Myocardial distribution of retrograde flow through the coronary sinus of the excised normal canine heart.

Myocardial distribution of the retrograde flow through the coronary sinus in the canine heart was evaluated by observing the corrosion casts of the myocardial vessels after coronary sinus injection of a low-viscosity resin, Mercox, a compound that passes through capillaries. The apex and the left ventricular free wall were well perfused at the microvascular level, even in the presence of complete left main coronary artery occlusion, whereas the right ventricular free wall was not perfused effectively at this level in any heart. Although there was considerable variation in the perfusion of the ventricular septum from heart to heart, the entire septum was not perfused in some of the hearts. We considered this poor perfusion of the septum to be due to the presence of well-developed thebesian veins in the septum. Retrograde coronary sinus perfusion of cardioplegic solution may be a valuable alternative to protect the left ventricular free wall, especially in cases of critical coronary artery stenosis or occlusion. However, antegrade perfusion should be used also, whenever possible, for adequate protection of the septum and the right ventricular free wall.