Right coronary artery. Originates from the anterior (new nomenclature: right) aortic sinus. It passes anteriorly between the pulmonary trunk and the right auricle to reach the atrioventricular sulcus in which it runs down the anterior surface of the right cardiac border and then onto the inferior surface of the heart. It terminates at the junction of the atrioventricular sulcus and the posterior interventricular groove by anastomosing with the circumflex branch of the left coronary artery and giving off the posterior interventricular (posterior descending) artery. It supplies the right atrium and part of the left atrium, the sinuatrial node in 60% of cases, the right ventricle, the posterior part of the inter- ventricular septum and the atrioventricular node in 80% of cases.
Left coronary artery. Arises from the left posterior (new nomenclature: left) aortic sinus. It passes laterally, posterior to the pulmonary trunk and anterior to the left auricle to reach the atrioventricular groove where it divides into an anterior interventricular (formally left anterior descending) artery and circumflex branches.
The circumflex artery runs in the atrio- ventricular sulcus around the left border of the heart to anastornose with the right coronary artery. The anterior inter-ventricular artery descends on the anterior surface of the heart in the anterior interventricular groove and around the apex of the heart into the posterior interven-
tricular groove where it anastomoses with the posterior interventricular branch of the right coronary artery. The left coronary artery supplies the left atrium, left ventricle, anterior interventricular septum, sinuatrial
node in 40% of cases and the atrioven- tricular node in 20%.
Dominance. In approximately 10% of hearts the posterior interventricular artery arises from the circumflex artery (left coronary) and then most of the left ventricle and interventricular septum are supplied by the
left coronary artery. The heart is said to have left cardiac dominance.