LA drainage of a right superior vena cava (RSVC) is an exceedingly rare congenital heart defect. When present as an isolated defect, this defect typically results in mild cyanosis due to desaturated systemic venous blood from the upper body mixing with fully saturated pulmonary venous blood in the LA.¹ Drainage of upper-extremity venous blood returning to the LA in this patient was confirmed by agitated saline contract injection into a right upper-extremity vein, which demonstrated immediate opacification of the LA and LV (with some crossing over into the right heart via the small atrial shunt). Findings on computed tomography angiogram (CTA) confirmed the etiology of this abnormal drainage to be an RSVC draining exclusively to the LA with no connection to the RA (Image 1). The right middle and right upper pulmonary vein were demonstrated to drain into the rightward and posterior aspect of the RSVC (partial anomalous pulmonary venous return). The right lower and all left-sided pulmonary veins drained normally to the LA. A small secundum atrial septal defect was noted to be remote from the cavoatrial connection with an atrial septum that was malpositioned rightward. The branch pulmonary arteries appeared mildly hypoplastic. She was discharged home on room air with goal SpO₂ levels of ≥85%.

Image 1

(Panel A) Oblique anterior view. (Panel B) Oblique posterior view. The PAs are removed to clarify the RPV anatomy. Separate branches of the RUPV and a branch of the right middle vein connect to the SVC.
Ao = aorta; Azy = azygous vein; IV = innominate vein; LA = left atrium; LPA = left pulmonary vein; LV = left ventricle; PA = pulmonary artery; RA = right atrium; RV = right ventricle; RPV = right pulmonary vein; RUPV = right upper pulmonary vein; SVC = superior vena cava.

Monthly routine outpatient pediatric cardiology follow-up evaluations demonstrated SpO₂ levels in the range of 85-88% and good somatic growth. She was free of symptoms and required no medications. Elective surgical repair occurred via median sternotomy at 6 months of life with autologous pericardial patch baffling of the right middle and upper pulmonary veins into the LA. The atrial septum was incised through the limbus and across the superior aspect of the fossa ovalis, incorporating this communication into a newly created atrial communication with a second patch of autologous pericardium used to augment the superior vena cava (SVC) to the RA junction. The atrial shunt was closed as part of the baffle. A transesophageal echocardiogram (TEE) had negative findings of intracardiac shunting; the baffles were unobstructed and the biventricular function was normal. Of note, while sewing this baffle patch, the surgeon noted significant distention of the innominate vein and upper SVC, intermittently requiring release of the SVC snare to allow it to decompress.

An unexpected amount of hemodynamic instability was encountered in the cardiac ICU postoperatively. She required support with mechanical ventilation and infusions of norepinephrine, epinephrine, and vasopressin; she had a greater-than-anticipated diuretic need. The intraoperative observation of robust SVC return along with review of the preoperative CTA findings of dilated brachiocephalic arteries and TTE findings of moderate dilatation of the LV and diastolic flow reversal across the aortic arch (Image 2) led to clinical concern for a vein of Galen malformation (VOGM). A congenital arteriovenous malformation (AVM) in the brain was confirmed by a CTA, and she was taken to the interventional radiology suite for the first of several planned serial coil embolization procedures of the VOGM. Vasoactive infusions were weaned, and she was extubated the next day. The subsequent hospital course was unremarkable. She was discharged on PO feeds and enteral diuretics 12 days following cardiac surgery. A second coil embolization 6 weeks later allowed for a wean in diuretics. An additional coil embolization was planned, contingent on the results of a routine follow-up brain magnetic resonance imaging.

Image 2

LA drainage of the RSVC is often not diagnosed until later in life when affected patients present with systemic emboli, stroke, and brain abscess, among other complications. Visible cyanosis from this lesion, particularly in the neonate, is uncommon.^1,2 In this case, universal screening for CCHD led to the detection of a noncritical congenital heart defect. A CTA is an essential part of the workup for such an anomaly of the systemic venous system and, in this case, confirmed partial anomalous drainage of two right-sided pulmonary veins. An anomalously draining RSVC to the LA is thought to have embryologic origins similar to that of a superior sinus venous defect with a deficiency is present in the common wall between the posterior RSVC and a portion of the anterior right-sided pulmonary veins. Preferential blood flow from the RSVC into the LA in utero leads to diminished flow to the RA and atresia of the RSVC orifice to the RA.²

VOGM is an AVM in the brain that typically causes high-output heart failure (HF) as oxygenated systemic blood flow shunts from the aorta to the brain and directly into a systemic vein, which then returns blood to the heart and lungs. This extracardiac shunt increases the cardiac demand to sustain systemic needs for oxygenated blood and results in congestive HF and pulmonary hypertension (PH) due to excessive return of blood to the right heart and lungs.³ Sinus venous defects and coarctation of the aorta are the most common forms of congenital heart disease (CHD) to be reported with a VOGM. RSVC drainage to the LA and a VOGM has also been previously reported. Other patients found to have this association of VOGM and RSVC to the LA were similarly well in the preoperative period.^3,4 This finding is in notable contrast to neonates with a VOGM and normal systemic venous anatomy, who may be critically ill. This patient was free of symptoms and growing well until elective repair of the RSVC to LA occurred at 6 months of age. It has been theorized that right-to-left shunting of systemic venous return to the systemic circulation provides some degree of a balance to the steal of blood from the aorta into the VOGM. The increased venous return entering the left heart and not the RA, RV, and pulmonary vascular bed may explain the absence of congestive HF and PH.³

This patient's postoperative diagnosis of a VOGM is an important reminder to maintain a high index of suspicion for potential noncardiac anomalies when taking care of patients with CHD. The significant innominate vein distension noted intraoperatively was the first clinical finding to be recognized that would suggest excessive systemic venous return from the brain, as is seen with a VOGM. This operative finding, along with her unexpected postoperative instability and Doppler evidence of systemic steal by TTE, led to a prompt evaluation for and diagnosis of this important noncardiac vascular abnormality.

References

1. Deraz S, Alzaabi O, Ummerkhan A, Hakeem SA, Elnady H, Al Kamali A. Partial anomalous systemic venous drainage, right superior vena cava to the left atrium in nonisomeric patient. Ann Pediatr Cardiol. 2023;16(6):468-471. doi:10.4103/apc.apc_93_23
2. Van Praagh S, Geva T, Lock JE, Nido PJ, Vance MS, Van Praagh R. Biatrial or left atrial drainage of the right superior vena cava: anatomic, morphogenetic, and surgical considerations--report of three new cases and literature review. Pediatr Cardiol. 2003;24(4):350-363. doi:10.1007/s00246-002-0329-7
3. Hoda M, Lemler M, Cory M. Vein of Galen aneurysmal malformation with anomalous right superior vena cava to the left atrium leading to atypical clinical and echocardiographic findings. Pediatr Cardiol. 2023;44(1):254-259. doi:10.1007/s00246-022-03057-x
4. Elmahrouk AF, Helal A, Ismail MF, et al. Isolated right superior vena cava draining into the left atrium in a child with vein of Galen aneurysmal malformation-case report. J Cardiothorac Surg. 2018;13(1):66. Published 2018 Jun 13. doi:10.1186/s13019-018-0758-x