The gap between the aorta and the superior vena cava: A sonographic sign of persistent left superior vena cava and associated abnormalities.

OBJECTIVES

To assess the distance between the right superior vena cava (SVC) and the aorta in fetuses with bilateral superior vena cava as a possible sonographic marker for this.

METHODS

This was a nested case-control study including 20 cases of bilateral SVC and 40 gestational age-matched controls. The distance between the right SVC and the aorta was measured at the level of the three-vessel trachea view in stored images, as well as the diameters of the aorta and the right SVC.

RESULTS

The distance between the aorta and the right SVC was significantly larger in the cases of a left SVC compared with controls, P < .001. A distance of 2.0 mm or more was found in 70% of the cases and 5% of the controls, with a gestational-age adjusted area under the receiver-operating characteristics (ROC) curve for the diagnosis of left SVC of 0.93 (95% CI 0.87-0.99). The aorta and the right SVC were significantly smaller in cases compared with controls, and there was a significant association with other cardiac and extracardiac abnormalities amongst cases of persistent left SVC.

CONCLUSION

An increased distance between the aorta and the right SVC is associated with the diagnosis of bilateral SVC.