The coronary sinus conduit function: anatomical study (relationship to adjacent structures)

The mitral valve annulus (MVA) is anchored antero-medially to the aorta. Dilatation of the MVA primarily affects its postero-lateral aspect, which is related to the coronary sinus (CS). The CS and its tributaries have been used for pacing the left ventricle in patients with intractable heart failure. The aim of this study was to determine anatomical relations between the CS and its adjacent structures in 40 adult normal cadaveric heart specimens.

In 32 specimens, longitudinal sections were made along the free circumference of the MVA in 6 separate regions, 36 degrees between each, with the 0 degree marked by a line joining the centre of the CS ostium and that of the MV. In each section, the relations of the CS to the circumflex artery and the MVA were determined. CS diameter and its distance from the endocardium, just below the MVA, were also measured by a digital calliper.

The great cardiac vein (GCV) diameter is 5.6 +/- 1.6 mm. As it leaves the interventricular groove, it curves to the left forming the base of the triangle of "Brocq and Mouchet" with the two branches of the left coronary artery, having a triple relationship with the circumflex artery. It then continues as the CS (diameter 9.3 +/- 5.3 mm) in the inferior atrioventricular groove. The end part of the GCV crosses superficial to the left circumflex artery at the level of the left marginal vein. The shortest distance between the wall of the CS and the endocardium adjacent to the MVA at the level of the anterolateral commissure is 5.2 +/- 1.6 mm, i.e. beyond the Vieussens valve. Thus, together with the CS the great cardiac vein, form a semicircular venous channel at the postero-lateral aspect of the MVA. In 37/40 hearts, this venous channel arches upwards in its middle part to be in direct contact with the left atrium.

This study demonstrates an intimate proximity between the coronary sinus, at its beginning and end, and the mitral valve annulus. It also highlights the close relationship between the great cardiac vein, the annulus and the left ventricular free wall. Assessing the same relationship using the currently available imaging techniques should aid in the successful cannulation of the coronary sinus for various cardiological interventions.