Teaching Case

A 3-year-old girl presented 8 days after birth with a cardiac murmur on auscultation and low oxygen saturation (88-94%) as an incidental finding. An interventricular shunt was suspected, but not conclusively diagnosed. As this cardiac murmur and low oxygen saturation persisted during follow-up during the following 3 months, she was referred to a pediatric cardiologist. An echocardiography was performed and showed no abnormalities.  Due to the low oxygen saturation, she was referred to a pneumologist for further investigation.

A computed tomography (100kV, 30mAs) with intravenous contrast (25ml, Iomeron 400) was performed and showed a double superior vena cava with a left superior vena cava draining into the left atrium and a right superior vena cava draining into the right atrium. Bridging of the bilateral superior vena cava through a small left innominate vein (Fig 1A-B).

Persistent left superior vena cava (PLSVC) is one of the most common congenital venous malformations in the thorax. It is caused by a persistent left anterior cardinal vein which normally regresses and becomes the ligament of Marshall (1, 2). It affects 0.3% - 0,5% of patients with a normal heart and 4,5% - 12% of patients with congenital heart abnormalities (e.g. atrial and ventricular septal defect, aortic coarctation, transposition of the great vessels, Tetralogy of Fallot) (3).

PLSVC has several anatomic variations with different clinical consequences. In 90% the PLSVC drains into the right atrium through a dilated coronary sinus (2, 4). In 10-20% a PLSVC drains into the left atrium or through an unroofed coronary sinus causing a right-to-left shunt with systemic hypoxemia (5, 8). The right superior vena cava can be normal, small or absent and in 30% there is a bridging innominate vein (5, 6). In 50% they’re associated with other cardiac anomalies (7).

PLSVC is often detected during catheterization as an incidental finding, but appropriate investigation is necessary to characterize the venous anatomy and to look for coexisting cardiological anomalies. The possible imaging modalities are conventional contrast venography, transthoracic echocardiography (TTE), MRI and CT. On TTE, a dilated coronary sinus will be seen which can be confirmed by use of intravenous saline contrast echocardiography (bubble study) (5, 8, 9).

A PLSVC has several clinical and practical implications.  Catheterization or placement of pacemaker/ICD can be difficult with possible injury. For cardiothoracic surgery, a PLSVC is of clinical importance when cannulating the heart for cardiopulmonary bypass. A right to left shunt increases the risk of brain abscess, cerebral infarction or paradoxical thrombo-embolism when drugs are administered intravenously (1, 5, 7, 8).  

There are several surgical procedures to correct this anomaly have been reported. Ligation of the left SVC, intra-atrial redirection of flow from the left SVC to the right atrium, and reimplantation of the left SVC into the right atrium, pulmonary artery or SVC (1, 5, 7, 8).  

In our case, the patient was treated by transcatheter occlusion. An introducer sheath was placed into the left internal jugular vein and a vascular occlusive device (Amplatzer Vascular Plug 2, Abbott Vascular Division, Diegem, Belgium) was inserted in the embolization site (Fig.2 – 4). After 5 minutes there was a complete occlusion of the left vena cava with immediate normalization of the oxygen saturation.

In conclusion, a persistent left superior vena cava has several anatomic variations with or without hemodynamical changes. In case of chronic hypoxia, without cardiac anomaly, a full investigation is mandatory to search for extra-cardiac right-to-left shunts and also to verify the anatomy as they have different clinical and/or practical implications with different management. CT and MRI are well adapted to this type of investigation.

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