Most common acyanotic types of CHD
Acyanosis implies a left-to-right shunt, and the most common causes include ASD, VSD, PDA, and endocardial cushion defects. These typically cause enlargement of specific chambers in the heart as a result of decompression of some chambers and overload in others.
A VSD, due to a communication between the right ventricle and left ventricle, results in an enlarged right ventricle, main pulmonary artery, and left atrium, sometimes with left ventricular dilation as well.
An ASD, due to a communication between the right atrium and left atrium, results in an enlarged right atrium, right ventricle, and main pulmonary artery, with a normal-sized left atrium as blood is shunted away from it.
A PDA, due to persistent patency of the ductus arteriosus between the aorta and pulmonary artery, results in an enlarged main pulmonary artery, left atrium, and left ventricle.
An endocardial cushion defect, due to defects in the atrial septum, ventricular septum, and one or more atrioventricular valves, results in an enlarged right atrium, right ventricle, and pulmonary artery, along with variable enlargement of the left atrium and left ventricle. This is the most common cardiac anomaly in patients with Down syndrome.