Right to left shunting through communications between the left superior intercostal vein tributaries and the left atrium: A potential cause of paradoxical embolism

ObjectivesTo investigate the role of collateral venous pathways between the left brachiocephalic vein (LBV) and the left atrium through an arcade comprising the left superior intercostal vein (LSICV), left vertical vein (LVV), and pulmonary veins as a potential cause of paradoxical embolism.MethodsA retrospective search was performed to find symptomatic patients with negative work up for paradoxical emboli whose chest CT or MR angiography by left arm contrast injection showed a visible right to left shunt through the LSICV/LVV collateral pathway (symptomatic group). We also evaluated the characteristics of this collateral pathway in 150 chest CT angiographies from general referrals (comparison group).ResultsWe found 7 symptomatic patients. Initial presentations included neurological symptoms in all patients and episodes of hypoxemia in three patients. Communications between the LBV and left atrium through the LSICV/LVV pathway was seen is all 7 cases and confirmed by transesophageal echocardiography in two. An abnormal LBV was seen in 6 cases (absence in one, stenosis in 5). Moderate superior vena cava stenosis was seen in one and acute right subclavian vein thrombosis in one. Six patients had past history of an upper extremity central line placement. In the comparison group, LSICV was seen in 73 (48%), connecting to the hemiazygos vein in 41, to a LVV in 19 and to the left atrium in 7.ConclusionLSICV/LVV collaterals are common and can be a potential route for paradoxical emboli especially when stenosis of a draining vein such as LBV exists.