Discussion

Our cases demonstrate that left main coronary artery atresia may be a rare, under-reported cause of sudden death in teens, and non-invasive modalities such as echocardiography and CT may be inadequate for diagnosis. Coronary angiography may be the only method to make a definitive diagnosis.

An anomalous coronary artery origin from the opposite sinus with an intra-mural or an inter-arterial course is well described as a cause of sudden death,^{Reference Brothers, Frommelt, Jasquiss, Myerburg, Fraser and Tweddell2} but occlusion of the left main coronary artery has not, presumably due to its rarity.^{Reference Yajima, Toda, Nishi, Yoshioka, Nakamura, Miyagawa, Yoshikawa, Fukushima and Sawa3} Left main coronary artery atresia differs from an intramural or inter-arterial course of an anomalous coronary artery, as the blood flows retrograde from smaller calibre collateral arteries to larger calibre left-sided vessels.^{Reference Musiani, Cernigliaro, Sansa, Maselli and De Gasperis4} Musiani et al hypothesise the collateral vessels are inadequate to meet the myocardial demand which leads to cardiac and coronary insufficiency.^{Reference Musiani, Cernigliaro, Sansa, Maselli and De Gasperis4}

Both our patients underwent echocardiography in a well-equipped laboratory with sonographers and faculty experienced in CHD. Despite this, the echocardiograms obtained were thought to show normal origins of both left and right coronary arteries. Similarly, the CT studies were performed by radiologists with significant CHD experience. Although both the CT studies obtained suggested an abnormal course of the coronary arteries, they did not accurately identify the diagnoses.

The presentation of left main coronary artery atresia varies based on age. The symptomatic infantile form presents with failure to thrive and myocardial infarction, while older children and adolescents present with syncope and tachyarrhythmias.^{Reference Musiani, Cernigliaro, Sansa, Maselli and De Gasperis4,Reference Elian, Hegesh and Agranat7} A review of literature reveals numerous other case studies with delayed diagnosis of left main coronary artery atresia.^{Reference Yajima, Toda, Nishi, Yoshioka, Nakamura, Miyagawa, Yoshikawa, Fukushima and Sawa3-Reference Furuyama, Yoshikazu, Nakajima, Okajima, Okajima, Nakayama, Sawada and Ohta6} Amaral et al described two paediatric cases confirmed via coronary angiography or direct inspection in the operating room, despite normal coronaries on echocardiogram. Shah et al described a paediatric case with recurrent exertional syncopal episodes, an echocardiogram with prominent right coronary artery (otherwise normal), normal exercise testing and diagnosis confirmed by cardiac catheterisation.^{Reference Shah, Johnston and Cohen8}

These papers and our experience suggest that in patients presenting with sudden death or ventricular fibrillation, a high index of suspicion for coronary anomalies (including congenital left main coronary artery atresia) is paramount for efficient and accurate diagnosis.

In conclusion, in young patients with unexplained ventricular fibrillation, coronary occlusion must be considered as a possible cause. Echocardiography and CT may falsely reassure providers of normal coronary anatomy. We recommend performing coronary angiography in all patients with suspicion of coronary artery anomalies, especially if they present with sudden death or ventricular fibrillation. Our cases demonstrate the importance of coronary angiography to definitively rule out total occlusion of the left main coronary artery.