The aortic valve guards the opening between the left ventricle and the aorta. The aortic valve opens as the left ventricle begins to pump, allowing blood to eject out of the heart and into the aorta. When the ventricle has finished beating, the aortic valve closes to keep blood from washing back into the left ventricle.
When you develop aortic stenosis, your aortic valve no longer opens completely, so your heart must work much much harder to eject blood. This extra stress on the heart can lead to heart failure and other significant problems.
What Are The Causes Of Aortic Stenosis?
- Degeneration and calcification: In people over 70 years of age, the most common cause of aortic stenosis is "wear and tear." With the passage of time, the aortic valve can begin to degenerate, causing calcium deposits to accumulate on the valve. These calcium deposits infringe on the valvular opening, causing aortic stenosis.
- Bicuspid aortic valve: The most common cause of aortic stenosis in younger people is a congenital bicuspid valve, in which the aortic valve consists of only two "cusps" (i.e., flaps) instead of the normal three. Bicuspid aortic valves are especially prone to the formation of calcium deposits - and thus, to aortic stenosis. People with bicuspid aortic stenosis usually develop symptoms in their 40s and 50s.
- Rheumatic heart disease: Fifty years ago, rheumatic heart disease was the leading cause of aortic stenosis in the developed world. With the advent of antibiotics, rheumatic heart disease has become relatively uncommon.
- Congenital aortic stenosis: Other congenital problems can produce aortic stenosis. These include various malformations of the aortic valve itself, as well as abnormal membranes of obstructive muscle above or below the actual aortic valve. These more unusual forms of congenital aortic stenosis are usually seen in children.
What Problems Are Caused By Aortic Stenosis?In aortic stenosis, the outflow of blood from the left ventricle becomes partially obstructed, and the heart has to work much harder to eject blood. This extra work places significant stress on the left ventricular muscle, which causes it to thicken, or "hypertrophy."
This left ventricular hypertrophy can lead to diastolic dysfunction and diastolic heart failure, in which the thickened muscle interferes with normal cardiac function. Symptoms may include shortness of breath, reduced exercise tolerance, and an increased risk of developing atrial fibrillation.
As the aortic stenosis worsens, chest pain can occur, as well as dizziness and even syncope (loss of consciousness) during exertion.
With very severe aortic stenosis, the left ventricle can become weak and dilated, leading to significant (and often irreversible) heart failure. Sudden death is common with severe aortic stenosis.
How Is Aortic Stenosis Diagnosed?Because untreated aortic stenosis is often fatal, making the correct diagnosis is critical. Fortunately, diagnosing aortic stenosis today is usually not difficult.
Doctors become suspicious of aortic stenosis when patients complain of "typical" symptoms (shortness of breath, reduced exercise tolerance, chest pain, dizziness, or syncope), or before symptoms develop by examining the heart and noting the heart murmur that is typical of aortic stenosis. The diagnosis can be easily confirmed or ruled out by an echocardiogram.
Treating Aortic StenosisThe treatment of aortic stenosis is surgical valve replacement. Drug therapy is ineffective because the problem is a mechanical obstruction of the aortic valve. So if you have aortic stenosis, the question is usually not whether to do surgery, but when.
As a general rule, replacement of the aortic valve should be done soon after your aortic stenosis begins producing symptoms - shortness of breath, chest pain, or dizziness or syncope. Once any of these symptoms develop, the average life expectancy without valve replacement is two or three years. Valve replacement significantly improves this prognosis.
If you have significant aortic stenosis (as measured by echocardiogram) without any symptoms, it is important for both you and your doctor to become closely observant for any sign of those symptoms.
Because surgery suddenly relieves the severe obstruction, in most cases the function of the heart improves fairly dramatically after valve replacement. So even patients who are quite elderly often do well after aortic stenosis surgery.
The prosthetic valves used to replace your diseased aortic valve can either consist entirely of man-made materials (mechanical valves), or they can be made from the heart valve of an animal, generally a pig (bioprosthetic valve). Deciding which type of artificial valve to use depends on your age and whether you can take the blood thinner Coumadin.
All artificial heart valves have an increased propensity to form blood clots. However, blood clotting is less of a problem with bioprosthetic than mechanical valves, so people with the former generally do not have to take chronic Coumadin therapy; those with mechanical valves do.
But mechanical valves generally seem to last longer than bioprosthetic valves. So if you need a valve replacement, are under age 65, and you can take Coumadin, your doctor will likely recommend a mechanical valve. If you are older than 65, or you are younger but can't take Coumadin, a bioprosthetic valve is generally recommended.
Bonow, RO, Carabello, BA, Chatterjee, K, et al. 2008 Focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 1998 Guidelines for the Management of Patients With Valvular Heart Disease): endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. Circulation 2008; 118:e523.