Coronary sinus injection study in a dog with patent ductus arteriosus. Note the normal size of the coronary sinus (CS), retrograde flow into the great cardiac vein (CV) and antegrade flow into the right atrium (RA).

Continued coronary sinus injection study in the dog with patent ductus arteriosus. Note the increased pulmonary artery size (P) and wide pulsatile diameter changes in the aorta (arrows) indicative of wide pulse pressure. Left-to-right recirculating flow through the patent ductus arteriosus (obscured) causes persistent opacity of the heart.