Persistent left superior vena cava (PLSVC) and possible Partial anomalous pulmonary venous return (PAPVR)

56-years old female was referred to our department for a routine chest CT. Chest X-ray, which was performed in a smaller regional hospital for chronic coughing and possible COVID-19 pneumonia, revealed right hilar enlargement and a central pulmonary mass was suspected (chest X-ray images were not available). No other medical history was available.

Routine post-contrast chest CT images revealed persistent left superior vena cava (LSVC), originating below the junction of the left subclavian and internal jugular veins, coursing inferiorly to the left of the aorta and main pulmonary artery, and finally draining into the right atrium via the dilated coronary sinus. Normal anatomical position of the right superior vena cava (RSVC) was also found. Bridging vein (BV) was not present. Additionally, anomalous drainage of the right upper pulmonary vein into the right SVC was suspected. Dilation of central pulmonary arteries and segmental pulmonary branches indicate pulmonary hypertension.

Lung window analyses revealed prominent mosaic attenuation in both lungs and enlarged pulmonary branches surrounded by the area of hypoperfused lung. No lung or mediastinal masses were found.

Persistent left superior vena cava (PLSVC) is the most common congenital anomaly of the thoracic venous system. When accompanied (in up to 90% of the cases) by normal, right sided superior vena cava (RSVC) anomaly is called double SVC (DSVC). Both veins may be connected with the left brachiocephalic vein, which is then known as bridging vein (BV). PLSVC may be detected as an incidental finding in asymptomatic patients when cardiovascular imaging is performed for various reasons, or due to an atypical course of the catheter on a post-procedural chest X-ray [1-3]. When symptomatic, PLSVC is often associated with other congenital cardiovascular anomalies, most frequently ASD, VSD or less frequent variants such as anomalous pulmonary venous drainage (APVD), which was suspected in this case. The clinical significance of PLSVC depends on the drainage site and the type of accompanying anomalies. The most common site of drainage is the right atrium via the often dilated coronary sinus. Dilatation of CS may cause compression of the atrioventricular node and left atrium and lead to cardiac arrhythmias [1-3]. Less frequently the left atrial drainage is found.

Post-contrast computed tomography (CT) is most commonly used for the diagnosis. It can easily depict anomalous vessel course, diameter and termination.

Partial anomalous pulmonary vein return (PAPVR), as potential co-existing anomaly shown in this case, could be the main reason for the enlargement of the right hilum. Right upper lobe pulmonary veins draining into RSVC lead to left to the right shunt, increased pulmonary flow and consequently pulmonary hypertension. If the patient is referred to CT for non-specific reasons, and vascular anomaly is not instantly depicted, analyses of pulmonary vasculature and presence of mosaic attenuation in the lungs may become most helpful. Differentiating the vascular causes of mosaic attenuation from more frequently found small airway disease is crucial. Enlarged central pulmonary arteries, increased ratio between segmental bronchi and adjacent pulmonary artery branches are suggestive of pulmonary hypertension. In advanced stage right ventricular hypertrophy and enlargement, flattening and deviation of interventricular septum may be found [4]. However, because biphasic contrast protocol injection was used, which led to equal enhancement of both pulmonary arteries and veins, it became difficult to distinguish margins between these structures. Dedicated ECG-gated cardiac CT for the evaluation of pulmonary veins might be a useful tool for further clarification and final diagnosis.  In conclusion, this case report highlights the role of a routine chest CT in the assessment of vascular anomalies. A thorough analysis of chest vasculature may become the most helpful tool for the final diagnosis.