An S-shaped atrial artery supplying the sinus node area. An anatomical study.

An S-shaped sinus node artery (SSNA), originating in the posterolateral part of the left circumflex artery (LCir) below or behind the left auricle, is described in detail. The coronary vessels were studied in 300 human hearts by x-ray films or by casting of the vessels, and the SSNA was found in 24 (21.5 percent) of the 111 cases where the sinus node artery (SNA) arose from the LCir, (ie, 8 percent of all the hearts). The SSNA constituted a branch of the LCir in 15 cases, the upper part of a divided LCir in 6 cases, and the main continuation of this artery in 3 cases, always following basically the same route to the sinus node (SN) area. It was larger than the normal SNA, supplying the SN and surrounding area, almost the whole left atrium, a large part of the interatrial septum and right atrium, and partially supplying the atrioventricular node area.