Maggie Nguyen, RDCS (FE, PE)
ALCAPA is a rare congenital abnormality that affects 1 of every 300,000 live births in which the left coronary artery arises from the pulmonary artery, most commonly from the left posterior facing sinus. It usually manifests as an isolated defect, but in 5% of cases it may be associated with other cardiac anomalies such as atrial septal defect, ventricular septal defect, and aortic coarctation. The coronary circulation is a collection of blood vessels which provide oxygen-rich blood to the myocardium. These arteries, when healthy, are capable of autoregulation to maintain coronary blood flow at levels appropriate to the needs of the heart musle.
The pulmonary artery conversely contains oxygen-poor blood at pressures that rapidly decrease after birth. In ALCAPA, once the pulmonary vascular resistance decreases, the left ventricular myocardium is supplied by oxygen-poor blood at low pressures from the pulmonary artery. ALCAPA results in the “coronary steal” phenomenon, in which a left-to-right shunt leads to abnormal left ventricular perfusion resulting in compromised perfusion to the myocardium. ALCAPA is one of the most common causes of myocardial ischemia and infarction in children. If left untreated, up to 90% of patients with ALCAPA syndrome die within the 1st year of life. Eventually, this results in myocardial ischemia which can lead to heart muscle death (infarction). Typical echocardiographic findings in ALCAPA include a dilated, dysfunctional left ventricle. In addition, the mitral valve papillary muscles often appear echobright secondary to infarction of coronary blood flow to this apparatus which can affect the competency of the mitral valve and cause mitral regurgitation. Poor visualization of the origin of the left coronary artery, a dilated right coronary artery, isolated severe mitral regurgitation, or echobright endocardium and papillary muscles should increase your suspicion for this anomaly.
Direct reimplantation of the origin of the left coronary artery into the aorta, with a button of a pulmonary artery around the origin, has been proven successful and is considered the standard in many centers. An alternative approach is the Takeuchi procedure, in which an aortopulmonary window is created and then a tunnel fashioned that directs blood from the aorta to the left coronary ostium