Aortic and pulmonary vascular abnormalities on CXR
Aortic abnormalities on CXR
Right aortic arch: Side of aortic arch is recognized by the indentation of tracheal air shadow. Normally it is on the left side as it is left aortic arch. In right aortic arch, the indentation is on the right side. Right aortic arch may be seen in tetralogy of Fallot and truncus arteriosus.
Ascending aorta: Ascending aorta is seen well just above the right atrial contour on the right cardiac border when it is dilated. Dilated ascending aorta can occur in:
- Post stenotic dilatation in aortic stenosis
- Annuloaortic ectasia in Marfan syndrome
- Ascending aortic aneurysm
Aortic knuckle: Intimal calcification seen as a crescentic shadow is common in older individuals on the lateral aspect of aortic knuckle. The distance between the intimal calcification and the outer border of the aortic knuckle is increased in aortic dissection (typically more than 1 cm). This is known as calcium sign in aortic dissection.
Descending aorta: Normally descending aorta is just visible behind the cardiac outline extending slightly beyond the left border of spine. It becomes prominent and tortuous in the elderly and when there is an aneurysm.
Coarctation of aorta: In coarctation of aorta, figure 3 sign is composed of the prestenotic dilatation of aorta and left subclavian, indentation at the coarctation site (tuck) and the post stenotic dilatation. Reverse 3 or E sign is a mirror image of this pattern seen as indentation on the barium filled esophagus on barium swallow. Rib notching seen in coarctation of aorta has been discussed in the preceding section.
Pulmonary vessels on CXR
Pulmonary vessels are more prominent in the lower zones due to the effect of gravity. In pulmonary venous hypertension as in mitral stenosis, upper lobe vessels are more prominent, due to dilatation of pulmonary veins. There are several names for these prominent upper lobe vessels:
- Antler sign
- Cephalization
- Redistribution
- Inverted moustache sign
Main pulmonary artery: Main pulmonary artery segment is concave normally. It bulges out when it is dilated as occurs in:
- Pulmonary arterial hypertension
- Post stenotic dilatation in pulmonary stenosis
Main pulmonary artery segment can be prominent without pulmonary arterial hypertension in:
- Idiopathic dilatation of pulmonary artery
- Partial absence of left pericardium
- Absent pulmonary valve, an association of tetralogy of Fallot
Right pulmonary artery: Right descending pulmonary artery is seen lateral to the right bronchial air shadow. It can be dilated in pulmonary arterial hypertension and absent pulmonary valve syndrome with or without tetralogy of Fallot. Abrupt cut off is seen in pulmonary embolism (knuckle sign). Along with this, right descending pulmonary artery becomes prominent (Palla’s sign). An area of focal oligemia due to embolic obstruction of a large pulmonary branch is known as Westermark’s sign. Right pulmonary artery is not dilated in post stenotic dilatation of pulmonary artery and idiopathic dilatation of pulmonary artery.
Left pulmonary artery: Left pulmonary artery descends behind the heart shadow, parallel to the descending aorta. It is dilated in pulmonary arterial hypertension, absent pulmonary valve syndrome and post stenotic dilatation of pulmonary stenosis. Left pulmonary artery is dilated in post stenotic dilatation because the stenotic jet is directed from the main pulmonary artery to the left pulmonary artery as it is in line with it, while right pulmonary artery is oriented transversely in the mediastinum, when it courses to the right lung. Left pulmonary artery is not dilated in idiopathic dilatation of pulmonary artery.
Scimitar sign: Anomalous drainage of the right pulmonary vein is seen as a curved vascular shadow resembling the Turkish sword. Scimitar syndrome has in addition a hypoplastic right lower lobe of the lung, small right pulmonary artery, systemic arterial supply to the sequestrated lobe and eventration of right hemidiaphragm.
Figure of 8 sign: Figure of 8 sign, also known as cottage loaf and snow man in snow storm are described in supra cardiac variety of total anomalous pulmonary venous connection/drainage (TAPVC/D). The lower part of the figure of 8 is the cardiac shadow while the upper part is constituted by a combination of the vertical vein, dilated brachiocephalic vein and superior vena cava. Vertical vein which ascends up the left side of the spine, receives all the pulmonary venous drainage and in turn empties into the left brachiocephalic vein. The congested lung if there is pulmonary venous congestion gives the appearance of ‘snow storm’ for the snow man in snow storm sign.