Vasculature - Superior Vena Cava

Question 1

What veins give rise to the SVC?

Relevant part of the mediastinum?

Answer 1

Right and left brachiocephalic veins.

Middle mediastinum.

Question 2

Clinical relevance - jugular venous pressure?

Answer 2

SVC is a valveless structure. This allows pressure to be conducted upwards from the right atrium to the right internal jugular vein.

Visualisation of the right internal jugular vein is an indicator of the JVP - which in turn represents the pressure of the atrium.

To examine, patient should be at a 45 degree angle, with their head turned slightly to the left. Pulsation should be identified between the two heads of the sternocleidomastoid muscle.

Causes of raised JVP - right sided heart failure, pulmonary hypertension, and SVC obstruction.

Question 3

Tributaries of the SVC?

Answer 3

At the level of T4, the SVC receives the azygos vein, which drains the upper lumbar region and thoracic wall.

Other tributaries from several minor vein groups:

1) Mediastinal veins
2) Oesophageal veins
3) Pericardial veins

Question 4

Clinical relevance - SVC obstruction

Answer 4

Thin walled and low pressure vessel, making it vulnerable to compression.

Most common cause is due to malignancy, typically from lung cancer, lymphoma, or metastatic disease.

Vessel obstruction leads to swelling in the neck, face and upper limbs.

Clinical features - shortness of breath, distension of veins in the face and upper limb.

SVC obstruction can be tested by performing a Pemberton test. Patients are asked to raise arms above the head - postive test indicates facial oedema or cyanosis after approximately one minute.