Letter from the Editor

A Vicious Vieussens' Circle?

When, in 1706, Raymond de Vieussens, for the first time, correctly described the anatomy of the coronary vessels of the heart, little did he know that he also delineated their confusing embryology [1]. In his studies he encountered an epicardial vessel proximally connecting what would become known as the left anterior descending artery (LAD) with the conus branch of the right coronary artery (RCA). He gave it the somewhat unflattering name “arteria adiposa”. In the 19th century this intercoronary connection was named in his honour as Vieussens' arterial ring [2]. Later again it was realized that this, also known as the conotruncal circle, constitutes the most cranial of three embryologic coronary loops also including the atrioventricular circle, forming the major part of the later RCA, and the interampullary circle, responsible for most of the left coronary artery [3]. It was, however, not until the 1980s when evidence was found that the coronaries do not sprout from the aortic root but rather develop independently as the aforementioned epicardial loops and then find their way to the aorta [4], [5]. It should be noted that these studies were published by an aspiring pediatric cardiac surgeon, at that time working in Adriana Gittenberger-de Groot's anatomy department at Leiden University. For this connection to the great vessels, Vieussens' ring seems to play an important, if not fully understood, role [6]. Variations in its embryologic progress lead to abnormal coronary patterns: e.g., LAD from RCA with retropulmonary course, ALCAPA (anomalous left coronary artery connecting to pulmonary artery), or the arrangements frequently seen with certain conotruncal forms of congenital heart disease such as transposition of the great arteries or tetralogy of Fallot.

Coronary artery surgery generally suggests palliation of acquired atherosclerotic heart disease, still constituting the major part of adult cardiac operations. But it does not stop there. In this issue you will also find remarkable observations on myocardial bridging and coronary aneurysmal disease. For both pathologies it helps to reflect on the embryological development of these small but vitally important vessels.

Whilst pondering on basic science it is also worthwhile to take the evolutionary concept of coronary arteries into account. On Darwin's ladder, coronaries appeared late, only with the birds and mammals, when the blood became warmer and the heartbeat faster. Amphibians and reptiles perfuse their myocardium by providing a large inner surface of their common ventricle. We encounter this in humans when the primitive ventricle prevails or if something goes wrong with the feeding vessels, for instance, in pulmonary atresia with right-ventricular dependent coronary circulation. The supposedly highest form of evolution will run into a serious problem if it continues to convert its coronaries into sclerotic wrecks. Coming a full Vieussens' circle, we as humans should bear in mind that alligators won't die from myocardial infarction.

References

• 1 Vieussens R. Nouvelles découvertes sur le coeur. Toulouse: Jean Guillmette; 1706
• 2 Gray H. Anatomy: Descriptive and Surgical. London: JW Parker & Son; 1858
• 3 Corone P, Corone A, Dor X, Binet J P. Coronary arteries and their variations: an embryological explanation.  C R Acad Sci III. 1984;  299 451-458
• 4 Bogers A J J C, Gittenberger-de Groot A C, Dubbeldam J A, Huysmans H A. The inadequacy of existing theories on development of the proximal coronary arteries and their connexions with the arterial trunks.  Int J Cardiol. 1988;  20 117-123
• 5 Bogers A J J C, Gittenberger-de Groot A C, Poelmann R E, Péault B M, Huysmans H A. Development of the origin of the coronary arteries: a matter of ingrowth or outgrowth?.  Anat Embryol. 1989;  180 437-441
• 6 Gittenberger-de Groot A C, Lie-Venema H, van den Akker N M, Winter E M, Poelmann R E. Coronary vascular development.  Wien Klin Wochenschr. 2007;  119 4-5