Heart International 2011; volume 6:e6 Accessory mitral valve tissue causing severe left ventricular outflow tract obstruction in a post-Senning patient with transposition of the great arteries Prashanth Panduranga,1 Thomas Eapen,2 Salim Al-Maskari,2 Abdullah Al-Farqani 2 1Department of Adult Congenital Heart Disease, Royal Hospital, Muscat; 2Pediatric Cardiology, Royal Hospital, Muscat, Oman Abstract Accessory mitral valve tissue is a rare con- genital anomaly associated with congenital cardiac defects and is usually detected in the first decade of life. We describe the case of an 18-year old post-Senning asymptomatic patient who was found to have accessory mitral valve tissue on transthoracic echocar- diography producing severe left ventricular outflow tract obstruction. Introduction Accessory mitral valve tissue (AMVT) has an incidence of 1 per 26,000 echocardiograms in adults.1 It is generally found in association with congenital anomalies of the heart or great vessels, such as ventricular septal defect, patent ductus arteriosus, or transposi- Correspondence: Prashanth Panduranga, Department of Cardiology, Royal Hospital, Post Box 1331, Muscat-111, Sultanate of Oman. Tel. +968.92603746 - Fax: +968.24599841. E-mail: prashanthp_69@yahoo.co.in Key words: accessory mitral valve tissue, left ven- tricular outflow tract obstruction Conflict of interest: the authors report no con- flicts of interest. Received for publication: 7 May 2011. Revision received: 9 July 2011. Accepted for publication: 15 July 2011. This work is licensed under a Creative Commons Attribution NonCommercial 3.0 License (CC BY- NC 3.0). ©Copyright P. Panduranga et al., 2011 Licensee PAGEPress, Italy Heart International 2011; 6:e6 doi:10.4081/hi.2011.e6 [page 18] tion of the great arteries (TGA).1-4 Patients with isolated AMVT usually present with symp- toms during the first decade of life depending on the severity of left ventricular outflow tract (LVOT) obstruction.2 Embryologically, AMVT is due to incomplete separation of the mitral valve from the endocardial cushion.1,5 The accessory tissue is usually attached to the ven- tricular aspect of anterior mitral valve leaflet, the chordae of the mitral valve or to an acces- sory papillary muscle.1-3 We describe the case of an 18-year old post-Senning asymptomatic patient who was found to have AMVT on transthoracic echocardiography producing severe LVOT obstruction. Case Report An 18-year old male patient was referred to our clinic for murmur evaluation. The patient was known to suffer from TGA and had under- gone a Senning operation in the UK in 1992 when he was six months old. Since then he had been asymptomatic, in good health with no medical follow up. Cardiovascular examina- tion revealed a harsh 4/6 ejection systolic mur- mur radiating widely over the precordium as well as to the patient's neck and back. ECG demonstrated sinus tachycardia with biven- tricular hypertrophy. The transthoracic echocardiography showed situs solitus, D-TGA with pulmonary vein baffle to right atrium, and the systemic vein baffle to left atrium demonstrating normal flow and no stenosis or leak. The left ventricle was small with an intact interventricular septum bulging into the left ventricle, but with good systolic function. The right ventricle was dilated with moderate right ventricular systolic dysfunction. There was no asymmetric septal hypertrophy or sys- tolic anterior motion of mitral valve or pres- ence of any subaortic membrane. There was a well defined mobile leaflet-like structure measuring 1.3¥0.5 cm, prolapsing in systole into the LVOT (Figure 1A and B, arrowheads). On color Doppler examination, there was [Heart International 2011; 6:e6] severe turbulence in the LVOT (Figure 2A) with LVOT peak gradient of 79 mmHg and a mean gradient of 49 mmHg (Figure 2B). On careful examination, the mobile mass repre- sented an AMVT which was seen to adhere to the ventricular side of the anterior mitral valve leaflet (Figure 1C, arrowheads, Movie 1) and prolapsing into the LVOT during systole. There was no aortic regurgitation. There was grade I left ventricular diastolic dysfunction. There had been no previous history of prolonged fever or hospitalization since his surgery. In view of severe LVOT obstruction, he was advised surgery but he and his family pre- ferred a medical follow up. He is being fol- lowed up on aspirin prophylaxis. Discussion Accessory mitral valve tissue can be asymp- tomatic with presence of a murmur or it can present with mild to severe LVOT obstruction causing exercise intolerance, chest pain, or syncope on exertion, as well as recurrent tran- sient ischemic attack or stroke.1-3 In our case there was severe LVOT obstruction but with no symptoms. AMVT is classified as: Type I (fixed: A = nodular, B = membranous), and type II (mobile: A = pedunculated, B = leaflet-like). Type IIB was further subdivided as rudimenta- ry chordae and developed chordae.2,3 In this patient, AMVT was of type IIB with rudimenta- ry chordae. The mobile type is a parachute-like leaflet floating in the LVOT with or without obstruction and is usually thickened or rarely dysplastic. The fixed type is attached to the interventricular septum by short chordae and may reduce the size of a ventricular septal defect.4 LVOT obstruction may be due to mass effect of the accessory tissue or due to pro- gressive deposition of fibrous tissues within the LVOT, secondary to the turbulent flow lead- ing to fibro-muscular hypertrophy.5 In the majority of cases there is severe LVOT obstruc- tion, with a median LVOT gradient of more than 50 mmHg.2,6 Other types of left ventricu-