Bicuspid aortic valve. Comparison of congenital and acquired types

Leaflet fusion length is associated with aortic dilation and flow alterations in non-dysfunctional bicuspid aortic valve

OBJECTIVE

Bicuspid aortic valve (BAV), the most common congenital valve defect, is associated with increased risk of aortic dilation and related complications; however, current risk assessment is not effective. Most of BAV have three leaflets with a fusion between two of them of variable length. This study aimed to ascertain whether the extent of leaflet fusion (often called raphe) is related to aortic dilation and flow abnormalities in BAV with no significant valvular dysfunction.

METHODS

One hundred and twenty BAV patients with no significant valvular dysfunction or history of surgical repair or aortic valve replacement were consecutively and prospectively enrolled (September 2014-October 2018). Cardiac magnetic resonance protocol included a 4D flow sequence for haemodynamic assessment. Moreover, a stack of double-oblique cine images of the aortic valve were used to quantify fusion length (in systole) and leaflet length (diastole). Inter- and intra-observer reproducibility was tested in 30 randomly selected patients.

RESULTS

Aortic valve leaflet fusion was measurable in 112 of 120 (93%) cases with good reproducibility (ICC = 0.826). Fusion length varied greatly (range: 2.3-15.4 mm; mean: 7.8 ± 3.2 mm). After correction for demographic and clinical conditions, fusion length was independently associated with diameter and z-score at the sinus of Valsalva (p = 0.002 and p = 0.002, respectively) and ascending aorta (p = 0.028 and p = 0.046). Fusion length was positively related to flow asymmetry, vortices and circumferential wall shear stress, thereby possibly providing a pathophysiological link with aortic dilation.

CONCLUSIONS

Aortic valve fusion length is related to aortic dilation and flow abnormalities in BAV patients.

KEY POINTS

• The length of the fusion between leaflets in non-dysfunctional bicuspid aortic valves varies substantially and can be reliably measured by cine CMR. • Aortic valve leaflet fusion length is independently related to aortic sinus and ascending aorta diameter. • Increased flow asymmetry, circumferential wall shear stress and presence of vortices are positively related to aortic valve leaflet fusion length.

Causes, Diagnosis, Risk Stratification and Treatment of Bicuspid Aortic Valve Disease: An Updated Review

The most common congenital heart disease is the bicuspid aortic valve. Understanding the pathophysiology and the altered hemodynamics is a key component for the diagnosis, risk stratification and treatment. Among others, aortic valve stenosis is the most common complication. Treatment strategies vary depending on the severity of the disease, particularly the dilation of the aorta playing a major role. Together with valve replacement, transcatheter aortic valve implantation is now considered as an alternative option with good results. With this review we would like to discuss the causes, diagnostic methods, risk stratification and treatment strategies of the bicuspid aortic valve.

Spectrum of aortic valve abnormalities associated with aortic dilation across age groups in Turner syndrome

BACKGROUND

Congenital aortic valve fusion is associated with aortic dilation, aneurysm, and rupture in girls and women with Turner syndrome. Our objective was to characterize aortic valve structure in subjects with Turner syndrome and to determine the prevalence of aortic dilation and valve dysfunction associated with different types of aortic valves.

METHODS AND RESULTS

The aortic valve and thoracic aorta were characterized by cardiovascular MRI in 208 subjects with Turner syndrome in an institutional review board-approved natural history study. Echocardiography was used to measure peak velocities across the aortic valve and the degree of aortic regurgitation. Four distinct valve morphologies were identified: tricuspid aortic valve, 64% (n=133); partially fused aortic valve, 12% (n=25); bicuspid aortic valve, 23% (n=47); and unicuspid aortic valve, 1% (n=3). Age and body surface area were similar in the 4 valve morphology groups. There was a significant trend, independent of age, toward larger body surface area-indexed ascending aortic diameters with increasing valve fusion. Ascending aortic diameters were (mean±SD) 16.9±3.3, 18.3±3.3, and 19.8±3.9 mm/m(2) (P<0.0001) for tricuspid aortic valve, partially fused aortic valve, and bicuspid aortic valve+unicuspid aortic valve, respectively. Partially fused aortic valve, bicuspid aortic valve, and unicuspid aortic valve were significantly associated with mild aortic regurgitation and elevated peak velocities across the aortic valve.

CONCLUSIONS

Aortic valve abnormalities in Turner syndrome occur with a spectrum of severity and are associated with aortic root dilation across age groups. Partial fusion of the aortic valve, traditionally regarded as an acquired valve problem, had an equal age distribution and was associated with an increased ascending aortic diameters.

Native Cardiac Valve Pathology

Anatomy of the native cardiac valves, reasons for surgical excision and examination, and a summary of the gross examination and documentation are presented. Aortic stenosis, aortic valve regurgitation, tricuspid and pulmonary valve pathology, mitral stenosis, and mitral insufficiency are each presented with an overview, focused anatomy, and discussion of pathologic diagnosis by gross examination and histology.

Genetically alike Syrian hamsters display both bifoliate and trifoliate aortic valves

The bifoliate, or bicuspid, aortic valve (BAV) is the most frequent congenital cardiac anomaly in man. It is a heritable defect, but its mode of inheritance remains unclear. Previous studies in Syrian hamsters showed that BAVs with fusion of the right and left coronary leaflets are expressions of a trait, the variation of which takes the form of a phenotypic continuum. It ranges from a trifoliate valve with no fusion of the coronary leaflets to a bifoliate root devoid of any raphe. The intermediate stages are represented by trifoliate valves with fusion of the coronary aortic leaflets, and bifoliate valves with raphes. The aim of this study was to elucidate whether the distinct morphological variants rely on a common genotype, or on different genotypes. We examined the aortic valves from 1 849 Syrian hamsters belonging to a family subjected to systematic inbreeding by full-sib mating. The incidence of the different trifoliate aortic valve (TAV) and bifoliate aortic valve (BAV) morphological variants widely varied in the successive inbred generations. TAVs with extensive fusion of the leaflets, and BAVs, accounted for five-sixths of the patterns found in Syrian hamsters considered to be genetically alike or virtually isogenic, with the probability of homozygosity being 0.999 or higher. The remaining one-sixth hamsters had aortic valves with a tricuspid design, but in most cases the right and left coronary leaflets were slightly fused. Results of crosses between genetically alike hamsters, with the probability of homozygosity being 0.989 or higher, revealed no significant association between the valvar phenotypes in the parents and their offspring. Our findings are consistent with the notion that the BAVs of the Syrian hamster are expressions of a quantitative trait subject to polygenic inheritance. They suggest that the genotype of the virtually isogenic animals produced by systematic inbreeding greatly predisposes to the development of anomalous valves, be they bifoliate, or trifoliate with extensive fusion of the leaflets. We infer that the same underlying genotype may account for the whole range of valvar morphological variants, suggesting that factors other than genetic ones are acting during embryonic life, creating the so-called intangible variation or developmental noise, and playing an important role in the definitive anatomic configuration of the valve. The clinical implication from our study is that congenital aortic valves with a trifoliate design, but with fusion of coronary aortic leaflets, may harbour the same inherent risks as those already recognised for BAVs with fusion of right and left coronary leaflets.

Anatomic three-dimensional echocardiographic correlation of bicuspid aortic valve

This study was undertaken to verify the echocardiographic characteristics of bicuspid aortic valve (AV) using 3-dimensional transesophageal echocardiography by comparing the findings with anatomic examination of autopsy specimens from carriers of this condition. Three-dimensional reconstructions of transesophageal echocardiograms were performed on 14 patients with bicuspid AV, and 20 autopsy specimens of bicuspid AVs were analyzed. Echocardiographic images and autopsy material were correlated. Two variants of bicuspid aorta were identified. In group I the AV had 2 leaflets. This group included 9 (9/14) 3-dimensional echocardiographic studies and 13 (13/20) necropsies. In group II 3 sigmoid leaflets had originally developed and 2 underwent dysplastic fusion, resulting in functionally bicuspid valves. Five (5/14) echocardiographic studies and 7 (7/20) anatomic specimens fell into this category. There was a clear correspondence between anatomic and echocardiographic findings, which leads to the conclusion that 3-dimensional echocardiography is a technique that reliably defines the morphological details of bicuspid AV with the precision of anatomopathologic examination.

Sudden deterioration of aortic regurgitation due to rupture of a raphal cord on the conjoined cusp

A 57-year-old man was admitted to hospital for acute myocardial infarction associated with mild aortic regurgitation, which was successfully treated by intracoronary thrombolysis. Twenty-four days later, he suffered from another chest pain attack without any electrocardiographic ST-T changes. The coronary angiogram did not show any significant lesions, but the aortic root angiogram showed massive aortic regurgitation. Surgery revealed a bicuspid aortic valve with a conjoined cusp that had a fenestrated raphe torn away from the aortic wall and prolapsing into the left ventricle. The aortic valve was successfully replaced with a St Jude Medical mechanical valve prosthesis. The pathological significance of the intact raphal cord and the rupture remains an unsolved problem. This is the first reported case in which an increase of aortic regurgitation due to a ruptured raphal cord supporting the conjoined cusp was confirmed by a serial root angiogram.

The aortic valve with two leaflets--a study in 2,000 autopsies

Our study is based on the examination of 2,000 aortic valves obtained from fresh cadavers (1,499 males, 501 females) at the Institute of Forensic Medicine in Rio de Janeiro. We discovered 13 valves having two leaflets, giving a prevalence of 0.65%, much lower than generally reported in the literature. All 13 valves were from males, 10 from whites, three from mulattos, and none from blacks. Special attention was given to the raphe and the leaflets, the calcification of which can lead to stenosis. The only valves with normal texture and flexibility were two obtained from children less than one year old. All the other valves were thickened, and five of them had some degree of calcification. Six valves were judged to be functioning normally, while 7 valves were abnormal, 5 being stenotic and two showing evidence of insufficiency. The insufficiency in one was due to endocarditis, but in the other was due to redundancy of the leaflets. The only other cardiac anomaly discovered in these 13 cases was one patient with aortic coarctation. Bifoliate aortic valve, therefore, is probably the most common cardiac anomaly, although its prevalence as discovered in Brazil is lower than that reported in the literature. It affects mainly white males. After the fourth decade of life, most valves present some thickening, with stenosis being the most common complication. As is well recognised, infective endocarditis and aortic insufficiency are the other frequent complications. It is in general, nonetheless, an isolated anomaly.

Congenitally bicuspid aortic valves: a surgical pathology study of 542 cases (1991 through 1996) and a literature review of 2,715 additional cases

OBJECTIVE

To describe a clinicopathologic study of a large group of congenitally bicuspid aortic valves surgically excised at a single institution.

MATERIAL AND METHODS

The medical charts and bicuspid valves from patients undergoing aortic valve replacement at Mayo Clinic Rochester between 1991 and 1996 were retrospectively reviewed.

RESULTS

The age of the 542 patients ranged from 1 to 86 years (mean, 61), and 372 (69%) were men. Among these, 409 (75%) had pure aortic stenosis (AS), 73 (13%) had pure aortic insufficiency (regurgitation) (AI), 53 (10%) had combined AS and AI, and 7 (1%) had normal function. The mean age was higher for those with AS than AI (65 versus 46 years; P < 0.001), whereas the male-to-female ratio was higher for AI than AS (17.3:1 versus 1.7:1; P < 0.001). The two cusps were not equal in size in 95%, and a raphe was present in 76% (67% typical, 9% atypical). Raphal position was described in 315 and was between the right and left cusps in 270 (86%). Raphal absence occurred more often in valves with equal-sized cusps than unequal (33% versus 14%; P = 0.005). Moderate to severe calcification affected valves with AS more frequently than AI (99% versus 41%; P < 0.001). In contrast, annular dilatation was associated with AI more than AS (48% versus 11%; P < 0.001). Acquired commissural fusion involved valves with combined AS and AI more often than the other functional states (31% versus 14%; P = 0.002). Sixteen patients (age range, 18 to 78 years; 13 men) had infective endocarditis (6 active, 10 healed), including 10 with AI (9 men), 3 with AS plus AI, 2 with AS, and 1 with normal function but embolization.

CONCLUSION

Functionally, the most common fate of congenitally bicuspid aortic valves was calcific stenosis with or without regurgitation (85%). Because approximately 4 million US citizens have bicuspid valves and because valve replacement is currently the only treatment of symptomatic AS, this disorder will continue to affect health-care costs.

Catheter-based intravascular ultrasound discriminates bicuspid from tricuspid valves in adults with calcific aortic stenosis

A catheter-based intravascular ultrasound transducer was used to study aortic valve morphology in adults with calcific aortic stenosis. Examination of 14 postmortem specimens disclosed that intravascular ultrasound consistently identified the number of cusps or the presence of a calcified median raphe in the conjoined cusp, or both, and thereby distinguished a calcified bicuspid from a calcified tricuspid aortic valve. These postmortem findings were then employed to identify valvular morphology in 15 patients undergoing diagnostic cardiac catheterization or balloon aortic valvuloplasty, or both. Reproduction of criteria established in vitro allowed discrimination of congenital valvular morphology in all 15 patients, including 7 in whom assessment by intravascular ultrasound was confirmed by subsequent pathologic examination. Identification of aortic valvular morphology by intravascular ultrasound has potential therapeutic implications for patients considered to be candidates for operative or nonoperative aortic valvuloplasty.

Contrasting histoarchitecture of calcified leaflets from stenotic bicuspid versus stenotic tricuspid aortic valves

Preliminary findings from clinical trials of percutaneous balloon aortic valvuloplasty and intraoperative debridement of calcific deposits in patients with aortic stenosis have suggested that calcified, congenitally bicuspid aortic valves may be less amenable to these techniques than are calcified tricuspid aortic valves. Accordingly, we evaluated the histoarchitecture of calcific deposits in 30 operatively excised aortic valves. Light microscopic sections taken through the calcified aortic valve leaflets disclosed two principal types of histoarchitecture. In 11 aortic valves nodular calcific deposits were superimposed on an underlying fibrotic aortic valve leaflet (type A); in 17 valves calcific deposits were diffusely distributed throughout the body (spongiosa) of the aortic valve leaflets (type B). Two aortic valves could not be classified histologically. These histologic subtypes were not randomly distributed with regard to gross valvular morphology. All 14 bicuspid valves (100%) were type B; in contrast, 11 (69%) of 16 tricuspid aortic valves were type A, and only 3 (19%) of 16 tricuspid valves were type B (p less than 0.01). Both valves with nonclassifiable histologic features were tricuspid on the basis of gross examination. Thus, the histoarchitectural distribution of calcific deposits is different for bicuspid than for tricuspid stenotic aortic valves. The more diffuse distribution of calcium throughout the body of calcified bicuspid aortic valve leaflets may render these valves less amenable to operative and percutaneous valvuloplasty than are calcified tricuspid aortic valve leaflets on which calcific deposits are typically superimposed in nodular form.

Prevalence and characteristics of the aortic ejection sound in adults

A survey of 1,950 phonocardiograms recorded over a 6-year period revealed 170 (9%) with a distinct aortic ejection sound. All patients were men with a mean age of 61 years (range 29 to 88). Associated clinical features were: aortic stenosis in 28%, history of systemic hypertension in 10%, history of rheumatic fever in 4% and none of these features in 58% of patients. In 141 (83%) of 170 patients the aortic ejection sound occurred simultaneously with or 0.01 second before or after the onset of the rise of the externally recorded carotid pulse. In 37 (66%) of 56 patients who had simultaneous echocardiograms and phonocardiograms recorded, the aortic ejection sound occurred at 0.01 second before or after the maximal opening point of the aortic valve leaflets. Two-dimensional echocardiography was performed in all patients and a bicuspid aortic valve was identified in 38 patients (22%). In 83 patients (49%) 3 cusps were clearly seen. In 49 patients (29%) an accurate determination was not possible. Anatomic examination of 120 consecutive aortic valves at autopsy was performed to identify possible causes of the aortic ejection sound. In 18 (15%) of autopsies fusion of 2 aortic cusps extending greater than or equal to 5 mm from the attachment to the aorta was observed. This abnormality, aortic commissural fusion, may be congenital or acquired. It is concluded that aortic ejection sounds may occur in patients without bicuspid aortic valves and in a variety of clinical conditions. A moderate degree of cuspal fusion may be the cause of the sound.

Patterns of calcific deposits in operatively excised stenotic or purely regurgitant aortic valves and their relation to mechanical stress

Two hundred twenty-one aortic cusps from 96 patients who underwent aortic valve replacement were examined. Of all the cusps that showed any calcific deposits, 87% had calcific deposits in 1 of 2 specific patterns: a coaptation pattern, where calcific deposits occurred along the line of cusp coaptation, and a radial pattern, where calcific deposits occurred as spokes spread inward from the cusp attachment to the center of the cusp. This was true irrespective of the patients' sex or age, the type of disease, and the type of valve or the extent of calcific deposits. These patterns of calcific deposits relate to the area of maximal cusp flexion and, hence, maximal mechanical stress. It is therefore concluded that calcific deposits in aortic valve cusps occur in specific patterns in most cases, and that mechanical stress may be the initiating or accelerating factor in the calcification of these cusps.

Surgical pathology of pure aortic insufficiency: a study of 225 cases

The gross surgical pathologic features of the aortic valve were reviewed in 225 patients who had had clinically pure aortic insufficiency and aortic valve replacement at our institution during the years 1965, 1970, 1975, and 1980. The four most common causes of aortic regurgitation were postinflammatory disease (46%), aortic root dilatation (21%), incomplete closure of a congenitally bicuspid aortic valve (20%), and infective endocarditis (9%). Other causes of aortic incompetence in our study included ventricular septal defects (2%) and quadricuspid aortic valves (1%); the cause was indeterminate in 1%. The mean age of patients at valve replacement was approximately 50 years for all etiologic factors except a ventricular septal defect. All forms of aortic insufficiency were much more common in male than in female patients, except the postinflammatory and indeterminate types, which occurred approximately equally in both sexes. Moreover, the incidences of postinflammatory disease and aortic root dilatation changed appreciably with time. Before 1980, their incidences were 51% and 17%, respectively, but during 1980, they were 29% and 37%, respectively. Accordingly, aortic root dilatation is now the most common cause of pure aortic regurgitation in our surgical population. The decrease in the incidence of postinflammatory disease may be a result of the decreasing incidence of acute rheumatic fever reported in western countries.

Coronary arterial anatomy in bicuspid aortic valve. Necropsy study of 100 hearts

In a necropsy study, the conjoined cusps of 50 congenitally and 50 acquired bicuspid aortic valves most commonly involved the right and left aortic cusps. In hearts with congenitally bicuspid aortic valves, the left coronary ostium arose at or above the aortic sinotubular junction in 44 per cent, whereas the incidence for the left coronary ostium in the acquired group was 20 per cent and that for the right coronary ostium in both groups was less than 20 per cent. In hearts with congenitally bicuspid aortic valves, the incidence of left coronary dominance (26%) was higher than in normal hearts. In hearts with apparently acquired bicuspid aortic valves, this incidence was also higher than normal, possibly because of acquired fusion of atypical congenitally bicuspid valves in some cases. In both types of aortic valve disease, the length of the left main coronary artery was similar; this length, however, was significantly shorter in hearts with left coronary dominance than in those with right or shared dominance.

The ascending aorta in aortic stenosis

Dilatation of the ascending aorta, a frequently reported sign of aortic stenosis, was assessed in 47 patients for whom aortic angiograms has been recorded. Twenty-eight of the patients had rheumatic valvar disease and 19 had congenital aortic stenosis. A simple ratio between the maximal width of the mid-ascending aorta and the width of the aortic root was calculated. Patients with congenital aortic stenosis had significantly greater supravalvar aortic dilatation than did those with rheumatic aortic valve involvement. There was no correlation between the pressure difference across the aortic valve and degree of dilatation of the ascending aorta.

Spontaneous rupture of bicuspid aortic valve. An unusual cause of aortic insufficiency

This report documents the clinicopathologic correlation between pure aortic regurgitation and an exceptional form of congenitally bicuspid aortic valve. The patient was known for many years to have mild aortic insufficiency. His condition suddenly deteriorated, with signs of an aggravated aortic regurgitation. Infectious endocarditis was considered, but the diagnosis was never established. Surgery revealed an exceptional form of a bicuspid aortic valve in which the conjoined cusp had prolapsed, due to rupture of a fibrous strand which previously had anchored the free rim of the cusp to the inner wall of the aorta. There were no signs of infectious endocarditis. It is suggested that spontaneous rupture of the cord caused the sudden aggravation of aortic regurgitation.

Congenital bicuspid aortic valve after age 20

The bicuspid aortic valve is recognized as a frequent cause of aortic stenosis in adults. Aortic stenosis has been reported to occur in as many as 72 percent of adults with a congenital bicuspid aortic valve, with peak incidence occurring in the 5th and 6th decades of life. Review of the clinical records of 152 patients aged 20 years and older found to have a bicuspid aortic valve at autopsy revealed aortic stenosis in only 28 percent. The incidence of aortic stenosis increased progressively with age; 46 percent of patients over age 50 years and 73 percent over age 70 years had some degree of stenosis. The stenotic valves were obstructed by nodular, calcareous masses but commissural fusion was present in only eight cases. The largest group of patients in the series (40 percent) died of infective endocarditis; 77 percent of these were under age 50 years. Primary aortic regurgitation without infective endocarditis was uncommon. Thirty-two percent of the patients in this series had an apparently normally functioning aortic valve, and this rate remained relatively constant with increasing age; 37 percent of patients over age 50 years and 27 percent over age 70 years had an apparently normal valve. The bicuspid aortic valve in patients over age 20 does not invariably become stenotic or insufficient.

Familial supravalvular aortic stenosis. Report of a large family and review of the literature

Familial supravalvular aortic stenosis has been recognized as a distinct syndrome. A large family with five proven cases and a review of the literature on familial supravalvular aortic stenosis are presented. The diagnosis was substantiated in all 63 cases by cardiac catheterization, surgery, or postmortem examination.