Anomalous Origin of the Left Coronary Artery From the Main Pulmonary Artery in Adults
Coronary Collateralization at Its Best
Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA, or Bland-White-Garland syndrome) occurs once per 300 000 live births, usually as an isolated cardiac lesion. In fetal life, this anomaly is well tolerated because pulmonary pressure equals systemic pressure and oxygen content is identical in the main pulmonary artery (PA) and aorta. Therefore, coronary collateral growth is not especially promoted before birth. After birth, as soon as pulmonary pressure and saturation fall, left ventricular (LV) oxygen demands no longer can be accommodated by the left coronary artery (LCA), and ALCAPA leads to myocardial ischemia. Subendocardial ischemia can occur even in the presence of well-established coronary collateral vessels because of preferential coronary blood flow into the low-pressure pulmonary circulation instead of high-resistance myocardial blood vessel (ie, coronary steal). It is not surprising that up to 9 of 10 children with ALCAPA will die within the first year of life without surgical intervention. The asymptomatic individual presenting in adulthood is rare and must have a well-developed coronary collateral circulation with retrograde perfusion of the LV from the right coronary artery (RCA). Some of these patients have an ostial stenosis of the LCA, limiting the steal and increasing myocardial perfusion pressure. Even if asymptomatic, uncorrected adult ALCAPA patients are at risk for sudden death, which classically is precipitated by exercise.
We recently examined a 38-year-old asymptomatic male undergoing cardiac evaluation for a continuous heart murmur along the left sternal border. His ECG showed sinus rhythm and was suggestive of a previous anteroseptal myocardial infarction. Transthoracic echocardiography demonstrated a large coronary artery arising from the right aortic sinus (Figure 1), turbulent diastolic flow within the interventricular septum and right ventricular (RV) apex, and take-off of a vessel from the posteromedial aspect of the PA (Figure 2). LV systolic function was mildly reduced with septal hypokinesis and apical akinesis. Cardiac MRI confirmed ALCAPA (Figures 3 and 4⇓) by demonstrating the pulmonary origin of the LCA with retrograde flow in the left anterior descending artery (LAD). The turbulent diastolic flow seen in the interventricular septum on echocardiography was the result of large septal collateral vessels. Delayed gadolinium-enhanced imaging demonstrated a viable myocardium with only subendocardial hyperenhancement in the LAD and circumflex territories (Figure 5). Right coronary angiography revealed a dilated and tortuous vessel with impressive right-to-left collateralization (Figure 6).
The patient currently is awaiting surgical repair to establish 2-coronary myocardial perfusion.