Great Vessels

The roentgen appearance of the great vessels often provides valuable information for the diagnosis of heart disease.2-3'18'19 For example, selective dilatation of the ascending aorta is the hallmark of valvular aortic stenosis (Fig. 12-13); generalized dilatation of the entire thoracic aorta (Fig. 12-14), on the other hand, favors the diagnosis of aortic regurgitation, systemic hypertension, or both, depending on the size of the left ventricle. A larger left ventricle is associated with aortic regurgitation because of volume overload. In atrial septal defect and mitral stenosis, the pulmonary trunk is quite large, and the aortic knob is usually small (see BhH; Figs. 12-2B and B+fl; 12-3/1). This is explained on the basis of a leftward cardiac rotation that occurs when an enlarged right ventricle coexists with a normal-sized left ventricle. When the heart rotates to the left, the aorta folds on itself in the midline and becomes inconspicuous. Meanwhile, the pulmonary trunk is brought laterally and looks larger than it actually is. Aortic aneurysm (Fig. 12-15) and dissection frequently are associated with hypertensive and atherosclerotic disorders.

Congenital Defects The Aortic Valve
Figure 12-13: A 17-year-old boy with congenital aortic valve stenosis. Note dilatation of the ascending aorta, increased convexity of the left ventricle, and normal pulmonary vascularity. The systolic aortic pressure gradient was 100 mmHg.
Great Vessels Prominence

Figure 12-14: A 45-year-old man with Marfan's syndrome, severe aortic regurgitation, and proximal aortic dissection into the pericardial cavity. A. Posteroanterior view shows a huge left ventricular and aneurysmal dilatation of the ascending aorta. There is no sign of heart failure. B. Lateral view shows a small pericardial effusion (arrow).

Great Vessels Prominence

Figure 12-15: Posteroanterior view of a 77-year-old man shows a huge descending aortic aneurysm

Figure 12-15: Posteroanterior view of a 77-year-old man shows a huge descending aortic aneurysm

As already mentioned, prominence of the pulmonary trunk is a reliable secondary sign of right ventricular enlargement (Fig. 12-16; also see B+fl; Fig. 12-2B), with the following exceptions: (1) tetralogy of Fallot with right ventricular hypertrophy but pulmonary trunk hypoplasia, (2) idiopathic dilatation of the pulmonary artery, (3) patent ductus arteriosus with dilated pulmonary trunk but normal right ventricle, and (4) straight-back syndrome, pectus excavatum, and scoliosis with narrowed anteroposterior diameter of the chest. Under the latter conditions, the heart is compressed, displaced, and rotated to the left, giving rise to a falsely enlarged pulmonary artery.

Great Vessels Prominence
Figure 12-16: A 37-year-old woman with congenital valvular pulmonary stenosis. Note enlarged pulmonary trunk and left pulmonary artery versus diminished right pulmonary artery. Also note increased pulmonary blood flow on the left side and decreased pulmonary blood flow on the right side.

In coarctation of the aorta, the engorged aortic knob and the poststenotic dilatation of the descending aorta may cause a "3 sign" on the aorta and an "E sign" on the barium-filled esophagus, both depicting the site of coarctation6 (see Fig. 12-lQ.

The abnormal size and distribution of both the pulmonary and systemic veins are important clues to the presence of certain conditions, e.g., anomalous pulmonary venous connections, pulmonary arteriovenous fistulas, pulmonary varix, persistent left superior vena cava, and interruption of inferior vena cava with azygos continuation (see Fig. 12-4).

The significance of aortic arch anomalies is discussed under "Statistical Guidance," below. MEDIASTINAL STRUCTURES

The mediastinal organs frequently are affected by the cardiovascular structures because of their close spatial interrelationships. An enlarged left atrium not only displaces the esophagus (see Fig. 12-JXB+iH; E) and the descending aorta but also elevates and compresses the left mainstem bronchus. A double aortic arch may compress both the trachea and the esophagus. On the other hand, malignant processes may invade the heart and great vessels, causing cardiac tamponade or the superior vena cava syndrome, for example. Usually, these mediastinal changes are evident on the chest roentgenogram and should be recognized promptly.18-22

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