FIG. 57-2. Pulmonary vascular congestion. Bilateral increased lung markings are present, particularly in the lower lung fields, with prominent interstitial lung markings. The pulmonary hila are also enlarged.
CARDIAC CHAMBER ENLARGEMENT Left Ventricle Increased workload by the left ventricle initially results in dilatation of the ventricle, but if it is sustained, hypertrophy of the left ventricular wall occurs. Hypertrophy is a normal response to increased workload. Chest x-ray findings at this time are usually normal. As the ventricle begins to fail, dilatation results, and the cardiothoracic ratio increases. The apex of the heart also becomes more rounded in appearance. The most marked increases in size of the left ventricle result from hypertension, aortic insufficiency, and cardiomyopathy. Pericardial effusion results in generalized cardiac enlargement
FIG. 57-3. Pericardial effusion. Generalized dilatation of the heart is present, with the cardiothoracic ratio measuring more than 50 percent. Although a similar cardiac silhouette would be present in patients with dilated cardiomyopathy, this patient had documented pericardial effusion.
Right Ventricle The right ventricle enlarges from processes that increase the work of this chamber, such as pulmonary diseases or pulmonary artery hypertension. Mitral valve disease will also eventually result in right ventricle enlargement. The outflow tract of the right ventricle enlarges first; chest x-ray findings are subtle but include straightening or convexity of the pulmonary artery segment below the aortic knob in the frontal view. Multichamber enlargement is frequent, so that the relative involvement of each cardiac chamber is not easily distinguished on chest x-ray.
Left Atrium Common cases of left atrial enlargement include mitral valve disease from rheumatic fever, or congenital defects resulting in left-to-right shunts. The normal left atrium is posterior and does not form any portion of the cardiac silhouette in a normal patient. Moderate enlargement causes the left atrial appendage to become larger and causes a bulge or straightening of the left cardiac border below the pulmonary artery segment. Further enlargement may cause the right-sided border of the left atrium to extend beyond the normal upper aspect of the right atrium and superior vena cava. A double cardiac border is seen on the frontal view on the right side. If the left atrial enlargement is less extreme, a double border may still be seen because of the increased radiodensity of the left atrium. On the lateral view, the upper posterior border of the cardiac silhouette projects more posteriorly than normal.
Right Atrium Enlargement of the right atrium causes enlargement of the lower right cardiac contour with increased convexity. Diseases resulting in right atrial enlargement include atrial septal defect, tricuspid stenosis and insufficiency, and right ventricular failure. In multichamber disease, right atrial enlargement is not separately identified.
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