole and increased early-diastolic flow wave (D wave), which in turn causes an additional flow wave across the mitral valve (L wave), as well as a reversal flow at the left atrial appendage orifice. In the case of atrial fibrillation, we show that the loss of active contraction is associated with a slower flow inside the left atrial appendage and disappearances of the late-diastole atrial reversal wave (AR wave) and the first systolic wave (S1 wave) in pulmonary veins. The haemodynamic changes along the pulmonary vessel trees on different scales from microscopic vessels to the main pulmonary artery can all be captured in this model. The work promises a potential in quantifying disease progression and medical treatments of various pulmonary diseases such as the pulmonary hypertension due to a left heart dysfunction.

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Effect of the Alterations in Contractility and Morphology Produced by Atrial Fibrillation on the Thrombosis Potential of the Left Atrial Appendage

Frontiers in Bioengineering and Biotechnology ◽

10.3389/fbioe.2021.586041 ◽

2021 ◽

Vol 9 ◽

Author(s):

Danila Vella ◽

Alessandra Monteleone ◽

Giulio Musotto ◽

Giorgia Maria Bosi ◽

Gaetano Burriesci

Keyword(s):

Atrial Fibrillation ◽

Left Atrium ◽

Left Atrial ◽

Left Atrial Appendage ◽

Thrombus Formation ◽

Fluid Dynamic ◽

Atrial Appendage ◽

Primary Role ◽

Shear Strain Rate ◽

Increased Risk

Atrial fibrillation (AF) is a common arrhythmia mainly affecting the elderly population, which can lead to serious complications such as stroke, ischaemic attack and vascular dementia. These problems are caused by thrombi which mostly originate in the left atrial appendage (LAA), a small muscular sac protruding from left atrium. The abnormal heart rhythm associated with AF results in alterations in the heart muscle contractions and in some reshaping of the cardiac chambers. This study aims to verify if and how these physiological changes can establish hemodynamic conditions in the LAA promoting thrombus formation, by means of computational fluid dynamic (CFD) analyses. In particular, sinus and fibrillation contractility was replicated by applying wall velocity/motion to models based on healthy and dilated idealized shapes of the left atrium with a common LAA morphology. The models were analyzed and compared in terms of shear strain rate (SSR) and vorticity, which are hemodynamic parameters directly associated with thrombogenicity. The study clearly indicates that the alterations in contractility and morphology associated with AF pathologies play a primary role in establishing hemodynamic conditions which promote higher incidence of ischaemic events, consistently with the clinical evidence. In particular, in the analyzed models, the impairment in contractility determined a decrease in SSR of about 50%, whilst the chamber pathological dilatation contributed to a 30% reduction, indicating increased risk of clot formation. The equivalent rigid wall model was characterized by SSR values about one order of magnitude smaller than in the contractile models, and substantially different vortical behavior, suggesting that analyses based on rigid chambers, although common in the literature, are inadequate to provide realistic results on the LAA hemodynamics.

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Pericardial Patch Exclusion Technique for Left Atrial Appendage Closure

Innovations Technology and Techniques in Cardiothoracic and Vascular Surgery ◽

10.1097/imi.0000000000000484 ◽

2018 ◽

Vol 13 (2) ◽

pp. 144-146

Author(s):

Olivia K. Ginty ◽

Ferns H. Khaliel ◽

Corey Adams ◽

Michael W. A. Chu

Keyword(s):

Left Atrium ◽

Left Atrial ◽

Left Atrial Appendage ◽

Atrial Appendage ◽

Pericardial Patch ◽

Left Atrial Appendage Closure ◽

Risk Of Bleeding ◽

Left Atrial Appendage Occlusion ◽

Autologous Pericardial Patch ◽

Patch Closure

We describe a technique of left atrial appendage occlusion that consists of autologous pericardial patch closure of the left atrial appendage orifice from within the left atrium. This pericardial patch exclusion technique has little added risk of bleeding, can be performed through sternotomy or right minithoracotomy, and can be used in re-operative situations.

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1112 Discovering the origin of a mysterious heart cavity

European Heart Journal - Cardiovascular Imaging ◽

10.1093/ehjci/jez319.657 ◽

2020 ◽

Vol 21 (Supplement_1) ◽

Author(s):

V Vidal Urrutia ◽

P Garcia Gonzalez ◽

J L Perez Bosca ◽

D Escribano Alarcon ◽

J M Simon Machi ◽

...

Keyword(s):

Left Ventricle ◽

Left Atrium ◽

Left Atrial ◽

Left Atrial Appendage ◽

Contrast Echocardiography ◽

Left Ventricular ◽

Atrial Appendage ◽

Invasive Approach ◽

Cardiovascular Morbidity And Mortality ◽

Doppler Color

Abstract Left atrial appendage aneurysm is an infrequent cardiac malformation, with less than 150 cases reported in the literature. It is a congenital anomaly in the majority of cases, related to a dysplasia of pectinate muscles and atrial muscle bands, which tends to grow with age. At the present time, and despite of being not considered in current guidelines, surgical resection is the standard of treatment in the current literature, even in asymptomatic cases, based on cardiovascular morbidity and mortality by predisposing to atrial tachyarrhythmia, thromboembolism, and other rare conditions as coronary or left ventricular compression and rupture of the aneurysm. We report the case of a 53-year-old male patient presenting an episode of supraventricular paroxysmal tachycardia with the casual finding of a mysterious cavity in the transthoracic echocardiography. We found out the presence of a 50 mm cavity adjacent to the left atrium and left ventricle, with a bidirectional blood flow between the left atrium and the cavity when applying Doppler color and with contrast echocardiography. Given this finding, several differential diagnosis had to be considered, including vascular and structural disorders. In order to clarify the diagnosis, a cardiac magnetic resonance was performed. It revealed the presence of a huge aneurysm of the left atrial appendage (50 x 53 mm) causing a mild compression of the left ventricle, with no thrombus and no other significant findings. Due to its size, the compression of the left ventricle and the history of atrial arrhythmia we decided to manage it with an invasive approach by performing a middle thoracotomy, in order to prevent potentially serious complications. Abstract 1112 Figure. CMR 3D reconstruction; echocardiography

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