Superior vena cava
The superior vena cava (SVC, also known as the cava or cva) is a short, but large diameter vein located in the anterior right superior mediastinum. Its latin name is related to its large pipe appearance in cadavers, 'cava' meaning 'hollow'.
The superior vena cava is very important for the function of the cardiovascular system, since it largely contributes to the input of blood to the right atrium. Any hypertensive process in the right half of the heart or in the pulmonary circulation retrogradely affects both superior and inferior venae cavae. This is important since the veins are not adjusted to high pressures, which can result with forming an aneurysm or even rupture of the wall of the SVC.
This article will discuss the anatomy and function of the superior vena cava.
|Source||Brachiocephalic vein, azygos vein|
|Draining area||Upper half of the body (above the diaphragm)|
|Drains to||Right atrium of heart|
- Clinical notes
Embryologically, the SVC is formed by the left and right brachiocephalic veins (also known as the innominate veins) that also receive blood from the upper limbs, certain parts of the head, one being the eyes, and neck.
There is no valve that divides the SVC from the right atrium, which conducts blood from right atrial and right ventricular contractions upwards into the internal jugular vein (seen as the jugular venous pressure) and sternocleidomastoid muscle.
Positionally, the SVC begins behind the lower border of the 1st right costal cartilage and descends vertically behind the 2nd and 3rd intercostal spaces to drain into the right atrium at the level of the 3rd costal cartilage. Its lower half is covered by a fibrous pericardium, which is pierced by the SVC at the level of the 2nd costal cartilage.
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The SVC is one of the 2 large veins by which blood is returned from the body to the right side of the heart. After circulating through the body systemically, deoxygenated blood returns to the right atrium of the heart through either the SVC, which drains the upper body, or the inferior vena cava (IVC) that drains everything below the diaphragm.
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Test yourself on the superior vena cava and other neurovasculature of the posterior mediastinum with the quiz below to consolidate what you learned so far!
Superior vena cava obstruction (SVCO)
This usually refers to a partial or complete obstruction of the SVC, often in the context of cancer (lung cancer, metastatic cancer, or lymphoma). Clinically this obstruction can lead to enlarged veins in the head and neck, and cause shortness of breath, cough, chest pain, and difficulty swallowing).
A clinical test known as Pemberton’s sign can be performed to identify this condition. A positive Pemberton's sign is marked by facial congestion and cyanosis (and/or respiratory distress) after 1 minute of having the patient elevate both arms until they touch the sides of the face. This sign is indicative of superior vena cava syndrome, commonly the result of a mass in the mediastinum.
Superior vena cava syndrome (SVCS)
This syndrome refers to a group of symptoms caused by the obstruction of the SVC. More than 90% of the cases of SVC obstruction are caused by cancer, most commonly bronchogenic carcinoma, which includes small cell and non-small cell lung carcinoma, Burkitt’s lymphoma, lymphoblastic lymphomas, pre-T-cell lineage acute lymphoblastic leukemia, and other acute leukemias.
Characteristic symptoms are edema of the arms and face, development of swollen collateral veins on the front of the chest wall, shortness of breath, difficulty swallowing, stridor, cough, and neurological symptoms (reduced alertness, etc. from edema in the brain or airway compromise). Again, Pemberton’s sign can be used to identify an SVCO.
Superior vena cava thrombosis
The thrombosis often occurs from a thrombus around a long-term central venous catheter (CVC), especially in cancer patients with permanent indwelling CVCs. CVC-related thrombosis is as high as 30% in adults. However, patients can be treated with thrombolytics or anticoagulants, or by removal of the catheter.
Superior vena cava aneurysm
Venous aneurysms arising from the mediastinal systemic veins are extremely rare, with the majority being fusiform (“spindle-shaped”) aneurysms that arise from the SVC.
Persistent left superior vena cava (PLSVC)
A PLSVC is an embryologic remnant that is the most common variation of the thoracic venous system, resulting from a failure to involute during embryologic development.
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