Chest Radiography

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Chapter 6 Chest Radiography

Skilled interpretation of chest radiographs is central to the diagnosis and treatment of patients in the cardiothoracic intensive care unit (ICU). In this chapter the common abnormalities of chest radiographs that are encountered in cardiac surgery patients are reviewed. Where appropriate, indications for computed tomography (CT) or ultrasound scanning of the chest are discussed. Before attempting to interpret abnormalities, it is essential to appreciate the findings of the normal chest radiograph and to have a systematic approach to reviewing films. These topics are discussed first.

NORMAL CHEST RADIOGRAPH

Types of Chest Radiographs

Two types of frontal chest radiographs may be obtained:

Normal Structures on the Erect Posteroanterior Chest Radiograph

Normal structures identified on the PA and left lateral radiographs are shown in Figs. 6-1 and 6-2.

PREOPERATIVE CHEST RADIOGRAPH

Virtually all patients presenting for cardiac or thoracic surgery receive erect PA and left lateral chest radiographs preoperatively.

Cardiac Chamber Enlargement

The PA and lateral chest radiographs can suggest specific valvular or chamber abnormalities.

Cardiac Calcification

Calcification can be present in many cardiac structures, including the pericardium, the cardiac valves, and the walls of the cardiac chambers, as well as in organized thrombus and in the coronary arteries due to atheroma. Aortic valve calcification can be seen on the lateral radiograph as a ring of calcification projected centrally over the heart (Fig. 6-4). The presence of aortic valve calcification implies stenosis. Mitral annular calcification is common in patients more than 70 years of age; it appears as a C-shaped ring near the posterior and inferior aspects of the heart on the lateral radiograph (Fig. 6-5). Mitral annular calcification does not imply functional impairment of the mitral valve. In contrast, calcification of the mitral leaflets is associated with rheumatic heart disease and usually indicates significant mitral valve dysfunction, usually stenosis. Mitral leaflet calcification is seen in the same region as annular calcification but is punctate and lacks the C-shape of the more benign annular calcification. The positions of each of the four heart valves on frontal and lateral radiographs are shown in Figure 6-6.

image

Figure 6.6 A and B, Frontal and lateral radiographs of a patient with four prosthetic heart valves. A mechanical prosthesis has been inserted in each of the four heart valve positions.

(Reproduced from Bijl M, van den Brink RB: Images in clinical medicine: four artificial heart valves. N Engl J Med 353:712, 2005. Copyright © 2005 Massachusetts Medical Society.)

Pulmonary Vascularity

Pulmonary Venous Hypertension and Pulmonary Edema

Three changes in pulmonary vascularity occur in patients with raised left atrial pressure:

2. Interstitial edema. Increased interstitial fluid within the pulmonary parenchyma results in the thickening of the interlobular septa (Kerley A and B lines), in peribronchial thickening, and in fuzziness around vessels. Kerley B lines are seen as horizontal lines perpendicular to the chest wall peripherally, in the mid to lower zones, and measuring 1 to 3 mm in thickness (Fig. 6-7). Kerley A lines are thickened interlobular septa that are seen within the more central lung, passing obliquely toward the pulmonary hilum. Septal lines that persist beyond resolution of heart failure may occur due to hemosiderin or fibrin deposition within the septa.

On a supine chest radiograph, the gravitational changes of pulmonary venous hypertension are not identified, but the signs of interstitial and alveolar edema are unchanged. Pleural fluid often coexists with interstitial or alveolar edema.

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