The pathophysiological entity of a persisting left-sided superior caval vein draining into the roof of the left atrium represents an extreme form of coronary sinus de-roofing. This is an uncommon, but well-documented condition associated with systemic desaturation due to a right-to-left shunt. Depending on the size of the coronary ostium, the defect may also present with right-sided volume loading. We describe two patients, both of whom presented with desaturation, and highlight the important anatomical features underscoring management.

Both patients were managed interventionally with previous assessment of the size of the coronary sinus ostium through cross-sectional imaging. This revealed a restrictive interatrial communication at the right atrial mouth of the coronary sinus in both patients, which permitted an interventional approach, as the residual left-to-right shunt subsequent to closure of the aberrant vessel would be negligible. At intervention, test occlusion of the left superior caval vein allowed assessment of decompressing vessels before successful occlusion using an Amplatzer Vascular Plug.

Persistence of a left superior caval vein draining to the left atrium may be associated with an interatrial communication at the mouth of the unroofed coronary sinus. The ostium of the de-roofed coronary sinus can be atretic, restrictive, normally sized, or enlarged. Careful assessment of the size of this defect is required before treatment. In view of its importance, which has received little attention in the literature to date, we suggest an additional consideration to the classification of unroofed coronary sinus.