The atrioventricular or coronary groove of the heart demarcates the borders of the underlying atria from the ventricles. It is a continuous sulcus but it has been described as right and left parts in the following section for the purposes of description.
On the right side it begins anteriorly and superiorly on the sternocostal surface having passed from its continuity with the left side of the groove from posterior to the ascending aorta. In the anatomical position, it passes inferiorly and to the right on the sternocostal surface to separate the right atrium and its auricle from the right ventricle inferiorly and its infundibulum superiorly. Then, it passes onto the anterior part of the diaphragmatic surface and courses to the left and posteriorly.
The left superior origin of the atrioventricular groove is in continuity with the right groove posterior to the aorta; it extends to the left, posterior to the pulmonary trunk and then turns inferiorly and to the right, anterolateral to the left pulmonary veins. At this point, the groove forms the left margin of the posterior surface of the heart and separates the left atrium from the left ventricle. It continues inferiorly and to the right to where it forms the posterior border of the diaphragmatic surface of the heart. Along this border, the left side merges with the right side of the atrioventricular groove.
If a transection of the heart is taken along the groove, the plane so formed is about 45 degrees to the sagittal plane, 25 degrees to the coronal plane and 30 degrees to the horizontal plane. Superior and to the right of this plane are the atria. Inferior and to the left of this plane are the ventricles. Approximately within this plane are the valves of the heart.