Cardiac > Congenital > Leftsvc

Apr 2, 2002

Left superior vena cava:

Clinical:

A left SVC is found in about 0.3% of healthy individuals and in 4.4-10% of patients with congenital heart disease (the higher incidence of CHD is associated with coexistent absence of the right SVC) [4]. It is the most common congenital thoracic venous abnormality [4]. The anomaly is due to persistence of the embryonic left anterior cardinal vein. The left jugular and left subclavian vein join to form the left superior vena cava which is typically detected as an incidental finding in an adult patient. There is usually a right superior vena cava and a bridging vein often connects the two cavae across the anterior mediastinum. A left SVC is associated with absence of the left brachiocephalic vein in 65% of patients and absence of the right SVC in 10-18% of patients.

X-ray:

CXR: The left SVC appears as a prominent vertical border along the left superior mediastinum which is lateral to and does not obscure the aortic knob.

CT/MRI: CT or MRI will both demonstrate the additional vessel which typically courses lateral to the aortic arch and anterior to the left hilum. In the vast majority of patients the vessel terminates in the coronary sinus of the right atrium which will be enlarged. The left superior intercostal vein (which appears as a continuation of the hemiazygous vein) will swing around the aorta and insert into the left SVC. In a small minority of patients (generally with underlying congenital heart disease [3]) the left SVC will drain into the left atrium creating a left-to-right shunt. Patients with left SVC to left atrium drainage also have a substantially increased prevalence of congenital heart disease.

Left SVC: The patient below was incidentally found to have a left SVC (white arrow). Contrast had been injected in the left arm and there was no connection to the right superior vena cava. The left SVC drained to the coronary sinus (black arrows).