Which are the causes of Major aortopulmonary collateral arteries (MAPCAs)?

Major aortopulmonary collateral arteries (MAPCAs) are abnormal blood vessels that develop in the lungs as a result of certain congenital heart defects. These collateral arteries serve as alternative pathways for blood flow between the aorta and the pulmonary arteries, bypassing the normal route through the heart. The presence of MAPCAs can lead to various complications and affect the overall functioning of the cardiovascular system.

There are several causes that contribute to the development of MAPCAs:

1. Pulmonary Atresia: This is a congenital heart defect where the pulmonary valve is either missing or abnormally developed. As a result, blood flow from the right ventricle to the pulmonary arteries is obstructed. In response, the body tries to compensate by forming collateral arteries to supply blood to the lungs.

2. Tetralogy of Fallot: This is a complex heart defect characterized by four abnormalities, including a ventricular septal defect (VSD), pulmonary stenosis, an overriding aorta, and right ventricular hypertrophy. In some cases, the pulmonary stenosis can be severe, causing reduced blood flow to the lungs. The body compensates by developing MAPCAs to ensure adequate oxygenation of the blood.

3. Double Outlet Right Ventricle (DORV): In DORV, both the pulmonary artery and the aorta arise from the right ventricle instead of their normal positions. This leads to mixing of oxygenated and deoxygenated blood. To improve oxygenation, collateral arteries may form to supply blood directly to the lungs.

4. Transposition of the Great Arteries (TGA): In TGA, the positions of the pulmonary artery and the aorta are switched. As a result, oxygenated blood from the lungs is pumped back to the lungs instead of being circulated to the body. The body compensates by developing MAPCAs to allow some oxygenated blood to reach the body tissues.

5. Other Congenital Heart Defects: MAPCAs can also occur in association with other heart defects, such as truncus arteriosus, single ventricle defects, or pulmonary atresia with intact ventricular septum. These defects disrupt the normal blood flow patterns, leading to the formation of collateral arteries.

It is important to diagnose and manage MAPCAs appropriately as they can cause complications such as pulmonary hypertension, heart failure, and reduced oxygenation. Treatment options may include surgical interventions to redirect blood flow, repair or replace abnormal valves, or close off abnormal vessels.