Discussion

Anomalous origin of a coronary artery from the contralateral coronary sinus of Valsalva is associated with increased risk of sudden death and cardiac morbidity.Reference Benson ^{1 ,} Reference Davis, Cecchin and Jones ² Sudden death, especially in young athletic individuals, is frequently the initial manifestation of these abnormalities.Reference Liberthson ^{5 ,} Reference Chaitman, Lespereanc and Salteil ⁶ Sudden death is thought to be due to a reduction in blood flow in the anomalous vessel, resulting in myocardial ischaemia and/or infarction.Reference Benge, Martins and Funk ^{7 ,} Reference Frescura, Basso and Thiene ⁸ The exact pathophysiology of this decreased blood flow is not fully understood. The mechanism has been described as a tangential acutely angulated origin associated with a slit-like orifice that may be further compressed by aortic dilation during exercise.Reference Frescura, Basso and Thiene ⁸ We report an extremely rare case of the anomalous right coronary artery arising from the posterior sinus diagnosed by MRI. In our patient, the proximal right coronary artery is widely patent and there is no interarterial course. Although an intramural course cannot be directly assessed or ruled out with cross-sectional non-invasive imaging, in this case the absence of an acutely angulated proximal right coronary artery suggests there is no intramural course. Furthermore, the patient underwent exercise stress testing with nuclear perfusion, which was normal without evidence of ischaemic changes or perfusion defects. Similarly, MRI shows no evidence of myocardial scarring on delayed gadolinium enhancement imaging. In reviewing the literature, there are few reports of this rare anomaly. Vlodaver et alReference Vlodaver, Neufeld and Edwards ⁹ and Virmani et alReference Virmani, Rogan and Cheitlin ¹⁰ report right coronary artery from the posterior sinus associated with significant atherosclerotic disease in two adults aged 72 and 59 years, respectively. Yamanaka and Hobbs’Reference Yamanaka and Hobbs ¹¹ report of identified coronary anomalies in a large catheter angiography series finds four patients with right coronary artery from the posterior sinus, without clinical manifestations or perfusion abnormalities, and considers this anomaly benign until proven otherwise. RobertsReference Roberts ¹² reports the one case of right coronary artery he has observed from the posterior sinus in a 19-year-old with a quadricuspid pulmonic valve and cardiomegaly, who suddenly died while playing basketball. Roberts states that, although the cause of sudden death was unclear, it seemed unlikey because of the coronary anomaly, given the significant cardiomegaly. For these reasons, in our patient, the coronary anomaly was considered an incidental finding and the patient was permitted to exercise. Our findings on cardiac MRI support that the anomalous right coronary artery from the posterior sinus should be considered a distinct clinical entity of the anomalous right coronary artery from the left sinus of Valsalva.