Anatomic variations of the coronary arteries supplying the anterolateral aspect of the left ventricle: possible explanation for the "Unexplained" anterior aneurysm.

Coronary arteriograms of 418 adult patients were studied to ascertain the frequency of variations in blood supply of the anterolateral free wall of the left ventricle; 92.6% had from one to three ramus medianus or diagonal branches supplying this area. Complete absence of any ramus medianus or diagonal branches was exceedingly rare (only 0.5% in this series), and when this occurs the angiographer should suspect complete occlusion of one or more such branches immediately at their origins. Failure to detect ostial occlusion of a ramus medianus or diagonal branch may be a cause of significant misinterpretation of coronary arteriograms.