Chapter 6 Valvular Heart Disease
Cardiac imaging in suspected valvular disease determines the involvement of the valves, the extent of the stenosis or regurgitation, and the hemodynamic consequence of the pressure or volume overload on the heart. It also evaluates associated conditions, such as aortic dissection or aneurysm and ventricular contractility and enlargement.
Fig. 6-1 illustrates the anatomic positions of the heart valves.
VALVULAR AORTIC STENOSIS
Chest Film Findings
The chest film abnormalities depend on the age of the patient and the severity of the stenosis. In infancy, pulmonary edema with generalized cardiomegaly is the typical appearance of obstruction to blood flow at any point between the pulmonary veins, left heart, and aorta (Fig. 6-2). The adult heart is normal in size, and the lungs are clear unless there is left ventricular failure and dilatation (Fig. 6-3). Calcification in the aortic valve over age 40 years occurs in all types of aortic stenosis and clinically marks the stenosis as severe. Dilatation of the ascending aorta is frequent in aortic stenosis but correlates rather poorly with severity or with the site of the stenosis (one third of patients with subvalvular aortic stenosis have dilated aortas).
Imaging Features
The preferred imaging modality for the dynamic assessment of aortic stenosis remains echocardiography. Cardiac-gated multidetector CT (MDCT) angiography is proving to be an excellent modality to detect and quantify aortic valve stenosis. Direct planimetry of the valve opening in systole correlates quite well to echocardiographic grades of aortic stenosis severity. The added advantage of MDCT is that it nicely demonstrates associated aortic root pathologies. Fig. 6-4 shows a case of mild aortic stenosis with the valve in short axis during systole (open) and diastole (closed). Fig. 6-5 shows the same valve in long axis during systole and diastole. Finally, MRI can be useful for aortic stenosis because it can accurately quantify peak aortic valve velocities and pressure gradients. The associated calcium on the valve makes MRI less useful to assess morphology because of the typical signal loss of calcified structures on gradient echo pulse sequences. A narrow orifice to the aortic valve is visible as a jet through the valve. The degree of aortic stenosis can be estimated by comparing the width of the jet with the diameter of the aortic annulus. When the jet is less than 15% of the diameter of the annulus, there is severe aortic stenosis. However, it may also be present when the width of the column of blood through the valve appears to be the same size as the annulus. This latter finding is typical of degenerative aortic stenosis in the elderly and in many cases of rheumatic involvement of the aortic valve. In the former, the valve orifice is irregularly eccentric without commissural fusion, allowing the stream of contrast material adjacent to the three commissures to project over the entire width of the aorta. Calcification may be so extensive that the leaflets are akinetic.
Box 6-1 lists the causes of aortic stenosis.
Congenital Valvular Aortic Stenosis
MDCT can be quite useful at characterizing congenital bicuspid aortic valves. Fig. 6-9 depicts a congenital bicuspid aortic valve in systole on MDCT in cross section and long axis, respectively. This patient has a normal systolic opening area with classic systolic dooming. Fig. 6-10 is a different case of a bicuspid aortic valve on MDCT. This valve demonstrates calcification of the cusps and diastolic prolapse. Cardiac MRI is more limited at depicting aortic valve leaflet morphology because the associated leaflet calcium causes profound signal void on MRI gradient pulse sequences, such as in Fig. 6-11. Black blood MRI pulse sequences may overcome this artifact.
The congenital unicuspid aortic valve is intrinsically stenotic and may at times be incompetent. This valve may exist with no lateral attachments and appear as a diaphragm with a central opening. A second type of unicuspid valve has one lateral attachment to the aortic annulus with the commissure appearing as a raphe between the central point and the aortic wall. Both types of valve are rare. In systole, there is an eccentric jet against the posterior wall of the aorta with no leaflet tissue posteriorly. In diastole, a sinus of Valsalva may appear anteriorly but not posteriorly.
Acquired Valvular Aortic Stenosis
The aortic valve that is not stenotic at birth may become so in two ways:
Calcific aortic stenosis in the adult results from rheumatic heart disease, occurs on a congenital bicuspid aortic valve, and occurs in the elderly. Although some overlap occurs, you can differentiate these three conditions by age and by the presence of other valvular lesions. The congenital bicuspid aortic valve begins to calcify in the fourth decade, whereas degenerative aortic stenosis affects those over 65 years of age. In developing countries, calcification in rheumatic aortic stenosis may appear in the late teens, but it is unusual in the United States until the fourth decade. With the aortic stenosis of rheumatic heart disease, mitral stenosis does not occur for at least 7 to 10 years after an episode of acute rheumatic fever, and aortic stenosis may develop about 7 years after that.
An important clue to the diagnosis of rheumatic disease in the aortic valve is the presence of mitral stenosis or regurgitation and calcification or thickening in the mitral leaflets in an otherwise functional valve. One characteristic of rheumatic aortic stenosis is the fusion of the commissures adjacent to the aortic wall. In general, these valves have either the usual appearance of a tricuspid valve or have one distorted sinus of Valsalva that occupies more than half the aortic annular circumference. When there is fusion of multiple commissures, the leaflets are usually so thickened and distorted that valve morphology is indistinguishable from other types of aortic stenosis.
MDCT can image calcific degenerative aortic valve stenosis (Figures 6-15, (6-16). The valve area can be planimetered from the short-axis views.
SUBVALVULAR AORTIC STENOSIS
Pathologic Abnormalities
Subvalvular aortic stenosis, or subaortic stenosis, consists of a heterogeneous group of abnormalities, several of which are associated with other types of cardiac malformation. These obstructions include:
Angiographic Findings
Optimal visualization of the angiographic features of most of these conditions is possible with biplane left ventriculography with cranial angulation in the left oblique projection. Because several of these malformations may be quite subtle (particularly discrete membranous subaortic stenosis), standard ventriculography may not demonstrate a lesion that is quite evident on pressure tracings. In these instances, an aortic root injection is useful because many of these valves are incompetent and the regurgitant stream outlines the subaortic chamber (Fig. 6-17). A magnetic resonance scan in planes aligned to the cardiac axis can sort out subaortic complexities with tomographic imaging (Fig. 6-18).
About 15% of patients with congenital obstruction to left ventricular outflow have discrete membranous subaortic stenosis. This consists of a 1- to 4-mm-thick membrane below the aortic valve. The membrane varies in position from just below the aortic valve to about 4 cm beneath it. The membrane may attach to the anterior leaflet of the mitral valve, and strands from this membrane may extend to the aortic cusps (Fig. 6-19). About one third to half of these patients have aortic insufficiency, and fewer than 5% have mild mitral insufficiency.
Subaortic Obstruction
Subaortic obstruction may rarely result from valve abnormalities or malalignment defects in complex congenital heart disease. Accessory mitral valve tissue, anomalous attachment of the mitral valve and its chordae tendineae, or a displaced annular insertion of the anterior leaflet result in outflow obstruction. The angiographic findings with each of these abnormalities varies; however, an asymmetric filling defect that moves into the subaortic region during systole and returns to a more posterior and inferior location during diastole is often visible during left ventriculography. Other complex congenital malformations have subaortic obstruction with conoventricular malalignment (e.g., aortic atresia and ventricular septal defect and in transposition with the aorta originating above an infundibular chamber).
SUPRAVALVULAR AORTIC STENOSIS
Classifications
There are three types of supravalvular stenosis. The hourglass type consists of a narrow segment of the ascending aorta just distal to the origin of the coronary arteries (Fig. 6-21). The second type is a membrane or fibrous diaphragm at the sinotubular aortic junction. The least common is hypoplasia of the entire ascending aorta from the sinotubular junction to the origin of the brachiocephalic artery (Figure 6-22). In actual practice, these three forms overlap and are alternatively classified as discrete or diffuse stenoses, categories that correspond to the alternatives in surgical treatment.
AORTIC REGURGITATION
Angiographic Technique
The typical examination is a biplane supravalvular aortogram performed in both oblique projections. The injection rate varies, depending on patient age, the size of the ascending aorta, and the clinical judgment of the severity of the runoff. For example, in the adult with suspected severe aortic regurgitation, an injection rate of 35 to 40 ml/sec over 2 seconds gives good visualization. Analysis of cuspal motion necessitates the cine technique.
Magnetic Resonance Imaging Technique
Cardiac-Gated Multidetector Computed Tomography
MDCT can detect the presence of aortic regurgitation by demonstrating in diastole the leaflet malcoaptation and the resultant regurgitant orifice. MDCT can demonstrate that the planimetered area of the central valvular leakage area correlates well to echocardiogram or MRI grades of aortic regurgitation severity. As with cases of aortic stenosis, MDCT has the added advantage of assessing for concurrent aortopathies. (Figures 6-25 and (6-26 demonstrate cases of mild and severe aortic regurgitation, respectively.

FIGURE 6-26 Severe aortic regurgitation. The aortic valve has a large central regurgitant area (arrow).
Specific Causes of Aortic Regurgitation
Fibrosis from the valvulitis in rheumatic heart disease is the most common aortic valve abnormality that causes regurgitation. These valves have thickened cusps that are shortened by the fibrotic process and may have some commissural fusion. Depending on the severity of the rheumatic process, the leaflets may have no visible calcium or, conversely, they may be reduced to irregular lumps with poor motion. The regurgitant jet is usually central unless the valve commissures are fused asymmetrically. In degenerative aortic valve disease, which occurs in persons over age 65, the cusps are thickened and immobile but without commissural fusion. Then regurgitation occurs over a broad front that is essentially the same diameter as the aortic annulus (Fig. 6-27