M01.05.024 Superior Vena Cava

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Learning Objective

Understand the anatomy, tributaries, and clinical relevance of the superior vena cava (SVC), including its role in jugular venous pressure and SVC obstruction.

Anatomical Position

The superior vena cava (SVC) is a large, valveless vein, measuring up to 2 cm in diameter and approximately 7 cm in length. It is formed by the union of the right and left brachiocephalic veins, posterior to the first right costal cartilage.

The SVC descends vertically through the superior mediastinum, lying behind the intercostal spaces and to the right of the aorta and trachea. At the level of the second costal cartilage, it enters the middle mediastinum and is enclosed by the fibrous pericardium, terminating in the right atrium at the level of the third costal cartilage.

Activity

Tributaries

The SVC collects venous blood from the head, neck, upper limbs, and thoracic structures. It is formed by the brachiocephalic veins, which drain the head, neck, and upper limbs. At the level of T4, it receives the azygous vein, which drains the upper lumbar region and thoracic wall.

Additional tributaries include:

Mediastinal veins
Oesophageal veins
Pericardial veins

Activity

Clinical Relevance

Jugular Venous Pressure (JVP)

The SVC is valveless, allowing right atrial pressure to be transmitted to the right internal jugular vein. The JVP is observed with the patient at a 45° angle, head turned slightly to the left. Pulsations between the sternocleidomastoid heads reflect right atrial pressure.

Raised JVP can indicate: right-sided heart failure, pulmonary hypertension, or SVC obstruction.

Superior Vena Cava Obstruction

The SVC is a thin-walled, low-pressure vessel, vulnerable to compression or occlusion. The most common cause is malignancy, such as lung cancer, lymphoma, or metastatic disease.

Obstruction disrupts venous return, leading to swelling of the neck, face, and upper limbs, with symptoms of dyspnea and venous distension. Pemberton’s test can assess obstruction: the patient raises both arms; a positive test is indicated by facial edema or cyanosis within 1 minute.