eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiology
Aortic Valve, Bicuspid
Updated: Nov 13, 2009
Introduction
Background
Sir William Osler was one of the first to recognize the bicuspid aortic valve as a common congenital anomaly of the heart.1 Leonardo da Vinci recognized the superior engineering advantages of the normal trileaflet valve.2 However, bicuspid aortic valve is mentioned only briefly in many pediatric and cardiology textbooks.
Definition
The normal aortic valve has 3 equal-sized leaflets or cusps with 3 lines of coaptation. A congenitally bicuspid aortic valve has 2 functional leaflets. Most have one complete line of coaptation. Approximately half of cases have a low raphe. Stenotic or partially fused valves caused by inflammatory processes, such as rheumatic fever, are not included.
Embryology
The embryonic truncus arteriosus is divided by the spiral conotruncal septum during development. The normal right and left aortic leaflets form at the junction of the ventricular and arterial ends of the conotruncal channel. The nonseptal leaflet (posterior) cusp normally forms from additional conotruncal channel tissue. Abnormalities in this area lead to the development of a bicuspid valve, often through incomplete separation (or fusion) of valve tissue.3
Bicuspid aortic valve is often observed with other left-sided obstructive lesions such as coarctation of the aorta or interrupted aortic arch, suggesting a common developmental mechanism.4 Specific gene mutations have been isolated.5
Anatomy
The bicuspid valve is composed of 2 leaflets or cusps, usually of unequal size.6,7
Bicuspid aortic valve with unequal cusp size. Note eccentric commissure and raphe.
The larger leaflet is referred to as the conjoined leaflet. Two commissures (or hinge points) are present; usually, neither is partially fused. The presence of a partially fused commissure, which has also been called a high raphe, probably predisposes toward eventual stenosis. At least half of all congenitally bicuspid valves have a low raphe, which never attains the plane of the attachments of the two commissures and never extends to the free margin of the conjoined cusp. Redundancy of a conjoined leaflet may lead to prolapse and insufficiency.8
Valve leaflet orientation and morphology can vary. A recent surgical study showed conjoined leaflets in 76% of specimens.9 Of these, fusion of the raphe was noted between the right and left cusps in 86%, and fusion was noted between the left and noncoronary cusps in only 3%. Of the valves without raphes, more than 30% of the leaflets were unequal in size.
Coronary arteries may be abnormal.7 A left-dominant coronary system (ie, posterior-descending coronary artery arising from the left coronary artery) is more commonly observed with bicuspid aortic valve. Rarely, the left coronary artery may arise anomalously from the pulmonary artery. The left main coronary artery may be up to 50% shorter in patients with a bicuspid aortic valve. Occasionally, the coronary ostium may be congenitally stenotic in association with bicuspid aortic valve.
The aortic root may be dilated.10 This dilatation has some similarities to the dilatation of the aorta seen in Marfan syndrome.11,12 The dilatation may involve the ascending aorta (most commonly) but may also involve the aortic root or transverse aortic arch.13,14 A recent study compared aortic dilation in children who had bicuspid aortic valve with and without coarctation of the aorta; the conclusion was that valve morphologic characteristics and function and age at the time of coarctation of the aorta repair had no impact to minimal impact on aortic dimensions.15
Pathophysiology
With degeneration of aging valves, sclerosis and calcification can occur. The changes are similar to those in atherosclerotic coronary arteries. The bicuspid valve may also be completely competent, producing no regurgitant flow. However, redundancy and prolapse of cusp tissue can lead to valve regurgitation. Complications arise in as many as one third of patients over their lifetimes;16 this disorder, therefore, deserves close attention and medical follow-up.
Valve morphology may be predictive of problems of stenosis, insufficiency, or both. Fusion along the right or left leaflets is less commonly associated with stenosis or insufficiency in children. This arrangement is much more common in patients with coarctation of the aorta, whose valves function adequately. Fusion along the right and noncoronary leaflets is more frequently associated with pathologic changes of stenosis or insufficiency in the pediatric population.17
Frequency
United States
Bicuspid aortic valves may be present in as many as 1-2% of the population. Because the bicuspid valve may be entirely silent during infancy, childhood, and adolescence, these incidence figures may be underestimated and are not generally included in the overall incidence of congenital heart disease.
International
Incidence does not appear to be affected by geography.
Race
A recent report suggests much lower than expected prevalence in African-Americans.18
Sex
The male-to-female ratio is 2:1 or greater. Sex is not a predictive variable in the natural history of bicuspid aortic valve. A recent prospective echocardiographic study in newborn infants showed a prevalence of bicuspid aortic valve in 7.1 per 1,000 male newborns versus 1.9 per 1,000 female newborns.19
Age
Bicuspid aortic valve may be identified in patients of any age, from birth through the 11th decade of life. It may be only an incidental finding at autopsy. Bicuspid aortic valve may remain silent and be discovered as an incidental finding on echocardiographic examination of the heart.
Critical aortic stenosis and infective endocarditis may be considered relatively early sources of morbidity for patients with bicuspid aortic valve. Critical aortic stenosis may occur in infancy and may be associated with a bicuspid valve.
Occasionally, bicuspid aortic valve is diagnosed after a patient has developed infective endocarditis with systemic embolization.
Stenosis of a bicuspid aortic valve is more likely to develop in persons older than 20 years and is caused by progressive sclerosis and calcification. High levels of serum cholesterol have been associated with more rapidly progressive sclerosis of the congenitally bicuspid aortic valve.20
Children who develop early progressive, pathologic changes in the bicuspid aortic valve are more likely to develop valve regurgitation than stenosis. Bicuspid aortic valve was identified in 167 (0.8%) of 20,946 young Italian military conscripts. Of these, 110 were found to have either mild or moderate aortic insufficiency.
Clinical
History
Patients with bicuspid aortic valves may be completely asymptomatic. About 30% of individuals with a bicuspid aortic valve develop complications.17,21,22 If symptoms are present, they relate to the development of aortic stenosis, aortic insufficiency, or both. Occasionally, a congenitally bicuspid aortic valve may be the cause of critical aortic stenosis, with symptoms of severe congestive heart failure developing in early infancy. This critical form of stenosis is more frequently associated with a unicommissural valve. In patients in whom a bicuspid aortic valve is observed in association with other types of left heart obstruction (coarctation or interrupted aortic arch), the bicuspid valve generally functions well, and symptoms are usually caused by the associated disorder.
- Inheritance: Although most cases of bicuspid aortic valve are sporadic, familial clusters have been identified, with incidence as high as 10-17% in first-degree relatives of probands.23 Increasing evidence suggests an autosomal-dominant inheritance pattern with variable penetrance, encompassing the entire spectrum of left heart obstruction (hypoplastic left heart syndrome, aortic stenosis, coarctation of the aorta)24
- Associated syndromes
- Coarctation or interrupted aortic arch (bicuspid aortic valve is present in >50% of patients with these lesions)4
- Williams syndrome (bicuspid aortic valve associated with supravalvular aortic stenosis occurs in 11.6% of cases)25
- Patent ductus arteriosus, also associated with hand anomalies26
- Turner syndrome (bicuspid aortic valve occurs in 30% of patients)27
Physical
Because the bicuspid aortic valve is frequently a clinically silent condition, general examination findings may be normal.
- Typical features of Turner syndrome (eg, short stature in females with webbed neck and broad chest) or Williams syndrome (eg, elfin facies, mild retardation) may suggest the possibility of bicuspid aortic valve.
- Cardiac examination findings include the following:
- The precordium is usually normal to palpation, and no evidence of cardiomegaly is present.
- The first heart sound is unaffected. The second heart sound splits normally with inspiration, with absent or minimal outflow gradient. With increasing aortic stenosis gradient, the splitting of the second sound is less apparent or may be absent. With severe stenosis, the second sound is split paradoxically (ie, with expiration). This splitting differs from normal splitting of the first heart sound (ie, with tricuspid and mitral valve closures) in that normal splitting is best appreciated at the lower left sternal border and is a softer lower-pitched sound than the click of a bicuspid aortic valve.
- The most common abnormal sound heard with bicuspid aortic valve is a systolic ejection click. This sound is actually a less-distinct, medium-pitched, short sound heard well at the apex with the diaphragm of the stethoscope. It is heard in all phases of respiration just after the first heart sound, and its timing does not vary with maneuvers (eg, hand-grip, Valsalva, squatting). The ejection sound may also be heard in the aortic area (upper right sternal border), where it takes on a brighter and sharper quality.28
- In contrast, the click of pulmonary valvular stenosis is intermittent (heard best during expiration) and located closer to the left sternal border. It is a bit less distinct than the aortic valve click. The click of mitral valve prolapse may also be heard at the apex but is softer, occurs later, and is less distinct than the bicuspid aortic valve click. The mitral prolapse click often varies in timing with changes in position or isometric handgrip and may be followed by the murmur of mitral regurgitation. Multiple showers of clicks are common, and the sound has been likened to crinkling cellophane.
- Minimal or mild stenosis may produce a soft and fairly harsh ejection murmur at the upper right sternal border with possible radiation into the carotids. Increasing severity of stenosis produces a longer, louder, and harsher murmur with definite radiation into the carotids and possibly into the posterior shoulder. With more severe stenosis, a thrill may be felt in the suprasternal notch.
- In the presence of a typical ejection click, the high-pitched sound of subtle aortic valve insufficiency may be heard at the third left intercostal space with the diaphragm of the stethoscope. Various maneuvers may be helpful in auscultation, including having the patient perform an isometric handgrip, having patients lean forward in a seated position (to bring the aortic area closer to the chest wall), and having patients hold their breath in expiration (also decreases the distance between the stethoscope and the left ventricle).28
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References
Keith JD. Bicuspid aortic valve. In: Keith JD, Rowe RD, Vlad P. Heart Disease in Infancy and Childhood. New York: MacMillan Publishing Co, Inc.; 1978:728-35.
Hajar R. Da Vinci's anatomical drawings the heart. Heart Views [serial online]. 3(2):Available at www.hmc.org.qa/hmc/heartviews/H-V-v3%20N2/8.htm.
Titus JL, Edwards JE. The aortic root and valve: Anatomy and congenital anomalies. In: Emery RW, Arom KV. The Aortic Valve. Philadelphia: Hanley & Belfus, Inc.; 1991:1-8.
Duran AC, Frescura C, Sans-Coma V, et al. Bicuspid aortic valves in hearts with other congenital heart disease. J Heart Valve Dis. Nov 1995;4(6):581-90. [Medline].
Ellison JW, Yagubyan M, Majumdar R, et al. Evidence of genetic locus heterogeneity for familial bicuspid aortic valve. J Surg Res. Sep 2007;142(1):28-31. [Medline].
Roberts WC. Morphologic aspects of cardiac valve dysfunction. Am Heart J. Jun 1992;123(6):1610-32. [Medline].
Roberts WC. The congenitally bicuspid aortic valve. A study of 85 autopsy cases. Am J Cardiol. Jul 1970;26(1):72-83. [Medline].
Sadee AS, Becker AE, Verheul HA, et al. Aortic valve regurgitation and the congenitally bicuspid aortic valve: a clinico-pathological correlation. Br Heart J. Jun 1992;67(6):439-41. [Medline].
Sabet HY, Edwards WD, Tazelaar HD, Daly RC. Congenitally bicuspid aortic valves: a surgical pathology study of 542 cases (1991 through 1996) and a literature review of 2,715 additional cases. Mayo Clin Proc. Jan 1999;74(1):14-26. [Medline].
Della Corte A, Bancone C, Quarto C, et al. Predictors of ascending aortic dilatation with bicuspid aortic valve: a wide spectrum of disease expression. Eur J Cardiothorac Surg. Mar 2007;31(3):397-404; discussion 404-5. [Medline].
de Sa M, Moshkovitz Y, Butany J, David TE. Histologic abnormalities of the ascending aorta and pulmonary trunk in patients with bicuspid aortic valve disease: clinical relevance to the ross procedure. J Thorac Cardiovasc Surg. Oct 1999;118(4):588-94. [Medline].
[Guideline] Bonow RO. Bicuspid aortic valves and dilated aortas: a critical review of the ACC/AHA practice guidelines recommendations. Am J Cardiol. Jul 1 2008;102(1):111-4. [Medline].
Schaefer BM, Lewin MB, Stout KK, et al. The Bicuspid Aortic Valve: An Integrated Phenotypic Classification of Leaflet Morphology and Aortic Root Shape. Heart. Feb 28 2008;[Medline].
Fazel SS, Mallidi HR, Lee RS, Sheehan MP, Liang D, Fleischman D, et al. The aortopathy of bicuspid aortic valve disease has distinctive patterns and usually involves the transverse aortic arch. J Thorac Cardiovasc Surg. Apr 2008;135(4):901-7, 907.e1-2. [Medline].
Beaton AZ, Nguyen T, Lai WW, et al. Relation of coarctation of the aorta to the occurrence of ascending aortic dilation in children and young adults with bicuspid aortic valves. Am J Cardiol. Jan 15 2009;103(2):266-70. [Medline].
Ward C. Clinical significance of the bicuspid aortic valve. Heart. Jan 2000;83(1):81-5. [Medline].
Kitchiner D, Jackson M, Walsh K, et al. The progression of mild congenital aortic valve stenosis from childhood into adult life. Int J Cardiol. Dec 31 1993;42(3):217-23. [Medline].
Khan W, Milsevic M, Salciccioli L, Lazar J. Low prevalence of bicuspid aortic valve in African Americans. Am Heart J. Sep 2008;156(3):e25. [Medline].
Tutar E, Ekici F, Atalay S, Nacar N. The prevalence of bicuspid aortic valve in newborns by echocardiographic screening. Am Heart J. Sep 2005;150(3):513-5. [Medline].
Chui MC, Newby DE, Panarelli M, Bloomfield P, Boon NA. Association between calcific aortic stenosis and hypercholesterolemia: is there a need for a randomized controlled trial of cholesterol-lowering therapy?. Clin Cardiol. Jan 2001;24(1):52-5. [Medline].
Lamas CC, Eykyn SJ. Bicuspid aortic valve--A silent danger: analysis of 50 cases of infective endocarditis. Clin Infect Dis. Feb 2000;30(2):336-41. [Medline].
Beppu S, Suzuki S, Matsuda H, et al. Rapidity of progression of aortic stenosis in patients with congenital bicuspid aortic valves. Am J Cardiol. Feb 1 1993;71(4):322-7. [Medline].
Cripe L, Andelfinger G, Martin LJ, et al. Bicuspid aortic valve is heritable. J Am Coll Cardiol. Jul 7 2004;44(1):138-43. [Medline].
Wessels MW, Berger RM, Frohn-Mulder IM, et al. Autosomal dominant inheritance of left ventricular outflow tract obstruction. Am J Med Genet A. Apr 15 2005;134(2):171-9. [Medline].
Hallidie-Smith KA, Karas S. Cardiac anomalies in Williams-Beuren syndrome. Arch Dis Child. Jul 1988;63(7):809-13. [Medline].
Gelb BD, Zhang J, Sommer RJ, Wasserman JM, Reitman MJ, Willner JP. Familial patent ductus arteriosus and bicuspid aortic valve with hand anomalies: a novel heart-hand syndrome. Am J Med Genet. Nov 19 1999;87(2):175-9. [Medline].
Sachdev V, Matura LA, Sidenko S, et al. Aortic valve disease in Turner syndrome. J Am Coll Cardiol. May 13 2008;51(19):1904-9. [Medline].
Zuberbuhler JR. Aortic stenosis. In: Clinical Diagnosis in Pediatric Cardiology. London, England: Churchill Livingstone; 1981:75-82.
Brandenburg RO Jr, Tajik AJ, Edwards WD, et al. Accuracy of 2-dimensional echocardiographic diagnosis of congenitally bicuspid aortic valve: echocardiographic-anatomic correlation in 115 patients. Am J Cardiol. May 15 1983;51(9):1469-73. [Medline].
Freedom RM, Mawson JB, Yoo SJ. Left ventricular outflow tract obstruction. In: Congenital heart disease: Textbook of angiocardiography. Armonk, NY: Futura Publishing Company, Inc; 1997:787-847.
McKusick VA. Bicuspid aortic valve. Online Mendelian Inheritance in Man, OMIM [serial online]. Accessed 7/2/1998. [Medline]. Available at http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?109730.
[Guideline] Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: guidelines from the American Heart Association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. Circulation. Oct 9 2007;116(15):1736-54. [Medline].
Stefani L, Galanti G, Toncelli L, et al. Bicuspid aortic valve in competitive athletes. Br J Sports Med. Jan 2008;42(1):31-5; discussion 35. [Medline].
De Mozzi P, Longo UG, Galanti G, Maffulli N. Bicuspid aortic valve: a literature review and its impact on sport activity. Br Med Bull. 2008;85:63-85. [Medline].
Brook MM. Pediatric bacterial endocarditis. Treatment and prophylaxis. Pediatr Clin North Am. Apr 1999;46(2):275-87. [Medline].
Parai JL, Masters RG, Walley VM, et al. Aortic medial changes associated with bicuspid aortic valve: myth or reality?. Can J Cardiol. Nov 1999;15(11):1233-8. [Medline].
Further Reading
Keywords
bicuspid valve, bicuspid aortic valve, bicommissural aortic valve, rheumatic fever, truncus arteriosus, coarctation of the aorta, interrupted aortic arch, Marfan syndrome, aortic insufficiency, hypoplastic left heart syndrome, patent ductus arteriosus, Turner syndrome, short stature, Williams syndrome
