CALCIFICATION

Most calcifications involving the heart occur in cardiac structures as a result of inflammatory or necrotic processes (or both) or degenerative disease. Because the calcific deposits have greater radiodensity than cardiac tissues do, they can often be seen within the cardiac silhouette.

The aortic and mitral valves abut each other, both inserting on the central fibrous tendon of the heart. On a frontal chest film, the two valves lie next to each other in the midportion of the cardiac silhouette, to the left of the spine ( Fig. 51-7A ), the aortic valve being slightly higher. It is often difficult to determine which valve is calcified in this view. They can be separated by fluoroscopy because the aortic valve tends to move in a vertical direction as the heart beats whereas the motion of the mitral valve approximates the horizontal. This distinction can also be made accurately from the lateral chest film. If a line is drawn from the left main bronchus, seen as a dark circular shadow over the lower end of the trachea, to the anterior costophrenic angle, the mitral valve lies below the line and the aortic valve is above it ( Fig. 51-7B ).

FIGURE 51-7  Location of the mitral and aortic valves. Both the mitral (M) and aortic (A) valves have been replaced by porcine heterografts. The circular stents indicate the location and tilt of each valve. A, Frontal projection. The two valves are normally in contact with each other, and it is difficult to separate them in the frontal projection. Furthermore, on a routinely exposed film, calcific deposits are not easily seen because of the overlapping shadows of the descending aorta (arrows) and the spine. B, Lateral projection. The valves can be differentiated on the lateral view by drawing a line from the left main bronchus (arrow) to the anterior costophrenic sulcus. The aortic valve lies above this line and the mitral valve below it.

In the United States, calcification of only the aortic valve is most likely to represent degenerative disease of the cusps (a process in older patients akin to coronary artery calcification) or deterioration of a congenitally bicuspid valve ( Chapter 75 ). In developing countries, calcification of the aortic or mitral valves, or both, is usually a late sequela of rheumatic fever. Calcification of the mitral annulus, which is seen in patients older than 70 years and is about four times more frequent in women than in men, is only rarely of clinical significance. The pattern of calcification is characteristic and should not be confused with that of the mitral valve. Calcium is deposited mainly between the base of the posterior mitral leaflet and the posterior wall of the left ventricle. It is seen as a broad, curvilinear band of calcium in a “C” shape, open superiorly and to the right on the frontal film and anteriorly on the lateral. In severe cases, the calcific deposits may also extend across the base of the anterior mitral leaflet and then form an “O” encircling the mitral orifice.

Calcification of the myocardium almost always indicates a previous transmural infarction and, frequently, a ventricular aneurysm. The calcified scar appears as a fine, curvilinear density, most commonly on the anterolateral aspect of the heart, best seen on the frontal view ( Fig. 51-8A ), or in the lower portion of the interventricular septum, best seen on the lateral projection (see Fig. 51-8B ). Calcification of the pericardium is usually coarser and tends to occur in clumps. Often, pericardial calcium is distributed primarily over the interventricular sulcus and the atrioventricular grooves, but when extensive, the deposits may coalesce and completely surround the heart ( Fig. 51-9 ).

FIGURE 51-8  Calcified myocardial infarctions. A, Patient 1: frontal projec-tion of an anterolateral left ventricular aneurysm. The fine calcific line outlines an anterolateral aneurysm of the left ventricle. The calcific deposit is much finer than that seen with pericardial calcification. The patient had suffered a myocardial infarction several years earlier. B, Patient 2: lateral projection of a septal infarction. The curvilinear calcific deposit is within the scarred lower portion of the ventricular septum. The infarction extended posteriorly along the base of the heart to involve the diaphragmatic wall of the left ventricle (arrow).

FIGURE 51-9  Calcific pericarditis. A, Frontal projection. A large, thick, calcific plaque (arrow) lies just below the level of the left upper lobe bronchus. More caudad, the calcific deposits become confluent and cover the diaphragmatic surface of the heart. B, The dense calcific peel around the cardiac apex and the diaphragmatic aspect of the heart is better seen. Linear calcific deposits (arrows) lie within the atrioventricular sulcus. C, Nonenhanced computed tomography shows the irregular, thick, calcific peel almost encircling the heart.

Calcification of the coronary arteries is a specific sign of complicated atheromatous plaques in which previous hemorrhage has occurred. Not uncommonly, this type of plaque, which may not produce significant narrowing of the vessel, is the site of acute thrombosis and vascular occlusion leading to myocardial infarction. There is no correlation between the sites of calcium deposition and the sites of greatest stenosis, but a strong correlation exists between the extent of coronary artery calcification and the extent of coronary arterial sclerosis.

Calcification of the coronary arteries is difficult to visualize on chest films because the deposits are thin and their shadows are blurred by the motion of the heart. Ultrafast computed tomography (CT) scanning using either electron beam or helical CT is very sensitive and accurate for detecting and quantifying the extent of coronary arterial calcification ( Chapter 54 ). However, the data accumulated to date have not clearly shown a correlation between the volume of coronary calcification and the clinical status of the patient. Although high calcium scores indicate extensive atherosclerosis, acute events, such as myocardial infarction or sudden death, can occur in patients with little or no calcification of their coronary arteries.