Comparative anatomy of the mitral valve in four species (human, ovine, porcine and canine): A pre-clinical perspective.

This study aimed to provide comparative anatomical data on the mitral valve and to substantiate the choice between large species for pre-clinical testing of cardiac devices. Different anatomical parameters of the anterior and posterior leaflets, chordae and papillary muscles were measured to characterize the anatomy of the mitral valve in 10 individuals for each four species. Ratios were calculated and used to circumvent the interspecies variations of body and heart size and weight. The results underline many relevant anatomical similarities and differences between man and the three animal species. We confirm that the porcine species is a better model based on anatomical measurements. But many parameters should be considered depending on the shape, size and purpose of the device. The mitral and aortic valve are closer than in man leading to potential damage of the aortic valve by a mitral device. The ovine mitral annulus is more flattened and would sustain more mechanical forces on a round-shaped stent. The anterior and posterior leaflets have comparable height in the animal species leading to more space for implantation. The porcine valve has more chordae allowing less space around the valve for a transcatheter stent. Our observations introduce new comparative data in the perspective of the choice of a large animal model for pre-clinical testing of mitral devices. They are very helpful for all cardiologists, surgeons or engineers who need to understand the reasons for success or failure of a device and to have key elements of discussion.

Finite element analysis of mitral valve annuloplasty in Barlow's disease.

Barlow's Disease affects the entire mitral valve apparatus causing mitral regurgitation. Standard annuloplasty procedures lead to an average of 55% annular area reduction of the end diastolic pre-operative annular area in Barlow's diseased valves. Following annular reduction, mitral valvuloplasty may be needed, usually with special focus on the posterior leaflet. An in silico pipeline to perform annuloplasty by utilizing the pre- and -postoperative 3D echocardiographic recordings was developed. Our objective was to test the hypothesis that annuloplasty ring sizes based on a percentage (10%-25%) decrease of the pre-operative annular area at end diastole can result in sufficient coaptation area for the selected Barlow's diseased patient. The patient specific mitral valve geometry and finite element model were created from echocardiography recordings. The post-operative echocardiography was used to obtain the artificial ring geometry and displacements, and the motion of the papillary muscles after surgery. These were used as boundary conditions in our annuloplasty finite element analyses. Then, the segmented annuloplasty ring was scaled up to represent a 10%, 20% and 25% reduction of the pre-operative end diastolic annular area and implanted to the end diastolic pre-operative finite element model. The pre-operative contact area decrease was shown to be dependent on the annular dilation at late systole. Constraining the mitral valve from dilating excessively can be sufficient to achieve proper coaptation throughout systole. The finite element analyses show that the selected Barlow's diseased patient may benefit from an annuloplasty ring with moderate annular reduction alone.

Excursão sistólica do anel tricúspide e do anel mitral: correlação com função diastólica ventricular esquerda / Tricuspid annular plane systolic excursion and mitral annular systolic excursion: correlation with left ventricular diastolic function

Introdução: A excursão sistólica do anel tricúspide e a do anel mitral são parâmetros utilizados para se avaliar a função contrátil do ventrículo direito e do ventrículo esquerdo, respectivamente. Pouco se conhece sobre sua relação com a função diastólica ventricular esquerda. Objetivo: Avaliar se os valores de excursão sistólica do anel tricúspide e do anel mitral se correlacionam com parâmetros utilizados na avaliação da função diastólica ventricular esquerda. Métodos: Estudo observacional transversal. Foram selecionados 219 indivíduos, sendo 116 mulheres, com função sistólica preservada de ambos os ventrículos. As análises foram feitas separadamente para os sexos masculino e feminino, por meio dos coeficientes de correlação de Pearson e de Sperman. Foram obtidos: excursão sistólica do anel tricúspide, excursão sistólica do anel mitral, volumes atriais e medidas relacionadas à avaliação da função diastólica do ventrículo esquerdo ao ecocardiograma transtorácico. Resultados: No sexo feminino, a excursão sistólica do anel mitral se correlacionou positivamente com o e' lateral (coeficiente de correlação de Sperman de 0,22; p=0,016) e a excursão sistólica do anel tricúspide se correlacionou positivamente com a relação E/A (coeficiente de correlação de Sperman de 0,23, p=0,037), com o e' lateral (coeficiente de correlação de Sperman de 0,28; p=0,012), com o e' septal (coeficiente de correlação de Sperman de 0,28; p=0,012) e negativamente com a relação E/e' (coeficiente de correlação de Pearson de -0,27; p=0,018) e onda A (coeficiente de correlação de Pearson de -0,29; p= 0,009). No sexo masculino, apenas a excursão sistólica do anel mitral se correlacionou positivamente com a onda E (coeficiente de correlação de Pearson de 0,21; p=0,037), e' lateral (coeficiente de correlação de Sperman de 0,34; p <0,001) e e' septal (coeficiente de correlação de Sperman de 0,26; p=0,008). Não houve correlação entre excursão sistólica do anel mitral e do anel tricúspide e volumes atriais. A presença de hipertensão arterial sistêmica e diabetes melito influenciou nos valores de excursão sistólica do anel tricúspide e do anel mitral correlacionados a ondas E e A, relação E/A, ondas e' septal e lateral e relação E/e'. Conclusão: No presente estudo, os valores da excursão sistólica do anel mitral e do anel tricúspide apresentaram correlação significativa com algumas variáveis da função diastólica ventricular esquerda com maior evidência no sexo feminino.(AU)

Introduction: Tricuspid annular plane systolic excursion and mitral annular systolic excursion are parameters used to assess the systolic function of the right ventricle and left ventricle, respectively. Little is known about its relationship with left ventricular diastolic function. Objective: To assess whether the values of mitral annular systolic excursion and tricuspid annular plane systolic excursion correlate with parameters used in the evaluation of left ventricular diastolic function. Method: Observational cross-sectional study. Two hundred nine individuals were selected, 116 women, with both ventricles normal systolic function. The analyzes were performed for men and women, through Pearson correlation coefficient and Sperman correlation coefficient. Tricuspid annular plane systolic excursion, mitral annular systolic excursion, atrial volumes and left ventricular diastolic function parameters on transthoracic echocardiogram were obtained. Results: In women, mitral annular systolic excursion was positively correlated with lateral e '(Sperman correlation coefficient of 0.22; p=0.016) and tricuspid annular plane systolic excursion was positively correlated with E / A ratio (Sperman correlation coefficient of 0.23; p=0.037), lateral e' (Sperman correlation coefficient of 0.28; p=0.012), and septal e' (Sperman correlation coefficient of 0.28; p=0.012), and negatively with the E/e' ratio (Pearson correlation coefficient of -0.27; p=0.018), and A wave (Pearson correlation coefficient of -0.29; p=0.009). In men, only mitral annular systolic excursion correlated positively with E wave (Pearson correlation coefficient of 0.21; p=0.037), lateral e' (Sperman correlation coefficient of 0.34; p <0.001) and the septal e' (Sperman correlation coefficient of 0.26; p=0.008). There was no correlation between mitral annular systolic excursion E and tricuspid annular plane systolic excursion and atrial volumes. Hypertension and diabetes mellitus influenced tricuspid annular plane systolic excursion and mitral annular systolic excursion values correlated to E and A waves, E/A ratio, septal and lateral e' waves, and E/e' ratio. Conclusion: In the present study, mitral annular systolic excursion and tricuspid annular plane systolic excursion values showed a significant correlation with some parameters of left ventricular diastolic function, with stronger evidence on female sex.(AU)

The Relationship of Mitral Annulus Shape at CT to Mitral Regurgitation after Transcatheter Aortic Valve Replacement.

Background There are conflicting results over the improvement rate and predictors of mitral regurgitation in patients undergoing transcatheter aortic valve replacement (TAVR). Purpose To define the cause, degree of improvement, and improvement predictors of moderate to severe mitral regurgitation in patients undergoing TAVR by using a simplified D-shaped mitral annulus model derived from multisection CT (MSCT). Materials and Methods This retrospective cohort study included 528 consecutive patients who underwent TAVR between April 2012 and October 2019. Patients with previous surgical aortic valve replacement and those with moderate or severe mitral stenosis were excluded. A total of 104 patients with moderate to severe mitral regurgitation met the inclusion criteria and were included in the final analysis. At least one grade reduction in the severity of mitral regurgitation was considered indicative of mitral regurgitation improvement after TAVR. Up to 5-year post-TAVR follow-up of mitral regurgitation improvement was evaluated. Mitral annular dimensions (annular area, circumference, and trigone-to-trigone, intercommissural, and anteroposterior distances) and annular calcification were assessed at MSCT with use of dedicated postprocessing software. Associations with mitral regurgitation improvement after TAVR were explored. Results A total of 104 patients with concomitant mitral regurgitation who underwent TAVR (mean age, 74 years ± 7; 61 men) were included in the study. Mitral regurgitation improved in 79 patients after TAVR and remained unchanged in the remaining 25 patients. Maximum improvement was observed in the 1st year after TAVR. D-shaped mitral annular parameters, including annular circumference (odds ratio [OR], 1.05; 95% CI: 1.01, 1.1; P = .02) and trigone-to-trigone (OR, 1.2; 95% CI: 1.03, 1.39; P = .02) and intercommissural (OR, 1.15; 95% CI: 1.02, 1.31; P = .02) distances, were related to mitral regurgitation improvement. In addition, patients with coronary artery disease had greater improvement in mitral regurgitation after TAVR (OR, 0.17; 95% CI: 0.04, 0.76; P = .02). Primary mitral regurgitation (OR, 5.1; 95% CI: 1.1, 24; P = .04) and D-shaped annular circumference (OR, 1.06; 95% CI: 1, 1.11; P = .04) were independent predictors of less mitral regurgitation improvement after TAVR. Conclusion Concomitant mitral regurgitation in patients undergoing transcatheter aortic valve replacement (TAVR) tends to improve after the procedure, with maximum improvement in the 1st year after TAVR. D-shaped annular circumference and primary mitral regurgitation were independent predictors of less mitral regurgitation improvement after TAVR. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Collins in this issue.

Automatic extraction of the mitral valve chordae geometry for biomechanical simulation.

PURPOSE: Mitral valve computational models are widely studied in the literature. They can be used for preoperative planning or anatomical understanding. Manual extraction of the valve geometry on medical images is tedious and requires special training, while automatic segmentation is still an open problem. METHODS: We propose here a fully automatic pipeline to extract the valve chordae architecture compatible with a computational model. First, an initial segmentation is obtained by sub-mesh topology analysis and RANSAC-like model-fitting procedure. Then, the chordal structure is optimized with respect to objective functions based on mechanical, anatomical, and image-based considerations. RESULTS: The approach has been validated on 5 micro-CT scans with a graph-based metric and has shown an [Formula: see text] accuracy rate. The method has also been tested within a structural simulation of the mitral valve closed state. CONCLUSION: Our results show that the chordae architecture resulting from our algorithm can give results similar to experienced users while providing an equivalent biomechanical simulation.

Energy loss associated with in-vitro modeling of mitral annular calcification.

INTRODUCTION: Study aims were to compare hemodynamics and viscous energy dissipation (VED) in 3D printed mitral valves-one replicating a normal valve and the other a valve with severe mitral annular calcification (MAC). Patients with severe MAC develop transmitral gradients, without the commissural fusion typifying rheumatic mitral stenosis (MS), and may have symptoms similar to classical MS. A proposed mechanism relates to VED due to disturbed blood flow through the diseased valve into the ventricle. METHODS: A silicone model of a normal mitral valve (MV) was created using a transesophageal echocardiography dataset. 3D printed calcium phantoms were incorporated into a second valve model to replicate severe MAC. The synthetic MVs were tested in a left heart duplicator under rest and exercise conditions. Fine particles were suspended in a water/glycerol blood analogue for particle image velocimetry calculation of VED. RESULTS: Catheter mean transmitral gradients were slightly higher in the MAC valve compared to the normal MV, both at rest (3.2 vs. 1.3 mm Hg) and with exercise (5.9 vs. 5.0 mm Hg); Doppler gradients were 2.7 vs. 2.1 mm Hg at rest and 9.9 vs 8.2 mm Hg with exercise. VED was similar between the two valves at rest. During exercise, VED increased to a greater extent for the MAC valve (240%) versus the normal valve (127%). CONCLUSION: MAC MS is associated with slightly increased transmitral gradients but markedly increased VED during exercise. These energy losses may contribute to the exercise intolerance and exertional dyspnea present in MAC patients.

Correction of Bileaflet Mitral Valve Prolapse Through Reduction of Posterior Leaflet Height.

Mitral regurgitation due to bileaflet prolapse can be corrected with height reduction of the posterior leaflet through detachment at its base, division of accompanying secondary chordae, and leaflet-annular reapproximation. This technique lowers the posterior leaflet height to approximately 1.5 cm, thereby displacing the line of coaptation posteriorly to achieve symmetry without the need for additional artificial chordae. Of 37 patients who underwent this type of repair at our institution, no patient had recurrent mitral regurgitation ≥ 2 at an average follow-up of 1.9 years (range, 0.2-4.5).

Associations between cardiac function and retinal microvascular geometry among Chinese adults.

Abnormal retinal microvascular geometry has been associated with cardiac remodeling and heart failure. However, its relation to cardiac function, prior to clinical disease has not been explored. In this cross-sectional study, 50 participants (mean age 62.5 ± 11.7 years) without cardiovascular disease (CVD) were recruited from the Cardiac Ageing Study. Transthoracic echocardiography imaging was performed to measure cardiac function indices, and retinal imaging was used to measure retinal vascular caliber and retinal vascular geometric indices. Multiple linear regressions were applied to examine associations between indices of cardiac function and retinal microvasculature, adjusting for age, sex, body mass index, mean blood pressure and comorbidity (i.e. hypertension, diabetes and dyslipidemia). After adjusting for confounders, each unit decrease in peak systolic septal mitral annular velocity (Septal S') indicating poorer left function was associated with smaller retinal venular branching angle (ß: - 2.69°; 95% CI - 4.92, - 0.46). Furthermore, each unit increase in peak velocity flow in late diastole by atrial contraction (MV A Peak) indicating poorer left atrial function was associated with lower retinal venular fractal dimension (- 0.13Df; - 0.25, - 0.004). Our findings suggested a relationship between poorer cardiac function and suboptimal retinal microvascular geometry, among Chinese without CVD.

Functional Grading of a Transversely Isotropic Hyperelastic Model with Applications in Modeling Tricuspid and Mitral Valve Transition Regions.

Surgical simulators and injury-prediction human models require a combination of representative tissue geometry and accurate tissue material properties to predict realistic tool-tissue interaction forces and injury mechanisms, respectively. While biological tissues have been individually characterized, the transition regions between tissues have received limited research attention, potentially resulting in inaccuracies within simulations. In this work, an approach to characterize the transition regions in transversely isotropic (TI) soft tissues using functionally graded material (FGM) modeling is presented. The effect of nonlinearities and multi-regime nature of the TI model on the functional grading process is discussed. The proposed approach has been implemented to characterize the transition regions in the leaflet (LL), chordae tendinae (CT) and the papillary muscle (PM) of porcine tricuspid valve (TV) and mitral valve (MV). The FGM model is informed using high resolution morphological measurements of the collagen fiber orientation and tissue composition in the transition regions, and deformation characteristics predicted by the FGM model are numerically validated to experimental data using X-ray diffraction imaging. The results indicate feasibility of using the FGM approach in modeling soft-tissue transitions and has implications in improving physical representation of tissue deformation throughout the body using a scalable version of the proposed approach.

Fibras musculares cardíacas en las cúspides de la valva atrioventricular izquierda humana / Cardiac muscle fibers at the cusps of the human left atrioventricular valve

Las valvas cardíacas y especialmente la valva atrioventricular izquierda (VAVI) ha sido considerada por largo tiempo, como una estructura pasiva. Sin embargo, han surgido nuevas teorías que reconocen a esta estructura como una "valva viva", con un funcionamiento de mayor autonomía y dinámico. En esta línea, existen estudios en donde se ha concluido que la ausencia de tejidos contráctiles en una valva, generan ondulaciones no fisiológicas. Por el contrario, se ha señalado la presencia de tejido contráctil en la valva, lo que refleja una activación ondulante. Basado en lo anterior, el objetivo del presente estudio fue determinar la presencia de fibras musculares cardíacas en las cúspides de la VAVI. Se utilizaron 12 cúspides, 6 anteriores y 6 posteriores, de 7 cadáveres adultos (4) y lactantes (3) de distintas edades, sin patologías cardíacas. Las muestras pertenecían a la Facultad de Medicina de la Universidad Estadual de Ciencias da Saúde de Alagoas, Maceió, Brasil. Estas muestras fueron tratadas con procesamiento histológico de rutina. Los hallazgos morfológicos a un aumento de 4x mostraron células musculares que fueron visibles principalmente por el lado atrial en la totalidad de las cúspides, tanto inmersas en el tejido conectivo denso del anillo fibroso como en el tejido conectivo laxo. Al verificar la naturaleza de las fibras con un aumento mayor (100x), se detectaron estrías transversales en todas las muestras estudiadas, lo cual afirma la presencia de fibras musculares estríadas cardíacas en la VAVI. Los resultados obtenidos aportan al conocimiento de la microestructura y tejido contráctil de las cúspides de la VAVI. Por lo tanto, resulta de gran relevancia seguir profundizando en los conocimientos morfológicos de la VAVI, para sentar una base sólida sobre la microestructura contráctil en los diferentes estadíos del ser humano.

Cardiac valves and particularly, the left atrioventricular valve (LAVV) have long been considered passive structures. Nonetheless, there are more recent hypothesis that recognize this structure as a "living valve", with greater autonomy and dynamic function. Along these lines, some studies have concluded that the absence of contractile tissues in a valve, generates non-physiological undulations. In contrast, the presence of contractile tissue in the valve has been reported, reflecting a waving activation. Based on the above, the objective of the present study was to determine the presence of cardiac muscle fibers in the cusps of the LAVV. 12 cusps, 6 anterior and 6 posterior. Therefore, 7 adult (4) and lactating (3) bodies of different ages without cardiac pathologies were used. The samples belonged to the Faculty of Medicine of the Universidade de Ciencias da Saude de Alagos, Maceió, Brazil. The samples were treated with routine histological processing. Morphological findings at an increase of 4x showed muscle cells that were visible mainly from the atrial side in all the cusps, both immersed in the dense connective tissue of the fibrous ring and in loose connective tissue. Transverse striations were detected in all samples studied, when verifying the nature of the fibers with greater increase (100x), confirming the presence of cardiac striated muscle fibers in the LAVV. The results obtained contribute to the knowledge of the microstructure and contractile tissue of the LAVV cusps. Therefore it is relevant to further morphological knowledge of this valve, in order to build a solid foundation on the contractile microstructure in the different stages of the human development.

Anatomical relationship between mitral valve annulus and circumflex artery and its surgical implications.

BACKGROUND: Performing surgical procedures around the mitral valve (MV) annulus can cause iatrogenic lesions on the circumflex artery (Cx). The risk of this iatrogenesis comes from the proximity between this vessel and the MV annulus. OBJECTIVE: To evaluate the relation between the MV annulus and the Cx at different spots of its path and highlight the risks of its damage. METHODS: Fifty cadaveric adult human hearts were studied. Each heart was categorized depending on coronary dominance, and Cx was classified in type 1 (Cx giving off only the left posterior ventricular artery) and type 2 (Cx reaching the crux cordis and giving off the posterior interventricular branch). Three reference spots were chosen: A- when Cx begins to run across the coronary sulcus; B- immediately before the left posterior ventricular artery emerges and C- in the midpoint of the two previous points; to measure the diameter of the Cx and the MV annulus. Values of P<0.05 were considered significant. RESULTS: A total of 43 (86%) hearts were classified in type 1. These hearts showed that the diameter of the Cx in spot A is bigger than in the B and C spots (P=0.001). The 7 hearts (14%) classified in type 2 did not exhibit a difference in the diameter of the Cx in the A, B and C spots (NS). Also, the thickness of the fibrous annulus, in type 1 and type 2 hearts were not different between the three spots (NS). CONCLUSION: The present study showed that the diameter of the Cx varies depending on the heart type. This knowledge might improve the success rate of cardiac surgeries and decrease the rates of iatrogenic Cx lesions.

Slit Orifice Aortic Cusp Extension Technique for Small Bicuspid Valves.

We describe a modification to the aortic cusp extension technique that eliminates aortic regurgitation in pediatric small bicuspid valves. This simple and reproducible cusp extension technique secures coaptation and commissure suspension of the reconstructed aortic valve and may act as a bridge option for forthcoming reoperations.

Geometric description for the anatomy of the mitral valve: A review.

The mitral valve is a complex anatomical structure whose physiological functioning relies on the biomechanical properties and structural integrity of its components. Their compromise can lead to mitral valve dysfunction, associated with morbidity and mortality. Therefore, a review on the morphometry of the mitral valve is crucial, more specifically on the importance of valve dimensions and shape for its function. This review initially provides a brief background on the anatomy and physiology of the mitral valve, followed by an analysis of the morphological information available. A characterisation of mathematical descriptions of several parts of the valve is performed and the impact of different dimensions and shape changes in disease is then outlined. Finally, a section regarding future directions and recommendations for the use of morphometric information in clinical analysis of the mitral valve is presented.

The aortic root hexagon as an aide memoire to the important surgical landmarks.

BACKGROUND: The anatomy of the aortic root and its relationship to cardiac landmarks is important for valve-sparing surgery and understanding the pathology of lesions arising in this structure. Rapid understanding of the key anatomical details can be achieved by a geometrical concept based on the shape of a hexagon. METHODS: Definitions, structure, and key anatomical concepts of the aortic root according to the current literature were reviewed. Thirty pig hearts were dissected to explore the relationships of the six points on the aortic root. Six double 2/0 ethibond needles were placed into the six points at 90°. The passage of the needles through the specific cardiac landmarks at each point was noted. The aortic root hexagon is a geometrical structure formed by two triangles superimposed on each other. The six points in the hexagon relate to important adjacent cardiac landmarks. RESULTS: The two best-known anatomical relationships are of the left-non coronary aortic commissure to the longitudinal axis of symmetry of the aortic leaflet of the mitral valve and the relationship of the nadir of the noncoronary aortic valve leaflet to the medial commissure of the mitral valve. The other four points are related to equally significant and well defined anatomical landmarks. CONCLUSION: The aortic root hexagon is made by two triangles superimposed on each other, these are the commissural and nadir triangles respectively. We have found this concept to be a quick way to learn and remember the key anatomical relationships of the aortic root.

Longitudinal Reference Ranges for Tricuspid Annular Plane Systolic Excursion and Mitral Annular Plane Systolic Excursion in Normally Grown Fetuses.

OBJECTIVES: The aim of this study was to construct reference ranges for fetal tricuspid annular plane systolic excursion (TAPSE) and mitral annular plane systolic excursion (MAPSE) using conventional M-mode ultrasound (US) in the second half of pregnancy. METHODS: Participants underwent US scans every 4 weeks from 18 weeks' gestation until delivery. The TAPSE and MAPSE were measured by conventional M-mode US at each examination. The relationships between TAPSE and MAPSE and gestational age and estimated fetal weight were modeled by Bayesian mixed effects linear regression. RESULTS: Positive linear relationships were observed between both MAPSE and TAPSE and gestational age and estimated fetal weight. Reference centiles for TAPSE and MAPSE were developed. CONCLUSIONS: This simple technique is a useful tool for assessing cardiac function and could be used for quantitative assessments of fetal cardiac function, particularly in high-risk pregnancies such as those complicated by maternal diabetes.

Reproducibility of Natural Shear Wave Elastography Measurements.

For the quantification of myocardial function, myocardial stiffness can potentially be measured non-invasively using shear wave elastography. Clinical diagnosis requires high precision. In 10 healthy volunteers, we studied the reproducibility of the measurement of propagation speeds of shear waves induced by aortic and mitral valve closure (AVC, MVC). Inter-scan was slightly higher but in similar ranges as intra-scan variability (AVC: 0.67 m/s (interquartile range [IQR]: 0.40-0.86 m/s) versus 0.38 m/s (IQR: 0.26-0.68 m/s), MVC: 0.61 m/s (IQR: 0.26-0.94 m/s) versus 0.26 m/s (IQR: 0.15-0.46 m/s)). For AVC, the propagation speeds obtained on different day were not statistically different (p = 0.13). We observed different propagation speeds between 2 systems (AVC: 3.23-4.25 m/s [Zonare ZS3] versus 1.82-4.76 m/s [Philips iE33]), p = 0.04). No statistical difference was observed between observers (AVC: p = 0.35). Our results suggest that measurement inaccuracies dominate the variabilities measured among healthy volunteers. Therefore, measurement precision can be improved by averaging over multiple heartbeats.

Analysis of a coupled fluid-structure interaction model of the left atrium and mitral valve.

We present a coupled left atrium-mitral valve model based on computed tomography scans with fibre-reinforced hyperelastic materials. Fluid-structure interaction is realised by using an immersed boundary-finite element framework. Effects of pathological conditions, eg, mitral valve regurgitation and atrial fibrillation, and geometric and structural variations, namely, uniform vs non-uniform atrial wall thickness and rule-based vs atlas-based fibre architectures, on the system are investigated. We show that in the case of atrial fibrillation, pulmonary venous flow reversal at late diastole disappears, and the filling waves at the left atrial appendage orifice during systole have reduced magnitude. In the case of mitral regurgitation, a higher atrial pressure and disturbed flows are seen, especially during systole, when a large regurgitant jet can be found with the suppressed pulmonary venous flow. We also show that both the rule-based and atlas-based fibre defining methods lead to similar flow fields and atrial wall deformations. However, the changes in wall thickness from non-uniform to uniform tend to underestimate the atrial deformation. Using a uniform but thickened wall also lowers the overall strain level. The flow velocity within the left atrial appendage, which is important in terms of appendage thrombosis, increases with the thickness of the left atrial wall. Energy analysis shows that the kinetic and dissipation energies of the flow within the left atrium are altered differently by atrial fibrillation and mitral valve regurgitation, providing a useful indication of the atrial performance in pathological situations.

Three-Dimensional Printing and Transesophageal Echocardiographic Imaging of Patient-Specific Mitral Valve Models in a Pulsatile Phantom Model.

Three-dimensional printing is increasingly used in the health care industry. Making patient-specific anatomic task trainers has been one of the more commonly described uses of this technique specifically, allowing surgeons to perform complex procedures on patient-specific models in a nonoperative setting. With regard to transesophageal echocardiography (TEE) training, commercially available simulators have been increasingly used. Even though these simulators are haptic in nature and anatomically near realistic, they lack patient specificity and the training of the dynamic workflow and imaging protocol used in the operative setting. Herein a customized pulsatile left-sided heart model that uses patient-specific 3-dimensional printed valves under physiological intracardiac pressures as a TEE task trainer is described. With this model, dynamic patient-specific valvular anatomy can be visualized with actual TEE machines by trainees to familiarize themselves with the surgery equipment and the imaging protocol.