Discussion
We present a rare case with anomalous left main (LM) coronary artery arising from the opposite side with a superadded severe atherosclerotic disease involving both the normal and the anomalous arteries. Based on its course, anomalous left main arising from the opposite side had been classified as follows: A. Passing anterior to the aorta in the right ventricular outflow, B. Inter-arterial course (between the aorta and the pulmonary artery), C. Courses through the crista of the septum, D. Passing posterior to the aortic root (2, 3). Based on this classification, our case had combined anomalous origin of the LM coronary artery and abnormal course including type B and D.
Coronary artery anomalies are very rare congenital cardiac disorders, with variable incidence reported in literature and wide range of clinical presentation (1). LM arising from the opposite sinus of Valsalva or the proximal segment of the right coronary artery is an extremely rare coronary anomaly with a reported incidence of 0.09 to 0.11% in the general population (4). Majority of the anomalous origin of the coronary arteries are benign, however clinical presentation may vary according to the left main course, and may presents present with sudden death, arrhythmias or myocardial ischemia (3). Pathophysiology behind this can be explained as follows (5): The slit like orifice of the anomalous coronary artery may lead to loss of blood flow, possible compression during its course especially in the interarterial course, or it may be vulnerable to the process of atherosclerosis as in our case.
The incidence of atherosclerotic disease involvement in anomalous coronary arteries is controversial and ranging from 1.7% to 72.2% according to previously published reports (1). This variation in the incidence could be related to the patient characteristics included or the imaging modality utilized for diagnosis (1). Certain reports demonstrated that anomalous coronary arteries are comparable to normal coronaries in the potential for developing atherosclerosis (6). Few studies have reported that anomalous left coronary arteries arising from the opposite side as in our case are more vulnerable to develop atherosclerosis (7). A superadded significant atherosclerotic disease in the anomalous coronary arteries poses a high therapeutic challenge due to the difficulties in utilizing percutaneous coronary interventions taking in consideration the complex anatomical findings and the increased fluoroscopic times.
Surgical intervention is recommended once diagnosis is established especially for those patients with the interarterial course (2). Modalities of surgical intervention included: Unroofing of the proximal left main intramural course, Ostial re-implantation, Coronary artery bypass grafting and pulmonary artery translocation(2). The complex anomalous anatomy with superadded atherosclerotic severe atherosclerotic disease involving the normal and anomalous coronary arteries in our case scenario made us reach an agreement to choose coronary artery bypass grafting as a valid choice.
To conclude, despite the fact that anomalous origin of the left main coronary artery is a rare congenital anomaly, it should be kept in mind as a possible diagnosis. Coronary computed tomography is an excellent diagnostic modality to clarify its course.