Ann Thorac Surg 1996;62:1846-1848
© 1996 The Society of Thoracic Surgeons
Case Report
Nonobstructing Accessory Mitral Valve Tissue and Ventricular Septal Defect
Hiroshi Izumoto, MD,
Kazuaki Ishihara, MD,
Masaaki Ogawa, MD,
Yutaka Fujii, MD,
Kotaro Oyama, MD,
Kohei Kawazoe, MD
Third Department of Surgery and Department of Pediatrics, Iwate Medical University, Morioka, Japan
Accepted for publication June 17, 1996.
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Abstract
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A 4-month-old boy with ventricular septal defect was found to have accessory mitral valve tissue attached to the anterior leaflet of the mitral valve. Operation was successfully performed to excise the accessory mitral tissue in the left ventricular outflow tract and close the ventricular septal defect. Most previously reported cases with accessory mitral valve tissue were associated with left ventricular outflow tract obstruction. This boy had no pressure gradient across the left ventricular outflow tract. The indications for prophylactic excision of nonobstructing accessory mitral valve tissue in a patient with other forms of congenital cardiac disease are discussed.
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Introduction
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Accessory mitral valve tissue is a rare congenital cardiac anomaly. Most of the cases reported in the literature were associated with other cardiac anomalies and left ventricular outflow tract (LVOT) obstruction (LVOTO). We report a case of ventricular septal defect (VSD) and accessory mitral valve tissue with no left ventricular outflow–laortic pressure gradient. This patient underwent successful repair of the ventricular septal defect and prophylactic excision of the accessory mitral valve tissue. In treating patients with congenital cardiac anomalies and nonobstructing accessory mitral valve tissue, prophylactic excision of the accessory tissue may be indicated.
In April 1995, a 4-month-old boy was referred to the Department of Pediatrics, Iwate Medical University, for evaluation of heart murmur. His birth was uncomplicated, and birth weight was 2,990 g at the 39th gestational week. His height at admission was 63.8 cm and he weighed 5,500 g. Blood pressure was 85/50 mm Hg with a pulse rate of 130 beats/min. There was a grade III/VI systolic heart murmur at the left sternal border and a grade II/VI diastolic rumble at the apex. Electrocardiography revealed a normal sinus rhythm with right-axis deviation and left atrial enlargement. Echocardiography revealed accessory mitral valve tissue in the LVOT and a perimembraneous VSD. Patent foramen ovale and moderate mitral insufficiency were also present (Fig 1
). Cardiac catheterization was performed, which revealed no pressure gradient across the LVOT and a pulmonary-to-systemic flow ratio of 3.25.
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Fig 1. . Echocardiogram demonstrating the accessory mitral valve tissue in the left ventricular outflow tract. The arrow indicates the accessory mitral valve tissue.
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In May 1995, he was electively operated on with a diagnosis of perimembraneous VSD, patent foramen ovale, moderate mitral insufficiency, and nonobstructing accessory mitral valve tissue. A median sternotomy was performed, and the patient was cannulated with an ascending aorta and biatrial cannulas and placed on cardiopulmonary bypass. Moderate hypothermia was induced and the ascending aorta was cross-clamped. After cardioplegic arrest, the right atrium was opened. The VSD was of the malalignment conoventricular septal type, 9 x 11 mm in size. Heterograft pericardium was used to close the VSD through the tricuspid valve. The patent foramen ovale was then enlarged so we could examine the mitral valve. The mitral valve appeared competent and had no cleft. The ascending aorta was opened transversely. The aortic valve was competent, and an accessory mitral valve tissue, 1.5 x 2 cm in size, was found to be attached to the ventricular aspect of the anterior mitral leaflet in the LVOT (Fig 2). The accessory mitral tissue possessed no chordal attachments. It was excised at the base of the anterior leaflet, and the enlarged foramen ovale and aortotomy were closed.
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Fig 2. . Photograph of intraoperative findings. The arrow indicates the accessory mitral valve tissue, which is attached to the anterior mitral leaflet with a couple of chordlike tissue segments.
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Postoperatively, the patient's course has been uneventful except for some residual shunt. The degree of mitral valve insufficiency has remained unchanged. He was discharged from the hospital on a regimen of oral diuretics, and is now under the supervision of the referring pediatrician.
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Comment
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Accessory mitral valve tissue is a rare congenital anomaly. Since MacLean and associates [1] reported the first case of this anomaly, there have been 42 such cases reported in the literature to the best of our knowledge. Prior to the advent of two-dimensional echocardiography, preoperative diagnosis of accessory mitral valve tissue was difficult. As the use of two-dimensional echocardiography has become more widespread, there have been more reports focusing on the importance of echocardiographic diagnosis of this anomaly [2–4]. In the present case, two-dimensional echocardiography was essential in making the correct diagnosis. As discussed elsewhere, intraoperative recognition of this anomaly is rarely possible. Therefore, the importance of two-dimensional transthoracic or intraoperative transesophageal echocardiography should be emphasized [4].
Congenital anomalies of the mitral valve are often associated with LVOTO in the literature. Three types of mitral valve anomalies are recognized: (1) abnormal attachments of the anterior leaflet of the mitral valve to the ventricular septum, (2) parachute mitral valve, and (3) accessory mitral valve tissue. Among the 42 reported cases of the accessory mitral valve tissue, LVOTO resulted from the accessory mitral valve tissue in combination with or without discrete-type LVOTO in 40 cases. In the presence of interventricular shunt, the severity of LVOTO caused by accessory mitral valve tissue is often underestimated. In the literature, the pressure gradient across the LVOT in patients with interventricular shunt has been reported to range from 10 to 100 mm Hg. The mean pressure gradient across the LVOT in 9 reported cases with VSD was 39 mm Hg. In the present case, there was no LVOTO as assessed by the cardiac catheterization data. The reason for the absence of the pressure gradient was not clearly defined in this particular case. However, we believe that two anatomic factors were involved. First, the size of the accessory valve was small. Second, the accessory mitral valve was attached to the base of the anterior leaflet with a couple of chordlike tissues but not attached to the chords, papillary muscles, or ventricular septum. The area of attachment of the accessory mitral valve was narrow, thereby producing little parachute effect in terms of LVOTO. However, it should be remembered that the severity of LVOTO is underestimated in patients with interventricular shunt.
The incidence of this anomaly is not yet known and the prognosis of patients with accessory mitral valve tissue is very difficult to determine at present. According to the literature, patient age at presentation ranges from 3 days to 59 years [5, 6]. Garrett and Spray [7] reported the oldest patient (44 years) to undergo operation for accessory mitral valve tissue. That patient had undergone repair of coarctation before operation for LVOTO. It is possible that the accessory mitral valve tissue was not recognized during the first operation for coarctation repair and LVOTO subsequently developed gradually. Left ventricular outflow tract obstruction may progress with age. Our case is the third case of accessory mitral valve tissue without LVOTO. The indications for operation in patients with nonobstructing accessory mitral valve tissue are not discussed in the literature, but we believe that if a patient presents with nonobstructing accessory mitral valve tissue and other congenital cardiac disease, prophylactic excision of the accessory tissue is indicated to prevent subsequent development of LVOTO and possible deterioration or emergence of hemodynamically significant LVOTO.
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Footnotes
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Address reprint requests to Dr Izumoto, Third Department of Surgery, Iwate Medical University, 19-1 Uchimaru, Morioka 020, Japan.
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References
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- MacLean L, Culligan JA, Kane DJ. Subaortic stenosis due to accessory tissue on the mitral valve. J Thorac Cardiovasc Surg 1963;45:382–8.
- Alboliras ET, Tajik AJ, Puga FJ, Ritter DG, Seward JB. Accessory mitral valve tissue in association with discrete subaortic stenosis: a two-dimensional echocardiographic diagnosis. Echocardiography 1985;2:191–5.
- Ascuitto RJ, Ross-Ascuitto NT, Kopf GS, Kleinman CS, Talner NS. Accessory mitral valve tissue causing left ventricular outflow obstruction (two-dimensional echocardiographic diagnosis and surgical approach). Ann Thorac Surg 1986;42:581–4.[Abstract]
- Eiriksson H, Midgley FM, Karr SS, Martin GR. Role of echocardiography in the diagnosis and surgical management of accessory mitral valve tissue causing left ventricular outflow tract obstruction. J Am Soc Echocardiogr 1995;8:105–7.[Medline]
- Mathewson JW, Riemenshneider TA, McGough EC, Condon VR. Left ventricular outflow tract obstruction produced by redundant mitral tissue in a neonate. Clinical, angiographic, and operative findings. Circulation 1976;53:196–9.[Abstract/Free Full Text]
- Baba T, Hashimoto Y, Kobayashi T, Murayama Y. A case of accessory mitral valve documented by two-dimensional and pulsed Doppler echocardiography. Jpn J Int Med 1989;78:597–8.
- Garrett HE, Spray TL. Accessory mitral valve tissue: an increasingly recognized cause of left ventricular outflow tract obstruction. J Cardiovasc Surg 1990;31:225–30.[Medline]
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Abstract
Introduction
