Aortic and Mitral Valvular Disease

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CHAPTER 60 Aortic and Mitral Valvular Disease

For the diagnosis of aortic and mitral valvular disease, a variety of noninvasive techniques are available to assess cardiac valve morphologic features and function, with echocardiography currently being the most widely used modality for this purpose. Technical advances in electrocardiographically gated multidetector row computed tomography (MDCT) and magnetic resonance (MR) imaging allow the noninvasive visualization of the cardiac valves. In this article, we describe noninvasive imaging methods including radiography, echocardiography, and cardiac CT and MRI to assess aortic and mitral valvular disease.



Aortic stenosis has become the most common valvular disease in the Western world, largely because of the increased life expectancy of the population. The prevalence of aortic stenosis in the population older than 65 years is 2% to 7%; aortic sclerosis, the precursor to aortic stenosis in which there is valve thickening but no stenosis, is present in approximately 25% of this age group.2,3 Whereas aortic stenosis is seen in patients with both tricuspid and bicuspid aortic valves, the patients with bicuspid aortic valves will become symptomatic and present for valve replacement an average of one to two decades earlier in life.4 Nonatherosclerotic causes of aortic stenosis, such as rheumatic and congenital, are rare in the developed world.2

Manifestations of Disease

Clinical Presentation

Aortic stenosis in asymptomatic patients is usually identified incidentally during the cardiac auscultation portion of the physical examination, when note is made of a late systolic murmur or a normally split second heart sound. Symptomatic patients can present with angina, syncope, dyspnea on exertion, and eventually symptoms of heart failure.1 The patient’s symptoms are associated with the degree of stenosis at the level of the aortic valve and with the degree of resulting left ventricular dysfunction. As the stenosis becomes more significant, with a higher pressure gradient across the valve, the left ventricle responds to the systolic pressure overload with concentric hypertrophy. Whereas this increased wall thickness is the expected, appropriate adaptation to increased pressure, it in turn causes a diastolic dysfunction that reduces cardiac output. In addition, hypertrophy may also cause reduced or imbalanced distribution of coronary blood flow, thereby increasing the risk of subendocardial ischemia and worsening the symptoms of heart failure.1

Imaging Techniques

Computed Tomography

Although echocardiography will likely continue to be the first-line modality for diagnosis, grading, and monitoring of aortic stenosis, ECG-gated multislice CT can add more information in patients in whom clinical symptoms for some reason do not match the echocardiographic findings or in patients who are technically challenging.6 The main advantage of CT over transthoracic echocardiography, other than being faster, is the more reliably accurate measurement of valve orifice area by planimetry, which in CT is not limited by hemodynamic factors, such as low cardiac output, as it is in transthoracic echocardiography (Figs. 60-2 and 60-3).6 In addition, CT can give a reproducible assessment and quantification of valve calcification, a major component of stenosis that correlates with its severity (Figs. 60-4 and 60-5).7 Newer multidetector CT scanners do not require pretreatment with β blockers for rate control if the heart rate is below 85 beats/min and allow a dynamic display of valve motion throughout the full cardiac cycle.8 The main disadvantages of CT, in addition to the relatively higher cost and lower availability, are radiation and the need for intravenous administration of contrast material.

Magnetic Resonance

Qualitative assessment of aortic valve stenosis can be performed by steady-state free precession (SSFP) cine MR because of the excellent temporal resolution, which allows highly accurate evaluation of valve motion.7 A signal void due to spin dephasing representing the stenotic jet is identified projecting from the valve toward the proximal aorta. Adequate quantitative measurements are not possible with the SSFP MR technique. For quantification of aortic stenosis, phase contrast MR imaging is typically used. With this technique, the peak flow of the jet in the ascending aorta can be measured, and as with echocardiography, the pressure gradient can be calculated by the modified Bernoulli equation (ΔP = 4V2) (Fig. 60-6). A disadvantage of MR in evaluation of aortic stenosis is the poor visualization of leaflet calcification, a major factor in the disease process.

Treatment Options


The key elements of medical management of asymptomatic patients with aortic stenosis include advising against strenuous exercise in cases of moderate to severe stenosis; antibiotic prophylaxis against endocarditis for dental or other interventional procedures; antihypertensive therapy; and close monitoring both of the severity of stenosis and for appearance of symptoms.1 The last item is of great importance, both because disease progression tends to be unpredictable and as surgical therapy, namely, aortic valve replacement, is usually indicated once symptoms appear or are thought to be imminent. Recognition of the onset of symptoms can be especially difficult in patients with other comorbidities, and special attention needs to be paid to any change in tolerance of strenuous activity or appearance of chest pain in either rest or stress.1


As the combined risk of aortic valve replacement (up to 10% mortality in the elderly or in those with severe comorbidities) and complications associated with having a prosthetic valve (2% to 3% per year) is much greater than the risk of sudden cardiac death in the asymptomatic patient, even those with severe stenosis by imaging, surgical therapy is usually not indicated until symptoms appear.4 The exception to this rule of thumb is if there is significant stenosis-related left ventricular dysfunction or if there has been a substantial increase in peak aortic jet velocity (>0.3 m/sec within 1 year), indicating imminent onset of symptoms.2

In terms of surgical techniques, open aortic valve replacement is the conventional surgical therapy, with either a bioprosthesis or a mechanical valve (Fig. 60-7). The mechanical valves have a longer lifespan, but they require permanent anticoagulation and are therefore usually used in younger patients. Aortic balloon valvotomy can sometimes be used to relieve stenosis, although it is usually reserved for young patients without valve calcifications. In older adults, it is used only in cases of palliation in poor surgical candidates or as a temporary bridge to valve replacement in clinically unstable patients.4