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J Thorac Cardiovasc Surg 2007;134:250-251
© 2007 The American Association for Thoracic Surgery
Brief Communication |
Department of Cardiovascular Surgery, Hospital Clinic Barcelona, University of Barcelona, Barcelona, Spain.
Received for publication November 3, 2006; accepted for publication November 16, 2006. * Address for reprints: Stefano Congiu, MD, Universite degli studi di Parma, Department of Cardiac Surgery, Via Gramsci 14, Parma 43100, Italy. (Email: scongiu{at}tiscali.it).
Double-orifice mitral valve (DOMV) is a rare congenital abnormality. Isolated occurrences of this defect are uncommon, and they are usually associated with other congenital heart defects.
A 64-year-old woman was found to have a heart murmur suggestive of mitral regurgitation during a routine clinical examination. The patient had a past history of arterial hypertension. She complained of gradually progressive dyspnea for 6 months before admission.
Transesophageal echocardiography showed dilatation of the left and right atria and ventricles, severe mitral regurgitation, moderate tricuspid regurgitation, a large aneurysm of the interatrial septum, and severe pulmonary hypertension. The mitral valve was divided in two by the presence of a middle structure, which created a functional double-orifice valve (Figure 1).
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Cardiopulmonary bypass was instituted through a standard median sternotomy and arterial and bicaval cannulation. The left atrial cavity was approached through the right atriotomy and septal defect. A large septal aneurysm in the area of the fossa ovalis was found and resected. The anterior and posterior mitral leaflets were thickened. From the operator’s viewpoint, the larger orifice was right, and the smaller was left. They were separated by a tissue bridge connecting the A2 and P2 segments of the valve, which created a double-orifice valve with an anterior and a posterior opening. It was noted that the connecting tissue bridge was also supported by its own chordae tendineae, as if the valve actually had a trileaflet structure (Figure 2). The middle bridge was thickened, and it prolapsed severely into the left ventricle. The anterior leaflet chordae and the most lateral chordae of the posterior leaflets attached to a normally appearing anterior papillary muscle. The chordae of the tissue bridge and some of the posterior leaflet attached to several small muscular outpouchings of the posterior wall of the left ventricle.
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DOMV is a rare abnormality, with the first case described in a postmortem study in 1876.1
DOMV is a consequence of an abnormal development of the endocardial cushions. A morphogenetic mechanism of this type of DOMV is explained by an abnormal union into a single structure between the dorsal endocardial and the left lateral endocardial cushions during an early developmental stage.2 The most accepted classification was described by Trowitzsch and colleagues in 1985,3 which defines 3 different types: the hole type (2 structured orifices with their own subvalvular apparatus [SA]), complete bridging (1 orifice divided by a complete bridge with a shared SA, the most common), and incomplete bridging (1 orifice divided by an incomplete bridge with shared SA).
DOMV is usually detected at an early age because it is associated with other cardiac abnormalities. The most frequent is atrioventricular canal, which is very common in the case of posteromedial accessory orifice.
At the time of diagnosis, functional valve dysfunction is commonly absent, and most of the patients are asymptomatic.
DOMV is frequently associated with abnormalities of the SA. These malformations might involve the chordae tendineae (redundant, abnormal attachment, chordal ring, and parachute type) and the papillary muscles (supranumerary, fused and abnormal attachment).
Transesophageal echocardiography is the key diagnostic tool providing the most detailed information about cardiac anatomy, the best view of the structure, and valve anatomy.
Three strategies have been described in the correction of DOMV: major valve repair, cleft suture, and valve replacement.4 The tissue bridge is responsible for keeping the valve competent, and therefore in case of valve repair, the bridging leaflet should not be divided.4 However, in the case of extensive or complicated mitral defects, valve replacement is the preferred technique.
The development of postoperative heart block in this patient was unexpected, because the abundant native valve annular tissue helped in placing the sutures far from the predicted location of the conduction tissue. As has been discussed previously, DOMV is a consequence of an abnormal development of the endocardial cushions, and abnormal conduction abnormalities have been well described in several congenital endocardial cushion defect diseases.5 This case suggests that some patients with DOMV might have an abnormal location of the conduction bundles, which could lead to perioperative conduction complications.
Supplementary data
Supplementary data associated with this article can be found, in the online version, at doi: 10.1016/j.jtcvs.2006.11.074.
References
Related Article
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  D. Zhu, A. Chen, and Q. Zhao Surgical repair for isolated congenital double-orifice mitral valve Eur J Cardiothorac Surg, February 1, 2011; 39(2): 268 - 270. [Abstract] [Full Text] [PDF]
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