Understanding coronary arterial anatomy in the congenitally malformed heart.

With the development of three-dimensional techniques for imaging, such as computed tomography and magnetic resonance imaging, it is now possible to demonstrate the precise sinusal origin and epicardial course of the coronary arteries with just as much accuracy as can be achieved by the morphologist holding the heart in his or her hands. At present, however, there is no universally accepted convention for categorising the various patterns found when the heart is congenitally malformed. In this review, we show how, to provide such a convention, it is necessary to take note not only of the sinusal origin of the three major coronary arteries, but also the relationship of the aortic root relative to the cardiac base. We summarise the evidence showing how the proximal portions of the developing coronary arteries grow into the aortic valvar sinuses subsequent to the separation of the aortic root from the subpulmonary infundibulum. We also discuss the evidence showing that the subpulmonary myocardium is impervious to the passage of epicardial coronary arteries, and suggest that the process of septation itself plays an integral role in guiding the arteries into the two aortic sinuses that are adjacent to the pulmonary root. We then show how marriage of convenience between the epicardial coronary arteries and the aortic valvar sinuses provides a good explanation for the known variations found in the setting of transposition. We point out that it is the absence of septation that likely governs the patterns seen in the setting of a common arterial trunk.

Describing the cardiac components--attitudinally appropriate nomenclature.

One of the first principles taught to medical students when they begin their study of human anatomy is that all structures within the body should be described as seen in the anatomical position. In this position, the subject is standing upright and facing the observer. The observer then views left-sided structures to the right hand and right-sided structures to the left hand. Those entities closest to the head are said to be superior, while those closest to the feet are considered to be inferior. And structures within the chest adjacent to the sternum are appropriately described as being anterior, with those adjacent to the spine properly being considered to be posterior. These conventions have been obeyed over the centuries for all organs except the heart. For reasons that are not clear, cardiac structures are described as though the heart has been removed from the thorax and positioned on its apex. This leads to unfortunate descriptions, such as the artery coursing through the middle of the diaphragmatic surface of the heart, blockage of which produces inferior infarction, being said to be posterior and descending. In reality, it is inferior and interventricular. The advent of three-dimensional techniques for imaging, such as computed tomography or magnetic resonance imaging, now demonstrates in unequivocal fashion the spurious natures of such descriptions, which extend also to the leaflets and papillary muscles of the atrioventricular valves. It is surely now incumbent on human anatomists and cardiologists to describe structures within the heart as they are seen relative to the thorax, in other words to do no more than follow a basic rule of human anatomy and use attitudinally appropriate terms. Whether clinical cardiologists will adopt such a logical approach is moot, but adoption will surely facilitate understanding for the future generations? This article is part of a JCTR special issue on Cardiac Anatomy.