The cardiological literature on coronary arterial anatomy consistently neglects the atrial portion of it. There are several reasons for this, most notably that the ventricular portion of the coronary articulation is larger and much more important to the clinician than is the atrial, and that the atrial arteries are extremely variable. Since large coronary arteries are related to the large myocardial masses that are ventricular, they do not appear in the atrial territory. Only 2 coronary atrial arteries are generally recognized with a term more specific than “atrial branch”: the sinus node and the atrioventricular node arteries. The great number of open heart operations now performed via the right atrium, makes knowledge of the arrangement of the atrial arteries, particularly the sinus node artery, very important for the surgeon [1]. A 56-year-old women underwent elective coronary angiography before surgical repair of severe mitral insufficiency. No coronary artery disease was noted. On selective left coronary angiography an abnormally huge S-shaped Sinus Node Artery (SSNA, Fig. 1A and B). The sinus–atrial node was supplied by the right coronary artery more frequently (73% of cases) than by the left (3%), and in 23% of cases this node was supplied by both coronary arteries. The SSNA may be found up to 21.5% of patients with sinus node artery, and