Aortic stenosis risk factors

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Claudia P. Hochberg, M.D. [2], Abdul-Rahman Arabi, M.D. [3], Keri Shafer, M.D. [4], Priyamvada Singh, MBBS [5], Mohammed A. Sbeih, M.D. [6]; Assistant Editor-In-Chief: Kristin Feeney, B.S. [7]

Overview

Aortic stenosis is not generally understood to be a preventable condition. However, some characteristics may incline certain patients to acquire aortic stenosis compared to their healthy counterparts. The most common risk factor for aortic stenosis arises from the congenital condition, bicuspid aortic valve syndrome. Prophylaxis therapy may be used as a preventative mechanism in impeding potential disease onset.

Risk factors

Some of the risk factors for aortic stenosis include:

• Age-related progressive calcification of the normal tricuspid aortic valve (>50% of cases).
• Congenital bicuspid aortic valve that may get calcified later in (30-40% of cases).
• Acute rheumatic fever (less than 10% of cases).

Other risk factors that may speed up the disease process include:

• Hypertension.
• Diabetes mellitus.
• Hyperlipoproteinemia.
• Uremia.

Normal aortic valve have three leafs (tricuspid), but some valves have two leafs (bicuspid). Typically, aortic stenosis due to calcification of a bicuspid valve appears earlier, in the 40s and 50s, whereas that due to calcification of a normal valve appears later, in the 70s and 80s.

Precautions

People with aortic stenosis of any aetiology are at risk for the development of infection of their stenosed valve, i.e. infective endocarditis. To lessen the chance of developing that serious complication, people with AS are usually advised to take antibiotic prophylaxis around the time of certain dental/medical/surgical procedures. Such procedures may include dental extraction, deep scaling of the teeth, gum surgery, dental implants, treatment of esophageal varices, dilation of esophageal strictures, gastrointestinal surgery where the intestinal mucosa will be disrupted, prostate surgery, urethral stricture dilation, and cystoscopy. Note that routine upper and lower GI endoscopy (i.e. gastroscopy and colonoscopy), with or without biopsy, are not usually considered indications for antibiotic prophylaxis.

Not withstanding the foregoing, the American Heart Association has recently changed its recommendations regarding antibiotic prophylaxis for endocarditis. Specifically, as of 2007, it is recommended that such prophylaxis be limited only to:

• Those with prosthetic heart valves.
• Those with previous episode(s) of endocarditis.
• Those with certain types of congenital heart disease .

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.