In anatomy, a persistent left superior vena cava is the most common variation of the thoracic venous system.

[4][5] If an anomaly is detected during a routine ultrasound, a fetal echocardiogram is performed to determine whether a fetus has the condition.

[citation needed] CT and MRI scans in a parasagittal section may show a "pipe" sign where the left superior vena cava occurs.

[4] If no other cardiac abnormalities are present, persistent left superior vena cava will not be treated, as it is usually asymptomatic and unharmful.

[4] If it drains into the left atrium, then deoxygenated blood enters the circulation to the body, and cyanosis may occur.