Aortic stenosis natural history, complications and prognosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Mohammed A. Sbeih, M.D. [2]; Lakshmi Gopalakrishnan, M.B.B.S. [3]

Overview

Left untreated, aortic valve stenosis can lead to angina, syncope, congestive heart failure, atrial fibrillation, endocarditis, and sudden cardiac death. Surgical treatment of aortic stenosis also carries risks and potential complications including vascular complications and mitral valve injury.

Natural History

Calcific Degenerative Aortic Stenosis

Aortic stenosis due to degeneration of a calcified aortic valve has a prolonged latent period during which time symptoms may be minimal or even lacking . The average rate of progression in valvular aortic stenosis, once moderate stenosis is present and symptomatic, is a decrease in valve area of 0.1 cm² per year . Also on average, there is an increase in the jet velocity of 0.3 m / second per year and an increase in the mean pressure gradient of 7 mm Hg per year . There is tremendous individual variability in the rate of progression of aortic stenosis. Risk factors for atherosclerosis, such as age, smoking, hypertension, obesity and diabetes, lipid abnormalities, chronic renal failure and dialysis, and atherosclerotic disease itself, such as concomitant coronary artery disease are associated with more rapid rates of aortic stenosis progression.

Bicuspid Aortic Valve Disease

Bicuspid aortic valve stenosis presents one to two decades earlier. The rate of progression of degenerative aortic stenosis can be faster than in those with congenital or rheumatic disease . Bicuspid aortic valve, during childhood functions without any significant pressure gradient. However, the thickening and calcification of the valves may be detectable pathologically and on echocardiography by second decade. This progresses to aortic stenosis requiring operative correction in approximately 75% of cases.

Bicuspid aortic stenosis progressively leads to heart failure, arrythmias, angina and other symptoms which generally manifests between 40 to 60 years of age which is relatively younger to manifestation of aortic stenosis otherwise. However, children who develop early pathologic changes in bicuspid aortic valve are more likely to develop aortic insufficiency than stenosis.

Aortic Sclerosis

Aortic sclerosis (defined as aortic valve thickening without obstruction to ventricular outflow) may progress to narrowing of the aortic valve or aortic stenosis. If the pulse pressure or upstroke of the pulse diminishes in the patient with aortic sclerosis, this can be a sign of progression to aortic stenosis.

Complications

Degenerative Calcific Aortic Stenosis

If left untreated, aortic stenosis may lead to complications such as angina, syncope, or heart failure. A complete list of complications of aortic stenosis includes the following:

• Angina
• Arrhythmias
• Atrial fibrillation
• Bleeding. Impaired platelet function and coagulation abnormalities as decreased levels of Von Willebrand factor can be seen in most patients with severe AS. This resolves after valve replacement procedure. 20% of patients have clinical bleeding, most often epistaxis or ecchymoses
• Congestive heart failure, particularly left-sided heart failure or systolic dysfunction
• Endocarditis
• Fainting or syncope. Since the stenosed aortic valve may limit the heart's output, people with aortic stenosis are at risk of syncope and dangerously low blood pressure should they use any of a number of common medications. Ironically, these same medicines are used to treat a variety of cardiovascular diseases, many of which may co-exist with aortic stenosis. Examples include nitroglycerin, nitrates, ACE inhibitors, terazosin (Hytrin), and hydralazine. Note that all of these substances lead to peripheral vasodilation. Normally, however, in the absence of aortic stenosis, the heart is able to increase its output and thereby offset the effect of the dilated blood vessels. In some cases of aortic stenosis, however, due to the obstruction of blood flow out of the heart caused by the stenosed aortic valve, cardiac output cannot be increased. Low blood pressure or syncope may ensue.
• Left ventricular hypertrophy
• Myocardial infarction

Prognosis

Asymptomatic Patients

The prognosis of patients with aortic stenosis who do not have symptoms is quite good . The annual mortality rate is < 1% per year in asymptomatic patients. Only 4% of sudden cardiac deaths that occur in patients with aortic stenosis occur in those patients who are asymptomatic.

Symptomatic Patients

Medical treatment of newly diagnosed moderate to severe symptomatic aortic stenosis is associated with a 25% mortality at one year, and a 50% mortality at two years. Half the deaths are due to sudden cardiac death .

Left untreated, the average survival is 5 years after the onset of angina, 3 years after the onset of syncope, and 1 year after the onset of congestive heart failure .

Low Flow Aortic Stenosis

If there is a decline in left ventricular function due to systolic dysfunction, there may be only a moderate transvalvular gradient or low flow aortic stenosis. If there is fibrosis of the left ventricle, there may be incomplete recovery after aortic valve replacement. This scenario can also occur among patients in whom there is a history of myocardial infarction: there is insufficient contractility to mount an aortic gradient.

Definition

1. An aortic valve areas < 1.0 cm2
2. A left ventricular ejection fraction < 40%
3. A mean pressure difference or gradient across the aortic valve of < 30 mm Hg

With a dobutamine infusion, the aortic valve area should increase to > 1.2 cm2, and the mean pressure gradient should rise above 30 mm Hg. If there is a failure to acheive these improvements, early surgical mortality is 32-33%, but it is only 5–7% in those patients who can augment their contractility and gradient. Survival at five years was 88% after surgery if the patient can augment their contractility, but only 10–25% if the patient cannot augment their contractility.

It should be noted that left ventricular contractile reserve is a better predictor of surgical outcomes than markers of stenosis. Aortic valve surgery is indicated if there is severe AS along with an increase in the systolic velocity integral by >20% during a dobutamine infusion.