FIG 46.5 Left ventricle from an individual with anomalous origin of the left coronary artery from the pulmonary trunk The ventricle has been opened along its inferior border, showing the fibrosis and infarction that also involves the inferoseptal papillary muscle of the mitral valve Anomalous Aortic Origin of the Coronary Arteries Abnormal aortic origin can take several forms For example, high take-off relative to the sinutubular junction, when excessive, is anatomically anomalous, although origins minimally above the sinutubular junction are common.6 It is abnormal sinusal origin that is now recognized as being of far more significance (Fig 46.6, left panel), particularly if associated with a so-called intramural course (see Fig 46.6, right panel) Recognition of abnormal sinusal origin means that it is necessary uniformly to distinguish between the sinuses themselves, irrespective of the relationship between the arterial trunks This can be done by assessing the view of the sinuses obtained by the observer, figuratively speaking, standing in the nonadjacent aortic sinus (Fig 46.7) When taking an anomalous origin, the abnormal vessel will almost always continue to arise from one or another of the two sinuses adjacent to the pulmonary trunk Using the convention suggested previously, which is equally valid in hearts with abnormal ventriculoarterial connections, the sinuses adjacent to the pulmonary trunk will either be to the right side or left side of the observer Convention now dictates that the right-side sinus is considered sinus 1, with the left-side sinus deemed to be sinus 2.7 This approach also accounts for anomalous origin of a major coronary artery from the nonadjacent sinus.8 Although this sinus is usually described as being noncoronary, that term is obviously inappropriate when the sinus gives rise to a coronary artery Such origin, in the absence of associated lesions, is unlikely to be of clinical significance unless associated with the intramural pattern FIG 46.6 Left, Anomalous origin of the right coronary artery from the leftside coronary aortic sinus, known as sinus 2, as viewed from the nonadjacent sinus Right, Section taken at the level of the sinutubular junction showing how the anomalous artery takes an oblique course through the aortic wall, crossing the so-called commissure (star) FIG 46.7 Concept of distinguishing between the aortic sinuses supporting the coronary arteries by “standing” in the nonadjacent sinus and looking toward the pulmonary trunk In individuals with normally related arterial trunks, the sinus on the left side, known as sinus 2, gives rise to the left coronary artery, with the right coronary artery usually arising from the sinus to the right side, known as sinus 1 Coronary arteries arising ectopically from the aorta can also take an anomalous course relative to the arterial roots Such anomalous courses can be retroaortic, interarterial, or prepulmonary When the anomalously arising artery runs between the arterial trunks, the arrangement is often described as being “interarterial.” The course can, indeed, extend deep within the crest of the muscular ventricular septum, but more usually the artery runs at the level of the sinutubular junction or within the area of fibro-adipose tissue separating the aortic root from the free-standing subpulmonary infundibular sleeve It is again the initial course of the artery that is more important It is more likely to be constricted when running within the wall of the aorta, particularly when crossing the peripheral attachments of the leaflets at the sinutubular junction, the socalled intramural arrangement (see Fig 46.6, right panel) Although any possible anomalous course must be anticipated, there are well-recognized common patterns Anomalous origin of the left coronary artery or the circumflex artery from sinus 1, for example, or from the RCA, is often associated with a retroaortic course through the transverse pericardial sinus (Fig 46.8)