Anomalous left coronary artery off the pulmonary artery

An anomalous left coronary artery off the pulmonary artery (ALCAPA) also known as the Bland-White-Garland syndrome (BWG) is a rare congenital coronary artery anomaly and is considered one of the most serious of such anomalies ⁴.

Epidemiology

This abnormality only accounts for 0.25 - 0.5 % of all congenital cardiac anomalies ³.

Associations

It is often an isolated anomaly but can be associated with other cardiac anomalies in ~ 5% of cases. These include ³

• atrial septal defect (ASD)
• ventricular septal defect (VSD)
• coarctation of the aorta

Clinical presentation

Typically ALCAPA presents when infants are 1 - 2 months old (see pathophysiology below). 

Pathophysiology

ALCAPA results when the left main coronary artery arises from the pulmonary trunk instead of the aorta. Function of the left main coronary arterial territory then often requires extensive collateral formation from the right coronary artery.

In the first month of life, physiologic pulmonary hypertension tends to preserve antegrade blood flow within the left coronary artery, and infants usually remain asymptomatic. 

As pulmonary pressures drop, left-to-right shunting from the higher pressure left coronary arterial system to the lower pressure pulmonary arterial system begins to occur, and patients become symptomatic. 

Radiographic features

CT

CTA allows direct visualisation of anomalous left main coronary arterial origin from the posterior aspect of the pulmonary artery. The right coronary artery may be unusually dilated and tortuous with evidence of collateral formation. Intercoronary collateral arteries along the external surface of the heart or within the interventricular septum may also be seen. 

Treatment and prognosis

Prognosis depends significantly of extent of collateral formation, however most infant die within the 1^st year of birth ⁴. Death is usually due to circulatory insufficiency from left ventricular dysfunction or mitral valve incompetence, myocardial infarction, or life-threatening cardiac dysrhythmias ³.

Early surgical repair is potentially curative.