Cranial vena cava injection study in a dog. The course of the vena cava reaching the dorsocaudal border of the heart indicates that it is a left sided cranial vena cava (LCVC) with characteristic blood flow into a large coronary sinus (CS) and thence into the caudal aspect of the right atrium (RA). The right atrial appendage (RAA) is large. Contrast material persisting in the right atrium and right ventricle indicates probable tricuspid regurgitation.

Continued cranial vena cava injection study in a dog. The left atrium (LA) is compressed by the large, non-opaque coronary sinus (CS).