Discussion
LMCAA is a quite rare condition with unclear etiology. In LMCAA, the left coronary system receives blood only by collateral arteries from the RCA. Thus, the heart may eventually be unable to cope with collateral circulations and develop myocardial ischemia. Patients mostly present with nonspecific symptoms depending on their age group and the formation of collateral vessels from the right coronary artery to the left coronary artery. Adult patients usually present with angina pectoris at an advanced age when collateral flow cannot keep pace with myocardial demands. Children and adolescents often present with chest pain, dyspnea, syncope and tachyarrhythmia, and sudden cardiac death [2, 3]. Infants mostly present with growth retardation and myocardial infarction [2]. Catastrophic situations like sudden cardiac arrest, low cardiac output, and cardiomyopathy, as seen in our case, can also be the first symptoms of infants with LMCAA. [5, 6] Since these symptoms are not specific to LMCAA, the clinical diagnosis might be neglected. Thus, other coronary anomalies should be excluded to reach a correct diagnosis. As stated in a retrospective study done by Yildiz et al., LMCA was the most common anomalous vessel [1]. Separate origins of LAD and CX from the left coronary sinus of Valsalva were the most seen anomaly and should be excluded in patients presenting with symptoms of myocardial infarction. ALCAPA is one situation that LMCAA can be confused with and should be differentiated from [2,7].
Although congenital atresia of the left main coronary artery usually occurs as an isolated cardiac lesion, concomitant anomalies including bicuspid aorta, supravalvular aortic stenosis, right coronary ostial stenosis, pulmonary stenosis, ventricular septal defect, and mitral valve prolapsus secondary to myocardial ischemia can be seen [4, 8, 9].
The diagnosis of LMCAA can be done by coronary angiographic findings, which usually show no left coronary ostium and left coronary artery filled in a retrograde manner via the RCA instead of antegrade blood flow. In recent years, MDCT has also played an essential role in diagnosing LMCAA in older children and adults and can be used in patients suspected of congenital coronary artery abnormalities [3, 10]. According to some researchers, MDCT provides more precise details in a less invasive way than coronary angiography and is thus recommended for evaluation of congenital coronary abnormalities. [11] MDCT not only defines the anatomic course and the ostium shape, but also has less complications as coronary spasm than conventional coronary angiography. However, there is no reliable research reporting the use of MDCT in infants with coronary anomalies. [9]
The prognosis of LMCAA is poor [2]. Due to the symptomatic nature of LMCAA and the risk of sudden cardiac death, patients in the pediatric population with LMCAA should undergo surgical intervention to restore the antegrade flow to the left coronary system. Various surgical interventions have been described and coronary artery bypass grafting using the internal mammary artery or saphenous vein has been identified as the treatment of choice, regardless of the caliber of left sided vessels [4, 8, 12]. A LIMA graft for LMCAA appears to be a reasonable early interventional approach with successful results 1 year postoperatively. Nevertheless, due to the rarity of this disease, long-term postoperative outcomes have not been reported yet [2, 4, 5, 8, 9, 11]. Alternative to bypass grafting, direct surgical reimplantation or reconstruction of the left main coronary artery using azygos vein have been described to provide the shortest and most efficient way for blood to the myocardium. [6, 12, 13]. The advantages they offer relative to bypass grafting are prevention of the occlusion of main trunk, provision of the antegrade flow and avoidance of competitive flow. After the application of these techniques, reoperative surgery can be easily performed. However, application of this technique for LMCAA is not common and the long-term outcomes of the surviving patients were unknown [6, 12].