Discussion

To our knowledge, this is the first report of a single coronary artery originating from the right aortic sinus with a pre-pulmonic left anterior descending artery, retro-aortic left circumflex artery, and dual left anterior descending artery. There has been only one previous image describing a single coronary artery, pre-pulmonic left anterior descending artery, and retro-aortic left circumflex artery.Reference Neufeld and Scheeeweiss ¹

Coronary anomalies are congenital disorders with a wide spectrum of expression, clinical, and pathophysiological features. Broadly, these can be classified as anomalies of origin, course, intrinsic anatomy, termination, or anastomotic vessels, each with several subtypes.Reference Angelini ² The overall incidence has been shown to be 5.6%,Reference Angelini, Villason, Chan and Diez ³ with the majority (80%) of them being asymptomatic; however, these anomalies can cause myocardial ischaemia, syncope, cardiac failure, myocardial infarction, and death. In military recruits, 33% of sudden cardiac deaths are caused by anomalous origin of the coronary artery from the opposite sinus.Reference Eckart, Scoville and Campbell ⁴ In another study, coronary artery anomalies were found in 0.6% of patients with sudden cardiac death.Reference Drory, Turetz and Hiss ⁵ CT can provide exquisite detail of the origin and course of the coronary arteries, their anatomical relationships with other major cardiac structures, atherosclerosis, and luminal stenosis.Reference Kim, Seo and Do ⁶

Single coronary artery is a rare anomaly, with an incidence of 0.0024–0.044%, in which a single coronary artery originates from a single ostium in the aortic sinus.Reference Desmet, Vanhaecke and Vrolix ⁷ The terminology should be based on the nature of the aortic sinus giving rise to the solitary coronary artery. This can be either the right-handed sinus (#1) or the left-handed sinus (#2) as viewed by the observer standing in the non-adjacent sinus. To the best of our knowledge, a solitary coronary artery has yet to be described when arising from the non-adjacent sinus. Other congenital defects are associated in 40% of these patients.Reference Desmet, Vanhaecke and Vrolix ⁷ This anomaly is usually discovered incidentally, although there is a higher risk of sudden cardiac death if there is an interarterial course between the aorta and the pulmonary artery. More importantly, stenosis of the single artery can result in significant haemodynamic compromise if adequate collateral vessels are not developed.

A retro-aortic course is the most common type of coronary anomaly, seen in 0.9% of the population.Reference Shriki, Shinbane and Rashid ⁸ The left circumflex artery is the most commonly involved artery, which originates either from the right coronary artery or the right aortic sinus and then runs posterior to the aortic root and anterior to the left atrium. Usually, this anomaly is asymptomatic without any clinical significance; however, this anomaly is important to recognise in patients being evaluated for aortic root/valve surgical/interventional procedures so that injury can be avoided. Access for bypass graft to the left circumflex artery may also be difficult in this anomaly. Myocardial ischaemia, infarction, and sudden death have been reported, presumably due to compression of the artery by the dilated aortic root, slit-like ostium, or unusual angling.Reference Corrado, Penelli, Piovesana and Thiene ^{9 –} Reference West, McKenna, Ormerod, Forfar, Banning and Channon ¹¹

Pre-pulmonic course is a rare ectopic course of the coronary artery, where either the left main, the left anterior descending, or the left circumflex artery course anterior to the pulmonary artery or the right ventricular outflow tract. Rarely, the right coronary artery originates from the left anterior descending artery or the left main artery and has a pre-pulmonic course.Reference Corrado, Penelli, Piovesana and Thiene ⁹ This anomaly is commonly seen in tetralogy of Fallot.Reference Davis, Teske, Allen, Cohen and Schauer ¹² This anomaly should be recognised in patients being evaluated for repair of tetralogy of Fallot or percutaneous pulmonary valve replacement, so that injury to the coronary artery can be avoided. Pre-pulmonic course of a single coronary artery with the left main trunk has been reported, presenting with ischaemia due to stretching of the ectopic vessel as it courses anterior to the right ventricular outflow tract.Reference Sanford, Molavi and Sinha ¹³

Dual left anterior descending artery is a rare anomaly, which is defined as the presence of two distinct segments of vessels occupying the anterior interventricular groove of the heart.Reference Bozlar, Ugurel and Sari ¹⁴ There is a long left anterior descending artery that extends along the entire length of the anterior interventricular groove and a short descending artery that terminates high in the anterior interventricular groove. Several subtypes have been described,Reference Bozlar, Ugurel and Sari ¹⁴ depending on the origin of the long and short branches. The long branch can originate from the left anterior descending artery proper, the right coronary artery, or the right coronary sinus and the course can either be epicardial, pre-pulmonic, or intramyocardial. The short branch can originate from the left anterior descending artery proper, the left main coronary artery, or the left coronary sinus. The septal branches usually originate from the short left anterior descending artery, whereas the diagonal branches originate either from the long left anterior descending artery, the left anterior descending artery proper, or occasionally the short left anterior descending artery. Knowledge of this anatomy is important to plan for surgical re-vascularisation, as grafts may be needed for both the vessels. If the right coronary origin of the left anterior descending artery is not recognised, the short left anterior descending artery may be confused with the mid left anterior descending artery occlusion.Reference Agarwal and Kazerooni ¹⁵

Our cases also illustrate that to provide full descriptions of coronary arterial distribution, it is necessary to account not only for the sinusal origin but also for the course of the major arteries relative to the arterial pedicle. For describing the coronary sinuses and coronary arteries, an attitudinally correct nomenclature – that is, description according to the position they occupy in the body – is essential.Reference Cook and Anderson ¹⁶ The aortic sinuses are labelled as right coronary, left coronary, and non-coronary depending on the origin of the coronary arteries. The sinuses are accounted and described assuming that the heart is standing on its apex, with long axes occupying the sagittal and coronal planes, which is not correct, as the correct attitudinal position is with the apex pointing to the left and the right heart chambers positioned anterior to the so-called left-sided chambers. In our cases, the sinus from which the solitary artery arises is anterior rather than being right sided. As this is the solitary coronary sinus, it should be described as being “#1” or to the right hand when viewed from the non-adjacent sinus. The major branches of the coronary arteries occupy either the atrioventricular or the interventricular grooves. The right coronary artery occupies the right atrioventricular groove and the left circumflex artery occupies the left atrioventricular groove. The left anterior descending artery occupies the anterior/superior interventricular groove, and hence should be labelled as superior interventricular artery. The so-called posterior descending artery, which decides the coronary dominance, is neither posterior nor descending, and should be appropriately labelled as the inferior interventricular artery,Reference Cook and Anderson ¹⁶ as it runs on the inferior surface of the heart and supplies the inferior wall.Reference Cook and Anderson ¹⁶