Aortic Stenosis

Essentials of Diagnosis

  • In adults, usually asymptomatic until middle or old age.
  • Delayed and diminished carotid pulses.
  • Soft, absent, or paradoxically split S2.
  • Harsh systolic murmur, sometimes with thrill along left sternal border, often radiating to the neck; may be louder at apex in older patients.
  • ECG usually shows left ventricular hypertrophy; calcified valve on x-ray or fluoroscopy; echo-Doppler is diagnostic in most cases.

General Considerations
Aortic valvular stenosis may follow rheumatic fever but is more commonly caused by progressive valvular calcification. This may occur in younger patients with a congenitally bicuspid valve or in elderly individuals with normal three-cusp valves. In the latter group, the aortic valve becomes sclerotic and, with further calcification, stenotic.

Approximately 25% of patients over age 65 and 35% of those over age 70 have echocardiographic evidence of sclerosis, which appears to be related to atherosclerotic vascular disease and is associated with a higher rate of vascular events. About 10-20% of these will progress to hemodynamically significant aortic stenosis over a period of 10-15 years. Thus, aortic stenosis has become the most common surgical valve lesion in developed countries. Degenerative valve disease is three to four times more frequent in men than in women and is more common in smokers and hypertensives. Valvular stenosis must be distinguished from supravalvular obstruction and from outflow obstruction of the left ventricular infundibulum, both relatively rare.

Clinical Findings
A. Symptoms and Signs
Slightly narrowed, thickened, or roughened valves (aortic sclerosis) or aortic dilation may produce the typical murmur and thrill without causing significant hemodynamic effects. In mild or moderate cases, the characteristic signs are a systolic ejection murmur at the aortic area transmitted to the neck and apex; in severe cases, a palpable left ventricular heave or thrill, a weak to absent aortic second sound, or reversed splitting of the second sound are present (see Table 10-1). When the valve area is less than 0.8-1 cm2 (normal, 3-4 cm2), ventricular systole becomes prolonged and the typical carotid pulse pattern of delayed upstroke and low amplitude is present, but this may be an unreliable finding in older patients with extensive arteriosclerotic vascular disease. Left ventricular hypertrophy increases progressively, with resulting elevations in ventricular end-diastolic pressure. Cardiac output is maintained until the stenosis is severe (with a valve area < 0.8 cm2). Patients may present with left ventricular failure, angina pectoris, or syncope.

Symptoms of failure may be sudden in onset or may progress gradually. Angina pectoris - stable frequently occurs in aortic stenosis. One-half of patients with calcific aortic stenosis and angina have significant associated coronary artery disease, whereas coronary disease is noted at only half this rate in the absence of angina. Syncope is typically exertional and may be due to arrhythmias (usually Ventricular tachycardia but sometimes sinus bradycardia), hypotension, or decreased cerebral perfusion resulting from increased blood flow to exercising muscle without compensatory increase in cardiac output. Sudden death may occur but is rarely the initial manifestation of aortic stenosis in previously asymptomatic patients.

B. Diagnostic Studies
The clinical assessment of aortic stenosis may be difficult, especially in older patients. The ECG reveals left ventricular hypertrophy or suggestive repolarization changes in most patients but may be normal in up to 10%. The chest radiograph may show a normal or enlarged cardiac silhouette, calcification of the aortic valve, and dilation and calcification of the ascending aorta. The echocardiogram provides useful data about aortic valve calcification and opening and left ventricular thickness and function, while Doppler can estimate the aortic valve gradient. These data can reliably exclude or diagnose severe stenosis. In patients with moderate obstruction, especially with low cardiac output or concomitant regurgitation, these evaluations may be inaccurate.

Angina is a pain or discomfort in the chest or adjacent areas caused by insufficient blood flow to the heart muscle. This chest pain is relieved by rest or medication within a short period of time (usually 15 minutes). Chest pain of a longer duration or pain appearing with a lower level of effort than before, even at rest, should be considered unstable angina.

Causes, incidence, and risk factors
Angina affects approximately 3% to 5% of the population in the U.S. The most common cause is Coronary artery disease (CAD).

Cardiac catheterization is the definitive diagnostic procedure. The valve gradient is measured and the valve area calculated; a valve area below 0.8 cm2 indicates severe stenosis. Aortic regurgitation can be quantified by aortic root angiography. Coronary arteriography should be performed in most adults with aortic stenosis to assess for concomitant coronary disease.

Prognosis & Treatment
Following the onset of heart failure, angina, or syncope, the prognosis without surgery is poor (50% 3-year mortality rate). Medical treatment may stabilize patients in heart failure, but surgery is indicated for all symptomatic patients, including those with left ventricular dysfunction, which often improves postoperatively. Valve replacement is usually not indicated in asymptomatic individuals. Exceptions are those with declining left ventricular function, very severe left ventricular hypertrophy, and very high gradients (> 80 mm Hg) or severely reduced valve areas (= 0.7 cm2).

The surgical mortality rate for valve replacement is 2-5%, but it rises to 10% above the age of 75. Mortality rates are substantially higher when left ventricular function is depressed or when severe coronary disease and prior myocardial infarctions are present. Severe coronary lesions are usually bypassed at the same time. Anticoagulation with warfarin is required for mechanical prostheses but is not essential with bioprostheses. Although bioprosthetic valves have hitherto undergone degenerative changes and required replacement within 7-10 years (sometimes within 3 years), newer ones may be more durable. Some centers have begun performing the Ross procedure, which entails switching the patient’s pulmonary valve to the aortic position and placing a bioprosthesis in the pulmonary position. Because bioprostheses do not deteriorate as fast on the right side of the heart, this procedure has produced excellent long-term results without anticoagulation.

Although percutaneous balloon valvuloplasty can produce short-term reductions in the severity of aortic stenosis, restenosis occurs rapidly in most adults who have calcified valves. Except in adolescents, balloon valvuloplasty should be reserved for individuals who are poor candidates for surgery or as an intermediate procedure to stabilize high-risk patients prior to surgery.

Preferences:
Carabello B: Clinical practice. Aortic stenosis. N Engl J Med 2002;346:677. [PMID: 11870246]

Palta S et al: New insights into the progression of aortic stenosis: implications for secondary prevention. Circulation 2000; 101:2497. [PMID: 10831524]

Pereira JJ et al: Survival after aortic valve replacement for severe aortic stenosis with low transvalvular gradients and severe left ventricular dysfunction. J Am Coll Cardiol 2002;39: 1356. [PMID: 11955855]

Provided by ArmMed Media
Revision date: July 9, 2011
Last revised: by Janet A. Staessen, MD, PhD