**8. Chest X-ray**

X-ray is integral part of the evaluation of a child with cardiac disease.

The x-ray helps in the evaluation of cardiomegaly, chamber size, and blood flow by looking at the pulmonary artery and venous markings. Lungs, spine, thorax and visceral situs are also evaluated using x-ray. For example the presence of aortic knuckle and gastric fundus on the same side is suggestive of corrected transposition.

The structures forming the margin of the heart on the right side are– SVC, aortic knuckle and RA and on the left side they are the pulmonary artery, left atrial appendage and LV.

Different conditions can have diagnostic X-ray features. TOF has a *' boot shaped'* heart, TGA has a '*egg on side'* heart and supracardiac TAPVC is associated with '*snow man sign'* the left vertical vein, the innominate vein and the right superior vena cava form the head of the snowman., Truncus, the dilated pulmonary artery particularly the right pulmonary artery produces the ' *comma or the water fall sig*n'. In Ebsteins anomaly there is cardiomegaly with a narrow pedicle, with '*Pencil line sharp'* cardiac borders.These classic appearances are not usually seen, though they are supportive evidences in broader clinical context.

#### **8.1. The assessment of pulmonary arterial and venous pressure using X-ray**

Pulmonary plethora – the presence of right descending pulmonary artery larger than the size of trachea is a sensitive sign of increased pulmonary blood flow. Other signs are prominent upper and lower zone vessels and vessels seen in the outer third of the lungs. Infants and children present with generalized mottling, due to increased pulmonary flow.

**Pulmonary arterial hypertension**: Is said to occur when the mean pulmonary artery pressure is > 20 mmHg,

In mild PAH – (20-29 mmHg) there is prominent pulmonary artery.

Moderate PAH- (30-49), the central vessels dilate further,

Severe PAH (50 mmHg) - there is central dilation with reduction in the calibre of peripheral vessels (peripheral pruning). The size of the pulmonary artery correlates with PAH, and it has been found that plethora correlates better with the degree of left to right shunt than cardio‐ megaly.

**Pulmonary venous hypertension** – normal 8-12 mm Hg, and gradual increase causes:


The presence of prominent aortic knuckle points to the presence of extra cardiac left to right shunt like PDA, Sinus of Valsalva rupture, Coronary arteriovenous fistula, or AP window. The absence points to intra- cardiac L-> R shunt like atrial septal defect and ventricular septal defect.

In addition to the above findings careful consideration should be given to lung parenchyma to look for any parenchymal patches and also the status of spine and bony thorax for complete preoperative assessment.
