Chest X-ray In Pediatric Cardiology

 A chest X-ray aids in the diagnosis of the underlying disease by revealing information about the patient's diaphragmatic status overall, cardiac size, cardiac shadow abnormalities, pulmonary blood flow, individual chamber abnormalities, and the state of the pulmonary parenchyma.

Views Taken

The optimal view to adopt is the PA view. It offers the most lucid perspective for assessing the child's cardiac health. This is not possible without the use of complex maneuvers with toddlers under three years old.
The film needs to be erected over the front of the body in order to obtain the X-ray result. The PA view is found to be superior to the AP view because the scapula will overlap the lung area. Even if it might not be the case, a patient may perceive illusory cardiomegaly if there is a modest elevation in the cardio-thoracic ratio. Nonetheless, small children under the age of two are better suited for AP view because it can also be performed in a supine position.

In situations like right ventricular hypertrophy, the lateral view is helpful, although being a little trickier to use.

The images provided are the lateral view, AP view, and PA view, respectively.  The scapulae are not entering the field in image A, but they are in image B.  In picture B, the clavicle is visible above the apices.
The posterior ribs are more visible in image A than in image B.

 The diaphragm is positioned more sharply in image B than in image A.
The X-ray's PA view is displayed in image A, while its AP view is displayed in image B. The lateral perspective of the X-ray is displayed in the third image, which is an uncommon method. Only when conditions like isolated LV enlargement, RV enlargement, and the increasingly common lateral view echocardiogram are virtually completely avoided is it performed.

Cardiac Size

The size of the heart is the most crucial piece of information obtained from an X-ray.  The ratio of the heart's maximum internal thoracic diameter to its maximum transverse diameter is known as the cardiothoracic ratio.  If the number is more than 50%, we consider the patient to have cardiomegaly.  Because it might be somewhat inflated on AP view, it might not be correct. 

Although it is not a standard reference, some studies suggest that the cut-off value when the AP view is taken should be approximately 55%.

The sternal shadow or the X-ray's center are used to draw a vertical line.
Using this, we get the maximum diameter, denoted as A, on the right side.  Next, the left side's maximum diameter is measured and assigned the letter B.  The heart's maximal potential diameter is represented by A+B.. Since C is assumed to be at its maximum in the thoracic cage, the formula for the CT ratio is (A+B)/C.

For cardiomegaly, a lateral X-ray is obtained in addition to the CT ratio; this image identifies the isolated RV enlargement. While ECG is better at detecting pressure overload, CXR is better at detecting volume overload.
In cases of pressure overload, concentric hypertrophy happens as a result of an increase in pressure. The heart muscle cannot migrate outward; instead, it thickens inside. A CXR will not readily measure this remodelling. However, because of the increased cardiac muscle mass, you will detect either left- or right-sided excess division characteristics on an ECG. Therefore, an ECG is a superior way to show pressure overload.

In patients with a flat chest or narrow AP diameter, a PA film may mistakenly reveal cardiomegaly. Unless certain maneuvers are employed, a CXR on a child younger than three years old is more likely to be an AP view than a PA one.

Normal Cardiac Silhouette

This is a picture of a normal cardiac silhouette in PA view. The right heart border is formed by structures like the right atrium and superior vena cava. The left heart border is formed by structures like the left ventricle, pulmonary artery, aortic knob, and occasionally the left atrial appendage. 

The left ventricle and auricle comprise the posterior segment in the lateral view, whereas the right ventricle and a few segments of the pulmonary artery form the anterior segment. Above the diaphragm's dome, the left ventricle meets or overlaps the inferior vena cava in a typical cardiac profile.

Abnormal Cardiac Silhouette

Boot-Shaped Heart

Right ventricular hypertrophy, which causes the apex to be turned upward, RV outflow obstruction from reduced pulmonary blood flow, and hypoplastic pulmonary artery segment, which results in a concavity, are the causes of a boot-shaped heart. It is also known as coeur-en-sabot, and the Fallot tetralogy is where it is most frequently observed. In tricuspid atresia, the apex's overturning is not as noticeable. 

Q. A CXR done in a cyanotic infant showed the typical boot-shaped heart. The next investigation will be helpful to see if it's TOF or Tricuspid Atresia if echocardiography is not available immediately.

As soon as a CXR reveals a heart that resembles a boot, echocardiography is carried out.  An ECG is done since it is unavailable.
Tetralogy of Fallot is the most likely diagnosis if the ECG exhibits RVH symptoms; if LVH features are observed, tricuspid atresia is the most likely diagnosis.

Egg-on String Appearance

The most typical occurrence of this condition, also known as the egg-on-side look or egg-shaped heart, occurs in dextroposed TGA.  Cause: An improper relationship between the great arteries results in a small upper pedicle with convexity, and a diminished or missing thymic shadow. These characteristics are linked to an elevated PBF.

Snowman Appearance

The figure of eight look, also known as the cottage loaf appearance, is observed in the supra-cardiac variant of TAPVC. The left innominate vein, also known as the left vertical vein, is prominent, and the superior vena cava is dilated.

Individual Cardiac Chambers

Left Atrial Enlargement

The lateral view is the best way to observe the modest expansion of the LA, which causes the LA border to protrude posteriorly.  The following are indications of LA enlargement on PA view:  A double density sign indicates a markedly enlarged left atrium. It finishes just before the right heart border, forming a partial shadow. Thus, there are two cardiac shadows on the right side. Additionally, the left mainstem bronchus will be elevated, which is uncommon in young infants, and there will be a noticeable left atrial appendage on the left heart border.

Right Atrial Enlargement

The lower heart border appears more prominently when viewed in PA view.Because false positives and negatives might occasionally be observed, it is not particularly helpful.

Left Ventricular Enlargement

The lower posterior cardiac boundary is pushed farther posteriorly and meets the IVC line below the diaphragm level on the lateral view. • The apex is shifted downward and laterally on the PA view.

Right Ventricular Enlargement

It is best recognized in the lateral view in which it manifests by filling of the retrosternal space.

Size And Abnormalities In The Great Vessels

Prominent Main Pulmonary Artery

Increased PBF situations such as ASD and VSD are associated with a convexity formed by the primary pulmonary artery.  Post-stenotic dilatation, such as pulmonary valvular stenosis, may be the cause.

Hypoplastic Pulmonary Artery

Patients with reduced peripheral blood flow (PBF), such as those with tetralogy of Fallot, are affected. The primary pulmonary artery has a concavity.

Aortic Dilatation

A convexity will form on the right side of the heart if the aortic arch is dilatation. Aortic knuckle formation is characterized by a convexity in the upper left corner and is observed in circumstances such as post-stenotic dilatation in aortic valvular stenosis, coarctation of the aorta, Marfan's syndrome, and PDA.

A three-shaped figure may be seen in this figure.  There is upper and lower dilatation (convexities) and stenosis (concavity), which is occurring.  The coarctation of the aorta (COA) displays this.

Pulmonary Blood Flow

Raised PBF is also known as pulmonary plethora, and lower PBF is known as pulmonary oligemia. • Pulmonary blood flow can be either raised or decreased.

Pulmonary Plethora

The radiological indicators include the expansion of the left or right pulmonary artery, pronounced vascular patterns, and vascular patterns that reach the peripheral 1/3 of the lung fields in addition to the upper 2/3 of the lung fields. 

The lung is segmented into three sections, beginning at the hilum. The central area and the hilar third may have vascular marks. • The exterior diameter of the right PA shown in the right hilum is wider than the internal diameter of the trachea; if these arteries may go beyond the middle area, it is indicative of greater pulmonary blood flow.

Pulmonary Oligemia

Less than one-third of the lung fields will have vascular markings, small and thin pulmonary arteries, dark or black lung fields, and a small hilum are among the radiological markers.

Kerley B Lines

The source of these short transverse strips of increased density is pulmonary venous congestion-related interstitial edema of the interlobular septa and engorged lymphatics. They are most visible in the costophrenic sulci. It is an indication of pulmonary venous congestion; abrupt left ventricular failure and mitral stenosis are two such conditions.

Also Read: Rapid Acquisition Of Key Concepts Cardiovascular

OTHER INFORMATION OBTAINED

Inferior Rib Notching

 It is a characteristic of aortic coarctation. The third through eighth ribs are affected.  The inferior surface of the ribs has erosions.  The posterior and anterior intercostal vessels' collateral development is the cause of it.
The formation of collaterals between branches of the anterior intercostal arteries (provided by the ascending aorta) and branches of the posterior intercostal arteries (supplied by the descending aorta) causes inferior rib notching.
Since the anterior and posterior intercostal arteries originate from the ascending aorta in the first two intercostal spaces, no collaterals are required, thus the first two ribs are not affected.

Dextrocardia With Situs Inversus

The two diaphragm domes in a normal person are not at the same level; in a normal person, the cardiac shadow occupies one-third of the right side and two-thirds of the left side of the thoracic cavity. The apex points towards the left side, and if it points towards the right, it is referred to as dextrocardia. Compared to the left, the right-sided dome is somewhat higher. The left dome is supported by the cardiac apex, which prevents the dome from rising. 

 A normal individual has a stomach bubble on the left side and a hepatic shadow on the right. The apex on that side is slightly on the lower side. 

The situation is inverted in situs inversus. The heart's apex is oriented to the right. Additionally, the diaphragmatic domes will shift in position, and the stomach bubble will shift to the right. Because of the cardiac shadow, the diaphragm's dome is lowered on the right side.

Also Read: Fetal Circulation And Transition To Neonatal Circulation

Heterotaxia Syndrome

 It is suspected on CXR if there is a left-sided stomach bubble with a right-sided cardiac apex, or a right-sided stomach bubble with a normal left-sided cardiac apex.  Many people may have a mid-line liver associated with the absence of the spleen and Polysplenia abnormality. 

There is an incomplete rotation of the body's axis. 
Erroneous Cardiomegaly Sign
In the event that the chest's transverse diameter rises in response to the thorax's flattening of its AP diameter. It can provide the erroneous appearance that a patient has cardiomegaly. Patients with pectus excavatum are affected.

Right-Sided Aortic Arch

It is observed in diseases such as truncus arteriosus and tetralogy of Fallot; in a healthy individual, the left-sided aortic knob is present normally.  When the aortic knuckle is located on the side opposite the air-filled airway, it may indicate a right-sided aortic arch (as seen in the second figure above).

Water-Bottle Sign

It is also called the flask-shaped heart.It is seen in patients with massive pericardial effusions.

Thymic Shadow

It creates a traditional sign known as the sail sign with a wavy border, which is caused by an indentation made by ribs known as the Mulvey wave sign.  The expanded thymic shadow is absent in DiGeorge syndrome; it is observed in normal variations, thymic hyperplasia, tumors, leukemia, lymphoma, and LCH; in newborns with cyanotic CHD, such as d-TGA, and in individuals with severe CCF, it diminishes or narrows.

Spinnaker Sail Sign

This anomalous finding, often known as the "angel wing sign," describes the thymus as being outlined by air, with each lobe pushed laterally and resembling spinnaker sails.  In newborns and young children, it is an indication of pneumomediastinum.

Scimitar Syndrome

 Observed in PAPVR of the right middle or lower lung lobes, there is a scimitar-shaped vertical shadow along the lower right heart boundary.
It is linked to hypoplastic right PA, sequestration of the right lung, ASD, and right lung hypoplasia. • The pulmonary venous blood empties into the inferior vena cava.

Also Read: Arrhythmias in Children : NEET SS Pediatrics

RARE SIGNS

Box-Shaped Heart

It is a condition where the heart is highly enlarged due to right atrium involvement. It is seen in patients with Ebstein’s anomaly.

Other Named Signs

Patients with an atrial septal defect may exhibit a jug-handle look.
Patients with dilated cardiomyopathy have the globular heart.  Patients with pulmonary hypertension may experience peripheral pruning of the pulmonary arteries.  Patients with tricuspid atresia may exhibit the sitting duck sign, a variation of the boot-shaped sign (shown in the upper figure).

Hope you found this blog helpful for your NEET SS Pediatrics Cardiology preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.