Rare origin of left main coronary artery from non-coronary sinus with aortic coarctation

Abstract

Anomalous origin of left main coronary artery from non-coronary sinus (LCANCS) is an extremely rare anomaly. Aortic coarctation in association with LCANCS has not been previously described in literature.

Background

With increasing use of multislice CT coronary angiography (CTCA), coronary artery anomalies are being identified more frequently. Here, we describe a rarely reported anomaly of coronary artery origin.

Case presentation

A previously asymptomatic 54-year-old man presented to the hospital with atypical chest pain. On echocardiography, he was diagnosed with possible aortic coarctation. Preoperative evaluation by CTCA was done for better characterisation of the coarctation and to rule out coronary artery disease (CAD). Incidentally, the left main coronary artery (LMCA) was found to be originating from the non-coronary sinus with an acute angle take-off suggesting possible intramural course of the ostioproximal LMCA (figure 1A). The CT also revealed severe juxtaductal coarctation with presence of multiple collaterals (figure 1B,C). No other significant CAD was noted.

Figure 1.

(A) Oblique axial image showing the LM (arrow) arising from the NCS (immediately adjacent to the commissure). (B) Volume rendered image showing postductal aortic coarctation (arrow) with RCA originating from the RCS and LM splayed around the aortic root after originating from the non-coronary sinus. (C) Volume rendered image showing LM clearly originating from the NCS. LCS, left coronary sinus; LM, left main coronary artery; LAD, left anterior descending artery; LCx, left circumflex coronary artery; NCS, non-coronary sinus; RCA, right coronary artery; RCS, right coronary sinus.

Differential diagnosis

The differential diagnosis in this case would include commissural origin of the LM, in which the coronary artery originates from the commissure between the aortic valve cusps.

Outcome and follow-up

The patient was referred for surgical correction of the coarctation with concurrent unroofing of the LMCA.

Discussion

Epicardial coronary arteries usually arise from the two-pulmonary facing aortic sinuses. Anomalous origin of coronary artery can occur, with incidence varying between 1% and 2%.¹ Left main coronary artery from non-coronary sinus (LCANCS) is a rare anomaly with an incidence of 0.0008% to 0.012%.^{1 2} Right coronary artery can similarly arise anomalously from NCS with an incidence of 0.003%.² Though originally thought to be a benign condition, LCANCS has been associated with sudden cardiac death (SCD) or fatal arrhythmia. Anwar et al³ first described the coronary intramural course in LCANCS, as suspected by CTCA which was further confirmed during surgical exposure. This intramural course has been hypothesised to increase the chances of fatal arrhythmias and SCD because of which aggressive management by a surgical unroofing procedure is advocated.³ After the advent of multidetector CTCA, there has been increase in the detection rate of anomalous coronary arteries.⁴ Besides description of the anomalous origin, the course of the coronary artery should be studied meticulously and reported as it helps in deciding the further management. Along with intramural course, other factors which can contribute to the increased risk of ischaemia and SCD are acute take-off angle (<45° between proximal LCA and aortic wall) or ostial valve like ridges (covering >50% of ostial luminal area).⁵ The authors also suggested that with increasing aortic dilatation, further compromise of the coronary artery can occur leading to acute infarction. Only few case reports of LCANCS detected by CTCA have been previously described in literature.^{3 6 7} This is the first case to the best of our knowledge to report a LCANCS coexisting with coarctation.

Learning points.

• Though originally described as a benign condition, left main coronary artery from non-coronary sinus is a rare anomaly which may sometimes be associated with sudden cardiac death and fatal arrhythmias.

• Besides its origin, CT coronary angiography (CTCA) can suggest possible intramural course of the artery when its take-off angle is acute, and this may influence the management strategy.

• CTCA enables identification and characterisation of this disease which may be difficult to detect by CA.