Pedriatic radiology Cardiovascular system
Imaging plays a critical role in the diagnosis and appropriate therapy of cardiovascular disease in the pediatric patient. The incidence of cardiovascular malformations in children is less than l %. In pediatric patients requiring surgery or treatment, diagnosis is based on invasive techniques in 60% and non-invasive methods, primarily echocardiography, in 40%.
Diagnostic evaluation of general abnormalities of the heart and great vessels is based on accurate clinical, laboratory, andradiologic observations. Pertinent clinical information includes age, sex, onset of symptoms, presence of cyanosis, type of symptoms, blood pressure, presence or absence of peripheral pulses, and type of murmur. Important laboratory data includes hemoglobin, hematocrit, electrolytes, blood urea nitrogen, creatinine, calcium, and glucose. The electrocardiogram provides information about specific chamber size, electrophysiologic activity, conduction, and cardiac axis. Echocardiography demonstrates anatomy and dynamic function. The chest radiograph remains a valuable and readily available imaging modality. Although the chest radiograph is a static image of the heart and lungs, it provides important physiologic as well as anatomic information. Nuclear scintigraphy allows imaging and quantification of certain pulmonary vascular abnormalities, shunts, and myocardial dysfunctions. Cardiac catheterization provides information regarding pressure and oxygenation within select chambers and great vessels. Angiocardiography demonstrates the anatomy as well as function of individual cardiac chambers and great vessels. Magnetic resonance imaging demonstrates cardiac anatomy without the use of ionizing radiation.
Pulmonary vascularity, as assessed from the chest radiograph, forms the basis for the classification of congenital heart disease. It must be remembered that an increase in pulmonary vessel size is not seen until a left-to-right shunt is at least 2: 1. Decreased pulmonary vascularity is more unusual in patients with congenital cardiovascular malformations than normal pulmonary blood flow or increased vascularity; decreased pulmonary vascularity is associated with congenital cyanosis.
Congenital heart disease (CHD) is classified by the presence or absence of cyanosis with the radiologic appearance of the pulmonary vascularity. This functional classification forms the basis for differential diagnosis of CHD in children.
Acyanotic CHD with normal or increased pulmonary blood flow
Ventricular septal defect (VSD)
Ventricular septal defect (VSD) is second only to bicuspid aortic valve in frequency among congenital cardiovascular anomalies. VSD may be an isolated anomaly or part of a more complex malformation. VSDs may involve the membranous or perimembranous portion of the septum (70-80%), the muscular septum (10%), conal region (5%), or posterior septum (5-10%) as part of atrioventricular canal defects.
The hemodynamics of VSD are determined by the size of the defect and the pressure difference between the right and left ventricle. In patients with small or moderate VSDs, there is shunting of blood from the high-pressure left ventricle to the low-pressure right ventricle and low resistance lungs. Large shunts can produce pulmonary arteriolar changes that increase pulmonary vascular resistance. This may produce fixed pulmonary hypertension (Eisenmenger physiology) with clinical cyanosis.
The chest radiograph in a patient with a small VSD (less than 2: 1 or 50% shunt) is normal. It must be remembered that a normal chest radiograph in no way excludes a small left-to-right shunt. In patients with moderate to large VSDs, there is cardiac enlargement, increase in the main pulmonary artery segment, and an increase in pulmonary vascularity (Fig. 20). Due to volume overload, the left atrium is usually enlarged; this is best seen on the lateral view with posterior displacement of the left mainstem bronchus and/or impression on the barium-filled esophagus.
Atrial septal defect
Atrial septal defect (ASD) is relatively common, often occurs as an isolated lesion, and is more common in females. Due to a defect in the atrial septum, blood passes from the left atrium to the right atrium and into the right heart and pulmonary vascular bed. The left atrium is not enlarged
 a
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Figure 20.
Ventricular septal defect.
a) The heart is moderately enlarged and there is shunt vascularity. The distinct vessel margins indicate no interstitial edema. Cardiac catheterization showed a large shunt (2.5: 1) at the ventricular level.
b) There is posterior displacement of the esophagus (arrows) by left atrial enlargement.
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 b
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since blood is immediately shunted left-to-right across the ASD.
In patients with small ASDs and in patients of a young age, the heart size and pulmonary blood flow are usually normal. In older children with moderate-sized ASDs, the chest radiograph is highly suggestive of the diagnosis. Pulmonary vascularity is increased and of the shunt type. There is right heart enlargement, a normal left atrium, and a normal-sized aorta (Fig. 21).
In all patients with suspected ASD, the upper lobe pulmonary veins and upper mediastinum should be carefully evaluated. There may be anomalous right upper pulmonary venous drainage into the right atrium with associated sinus venosus ASD. There is also association between partial anomalous pulmonary venous connection in the left upper mediastinum with an ostium secundum ASD.
 a | Figure 21.Atrial septal defect.
a) There is shunt vascularity. The heart is enlarged in its transverse diameter and there is prominence of the main pulmonary artery segment.
b) Retrosternal density is due to right ventricular enlargement. There is no evidence of left atrial enlargement. |
 b |
Patent ductus arteriosus (PDA)
During fetal life, the ductus arteriosus shunts blood from the pulmonary artery to the aorta; this allows blood to bypass the non-aerated lungs. Functional closure usually occurs by 24 hours of age. Prematurity and hypoxia can maintain patency of the ductus arteriosus. PDA produces a left-to-right shunt with a characteristic machinery murmur.
There are two distinct groups of patients with PDA. The majority are older children with a murmur. Most patients have a small PDA with a completely normal chest radiograph. Moderate to large PDAs show increased vascularity of the shunt type. The vessels and chambers through which blood circulates are enlarged. Therefore, there is enlargement of the main pulmonary artery, pulmonary vessels, left atrium, left ventricle, and transverse portion of the aortic arch.
In premature infants, the diagnosis of PDA is best confirmed by serial films. There is frequently underlying pulmonary disease. Slight increase in cardiac size and hazy, ill-defined pulmonary densities due to pulmonary edema in a premature infant suggest a PDA. Doppler sonography is important in diagnosing a PDA in infants. Angiographic studies are rarely performed. Premature infants usually require surgical closure of the PDA.
Atrioventricular can al defect (AVC)
Atrioventricular cardiac defect (AVC) (atrioventricular communis, endocardial cushion defect) is due to abnormalities of growth and fusion of the endocardial cushions. This causes a defect in the formation of the upper ventricular septum, the lower portion of the atrial septum, and the septal leaflets of both mitral and tricuspid valves. The spectrum of AVC includes ostium primum defect and atrioventricular canal defects. Physiologically, there are shunts at both the atrial and ventricular level as well as frequently insufficiency of both mitral and tricuspid valves.
With an ostium primum defect, the heart may be normal to only slightly enlarged and the pulmonary vascularity is minimally increased. With the complete AVC, the heart is moderately to markedly enlarged. The right atrium is frequently enlarged. The pulmonary artery is prominent and the pulmonary vascularity is increased. The left atrium is normal to markedly enlarged. There is frequently heart failure in the newborn period.
Patients with trisomy 21 (Down syndrome) account for 40% of all patients with the complete type of AVC; conversely, 33 % of patients with Down syndrome have AVC.
Coarctation of the aorta
Coarctation is a congenital narrowing of the aorta. The localized or juxtaductal type is most common; the area of coarctation is located just beyond the origin of the left subclavian artery at the level of the ductus arteriosus and is short as well as discrete. The diffuse type is also known as infantile or preductal type; there is a long segment of narrowed aorta that extends from just distal to the brachiocephalic artery to the level of the ductus arteriosus.
 | Figure 22.Coarctation of the aorta. Coned-down view shows inferior rib notching (arrows) due to bony erosion by enlarged intercostal arteries. |
 | Figure 23.Discrete coarctation of the aorta. Sagittal MRI demonstrates aortic narrowing just distal to the origin of the left subclavian artery. |
 | Figure 24.Tetralogy of Fallot. A neonate with cyanosis. The heart is not enlarged in its transverse diameter. There is elevation of the cardiac apex, concavity of the main pulmonary artery segment, and a right aortic arch. The pulmonary vascularity is decreased. |
lntracardiac defects, most commonly VSD, are present in 50% of patients with the
diffuse type of coarctation. PDA is almost always present with this type of
lesion. The
diffuse type of coarctation usually presents in the neonate or young infant with congestive heart failure and bounding pulses in the upper
extremities.
The localized type of coarctation is usually diagnosed during late childhood; these patients are frequently asymptomatic. On physical examination, the patients may have upper extremity hypertension. The heart is usually not enlarged in its transverse diameter. However, there is frequently rounding of the left ventricular contour on the AP film as well as left ventricular enlargement on the lateral view. There is dilatation of the aorta and a notch in the descending aorta may be identified. Rib notching may be present due to pressure erosion caused by dilated intercostal arteries (Fig. 22). The pulmonary vascularity is normal unless left ventricular failure has developed. MRI has replaced cardiac catheterization and angiocardiography in older patients with coarctation. The exact size and extent of the coarctation is demonstrated, and the degree of collateral circulation is assessed (Fig. 23).
Aortic stenosis and valvular pulmonary stenosis
Most children and adolescents with aortic stenosis are asymptomatic. Congenital valvular pulmonary stenosis is a common abnormality that may be found as an isolated lesion or in combination with other abnormalities. These patients are frequently also asymptomatic despite the presence of a loud systolic murmur.
Considerable aortic valvular stenosis may be present with a normal appearing chest radiograph. The lateral film frequently demonstrates left ventricular enlargement. There may be dilatation of the ascending aorta on the AP view due to poststenotic dilatation. Dilatation of the ascending aorta is not present in subvalvular or supravalvular aortic stenosis.
The chest radiograph in mild valvular pulmonic stenosis is completely normal. With moderate and severe pulmonic stenosis, there is dilatation of the main pulmonary artery due to the high velocity of blood ejected through the small pulmonary valve orifice. This dilatation may extend to the left pulmonary artery.
Cyanotic CHD with decreased pulmonary blood flow
Tetralogy of Fallot
The four components of tetralogy of Fallot are right ventricular outflow tract obstruction, sub-aortic large ventricular septal defect, overriding of the aorta, and right ventricular hypertrophy. Cyanosis is usually present.
X-ray features are those of a normal-sized heart with abnormal shape. The vascular pedicle is narrow and there is uplifting of the ventricular apex due to rotation of the heart secondary to right ventricular enlargement. There is concavity in the region of the main pulmonary artery segment. This leads to a characteristic boot-shaped heart (Fig. 24). The pulmonary vascularity is usually decreased. A right-sided aortic arch is present in 25 % of patients with classic tetralogy of Fallot and 50% of patients with tetralogy with pulmonary atresia (pseudotruncus arteriosus).
Echocardiography is diagnostic. Angiography is frequently performed prior to surgery. MRI is becoming increasingly important in demonstrating the main, right, and left pulmonary arteries.
Tetralogy of Fallot is frequently corrected in two surgical stages. Initially, a shunt is created between the aorta and the pulmonary circulation. At 1-2 years of age, definitive correction is performed. This includes closing the VSD, removing infundibular muscle causing obstruction, and inserting a patch or conduit to increase flow from the right ventricle to the main pulmonary artery. Several cardiovascular surgical centres are performing definitive rep air in the neonatal period.
Tricuspid atresia
Because of agenesis (atresia) of the tricuspid valve, there is no communication between the right atrium and right ventricle. There is an obligatory right-to-left shunt at the atrial level through an ASD or patent foramen ovale and usually associated hypoplasia of the right ventricle as well as a VSD or PDA. There may be normally related great vessels or associated transposition. Chest radiography demonstrates a normal or small heart with decreased pulmonary blood flow. There is convexity of the left cardiac border with an elevated apex and concave main pulmonary artery segment. The right heart border may be straight (Fig. 25 a). Angiocardiography demonstrated the pathologic anatomy (Fig. 25 b).
Ebstein anomaly
In this anomaly, there is redundancy of tricuspid valve tissue and adherence of this valve tissue to the right ventricular wall. This causes a functional obstruction to the emptying mechanism of the right atrium, as well as tricuspid regurgitation. An interatrial communication (either patent foramen ovale or ASD) is almost always present. Radiographic findings depend on the severity of the anomaly. Infants with Ebstein
 a | Figure 25.Tricuspid atresia.
a) 2-day-old male with cyanosis. The heart is mildly enlarged in its transverse diameter. There is convexity of the lower left cardiac border with an elevated apex and concave main pulmonary artery segment. There is slight flattening of the lower right heart border.
b) 1-month-old female with cyanosis. The catheter could not be passed through the tricuspid valve. Injection of contrast material into the right atrium (RA) shows opacification of the left atrium (LA) and left ventricle (LV). There is a triangular lucency (arrow) to the left of the tricuspid valve in the position normally occupied by the inflow portion of the right ventricle.
[From Kirks.] |
 b |
 | Figure 26.
Transposition of the great vessels. Newborn male with profound cyanosis. The heart is not enlarged. The heart is more oval than normal. Pulmonary vascularity is normal. |
anomaly present with severe cyanosis and may have decreased pulmonary vascularity and massive cardiomegaly due to right atrial enlargement. Older patients, with milder malformations, have a mildly enlarged heart with a "box-like" appearance. This abnormal cardiac shape is due to right atrial enlargement; there is usually some decrease in pulmonary vascularity.
Cyanotic CHD with increased pulmonary blood flow
Transposition of great vessels (TGV)
Complete transposition of the great vessels is the most common congenital heart disease presenting with cyanosis during the first 24 hours of life. The lesion may be isolated or part of a more complex anomaly.
In TGV, the aorta and pulmonary arteries are transposed. The ascending aorta and coronary arteries arise from the right ventricle while the pulmonary artery arises from the left ventricle. As a result of the abnormality in arterial relations, there are two parallel circuits. Desaturated systemic venous blood enters the right atrium, passes into the right ventricle, and is ejected into the aorta. There must be a left-to-right shunt for survival; possible communications between the two circulations include a patent foramen ovale, ASD, VSD, PDA, systemic collateral arteries, or any combination of these. Due to physiologic pulmonary arterial hypertension, the pulmonary blood flow is usually normal at birth (Fig. 26). As the pulmonary vascular resistance decreases, the pulmonary blood flow becomes increased. If there is a small shunt between the two circulations or if there is associated pulmonary stenosis, the pulmonary vascularity is normal or decreased.
The radiographic findings of TGV include (l) the superior mediastinum is narrow due to absence of thymic tissue and abnormal relationship of the great vessels. (2) There is an absence of visualization of the malpositioned aortic arch on the left and a concavity in the region of the main artery segment since both the aorta and main pulmonary artery are rightward in position. (3) Frequently, there is asymmetry of pulmonary arterial blood flow. As noted above, the pulmonary arterial flow may be diminished if there is associated subpulmonic or pulmonic stenosis, normal in the first few days of life or if the size of a left-to-right shunt(s) is small, or increased if there is significant intracardiac shunting. A Rashkind balloon atrial septostomy now permits survival until
 a | Figure 27.Atrial balloon septostomy.
a) Balloon is inflated in the left atrium.
b) Balloon pulled through the foramen ovale.
c) The deformed balloon is in the interior vena cava. |
 b |
 c |
definitive repair can be performed. A balloon
catheter is placed across the atrial septum, and the balloon is inflated. Once position is verified, the balloon is rapidly withdrawn across the atrial septum, rupturing and enlarging the interatrial communication (Fig. 27). This interatrial communication permits better mixing of blood with decrease in clinical cyanosis. At several
cardiac surgical centres in the world, primary surgical rep air (arterial switch procedure) is performed in the newborn period.
Other congenital lesions included as part of the transposition complex include double outlet right ventricle, Taussig-Bing complex, and corrected transposition of the great vessels.
Truncus arteriosus
Truncus arteriosus (TA) is due to failure of division of the primitive common truncus arteriosus into aorta and pulmonary artery. One large vessel (truncus) originates from the heart to supply the coronary circulation, systemic circulation, and pulmonary circulation. There is an associated VSD, which is high in position and large in size.
TA is an admixture lesion. There is right-to-left shunting across the VSD and high flow from the truncus into the pulmonary arteries; the pressure in the two ventricles is similar. Cyanosis and heart failure occur early in infancy. Peripheral pulses are bounding, and the pulse pressure is wide because of aortic run-off.
Cardiomegaly is frequently present at birth; as pulmonary vascular resistance decreases (after the 2nd or 3rd day of life), there is a marked increase in pulmonary arterial blood flow. The truncus or ascending aorta is usually prominent. A right-sided arch is identified in one-third of patients and, in conjunction with increased pulmonary vascularity and cardiomegaly, is highly suggestive of the diagnosis.
Total anomalous pulmonary venous return
Total anomalous pulmonary venous return (TAPVR) is due to an error of embryologic development. It occurs when the common pulmonary vein fails to develop or is obliterated so that pulmonary veins connect with other venous structures.
TAPVR may be divided into 4 main groups according to the site or sites of connection: supracardiac, cardiac, infracardiac, and mixed.
The radiographic appearance of TAPVR varies according to the site of abnormal venous drainage as well as the presence or absence of obstruction of anomalous vein. In supracardiac TAPVR, the dilated left vertical vein, right superior vena cava, and right atrium give the appearance of a "snowman". On lateral chest radiographs there may be a pretracheal density due to superimposition of the left vertical vein on the superior vena cava.
In TAPVR at the cardiac level, the pulmonary venous blood flows into the coronary sinus and right atrium. The radiologic findings simulate a large left-to-right shunt at the atrial level.
The infracardiac type of TAPVR (obstructed) demonstrates a normal sized heart with severe pulmonary edema. Kerley B lines are usually present due to pulmonary venous hypertension. This serious cardiovascular anomaly may be confused with pulmonary parenchymal abnormalities such as wet-lung disease or neonatal pneumonia.
Cardiomegaly without cardiac malformation
These congenital and acquired heart diseases are characterized by cardiomegaly and pulmonary venous hypertension. Lesions distal to the mitral valve usually have cardiomegaly because of left ventricular failure or dysfunction. Cardiac enlargement is out of proportion to the prominence of the pulmonary vascularity. Although there is interstitial edema due to pulmonary venous hypertension, there is no shunt vascularity.
Infiltrative disease
Endocardial fibroelastosis may occur as a primary disease or may be secondary to left ventricular obstruction. There is marked deposition of collagen and elastin within the endocardium of the left ventricle; this causes restricted left ventricular contractility and subsequent mitral insufficiency. Chest radiography demonstrates cardiac enlargement with significant enlargement on lateral film of the left ventricle and left atrium.
Glycogen storage disease leads to deposition of glycogen in the skeletal muscles and myocardium. There is massive thickening of the ventricular septum and walls resulting in cardiomyopathy. Chest radiography shows striking cardiac enlargement; this cardiomegaly is out of proportion to the prominence of the pulmonary vascularity. As a child becomes older, there is increasing left atrial enlargement that compresses the left lower lobe bronchus and may cause collapse.
Coronary artery abnormalities
In patients with anomalous origin of the left coronary artery, the left coronary artery arises from the pulmonary artery. This is a rare anomaly that usually presents in young children with tachypnea and sweating. The EKG shows changes of myocardial ischemia or infarction. The chest radiograph may be entirely normal. However, if the patient has had an infarct, marked cardiomegaly is present. Left ventricular enlargement and left atrial enlargement, secondary to mitral insufficiency, may be present.
Coronary artery fistula
is characterized by a communication between a dilated coronary artery and an intracardiac chamber. The etiology is probably due to persistence of
 a | Figure 28.Double aortic arch.
a) Lateral esophagogram shows a posterior impression on the esophagus (arrow) and marked tracheal narrowing (arrow).
b) Axial MRI. The right (R) and left (L) limbs of the double arch are seen encircling the trachea and esophagus.
c) Coronal MRI demonstrates that the right (R) and left (L) limbs of the double arch join posteriorly. The right arch (R) is higher and larger.
[From Kirks.} |
 b |
 c |
normal fetal
vascular communications. Most fistulas from the coronary arteries enter either the right atrium or right
ventricle. This results in significant left-to-right shunting. Clinically, a murmur may suggest a PDA.
Echocardiography is extremely useful for the diagnosis of these lesions.
Acquired heart disease
Acquired heart disease is much less common in children than in adults. Etiologies include arrhythmia, anemia, fluid overload, Kawasaki disease, and acute rheumatic fever. Depending on the severity of the cardiac insult, the heart may be normal in size, or enlarged. Congestive heart failure may develop.
A vascular ring is an anomaly in which there is complete encirclement of the trachea and esophagus by the aortic arch and its vascular derivatives. If a vascular ring is not complete, there are rarely symptoms. If a vascular ring is present, symptoms may be due to tracheal compression or esophageal compression. The most common asymptomatic vascular rings are left aortic arch with aberrant right subclavian artery or innominate artery compression. The most common symptomatic vascular rings are double aortic arch, right aortic arch with aberrant left subclavian artery and aortic diverticulum, and pulmonary sling.
The diagnosis of vascular rings traditionally has been based on chest radiography and esophagography. MRI now allows precise anatomic diagnosis without invasive studies. Angiography is rarely required.
Double aortic arch
Double aortic arch is the most common type of vascular ring. Although the anomaly usually exists in isolation, it can be associated with congenital heart disease. The ascending aorta rises anterior to the trachea and divides into an anterior and posterior branch; these branches then join posteriorly to form a common descending aorta. The right arch is usually larger, more posterior, and higher than the left aortic arch; it passes posterior to the trachea and the esophagus (Fig. 28).
Pulmonary sting
Anomalous origin of the left pulmonary artery may be a part of a more complex anomaly, or it may be an isolated finding. The left pulmonary artery is aberrant and arises from the right pulmonary artery. It crosses over the proximal portion of the right main stem bronchus or trachea and then proceeds posteriorly to the left behind the trachea in front of the esophagus. Plain radiographs of the chest usually show abnormal aeration of the lungs, low position of the left hilum, and anterior bowing of the lower trachea or right main-stem bronchus. An esophagogram shows anterior bowing of the trachea and a ventral impression on the esophagus by the aberrant vessel (Fig. 29). MRI accurately assesses the vascular anomaly as well as the degree and extent of any associated tracheal abnormality.
Donald R. Kirks and Sven Laurin