Ann Thorac Surg 2009;87:79-82. doi:10.1016/j.athoracsur.2008.09.082
© 2009 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
Mitral Regurgitation Due to Myxomatous Degeneration Combined With Bicuspid Aortic Valve Disease is Often Due to Prolapse of the Anterior Leaflet of the Mitral Valve
Vidyadhar Lad, MD,
Tirone E. David, MD*,
Annette Vegas, MD
Division of Cardiovascular Surgery, Department of Anesthesia of the Peter Munk Cardiac Centre at Toronto General Hospital and University of Toronto, Toronto, Ontario, Canada
Accepted for publication September 30, 2008.
* Address correspondence to Dr David, 200 Elizabeth St, 4N457, Toronto, Ontario, M5G2C4, Canada (Email: tirone.david{at}uhn.on.ca).
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Abstract
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Background: This study examines the clinical, echocardiographic, surgical, and pathologic features of patients who had heart valve operations for combined congenital bicuspid aortic valve and mitral regurgitation due to degenerative disease of the mitral valve.
Methods: A retrospective review of 1595 patients who had procedures for mitral regurgitation due to degenerative disease of the mitral valve and 1820 patients who had procedures for congenital bicuspid aortic valve disclosed 29 patients who had combined diseases.
Results: The most common morphology of the bicuspid aortic valve was type 1 (fused right and left aortic cusps). Mitral regurgitation in 21 of 29 patients was caused by prolapse of the anterior leaflet, which was exceptionally large (mean height, 36.5 ± 6.6 mm). Patients with prolapsed anterior leaflet of the mitral valve were younger (48 ± 13 years vs 58 ± 16 years, p = 0.01) and 95% were men. The bicuspid aortic valve was incompetent in 19 of 21, and the aortic annulus exceeded 30 mm in 20 of 21 patients.
Conclusions: Patients with combined mitral regurgitation due to myxomatous degeneration and bicuspid aortic valve disease who require operations often have a large, prolapsing anterior leaflet of the mitral valve and dilated aortic annulus with aortic insufficiency due to cusp prolapse.
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Introduction
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Congenital bicuspid aortic valve and degenerative diseases of the mitral valve (MV) are common heart valve problems. Premature degenerative changes of the arterial wall of the ascending aorta and aortic root are common in patients with a bicuspid aortic valve [1, 2]. Degenerative changes of the mitral valve in patients with bicuspid aortic valve have also been documented [3, 4]. This study reviews the pathology and pathophysiology of combined congenital bicuspid aortic valve and degenerative disease of the MV in a large cohort of patients who underwent heart valve operations.
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Patients and Methods
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Using the Cardiovascular Surgery database of Peter Munk Cardiac Centre, we reviewed all patients who had operations for degenerative disease of the MV as well for congenital bicuspid aortic valve (BAV) from 1990 to 2006. Our institution Review Ethics Board approved this retrospective study, and patient consent was waived. The preoperative transesophageal echocardiograms and the operative and the surgical pathology reports were reviewed in all patients with combined diseases. The BAV cusp morphology was classified as type 1 when the right and left cusps were fused, type 2 when the right and noncoronary cusps were fused, and type 3 when the left and noncoronary cusps were fused.
Categoric variables were expressed as percentages, and continuous variables as mean ± standard deviation (SD). The t test was used for comparison of ages and leaflet sizes.
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Results
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A total of 1595 patients had first-time MV operations for mitral regurgitation due to degenerative disease of the MV and 1820 patients had intervention for congenital BAV. Amongst these patients were 29 in whom both congenital BAV and degenerative disease of the MV was diagnosed by echocardiography and confirmed at operation. These 29 patients are the subjects of this study. Table 1
summarizes their clinical profile.
The BAV had 3 aortic sinuses in 27 patients and 2 aortic sinuses in 2 patients. The 27 patients with 3 aortic sinuses had the same cusp morphology: the anterior cusp (type 1, fused left and right cusps) was attached to the muscular interventricular septum and contained a raphe, and the posterior cusp was attached to the fibrous components of the left ventricular outflow tract. The 2 patients with 2 aortic sinuses had 2 cusps without a raphe, and both cusps were attached to muscular and fibrous portions of the left ventricular outflow tract. The type of valve dysfunction is compiled in Table 1. The mechanism of aortic insufficiency was cusp prolapse and dilated aortic annulus.
The pathology of the MV was myxomatous degeneration in all patients. No patients presented with other types of degenerative diseases of the MV such as fibroelastic deficiency or dystrophic calcification of the mitral annulus. The mitral regurgitation was due to isolated prolapse of the anterior leaflet in 21 patients (72%), isolated prolapse of the posterior leaflet in 7 (24%), and both leaflets in 1 (3%). The matching aortic valve lesion in these patients is summarized in Table 2.
Patients with prolapsed anterior leaflet of the MV were younger than the remaining patients (48 ± 13 vs 58 ± 16 years, p = 0.01), 20 of 21 were men, and all but 1 patient had exceptionally large and myxomatous anterior leaflet and a grossly normal posterior leaflet height with minimal degenerative changes. The mean height of the prolapsed anterior leaflet as measured by preoperative transesophageal echocardiography was 36.5 ± 6.6 mm (range, 25 to 48 mm). The mean height of the anterior leaflet in the remaining 8 patients was 28.1 ± 5.3 mm (range, 23 to 35 mm). The difference in height was highly significant (p < 0.001) (Fig 1). All but 1 patient with a prolapsed anterior MV leaflet had an aortic annulus exceeding 30 mm as measured during the operation. Only 1 patient with a prolapsed anterior MV leaflet had a normally size anterior leaflet (25 mm) by echocardiogram and aortic annulus (25 mm) at operation. The BAV was stenotic in this patient. In the remaining patients with prolapsed anterior leaflet of the MV, the BAV had aortic insufficiency in 19 (mild in 1, moderate in 7, severe in 11) and aortic stenosis in 1. The BAV had 2 aortic sinuses in 2 patients and 3 in 19. The aortic root was aneurysmal in 7 patients and the ascending aorta in 2. One patient with an ascending aorta aneurysm had only mild aortic insufficiency.
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Fig 1. Offline measurement of the length of the anterior mitral leaflet obtained during end-diastole in the midesophageal 4-chamber view. In this instance, it measured 40 mm (white line).
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Three patients had Marfan syndrome with a normal aortic root size, and the indication for intervention was the severity of mitral regurgitation. The MV had advanced myxomatous disease in 1 patient, but only the posterior leaflet had prolapse. The other 2 patients had prolapse of the anterior leaflet and a fairly normal posterior leaflet. The MV was repaired in all 3 patients, and the aortic root was replaced in 2 patients with aortic homograft and repaired in 1 by aortic valve reimplantation.
Echocardiography (Fig 1) showed dilated mitral annulus in all but 1 patient. The mean diameter was 38.9 ± 8.7 mm (range, 22 to 62 mm).
The MV was repaired in 24 patients and replaced in 5. The BAV was repaired in 10 patients and replaced in 19. In addition, the ascending aorta was replaced in 3 patients and the ascending aorta and aortic root in 7. Repair of the aortic valve consisted of shortening of the prolapsing cusp by plication of the area of the nodule of Arantius and annular reduction by plication of the subcommissural triangles in 8 patients, or aortic valve reimplantation in 2. Three patients also had coronary artery bypass grafting.
There were no operative deaths. One patient who had aortic and mitral valve repair required aortic and mitral valve replacement for recurrent grade 4 regurgitation postoperatively.
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Comment
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BAV is the most common congenital heart anomaly, and most reports indicate an incidence of 1% to 2% in the general population. Movahed and colleagues [5] recently reviewed 24,265 patients who had echocardiograms performed for various clinical reasons and 1742 echocardiograms obtained by screening teenage athletes in Southern California. They found a prevalence of BAV of 0.6% in the large cohort and 0.5% in the smaller one. Congenital BAV is often an isolated defect, but it may coexist with other anomalies such as coarctation of aorta, ventricular septal defect, Turner syndrome, coronary artery anomalies, and premature degeneration of the aortic wall that can cause aortic root and ascending aortic aneurysm and dissection [6–8]. Patients with BAV may also have associated degenerative disease of the MV [3, 4]. In an echocardiographic study of BAV by Schaefer and associates [3], the overall prevalence of myxomatous MV was 4.7% and varied according to the morphology of the aortic cusps: the prevalence was 2.6% in type 1 (fused right and left cusps) and 13% in type 2 (fused right and noncoronary cusps). That study did not mention the severity of mitral regurgitation in patients with myxomatous MV.
Thus, the association of congenital BAV with degenerative MV disease is common, but in our experience it is uncommon to find patients with clinically significant combined disorders. In our series of 1595 patients who underwent operations for MR due to degenerative MV disease, only 29 patients (1.8%) had congenital BAV. During the same interval, our database contained 1820 patients who had operations for BAV disease and 29 (1.6%) had clinically important MR due to degenerative disease of the MV.
Myxomatous degeneration is the most common cause of degenerative disease of the MV. The pathologic spectrum of myxomatous degeneration of the MV varies widely and does not always correlate well with the degree of mitral regurgitation. The degenerative process can be limited to a single segment of the MV and cause severe mitral regurgitation, whereas very advanced myxomatous changes of the entire MV may be associated with only mild mitral regurgitation.
Prolapse of one or more segments of the MV leaflets is the main cause of mitral regurgitation in patients with degenerative MV disease. Isolated prolapse of the posterior leaflet is the most common cause of mitral regurgitation [9]. In a series of 701 consecutive patients with mitral regurgitation due to degenerative MV disease, 359 (51%) had isolated prolapse of the posterior leaflet and only 4 (1%) had BAV disease, 92 (13%) had isolated prolapse of the anterior leaflet and 8 (9%) had BAV, and 250 (35%) had prolapse of both leaflets and only 1 had BAV [9]. Thus, the predominance of isolated prolapse of the anterior leaflet of the MV in our patients with BAV is exceptional. In addition, the prolapsed anterior leaflets were unusually large, with a mean height of 36.5 ± 6.6 mm, which was much larger than in patients with prolapsed posterior leaflet in this series and in other reports [10, 11].
The anterior leaflet of the MV is embryologically related to fibrous tissue that forms the left ventricular outflow tract and the left and noncoronary cusps of the aortic valve [12, 13]. The posterior leaflet of the MV originates from a lateral endocardial cushion that forms within the lumen of the developing left ventricle, whereas the anterior leaflet originates from fusions of the superior and inferior atrioventricular endocardial cushions and the developing aorta as it becomes attached to the developing left ventricle [12, 13].
Because most patients with BAV and prolapsed anterior leaflet of the MV had aortic insufficiency and dilated aortic annulus, it is conceivable that degenerative changes occur preferentially on the anterior leaflet of the MV, intervalvular fibrous body, and aortic cusps attached to the fibrous portion of the left ventricular outflow tract, anatomic structures that are embryologically related. Conversely, it is also conceivable that those structures were larger than normal from birth, were subjected to greater mechanical stress (Laplace's law), and with time they increased in size.
Individuals with BAV can have myxomatous disease of the MV just like other persons, but in a small proportion, the degenerative process that causes dilation of the aortic annulus extends into the intervalvular fibrous body and anterior leaflet of the MV with resulting enlargement of the leaflet and mitral regurgitation due to prolapse, likely as consequence of increased mechanical stress.
A limitation of the study is that the clinical observation that patients with BAV disease and mitral regurgitation due to degenerative disease usually have large and prolapsing anterior leaflet is applicable only in the context of combined diseases that require surgical intervention. We cannot generalize this finding to all patients with BAV and myxomatous mitral valve. A much larger epidemiologic study of patients with BAV and myxomatous degeneration of the mitral valve with or without valve dysfunction would be needed to establish the relationship.
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Abstract
Introduction
