23 Superior Vena Cava Syndrome

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Superior Vena Cava Syndrome 

Francesco Puma and Jacopo Vannucci 

University of Perugia Medical School,  

Thoracic Surgery Unit, 


1. Introduction 

1.1 Anatomy 

The superior vena cava (SVC) originates in the chest, behind the first right sternocostal 

articulation, from the confluence of two main collector vessels: the right and left 

brachiocephalic veins which receive the ipsilateral internal jugular and subclavian veins. It 

is located in the anterior mediastinum, on the right side. 

The internal jugular vein collects the blood from head and deep sections of the neck while 

the subclavian vein, from the superior limbs, superior chest and superficial head and 


Several other veins from the cervical region, chest wall and mediastinum are directly 

received by the brachiocephalic veins.  

After the brachiocephalic convergence, the SVC follows the right lateral margin of the 

sternum in an inferoposterior direction. It displays a mild internal concavity due to the 

adjacent ascending aorta. Finally, it enters the pericardium superiorly and flows into the 

right atrium; no valve divides the SVC from right atrium. 

The SVC’s length ranges from 6 to 8 cm. Its diameter is usually 20-22 mm. The total 

diameters of both brachiocephalic veins are wider than the SVC’s caliber. The blood 

pressure ranges from -5 to 5 mmHg and the flow is discontinuous depending on the heart 

pulse cycle. 

The SVC can be classified anatomically in two sections: extrapericardial and intrapericardial. 

The extrapericardial segment is contiguous to the sternum, ribs, right lobe of the thymus, 

connective tissue, right mediastinal pleura, trachea, right bronchus, lymphnodes and 

ascending aorta. In the intrapericardial segment, the SVC enters the right atrium on the 

upper right face of the heart; in front it is close to the right main pulmonary artery. On the 

right side, the lung is in its proximity, separated only by mediastinal pleura. The right 

phrenic nerve runs next to the SVC for its entire course [1] (Figure 1). 

The SVC receives a single affluent vein: the azygos vein. The azygos vein joins the SVC from 

the right side, at its mid length, above the right bronchus. The Azygos vein constantly 

receives the superior intercostal vein, a large vessel which drains blood from the upper two 

or three right intercostal spaces. In the case of SVC obstruction, the azygos vein is 

responsible for the most important collateral circulation. According to the expected 

collateral pathways, the SVC can be divided into two segments: the supra-azygos or 



Topics in Thoracic Surgery 



preazygos and the infra-azygos or postazygos SVC. There are four possible collateral 

systems which were first described in 1949 by McIntire and Sykes. They are represented by 

the azygos venous system, the internal thoracic venous system, the vertebral venous system 

and the external thoracic venous system [2]. The azygos venous system is the only direct 

path into the SVC. The internal thoracic vein is the collector between SVC and inferior vena 

cava (IVC) via epigastric and iliac veins. The vertebral veins with intercostals, lumbar and 

sacral veins, represent the posterior network between SVC and IVC. The external thoracic 

vein system is the most superficial and it is represented by axillary, lateral thoracic and 

superficial epigastric veins.  



Fig. 1. 

The SVC is a constituent part of the right paratracheal space (also called “Barety's space”), 

containing the main lymphatic route of the mediastinum, i.e.  the right lateral tracheal 

chain.  Barety's space is bounded laterally by the SVC,  posteriorly by the tracheal wall, 

and medially by the ascending aorta. The nodes of the right paratracheal space are 

frequently involved in malignant growths: the SVC is undoubtedly the anatomical 

structure of this space which offers less resistance to compression, due to its thin wall and 

low internal pressure.    

Anatomical anomalies are rare. The most frequent is the double SVC which has an 

embryologic etiology [1]. 



Superior Vena Cava Syndrome 



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