Ann Thorac Surg 2004;77:713-715
© 2004 The Society of Thoracic Surgeons
Case report
Accessory mitral valve tissue causing severe left ventricular outflow tract obstruction in an adult
Yoshikazu Aoka, MDa*,
Naoko Ishizuka, MD, PhDa,
Yasunari Sakomura, MD, PhDa,
Hirotaka Nagashima, MD, PhDa,
Masatoshi Kawana, MD, PhDa,
Akihiko Kawai, MD, PhDb,
Hiroshi Kasanuki, MD, PhDa
a Department of Cardiology, The Heart Institute of Japan, Tokyo Women's Medical University, Tokyo, Japan
b Department of Cardiovascular Surgery, The Heart Institute of Japan, Tokyo Women's Medical University, Tokyo, Japan
Accepted for publication April 9, 2003.
* Address reprint requests to Dr Aoka, 8-1 Kawada-cho Shinjuku-ku, Tokyo 162-8666, Japan
e-mail: maoka{at}hij.twmu.ac.jp
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Abstract
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Accessory mitral valve (AMV) is a rare cause of left ventricular outflow tract (LVOT) obstruction and is extremely rare in adults. We report a case of an older adult with an AMV that caused severe LVOT obstruction. A parachute-like piece of tissue (the AMV) protruding into the LVOT during systole was first detected in a 45-year-old woman by echocardiography. Because the pressure gradient and dyspnea gradually progressed, she finally underwent a successful operation for removal when she was 48 years old.
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Introduction
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Accessory mitral valve (AMV) is a rare cause of left ventricular outflow tract (LVOT) obstruction in childhood and is extremely rare in adults. MacLean and associates [1] first described this rare condition in 1963. At least 63 cases of AMV have been reported in the literature. Of these, 59 patients underwent operations, and only 7 were adults [2]. In most reported cases, this anomaly was found in the first decade of life, mainly because of a heart murmur [3]. We report a case of AMV in an adult patient that caused severe LVOT obstruction and was found in the 40 s. The AMV was removed in a successful operation after 3 years of medical follow-up.
A heart murmur was first detected in a healthy 38-year-old woman at an annual checkup. Because she had no symptoms, she did not undergo further examination and a diagnosis was not made at that time. When she was 45 years old, she began to experience chest tightness on exertion and was referred to the Tokyo Women's Medical University Hospital.
A harsh, systolic ejection murmur was audible in the aortic valve area (grade 3/6), and it radiated to the neck. The upslope of the carotid pulse was sluggish, and her blood pressure was 140/80 mm Hg. The electrocardiogram (ECG) showed typical left ventricular hypertrophy (high voltages with an ST-T strain pattern). Transthoracic echocardiography (TTE) revealed marked concentric, left ventricular hypertrophy and a parachute-like piece of abnormal tissue protruding into the LVOT during systole. Color Doppler revealed a mosaic flow pattern, which meant that there was a mechanical obstruction in the LVOT. The peak pressure gradient (PG) across the LVOT, estimated by Doppler measurement of peak flow velocity, was about 80 to 100 mm Hg.
To obtain more detailed information, transesophageal echocardiography (TEE) was performed (Fig 1A, 1B).
This revealed that the abnormal tissue was not part of the mitral valve and that no other cardiac anomalies were present. The abnormal tissue was diagnosed as an AMV. Surgical removal was recommended, but the patient refused to undergo an operation. An infusion of disopyramide reduced the mean PG across the LVOT from 60 to 40 mm Hg. She was placed on oral disopyramide and followed.
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Fig 1. Transesophageal echocardiographic (TEE) findings of an accessory mitral valve (AMV). (A, B) Preoperative TEE: (A) The arrow indicates AMV tissue protruding into the left ventricular outflow tract (LVOT). Note the marked concentric left ventricle (LV) hypertrophy. (AO = aorta; LA = left atrium.) (B) The mosaic flow pattern shows a pressure gradient across the LVOT produced by the AMV. (C, D) Postoperative TEE: (C) The abnormal tissue has been completely removed, (D) and no abnormal flow is seen in the LVOT.
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The patient remained well until chest tightness on exertion began to occur 3 years after cardiac catheterization was performed. Echocardiography revealed that the maximum pressure gradient across the LVOT was more than 140 mm Hg, even though she was still taking disopyramide. She then decided to undergo surgical repair.
A median sternotomy was followed by an aortotomy, and the AMV was observed beneath the noncoronary cusp. It had three separate chordae that were all connected to the posteromedial papillary muscle. Part of the AMV was also attached to the noncoronary cusp as well as the ventricular septum below the noncoronary cusp and the aorto-mitral continuity. Because the AMV did not contribute to mitral valve function, it was excised completely without any destruction of the valve.
The patient had a smooth recovery after the operation. Her heart murmur disappeared, and the up-sloping pattern of pulsation returned to normal. TEE showed neither a mosaic flow pattern in the LVOT nor mitral regurgitation (Fig 1C, 1D). The histopathologic examination revealed that this accessory valve was composed of fibrous tissue. She has been healthy and without symptoms for 2 years since the operation.
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Comment
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Most reported cases of AMV have been associated with other congenital cardiac malformations, but this case was not associated with any malformation. Isolated AMV, such as that seen in our patient, is rare. This may be one reason why AMV was not found until the 40 s in the present case. If there had been associated cardiac malformations, a detailed examination would have been performed because of the concomitant heart murmur or symptoms, and the AMV might have been found earlier.
According to the literature, the youngest patient with AMV was diagnosed immediately after birth, and the oldest was diagnosed at 77 years. The mean age at diagnosis is around 6.5 years, according to a previous review [4]. In our patient, although the AMV had been present since birth and regular annual medical check-ups had been performed, no heart murmur was noticed until she was 38 years old. This means that there was no pressure gradient in the LVOT before that age, which might be another reason why she had no symptoms throughout early life.
As mentioned before, a harsh murmur is audible from birth in most cases of AMV, which allows a diagnosis in childhood. Possible reasons why the PG in the LVOT was not present until the 40 s but appeared after that time, are:
- The AMV did not protrude into the LVOT during childhood, but the chordae gradually became longer and finally the valve tissue protruded into the LVOT, which resulted in a harsh systolic heart murmur and symptoms.
- The abrupt snapping of a chorda may have caused a change in the shape of the AMV, resulting in protrusion of tissue into the LVOT and rapid progression of the heart murmur and symptoms in adulthood. In fact, the excised AMV had several chordae that seemed to have been stretched or snapped before its removal (Fig 2A–2C).
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Fig 2. Intraoperative findings and excised accessory mitral valve. (A) Extra chordae originating from the accessory mitral valve are seen between the tips of the forceps (right side). The operator is picking up the accessory valve using forceps with the left hand toward the left side of this photo. (B) Reproduction of the condition in which the accessory mitral valve protrudes into the left ventricular outflow tract by filling with water from the left ventricle. A parachute-like structure can be seen just below the aortic valve. (C) The white, membranous, and parachute-like accessory mitral valve after resection.
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There have been few reports concerning the progression of the PG in patients with AMV. Although one case of AMV with a progressive PG across the LVOT was reported, this patient was a newborn infant [5]. In another case, the PG across the LVOT was reported to increase by 65 mm Hg over a 5-year period [6]. However, the incidence and natural history of this anomaly is not fully known yet.
Even though AMV is extremely rare in adults, this uncommon congenital abnormality should be kept in mind as part of the differential diagnosis of LVOT obstruction, because there might be cases where the obstruction becomes prominent over time. Early surgical removal is recommended for an AMV that causes LVOT obstruction, because the PG might increase with aging, as happened in the case presented here.
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References
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- MacLean L., Culligan J., Kane D. Subaortic stenosis due to accessory tissue on the mitral valve. J Thorac Cardiovasc Surg 1963;45:382-387.
- Prifti E., Frati G., Bonacchi M., Vanini V., Chauvaud S. Accessory mitral valve tissue causing left ventricular outflow tract obstruction: case reports and literature review. J Heart Valve Dis 2001;10:774-778.[Medline]
- Ow E.P., DeLeon S.Y., Freeman J.E., et al. Recognition and management of accessory mitral tissue causing severe subaortic stenosis. Ann Thorac Surg 1994;57:952-955.[Abstract]
- Meyer-Hetling K., Alexi-Meskishvili V.V., Dahnert I. Critical subaortic stenosis in a newborn caused by accessory mitral valve tissue. Ann Thorac Surg 2000;69:1934-1937.[Abstract/Free Full Text]
- Inigo A.C., Santos de Soto J., Descalzo Senorans A., Lillo Jimenez T., Grueso Montero J., Gil-Fournier C. Progressive subaortic stenosis caused by accessory mitral valve tissue. Rev Esp Cardiol 1999;52:438-440.[Medline]
- Hatem J., Sade R.M., Taylor A., Usher B.W., Upshur J.K. Supernumentary mitral valve producing subaortic stenosis. Chest 1981;79:483-486.[Abstract/Free Full Text]
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Abstract
Introduction
