Pediatric Cardiovascular Radiology

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What are some of the most common types of congenital heart disease (CHD) in order of frequency (most common to least common)?

Bicuspid aortic valve, ventricular septal defect (VSD), atrial septal defect (ASD), patent ductus arteriosus (PDA), tetralogy of Fallot, coarctation of the aorta, and transposition of the great vessels.

2

How does assessment of pulmonary blood flow aid in the diagnosis of cyanotic disease?

The first consideration in diagnosing CHD is whether the infant is clinically cyanotic. Cyanosis may be secondary to admixture of oxygenated and deoxygenated blood, which can appear as increased blood flow to the heart with enlargement of the pulmonary arteries, or may be secondary to blood shunted away from the lungs, which would appear as decreased blood flow with small to absent pulmonary arteries. Assessment of blood flow includes looking for shunt vessels at the periphery of the lung fields or behind the liver shadow.

3

Which types of CHD appear with cyanosis and increased pulmonary blood flow?

These conditions include total anomalous pulmonary venous return (TAPVR), truncus arteriosus, transposition of the great vessels (d-TGV), tricuspid atresia, and single ventricle. Hypoplastic left heart syndrome (HLHS) may also appear with congestive heart failure (CHF) and cyanosis.

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How is HLHS corrected surgically?

In HLHS, the left-sided cardiac structures (usually the left ventricle and aortic root) are hypoplastic. The right ventricle is surgically recruited to become the systemic pumping ventricle. A neoaortic root is fashioned from the pulmonary outflow track and anastomosed to the aortic arch, an atrial septectomy is performed, and a shunt is temporarily created between the subclavian artery and pulmonary arteries (Norwood procedure). Systemic venous return is subsequently diverted directly to the branch pulmonary arteries through a Glenn procedure (superior vena cava to pulmonary arteries) and a Fontan completion (inferior vena cava to pulmonary arteries.)

5

What is congenitally corrected transposition of the great vessels, and why is it a problem?

In congenitally corrected transposition of the great vessels (l-TGV), there is an abnormal (L) ventricular loop, but there is also an abnormal (−150 degree) rotation of the great vessels. This leads to the following circuits: (1) systemic venous return-right atrium-left ventricle-pulmonary artery and (2) pulmonary venous return-left atrium-right ventricle-aorta. Although systemic and pulmonary blood flow circuits are “corrected” congenitally, this places abnormal stress on the right ventricle, which must pump blood against systemic pressures.

6

What are the 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.

7

What is the role of the radiologist in assessing suspected CHD?

Although magnetic resonance imaging (MRI) or computed tomography (CT) examination of the heart may be used to assess cardiac chamber size and position, wall thickness, presence of intracardiac shunts, and position of the coronary arteries, the initial role of the radiologist is to evaluate the chest radiograph and to provide an ordered, logical differential diagnosis. It is usually impossible to give a precise diagnosis in these cases initially.

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