Multiscale Structure and Function of the Aortic Valve Apparatus.

While studying the aortic valve in isolation has facilitated the development of life-saving procedures and technologies, the dynamic interplay of the aortic valve and its surrounding structures is vital to preserving their function across the wide range of conditions encountered in an active lifestyle. Our view is that these structures should be viewed as an integrated functional unit, herein referred to as the aortic valve apparatus (AVA). The coupling of the aortic valve and root, left ventricular outflow tract, and blood circulation is crucial for AVA's functions: unidirectional flow out of the left ventricle, coronary perfusion, reservoir function, and supporting left ventricular function. In this review, we explore the multiscale biological and physical phenomena that underly the simultaneous fulfilment of these functions. A brief overview of the tools used to investigate the AVA is included, such as: medical imaging modalities, experimental methods, and computational modelling, specifically fluid-structure interaction (FSI) simulations, is included. Some pathologies affecting the AVA are explored, and insights are provided on treatments and interventions that aim to maintain quality of life. The concepts explained in this paper support the idea of AVA being an integrated functional unit and help identify unanswered research questions. Incorporating phenomena through the molecular, micro, meso and whole tissue scales is crucial for understanding the sophisticated normal functions and diseases of the AVA.

Whole-exome sequencing uncovers the genetic complexity of bicuspid aortic valve in families with early-onset complications.

Bicuspid aortic valve (BAV) is the most common congenital heart lesion with an estimated population prevalence of 1%. We hypothesize that specific gene variants predispose to early-onset complications of BAV (EBAV). We analyzed whole-exome sequences (WESs) to identify rare coding variants that contribute to BAV disease in 215 EBAV-affected families. Predicted damaging variants in candidate genes with moderate or strong supportive evidence to cause developmental cardiac phenotypes were present in 107 EBAV-affected families (50% of total), including genes that cause BAV (9%) or heritable thoracic aortic disease (HTAD, 19%). After appropriate filtration, we also identified 129 variants in 54 candidate genes that are associated with autosomal-dominant congenital heart phenotypes, including recurrent deleterious variation of FBN2, MYH6, channelopathy genes, and type 1 and 5 collagen genes. These findings confirm our hypothesis that unique rare genetic variants drive early-onset presentations of BAV disease.

Asymmetric fluid flow in helical pipes inspired by shark intestines.

Unlike human intestines, which are long, hollow tubes, the intestines of sharks and rays contain interior helical structures surrounding a cylindrical hole. One function of these structures may be to create asymmetric flow, favoring passage of fluid down the digestive tract, from anterior to posterior. Here, we design and 3D print biomimetic models of shark intestines, in both rigid and deformable materials. We use the rigid models to test which physical parameters of the interior helices (the pitch, the hole radius, the tilt angle, and the number of turns) yield the largest flow asymmetries. These asymmetries exceed those of traditional Tesla valves, structures specifically designed to create flow asymmetry without any moving parts. When we print the biomimetic models in elastomeric materials so that flow can couple to the structure's shape, flow asymmetry is significantly amplified; it is sevenfold larger in deformable structures than in rigid structures. Last, we 3D-print deformable versions of the intestine of a dogfish shark, based on a tomogram of a biological sample. This biomimic produces flow asymmetry comparable to traditional Tesla valves. The ability to influence the direction of a flow through a structure has applications in biological tissues and artificial devices across many scales, from large industrial pipelines to small microfluidic devices.

Translational control of furina by an RNA regulon is important for left-right patterning, heart morphogenesis and cardiac valve function.

Heart development is a complex process that requires asymmetric positioning of the heart, cardiac growth and valve morphogenesis. The mechanisms controlling heart morphogenesis and valve formation are not fully understood. The pro-convertase FurinA functions in heart development across vertebrates. How FurinA activity is regulated during heart development is unknown. Through computational analysis of the zebrafish transcriptome, we identified an RNA motif in a variant FurinA transcript harbouring a long 3' untranslated region (3'UTR). The alternative 3'UTR furina isoform is expressed prior to organ positioning. Somatic deletions in the furina 3'UTR lead to embryonic left-right patterning defects. Reporter localisation and RNA-binding assays show that the furina 3'UTR forms complexes with the conserved RNA-binding translational repressor, Ybx1. Conditional ybx1 mutant embryos show premature and increased Furin reporter expression, abnormal cardiac morphogenesis and looping defects. Mutant ybx1 hearts have an expanded atrioventricular canal, abnormal sino-atrial valves and retrograde blood flow from the ventricle to the atrium. This is similar to observations in humans with heart valve regurgitation. Thus, the furina 3'UTR element/Ybx1 regulon is important for translational repression of FurinA and regulation of heart development.

Shear-Sensing by C-Reactive Protein: Linking Aortic Stenosis and Inflammation.

BACKGROUND: CRP (C-reactive protein) is a prototypical acute phase reactant. Upon dissociation of the pentameric isoform (pCRP [pentameric CRP]) into its monomeric subunits (mCRP [monomeric CRP]), it exhibits prothrombotic and proinflammatory activity. Pathophysiological shear rates as observed in aortic valve stenosis (AS) can influence protein conformation and function as observed with vWF (von Willebrand factor). Given the proinflammatory function of dissociated CRP and the important role of inflammation in the pathogenesis of AS, we investigated whether shear stress can modify CRP conformation and induce inflammatory effects relevant to AS. METHODS: To determine the effects of pathological shear rates on the function of human CRP, pCRP was subjected to pathophysiologically relevant shear rates and analyzed using biophysical and biochemical methods. To investigate the effect of shear on CRP conformation in vivo, we used a mouse model of arterial stenosis. Levels of mCRP and pCRP were measured in patients with severe AS pre- and post-transcatheter aortic valve implantation, and the presence of CRP was investigated on excised valves from patients undergoing aortic valve replacement surgery for severe AS. Microfluidic models of AS were then used to recapitulate the shear rates of patients with AS and to investigate this shear-dependent dissociation of pCRP and its inflammatory function. RESULTS: Exposed to high shear rates, pCRP dissociates into its proinflammatory monomers (mCRP) and aggregates into large particles. Our in vitro findings were further confirmed in a mouse carotid artery stenosis model, where the administration of human pCRP led to the deposition of mCRP poststenosis. Patients undergoing transcatheter aortic valve implantation demonstrated significantly higher mCRP bound to circulating microvesicles pre-transcatheter aortic valve implantation compared with post-transcatheter aortic valve implantation. Excised human stenotic aortic valves display mCRP deposition. pCRP dissociated in a microfluidic model of AS and induces endothelial cell activation as measured by increased ICAM-1 and P-selectin expression. mCRP also induces platelet activation and TGF-ß (transforming growth factor beta) expression on platelets. CONCLUSIONS: We identify a novel mechanism of shear-induced pCRP dissociation, which results in the activation of cells central to the development of AS. This novel mechanosensing mechanism of pCRP dissociation to mCRP is likely also relevant to other pathologies involving increased shear rates, such as in atherosclerotic and injured arteries.

The emerging challenge of Enterococcus faecalis endocarditis after transcatheter aortic valve implantation: time for innovative treatment approaches.

SUMMARYInfective endocarditis (IE) is a life-threatening infection that has nearly doubled in prevalence over the last two decades due to the increase in implantable cardiac devices. Transcatheter aortic valve implantation (TAVI) is currently one of the most common cardiac procedures. TAVI usage continues to exponentially rise, inevitability increasing TAVI-IE. Patients with TAVI are frequently nonsurgical candidates, and TAVI-IE 1-year mortality rates can be as high as 74% without valve or bacterial biofilm removal. Enterococcus faecalis, a historically less common IE pathogen, is the primary cause of TAVI-IE. Treatment options are limited due to enterococcal intrinsic resistance and biofilm formation. Novel approaches are warranted to tackle current therapeutic gaps. We describe the existing challenges in treating TAVI-IE and how available treatment discovery approaches can be combined with an in silico "Living Heart" model to create solutions for the future.

Practical Guidance for Clinical Microbiology Laboratories: Microbiologic diagnosis of implant-associated infections.

SUMMARYImplant-associated infections (IAIs) pose serious threats to patients and can be associated with significant morbidity and mortality. These infections may be difficult to diagnose due, in part, to biofilm formation on device surfaces, and because even when microbes are found, their clinical significance may be unclear. Despite recent advances in laboratory testing, IAIs remain a diagnostic challenge. From a therapeutic standpoint, many IAIs currently require device removal and prolonged courses of antimicrobial therapy to effect a cure. Therefore, making an accurate diagnosis, defining both the presence of infection and the involved microorganisms, is paramount. The sensitivity of standard microbial culture for IAI diagnosis varies depending on the type of IAI, the specimen analyzed, and the culture technique(s) used. Although IAI-specific culture-based diagnostics have been described, the challenge of culture-negative IAIs remains. Given this, molecular assays, including both nucleic acid amplification tests and next-generation sequencing-based assays, have been used. In this review, an overview of these challenging infections is presented, as well as an approach to their diagnosis from a microbiologic perspective.

Atorvastatin Effect on Aortic Dilatation and Valvular Calcification Progression in Bicuspid Aortic Valve (BICATOR): A Randomized Clinical Trial.

BACKGROUND: Ascending aorta dilation and aortic valve degeneration are common complications in patients with bicuspid aortic valve. Several retrospective studies have suggested the benefit of statins in reducing these complications. This study aimed to determine whether atorvastatin treatment is effective in reducing the growth of aortic diameters in bicuspid aortic valve and if it slows the progression of valve calcification. METHODS: In a randomized clinical trial, 220 patients with bicuspid aortic valve (43 women; 46±13 years of age) were included and treated with either 20 mg of atorvastatin per day or placebo for 3 years. Inclusion criteria were ≥18 years of age, nonsevere valvular dysfunction, nonsevere valve calcification, and ascending aorta diameter ≤50 mm. Computed tomography and echocardiography studies were performed at baseline and after 3 years of treatment. RESULTS: During follow-up, 28 patients (12.7%) discontinued medical treatment (15 on atorvastatin and 13 taking placebo). Thus, 192 patients completed the 36 months of treatment. Low-density lipoprotein cholesterol levels decreased significantly in the atorvastatin group (median [interquartile range], -30 mg/dL [-51.65 to -1.75 mg/dL] versus 6 mg/dL [-4, 22.5 mg/dL]; P<0.001). The maximum ascending aorta diameter increased with no differences between groups: 0.65 mm (95% CI, 0.45-0.85) in the atorvastatin group and 0.74 mm (95% CI, 0.45-1.04) in the placebo group (P=0.613). Similarly, no significant differences were found for the progression of the aortic valve calcium score (P=0.167) or valvular dysfunction. CONCLUSIONS: Among patients with bicuspid aortic valve without severe valvular dysfunction, atorvastatin treatment was not effective in reducing the progression of ascending aorta dilation and aortic valve calcification during 3 years of treatment despite a significant reduction in low-density lipoprotein cholesterol levels. REGISTRATION: URL: https://www.clinicaltrialsregister.eu; Unique identifier: 2015-001808-57. URL: https://www.clinicaltrials.gov; Unique identifier: NCT02679261.

Contemporary Outcomes and Trends for the Transseptal Mitral Valve-in-Valve Procedure Using Balloon Expandable Transcatheter Valves in the United States.

BACKGROUND: Previous transcatheter valve therapy registry analyses of transcatheter mitral valve in valve (MViV) replacement of degenerated bioprosthesis reported early experience in the United States. Given recent increases in transseptal MViV volumes and introduction of the SAPIEN 3 Ultra valve, it is important to determine contemporary outcomes for patients undergoing transseptal SAPIEN 3/SAPIEN 3 Ultra MViV replacement. METHODS: The Society of Thoracic Surgeons (STS)/American College of Cardiology Transcatheter Valve Therapy Registry was used to extract data for all patients undergoing transseptal SAPIEN 3/SAPIEN 3 Ultra MViV from 2015 to September 2022. Primary efficacy outcome was 1-year all-cause mortality. Secondary end points included 30-day mortality, functional class, quality of life, and mitral valve performance. Primary safety outcomes were device success and in-hospital complications. RESULTS: A total of 4243 patients with a mean STS score of 9.2±7.7 underwent transseptal MViV at 455 sites. The rate of Mitral Valve Academic Research Consortium technical (96.6%) success was high, and procedural complications were low. All-cause in-hospital, 30-day, and 1-year mortality rates were 3.2%, 4.3%, and 13.4%, respectively. Significant improvements in New York Heart Association class (New York Heart Association I/II, 18% to 87%) and quality of life (Kansas City Cardiomyopathy Questionnaire score, 38 to 78) were noted at 1 year (P<0.0001 for both) after MViV. Upon stratifying by STS scores, it was observed that the low-risk group (STS<4) had a significantly lower in-hospital mortality rate of 0.4%, whereas the intermediate-risk group (STS, 4-8) had an in-hospital mortality rate of 1.9%. From 2015 to 2022, the number of transseptal MViV cases/year increased significantly, whereas procedure times, length of stay, and intensive care unit hours shortened significantly. At the same time, there was a significant trend toward reduced in-hospital (P=0.0005), 30-day (P=0.004), and 1-year mortality rates (P=0.01). CONCLUSIONS: This multicenter, prospective study reports excellent procedural outcomes, 1-year mortality rates, and a significant improvement in quality of life for patients undergoing transseptal MViV in the contemporary era. Patients in the low-risk and intermediate-risk STS score categories had significantly better outcomes compared with those in the high-risk category. MViV is a reasonable therapy for the majority of patients with degenerated bioprosthetic mitral valves, who are anatomical candidates.

The Tricuspid Valve: A Review of Pathology, Imaging, and Current Treatment Options: A Scientific Statement From the American Heart Association.

Tricuspid valve disease is an often underrecognized clinical problem that is associated with significant morbidity and mortality. Unfortunately, patients will often present late in their disease course with severe right-sided heart failure, pulmonary hypertension, and life-limiting symptoms that have few durable treatment options. Traditionally, the only treatment for tricuspid valve disease has been medical therapy or surgery; however, there have been increasing interest and success with the use of transcatheter tricuspid valve therapies over the past several years to treat patients with previously limited therapeutic options. The tricuspid valve is complex anatomically, lying adjacent to important anatomic structures such as the right coronary artery and the atrioventricular node, and is the passageway for permanent pacemaker leads into the right ventricle. In addition, the mechanism of tricuspid pathology varies widely between patients, which can be due to primary, secondary, or a combination of causes, meaning that it is not possible for 1 type of device to be suitable for treatment of all cases of tricuspid valve disease. To best visualize the pathology, several modalities of advanced cardiac imaging are often required, including transthoracic echocardiography, transesophageal echocardiography, cardiac computed tomography, and cardiac magnetic resonance imaging, to best visualize the pathology. This detailed imaging provides important information for choosing the ideal transcatheter treatment options for patients with tricuspid valve disease, taking into account the need for the lifetime management of the patient. This review highlights the important background, anatomic considerations, therapeutic options, and future directions with regard to treatment of tricuspid valve disease.

Unraveling the Mechanisms of Valvular Heart Disease to Identify Medical Therapy Targets: A Scientific Statement From the American Heart Association.

Valvular heart disease is a common cause of morbidity and mortality worldwide and has no effective medical therapy. Severe disease is managed with valve replacement procedures, which entail high health care-related costs and postprocedural morbidity and mortality. Robust ongoing research programs have elucidated many important molecular pathways contributing to primary valvular heart disease. However, there remain several key challenges inherent in translating research on valvular heart disease to viable molecular targets that can progress through the clinical trials pathway and effectively prevent or modify the course of these common conditions. In this scientific statement, we review the basic cellular structures of the human heart valves and discuss how these structures change in primary valvular heart disease. We focus on the most common primary valvular heart diseases, including calcific aortic stenosis, bicuspid aortic valves, mitral valve prolapse, and rheumatic heart disease, and outline the fundamental molecular discoveries contributing to each. We further outline potential therapeutic molecular targets for primary valvular heart disease and discuss key knowledge gaps that might serve as future research priorities.

Concomitant Left Atrial Appendage Occlusion and Transcatheter Aortic Valve Replacement Among Patients With Atrial Fibrillation.

BACKGROUND: Atrial fibrillation (AF) is common in patients undergoing transcatheter aortic valve replacement (TAVR) and is associated with increased risk of bleeding and stroke. While left atrial appendage occlusion (LAAO) is approved as an alternative to anticoagulants for stroke prevention in patients with AF, placement of these devices in patients with severe aortic stenosis, or when performed at the same time as TAVR, has not been extensively studied. METHODS: WATCH-TAVR (WATCHMAN for Patients with AF Undergoing TAVR) was a multicenter, randomized trial evaluating the safety and effectiveness of concomitant TAVR and LAAO with WATCHMAN in AF patients. Patients were randomized 1:1 to TAVR + LAAO or TAVR + medical therapy. WATCHMAN patients received anticoagulation for 45 days followed by dual antiplatelet therapy until 6 months. Anticoagulation was per treating physician preference for patients randomized to TAVR + medical therapy. The primary noninferiority end point was all-cause mortality, stroke, and major bleeding at 2 years between the 2 strategies. RESULTS: The study enrolled 349 patients (177 TAVR + LAAO and 172 TAVR + medical therapy) between December 2017 and November 2020 at 34 US centers. The mean age of patients was 81 years, and the mean scores for CHA2DS2-VASc and HAS-BLED (Hypertension, Abnormal renal/liver function, Stroke, Bleeding history or predisposition, Labile INR, Elderly, Drugs/alcohol concomitantly) were 4.9 and 3.0, respectively. At baseline, 85.4% of patients were taking anticoagulants and 71.3% patients were on antiplatelet therapy. The cohorts were well-balanced for baseline characteristics. The incremental LAAO procedure time was 38 minutes, and the median contrast volume used for combined procedures was 119 mL versus 70 mL with TAVR alone. At the 24-month follow-up, 82.5% compared with 50.8% of patients were on any antiplatelet therapy, and 13.9% compared with 66.7% of patients were on any anticoagulation therapy in TAVR + LAAO compared with TAVR + medical therapy group, respectively. For the composite primary end point, TAVR + LAAO was noninferior to TAVR + medical therapy (22.7 versus 27.3 events per 100 patient-years for TAVR + LAAO and TAVR + medical therapy, respectively; hazard ratio, 0.86 [95% CI, 0.60-1.22]; Pnoninferiority<0.001). CONCLUSIONS: Concomitant WATCHMAN LAAO and TAVR is noninferior to TAVR with medical therapy in severe aortic stenosis patients with AF. The increased complexity and risks of the combined procedure should be considered when concomitant LAAO is viewed as an alternative to medical therapy for patients with AF undergoing TAVR. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03173534.

Aortic Valve Stenosis Causes Accumulation of Extracellular Hemoglobin and Systemic Endothelial Dysfunction.

BACKGROUND: Whether aortic valve stenosis (AS) can adversely affect systemic endothelial function independently of standard modifiable cardiovascular risk factors is unknown. METHODS: We therefore investigated endothelial and cardiac function in an experimental model of AS mice devoid of standard modifiable cardiovascular risk factors and human cohorts with AS scheduled for transcatheter aortic valve replacement. Endothelial function was determined by flow-mediated dilation using ultrasound. Extracellular hemoglobin (eHb) concentrations and nitric oxide (NO) consumption were determined in blood plasma of mice and humans by ELISA and chemiluminescence. This was complemented by measurements of aortic blood flow using 4-dimensional flow acquisition by magnetic resonance imaging and computational fluid dynamics simulations. The effects of plasma and red blood cell (RBC) suspensions on vascular function were determined in transfer experiments in a murine vasorelaxation bioassay system. RESULTS: In mice, the induction of AS caused systemic endothelial dysfunction. In the presence of normal systolic left ventricular function and mild hypertrophy, the increase in the transvalvular gradient was associated with elevated eryptosis, increased eHb, and increased plasma NO consumption; eHb sequestration by haptoglobin restored endothelial function. Because the aortic valve orifice area in patients with AS decreased, postvalvular mechanical stress in the central ascending aorta increased. This was associated with elevated eHb, circulating RBC-derived microvesicles, eryptotic cells, lower haptoglobin levels without clinically relevant anemia, and consecutive endothelial dysfunction. Transfer experiments demonstrated that reduction of eHb by treatment with haptoglobin or elimination of fluid dynamic stress by transcatheter aortic valve replacement restored endothelial function. In patients with AS and subclinical RBC fragmentation, the remaining circulating RBCs before and after transcatheter aortic valve replacement exhibited intact membrane function, deformability, and resistance to osmotic and hypoxic stress. CONCLUSIONS: AS increases postvalvular swirling blood flow in the central ascending aorta, triggering RBC fragmentation with the accumulation of hemoglobin in the plasma. This increases NO consumption in blood, thereby limiting vascular NO bioavailability. Thus, AS itself promotes systemic endothelial dysfunction independent of other established risk factors. Transcatheter aortic valve replacement is capable of limiting NO scavenging and rescuing endothelial function by realigning postvalvular blood flow to near physiological patterns. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifiers: NCT05603520 and NCT01805739.

Transcatheter or Surgical Aortic Valve Replacement in Patients With Severe Aortic Stenosis and Small Aortic Annulus: A Randomized Clinical Trial.

BACKGROUND: The optimal treatment in patients with severe aortic stenosis and small aortic annulus (SAA) remains to be determined. This study aimed to compare the hemodynamic and clinical outcomes between transcatheter aortic valve replacement (TAVR) and surgical aortic valve replacement (SAVR) in patients with a SAA. METHODS: This prospective multicenter international randomized trial was performed in 15 university hospitals. Participants were 151 patients with severe aortic stenosis and SAA (mean diameter <23 mm) randomized (1:1) to TAVR (n=77) versus SAVR (n=74). The primary outcome was impaired valve hemodynamics (ie, severe prosthesis patient mismatch or moderate-severe aortic regurgitation) at 60 days as evaluated by Doppler echocardiography and analyzed in a central echocardiography core laboratory. Clinical events were secondary outcomes. RESULTS: The mean age of the participants was 75.5±5.1 years, with 140 (93%) women, a median Society of Thoracic Surgeons predicted risk of mortality of 2.50% (interquartile range, 1.67%-3.28%), and a median annulus diameter of 21.1 mm (interquartile range, 20.4-22.0 mm). There were no differences between groups in the rate of severe prosthesis patient mismatch (TAVR, 4 [5.6%]; SAVR, 7 [10.3%]; P=0.30) and moderate-severe aortic regurgitation (none in both groups). No differences were found between groups in mortality rate (TAVR, 1 [1.3%]; SAVR, 1 [1.4%]; P=1.00) and stroke (TAVR, 0; SAVR, 2 [2.7%]; P=0.24) at 30 days. After a median follow-up of 2 (interquartile range, 1-4) years, there were no differences between groups in mortality rate (TAVR, 7 [9.1%]; SAVR, 6 [8.1%]; P=0.89), stroke (TAVR, 3 [3.9%]; SAVR, 3 [4.1%]; P=0.95), and cardiac hospitalization (TAVR, 15 [19.5%]; SAVR, 15 [20.3%]; P=0.80). CONCLUSIONS: In patients with severe aortic stenosis and SAA (women in the majority), there was no evidence of superiority of contemporary TAVR versus SAVR in valve hemodynamic results. After a median follow-up of 2 years, there were no differences in clinical outcomes between groups. These findings suggest that the 2 therapies represent a valid alternative for treating patients with severe aortic stenosis and SAA, and treatment selection should likely be individualized according to baseline characteristics, additional anatomical risk factors, and patient preference. However, the results of this study should be interpreted with caution because of the limited sample size leading to an underpowered study, and need to be confirmed in future larger studies. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03383445.

Extracellular Matrix Disorganization Caused by ADAMTS16 Deficiency Leads to Bicuspid Aortic Valve With Raphe Formation.

BACKGROUND: A better understanding of the molecular mechanism of aortic valve development and bicuspid aortic valve (BAV) formation would significantly improve and optimize the therapeutic strategy for BAV treatment. Over the past decade, the genes involved in aortic valve development and BAV formation have been increasingly recognized. On the other hand, ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) gene family members have been reported to be able to modulate cardiovascular development and diseases. The present study aimed to further investigate the roles of ADAMTS family members in aortic valve development and BAV formation. METHODS: Morpholino-based ADAMTS family gene-targeted screening for zebrafish heart outflow tract phenotypes combined with DNA sequencing in a 304 cohort BAV patient registry study was initially carried out to identify potentially related genes. Both ADAMTS gene-specific fluorescence in situ hybridization assay and genetic tracing experiments were performed to evaluate the expression pattern in the aortic valve. Accordingly, related genetic mouse models (both knockout and knockin) were generated using the CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeat-associated 9) method to further study the roles of ADAMTS family genes. The lineage-tracing technique was used again to evaluate how the cellular activity of specific progenitor cells was regulated by ADAMTS genes. Bulk RNA sequencing was used to investigate the signaling pathways involved. Inducible pluripotent stem cells derived from both BAV patients and genetic mouse tissue were used to study the molecular mechanism of ADAMTS. Immunohistochemistry was performed to examine the phenotype of cardiac valve anomalies, especially in the extracellular matrix components. RESULTS: ADAMTS genes targeting and phenotype screening in zebrafish and targeted DNA sequencing on a cohort of patients with BAV identified ADAMTS16 (a disintegrin and metalloproteinase with thrombospondin motifs 16) as a BAV-causing gene and found the ADAMTS16 p. H357Q variant in an inherited BAV family. Both in situ hybridization and genetic tracing studies described a unique spatiotemporal pattern of ADAMTS16 expression during aortic valve development. Adamts16+/- and Adamts16+/H355Q mouse models both exhibited a right coronary cusp-noncoronary cusp fusion-type BAV phenotype, with progressive aortic valve thickening associated with raphe formation (fusion of the commissure). Further, ADAMTS16 deficiency in Tie2 lineage cells recapitulated the BAV phenotype. This was confirmed in lineage-tracing mouse models in which Adamts16 deficiency affected endothelial and second heart field cells, not the neural crest cells. Accordingly, the changes were mainly detected in the noncoronary and right coronary leaflets. Bulk RNA sequencing using inducible pluripotent stem cells-derived endothelial cells and genetic mouse embryonic heart tissue unveiled enhanced FAK (focal adhesion kinase) signaling, which was accompanied by elevated fibronectin levels. Both in vitro inducible pluripotent stem cells-derived endothelial cells culture and ex vivo embryonic outflow tract explant studies validated the altered FAK signaling. CONCLUSIONS: Our present study identified a novel BAV-causing ADAMTS16 p. H357Q variant. ADAMTS16 deficiency led to BAV formation.

Targeting Sphingosine-1-Phosphate Signaling to Prevent the Progression of Aortic Valve Disease.

BACKGROUND: Aortic valve disease (AVD) is associated with high mortality and morbidity. To date, there is no pharmacological therapy available to prevent AVD progression. Because valve calcification is the hallmark of AVD and S1P (sphingosine-1-phosphate) plays an important role in osteogenic signaling, we examined the role of S1P signaling in aortic stenosis disease. METHODS: AVD progression and its consequences for cardiac function were examined in a murine wire injury-induced AVD model with and without pharmacological and genetic modulation of S1P production, degradation, and receptor signaling. S1P was measured by LC-MS. Calcification of valvular interstitial cells and their response to biomechanical stress were analyzed in the context of S1P signaling. Human explanted aortic valves from patients undergoing aortic valve replacement and cardiovascular magnetic resonance imaging were analyzed for S1P by LC-MS. RESULTS: Raising S1P concentrations in mice with injury-induced AVD by pharmacological inhibition of its sole degrading enzyme S1P lyase vastly enhanced AVD progression and impaired cardiac function resembling human disease. In contrast, low S1P levels caused by SphK1 (sphingosine kinase 1) deficiency potently attenuated AVD progression. We found S1P/S1PR2 (S1P receptor 2) signaling to be responsible for the adverse S1P effect because S1PR2-deficient mice were protected against AVD progression and its deterioration by high S1P. It is important to note that pharmacological S1PR2 inhibition administered after wire injury successfully prevented AVD development. Mechanistically, biomechanical stretch stimulated S1P production by SphK1 in human valvular interstitial cells as measured by C17-S1P generation, whereas S1P/S1PR2 signaling induced their osteoblastic differentiation and calcification through osteogenic RUNX2/OPG signaling and the GSK3ß-Wnt-ß-catenin pathway. In patients with AVD, stenotic valves exposed to high wall shear stress had higher S1P content and increased SphK1 expression. CONCLUSIONS: Increased systemic or local S1P levels lead to increased valvular calcification. S1PR2 antagonists and SphK1 inhibitors may offer feasible pharmacological approaches to human AVD in prophylactic, disease-modifying or relapse-preventing manners.

High-Throughput Deep Learning Detection of Mitral Regurgitation.

BACKGROUND: Diagnosis of mitral regurgitation (MR) requires careful evaluation by echocardiography with Doppler imaging. This study presents the development and validation of a fully automated deep learning pipeline for identifying apical 4-chamber view videos with color Doppler echocardiography and detecting clinically significant (moderate or severe) MR from transthoracic echocardiograms. METHODS: A total of 58 614 transthoracic echocardiograms (2 587 538 videos) from Cedars-Sinai Medical Center were used to develop and test an automated pipeline to identify apical 4-chamber view videos with color Doppler across the mitral valve and then assess MR severity. The model was tested internally on a test set of 1800 studies (80 833 videos) from Cedars-Sinai Medical Center and externally evaluated in a geographically distinct cohort of 915 studies (46 890 videos) from Stanford Healthcare. RESULTS: In the held-out Cedars-Sinai Medical Center test set, the view classifier demonstrated an area under the curve (AUC) of 0.998 (0.998-0.999) and correctly identified 3452 of 3539 echocardiography videos as having color Doppler information across the mitral valve (sensitivity of 0.975 [0.968-0.982] and specificity of 0.999 [0.999-0.999] compared with manually curated videos). In the external test cohort from Stanford Healthcare, the view classifier correctly identified 1051 of 1055 manually curated videos with color Doppler information across the mitral valve (sensitivity of 0.996 [0.990-1.000] and specificity of 0.999 [0.999-0.999]). In the Cedars-Sinai Medical Center test cohort, MR moderate or greater in severity was detected with an AUC of 0.916 (0.899-0.932) and severe MR was detected with an AUC of 0.934 (0.913-0.953). In the Stanford Healthcare test cohort, the model detected MR moderate or greater in severity with an AUC of 0.951 (0.924-0.973) and severe MR with an AUC of 0.969 (0.946-0.987). CONCLUSIONS: In this study, a novel automated pipeline for identifying clinically significant MR from full transthoracic echocardiography studies demonstrated excellent performance across large numbers of studies and across multiple institutions. Such an approach has the potential for automated screening and surveillance of MR.

Deep Learning for Echo Analysis, Tracking, and Evaluation of Mitral Regurgitation (DELINEATE-MR).

BACKGROUND: Artificial intelligence, particularly deep learning (DL), has immense potential to improve the interpretation of transthoracic echocardiography (TTE). Mitral regurgitation (MR) is the most common valvular heart disease and presents unique challenges for DL, including the integration of multiple video-level assessments into a final study-level classification. METHODS: A novel DL system was developed to intake complete TTEs, identify color MR Doppler videos, and determine MR severity on a 4-step ordinal scale (none/trace, mild, moderate, and severe) using the reading cardiologist as a reference standard. This DL system was tested in internal and external test sets with performance assessed by agreement with the reading cardiologist, weighted κ, and area under the receiver-operating characteristic curve for binary classification of both moderate or greater and severe MR. In addition to the primary 4-step model, a 6-step MR assessment model was studied with the addition of the intermediate MR classes of mild-moderate and moderate-severe with performance assessed by both exact agreement and ±1 step agreement with the clinical MR interpretation. RESULTS: A total of 61 689 TTEs were split into train (n=43 811), validation (n=8891), and internal test (n=8987) sets with an additional external test set of 8208 TTEs. The model had high performance in MR classification in internal (exact accuracy, 82%; κ=0.84; area under the receiver-operating characteristic curve, 0.98 for moderate or greater MR) and external test sets (exact accuracy, 79%; κ=0.80; area under the receiver-operating characteristic curve, 0.98 for moderate or greater MR). Most (63% internal and 66% external) misclassification disagreements were between none/trace and mild MR. MR classification accuracy was slightly higher using multiple TTE views (accuracy, 82%) than with only apical 4-chamber views (accuracy, 80%). In subset analyses, the model was accurate in the classification of both primary and secondary MR with slightly lower performance in cases of eccentric MR. In the analysis of the 6-step classification system, the exact accuracy was 80% and 76% with a ±1 step agreement of 99% and 98% in the internal and external test set, respectively. CONCLUSIONS: This end-to-end DL system can intake entire echocardiogram studies to accurately classify MR severity and may be useful in helping clinicians refine MR assessments.

Conduction Disturbances and Outcome After Surgical Aortic Valve Replacement in Patients With Bicuspid and Tricuspid Aortic Stenosis.

BACKGROUND: This study aimed to compare the incidence and prognostic implications of new-onset conduction disturbances after surgical aortic valve replacement (SAVR) in patients with bicuspid aortic valve (BAV) aortic stenosis (AS) versus patients with tricuspid aortic valve (TAV) AS (ie, BAV-AS and TAV-AS, respectively). Additionally, the study included stratification of BAV patients according to subtype. METHODS: In this cohort study, the incidence of postoperative third-degree atrioventricular (AV) block with subsequent permanent pacemaker requirement and new-onset left bundle-branch block (LBBB) was investigated in 1147 consecutive patients without preoperative conduction disorder who underwent isolated SAVR (with or without ascending aortic surgery) between January 1, 2005, and December 31, 2022. The groups were stratified by aortic valve morphology (BAV, n=589; TAV, n=558). The outcomes of interests were new-onset third-degree AV block or new-onset LBBB during the index hospitalization. The impact of new-onset postoperative conduction disturbances on survival was investigated in BAV-AS and TAV-AS patients during a median follow-up of 8.2 years. BAV morphology was further categorized according to the Sievers and Schmidtke classification system (possible in 307 BAV-AS patients) to explore association between BAV subtypes and new-onset conduction disturbances after SAVR. RESULTS: The overall incidence of third-degree AV block and new-onset LBBB after SAVR was 4.5% and 7.8%, respectively. BAV-AS patients had a higher incidence of both new-onset third-degree AV block (6.5% versus 2.5%; P=0.001) and new-onset LBBB (9.7% versus 5.7%; P=0.013) compared with TAV-AS patients. New-onset LBBB was associated with an increased all-cause mortality during follow-up (adjusted hazard ratio, 1.60 [95% CI, 1.12-2.30]; P=0.011), whereas new-onset third-degree AV block was not associated with worse prognosis. Subgroup analysis of the BAV cohort revealed that BAV-AS patients with fusion of the right- and non-coronary cusps had the highest risk of new-onset third-degree AV block (adjusted odds ratio [aOR], 8.33 [95% CI, 3.31-20.97]; P<0.001, with TAV as reference group) and new-onset LBBB (aOR, 4.03 [95% CI, 1.84-8.82]; P<0.001, with TAV as reference group), whereas no significant association was observed for the other BAV subtypes. CONCLUSIONS: New-onset LBBB after SAVR is associated with increased all-cause mortality during follow-up, and is more frequent complication in BAV AS patients compared with TAV-AS patients. BAV-AS patients with fusion of the right- and non-coronary cusps have an increased risk for conduction disturbances after SAVR. This should be taken into consideration when managing these patients.

Major Facilitator Superfamily Domain Containing 5 Inhibition Reduces Lipoprotein(a) Uptake and Calcification in Valvular Heart Disease.

BACKGROUND: High circulating levels of Lp(a) (lipoprotein[a]) increase the risk of atherosclerosis and calcific aortic valve disease, affecting millions of patients worldwide. Although atherosclerosis is commonly treated with low-density lipoprotein-targeting therapies, these do not reduce Lp(a) or risk of calcific aortic valve disease, which has no available drug therapies. Targeting Lp(a) production and catabolism may provide therapeutic benefit, but little is known about Lp(a) cellular uptake. METHODS: Here, unbiased ligand-receptor capture mass spectrometry was used to identify MFSD5 (major facilitator superfamily domain containing 5) as a novel receptor/cofactor involved in Lp(a) uptake. RESULTS: Reducing MFSD5 expression by a computationally identified small molecule or small interfering RNA suppressed Lp(a) uptake and calcification in primary human valvular endothelial and interstitial cells. MFSD5 variants were associated with aortic stenosis (P=0.027 after multiple hypothesis testing) with evidence suggestive of an interaction with plasma Lp(a) levels. CONCLUSIONS: MFSD5 knockdown suppressing human valvular cell Lp(a) uptake and calcification, along with meta-analysis of MFSD5 variants associating with aortic stenosis, supports further preclinical assessment of MFSD5 in cardiovascular diseases, the leading cause of death worldwide.