Mitral Atresia with Hypoplastic Left Ventricle and Multiple Shunt Lesions.

Mitral atresia is a rare congenital heart defect when compared to atresia of other valves and it is often associated with other cardiac malformation such as patent ductus arteriosus, coarctation of the aorta, transposition of the great arteries, pulmonary stenosis, shunt defects, cor triatriatum, chamber, and valvular anomalies. There have been few reports of mitral atresia, therefore, the case of a 5-month-old male child with complaint of difficulty with breathing and echocardiographic diagnosis of atretic mitral valves, atrial septal defect of 15 mms, ventricular septal defect (VSD) of 10 mms and hypoplastic left ventricle is reported.

INTRODUCTION

Mitral atresia is a rare congenital heart defect. This rarity has been reported when compared to atresia of other valves.[1] Embryologically, this defect has been attributed to a malaligned ventricular and or atrial septum,[2] defect of the atrioventricular canal[3] as well as the excessive growth of the endocardial cushion.[4]

This condition is often associated with other congenital heart defects. These include patent ductus arteriosus, coarctation of the aorta, transposition of the great arteries, pulmonary stenosis, shunt defects, cor triatriatum, chamber, and valvular anomalies. There have been few reports of mitral atresia including that of the first of a set of twin diagnosed with mitral atresia; hypoplastic left ventricle, ventricular septal defect (VSD), D-transposition of the great vessels, severe pulmonary stenosis, and hypoplastic pulmonary arteries at 33 weeks gestation.[5]

Clinical presentation depends on the types and severity of the accompanying anomalies, however, most patients present with respiratory difficulty, cyanosis, failure to thrive, poor peripheral pulses, and congestive cardiac failure. Although cardiac catheterization and cardiac angiography are the mainstay in the evaluation of these patients, ultrasonography remains an effective alternative in the evaluation of the mitral valve especially in resource-poor countries with limited facilities.[6]

Some authors have proposed to classify mitral atresia based on the position of the great vessels, the size of the left ventricle and the presence or absence of a ventricular outflow obstruction.[7] This report describes the presence of this rare anomaly in the presence of a hypoplastic left ventricle, large atrial septal defect (ASD), and VSD in a 5-month-old infant.

CASE REPORT

A 5-month-old male infant was referred to the Emergency Paediatric Unit of our facility from the ENT unit. His complaints were recurrent breathlessness and cough since the first week of life and fever of 4 days before presentation. Breathlessness usually worsened by fever and catarrh, but reduces after treatment. This was associated with a cough and darkened mucous membrane of the oral cavity, lips and the digits; the parents also complained of feeding difficulties, but there was no history of body swelling. He was a product of term gestation, delivered to a 17-year-old primipara; the marriage was nonconsanguineous and the father was 27 years old. On examination, he was in respiratory distress, centrally cyanosed, well hydrated with no pedal edema. He had deranged anthropometry; his weight was 3.8 kg, length was 50 cm while occipito frontal circumference was 38 cm. He was tachycardic with a pulse rate of 176 beats/min, the apex was displaced to fifth left intercostal space lateral to midclavicular line, he had first, second and third heart sounds with a grade three systolic murmur maximal at the left sternal margin. He was tachypnoeic with a respiratory rate of 58 cycles/min. Oxygen saturation was 84% in room air which increased to 90% on oxygen. Abdominal examination revealed a tender hepatomegaly of 4 cm below the right coastal margin. Chest X-ray [Figure 1] revealed cardiomegaly and an elevated apex indicative of right ventricular hypertrophy, and there were prominent vascular markings in both lung fields. Electrocardiography revealed sinus tachycardia with right ventricular hypertrophy; and transthoracic echocardiography was done using SonoScape S8000 with 7.5 MHz probe; studies included M-mode, Doppler, color flow mapping which revealed an atretic mitral valve, large ASD of 15 mm (almost like a common atrium), inlet VSD of 10 mm with right to left shunting and hypoplastic left ventricle [Figure 2]. The great vessels were normally positioned and related [Figure 3]; the aortic arch was left side [Figure 4] and there was no patent ductus arteriosus detected. He was managed with diuretics, vasopressors, antibiotics, and also maintained on oxygen. Parents were counseled. However, his condition further deteriorated, and he died on the third day of admission.

Figure 1

Chest X-ray showing cardiomegaly

Figure 2

Echocardiography showing mitral atresia, atrial septal defect, and ventricular septal defect

Figure 3

Normal relationship of the great arteries

Figure 4

Left sided aortic arch

DISCUSSION

According to the proposed classification of mitral atresia our patient who had a normally positioned great vessels, hypoplastic left ventricle and the absence of a ventricular outflow obstruction fits type I mitral atresia.[7]

The presence of a hypoplastic left ventricle in our patient is similar to the observation in previous reports and had often been referred to as the “hypoplastic left heart syndrome.”[89] This is common and have been reported in about 75% of cases of type I mitral atresia.[7] This is attributable to the underfilling of the ventricle due the absent mitral valve. However, Cabrera et al.[10] had described the presence of a normally sized left ventricle, although their patient had an associated aortic atresia with an intact ventricular septum.[10] This is a frequent finding associated with cases of mitral atresia. The regurgitant flow from the atretic aortic valve maintains the size of the left ventricle. Other less common findings are mitral atresia with an absent left ventricle or single ventricle.

The normally sited and positioned great vessels in our patient was also in keeping with the autopsy cases reviewed by Moreno et al.[7] where up to 52 cases of mitral atresia were also found to have normally related great vessels. They reported transposition of great vessels in 30 subjects.[7] Similarly, they reported ASD and VSD in their series as was observed in our case.[7]

Asplenia[11] and polysplenia[12] have been documented by some authors, however, our patient had a normal spleen.

Our patient presented within the first week of life, and this is in keeping with the natural history of this complex heart disease. Similarly, majority of the cases reviewed by Moreno et al.[7] presented with cyanosis and respiratory difficulty within the first week of life.[7] Although, they observed more severe cyanosis in patients with right ventricular outflow tract obstruction, our patient had severe cyanosis with no observed pulmonary stenosis. In the absence of a pulmonary stenosis, the ensuing pulmonary venous congestion from our patient's large ASD in the presence of a mitral atresia may have contributed to severe pulmonary congestion explaining the cyanosis and heart failure.

Hypertrophy of the right chamber of the heart is usually a common finding because both systemic and pulmonary venous blood is propelled mostly by the right ventricle in the presence of a large ASD. This is because blood flows from the lungs into the left atrium, crosses to the right side of the heart to mix with the systemic venous return and then from the right ventricle into the pulmonary artery and aorta through the VSD.

Prognosis and outcome of this patient may have been improved by the presence of a pulmonary stenosis as this may prevent the pulmonary venous congestion that ensues from the large amount of blood shunted to the right chamber through the large ASD in the presence of a mitral atresia. Furthermore, this will also prevent ensuing pulmonary hypertension.

CONCLUSION

Mitral atresia is a rare disease with poor outcome, and very few cases have been reported in recent times. It could be associated with variable cardiac defects and absence of pulmonary stenosis, surgical intervention portends poor outcome as was witnessed in the index case.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.