What is the superior vena cava?

The superior vena cava is a large vein located in the upper anterior mediastinum. The mediastinum is the space surrounded by the chest wall in the front, the lungs to the sides and the spine at the back. Subdivided into four divisions (upper, medial, anterior and posterior), the mediastinum contains the heart, blood vessels, trachea, large bronchi and part of the esophagus.

The superior vena cava is responsible for carrying deoxygenated blood from the upper body (head, neck, upper limbs, and some organs of the chest) to the heart. The heart then sends the deoxygenated blood to the lungs so it can be transformed into oxygenated blood to be pumped throughout the entire body.

The superior vena cava is approximately 7 cm in length and about 22mm in diameter. There is no valve that divides the superior vena cava from the right atrium. It is formed by the confluence of two large veins: the brachiocephalic veins (also known as the innominate veins) which travel down to the extreme sternal of the third costal cartilage towards the right, pierce the pericardium (the membrane containing the heart and the initial portions of the arterial vessels), and join with the azygos vein, just before entering into the right atrium, at the upper right front portion of the heart.

If the superior vena cava becomes narrowed or blocked, it can lead to a condition known as SVC obstruction. SVC obstruction is most often caused by cancer (lung cancer, metastatic cancer, or lymphoma) or tumor in the medastinum. Though the condition is rare, it can cause severe symptoms such as swelling, nausea, vomiting, vision changes, shortness of breath, chest pain, decreased alertness, throat blockage, fainting, and headaches.The speed of the blockage and its location determine the seriousness of the syndrome. The more quickly the airway gets blocked, the more severe the symptoms, since the other veins do not have time to widen to adjust to the increased blood flow. In such cases, an individual may need a ventilator to help with breathing. Sometimes, the other veins can take over  the superior vena cava’s function if it is obstructed, however this takes time.

Treatment of SVC obstruction depends on the cause of the obstruction, the seriousness of the symptoms, the patient’s overall health as well as their own preferences. Treatments that can be used for superior vena cava syndrome include: radiation therapy, chemotherapy, thrombolysis, stent placement and surgery. It is essential that the patient receive a proper diagnosis in order to determine the most appropriate form of treatment and prevent further complications (which can be severe and even fatal) from arising.


What function does the superior vena cava serve?

The superior vena cava is solely responsible for transporting deoxygenated blood from the upper portion of the body (head, neck, upper limbs, and some organs of the chest) into the heart, which then sends it to the lungs. Through small circulation, or pulmonary circulation, the blood is cleansed and sent back to the heart to be pumped full of oxygen and nutrients and further sent throughout the entire body.