Myocardial coverage of the coronary sinus and related veins

The incidence and distribution of landmarks relating to the coronary sinus (c.s.) were evaluated in 240 human hearts. Special attention was directed to the myocardial coat of the c.s., the distribution and pattern of the cardiac veins, and their dimensions. In all specimens the myocardial coat of the c.s. also covered the adjacent 2 to 11 mm of the great cardiac vein. In 15% of cases this myocardial layer was thickened in a sphincter-like fashion, the edge of which was formed obliquely, in a crescent-like manner, or diffusely without a sharp border. In 3% of the hearts the myocardial cover of the c.s. extended over the terminal 10 mm of the middle cardiac vein as a strong fiber cord. In 9%, single isolated belts of fibers fixated the terminal parts of the adjoining cardiac veins to the posterior wall of the left atrium, and in 8% two or three myocardial cords, embedded in the fatty tissue of the left coronary sulcus, did the same. Because the myocardial cover extended leftwards to variable distances over the c.s., the left edge of the myocardial covering cannot serve to define the beginning of the coronary sinus. The location of the ostial valve of the great cardiac vein (valve of Vieussens) was variable as well, being found on the average 2.5 mm proximal to the opening of the oblique vein of the left atrium. Moreover, the valve of the great cardiac vein was found in only 87% of cases; therefore it is inappropriate for defining the beginning of the coronary sinus. Finally, the dot-like ostium of the oblique vein was most constant, and from the viewpoint of embryologic development, it is the logical landmark for determining the beginning of the coronary sinus, a necessary presupposition for cardiologic procedures like reperfusion of cardiac veins.