Discussion

We report an interesting case of an anomalous right coronary arterial origin from the supra-commissural aspect between the left and right coronary sinus, and demonstrated that multi-detector computed tomography gave excellent definition and spatial resolution of the anomalous origin, intramural and inter-arterial course. It is crucial to have a high index of suspicion of exertional symptoms, as sudden death may be its first manifestation.

The incidence of coronary arterial anomalies in otherwise normal heart ranges from 0.2% of young patients undergoing echocardiography to 1.2% of patients at angiography.Reference Davis, Cecchin, Jones and Portman^1, Reference Angelini, Velasco and Flamm² The incidence was much higher at 5.6% in a study of adults undergoing coronary angiography for investigation of coronary artery disease, and 1.1% of this cohort was found to have an ectopic right coronary arterial origin arising outside the borders of the right coronary sinus.Reference Solanki, Gerula and Randhawa³

Solanki et alReference Solanki, Gerula and Randhawa³ precisely described an ectopic right coronary artery as one that originates outside the posterior two-thirds of the right coronary sinus. Using this definition, the most common origin of an anomalous right coronary artery is within the anterior third of the right coronary sinus, followed by an anomalous origin from the left-facing sinus. It rarely originates from the non-coronary sinus, left anterior descending or circumflex arteries, pulmonary artery or descending aorta.Reference Rath and Battler^4, Reference Cheatham, Ruyle and McManus⁵

Our patient was interestingly found to have an anomalous location of the right coronary ostium from outside the sinuses, arising from the supra-commissural margin between the left and right coronary sinuses. This anomaly has not been specifically defined in Angelini's extensive classification of coronary anomalies,Reference Angelini, Velasco and Flamm² nor has it been reported in large series as a cause of an ectopic coronary arterial origin. The reasons for this are unclear – either the lesion described in our case is exceedingly rare, or it is grouped by authors to be a form of an anomalous right coronary arterial origin from the left or right sinus of Valsava.

An anomalous coronary artery gains significant clinical importance if the arterial origin takes an intramural and/or inter-arterial course, potentially leading to coronary compression, myocardial ischaemia, and sudden death. This is mainly reported in the setting of an anomalous origin from the opposite-facing coronary sinus. A slit-like ostium, oblique angulation or high take-off are associated with an anomalous coronary arterial origin, and may further interrupt coronary flow and cause arterial vasospasm.

Our patient had chronic exertional symptoms with an unremarkable baseline work-up. Computed tomography was arranged due to the suspicious history and the fact that coronary arterial arrangement was not adequately seen on echocardiography. It reflects the importance of taking a careful and thorough history, despite symptoms being a feature in only 38% of individuals who have a malignant coronary arterial abnormality. Younger patients are more likely to die suddenly or during exercise compared with older patients aged greater than 30 years of age, and symptoms are more common shortly before sudden death.Reference Basso, Maron, Corrado and Thiene^6, Reference Taylor, Rogan and Virmani⁷ Although the presence of symptoms do not predict the risk of sudden death,Reference Taylor, Rogan and Virmani⁷ it is crucial to have a high index of suspicion for cardiac disease as sudden death may be an avoidable event.

Indeed, coronary arterial anomalies are the second most common cause of sudden cardiac death in competitive athletes,Reference Basso, Maron, Corrado and Thiene^6, Reference Taylor, Rogan and Virmani⁷ and has been reported to account for 19% of sudden death in young athletes.Reference Maron, Thompson and Puffer⁸ The high-incidence of cardiac events in athletes may relate to arterial compression of the anomalous coronary artery and interference in diastolic coronary perfusion in increased cardiac output states.Reference Pelliccia⁹

The diagnostic yield of echocardiography is high, provided the clinician is confident with defining coronary arterial origins and its course.Reference Pelliccia, Spataro and Maron¹⁰ Further non-invasive imaging is required if there is a high suspicion based on symptoms, or if the coronary arteries are not well defined on echocardiography.

Multi-detector computed tomography gave excellent two- and three-dimensional delineation of the anomalous right coronary arterial origin and course. It not only assisted with the diagnosis, but also provided the surgeon with a clear visual image of the precise right coronary arterial origin between the left and right sinuses. Focused coronary imaging endeavours to reduce the amount of contrast used and the dose of ionising radiation. Coronary magnetic resonance angiography requires little to no contrast or radiation, however it may yield less spatial resolution than computed tomography and cannot be used with pacemaker devices.

The management of a symptomatic patient with an anomalous coronary arterial origin includes unroofing of the anomalous artery, translocation, ostioplasty or bypass grafting. There are good short-to-medium term but no long-term outcomes for unroofing and bypass grafting.Reference Angelini, Velasco and Flamm² Many authors favour surgical correction even in asymptomatic cases, over medical therapy or discouraging an active lifestyle, in order to prevent a catastrophic event.Reference Davis, Cecchin, Jones and Portman^1, Reference Angelini, Velasco and Flamm²

In summary, it is imperative to high index of suspicion of exertional symptoms and to investigate thoroughly, so that a catastrophic event may be avoided. We found that multi-detector computed tomography gave excellent definition and spatial resolution of the unusual origin and intramural right coronary arterial course.