Diagnosis of Congenital Heart Disease III.L.D.Tonkin

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Introduction

Recent advances in diagnostic radiology have radically altered the approach to the diagnosis of congenital heart disease (CHD). Sophisticated trans-thoracic and trans- esophageal echocardiography is perhaps the best-known example. Additionally, state of the art magnetic reso- nance (MR) and multidetector computed tomography (CT) scanners, each with cardiac packages, can render di- agnostic angiocardiography unnecessary at times. With an accurate diagnosis, interventional angiocardiography, embolotherapy, surgical correction, or even cardiac trans- plantation can be accomplished for palliation or cure.

In spite of these imaging breakthroughs, many if not most CHD patients, independent of age, are referred to the radiologist with a request for a chest radiograph, either one or two views. The accompanying patient report usu- ally includes a few, brief clinical observation (e.g., cyan-

otic infant, shortness of breath, enlarged heart, murmur).

Consequently, the traditional approach to treating such pa- tients, i.e., situs evaluation, vascular pattern assessment, and cardiac contour/chamber analysis, still merits review.

Most importantly, this approach follows directly from the underlying pathophysiology seen in CHD, in which there are deranged flow dynamics and cardiac chamber alter- ations. With this in mind, this article describes a schemat- ic approach to assessing the most common forms of CHD, without technically addressing specific CT/MR protocols, which are covered elsewhere in the IDKD.

Approach to the Plain Chest Radiograph in Patients with Heart Disease

The situs of heart disease is inferred based on the anato- my of the atria (Fig. 1), the anatomy of the tracheo-

IDKD 2007

Diagnosis of Congenital Heart Disease II

I.L.D. Tonkin

Division of Cardiovascular, Interventional, and Pediatric Radiology, University of Tennessee Health Science Center, Memphis,TN, USA

Fig. 1. Normal cardiac anatomy. From Netter FH (1969), and from Elliott LP (1991), with permission

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bronchial tree, the position of the pulmonary arteries, lo- cation of the thoracic and abdominal viscera, and iso- merism (symmetric morphology) (Figs. 1, 2). Situs soli- tus, or normal situs, is defined by the position of the stomach (and liver), the cardiac apex, and the aortic arch. In this type of situs, the patient’s bronchial and atri- al anatomies suggest right and left sidedness in the nor- mal positions. Accordingly, situs inversus refers to a re- verse of the normal situs. Situs indeterminus (situs am- biguous) is further described with respect to either bilat- eral right isomerism (sidedness), such as occurs in as- plenia syndrome, or bilateral left isomerism, as seen in polypslenia syndrome. Bilateral right isomerism consists of bilateral eparterial bronchi and right-sided atrial structures, the absence of a spleen, and an increased in- cidence of congenital heart disease. In bilateral left iso- merism, there are multiple splenules along the greater curvature of the stomach, bilateral left isomerism with bilateral hyperarterial bronchi, and bilateral left pul- monary arteries extending over the bronchi. There is al- so a bilateral left atrial anatomy with bilateral left atrial appendages, as well as abnormal systemic venous con- nections and azygos or hemiazygos continuation with in- terruption of the hepatic segment of the inferior vena ca- va. Bilateral left isomerism is associated with a lower in- cidence of CHD.

The Pulmonary Vasculature in CHD

The pulmonary vasculature in CHD patients can be dif- ficult to evaluate and requires considerable experience.

The radiographs of these patients are difficult to inter- pret and must be ‘overread’ in order to identify the vas- cular defects. Pulmonary vascularity may be normal, in- creased, or decreased. Increased vascularity is associat- ed with pulmonary overcirculation (shunt vascularity), pulmonary venous hypertension, or pre-capillary hyper- tension (pulmonary arterial hypertension). In addition, there may be systemic collaterals from the aorta and major aortopulmonary collateral arteries (MAPCAs).

An overview of the four main groups of CHDs with re- spect to the pulmonary vascular pattern is provided in Table 1.

Group 1 CHDs: Increased Pulmonary Vascularity Without Cyanosis

Due to the difference in pressure and resistance between the greater and lesser circulation, the communication be- tween the two circuits results in increased pulmonary blood flow with increased blood flow through the left atrium, which is enlarged in all cases unless it is decom-

Table 1.Congenital heart disease classification by pulmonary vascular pattern

Acyanotic Cyanotic

Group 1 Group 2 Group 3 Group 4

↑PBF PVH or normal ↓PBF ↑PBF

Left to right shunts LV inflow or outflow obstruction; Right to left shunts due to RV Admixture lesions muscle disease inflow or outflow obstruction

Group 2a: Neonatal Group 3a: Normal heart size;

Group 2b: Childhood or later VSD present Group 3b: Cardiomegaly;

intact septum

PBF, Pulmonary blood flow; PVH, pulmonary vascular hypertension; LV, left ventricle; RV, right ventricle; VSD, ventricular septal defect Fig. 2. Types of situs. RL, Right lung; LL, left lung; RA, right atrium; LA, left atrium. From Tonkin ILD (1992), with permission

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pressed by a large atrial communication. Table 2 lists the group of acyanotic CHDs characterized by increased pul- monary blood flow, some of which are described below in greater detail.

Ventricular Septal Defect

The most common congenital cardiac anomaly is ventric- ular septal defect (VSD): It occurs as an isolated lesion in 20% of CHD patients and is present with other anomalies in another 5% of patients. Four types of VSD can be dis- tinguished: (1) membranous VSD (80%), (2) muscular (10%), (3) A-V canal type (5%), and (4) supracristal (5%).

The radiographic findings seen on cardiac imaging of VSD consist of increased pulmonary vascularity, acyanosis, an enlarged pulmonary artery, and an enlarged left atrium.

Atrial Septal Defect

Of the five recognized types of atrial septal defect (ASD), the most common is septus secundum, abnormal resorp- tion of the fossa ovalis. In the septum primum type, the defect is situated low, near the mitral valve, and consists of a partial atrioventricular canal. In sinus venosus, the third type of ASD, the most common defect results in par- tial anomalous pulmonary venous return, as the right up- per lobe pulmonary vein drains into the vena cava. An inferior vena caval defect can rarely occur. In patients with a stretched patent foramen ovale, the defect is func- tional due to right atrial enlargement and right atrial hy- pertension.

The radiograhic findings on cardiac imaging of ASD can include increased pulmonary vascularity, acyanosis (clinically evident), the absence of left atrial enlargement, and an enlarged right ventricle. Atrial-level CT/MR imaging with contrast enhancement will detect and iden- tify the type of ASD and show alterations in pulmonary venous return.

Atrioventricular Septal Defects (Endocardial Cushion Defect)

In atrioventricular septal defects, also known as endo- cardial cushion defect, three types of defects are recog- nized. In the partial form there is low atrial septal de-

fect, ostium primum type, and a cleft in the mitral valve. In the intermediate form, there is low and a small VSD, whereas complete endocardial cushion defect consists of low ASD, a large VSD, and complete clefts within the atrioventricular valves.

Patent Ductus Arteriosus

In this acyanotic CHD, imaging may reveal a prominent aorta. A characteristic murmur is heard on auscultation (Figs. 3, 4).

Table 2. Acyanotic CHD with increased pulmonary blood flow (left to right shunts)

Common Rare

Ventricular septal defect Aortic pulmonary window Atrial septal defect Sinus of Valsalva aneurysm Patent ductus arteriosus Coronary artery fistula

Endocardial cushion defect Left ventricle to right atrium shunts (atrioventricular septal defect)

Partial anomalous pulmonary venous return

Fig. 3. Fetal circulation with patent ductus arteriosus. From Tonkin ILD (1992), with permission

Fig. 4. Schematic illustration of the defects in patent ductus arte- riosus (PDA) and aortic pulmonary window (APW). Ao, Aorta;

PT, pulmonary trunk; LIG ART, ligamentus arteriosus. From Gedgaudas E et al. (1985), with permission

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Miscellaneous Left-To-Right Shunts

The common feature of these CHDS is left-to-right shunt- ing. In aortic pulmonary window (Fig. 4), the shunt arises from the connection between the ascending aorta and main pulmonary artery. Patient with ruptured aortic sinus of Valsalva aneurysm will present with a continuous murmur and shunt vasculature. The aneurysm itself is not evident on the plain radiograph but may be seen at echocardiography, MR imaging, or double subtraction angiography. Coronary- artery fistula is defined as a communication between a coronary artery and either a chamber of the heart or a com- ponent of the systemic or pulmonary circulation. The rare patient with left ventricular to right atrial shunt will present with clinical features of atrial shunt but have a murmur re- sembling that of VSD as well as right atrial enlargement.

Group 2 CHDs: Acyanotic with Pulmonary Vascular Hypertension or Normal Vascularity

Either valvular obstruction or obstruction of the great vessels may be associated with pulmonary vascular hy- pertension or normal vascularity. Obstruction of the great vessels will occur in patients with coarctation of the aor- ta (Fig. 5a, b), either preductal or postductal (juxtaduc- tal), and in those with pulmonary valve stenosis.

Stenosis of the Aortic Valve

Aortic stenosis may be supravalvular, valvular or manifest as hypertrophic obstructive cardiomyopathy (idiopathic hypertropic subaortic stenosis; IHSS). The most common form of aortic valve stenosis involves the bicuspid valve (Fig. 6). In the USA, 2% of the population is estimated to have this type of CHD. It is thus the most common con- genital heart lesion in all age groups (Fig. 6).

Obstruction of the Great Vessels: Coarctation of the Aorta, Pulmonary Valve Stenosis, and Venous Obstruction

The clinical findings of coarctation are decreased femoral pulses in the lower extremities. In the juxtaduc- tal form of the disease (Fig. 6b), the radiographic find- ings include rib notching of ribs 3-8 in school-age chil- dren, normal pulmonary vascularity, and a normal-size

heart with a left ventricular contour. Other findings are an abnormal aortic arch with a characteristic ‘3’ sign and a ‘reverse 3’ sign with barium in the esophagus. An ab- normal aortic valve is found in 50-85% of these patients.

Stenosis and partial fusion of the pulmonary valve re- sults from fused or dysplastic valve leaflets. Pulmonary vascularity is normal as is the size of the heart. However, the main pulmonary artery is enlarged and a prominence of the left proximal pulmonary artery can be seen.

Pulmonary venous obstruction causes usually a char- acteristic granular pattern in infancy that is sometimes in- distinguishable from respiratory distress syndrome (RDS, or hyaline membrane disease). The presence of an air bronchogram may help to identify RDS. Redistribution of pulmonary blood flow occurs later in life. These le- sions place an increased demand on the right ventricle, which consequently hypertrophies. The heart size is usu- ally normal or slightly enlarged.

Other CHDs – Venous Obstruction

Congenital mitral stenosis is a very rare form of CHD. It is associated with hypertrophy of the right ventricle and left atrial enlargement.

In cor triatriatum, left atrial enlargement is also some- times visible along the right heart border. Cardiac imaging

Fig. 6. Aortic valve stenosis. From Netter FH (1969)

Fig. 5a, b. Coarctation of the aorta. a Pre-ductal (in- fantile); b juxtaductal (postductal).From Elliott LP (1991), with permission

a b

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with CT/MR demonstrates the presence of a membrane in the left atrium, an accessory chamber, and restricted ASD.

Patients with stenosis of individual pulmonary veins will have unilateral pulmonary edema but not left atrial enlargement.

Left atrial enlargement is also not a feature of total anomalous pulmonary venous return below the di- aphragm. In this condition, the heart is of normal size.

Congestive heart failure results from a variety of pri- mary cardiomyopathies.

The four most common vascular compression anom- alies are illustrated in Fig. 8.

Group 3 CHDs: Decreased Pulmonary Blood Flow Group 3A: Decreased Pulmonary Flow with Cyanosis

Perhaps the best-described CHD of this group is tetralo- gy of Fallot (Fig. 9). The radiographic findings on cardiac imaging are decreased pulmonary vascularity, right ven- tricular hypertrophy (‘coeur in sabot’), an inapparent pul- monary artery segment, and a large aorta. In 25% of af- flicted patients, the right arch is involved, sometimes with a boot-shaped heart. Palliative surgery includes a Blalock-Taussig shunt or a central shunt (Fig. 10 a, b).

Fig. 7.Pulmonic valve stenosis stenotic and partially fused pul- monary valve. Ao, Aorta; PA, pulmonary artery; RA, right atrium;

LA, left atrium; RV, right ventricle; LV, left ventricle. From Gedgaudas E et al. (1985), with permission

Fig. 9. Tetralogy of Fallot. Ao, Aorta;

LA, left atrium; LV, left ventricle. From Amplatz K, Moller JH (1994), with permission

Fig. 8 a-d. Vascular compression anomalies. a Double aortic arch; b anomalous innominate artery; c right arch, with an aberrant left sub- clavian artery (usually a vascular ring), or left arch, with an aberrant rightsubclavian artery (usually not a ring); d pulmonary sling. From Berdon WE et al. (1972), with permission

a b

c d

Fig. 10a, b. Surgical treatment of tetralogy of Fallot. a Blalock- Taussig shunt; b central shunt. From Amplatz K, Moller JH (1994), with permission

a

b

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Embolotherapy has been used to occlude the MAPCAs of patients with tetralogy of Fallot (Fig. 11). Gelfoam, Ivalon, and platinum coils have been used as embolic material.

Group 3B (Cardiomegaly)

In this group of cyanotic CHDs, cardiomegaly and an in- tact ventricular septum are the predominant features.

Several examples are shown in Figs. 12-14.

Group 4 CHDs: Cyanosis with Increased Pulmonary Blood Flow

This group of CHDs includes transposition of the great vessels (the most common), truncus arteriosus, total anomalous pulmonary venous connection (TAPVC) above the diaphragm, the ‘tingles’ (involving a single ventricle or atrium), and tricuspid atresia (without right ventricular outflow tract obstruction).

Fig. 11. Major aortopulmonary collateral arteries (MAPCAs). From Mullins CE et al. (1988), with permission

Fig. 12.Pulmonary stenosis or atresia. Note the intact ventricular septum, the very large heart, and the markedly decreased pulmonary vascularity. From Amplatz K, Moller JH (1994), with permission

Fig. 13. Tricuspid atresia. Left axis deviation is noted on the ECG.

On a chest radiograph, the left ventricle may be normal or have a rounded contour. Ao, Aorta; PA, pulmonary artery; LA, left atrium;

RV, right ventricle; LV, left ventricle. From Gedgaudas E et al.

(1985), with permission

Fig. 14. Ebstein’s anomaly, in which the tricuspid valve is abnor- mally formed, may feature a very large heart. A characteristic murmur is present. From Netter FH (1969)

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D-transposition of the Great Vessels

The reversal of the connections of the aorta and pulmonary artery is the most common neonatal cyanotic congenital heart lesion. The transposition results in arterioventricular concordance and ventriculoarterial discordance (Fig. 15).

The radiographic findings on cardiac imaging of a D- transposition include normal to increased pulmonary vascu- larity, an inapparent pulmonary artery segment, right-heart prominence, and an ‘egg’ or ‘apple on string’ appearance.

Truncus Arteriosus

Cardiac imaging of truncus arteriosus will reveal in- creased pulmonary vascularity, a right aortic arch (35%

of patients), and an elevated left pulmonary artery (type I truncus arteriosus) (Fig. 16).

Total Anomalous Pulmonary Venous Connection

In this CHD, all of the pulmonary veins are anomalously connected. Four variations of TAPVC have been de- scribed, It should be noted that left atrial enlargement is never seen in patients with TAPVC.

In type I TAPVC, the connections are supracardiac and involve the left vertical vein, innominate vein, superior vena cava, and right atrium. This condition is sometimes referred to as ‘snowman’s heart’. Type II TAPVC is at the cardiac level, with connections to the coronary sinus or right atrium. In type III disease, the connections are infra diaphragmatic, with drainage into the portal vein. In type IV, the connections are mixed, with various flows of the pulmonary veins to the right side of the heart (Fig. 17).

Fig. 16. Truncus arteriosus. Three variants of the condition are recognized. From Elliott (1991), with permission

Fig. 17. Total anomalous pulmonary venous return above the diaphragm, to the coronary sinus, and below the diaphragm. From Elliott (1991), with permission

Fig. 15.Complete transposition of the great arteries. From Elliott (1991), with permission

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The ‘Tingles’

In CHD patients with a single ventricle (‘tingle ventri- cle’), there will be situs anomalies and an inapparent pul- monary artery segment except for a double-outlet right ventricle. Other forms of this abnormality are single atri- um (‘tingle atrium’) and tricuspid atresia (without right ventricular outflow tract obstruction).

Hypoplastic Left Heart

The radiographic findings in patients with hypoplastic left heart include a normal to mildly enlarged heart (1-3 days), pulmonary edema, severe pulmonary venous ob- struction, and right to left shunt across the posterior de- scending artery. Echocardography is diagnostic and will demonstrate an enlarged right heart and pulmonary artery as well as an underdeveloped left heart and ascending aorta. CT/MR imaging will also show the underdevel- oped left heart. A hypoplastic ascending aorta and aortic valve can be seen on angiography, which also reveals the positions of the coronary arteries, posterior descending artery, and brachiocephalic arteries (Fig. 18).

Clinical Information

The presence or absence of cyanosis and the age of the patient are important factors to consider in the diagnosis of CHDs. Diagnostic accuracy is increased by obtaining

a detailed clinical history, a chest radiograph, ECG, and echocardiogram. CT and MR imaging will often provide invaluable diagnostic information, as will cine angio- cardiography or digital subtraction angiography. Inter- ventional procedures may also be required.