Asian Cardiovasc Thorac Ann 2006;14:210-212
© 2006 Asia Publishing EXchange Ltd
Clinical Characteristics of Bicuspid Aortic Valves in Surgical Patients
Toshihiko Ichihara, MD,
Genyo Fujii, MD,
Michio Sasaki, MD,
Osamu Kawaguchi, PhD1,
Yuichi Ueda, PhD2
Department of Cardiovascular Surgery, Tosei General Hospital
1 Department of Cardiac Surgery, Aichi Medical School
2 Department of Cardiothoracic Surgery, Nagoya University School of Medicine, Aichi, Japan
For reprint information contact: Toshihiko Ichihara, MD Tel: 81 561 825 101 Fax: 81 561 829 139 Email:hniinami{at}med.juntendo.ac.jp, 160 Nishioiwake-cho, Seto, Aichi 489-8642, Japan.
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ABSTRACT
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Of 413 patients undergoing surgery for aortic valve disease, 42 were confirmed to have congenital bicuspid aortic valve. There were 24 males and 18 females, with a mean age of 54.9 ± 14.6 years. The etiology of the surgical indications in patients with bicuspid valves were degeneration, rheumatic disease, and infectious endocarditis. Thirty-two patients had aortic stenosis and 10 had aortic regurgitation. Infective endocarditis was seen mainly in patients 
50 years of age at the time of surgery, while degenerative aortic stenosis occurred more often in older patients. The annular diameter measured during surgery was significantly narrower in the 42 patients with bicuspid valves compared to 371 patients with tricuspid valves who underwent aortic valve replacement during the same period. It is important to prevent infectious endocarditis in younger patients diagnosed with bicuspid aortic valve, whereas careful attention should be paid to decalcification during surgery in older patients because the vast majority suffer from degenerative aortic stenosis.
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INTRODUCTION
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The number of patients undergoing surgery for aortic valve (AV) stenosis has been increasing as society ages. Consequently, the chance of encountering a bicuspid aortic valve has also increased. Studies have been conducted on the pathology of patients with a bicuspid AV, but there are few reports of the relationship of valve structure to pathological findings and surgery, because of the limited number of cases. Patients who underwent AV surgery over a period of 24 years were reviewed to obtain a better picture of the parameters of congenital bicuspid AV based on the anatomical characteristics, annular diameter, and etiology.
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PATIENTS AND METHODS
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Aortic valve surgery was performed in 413 patients, including those with multiple valve disease, from September 1981 to December 2004. It was confirmed through a review of the surgical records that 42 (10%) of these patients (24 males, 18 females) had a bicuspid AV. Their mean age was 54.9 ± 14.6 years, with a range of 18 to 77 years. Following the definition of bicuspid AV proposed by Edwards,1 bicuspid valves that were judged to be congenital in nature were included, while acquired bicuspid valves resulting from fusion of valve leaflets caused by inflammation were excluded. The hemodynamic characteristics of each patient were classified as pure aortic stenosis (AS) or AS-dominant with a pressure gradient of 50 mm Hg or higher (32 patients), or pure aortic regurgitation (AR) or AR-dominant with Sellers III or higher regurgitation (10 patients). The etiology was classified as degenerative (senile), rheumatic disease, or infective endocarditis, based on the case history, operative findings, and pathology obtained from an aortic valve specimen. Measurement of the annular diameter of the aortic valve was conducted under cardioplegic arrest with the myocardium relaxed. The leaflets were excised with as much as possible of the calcified portion of the annulus. A cylinder-type sizer (Mera Inc., Tokyo, Japan), which comes in increments of 2 mm, was inserted for measurement. The bicuspid valve patients were studied from the standpoints of age, hemodynamics, pathology, and morphology.
In the statistical analysis, variables were expressed as the mean ± standard deviation, and the chi-squared and Fisher tests were used for comparison of the frequency of variables between the 2 groups, with a Yates correction employed depending on the variable. Statistical significance was accepted at p < 0.05.
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RESULTS
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The mean annular diameter index of all 42 patients with bicuspid AV was 0.46 cm2, and it was 0.3 cm2 in those with AS. In addition, the annulus ring diameter index was greater in younger patients compared to those aged over 50 years. The mean annular diameter measured during surgery in the 371 patients with a tricuspid AV was 23.6 ± 1.8 mm. The size of the inserted artificial valve (St. Jude Medical, Inc., St. Paul, MN, USA) was 21 mm in 174 patients (47%) and 
23 mm in 197 patients (53%). In contrast, the mean annular diameter of bicuspid aortic valves measured during surgery was narrower at 21.6 ± 1.9 mm ( p < 0.05), and the inserted artificial valve size was 21 mm in 26 patients (62%) and 23 mm in 16 (38%). Thus, a small artificial valve ( 21 mm) was selected more often in patients with a bicuspid AV.
The etiology of AV disease in patients with bicuspid AV was rheumatic (16%), degenerative (69.5%), and infective endocarditis (14.5%), with a significantly lower rate of rheumatic disease compared to tricuspid AV patients (Table 1
). The age distribution of bicuspid AV patients revealed that rheumatic disease was highest among those who were 50 years of age, while degeneration was highest among patients over 50 years old. Looking at the distribution by age and morphology, AS was dominant among patients > 50 years of age, while AR was dominant among those 50 years old. No correlation was found between the presence of a raphe and a stenotic or regurgitant lesion. No statistically significant difference was found between annular size and the presence of a raphe. The mean pressure gradient across the aortic valve in patients with AS was 80 mm Hg. The mean pressure gradient in those > 50 years old was 86 mm Hg, but among the patients presenting with AS, there was no significant difference between the younger and older age groups. The weights of the excised valves were not measured in this series.
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DISCUSSION
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The majority of patients with a congenital bicuspid AV exhibit no symptoms or clinical signs. According to Roberts,2 the bicuspid valve is pathologically significant in approximately 9% to 17% of patients with AV disease. Previous reports have underscored that the number of such patients is limited, and looked at the significance of the presence of a raphe and lesions. They found that many individuals with a bicuspid AV develop AS, particularly at a younger age than those with a tricuspid valve. They also found that few individuals with a bicuspid AV developed AR, a findings in agreement with our result.2 Valvular stenosis is triggered by deposition of calcium. In the absence of commissural fusions, a warning sign of bicuspid AS is calcification mainly in the commissures and annulus. The frequency of calcification also normally increases in patients with tricuspid valves after the age of 40, with the valve becoming dystrophic, and stenotic appearing. However, this process occurs earlier in patients with bicuspid valves. Mark and colleagues3 stated that the cause of this earlier onset is that calcification of the bicuspid AV starts first at the site of a raphe. Subramanian and colleagues4 found that the raphe is made up of elastic fibers that are coarse and easily destroyed with calcification, and that the presence of a raphe morphologically was a significant factor in the development of stenosis. Similarly Angelini5 reported that a raphe was present in 64% of patients with a bicuspid AV and AS. In contrast, Edwards1,6 found that a group of patients without raphes had AS predominantly, and he theorized that the stenosis was caused by shortening of the margin of the two cusps during movement in the systole phase.
In our bicuspid series, the aortic root was not dilated in any patient, and the sinotubular junction tended to be narrow. No conclusion can be made about the importance of the presence of a raphe based on these reports. Our bicuspid valves investigation classified patients into 4 subgroups based on the morphology of the commissures and leaflets, and it was found that they were AS dominant regardless of the presence of raphes and the positional relationship between the commissures and the leaflets. It was concluded that there was no difference based on morphology, including the presence of a raphe, with regard to AS and AR. Our data support the results of Mills and colleagues.7 Roberts8 classified bicuspid AV patients based on the presence of a raphe. It was found that the majority of those with a raphe were male, young at the time of surgery, and had unequal cusp sizes; AR was present in 55%. The patients without a raphe showed no sex bias, equal cusp size, and 76% had AS. This contrasted with the present study in which there was no sex-bias in the presence of a raphe.
Robicsek9 stated that all bicuspid aortic valves are forms of stricture by nature. A bicuspid AV creates turbulence and abnormally high stresses and may lead to early thickening and eventually to calcification and stenosis. The abnormal flow patterns also promote dilatation and dissection of the ascending aorta. Lewin and Otto10 thought the prevalence of congenitally malformed aortic valves may be underestimated. Although it has long been recognized that the 3 most common causes of aortic stenosis are a bicuspid valve, rheumatic disease, and calcification of a trileaflet valve, previous reports of the prevalence of bicuspid AV were based on surgical series that most likely included patients with rheumatic disease. Roberts and Ko11 reported that the prevalence of bicuspid AV was 53% in a consecutive series of 933 patients undergoing valve replacement for isolated AS.
Casselman and colleagues12 proposed aortic valvuloplasty for patients with a bicuspid AV. However, only 2 (4.7%) of the patients without infective endocarditis in this study had bicuspid AR, and the need to perform valvuloplasty in bicuspid AV patients would be extremely limited. It was concluded that the etiological factor leading to surgery for a bicuspid AV was primarily degeneration in older patients and infective endocarditis in younger patients. In addition, the annular diameter measured during surgery was significantly smaller, indicating a more stenotic annulus in patients with a bicuspid aortic valve, compared to those with a tricuspid AV. Thus, proper decalcification is necessary during valve replacement in bicuspid AV patients. This study excluded patients who developed bicuspid AV as a result of leaflet fusion after birth. We did not encounter dilatation of the aortic root or enlargement of the sinotubular junction, and there were no cases requiring aortic root reconstruction. Although the implanted valves were generally smaller, the surgical treatment of bicuspid valve disease was the same as for regurgitation or stenosis of a tricuspid valve.
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REFERENCES
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- Edwards JE. Congenital anomalies of or related to the aortic valve. In: Silver M, editor. Cardiovascular pathology. Pathology of aortic incompetence. New York, Tokyo: Churchill Livingstone, 1991:1019–21.
- Roberts WC. The congenitally bicuspid aortic valve. A study of 85 autopsy cases. Am J Cardiol 1970;26:72–83.[Medline]
- Peterson MD, Roach RM, Edwards JE. Types of aortic stenosis in surgically removed valves. Arch Pathol Lab Med 1985;109:829–32.[Medline]
- Subramanian R, Olson LJ, Edwards WD. Surgical pathology of combined aortic stenosis and insufficiency: a study of 213 cases. Mayo Clin Proc 1985;60:247–54.[Medline]
- Angelini A, Ho SY, Anderson RH, Devine WA, Zuberbuhler JR, Becker AE, et al. The morphology of the normal aortic valve as compared with the aortic valve having two leaflets. J Thorac Cardiovasc Surg 1989;98:362–7.[Abstract]
- Edwards JE. The congenital bicuspid aortic valve. Circulation 1961;23:485–8.[Free Full Text]
- Mills P, Leech G, Davies M, Leathan A. The natural history of a non-stenotic bicuspid aortic valve. Br Heart J 1978:40:951–6.[Abstract/Free Full Text]
- Roberts WC. The structure of the aortic valve in clinically isolated aortic stenosis. An autopsy study of 162 patients over 15 years of age. Circulation 1970;42:91–7.[Abstract/Free Full Text]
- Robicsek F. Bicuspid versus tricuspid aortic valves [Editorial]. J Heart Valve Dis 2003:12:52–3.[Medline]
- Lewin MB, Otto CM. The bicuspid aortic valve: adverse outcomes from infancy to old age [Editorial]. Circulation 2005;111:832–4.[Free Full Text]
- Roberts WC, Ko JM. Frequency of unicuspid, bicuspid and tricuspid aortic valves by decade in adults having aortic valve replacement for isolated aortic stenosis Circulation 2005;111:920–5.[Abstract/Free Full Text]
- Casselman FP, Gillinov AM, Cosgrove DM. Intermediate-term durability of bicuspid aortic valve repair for prolapsing leaflet. Eur J Cardiothorac Surg 1999;15:302–8.[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
