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].