Anterior Leaflet Of Tricuspid Valve Research Articles

Surgical Treatment of Unusual Anatomy of the Tricuspid Valve in Ebstein’s Anomaly

Ebstein’s anomaly is a congenital heart disease in which the septal and posterior leaflets of the tricuspid valve are displaced to the apex of the right ventricle, forming its atrialization. In contrast, the anatomical position of the anterior leaflet usually remains normal. The aim. To present and analyze a case of surgical treatment of Ebstein’s anomaly with a rare anatomy – isolated displacement of the anterior leaflet of the tricuspid valve. Case report. We present a rare clinical case of isolated displacement of the anterior leaflet of the tricuspid valve into the right ventricular cavity with the formation of a right atrial aneurysm. The diagnosis was made prenatally and confirmed after the birth of the child by echocardiography. Surgical intervention was postponed and successfully performed at the age of six years due to the progression of tricuspid insufficiency and increase in the right atrial aneurysm. We achieved a reduction in the size of the right atrium (diameter 31 mm, volume 25 ml and area 10 cm2) and minimized insufficiency at the tricuspid valve. The total duration of the surgical intervention was 270 minutes. The intra- and postoperative periods were uneventful. The duration of the patient’s stay in the intensive care unit was 4 days. We believe that this pathology of the anterior leaflet of the tricuspid valve should be interpreted as a variant of Ebstein’s anomaly. Conclusion. Isolated tricuspid valve anterior leaflet displacement with right atrial aneurysm is amenable to surgical correction with good immediate and long-term results.

An Animal Model of Functional Tricuspid Regurgitation by Leaflet Tethering Using Image-Guided Chordal Encircling Snares.

Several interventional therapies are in development to treat functional tricuspid regurgitation. Most have failed to achieve adequate efficacy, as animal models of this lesion are lacking. We developed a new image-guided technique in swine, by tethering the tricuspid valve chordae using echo-guided chordal encircling snares. Five swine underwent baseline echocardiographic assessment of tricuspid valve function, followed by echo-guided placement of snares that encircle the chordae inserting into the anterior and posterior tricuspid valve leaflets. Tethering these snares and stabilizing them on the right ventricle caused the regurgitant fraction to increase from 8.48±5.38% to 48.76±12.5%, and the valve tenting area to increase from 60.26±52.19 to 160.9±86.92 mm2. Image-guided chordal encircling snares could reproducibly induce clinically significant levels of functional tricuspid regurgitation and create a valve geometry like that seen in patients, providing a new animal model for use to study novel interventional devices.

1993. Serratia is a rare cause for Infective Endocarditis of the Tricuspid Valve

Abstract Background Serratia marcescens is a Gram-negative motile bacillus that is a facultative anaerobe and non-lactose fermenting. Serratia can be isolated from water, soil, plants, and the intestinal microbiome. Serratia produces a unique Identifying reddish pigment called prodigiosin. Serratia is responsible for only 0.14% of infective endocarditis cases, with a mortality rate of 85%. Methods A 37 YO female with a history of Intravenous heroin abuse was admitted with fevers and dyspnea. Vital signs were BP 76/50, HR 140, RR 26, temp 102 F, and SpO2 98% on room air. She was toxic-appearing. Labs: WBC 26000(4,000 – 11,000 /uL) with 14% bands, Hb 5.6 (12.6 – 17.0 g/dL), PLT 15*10^3(150-372*10^3/uL), creatinine 2.5 (0.50 - 1.60 mg/dL), lactic acid 15.8 (0.5-2.2 mmol/L). We started vancomycin, piperacillin-tazobactam, and norepinephrine for septic shock. A transthoracic echo showed a large mass on the tricuspid valve, and a transesophageal echo depicted it as vegetation. Blood cultures grew Serratia. She underwent excision of anterior and posterior tricuspid valve leaflets with reconstruction and ring annuloplasty. She reported washing her syringes with tab water and reusing them again. Serratia has a predilection for left-side heart valves even in the IVDU population but this patient presented with a tricuspid valve endocarditis. Results Serratia is a rare cause for IE in the ICE study; out of 2.761 definite IE cases identified over five years, only forty-nine instances were due to gram-negative bacilli. Of those, only four cases were due to Serratia. The clinical presentation of Serratia includes constitutional symptoms, new-onset murmur, and cutaneous and neurologic manifestations. Serratia produces multiple pathogenic factors allowing Serratia to result in valvular destruction and perivalvular complications, and distant septic emboli metastasis. Conclusion Serratia is sensitive to third and fourth-generation cephalosporins, monobactams, carbapenems, fluoroquinolones, and aminoglycosides. Treatment is complex due to the production of AmpC B-lactamase, which hydrolyzes third and fourth-generation cephalosporins. The 2005 IDSA suggested a combination of B-lactam and an aminoglycoside for Serratia endocarditis, and these are not guidelines but merely recommendations. Disclosures All Authors: No reported disclosures.

A Physics-Guided Neural Operator Learning Approach to Model Biological Tissues From Digital Image Correlation Measurements.

We present a data-driven workflow to biological tissue modeling, which aims to predict the displacement field based on digital image correlation (DIC) measurements under unseen loading scenarios, without postulating a specific constitutive model form nor possessing knowledge of the material microstructure. To this end, a material database is constructed from the DIC displacement tracking measurements of multiple biaxial stretching protocols on a porcine tricuspid valve anterior leaflet, with which we build a neural operator learning model. The material response is modeled as a solution operator from the loading to the resultant displacement field, with the material microstructure properties learned implicitly from the data and naturally embedded in the network parameters. Using various combinations of loading protocols, we compare the predictivity of this framework with finite element analysis based on three conventional constitutive models. From in-distribution tests, the predictivity of our approach presents good generalizability to different loading conditions and outperforms the conventional constitutive modeling at approximately one order of magnitude. When tested on out-of-distribution loading ratios, the neural operator learning approach becomes less effective. To improve the generalizability of our framework, we propose a physics-guided neural operator learning model via imposing partial physics knowledge. This method is shown to improve the model's extrapolative performance in the small-deformation regime. Our results demonstrate that with sufficient data coverage and/or guidance from partial physics constraints, the data-driven approach can be a more effective method for modeling biological materials than the traditional constitutive modeling.

Biomechanical phenotyping of minuscule soft tissues: An example in the rodent tricuspid valve

The biomechanical phenotype of soft tissues – i.e., the sum of spatially- and directionally-varying mechanical properties – is a critical marker of tissue health and disease. While biomechanical phenotyping is always challenging, it is particularly difficult with minuscule tissues. For example, tissues from small animal models are often only millimeters in size, which prevents the use of traditional test methods, such as uniaxial tensile testing. To overcome this challenge, our current work describes and tests a novel experimental and numerical pipeline. First, we introduce a micro-bulge test device with which we pressurize and inflate minuscule soft tissues. We combine this micro-bulge device with an optical coherence tomography device to also image the samples during inflation. Based on pressure data and images we then perform inverse finite element simulations to identify our tissues’ unknown material parameters. For validation, we identify the material parameters of a thin sheet of latex rubber via both uniaxial tensile testing and via our novel pipeline. Next, we demonstrate our pipeline against anterior tricuspid valve leaflets from rats. The resulting material parameters for these tissues compare excellently with data collected in sheep via standard planar biaxial testing. Additionally, we show that our device is compatible with other imaging modalities such as 2-Photon microscopy. To this end, we image the in-situ microstructural changes of the leaflets during inflation using second-harmonic generation imaging. In summary, we introduce a novel pipeline to biomechanically phenotype minuscule soft tissues and demonstrate its value by phenotyping the biomechanics of the anterior tricuspid valve leaflets from rats.

Help Wanted: New Options for Tricuspid Valve Repair

We refer to the tricuspid as the “forgotten valve,” and when the results of repair are reviewed, one can understand why surgeons want to forget it1 because of frequent recurrent tricuspid regurgitation (TR). Recurrent moderate or more functional TR is frequently in a range similar to the results with mitral repair with functional mitral regurgitation.2 Most treated TR is functional related to left-sided valve disease and is treated with a suture, band, or ring annuloplasty. Patch enlargement of the anterior tricuspid valve leaflet has been described but is time consuming and not easily reproducible.

Neonatal Rupture of the Tricuspid Valve and Maternal Lupus: Is There a Correlation?

Valve dysfunction is not widely recognized as a feature in newborns born to mothers with positive anti-Ro/SSA antibodies, and only scarce reports have suggested an association between rupture of the atrioventricular valve tensor apparatus and these maternal antibodies. We report the follow-up from fetal life to the time of postnatal surgery of a patient with severe tricuspid regurgitation due to a flail of the anterior tricuspid valve leaflet who was born to an anti-Ro/SSA antibodies positive mother.

Transcatheter ablation of the atrioventricular junction in refractory atrial fibrillation: A clinicopathological study

BackgroundCatheter ablation of the specialized atrioventricular junction (AVJ) with a right-side approach is an effective therapy for refractory atrial fibrillation with fast ventricular rate. Our aim is to assess the efficacy of the procedure in a single center experience and investigate the histologic findings of AVJ after catheter ablation. MethodsA) Analysis of AVJ ablation efficacy in a consecutive series of patients with refractory atrial fibrillation; B) Histopathologic study of the conduction system by serial section technique and clinical-electrophysiologic correlation in four patients who underwent AVJ ablation. ResultsA) Right-sided AVJ ablation was successful in all 87 consecutive patients (mean procedural time 19.2±17.9 min). Energy applications ranged from 1 to 27 (mean 5.8±5.1) with eight patients (9%) requiring > 15 applications. B) Fibrotic disruption of atrioventricular (AV) node and/or His bundle interruption was found in three cases with previous AVJ ablation. In the case requiring a left side approach, the compact AV node and common His bundle appeared undamaged whereas extensive fibrosis of the summit of the ventricular septum, branching His bundle and proximal bundle branches was found. Noteworthy, a continuity between the septal and anterior tricuspid valve leaflets was present. ConclusionOur data confirm that the ideal site for ablation of the specialized AVJ is the AV node. In selected cases with unsuccessful AV node ablation, a shift towards the His bundle is needed. A continuity between the septal and anterior leaflets of the tricuspid valve may protect the His bundle as to require multiple shocks and prolong the procedure.

Tricuspid Valve Anterior Leaflet Strains in Ovine Functional Tricuspid Regurgitation

Functional tricuspid regurgitation (FTR) is thought to arise due to annular dilation and alteration of right ventricular (RV) geometry in the presence of normal leaflets, yet mitral leaflets have been shown to remodel significantly in functional mitral regurgitation. We set out to evaluate tricuspid valve anterior leaflet deformations in ovine FTR. Eleven animals (FTR group) underwent implantation of a pacemaker with high rate pacing to induce biventricular dysfunction and at least moderate TR. Subsequently, both FTR (n = 11) and Control (n = 12) animals underwent implantation of 6 sonomicrometry crystals around the tricuspid annulus, 4 on the anterior leaflet, and 14 on RV epicardium. Tricuspid valve geometry and anterior leaflet strains were calculated from crystal coordinates. Left ventricular ejection fraction and RV fractional area change were significantly lower in FTR animals versus Control. Tricuspid annular area, septo-lateral diameter, RV pressures were all significantly greater in the FTR group. Mean TR grade (+0-3) was 0.7 ± 0.5 in Control and 2.4 ± 0.5 in FTR (P = < 0.001). The anterior leaflet area and length increased significantly. Global radial leaflet strain was significantly lower in FTR mostly driven by decreased free edge leaflet strain. Global circumferential anterior leaflet strain was also significantly lower in FTR with more remarkable reduction in the belly region. Rapid ventricular pacing in sheep resulted in a clinically pertinent model of RV and annular dilation with FTR and leaflet enlargement. Both circumferential and radial anterior leaflet strains were significantly reduced with FTR. Functional TR may be associated with alteration of leaflet mechanical properties.

Tricuspid Valve Annuloplasty Alters Leaflet Mechanics.

Tricuspid valve regurgitation is associated with significant morbidity and mortality. Its most common treatment option, tricuspid valve annuloplasty, is not optimally effective in the long-term. Toward identifying the causes for annuloplasty's ineffectiveness, we have previously investigated the technique's impact on the tricuspid annulus and the right ventricular epicardium. In our current work, we are extending our analysis to the anterior tricuspid valve leaflet. To this end, we adopted our previous strategy of performing DeVega suture annuloplasty as an experimental methodology that allows us to externally control the degree of cinching during annuloplasty. Thus, in ten sheep we successively cinched the annulus and quantified changes to leaflet motion, dynamics, and strain in the beating heart by combining sonomicrometry with our well-established mechanical framework. We found that successive cinching of the valve enforced earlier coaptation and thus reduced leaflet range of motion. Additionally, leaflet angular velocity during opening and closing decreased. Finally, we found that leaflet strains were also reduced. Specifically, radial and areal strains decreased as a function of annular cinching. Our findings are critical as they suggest that suture annuloplasty alters the mechanics of the tricuspid valve leaflets which may disrupt their resident cells' mechanobiological equilibrium. Long-term, such disruption may stimulate tissue maladaptation which could contribute to annuloplasty's sub-optimal effectiveness. Additionally, our data suggest that the extent to which annuloplasty alters leaflet mechanics can be controlled via degree of cinching. Hence, our data may provide direct surgical guidelines.

P1299 Right sided infective endocarditis with paradoxical embolization

Abstract Background Right sided infective endocarditis (IE) accounts for 5-10% of IE cases, systemic embolization is uncommon and if present it is linked to the presence of shunt or concomitant left sided IE. Clinical presentation A 35-years old gentleman with history of heroin intravenous drug abuse (IV), presented with a history of unexplained fever for two weeks along with exertional dyspnea, productive cough, chest pain and severe left hypochondria pain. On examination he had a blood pressure of 130/80 mmHg, a heart rate of 130 bpm, a temperature of 40oC, elevated jugular venous pressure and a harsh pansystolic murmur over the lower left sternal border. Laboratory results revealed anaemia, leukocytosis elevated ESR and CRP and blood cultures were positive for methicillin-resistant staphylococcus aureus (MRSA), electrocardiography showed sinus tachycardia and abdomen computed tomography scan revealed multiple splenic infarctions. Methods and results 2D&amp;3DTrans-Thoracic Echocardiography (TTE) revealed the presence of an echogenic elongated highly mobile mass measures 2.0 cm in maximum dimension attached to the atrial surface of the anterior tricuspid valve leaflet a long with severe valvular regurgitation. Patent foramen ovale (PFO) was visualized by Color Doppler and right to left shunt was confirmed by contrast study with a complete opacification of the left side. The left ventricle dimensions were normal , there was an evidence of hyokinesis of inter-ventricular septum (IVS) and inferior wall and function was reduced, estimated LVEF = 45%. Hence, coronary angiography was done and revealed normal coronaries. 3D Trans-esophageal Echocardiography(TEE) was done for better visualization of the interatrial septum (IAS), vegetation and to rule out complications. The study confirmed the presence of PFO, there was no concomitant IAS defects, the vegetation is highly mobile and facing the IAS. Accordingly, patient was diagnosed with tricuspid infective endocarditis complicated with paradoxical embolization, anti-biotics were commenced and patient underwent successful tricuspid valve replacement and PFO closure. Discussion Tricuspid valve endocarditis has been linked to IV drug abuse and staphylococcus aureus has been recognized as the most commonly implicated organism. While systemic emboli are rare in right sided IE, our patient represent this uncommon complication. He had multiple splenic infractions and TTE contrast study showed PFO with a high degree of right to left shunt. Coronary embolization was a suspect in our patient as well given the presence of regional wall motion abnormalities involving the left ventricle inferior wall and IVS. Conclusion Echocardiography is a crucial imaging modality in patient with long standing fever and history of IV drug abuse to rule out infective endocarditis. 3D-TEE is of added value along with TTE in better definition of vegetations and detection of infective endocarditis complication. Abstract P1299 Figure. Tricuspid valve infective endocarditis

An investigation of the effect of freezing storage on the biaxial mechanical properties of excised porcine tricuspid valve anterior leaflets

The atrioventricular heart valve (AHV) leaflets are critical to the facilitation of proper unidirectional blood flow through the heart. Previously, studies have been conducted to understand the tissue mechanics of healthy AHV leaflets to inform the development of valve-specific computational models and replacement materials for use in diagnosing and treating valvular heart disease. Generally, these studies involved biaxial mechanical testing of the AHV leaflet tissue specimens to extract relevant mechanical properties. Most of those studies considered freezing-based storage systems based on previous findings for other connective tissues such as aortic tissue or skin. However, there remains no study that specifically examines the effects of freezing storage on the characterized mechanical properties of the AHV leaflets. In this study, we aimed to address this gap in knowledge by performing biaxial mechanical characterizations of the tricuspid valve anterior leaflet (TVAL) tissue both before and after a 48-h freezing period. Primary findings of this study include: (i) a statistically insignificant change in the tissue extensibilities, with the frozen tissues being slightly stiffer and more anisotropic than the fresh tissues; and (ii) minimal variations in the stress relaxation behaviors between the fresh and frozen tissues, with the frozen tissues demonstrating slightly lessened relaxation. The findings from this study suggested that freezing-based storage does not significantly impact the observed mechanical properties of one of the five AHV leaflets—the TVAL. The results from this study are useful for reaffirming the experimental methodologies in the previous studies, as well as informing the tissue preservation methods of future investigations of AHV leaflet mechanics.

Mechanical Response Changes in Porcine Tricuspid Valve Anterior Leaflet Under Osmotic-Induced Swelling.

Since many soft tissues function in an isotonic in-vivo environment, it is expected that physiological osmolarity will be maintained when conducting experiments on these tissues ex-vivo. In this study, we aimed to examine how not adhering to such a practice may alter the mechanical response of the tricuspid valve (TV) anterior leaflet. Tissue specimens were immersed in deionized (DI) water prior to quantification of the stress–strain responses using an in-plane biaxial mechanical testing device. Following a two-hour immersion in DI water, the tissue thickness increased an average of 107.3% in the DI water group compared to only 6.8% in the control group, in which the tissue samples were submerged in an isotonic phosphate buffered saline solution for the same period of time. Tissue strains evaluated at 85 kPa revealed a significant reduction in the radial direction, from 34.8% to 20%, following immersion in DI water. However, no significant change was observed in the control group. Our study demonstrated the impact of a hypo-osmotic environment on the mechanical response of TV anterior leaflet. The imbalance in ions leads to water absorption in the valvular tissue that can alter its mechanical response. As such, in ex-vivo experiments for which the native mechanical response of the valves is important, using an isotonic buffer solution is essential.

An investigation of the glycosaminoglycan contribution to biaxial mechanical behaviours of porcine atrioventricular heart valve leaflets.

The atrioventricular heart valve (AHV) leaflets have a complex microstructure composed of four distinct layers: atrialis, ventricularis, fibrosa and spongiosa. Specifically, the spongiosa layer is primarily proteoglycans and glycosaminoglycans (GAGs). Quantification of the GAGs' mechanical contribution to the overall leaflet function has been of recent focus for aortic valve leaflets, but this characterization has not been reported for the AHV leaflets. This study seeks to expand current GAG literature through novel mechanical characterizations of GAGs in AHV leaflets. For this characterization, mitral and tricuspid valve anterior leaflets (MVAL and TVAL, respectively) were: (i) tested by biaxial mechanical loading at varying loading ratios and by stress-relaxation procedures, (ii) enzymatically treated for removal of the GAGs and (iii) biaxially mechanically tested again under the same protocols as in step (i). Removal of the GAG contents from the leaflet was conducted using a 100 min enzyme treatment to achieve approximate 74.87% and 61.24% reductions of all GAGs from the MVAL and TVAL, respectively. Our main findings demonstrated that biaxial mechanical testing yielded a statistically significant difference in tissue extensibility after GAG removal and that stress-relaxation testing revealed a statistically significant smaller stress decay of the enzyme-treated tissue than untreated tissues. These novel findings illustrate the importance of GAGs in AHV leaflet behaviour, which can be employed to better inform heart valve therapeutics and computational models.

An investigation of layer-specific tissue biomechanics of porcine atrioventricular valve anterior leaflets

Atrioventricular heart valves (AHVs) are composed of structurally complex and morphologically heterogeneous leaflets. The coaptation of these leaflets during the cardiac cycle facilitates unidirectional blood flow. Valve regurgitation is treated preferably by surgical repair if possible or replacement based on the disease state of the valve tissue. A comprehensive understanding of valvular morphology and mechanical properties is crucial to refining computational models, serving as a patient-specific diagnostic and surgical tool for preoperative planning. Previous studies have modeled the stress distribution throughout the leaflet’s thickness, but validations with layer-specific biaxial mechanical experiments are missing. In this study, we sought to fill this gap in literature by investigating the impact of microstructure constituents on mechanical behavior throughout the thickness of the AHVs’ anterior leaflets. Porcine mitral valve anterior leaflets (MVAL) and tricuspid valve anterior leaflets (TVAL) were micro-dissected into three layers (atrialis/spongiosa, fibrosa, and ventricular) and two layers (atrialis/spongiosa and fibrosa/ventricularis), respectively, based on their relative distributions of extracellular matrix components as quantified by histological analyses: collagen, elastin, and glycosaminoglycans. Our results suggest that (i) for both valves, the atrialis/spongiosa layer is the most extensible and anisotropic layer, possibly due to its relatively low collagen content as compared to other layers, (ii) the intact TVAL response is stiffer than the atrialis/spongiosa layer but more compliant than the fibrosa/ventricularis layer, and (iii) the MVAL fibrosa and ventricularis layers behave nearly isotropic. These novel findings emphasize the biomechanical variances throughout the AHV leaflets, and our results could better inform future AHV computational model developments. Statement of SignificanceThis study, which is the first of its kind for atrioventricular heart valve (AHV) leaflet tissue layers, rendered a mechanical characterization of the biaxial mechanical properties and distributions of extracellular matrix components (collagen, elastin, and glycosaminoglycans) of the mitral and tricuspid valve anterior leaflet layers. The novel findings from the present study emphasize the biomechanical variances throughout the thickness of AHV leaflets, and our results indicate that the previously-adopted homogenous leaflet in the AHV biomechanical modeling may be an oversimplification of the complex leaflet anatomy. Such improvement in the understanding of valvular morphology and tissue mechanics is crucial to future refinement of AHV computational models, serving as a patient-specific diagnostic and surgical tool, at the preoperative stage, for treating valvular heart diseases.

A computational multi-scale approach to investigate mechanically-induced changes in tricuspid valve anterior leaflet microstructure

The tricuspid valve is an atrioventricular valve that prevents blood backflow from the right ventricle into the right atrium during ventricular contractions. It is important to study mechanically induced microstructural alterations in the tricuspid valve leaflets, as this aids both in understanding valvular diseases and in the development of new engineered tissue replacements. The structure and composition of the extracellular matrix (ECM) fiber networks are closely tied to an overall biomechanical function of the tricuspid valve. In this study, we conducted experiments and implemented a multiscale modeling approach to predict ECM microstructural changes to tissue-level mechanical responses in a controlled loading environment. In particular, we characterized a sample of a porcine anterior leaflet at a macroscale using a biaxial mechanical testing method. We then generated a three-dimensional finite element model, to which computational representations of corresponding fiber networks were incorporated based on properties of the microstructural architecture obtained from small angle light scattering. Using five different biaxial boundary conditions, we performed iterative simulations to obtain model parameters with an overall R2 value of 0.93. We observed that mechanical loading could markedly alter the underlying ECM architecture. For example, a relatively isotropic fiber network (with an anisotropy index value α of 28%) became noticeably more anisotropic (with an α of 40%) when it underwent mechanical loading. We also observed that the mechanical strain was distributed in a different manner at the ECM/fiber level as compared to the tissue level. The approach presented in this study has the potential to be implemented in pathophysiologically altered biomechanical and structural conditions and to bring insights into the mechanobiology of the tricuspid valve. Statement of SignificanceQuantifying abnormal cellar/ECM-level deformation of tricuspid valve leaflets subjected to a modified loading environment is of great importance, as it is believed to be linked to valvular remodeling responses. For example, developing surgical procedures or engineered tissue replacements that maintain/mimic ECM-level mechanical homeostasis could lead to more durable outcomes. To quantify leaflet deformation, we built a multiscale framework encompassing the contributions of disorganized ECM components and organized fibers, which can predict the behavior of the tricuspid valve leaflets under physiological loading conditions both at the tissue level and at the ECM level. In addition to future in-depth studies of tricuspid valve pathologies, our model can be used to characterize tissues in other valves of the heart.

An Investigation of Layer-Specific Tissue Biomechanics of Porcine Atrioventricular Valve Anterior Leaflets

The atrioventricular heart valves (AHVs) are composed of structurally complex and morphologically heterogeneous leaflets. The coaptation of these leaflets during the cardiac cycle facilitates unidirectional blood flow and prevents regurgitation. Valve regurgitation is treated preferably by surgical repair if possible or replacement based on the disease state of the valve tissue. A comprehensive understanding of valvular morphology and mechanical properties is crucial to refining computational models, serving as a patient-specific diagnostic and surgical tool for preoperative planning. Previous studies have modeled the stress distribution throughout the thickness of the heterogeneous leaflet, but validations with layer-specific biaxial mechanical experiments are missing. In this study, we sought to fill this gap in literature by investigating the impact of microstructure constituents on mechanical behavior throughout the thickness of the AHVs’ anterior leaflets. Porcine mitral valve anterior leaflets (MVAL) and tricuspid valve anterior leaflets (TVAL) were micro-dissected into 3 layers (atrialis/spongiosa, fibrosa, and ventricular) and 2 layers (atrialis/spongiosa and fibrosa/ventricularis), respectively, based on their relative distributions of extracellular matrix (ECM) components as quantified by histological analyses: collagen, elastin, and glycosaminoglycans. Our results suggest that: (i) the atrialis/spongiosa layer, for both valves, is the most extensible and anisotropic layer, (ii) the intact TVAL response is stiffer than the atrialis/spongiosa layer but more compliant than the fibrosa/ventricularis layer, and (iii) the MVAL fibrosa and ventricularis layers behave nearly isotropic. These novel findings emphasize the biomechanical variances throughout the AHV leaflets, and our results will be useful to better inform AHV computational models.

Biventricular mural vegetations without valvular involvement: an unusual presentation of Staphylococcus aureus endocarditis

SummaryA 42-year-old intravenous drug user presented with seizures and septicaemia. CT and MRI were suggestive of multiple brain and systemic emboli, and blood and CSF cultures were positive for Staphylococcus aureus. Initial transthoracic echocardiogram did not show any abnormalities but subsequent transoesophageal echocardiography showed two masses in the left and the right ventricle. The LV mass was large, irregular, non-mobile and attached to the basal anterolateral LV segment abutting but not involving the mitral valve. (Fig. 1). The RV mass was smaller and mobile and appeared attached to the primary chordae of anterior tricuspid valve leaflet, not encroaching the valve or affecting its function (Fig. 2). Once commenced on antibiotic treatment the patient’s condition improved, and there were no further embolic events. There was no valvular damage and sequential echo studies showed significant reduction in vegetation size. Although the formal echocardiographic definition of vegetation includes non-oscillating masses on any endocardial surface (1), primary mural endocarditis without valvular involvement is considered extremely rare (2). The diagnosis is supported by the septic and embolic clinical picture but requires awareness of this uncommon presentation. The present case is even more unusual in view of the biventricular mural localisation of the vegetations, a pattern that has been mentioned in only very few case reports (3, 4).

An investigation of regional variations in the biaxial mechanical properties and stress relaxation behaviors of porcine atrioventricular heart valve leaflets

The facilitation of proper blood flow through the heart depends on proper function of heart valve components, and alterations to any component can lead to heart disease or failure. Comprehension of these valvular diseases is reliant on thorough characterization of healthy heart valve structures for use in computational models. Previously, computational models have treated these leaflet structures as a structurally and mechanically homogenous material, which may not be an accurate description of leaflet mechanical response. In this study, we aimed to characterize the mechanics of the heart valve leaflet as a structurally heterogenous material. Specifically, porcine mitral valve and tricuspid valve anterior leaflets were sectioned into six regions and biaxial mechanical tests with various loading ratios and stress-relaxation test were performed on each regional tissue sample. Three main findings from this study were summarized as follows: (i) the central regions of the leaflet had a more anisotropic nature than edge regions, (ii) the mitral valve anterior leaflet was more extensible in regions closer to the annulus, and (iii) there was variance in the stress-relaxation behavior among all six regions, with mitral valve leaflet tissue regions exhibiting a greater decay than the tricuspid valve regions. This study presents a novel investigation of the regional variations in the heart valve biomechanics that has not been comprehensively examined. Our results thus allow for a refinement of computational models for more accurately predicting diseased or surgically-intervened condition, where tissue heterogeneity plays an essential role in the heart valve function.

Uhl's anomaly: Clinical spectrum and pathophysiology

A 28 year-old woman from Afghanistan was referred for prenatal evaluation. She and her husband were consanguineous and had a previous female baby with a rare congenital cardiac defect that consisted of Uhl's anomaly, Ebstein's malformation and pulmonary atresia. The child died after the first palliative step towards a Fontan circulation. A fetal echocardiogram performed at 18 + 2 weeks' gestation showed distinctive right-sided cardiac abnormalities similar to those found in their previous daughter. A dilated, extremely thin walled right ventricle (RV) with poor systolic function was found with a markedly dysplastic tricuspid valve (Fig. 1A, Video 1). There appeared only to be a rudimentary anterior tricuspid valve leaflet. The tricuspid orifice was larger than the mitral valve annulus, 4.9 mm (Z-score +1.5) and 3.6 mm (Z-score -1.5) respectively [1] and free regurgitation through the rudimentary tricuspid valve was present. The oval fossa was wide open with right to left shunting over it (Fig. 1A–B, Video 2). The pulmonary valve annulus diameter was small (2.3 mm, Z-score -0.9) and the pulmonary arteries were underdeveloped (Fig. 1E). The left side of the heart appeared structurally normal (Fig. 1A–C) with normal aortic annulus dimension (3.0 mm, Z-score +2.9). No prograde flow could be detected over