Congenital Giant Left Atrium with Severe Mitral Valve Regurgitation

A three-month-old male infant presented to the Royal Hospital, Muscat, Oman in April 2014 following two episodes of pneumonia. On presentation, the patient was not dysmorphic; however, he was tachycardic and tachypnoeic with severe respiratory distress. A pansystolic murmur was heard in his apex, radiating to the axilla. A chest examination showed bilateral wheezing and scattered crepitations. An abdominal examination revealed a soft abdomen with hepatomegaly (liver span of 12 cm), situated 4 cm below the right costal margin.

Echocardiography and an angiographic volume-rendered reconstructed computed tomograph showed a giant left atrium measuring 7.4 × 4.7 cm [Figure 1]. The atrium had severe mitral valve regurgitation from poor coaptation of the mitral valve leaflets due to annulus dilation of 22 mm. The mitral valve apparatus and left atrial appendage were normal, excluding the associated left atrial appendage aneurysm. There was mild tricuspid valve regurgitation with a peak gradient of 90 mmHg (systemic blood pressure: 80/55 mmHg), indicating severe pulmonary hypertension. The left ventricle was moderately dilated—the left ventricular posterior wall dimension in diastole was 4 mm; the interventricular septum dimension in diastole was 4 mm; the left ventricular end diastolic dimension was 40 mm; and the left ventricular end systolic dimension was 18 mm. Normal ventricular systolic function was noted (ejection fraction: 62%). The right ventricle was compressed by the dilated left ventricle, with severe compression of the right atrium secondary to the dilated left atrium. The inferior vena cava and hepatic veins were dilated; however, the superior vena cava was compressed by the dilated left atrium with a mean gradient of 8 mmHg at its midportion. The dilated pulmonary veins drained normally to the left atrium. No intracardiac vegetation or thrombi were seen. These findings were confirmed by cardiac computed tomography (CT) angiography; severe compression of the left main bronchus was also observed [Figure 2]. The CT angiography also revealed a left atrial volume of 84 mL compared to a left ventricular volume of 10 mL. A chest radiograph of the infant revealed a persistent left-sided lung opacity [Figure 3]. Further abdominal ultrasonography and CT findings indicated eventration of the left hemidiaphragm with a raised spleen position corresponding to the opaque shadow seen on the chest radiograph. A diagnosis of a congenital giant left atrium (CGLA) was made.

Figure 1A & B:

A: Four chamber echocardiograph showing a giant congenital left atrium (white arrow) severely compressing the right atrium (red arrow) in a three-month-old male infant. B: Volume-rendered reconstructed computed tomography angiograph showing the giant congenital left atrium (white arrow). Note the size of the left atrium in comparison to the left ventricle (red arrow) and ascending aorta (asterisk).

RV = right ventricle; LV = left ventricle.

Figure 2A & B:

A: Axial computed tomography (CT) angiograph showing a giant congenital left atrium (black arrow) with left upper lobe and segmental right lower lobe atelectasis (red arrows) in a three-month-old male infant. B: Maximum-intensity CT angiograph projection showing splaying of the carina with a horizontal orientation and narrowing of the left main bronchus (asterisk). This was secondary to the mass effect from the enlarged left atrium (black arrow) resulting in left upper lobe and segmental left lower lobe atelectasis (red arrow).

Figure 3:

Frontal chest radiograph of a three-month-old male infant with congenital giant left atrium showing a persistent left-sided lung opacity (arrow). This was determined by ultrasonography and computed tomography to be a raised spleen caused by eventration of the left diaphragm.

Despite cardiac anti-failure medications and inotropic support, a high-risk operation was performed to repair the mitral valve due to the cardiac findings and prolonged intubation. A posterior annuloplasty and a posterior left atrial wall excision were also carried out concurrently. The diagnosis of CGLA was confirmed during the course of the surgery. Following the operation, the left atrial dilation improved and the right ventricular systolic pressure decreased to 30 mmHg (estimated from the tricuspid valve regurgitation jet). Unfortunately, the moderate mitral valve regurgitation continued postoperatively and the infant died two weeks later due to severe cardiorespiratory compromise.

Comment

CGLA is an extremely rare condition with significant morbidity and mortality.1 The exact aetiology remains unknown and only a few cases have been reported in patients under one year of age.2 The congenital aetiology of a giant left atrium includes a young age at presentation, a lack of associated valvular abnormalities and the absence of histological evidence of a specific degenerative disease in the atrial wall. CGLA has been associated with rheumatic heart disease, left ventricular failure, chronic atrial fibrillation and left-to-right shunts.3 It has a wide variety of clinical presentations including arrhythmias, systemic embolisation, congestive heart failure and effects of mechanical compression.2,4

In cases of potential CGLA, a high index of suspicion is required. The condition is usually suspected following radiographical evidence of cardiomegaly or persistent secondary effects of compression in the lung fields.4 Echocardiography is the easiest and least expensive diagnostic modality for CGLA.4 However, cardiac CT and magnetic resonance imaging are valuable in diagnosing CGLA when symptoms of compression occur.5 In the present case, the infant had normal mitral valve apparatus on transthoracic and transoesophageal echocardiography and so the CGLA diagnosis was confirmed intraoperatively. In addition, the left atrial appendage was normal in size with no visible thrombi, excluding the associated left atrial appendage aneurysm. The patient had severe pulmonary hypertension secondary to severe mitral valve regurgitation and left atrial dilation which improved postoperatively. Furthermore, the left main bronchus was severely compressed, which most likely contributed to the elevated pressure in the right side. However, as the patient was in a critical condition, diagnostic cardiac catheterisation was not performed. Due to the risk of life-threatening complications, surgical reduction was indicated.2