Chest and cardiac: Disorders
Congenital lobar hyperinflation [link]
Congenital pulmonary airway malformation [link]
Sequestration [link]
Congenital diaphragmatic hernia [link]
Bronchogenic cyst [link]
Bronchiolitis [link]
Pneumonia [link]
Tuberculosis [link]
Hyaline membrane disease [link]
Pulmonary interstitial emphysema (PIE) [link]
Cystic fibrosis [link]
Lymphoma [link]
Inhaled foreign body [link]
Kawasaki's disease [link]
Congenital cardiac disease [link]
Cardiac MRI [link]
Atrial septal defect (ASD) [link]
Ventricular septal defect [link]
Patent arterial duct (ductus arteriosus) [link]
Tetralogy of Fallot [link]
Vascular rings [link]
Aortic coarctation [link]
Scimitar syndrome [link]
Uncommon congenital cardiac conditions [link]
Congenital lobar hyperinflation
This was previously called congenital lobar emphysema, which is a poor term as there is no alveolar destruction. It is due to progressive overdistension of a pulmonary lobe due to antenatal airway obstruction. The alveoli are dilated; the walls are thinned but intact. Patients usually present with respiratory distress in the neonatal period, but increasingly it is being diagnosed with antenatal ultrasound.
Imaging findings
Radiographs
The most useful diagnostic feature is a radiodense lobe that becomes radiolucent and hyperexpanded as fetal fluid is replaced with air.
• Lobar predeliction:
• Left upper lobe 42%.
• Right middle lobe 35%.
• Right upper lobe.
• Compression of ipsilateral lung.
• Mediastinal shift to contralateral side.
Differential diagnosis
• Congenital pulmonary airway malformation (CPAM).
• Bronchial atresia.
• Pulmonary artery hypoplasia (affected lung is small).
• Pulmonary hypoplasia (affected lung is small).
• Congenital diaphragmatic hernia.
Management
• Bronchoscopy to exclude an endobronchial lesion.
• Surgical lobectomy.
• Conservative treatment may be considered for patients with minimal symptoms.
Fig. 2.5CXR of a newborn baby with congenital lobar hyperinflation of the right upper lobe of the lung. The lobe will become more hyperlucent over time as fluid from the lung is absorbed.
Congenital pulmonary airway malformation
This entity was previously called congenital cystic adenomatoid malformation. It is an uncommon cause of respiratory distress in neonates and infants characterized by a multicystic mass of pulmonary tissue with an abnormal proliferation of bronchial structures. The etiology is unknown. This malformation was originally classified by Stocker et al.1 into three histologic types.
• Type I is composed of variable-size cysts, with at least one dominant cyst (>2cm in diameter). This type is the most common.
• Type 2 and contain smaller cysts (0.5–2cm).
• Type 3 appear solid, but contain multiple small cysts (0.3–0.5cm).
Imaging findings
Radiographs
• Solid/multicystic mass depending on cyst size and amount of fluid.
• May cause mass effect: mediastinal shift, compression of adjacent lung.
• If the lesion is very large and causes cardiac compromise heart failure (hydrops) may occur.
Differential diagnosis
• Sequestration: usually do contain air, and have a systemic blood supply.
• Congenital lobar hyperinflation.
• Congenital diaphragmatic hernia.
• Cavitating pneumonia.
Management and prognosis
• Most advocate that the lesion is resected to avoid risk of infection. There have been multiple case reports associating CPAMs with malignancy.
• Lesions are easier to resect electively rather than after infection.
Fig. 2.6CT of a cystic pulmonary airway malformation. Notice the small cysts in the medial aspect of the left lower lobe.
Sequestration
Pulmonary sequestration is a congenital abnormal area of lung that does not connect to the bronchial tree or pulmonary arteries. This area of lung is dysplastic and does not function, and is prone to infection. The most common symptomatic presentation is with repeated infection, but increasingly they are diagnosed antenatally. It has a systemic arterial supply, usually from the aorta. There are two main types:
Imaging findings
Radiographs
• Persistent lower lobe opacity, usually left-sided.
• If infected may appear multicystic.
Ultrasound
• Antenatal ultrasound—hyperechoic mass.
• Hyperechoic mass may be seen postnatally.
• Feeding artery can be visualized. This feature can help differentiate from other masses, particularly if infradiaphragmatic.
Differential diagnosis
• CPAM
• Chronic pneumonia
• Diaphragmatic hernia
• Infradiaphragmatic lesions:
• Neuroblastoma
• Adrenal haemorrhage
• Pulmonary blastema (rare)
Congenital diaphragmatic hernia
A congenital defect in the diaphragm results in herniation of abdominal contents into the chest. There are two main types:
• Bochdalek hernia. Posterior defect: most common
• Morgagni hernia. Anterior: rare
Imaging findings
Radiographs
• Most commonly left-sided.
• Rounded lucencies within the chest that look like bowel.
• Appearance depends on the contents of the hernia and whether bowel is air-filled.
• Right-sided hernias may contain liver.
• Poorly visualized diaphragm.
• Hernia may cause mediastinal shift to contralateral side.
• Lungs often small due to hypoplasia.
• Abnormal position of NG tube tip.
Differential diagnosis
• CPAM.
• Congenital lobar hyperinflation.
• Cavitating pneumonia.
• Diaphragmatic eventration.
Bronchogenic cyst
Bronchogenic cysts are congenital abnormalities. The bronchial tree develops from a bud from the foregut in early gestation. Abnormal budding results in bronchogenic cyst (hence also called foregut duplication cysts). Lesions do not communicate with the bronchial tree. They can cause symptoms from compression (respiratory distress, dysphagia). The true incidence is unknown, as probably most are incidental.
Imaging findings
Radiographs
• Well-defined round mass.
• May not be visible.
• Usually requires further cross-sectional imaging.
CT
• Round homogenous lesion.
• Attenuation value depends on cyst content which can range from water to proteinaceous fluid.
• Do not enhance, but the rim may enhance, and the cyst may contain air if complicated by infection.
• Most common location is close to the carina, but they can occur in the lung parenchyma.
Differential diagnosis
• Round pneumonia.
• CPAM (usually not unilocular).
• Neurogenic tumours (more solid in appearance, often calcified).
• Lymphadenopathy.
• Pulmonary sequestration (usually lower lobe, with feeding artery).
• Pulmonary blastema (rare).
Management and prognosis
• Surgical resection to avoid infection.
• There have been some case reports of associated malignancy.
Fig. 2.9CXR of a patient with a bronchogenic cyst. (a) The trachea (white arrow) is displaced to the left by (b) the cyst (black arrow).Fig. 2.10CT of the same patient. The trachea (white arrow) is deviated to the right by the bronchogenic cyst.
Bronchiolitis
Bronchiolitis is a viral infection of the lower respiratory tract. It is very common in young children. Not all children with bronchiolitis require a chest radiograph, particularly if the child has typical features of a viral infection (cough, wheeze, runny nose). CXR is indicated in children when a bacterial infection is suspected.
Differential diagnosis
• Asthma:
• The radiographic appearances are almost identical, as both viral infections and asthma cause inflammation of the small airways.
• Left to right shunts:
• Pulmonary plethora can have a similar appearance, there is usually associated cardiomegaly.
Pneumonia
Imaging findings
Plain radiographs
• Viral lower respiratory tract infection: perihilar bronchial wall thickening, hyperinflated lungs. There may be areas of focal opacity, and subsegmental atelectasis due to bronchial plugging.
• Bacterial pneumonia usually manifests as an area of consolidation; segmental to lobar opacity with air bronchograms.
• Bacterial pneumonia can be complicated by the formation of:
• Empyemas: these may require surgical intervention or drainage
• Cavities: which may result in the formation of bronchopleural fistulas and recurrent pneumothoraces.
• Mycoplasma pneumonia is a common cause of pneumonia in older children and typically causes bilateral perihilar opacity.
• ‘Round’ pneumonias, which appear as solitary large round masses on the CXR, are more common in children.
Ultrasound
• Helpful to demonstrate effusions and whether they are simple (anechoic) or are complex (containing septae and debris).
Fluoroscopy
Recurrent aspiration due to gastro-oesophageal reflux may cause repeated pneumonia. This can usually be demonstrated by a barium meal examination. Very rarely, an H-type tracheo-oesophageal fistula may be the cause of recurrent pneumonia.
CT
CT may be required to exclude an underlying cause of repeated chest infections in children, for example:
• Sequestration or CPAM.
• Bronchiectasis.
• CT may be requested if surgical intervention is necessary to treat complications of pneumonia. CT demonstrates loculated collections, lung cavitation and abscess formation or purulent pericarditis.
Management and prognosis
• Antibiotics.
• Prognosis is usually good.
Fig. 2.12CXR of a child with a right-sided round pneumonia.Fig. 2.13CXR of a child with severe, bilateral cavitating pneumonia. An air–fluid level is seen within one cavity on the right (black arrow). There are associated bilateral pleural effusions (white arrow).
Tuberculosis
Tuberculosis (TB) is increasing in frequency throughout the world. It is more common in poorer, crowded communities. Infection in children is due to close contact with a person with active, cavitating, sputum-positive disease.
Spectrum of disease
Primary complex
• Usually asymptomatic, may cause malaise, fever, erythema nodosum.
• Consolidation in lower or middle lobe, and enlarged draining lymph node.
Progressive primary TB
• Lobar or bronchopneumonia, associated with haemoptysis, weight loss and cavitation.
Pleural effusions
• Usually reactive, but can be due to bacilli that have ruptured into the pleural space.
Lymphadenopathy
• Most common extrathoracic site is the neck (scrofula).
• Nodes are typically non-tender.
• Imaging (ultrasound of neck nodes, or CT of chest or abdominal disease) often shows central necrosis.
Miliary TB
• Widespread blood-borne dissemination.
• Multiple small nodules (the size of millet seed) scattered throughout the chest. These are usually visible on CXR.
Meningitis
• Insidious disease.
• Seen in 30% of patients with military TB.
• Thickened basal meninges (best seen on post-contrast MRI).
• Associated perivascular inflammation can result in strokes. Acute infarction best demonstrated with diffusion MRI.
Abdominal TB
• Lymphadenopathy.
• Ascites.
• Bowel wall thickening; particularly the caecum.
• Features can be shown on ultrasound, CT or MRI.
Osteomyelitis
• Ill-defined lucent areas due to bone destruction and periosteal reaction, can be seen on radiographs. Skeletal lesions are usually delayed 2–3yrs after the primary infection.
• The spine is the most common site (Pott's disease).
• Other common sites include the hips and fingers (dactylitis).
• Bone scans are more sensitive.
• MRI is the gold standard investigation as it will give information about surrounding tissue and joint inflammation, sinus tracts and sequestrae (areas of dead bone).
Diagnosis
Mantoux skin test:
• 10mm induration 48hrs after injection indicates disease.
• False negative results can occur in patients early in the disease, in patients who are immunosuppressed, with AIDs, malnutrition, overwhelming disease, or patients with atypical TB.
Hyaline membrane disease
Surfactant deficiency is common in premature infants. Surfactant lowers surface tension, and allows the lungs to expand, and stay open. Without surfactant, the lungs remain of low volume. Proteinaceous exudates line the alveoli, forming hyaline membranes. Patients often need ventilatory support. Complications are common.
Differential diagnosis
• Group B Streptococcal pneumonia.
• Congenital heart disease causing interstitial oedema.
• Transient tachypnoea of the newborn (retained fetal lung fluid) usually term infants.
• Meconium aspiration: usually term infants, lungs are hyperinflated.
Pulmonary interstitial emphysema (PIE)
Air within the interstitium and lymphatics can occur in neonates on ventilatory support secondary to barotrauma. This is usually transient, but unless ventilatory pressures are altered, complications may include pneumothorax and pneumomediastinum. PIE usually develops in the first week of life.
Differential diagnosis
• Bronchopulmonary dysplasia (BPD) or chronic lung disease, is very similar in appearance: BPD usually occurs later, and changes are more gradual in onset.
• Treated surfactant deficiency: it can be difficult to deliver surfactant uniformly to all areas of the lung, which can result in partial clearing of alveoli.
• Congenital lobar hyperinflation, usually involves a whole lobe.
Cystic fibrosis
Cystic fibrosis (CF) is an autosomal recessive condition, most common in the Caucasian northern European population, causing abnormal exocrine function. Abnormal chloride transport results in thick sticky secretions, resulting in recurrent chest infections, and bronchiectasis. Thickened gastrointestinal secretions can cause obstruction. Neonates may present with meconium ileus. Pancreatic dysfunction causes steatorrhoea, diabetes and diabetes mellitus. Other symptoms include cirrhosis and portal hypertension, and failure to thrive. Diagnosis is made by a positive sweat test, and genotyping is important.
Bronchiectasis
Radiographs
• Perihilar interstitial opacity, ring and tramline in shape (
Fig. 2.17) due to bronchial wall thickening.• Plugging of airways results in small opacities, and areas of atelectasis.
Differential diagnosis
• Asthma.
• Recurrent aspiration: can cause bronchiectasis.
• Chronic foreign body: can cause bronchiectasis.
• Allergic bronchopulmonary aspergillosis.
• Immotile cilia syndrome: may have situs inversus.
• Immunodeficiency resulting in chronic lung infections.
• Bronchopulmonary dysplasia: usually history of prematurity and prolonged ventilation.
Lymphoma
Lymphoma is one of the more common malignancies seen in children in the second decade of life. It commonly involves lymph nodes. There are three main types:
• Hodgkin's: often involves the chest.
• Non Hodgkin: commonly involves abdominal solid organs and bowel.
• Lymphoproliferative disorder: can complicate organ transplantation.
Imaging findings
Radiographs
• Anterior mediastinal mass: widened superior mediastinum.
• Tracheal shift or compression.
• Enlarged, rounded hilar regions due to lymphadenopathy.
• Pericardial effusion: enlarged cardiac contour.
• Pleural effusion.
CT
• Mediastinal and hilar lymphadenopathy, usually not calcified.
• Pericardial thickening and effusion.
• Pleural effusion.
• Lung involvement: pulmonary nodules and consolidation.
• Airway compression.
• Vascular compression (e.g. SVC) associated with higher risk of general anaesthetic.
PET
• Most lymphomas are PET positive.
• Increasingly being used to determine ‘active disease’ during treatment.
Caution should be taken in imaging these patients. If lying flat, positive pressure ventilation in patients with vascular compression can reduce cardiac venous return, and cause cardiorespiratory arrest.
Differential diagnosis
• Normal thymus: does not cause deviation of airway or vessels
• TB: can be very similar in appearance.
• Germ cell tumour: anterior mediastinal mass more commonly mixed attenuation, with areas of fat, fluid or calcification.
Inhaled foreign body
A foreign body within the airway causes a ball valve effect: trapping air more distally. The most common age is 8 months–3 years. Aspiration may not be witnessed. Patients may present acutely with wheezing, or cough. Others have a chronic presentation, with infection, or wheeze not responding to medical treatment.
High index of suspicion required to make diagnosis as there may be no history of aspiration.
Differential diagnosis
• Viral infection/bronchiolitis, can cause patchy volume loss and asymmetrical lung volumes.
• Extrinsic compression of airway:
• bronchogenic cyst.
• lymphadenopathy.
• Swyer–James syndrome/bronchiolitis obliterans–assymetrical lungs.
Kawasaki's disease
Kawasaki's disease (mucocutaneous lymph node syndrome) is a systemic vasculitis which often affects the coronary arteries, resulting in aneurysm formation. It is the commonest cause for acquired coronary artery disease in children. Japan has the highest rate per population (M>F). Aetiology is unknown but an infective cause with an abnormal immune response is suggested.
Clinical presentation
There are three phases;
• Acute febrile phase (<11 days): pyrexia, hand and feet erythema, swollen tongue and oral mucosa, arthralgia, acute cholecystitis, myocarditis and pericarditis.
• Subacute phase (11–21 days): fever resolves, general irritability, conjunctival infection, desquamation of feet and toes, aneurysm formation.
• Chronic phase: clinical symptoms resolve, cardiac and aneurysmal complications including arrhythmias, functional abnormalities and myocardial infarction.
Imaging findings
Echocardiography
• Coronary artery involvement is in the proximal part at branching points.
• Myocardial dysfunction.
MRI
• Cardiac wall thinning.
• Infarcted myocardium.
• Abnormal wall motion.
• Coronary artery aneurysms.
• Larger vessels can also be involved.
• Coronary artery involvement is in the proximal part or at branching points.
Management and prognosis
High-dose anti-inflammatory drugs, intravenous gamma globulin. Imaging follow-up of any aneurysm. Occasionally surgical intervention for severe aneurysm formation.
Congenital cardiac disease
Congenital cardiac disease is a complex spectrum of abnormalities. Any child with a suspected congenital heart abnormality should be referred to an appropriate centre where a multidisciplinary approach is undertaken to confirm the nature of the underlying disorder and the appropriate management strategy, be it medical or surgical.
Clinical presentation may be in the neonatal period or later in life. In the neonate, the presence or absence of cyanosis is an important discriminating factor but cyanosis may take weeks to develop. In the older child, the presentation may be with heart failure, shortness of breath, repeated chest infections or a failure to thrive. Historically, certain classical radiographic findings of many of the congenital cardiac disorders have been described. In some circumstances, these findings represent a relative failure of management that does not reflect current surgical practice. In the vast majority of cases, the diagnosis of congenital cardiac disease is made with echocardiography, cardiac angiography, and increasingly cardiac MRI.
Neonatal congenital heart disease
During fetal life, there is a high pulmonary vascular resistance with pulmonary arterial and aortic pressures being equal. There is shunting of blood from the right to left atrium through the foramen ovale and from the pulmonary artery to descending aorta via the ductus arteriosus. Following birth and the child's first breaths, the pulmonary vascular resistance falls, causing an increase in pulmonary blood flow. The presentation of the neonate with a congenital heart defect will depend on the cardiac response to this fall in the pulmonary vascular resistance. Closure of the ductus arteriosus within the first couple of weeks of life will determine the time of presentation of duct dependent lesions.
Clinical presentation
Cyanosis +/− respiratory distress, cardiac failure +/− cyanosis and cardiovascular collapse.
Left to right shunts
Cardiac anomalies which result in shunting of blood from the systemic circulation (left side of the heart) to the pulmonary circulation (right heart). This results in volume overloading of the receiving cardiac chamber and in more chronic cases, those chambers distal to the connection. This includes ventricular and atrial septal defects (VSD and ASD), which are the commonest defects.
Cardiac MRI
Cardiac catheterization is an invasive procedure associated with significant radiation exposure with a morbidity and mortality risk. MRI is increasingly used to provide diagnostic as well as functional evaluation of cardiac lesions.
Techniques
Cardiac and respiratory gating
Images are acquired within a short time period which is synchronized to the cardiac cycle using high-quality electrocardiogram (ECG) monitoring. In some patients, they can be acquired using breath hold sequences. In less cooperative or sicker patients, there may also be respiratory motion synchronization using a bellows device. Both techniques add increased imaging times.
Cine MRI
Cardiac gated gradient echo sequences can produce multiple images over the cardiac cycle. These can be displayed as a cine loop to demonstrate the cardiac motion. This technique can identify high-flow blood as signal voids.
Blood-flow analysis
ECG gated velocity and coded cine MRI can be used to measure blood flow and assess velocity and quantity.
Imaging sequences
• ‘Black blood images’:
• Cardiac gated spin echo or double inversion recovery.
• Excellent for depicting anatomy.
• Measurement of sizes of defects.
• Size of anatomical structures.
• ‘Bright blood’:
• T2* gradient recalled echo (GRE) steady state sequences.
• Useful for flow abnormalities.
• Steady state free precession.
• Useful in identifying turbulent flow through a stenosis and regurgitant flow.
• Post-processing will allow functional evaluation of flow including ejection fraction.
• MR angiography.
• Post-gadolinium sequences with multiple projection of images will show complex anatomical relationships.
Fig. 2.21Axial (a) and oblique sagittal (b) MR images showing cardiac anatomy. Using the axial plane as a template additional images can be obtained through the ventricles and outflow tracts.
Atrial septal defect (ASD)
Defects of the atrial septum can occur in isolation or with other congenital heart diseases. The size of the defect may vary and is characterized by its location.
Types of ASD
• Patent foramen ovale: a physiological communication which usually closes after birth due to increasing left atrial pressure. Persistence of the foramen occurs with right to left shunts due to elevated right atrial pressure. Causes include tricuspid atresia, Ebstein's anomaly and hypoplastic right ventricle.
• Ostium primum defect: located in the anterior inferior aspect of the atrial septum. Often associated with defects in the mitral valve.
• Secundum defect: bordered by the fossa ovalis.
• Sinus venosus defect: in the upper atrial septum and contiguous with the SVC. Associated with anomalous connection of the right pulmonary veins to the SVC.
Clinical presentation
Often asymptomatic with a systolic murmur, feeding difficulties and failure to thrive, paradoxical emboli. Pulmonary hypertension is now rare, as the defect is usually diagnosed and treated.
Imaging findings
Ventricular septal defect
Commonest congenital heart abnormality. The size of VSDs is variable. The size of the VSD is compared with the size of the aortic valve opening, with large VSDs being of a similar or greater size than the aortic opening.
Types of VSD
• Membranous or peri-membranous just below the outflow tract beneath the aortic valve (80%).
• Inlet (10%) beneath the tricuspid valve:
• this is associated with atrioventricular septal defect (AVSD).
• Muscular (5–10%).
• Outlet (5%).
Clinical presentation
Small VSDs are asymptomatic but the child has a murmur. Larger defects cause tachycardia, tachypnea, and failure to thrive. Not usually symptomatic at birth due to high neonatal pulmonary vascular resistance that limits left to right shunting. Larger defects usually present in the first few months of life.
Imaging findings
Echocardiography
The imaging modality of choice.
• Characterizes site, type and haemodynamics of the defects.
Patent arterial duct (ductus arteriosus)
In utero, the ductus arteriosus connects the pulmonary artery and descending aorta which allows shunting of blood from the pulmonary to the systemic circulation. The ductus usually closes within the first few days of life. A patent ductus arteriosus can be an isolated finding and is a cause of increased pulmonary blood flow. It can be familial. Presentation depends on duct size.
Associations
• Lung disease, eg. hyaline membrane disease.
• Congenital heart disease, hypoplastic left heart syndrome (HLHS), transposition of great vessels, pulmonary atresia.
Prematurity
Premature infants, particularly those of low birthweight and with respiratory disease, have delayed closure. It may be an asymptomatic finding or the infant may develop cardiac failure if the shunt is large. Chest radiographs may be normal or may show pulmonary plethora. Echocardiography will demonstrate the shunt and may show left atrial, left ventricle and PDA enlargement.
Term infants
A patent ductus arteriosus can be an isolated finding. Presentation depends on duct size. Small ducts may be detected as an asymptomatic murmur. With large shunts, the child may have poor weight gain and cardiac failure. Left untreated, there may be development of pulmonary hypertension with shunt reversal.
Imaging
Echocardiography
Initial imaging modality of choice.
• Will demonstrate the shunt and may show left atrial, left ventricle and PDA enlargement.
Differential diagnosis
• Other causes of left to right shunt (VSD, ASD, AVSD).
• Persistent fetal circulation.
Tetralogy of Fallot
One of the commoner causes of cyanotic congenital heart disease that presents beyond the neonatal period.
It is an association of:
• right ventricular outflow obstruction (either subpulmonic or infundibular).
• over-riding aorta.
• VSD (usually perimembranous).
• right ventricular hypertrophy.
This creates an outflow obstruction to the right ventricle with an initially normal size heart and reduced pulmonary vascularity. It is associated with a right-sided aortic arch, aberrant subclavian artery, anomalies of the coronary arteries and trisomy 21.
Clinical presentation
Varying degrees of cyanosis. In older children cyanotic episodes are relieved by squatting. The child may be clubbed, have decreased exercise tolerance, arrhythmias, strokes due to paradoxical emboli and endocarditis.
Imaging findings
Radiographs
• Normal-sized heart at birth.
• Develops a boot-shaped heart due to concavity of the pulmonary bay and an elevated apex due to right ventricular hypertrophy.
• Right aortic arch (25%).
• Pulmonary vascularity is reduced or can be disorganized.
Differential diagnosis
• Pulmonary atresia with VSD and aorto–pulmonary collaterals.
• Pulmonary atresia with intact ventricular septum and cardiomegaly with atrial enlargement at birth.
• Tricuspid atresia.
Management and prognosis
• Palliative shunt (Blalock–Taussig shunt).
• Complete repair.
• Pulmonary valve or conduit replacement in adult life after early complete repair.
Fig. 2.25AP radiograph showing a classic ‘boot-shaped’ heart due to ventricular enlargement with concave pulmonary artery segment with pulmonary oligaemia.
Vascular rings
In early fetal development each of the six branchial arches is supplied by its own aortic arch. Most of these obliterate. Failure of this can lead to vascular anomalies which encircle and compress the airway and oesophagus causing stridor, respiratory distress or feeding difficulties. The location and pattern of tracheal and oesophageal indentation is useful in determining the cause of compression.
Double aortic arch
Both the left and right aortic arch is present (R>L). They unite posteriorly to form the descending aorta which is usually left-sided. The right arch is usually larger than the left. The right subclavian and common carotid artery arise from the right arch. The left subclavian and occasionally the left common carotid arise from the left arch.
Right aortic arch, aberrant left subclavian and ligamentum arteriosus (ductus)
The right aortic arch encircles the trachea. The aberrant subclavian passes posterior to the trachea with the ligamentum (or ductus) passing to the more anterior left pulmonary artery.
Aberrant right subclavian artery
Common incidental finding. Posterior indentation of the oesophagus on a barium swallow. Most children are treated conservatively.
Pulmonary sling
If the left pulmonary artery originates from the right pulmonary artery, it will pass posteriorly between the trachea and oesophagus and can cause compression of the right main bronchus which may in turn lead to hyperinflation of the right lung. A barium swallow will show the abnormal left pulmonary artery lying posterior to the trachea but indenting the oesophagus anteriorly.
Aortic coarctation
Narrowing of the aorta obstructs normal arterial blood flow and increases left ventricular pressure. The coarctation may be pre-ductal (infantile), juxta or post-ductal or abdominal. It is associated with a bicuspid aortic valve, VSD and PDA. This is an acyanotic disorder, with a normal-size heart and pulmonary vasculature.
Clinical presentation
Often asymptomatic, in severe cases it can lead to congestive heart failure, hypertension and left ventricular hypertrophy. There is a differential in blood pressure between the arms and legs.
Imaging findings
Radiographs
• Rib notching (over 5 years of age), due to collateral circulation.
• Post-stenotic dilatation of the descending aorta.
• Rounded cardiac apex due to left ventricular hypertrophy.
MRI
• Oblique sagittal plane (black blood images) will show the level and size of the coarctation.
• Perpendicular images will assess cross-sectional diameter.
• Cine images will show a jet of blood across the coarctation.
• Numerous collateral vessels across the chest wall and ribs.
• Gradient assessment across the coarctation.
Scimitar syndrome
This is hypoplasia of the right lung with an abnormal connection between the right pulmonary vein and IVC. There is often an anomalous arterial connection between the right lung base and systemic circulation. As a consequence venous flow from the right lung is returned to the right atrium, creating a left to right shunt and causing volume overload. This is an acyanotic condition with increased pulmonary vascularity.
Clinical presentation
Depends on the size of the left to right shunt. In severe cases presentation is in the newborn with congestive heart failure and pulmonary hypertension. In milder cases it is in the older child, and is associated with recurrent infections of the right lung base.
Imaging findings
Radiographs
• Curved vessel at the right medial cardiophrenic angle which increases in size towards the diaphragm (like a ‘curved sword’—scimitar).
• Hypoplasia of the right lung.
• Prominent right atrium.
• Increased pulmonary vascularity.
Differential diagnosis
• Pulmonary sequestration.
• Anomalous pulmonary venous connections.
• Pulmonary hypoplasia.
Management and prognosis
Embolization of systemic arterial supply. Surgical repair of severe shunts to avoid pulmonary hypertension.
Uncommon congenital cardiac conditions
The following conditions, while very serious and potentially life-threatening, are relatively rare. Typically the diagnosis is made on clinical findings and echocardiography. The classical radiographic findings may not be present as these are often associated with untreated disease.
D-Transposition of the great arteries
This is less common than tetralogy of Fallot, but the most common cause of cyanosis in the neonate. The great vessels arise off the inappropriate ventricle. This is incompatible with life unless there is a connection between the pulmonary and systemic circulation: through a patent foramen ovale, a ventricular septal defect or patent ductus arteriosus.
Clinical presentation
Pulmonary atresia
This can occur with or without a VSD, the presence of which is used to classify the lesion. Both types are characterised by the underdevelopment of the right ventricular outflow tract and pulmonary valve. There is extreme outflow obstruction with the entire cardiac output going into the dilated overriding ascending aorta. It presents with progressive cyanosis after birth, following closure of the ductus arteriosus, causing cardiomegaly.
Ebstein's anomaly
This is downward displacement of the septal and posterior leaflets of the tricuspid valve. It can be asymptomatic at birth with a normal-size heart (the heart can also be enlarged at birth), but it will cause cyanosis and severe cardiomegaly with normal to decreased pulmonary vasculature. It is associated with chronic right heart failure and arrhythmias.
Tricuspid atresia
Congenital absence or agenesis of the tricuspid valve. It is associated with a VSD and a right aortic arch. Neonates often present with cyanosis in the first 24hrs of life, but may present later in life with congestive heart failure. With a small VSD the heart is normal in size, when the VSD is large the heart is typically enlarged.
Truncus arteriosus
This is a common arterial trunk arising from the heart, giving rise to the aorta, pulmonary arteries and coronary arteries. Associated with a right-sided aortic arch, absent thymus and parathyroid glands (DiGeorge syndrome). It presents with increasing cyanosis and progressive congestive heart failure as the pulmonary vascular resistance falls due to shunt reversal and development of pulmonary hypertension.
Total anomalous pulmonary venous return (TAPVR)
This is failure of the connection between the pulmonary veins and the left atrium. There are three types:
• Type I: supracardiac TAPVR common pulmonary vein joins the left innominate vein.
• Type II: cardiac TAPVR common pulmonary vein joins the coronary sinus.
• Type III: infracardiac TAPVR common pulmonary vein joins the portal vein, ductus venosus or inferior vena cava.
Hypoplastic left heart syndrome
Anomalous origin of the left coronary artery
The left coronary artery arises from an abnormal position, most commonly from the pulmonary artery. It causes poor ventricular function and tortuous collateral coronary circulation. Presents in infancy with symptoms related to the degree of cardiac ischaemia such as irritability, wheezing or failure to thrive.