INTRAATRIAL COURSE OF THE RIGHT CORONARY-ARTERY AND ITS BRANCHES

OBJECTIVE: To illustrate and describe an anomaly of right coronary art ery (RCA) course. SETTING: Postmortem examination of cardiac tissue. D ESIGN AND PATIENTS: Three cases where the RCA had an intracavitary pos ition in the right atrium are described. Additionally, light microscop ic analysis of random sections of posterior right atrium from 100 cons ecutive autopsy cases was undertaken. MAIN RESULTS: Each of the index cases was an incidental finding at autopsy. In two cases, the RCA, aft er passing the acute angle of the heart (epicardially), entered the ri ght atrium posteriorly and ran subendocardially for distances of 1. 5 and 3.0 cm, respectively. In the third case, the RCA entered the right atrial cavity 2.5 cm from its origin and ran subendocardially for 2.0 cm. In all three cases, the RCA exited the atria cavity and once agai n attained an epicardial course. In the first two cases, the RCA ran 1 .0 cm above the atrioventricular groove, rather than in its normal loc ation at the annulus. The random sections of right atriat wall showed that medium calibre arterial branches of the RCA also commonly run in subendocardial positions (29 of 100 cases) and sometimes project into the atrial cavity (five of 29 cases). CONCLUSIONS: The genesis of this epicardial coronary anomaly is unclear, but may relate to the 'higher ' than normal course of the artery in these cases, in concert with the normal thinness of the right atrial wall, and the tendency for even m edium calibre arteries to assume this subendocardial location. Despite the benign outcome of the index cases described here, the authors bel ieve that this intracavitary, course of the RCA could pose special tec hnical problems during coronary artery catheterization and bypass graf ting.