CASE 12168 Published on 27.09.2014

SVC\'s ostium obstruction causes a right-to-left shunt: unusual acquired systemic-to-pulmonary venous collateral pathway

Section

Cardiovascular

Case Type

Clinical Cases

Authors

F. Ho-Mouye, J-Y Travers

Radiology department,
CHU Felix Guyon,
Allee des topazes,
97400 Saint Denis,
Reunion Island
email: fhm33000@hotmail.com
Patient

63 years, female

Categories
Area of Interest Cardiovascular system ; Imaging Technique CT
Clinical History
A 63-year-old woman was referred for CT examination for suspicion of pulmonary embolism. She had a history of Ebstein disease and tricuspid valves replacement decades ago, but no pulmonary disease nor anaemia. A recent echocardiography showed normal right and left contractile functions, yet an enormous thrombus in the right atrium. No shunt were visible.
Imaging Findings
*As expected, artificial tricuspid valves and a huge thrombus in the right atrium were found. However, upon contrast injection at pulmonary arterial phase, pulmonary artery and aorta showed reversed contrast: contrast followed the superior vena cava then flowed through an unsual "bag of worms"-like ductus into the superior left pulmonary vein, thus creating a right-to-left shunt. This so-called ductus was located around the right hilar region and included the azygos vein.

*The rest of the cardiac anatomy was normal, with situs solitus of the viscera and atria (S), ventricular D-loop (D), and solitus-related great arteries (S): S, D, S.

*No pulmonary embolism was seen.

*CT evidence showed this unusual right-to-left shunt causing dyspnoea.
This patient's case emphasized an unusual pathway through preexisting bronchial venous plexuses which link the right atrium to the left superior pulmonary vein.
Discussion
- Chronic obstruction of superior vena cava is commonly an acquired condition due to thrombus, mediastinal mass or fibrosis. Thus, bloodstream often goes through the aygos-hemiazygos pathway, or internal mammary. However, in cases of SVC's ostium obstruction or enlarged right atrium, shunting of systemic-to-pulmonary venous pathway, normally prevented by venous valves, may be observed. [1]
- In a patient with cardiac insufficiency symptoms with preserved contractile function, clinicians have to rule out anaemia and possible shunts such as atrial septal defect (ASD), arterio-venous fistula from dialysis or other arterio-venous malformation. The first imaging needed is echocardiography. If non-contributive, consider contrast-enhanced body CT to look for shunts.
- Imaging is expected to find the location of a shunt, its primary cause, the anatomy of collateral pathways, as well as its severity in order to plan surgical treatment. The appropriate protocol could be pulmonary arterial phased acquisition as the table moves onward, followed by arterial phase acquisition as the table moves backward. Otherwise, a single acquisition with mixed phased can be performed.
- Therapy consists of endovascular or surgical closure of the collateral pathways, and treatment of their primary cause.

- Teaching point: In case of cardiac insufficiency with enlarged right atrium or SVC’s ostium obstruction, radiologists may find unusually shunting collateral pathways such as systemic-to-pulmonary venous pathway: bronchial plexus veins -> azygos vein -> left superior pulmonary vein.
Differential Diagnosis List
Systemic-to-pulmonary venous acquired shunt as collateral pathway.
Azygos-hemiazygos collateral pathway
Internal and external mammary collateral pathway
Lateral thoracic collateral pathway
Vertebral collateral pathway
Final Diagnosis
Systemic-to-pulmonary venous acquired shunt as collateral pathway.
Case information
URL: https://www.eurorad.org/case/12168
DOI: 10.1594/EURORAD/CASE.12168
ISSN: 1563-4086