Left Ventricle Enlargement
The left ventricle (LV) is ellipsoid in shape. It lies behind, and to the left of the right ventricle. Its long axis lies at about 45 degrees to the vertical. When this chamber enlarges, all its diameters increase, but particularly its long axis. This results in a downward displacement of the apex. On the PA view this causes the left ventricular border to elongate, and move downwards or outwardsn or both. On the lateral view, the chamber may extend posterior to the esophagus. Its posteroinferior border may project behind the IVC at a point 2 cm above the diaphragm (Hoffman Rigler sign). The changes in cardiac contour produced by left ventricular enlargement on all four views are shown in Fig.
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| LV Enlargement |
Right Ventricle Enlargement
The right ventricle (RV) is roughly triangular in shape on the PA view, with a near vertical base-apex axis. When this chamber enlarges ,there is broadening of its triangular shape. Two patterns of enlargement are generally seen. A bulge may be seen along the left heart border above the apex, formed by the enlarged ventricle. The change in contour could also be due to the enlarged RV elevating a normal LV. This causes a long prominent upper contour above the apex,and a second shorter contour turning medially below the apex. On the lateral view, an enlarged RV fills in the retrosternal clear space, owing to its anterior location.
The right ventricle (RV) is roughly triangular in shape on the PA view, with a near vertical base-apex axis. When this chamber enlarges ,there is broadening of its triangular shape. Two patterns of enlargement are generally seen. A bulge may be seen along the left heart border above the apex, formed by the enlarged ventricle. The change in contour could also be due to the enlarged RV elevating a normal LV. This causes a long prominent upper contour above the apex,and a second shorter contour turning medially below the apex. On the lateral view, an enlarged RV fills in the retrosternal clear space, owing to its anterior location.
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| RV Enlargement |
Left Atrial Enlargement
This chamber is oval in the frontal projection and flattened in lateral projection. On the PA view,its appendage makes a small contribution to the left heart border. The left atrium (LA) may enlarge in many directions. Rightward enlargement is seen as increased density, producing a convex border overlying or to the right of the right heart border. This could mimic a dilated aortic root. When the chamber enlarges to the left, it causes straightening or convexity of the left heart border in the region of the left atrial appendage. Posterior enlargement of the LA is seen as increased central heart density on a PA view and as posterior displacement of the left atrial border and the pulmonary veins on the lateral view. Superior enlargement is manifested as widening of the carinal angle, which is usually less than 90 degrees. Occasionally, the LA may be aneurysmally dilated. On the PA view, the right border may approach the right chest wall, with a markedly enlarged appendage on the left, and splaying of the carinal angle to 180 degrees. On the lateral view, the massively enlarged LA is convex posteriorly, forming the entire heart border.Fig. shows the changes in cardiac contour that result from LA enlargement on four views.
This chamber is oval in the frontal projection and flattened in lateral projection. On the PA view,its appendage makes a small contribution to the left heart border. The left atrium (LA) may enlarge in many directions. Rightward enlargement is seen as increased density, producing a convex border overlying or to the right of the right heart border. This could mimic a dilated aortic root. When the chamber enlarges to the left, it causes straightening or convexity of the left heart border in the region of the left atrial appendage. Posterior enlargement of the LA is seen as increased central heart density on a PA view and as posterior displacement of the left atrial border and the pulmonary veins on the lateral view. Superior enlargement is manifested as widening of the carinal angle, which is usually less than 90 degrees. Occasionally, the LA may be aneurysmally dilated. On the PA view, the right border may approach the right chest wall, with a markedly enlarged appendage on the left, and splaying of the carinal angle to 180 degrees. On the lateral view, the massively enlarged LA is convex posteriorly, forming the entire heart border.Fig. shows the changes in cardiac contour that result from LA enlargement on four views.
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| LA Enlargement |
Right Atrial Enlargement
The right atrium (RA) is a globular chamber, forming the right heart border on the PA view. On the PA view, the border of the enlarged RA should project to the right and its radius of curvature increases. This may cause its border to be atleast half as long as the total height of the right mediastinal border. These changes on the CXR may not be seen, if the heart is positioned leftward or if the chamber enlargement is more in the AP dimension. Fig. 4.10 shows results of RA enlargement.
The right atrium (RA) is a globular chamber, forming the right heart border on the PA view. On the PA view, the border of the enlarged RA should project to the right and its radius of curvature increases. This may cause its border to be atleast half as long as the total height of the right mediastinal border. These changes on the CXR may not be seen, if the heart is positioned leftward or if the chamber enlargement is more in the AP dimension. Fig. 4.10 shows results of RA enlargement.
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| RA Enlargement |
Pulmonary Artery Enlargement
On the PA view, the pulmonary trunk is border forming for a short distance between the aortic knuckle and the left atrial appendage. In children and young adults, (especially women), it often has a convex contour which flattens and reaches the adult pattern by the age of 20 years. On the lateral view, the pulmonary trunk may form the posterior margin of the retrosternal space inferiorly.When the pulmonary conus enlarges, it forms a smooth convexity in the expected position on the PA view, and encroaches on the lower portion of the retrosternal clear space on the lateral view.On the PA view, nodes or masses at the left hilum or adjacent mediastinum may simulate this appearance. Focal post stenotic dilatation of the pulmonary artery tends to involve the roof of the vessel, and is thus relatively high-placed.
Aortic Enlargement
Ascending Aorta: The ascending aorta, along with the SVC forms a portion of the right cardiac border on the PA view. After the age of about 40 years, the ascending aorta may project to the right beyond the SVC. It is often difficult to differentiate age related elongation of the ascending limb from dilatation. On the lateral view, an enlarged ascending limb may encroach on the retrosternal clear space.
Arch: The arch crosses from right to left in front of the trachea and then arches over and behind the left main bronchus, where it lies just to the left of the midline. On the PA view, the aortic knuckle is formed by the distal part of the arch. Again, above the age of 40, the knuckle may be displaced upwards and leftwards.
Descending Aorta: The descending aorta begins at the level of the fourth thoracic vertebra. It is defined through the cardiac shadow on the CXR, as it lies on the anterior aspect of the thoracic vertebral bodies, just to the left of the midline. Lengthening with age may also affect this portion of the aorta, which may resemble an aneurysm. A tortuous aorta may lie to the right of the spine.
In systemic hypertension, the ascending aorta and arch may be dilated. Post stenotic dilatation of the ascending aorta is seen in aortic stenosis. More diffuse dilatation of the ascending limb, arch and descending aorta is usually seen in aortic regurgitation. A small aortic knuckle may be seen in ASD, severe mitral stenosis and supravalvar stenosis.
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