...Well, it sometimes (~55-65%) comes off the right coronary artery... the rest of the time it arises from the LCx (30-45%).
A smaller % (<10%) of patients have a dual blood supply.
But regardless of which circulation it arises from, it can be recognized by its course toward the SVC.
According to one article, the termination of the SA node artery can be further classified as retrocaval (~47%), precaval (~43%), or pericaval (~10%) -- but whether this is significant is unclear.
|(a) retrocaval, (b) precaval, and (c) pericaval. (Ref 2)|
1. Kini S, Bis KG, and Weaver L. "Normal and Variant Coronary Arterial and Venous Anatomy on High-Resolution CT Angiography" AJR June 2007 vol. 188 no. 6 1665-1674
2. Saremi F, Abolhoda A, Ashikyan O, et al. "Arterial Supply to Sinuatrial and Atrioventricular Nodes: Imaging with Multidetector CT" Radiology: Volume 246: Number 1—January 2008