Critical Left Ventricular Outflow Tract Obstruction Due to Accessory Mitral Valve Tissue

Critical Left Ventricular Outflow Tract Obstruction Due to Accessory Mitral Valve Tissue RAFFAELE CALABRO, M.D.,* GIUSEPPE SANTORO, M.D.,* CARL0 PISACANE, M.D.," BERARDO SARUBBI, M.D.," GABRIELLA FARINA, M.D.,t GIUSEPPE PACILEO, M.D.,* and GIUSEPPE CAIANIELLO, M.D.? Departments of *Pediatric Cardiology and ?Surgery, V. Monaldi Hospital, 2" University of Naples, Naples, Italy

Left ventricular outflow tract (LVOT) obstruction due to anomalous tissue tag arising from the mitral valve is a rare congenital cardiac anomaly. It generally becomes symptomatic during the first decade of life as exercise intolerance, chest pain, or syncope at effort. To date, only a few cases of critical systemic obstruction due to isolated mitral valve anomaly in neonates have been reported. We report the case of a neonate who was a few hours old and was referred i n severe clinical condition due to critical left ventricular outflow obstruction resulting from a n anomalous tissue tag of mitral valve origin. (ECHOCARDIOGRAPI-IY, Volume 17, February 2000) congenital heart disease, left ventricular outflow tract obstruction, mitral valve anomaly, echocardiography Left ventricular outflow tract (LVOT) obstruction is a relatively frequent cardiac malformation, accounting for 10% of neonatal cardiac emergencies1 It is most frequently due to aortic valve stenosis, whereas subaortic stenosis is far less common, causing about 20% of all types of LVOT obstruction. This latter anomaly is frequently due to fibrous diaphragm, fibromuscular tunnel, or muscular hypertrophy.2.3 However, anomalous mitral valve insertion or fibrous tissue tags of atrioventricular valve origin are quite rare and infrequently cause symptoms in neonates.*-12We report the case of a neonate who was a few hours old and was

This paper has been supported by the Programma Operativo del Piano CCCN-5 #BOO6 of the Minister0 dell'universita e Ricerca Scientifica (MURST) and the European Community (n".711/1998) Address for correspondence and reprint requests to: Giuseppe Santoro, M.D., Pediatric Cardiology, V. Monaldi Hospital, Via Vito Lembo, 14, 84131 Salerno, Italy. Fax: 39-81-7062355.

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referred to our center because of low cardiac output due to left ventricular obstruction; he needed emergent surgical excision of a fibrous tissue tag arising from the mitral valve.

Case Report

A 1-day-old male infant, born at term by elective cesarean section after an uncomplicated pregnancy, was referred in critical condition to our center. On clinical examination, heart failure and low cardiac output signs were evident, with tachycardia, tachypnea, hepatomegaly, peripheral vasoconstriction, weak peripheral pulses, and systemic acidosis. Gallop rhythm and a systolic ejection murmur were evident. Chest radiography showed cardiomegaly and normal pulmonary vascular markings, whereas no significant electrocardiographic anomaly was recorded. On echocardiography, normal sequential anatomy was imaged, without any significant intracardiac and extracardiac shunt. The left

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B

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Figure 1. Apical A. and subxiphoid B. long-axis views of the left ventricle showing a fibrous tissue tag (arrow) arising from the anterior leaflet of the mitral valve with multiple fibrous stalks and ballooning into the left ventricular outflow tract. This caused a severe subvalvular obstruction, as recorded with color flow Doppler C. A 0 or Ao = aorta, LA = left atrium, LV = left ventricle, RV = right ventricle.

ventricle appeared severely dilated and hypokinetic with severe mitral valve regurgitation. LVOT was occupied by a fibrous tissue tag arising from the anterior leaflet of the mitral valve and ballooning into the LVOT during the systole (Fig. l), resulting in a critical left ventricular obstruction. LVOT Doppler peak pressure gradient was only = 60 mmHg, but a typical pattern of ductdependent systemic blood flow, with right-toleft shunt and reverse flow in aortic arch, was

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recorded. Thus, after a brief period of clinical stabilization with prostaglandin and diuretic therapy, the patient underwent a successful surgical resection of the tissue tag (Fig. 2) and was discharged 2 weeks later.

Discussion Mitral valve anomaly is an uncommon congenital heart disease, although it is increasingly recognized as a cause of LVOT obstruc-

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SUBAORTIC OBSTRUCTION DUE TO M V TISSUE

Figure 2. Accessory fibrous tissue tag surgically resected from the left ventricular outflow tract. Short fibrous stalks anchoring this mass to the anterior mitral leaflet are clearly imaged.

tion.4-13 In neonates, this malformation becomes symptomatic for congestive heart failure when associated with ventricular septa1 defect or other anomalies.gJ1 Conversely, isolated LVOT obstruction due to mitral valve anomaly causes symptoms in only 30% of cases, in the form of exercise intolerance, chest pain, or syncope at effort and generally after the first few months of life. In fact, this anatomic arrangement has infrequently been found to be responsible for low cardiac output in neonates.gJ0 It could be supposed that in our patient the cardiac failure was secondary to both the critical LVOT obstruction and the moderate mitral valve regurgitation. This latter was probably caused by the mitral annular dilatation and the geometric mitral valve distortion secondary t o the Venturi effect due to the protrusion of the fibrous mass into the LVOT during the systole. On clinical grounds, it is quite difficult to distinguish LVOT due to mitral valve anomaly from the aortic valve stenosis, and an accurate delineation of the nature of the obstruction is fundamental in planning the correct management of the patient. In fact, aortic valve stenosis is safely and efficaciously

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treated with percutaneous valvuloplastyl; subvalvular obstruction is not amenable to this approach and requires surgery.3 Echocardiography clearly differentiates this from other types of LVOT of mitral valve origin, such as mitral valve stenosis with excessive valvular tissue, anomalous tissue tags arising from the common valve in the setting of atrioventricular canal defects, infective endocarditis, and others. Echo-Doppler analysis clearly images the shape, size, and insertions of the obstructing tissue within the LVOT,13J4 as well as the site and severity of the stenosis. Thus, particularly in neonates, echocardiography might safely guide corrective surgery on the floppy, cardioplegia-arrested heart.2J5J6 In conclusion, accessory tissue tag of mitral valve origin may be responsible for critical LVOT obstruction in neonatal age and always should be ruled out during a thorough evaluation of critical neonates and infants. As widely accepted, echocardiography might safely guide surgery, avoiding cardiac catheterization, which may be troublesome and risky in this subset of patients.

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