Unroofing of Left Main Coronary Artery With Trans-Septal Course

Trans-Septal/Intraconal Left Main Coronary Artery (LMCA) is a rare form of coronary arterial anomalies. It has been linked to increase risk of myocardial ischemia and sudden death. In this anomaly, the proximal portion of LMCA is surrounded by the myocardium of the interventricular septum. Usually there is a single anterior coronary artery that gives origin to both right and left coronaries. Repair of such anomaly has been challenging.

We present a 12-year-old boy who presented to the emergency room with exertional chest pain. Initial evaluation with electrocardiogram, echocardiography and stress test did not show evidence of ischemia and otherwise structurally normal heart. Computed tomography scan shows single anterior coronary artery that divides into both right and left branches. The left main then dips towards the interventricular septum and travels for a distance below the level of the pulmonary valve prior to exiting to the epicardial surface and bifurcating.

The procedure was performed through a median sternotomy and mild hypothermic cardiopulmonary bypass. After cardioplegic arrest, the main pulmonary artery was transected proximal to its bifurcation and retracted caudally. A limited aortotomy was performed and a probe is placed through the left main artery. The pulmonary root in these cases require extensive mobilization similar to the Ross procedure. Using a combination of Potts scissors and electrocautery at low settings, unroofing is performed guided by the coronary probe. The second part of the procedure require anterior translocation of the right main branch pulmonary artery to maintain the inter-arterial space and avoid recurrence of the compression by the pulmonary root.

The postoperative course was uneventful and the patient was discharged on the fourth postoperative day.

In conclusion, trans-septal (intraconal) LMCA is a rare anomaly that is linked to myocardial ischemia and sudden death. It is important to understand the 3-dimensional location of the anomalous LMCA to facilitate the unroofing procedure. Coronary artery bypass grafting is not advised in these cases and is committed to fail. The two main principles of the procedure include (1) Unroofing, and (2) anterior Translocation of the right main branch pulmonary artery.

References

1. Said SM, Cetta F. Pulmonary Root Mobilization and Modified Lecompte Maneuver for Transseptal Course of the Left Main Coronary Artery. World J Pediatr Congenit Heart Surg. 2020 Nov;11(6):792-796
2. Mainwaring RD, Hanley FL. Surgical treatment of anomalous left main coronary artery with an intraconal course. Congenit Heart Dis. 2019 Jul;14(4):504-510

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