Extracorporeal membrane oxygenation as a bridge to diagnosis in a 20-month old girl with pulmonary hypertension and right ventricular failure

Abstract

A 20-month old girl with severe pulmonary hypertension and cardiomegaly was admitted to the paediatric intensive care unit with right ventricular failure of unknown origin. Only after decompression of the heart chambers under extracorporeal membrane oxygenation (ECMO), did the pathognomonic membrane of Cor triatriatum become visible on echocardiography. The patient underwent successful surgical correction and subsequently cardiac function recovered completely. Cor triatriatum remains a rare congenital cardiac disorder with a variable presentation, often including recurrent respiratory infections before right-sided heart failure occurs. This case illustrates that ECMO can serve not only as a bridge to diagnosis, but can also facilitate correct diagnosis. Given the excellent outcome after surgical treatment, it is crucial that cardiologists rule out the possibility of cor triatriatum when assessing a child with unexplained pulmonary hypertension.

CASE SUMMARY

A 20-month old girl with pulmonary hypertension and cardiomegaly was admitted to our paediatric intensive care unit (PICU). At the age of 17 months, she had presented with fever and increased effort in breathing. The chest X-ray at that time showed a normal-sized heart and increased perihilar markings. Serology was positive for Mycoplasma, and atypical pneumonia was diagnosed. Despite treatment with clarithromycin, the symptoms persisted. She was hospitalized at the age of 20 months with hypoxia, and required supplemental oxygen treatment. A repeat chest X-ray revealed cardiomegaly and prominent central pulmonary vascularity.

On echocardiography, the right ventricle was massively dilated with a pressure gradient of 55 mmHg across the tricuspid valve (Fig. 1). Both left atrium and ventricle were compressed by the bulging septa, but the morphology appeared to be otherwise normal. All four pulmonary veins could be seen with normal insertion into the left atrium and unobstructed flow. The girl was electively intubated and a computed tomogram of the chest was obtained, which showed diffuse areas of ground-glass opacification and interlobular septal thickening. Cardiac angiography confirmed suprasystemic pulmonary pressures of 75/41 (52) mmHg [aortic pressure 73/39, (48) mmHg] with severely dilated right atrium and ventricle. The pulmonary artery wedge pressure was 36 mmHg, while the left ventricular end-diastolic pressure was 12 mmHg. Treatment with 100% oxygen and inhaled nitric oxide did not significantly reduce pulmonary artery pressures. Selective pulmonary artery wedge angiogram confirmed unobstructed drainage of the main pulmonary veins.

Figure 1:

Echocardiographic image (apical 4-chamber view) showing findings at presentation. The right atrium and ventricle are severely dilated compressing the left ventricle. LA: left atrium; LV: left ventricle; MV: mitral valve; RA: right atrium; RV: right ventricle.

During the catheter study, the girl became progressively unstable with systemic arterial hypotension, and signs of pulmonary oedema. Owing to the rapid deterioration, the procedure was abandoned and the patient brought to the PICU with the diagnosis of acute right ventricular failure due to severe pulmonary hypertension. Pulmonary veno-occlusive disease was suspected, potentially triggered by the Mycoplasma infection.

Despite high-frequency oscillatory ventilation, inhaled nitric oxide, prostacyclin infusion and inotropic support, arterial hypotension and lactic acidosis worsened. Given the previously good condition of the child, the lack of a definitive diagnosis and the possibility of a potentially reversible cause it was decided to offer extracorporeal membrane oxygenation (ECMO). Venoarterial ECMO was provided via neck cannulation, and normal gas exchange and perfusion pressures were established rapidly. The repeat echocardiography on ECMO showed some right atrial and ventricular decompression resulting in increased left atrial and ventricular dimensions, revealing a demarcated supra-mitral membrane in the left atrium (Fig. 2). The diagnosis of cor triatriatum was made and the patient was transferred to the cardiac theatre. The membrane was excised on cardiopulmonary bypass via the transseptal approach through the right atrium. She returned to PICU of ECMO on a milrinone infusion and inhaled nitric oxide with pulmonary artery pressures two-thirds systemic. Treatment with enteral sildenafil and intravenous prostacyclin was started and the patient could be weaned from inhaled nitric. She was extubated on Day 5, prostacyclin was ceased on Day 10 and the patient was discharged to the ward on Day 11. The right ventricular function gradually improved and the pulmonary artery pressures normalized. Postoperatively, we noted a mild left hemiplegia that was attributed to an ischaemic lesion in the right parietal cortex evident on brain magnetic resonance imaging. She was discharged home after 32 days. Cardiac and neurological follow-ups at 2 years of age were normal.

Figure 2:

Echocardiographic image (modified 4-chamber view) showing findings under ECMO. A membrane is visible in the left atrium (arrow), obstructing flow between the pulmonary veins/left atrium and the mitral valve. LA: left atrium; LV: left ventricle; MV: mitral valve; RA: right atrium; RV: right ventricle.

DISCUSSION

Cor triatriatum is a rare congenital cardiac defect wherein the left atrium is partially divided by a thin membrane, which usually leads to obstruction of pulmonary venous return. Successful treatment of cor triatriatum was reported for the first time by Belcher et al. [1]. A recent case series on 28 patients reported median age at presentation of 6 months (range: 0.6–240) and the malformation accounts for ∼0.1% of all congenital cardiac defects [2]. Presenting symptoms were increased effort in breathing, exertional dyspnoea, failure to thrive and poor feeding in the majority of cases, shock in four and respiratory arrest in two patients. Two of 28 patients died, both with associated complex congenital heart malformations. Other series have reported excellent surgical and long-term outcome.

Diagnosis of cor triatriatum can usually be rapidly established using transthoracic echocardiography showing a dilated left atrium and a membrane above the mitral valve obstructing mitral valve inflow. However, in the present case, the compressed left atrium and ventricle interfered with correct diagnosis. Decompression of the heart chambers under ECMO allowed visualization of the pathognomonic membrane on echocardiography. This case illustrates the point that ECMO can serve not only as a bridge to diagnosis, but can also facilitate correct diagnosis [3]. In the present case, without ECMO, the patient most likely would have died with an unrecognized underlying disorder that is amendable to surgical treatment with a very good prognosis.

In summary, cor triatriatum remains a rare congenital cardiac disorder with a variable presentation, often including recurrent respiratory infections before right-sided heart failure occurs. Given the excellent outcome after surgical treatment, it is crucial that cardiologists rule out the possibility of cor triatriatum when assessing a child with unexplained pulmonary hypertension.

Conflict of interest: none declared.