Anatomy and formation of congenital bicuspid and quadricuspid pulmonary valves in Syrian hamsters

The Medical versus Zoological Concept of Outflow Tract Valves of the Vertebrate Heart

The anatomical elements that in humans prevent blood backflow from the aorta and pulmonary artery to the left and right ventriclesare the aortic and pulmonary valves, respectively. Each valve regularly consists of three leaflets (cusps), each supported by its valvular sinus. From the medical viewpoint, each set of three leaflets and sinuses is regarded as a morpho-functional unit. This notion also applies to birds and non-human mammals. However, the structures that prevent the return of blood to the heart in other vertebrates are notably different. This has led to discrepancies between physicians and zoologists in defining what a cardiac outflow tract valve is. The aim here is to compare the gross anatomy of the outflow tract valvular system among several groups of vertebrates in order to understand the conceptual and nomenclature controversies in the field.

Development of the Human Arterial Valves: Understanding Bicuspid Aortic Valve

Abnormalities in the arterial valves are some of the commonest congenital malformations, with bicuspid aortic valve (BAV) occurring in as many as 2% of the population. Despite this, most of what we understand about the development of the arterial (semilunar; aortic and pulmonary) valves is extrapolated from investigations of the atrioventricular valves in animal models, with surprisingly little specifically known about how the arterial valves develop in mouse, and even less in human. In this review, we summarise what is known about the development of the human arterial valve leaflets, comparing this to the mouse where appropriate.

Perfil Clínico e Desfechos em 30 Dias de Pacientes Portadores de Valva Aórtica Bicúspide Submetidos à Cirurgia em Valva Aórtica e/ou Aorta

Fundamento

A válvula aórtica bicúspide (VAB) atinge de 0,5 a 2% da população e está associada a alterações valvares e de aorta. Há carência de estudos sobre o perfil desses pacientes na população brasileira.

Objetivo

Descrever o perfil de pacientes com VAB submetidos à cirurgia valvar e/ou de aorta em um centro cardiológico terciário, assim como os desfechos relacionados à intervenção.

Métodos

Coorte retrospectiva incluindo 195 pacientes (idade média 54±14 anos, 73,8% do sexo masculino) com diagnóstico de VAB submetidos à abordagem cirúrgica (valvar e/ou de aorta) no período de 2014 a 2019. Foram avaliados dados clínicos, ecocardiográficos e tomográficos, além das características da intervenção e eventos em 30 dias. O valor de p<0,05 foi considerado estatisticamente significante.

Resultados

Encontramos alta prevalência de aneurisma de aorta (56,5%), com diâmetro médio de 46,9±10,2 mm. Insuficiência aórtica importante foi encontrada em 25,1% e estenose aórtica importante em 54,9%. Cirurgia isolada em valva aórtica foi realizada em 48,2%, cirurgia isolada de aorta em 6,7% e cirurgia combinada em 45,1%. A mortalidade em 30 dias foi de 8,2%. Na análise multivariada, os fatores preditores de desfecho combinado em 30 dias (morte, fibrilação atrial e reoperação) foram idade (OR 1,044, IC 95% 1,009-1,081, p=0,014) e o índice de massa do ventrículo esquerdo (OR 1,009, IC 95% 1,000-1,018, p=0,044).

Conclusão

Pacientes com VAB abordados no nosso serviço apresentam uma maior incidência de aortopatia, com a necessidade adicional de avaliação da aorta com tomografia computadorizada ou ressonância magnética.

New Concepts in the Development and Malformation of the Arterial Valves

Although in many ways the arterial and atrioventricular valves are similar, both being derived for the most part from endocardial cushions, we now know that the arterial valves and their surrounding structures are uniquely dependent on progenitors from both the second heart field (SHF) and neural crest cells (NCC). Here, we will review aspects of arterial valve development, highlighting how our appreciation of NCC and the discovery of the SHF have altered our developmental models. We will highlight areas of research that have been particularly instructive for understanding how the leaflets form and remodel, as well as those with limited or conflicting results. With this background, we will explore how this developmental knowledge can help us to understand human valve malformations, particularly those of the bicuspid aortic valve (BAV). Controversies and the current state of valve genomics will be indicated.

Quadricuspid pulmonary valve: macroscopic and microscopic morphometric examination

A quadricuspid pulmonary valve obtained upon autopsy of a 26-year-old male was examined. The macroscopic evaluation revealed three normal (posterior, right anterior and left anterior) leaflets and one additional leaflet of the pulmonary valve. Except that, the heart showed neither other anatomical variabilities nor any signs of heart disease. The additional leaflet was located between the left anterior and right anterior leaflets and was significantly smaller in size. Under the microscope, all leaflets showed preservation of the typical, layered structure. The thickness and extracellular matrix composition of the particular layers differed between the leaflets. Right ventricular myocardium (myocardial sleeves) exceeded the level of the hinge line in all three normal leaflets, which was not observed in the additional leaflet. Autonomic nerves and ganglia were not seen in the perivalvular epicardial adipose tissue surrounding the additional leaflet. The sinus wall of all the leaflets revealed typical organization of collagen bundles as well as elastic fibers and showed no signs of disruption. The abnormality seen in the structure of the pulmonary valve is likely to be a result of disturbed embryonic development and may affect the clinical management of patients with such variation.

Quadricuspid Aortic Valve With Ostium Secundum Atrial Septal Defect

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QAV is a rare congenital cardiac malformation.

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QAV with ostium secundum atrial septal defect.

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Hurwitz and Roberts's anatomic classification of QAV.

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More than 50% of people with QAV require valve repair or replacement.

Pigmentation of the aortic and pulmonary valves in C57BL/6J x Balb/cByJ hybrid mice of different coat colours

Neural crest-derived melanocytes have been recorded in several parts of the mammalian heart but not in the pulmonary valve. We report here the presence of melanin-containing cells in the leaflets (cusps) of both the aortic and pulmonary valves. A total of 158 C57BL/6J x Balb/cByJ hybrid mice exhibiting four coat colours, namely black, white, agouti and non-agouti brown, were examined. We sought for any relationship between the presence of melanocytes in the valves and the coat colour of the animals. The pigmentation levels of the leaflets were accomplished using a scale of five pigment intensities. White mice lacked pigment in the heart. In 10.5% of the remaining animals, there were melanocytes in the pulmonary valve leaflets. Thus, this is the first study to report the presence of such cells in the pulmonary valve of mammals. Melanocytes occurred in the leaflets of the aortic valves of 87.2% of mice. The incidence of melanocytes and the pigmentation level of the leaflets did not statistically differ according to the coat colours of the animals. This disagrees with previous observations, indicating that the amount of melanocytes in the heart reflects that of the skin. The incidence and distribution of melanocytes in aortic and pulmonary valves are consistent with the notion that the formation of the arterial valves is mediated by specific subpopulations of neural crest cells. We hypothesize that melanocytes, even not producing melanin, may be more frequent in the heart than previously thought, exerting presumably an immunological function.

Quadricuspid Aortic Valve: Report of Two Cases and Brief Review

Quadricuspid aortic valve (QAV) is a rare congenital cardiac defect characterized by the presence of four aortic valve leaflets of equal or varying sizes. Even rarer is its clinical presentation with aortic stenosis. Diagnosis of QAV could be challenging but is of great importance as patients often present with progressive aortic regurgitation. We present 2 cases of QAV presenting differently: one with aortic stenosis requiring valve replacement and the other with aortic regurgitation requiring close monitoring.

Investigation of an anatomically variant isolated bicuspid pulmonary valve: A case report

INTRODUCTION

We provide a discussion of the anatomical characteristics of the bicuspid pulmonary valve (BPV) in this paper. We performed an autopsy of an isolated BPV found in the heart of a deceased individual. The deceased was a man in his 60s and had no previous history of cardiovascular disease. The heart weighed 260 g and had mild right ventricular hypertrophy. The pulmonary valve had a fish-mouth-like shape that was convex to the pulmonary trunk and both cusps were thickened and hardened. The anterior and left semilunar cusps of the pulmonary valve were fused. Post-stenotic dilatation was noted.

CONCLUSIONS

In comparing the present case with previous reports, we found that, in human BPVs, cusps are fused in at least 2 patterns.

Incidental echocardiographic findings of a quadricuspid aortic valve associated with aortic regurgitation in a cat

Case summary

A 10-month-old male domestic shorthair cat was brought to Kitanomori Animal Hospital for routine castration. Preoperative thoracic radiography revealed a mildly enlarged heart silhouette, and transthoracic echocardiography (ECHO) suggested a quadricuspid aortic valve associated with central aortic regurgitation (regurgitant fraction 31%). After sedation with intramuscular medetomidine and midazolam for castration, heart rate decreased from 193 to 76 beats per minute. ECHO under sedation revealed two equally small and two equally large aortic valve cusps, suggesting a type C quadricuspid aortic valve. The findings were confirmed by real-time three-dimensional ECHO.

Relevance and novel information

This case reveals the echocardiographic features of a feline quadricuspid aortic valve and shows that transthoracic ECHO is useful to examine aortic valve morphology in cats. It also suggests that echocardiographic screening may be beneficial for detecting congenital cardiac anomalies in apparently healthy cats.

Quadricuspid Aortic Valve: A Case Report and Review of the Literature

The quadricuspid aortic valve (QAV) is a rare malformation; often isolated, sometimes associated with other heart diseases. Before the era of echocardiography, the diagnosis was made incidentally at autopsy or during surgery of valve replacement. The extensive use of echocardiography has allowed an early and accurate diagnosis of this malformation. In many cases, the transthoracic approach is suitable for the diagnosis but, transesophageal echocardiography is a tool for the accurate definition of the valve anatomy. This review analyzes, after the presentation of a clinical case, the current knowledge on embryogenesis, classification, diagnosis and clinical course of QAV.

Factors other than genotype account largely for the phenotypic variation of the pulmonary valve in Syrian hamsters

Understanding of the aetiology of congenitally anomalous pulmonary valves remains incomplete. The aim of our study, therefore, was to elucidate the degree to which the phenotypic variation known to exist for the pulmonary valve relies on genotypic variation. Initially, we tested the hypothesis that genetically alike individuals would display similar valvar phenotypes if the phenotypic arrangement depended entirely, or almost entirely, on the genotype. Thus, we examined pulmonary valves from 982 Syrian hamsters belonging to two families subject to systematic inbreeding by crossing siblings. Their coefficient of inbreeding was 0.999 or higher, so they could be considered genetically alike. External environmental factors were standardized as much as possible. A further 97 Syrian hamsters from an outbred colony were used for comparative purposes. In both the inbred and outbred hamsters, we found valves with a purely trifoliate, or tricuspid, design, trifoliate valves with a more or less extensive fusion of the right and left leaflets, bifoliate, or bicuspid, valves with fused right and left leaflets, with or without a raphe located in the conjoined arterial sinus, and quadrifoliate, or quadricuspid, valves. The incidence of the different valvar morphological variants was similar in the outbred and inbred colonies, except for the bifoliate pulmonary valves, which were significantly more frequent in the hamsters from one of the two inbred families. Results of crosses between genetically alike hamsters revealed no significant association between the pulmonary valvar phenotypes as seen in the parents and their offspring. The incidence of bifoliate pulmonary valves, nonetheless, was higher than statistically expected in the offspring of crosses where at least one of the parents possessed a pulmonary valve with two leaflets. Our observations are consistent with the notion that the basic design of the pulmonary valve, in terms of whether it possesses three or two leaflets, relies on genotypic determinants. They also denote that the bifoliate condition of the valve is the consequence of complex inheritance, with reduced penetrance and variable expressivity. Moreover, in showing that the incidence of the bifoliate pulmonary valve significantly differs in two different isogenetic backgrounds, our data suggest that genetic modifiers might be implicated in directing the manifestation of such specific pulmonary valvar malformations. Finally, our findings indicate that factors other than the genotype, operating during embryonic life and creating developmental noise, or random variation, play a crucial role in the overall phenotypic variation involving the pulmonary valve.

Quadricuspid aortic valve by cardiac magnetic resonance imaging: a case report and review of the literature

Quadricuspid aortic valve (QAV) is a rare congenital cardiac entity. The recognition of QAV has clinical significance as it causes aortic valve dysfunction, commonly aortic regurgitation, and is often associated with other congenital cardiac abnormalities. We showed the important role played by cardiac magnetic resonance imaging in detecting QAV and review the available literature to explain its incidence, diagnosis, classifications, embryology, correlation between morphology of the QAV and its function, associated conditions, and management.

Quadricuspid aortic valve with sinus of Valsalva rupture

A 22-year-old female with no medical history presented to the emergency room with 2 weeks of rapidly worsening dyspnea on exertion, orthopnea, and cough. On cardiac auscultation, she was noted to have to-and-fro murmurs and a continuous murmur with signs of right heart failure. Echocardiographic images obtained showed moderate to severe aortic regurgitation, severe tricuspid regurgitation, and a "windsock" originating in the right coronary sinus of Valsalva and terminating in the right atrium. The aortic valve had four leaflets, with the right leaflet function compromised by the ruptured sinus, causing aortic regurgitation. The patient underwent resection of the sinus aneurysm and aortic valve replacement with a bioprosthetic valve. Quadricuspid aortic valves are uncommon and are rarely associated with sinus of Valsalva aneurysm. The prevalence in the general population, clinical progression, and prognosis of this unique congenital abnormality are reviewed.

Bicuspid aortic valve disease

Bicuspid aortic valve (BAV) disease is the most common congenital cardiac defect. While the BAV can be found in isolation, it is often associated with other congenital cardiac lesions. The most frequent associated finding is dilation of the proximal ascending aorta secondary to abnormalities of the aortic media. Changes in the aortic media are present independent of whether the valve is functionally normal, stenotic, or incompetent. Although symptoms often manifest in adulthood, there is a wide spectrum of presentations ranging from severe disease detected in utero to asymptomatic disease in old age. Complications can include aortic valve stenosis or incompetence, endocarditis, aortic aneurysm formation, and aortic dissection. Despite the potential complications, 2 large contemporary series have demonstrated that life expectancy in adults with BAV disease is not shortened when compared with the general population. Because BAV is a disease of both the valve and the aorta, surgical decision making is more complicated, and many undergoing aortic valve replacement will also need aortic root surgery. With or without surgery, patients with BAV require continued surveillance. Recent studies have improved our understanding of the genetics, the pathobiology, and the clinical course of the disease, but questions are still unanswered. In the future, medical treatment strategies and timing of interventions will likely be refined. This review summarizes our current understanding of the pathology, genetics, and clinical aspects of BAV disease with a focus on BAV disease in adulthood.

A case of pentacuspid pulmonary valve

A pentacuspid pulmonary valve is a rare congenital anomaly. The present report describes a case of pentacuspid pulmonary valve encountered during the autopsy of a 50-year-old man with a ruptured abdominal aortic aneurysm. The pentacuspid pulmonary valve had three relatively equal cusps and two smaller cusps. In this case, a tricuspid aortic valve was identified with normal structure and no evidence of heart failure was found clinically or pathologically.

Quadricuspid aortic valves

Quadricuspid aortic valves (QAV) are a rare but well recognized cause of significant aortic regurgitation. The first case was found reported in 1862. Since then there have been 110 reported cases of QAV and we report 4 more. Previously, these were diagnosed at the time of surgery or postmortem examination. With advances in echocardiography, including harmonic imaging, and also the advent of transesophageal echocardiography, more cases are being diagnosed prior to surgery. We describe four more cases, three diagnosed preoperatively and one at the time of surgery, and then review the previously reported cases. Of the 114 cases reported, 46 had the aortic valve replaced, most commonly in the 5th and 6th decade of life. Hurwitz and Roberts classified quadricuspid valves according to the size of the leaflets. It has previously been believed that QAVs with four equal sized leaflets were less likely to develop significant aortic regurgitation; however, on review of the available cases, this would not appear to be the case. The preoperative diagnosis of QAVs is important as they can be associated with abnormally placed coronary ostium. Of the 114 cases reported, there are 10 reports of abnormally placed ostia. There has been at least one reported case of death occurring because of obstruction of an abnormally placed right coronary ostium by a prosthetic aortic valve.

Novel missense mutations (p.T596M and p.P1797H) in NOTCH1 in patients with bicuspid aortic valve

The bicuspid aortic valve (BAV) is the most common congenital cardiac malformation, occurring in 1-2% of the population. In a recent report, mutations in NOTCH1 a signaling and transcriptional regulator have been shown to cause BAV in two families. This study provides data on systematic sequencing in search for novel mutations in NOTCH1 gene in a large sample BAV. For the first time, we report results of a systematic mutation-analysis based on DNA-sequencing of all coding exons and adjacent splice consensus sequences of NOTCH1 gene. Our analyses revealed 57 NOTCH1 sequence variants. Twenty-one variants are located within exons and 36 within intronic or 5'-UTR sequences. Thirty-five variants were described previously as polymorphisms. The remaining 22, however, were neither listed in public SNP databases nor in the literature and were therefore considered novel. Seventeen variants were found only once (MAF = 1%), of these 15 were novel. Two sequence variants led to amino acid substitutions (p.T596M and p.P1797H) and are located in highly conserved regions of the NOTCH1 protein. In addition, these two mutations could not be detected in at least 327 healthy controls by using RFLP-analysis. The functional relevance of the other 13 novel and rare variants could not be proven without further functional examination. In this study, we provide a new evidence that the mutations in the NOTCH1 gene may trigger the underlying mechanism causing the valve calcification, especially in BAV. In conclusion, NOTCH1 gene mutations do not only play a role in familiar BAV, but can also be observed in approximately 4% of sporadic cases.

A bicuspid pulmonary valve associated with tetralogy of fallot

Congenitally bicuspid pulmonary valves are uncommon. When they occur, it is usually in association with other congenital cardiac lesions, most often a tetralogy of Fallot. We present a rare case of a patient with a congenitally bicuspid pulmonary valve who had pulmonary valve and RVOT reconstruction. The patient did well for 17 years, but needed further reconstruction when the pulmonary valve started getting stenosed and RV pressures went up significantly. The pulmonary valve showed fibroses, thickening, and focal calcification.

Quadricuspid Aortic Valve and Associated Abnormalities in a Dog

An 11-month-old, female Scottish terrier was presented with a history of a heart murmur. The electrocardiogram showed signs of left ventricular enlargement, and radiography confirmed generalized cardiomegaly. Echocardiography revealed four equally sized aortic valve cusps. A ventricular septal defect, with systolic left-to-right shunting, and aortic regurgitation into both ventricles were also present. The dog was free of clinical signs 1 year after diagnosis.

Cartilage in pulmonary valves of Syrian hamsters

The presence of cartilage in the pulmonary valve has been reported in birds, but not in mammals. We describe here the occurrence of cartilaginous tissue in the pulmonary valves of 40 (11.4%) of 351 Syrian hamsters examined using histological, histochemical and/or immunohistochemical techniques. The cartilaginous deposits were located along the fibrous attachments of the valve leaflets to the wall of the pulmonary artery trunk. Our findings indicate that the proximal attachments of the leaflets to their respective sinuses, and especially that of the ventral leaflet, are the most prone valvular regions to develop cartilaginous foci. Nonetheless, the possible function of these foci remains an open question. Formation of cartilage in the pulmonary valve starts within the first month of life, that is during the period in which the valve reaches histological maturation. The earliest evidence of chondrogenesis is the presence of small groups of cells embedded in a type II collagen-positive extracellular matrix. These groups of cells, which can appear as early as one day after birth, increase moderately in size and differentiate into hyaline cartilaginous tissue. The precursors of the cartilaginous cells are presumed to be neural crest-derived elements. However, the factor or factors involved in the differentiation of these precursors into chondrocytes are still unknown. In this regard, our observations cast doubt on the hypothesis that the formation of cardiac cartilages is primarily due to locally intense mechanical stimulation.

Congenital quadricuspid aortic valve anomaly in two dogs

A congenital quardricuspid aortic valve (QAV) was detected in two one year-old male dogs. This defect has not previously been reported in dogs. In both cases, the diagnosis was made by two-dimensional echocardiography performed to investigate the cause of a soft heart murmur. On the short-axis of a two-dimensional echocardiogram, the commissures of the QAV produced an "X" configuration of the valve during diastole in contrast to the "Y" configuration observed in dogs with a normal semilunar valve. Color flow Doppler studies indicated mild aortic regurgitation in both dogs, neither of which evidenced signs of disability. Subsequent necropsy of one of the dogs confirmed the presence of QAV.