Neonatal Central Cyanosis Caused by Anomalous Drainage of the Right Superior Vena Cava

Abstract

The draining of the right superior vena cava (SVC) into the left atrium is a very rare anomaly of systemic vein drainage. This case report describes a term male infant presenting with central cyanosis diagnosed with right SVC drainage into the left atrium. The diagnosis was performed using conventional echocardiography and computed tomography angiography. Surgical correction with translocation of the right SVC to the right atrium was necessary to treat the symptom of cyanosis and prevent further complications, including brain abscesses and paradoxical embolization.

INTRODUCTION

The prevalence of systemic venous anomalies is 0.5% of congenital heart defects. Persistent left superior vena cava (SVC) drainage to the coronary sinus is mostly found among systemic venous anomalies. Anomalous connection of the right SVC with the left atrium is very unusual and has an embryologic origin caused by the leftward and cephalic displacement of the right sinus horn.[1] Clinical diagnosis reveals challenges in the form of subtle manifestations such as mild cyanosis. The diagnosis was performed by echocardiography, cardiac catheterization, computed tomography angiography (CTA), or magnetic resonance imaging (MRI).

CASE REPORT

A 32-day-old, term male infant was transferred from a provincial hospital because of persistent respiratory distress and cyanosis. Desaturation was noted at birth. His SpO₂ was 88% on room air and rose up to 92% with a box with an oxygen flow of 10 L/min. Physical examination demonstrated mild cyanosis and systolic murmur Grade II/VI at the left parasternal border, but the infant was otherwise normal. A chest radiograph showed no cardiomegaly and normal pulmonary vascular marking. The baby was transferred to the Chiang Mai University Hospital for further investigation.

On arrival, an alert male infant without dysmorphic features had a stable appearance in a box with an oxygen flow of 10 L/min. His vital signs were as follows: temperature 37.4°C, heart rate 162/min, respiratory rate 60/min, and SpO₂ 92%. Cardiac examination demonstrated systolic murmur Grade II/VI at the left upper parasternal border, normal S₁/S₂, and regular rhythm. No significant differential cyanosis or differential blood pressure between the upper and lower extremities was observed. A chest radiograph demonstrated no cardiomegaly with a cardiothoracic ratio of 60% and normal pulmonary vascular marking. Echocardiography demonstrated a small atrial septal defect with a left-to-right shunt, no patent ductus arteriosus, and mild left atrial and left ventricular enlargement. Subcostal frontal and sagittal views showed the right SVC draining directly to the left atrium with normal pulmonary venous drainage [Figure 1]. In addition, CTA confirmed the diagnosis of right SVC draining into the left atrium and normal pulmonary venous drainage [Figure 2]. Surgical correction with translocation of the right SVC to the right atrium was performed successfully.

Figure 1.

Color flow Doppler echocardiography in the subcostal view showed anomalous drainage of the right superior vena cava into the left atrium and a small atrial septal defect with a left-to-right shunt. (a) Subcostal frontal view. (b) Subcostal sagittal view. ASD: Atrial septal defect, LA: Left atrium, RA: Right atrium, SVC: Superior vena cava

Figure 2.

Computed tomography angiography in three-dimensional reconstruction demonstrated the right superior vena cava draining into the left atrium. LA: Left atrium, SVC: Superior vena cava

DISCUSSION

Typically, drainage of the systemic vein begins in 5-week-old embryos. It develops from both the cardinal and subcardinal veins, which become the superior and inferior vena cava as well as the coronary sinus to the right atrium.[2] However, the evidence supporting the embryologic mechanism of isolated right SVC drainage into the left atrium is not clear. However, the current theory purposes that the abnormal position of the right horn of the sinus venosus leads to leftward and cephalic displacement, resulting in the opening of the right SVC draining into the left atrium.[3] Previous studies reported that the clinical sign of this anomaly was only mild cyanosis and tachypnea without an audible murmur.[4,5,6] Cyanosis mostly presents as clubbing fingers and dyspnea during adolescence and adulthood. However, the progression to right-sided heart failure does not often occur.[7,8] The essential point of assessment in determining whether cyanotic patients have abnormal venous drainage was to exclude other common diseases, such as lung diseases, cyanotic congenital heart diseases, and arteriovenous malformations. An increasing ability to diagnose congenital cardiac anomalies is notably emerging using advanced, technically noninvasive tools. The diagnosis of an isolated right SVC at the left atrium connection was originally performed by cardiac catheterization and radionuclide angiocardiography. Conventional and contrast echocardiography has been recently used to establish the diagnosis. Cardiac MRI and CTA have emerged as powerful noninvasive tools for the diagnosis and evaluation of other cardiac anomalies, especially pulmonary venous drainage.

The treatment for systemic venous abnormalities is a surgical correction. If left untreated, the most serious subsequent complications are the increasing risk of embolism, which ultimately may cause brain abscess.[9] Moreover, some procedures in patients with anomalous drainage of the right SVC into the left atrium should be mentioned, especially in using the upper extremities’ vein for giving intravenous fluid could be detrimental.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.