Aortic stenosis is a heart condition characterized by the narrowing of the aortic valve. (Stenosis means narrowing of a passage or opening in the body.) This narrowing restricts blood flow from the left ventricle—the heart’s lower left chamber—to the aorta, the large artery that transports oxygen-rich blood from the heart to the rest of the body. As a result, the heart must work harder than usual to pump blood into the aorta and throughout the body.

Initially, there may be no symptoms. However, over time, as the aortic valve becomes increasingly narrowed, symptoms can gradually develop. These symptoms, including chest pain, fatigue, shortness of breath, and fainting episodes, among others, often worsen with physical activity. Additional complications of the condition may include heart failure and infective endocarditis (when bacteria or fungi infect the heart's inner lining or valves).

Most commonly, aortic stenosis occurs when the leaflets thicken and grow stiff due to calcium buildup. Other causes include congenital (present at birth) aortic valve abnormalities and damage to the valve caused by rheumatic fever. (Calcium buildup can also occur in congenitally abnormal aortic valves and in valves damaged by disease.)

In the United States, aortic stenosis most commonly occurs in older adults due to calcium buildup (more on this below). It is relatively uncommon in people under age 65 who do not have a congenital aortic valve abnormality. In the U.S., around 5% of 65-year-olds have aortic stenosis, and the condition becomes more common with increasing age. Studies have found that about 12% of people aged 75 or older have the condition, and approximately 3% of these cases are severe.

Fortunately, effective treatments are available for aortic stenosis, including surgical aortic valve replacement and transcatheter aortic valve replacement (TAVR).

The aortic valve is located between the left ventricle and the aorta. A normal aortic valve has three leaflets, or flaps. When the left ventricle contracts, the aortic valve’s leaflets open to allow blood to flow into the aorta. The leaflets then close to prevent blood from flowing back into the heart.

In aortic stenosis, the opening of the aortic valve becomes narrowed. As a result, the left ventricle has to work harder than usual to pump blood through the smaller opening and into the aorta. Because the left ventricle must work harder, its muscular wall grows thicker and requires more oxygen than is provided. This can result in angina (chest pain or discomfort). Severe narrowing of the aortic valve can reduce the amount of blood that reaches the brain, especially during physical activity, resulting in dizziness and/or fainting episodes.

Aortic stenosis, in particular when caused by calcium buildup, typically progresses over time. The rate of progression varies from one person to another based on a number of risk factors, including older age, high blood pressure, smoking, and obesity, among others.

People without symptoms may not need any treatment beyond regular monitoring. However, once symptoms appear, the outlook for people with aortic stenosis worsens, and treatment is necessary to improve symptoms and survival rates.

There are multiple causes of aortic stenosis, including:

• Calcium accumulation on the leaflets of the aortic valve (calcific aortic stenosis): As people age, calcium deposits accumulate on the leaflets of the aortic valve, stiffening them and narrowing the valve opening. Calcium accumulation on the valve’s leaflets is the most common cause of aortic stenosis.
  
  While researchers are still studying the process of calcification of the valve, it is thought to begin when cells on the surface of the leaflets become damaged by mechanical stress (for example, from blood flow through the valve in people with high blood pressure), radiation (for example, chest radiation for cancer treatment), certain immune system proteins involved in inflammation, or other causes. Once damaged, lipids (fats), including LDL (the “bad” cholesterol), build up on the leaflets. In response, cells from the immune system travel to the lipid deposits, causing inflammation, which in turn leads to calcification of the leaflets.
  
  In people with a normal, three-leaflet valve, calcific aortic stenosis usually begins to cause symptoms in their 60s and 70s.
  
• Congenital aortic valve anomalies (congenital aortic stenosis): Congenital valve anomalies, in which the aortic valve does not form correctly during fetal development, can impact the number of leaflets. Some people are born with only two (known as bicuspid aortic valve, or BAV). More rarely, people may be born with one (unicuspid) or four (quadricuspid) aortic valve leaflets. These leaflet abnormalities prevent the valve from working properly and can result in a narrowing of the valve opening.
  
  While BAVs can cause aortic valve narrowing that results in aortic stenosis, most BAVs work normally for many years. However, aortic stenosis can also develop in people with a BAV due to calcium accumulation on the valve’s leaflets. In those with BAV, calcific aortic stenosis usually occurs in people in their 40s, 50s, and 60s. It develops earlier in individuals with a BAV because having only two leaflets leads to turbulent blood flow through the valve, resulting in earlier than expected damage to and calcification of the leaflets.
  
• Rheumatic heart disease: Rheumatic heart disease is a condition in which one or more episodes of rheumatic fever permanently damage the heart’s valves. Rheumatic fever is a disease that can develop after an infection with group A Streptococcus (strep) bacteria, including strep throat, scarlet fever, and impetigo. It can cause inflammation and scarring of the aortic valve, as well as fusion of the valve’s leaflets that narrow the valve opening. Problems with the valve develop five to 10 years or more after getting rheumatic fever.
  
  Rheumatic heart disease is a major cause of heart valve disease in low- and middle-income countries; it is a rare cause of aortic stenosis in developed countries.

Risk factors for calcific aortic stenosis include:

• Advanced age
• Congenital aortic valve abnormality
• Metabolic syndrome (having three or more of the following conditions: abdominal obesity, high blood pressure, high blood sugar levels, high blood triglycerides, low HDL cholesterol)
• High blood pressure
• High cholesterol levels
• Smoking
• Diabetes
• Male sex
• Obesity

People with mild or moderate aortic stenosis often do not have any symptoms or only mild symptoms. Around 50% of people with severe aortic stenosis also do not have symptoms.

However, those who do have symptoms may experience the following:

• Shortness of breath with physical exertion
• Chest pain or discomfort (may occur with physical exertion and improve with rest)
• Fatigue
• Dizziness, fainting, or weakness with physical exertion
• Reduced exercise tolerance
• Palpitations (feeling that the heart is beating rapidly or irregularly)

In infants, aortic stenosis is caused by congenital aortic valve abnormalities. Symptoms in infancy may include:

• Difficulty breathing
• Rapid breathing
• Rapid heart rate
• Heart failure
• Poor feeding
• Growth failure
• Acting fussy
• Pale or mottled (patchy color) skin
• Easily fatigued with physical activity

By two months of age, infants with severe aortic stenosis often develop progressive congestive heart failure.

Older children and adolescents usually do not have symptoms, though 10% of older children with aortic stenosis experience shortness of breath, chest pain, and/or discomfort or fainting episodes, especially when exercising.

To diagnose aortic stenosis, the doctor will review your medical history, conduct a physical exam, and order one or more diagnostic tests.

The doctor will ask about your symptoms, such as chest pain, shortness of breath with physical activity, and dizziness and/or fainting episodes, as well as the severity of your symptoms and when they began. The doctor may also ask whether you have any known congenital heart defects and/or a history of rheumatic fever.

During the physical exam, the doctor will listen to your heart using a stethoscope to check for a heart murmur suggestive of aortic stenosis. Doctors often first suspect aortic stenosis, including in patients without any symptoms, based on the presence of this murmur (follow-up testing is necessary to make a definitive diagnosis). The doctor will also check your blood pressure and carotid pulse (the pulse in the carotid arteries located on each side of your neck).

Echocardiography is the main diagnostic test for aortic stenosis. This ultrasound test uses sound waves to create images of the heart, allowing the doctor to evaluate the structure and function of the left ventricle and aortic valve to identify stenosis and determine its cause and severity.

The most commonly used echocardiogram is the transthoracic echocardiogram (TTE). In this test, a handheld transducer is placed on the chest. The transducer emits sound waves that bounce off internal structures, including the heart, and go back to the transducer. A computer processes the waves to produce moving images on a monitor that allows doctors to assess the function of the aortic valve and blood flow through it.

If the quality of images produced by TTE is insufficient, a transesophageal echocardiogram (TEE) may be necessary. In this test, a flexible tube with a transducer is inserted into the patient’s throat and esophagus, behind the heart. TEE may provide better images of the structure of the aortic valve than TTE. It may also be used before a patient undergoes a transcatheter aortic valve replacement (TAVR) procedure (see treatment section below).

Additional tests may also be used to assess the function and structure of the aortic valve and heart, and to help make a diagnosis, including:

• Exercise stress testing: Some people with severe aortic stenosis may not experience any symptoms because they avoid activities (such as exercise) that trigger them, or they may write off symptoms, such as shortness of breath, as normal signs of aging or a lack of fitness.
  
  However, it is important to determine whether these individuals have symptoms of aortic stenosis. This is because once symptoms develop, the outlook worsens, and without treatment, the condition can be life-threatening.
  
  Exercise stress testing is used to determine whether people with severe aortic stenosis have symptoms. In this test, patients exercise (for example, they may walk on a treadmill or ride a stationary bicycle) while their blood pressure is monitored. Exercise stress testing is used because aortic stenosis symptoms often become apparent or worsen during exercise. If blood pressure drops, the individual has reduced exercise capacity compared to other people without heart disease of the same sex and age, or symptoms occur during the test, the patient is considered to have symptomatic aortic stenosis and should receive prompt treatment.
• Cardiac catheterization: In this minimally invasive procedure, a catheter is inserted into a vein or artery in the groin, arm, or neck and guided to the heart. It is not commonly used to make a diagnosis, though it may be done when the diagnosis is uncertain after an echocardiogram and other noninvasive tests. It may also be used before people undergo an aortic valve replacement procedure. The test can measure the pressure inside the heart chambers and across the aortic valve, providing detailed information about the severity of the stenosis.
• Cardiac Computed tomography (CCT) scan and magnetic resonance imaging (MRI): These imaging tests can help health care providers evaluate heart structures when other tests are inconclusive or inconsistent. A CT scan of the heart may be used to measure the amount of calcium built up on the aortic valve, which can help determine the severity of aortic stenosis. An MRI of the heart may be used to evaluate the size and function of the left ventricle and the structure of the aortic valve.
• Chest X-ray: A chest X-ray can provide images of the heart and lungs, helping health care providers assess for pulmonary edema in patients with heart failure and rule out causes of shortness of breath other than aortic stenosis. Chest X-rays are not usually used to make a diagnosis, though they may show aortic valve calcium buildup in those with calcific aortic stenosis and an enlarged heart and/or aorta.
• Electrocardiogram (ECG or EKG): This test, which is not diagnostic, records the electrical activity of the heart and can identify co-existing heart conditions such as atrial fibrillation and coronary artery disease.

Treatments for aortic stenosis may include the following:

• Observation and monitoring: For people with asymptomatic aortic stenosis, regular monitoring through echocardiograms and clinical assessments can help track the progression of the condition and determine when other treatments might be needed.
• Activity restriction: People with moderate-to-severe aortic stenosis who do not have symptoms may be advised to restrict or avoid strenuous physical activity. Those with mild aortic stenosis who do not have any symptoms typically do not need to limit their physical activity. An exercise stress test may be used to assess what level of physical activity is appropriate.
  
  People with aortic stenosis who have symptoms should avoid physical activity until they undergo aortic valve replacement.
• Medications: While no medications can reverse or stop the progression of aortic stenosis, certain drugs may be prescribed to manage other co-existing heart conditions such as high blood pressure, heart failure, coronary artery disease, and atrial fibrillation. These and other heart conditions are common in people with aortic stenosis.
• Aortic valve procedures: Replacement of the aortic valve is typically the most effective treatment option for people with aortic stenosis.
• Surgical aortic valve replacement (surgical AVR or SAVR): In this procedure, the narrowed aortic valve is removed and replaced with a mechanical (made of man-made materials) or a biological (made from human, cow, or pig tissue) prosthetic valve. The procedure may be done via open-heart surgery or minimally invasive surgery (known as minimally invasive AVR or MIAVR).
• Transcatheter aortic valve replacement (TAVR): A less invasive alternative to traditional surgery, TAVR involves threading a catheter—a thin, flexible tube—through a blood vessel to the heart and placing a new biological prosthetic valve within the narrowed aortic valve. This procedure is also known as transcatheter aortic valve insertion (TAVI).
• Ross procedure: In this open-heart surgical procedure, the narrowed aortic valve is removed and replaced with the patient’s own pulmonary valve (the heart valve that regulates blood flow from the right ventricle to the pulmonary artery). A donor valve is used to replace the patient’s pulmonary valve. The Ross procedure may be a treatment option in young or middle-aged people with aortic stenosis.

• Percutaneous aortic balloon valvuloplasty: In this procedure, a catheter is inserted into a vein and threaded to the heart. Once in position, a balloon is inflated within the aortic valve to widen the opening. Narrowing (known as restenosis) of the aortic valve is common after this procedure. In adults with severe aortic stenosis, this may be used as a bridge to surgical AVR or TAVR or as a palliative treatment for patients who are not good candidates for aortic valve replacement. It is also often used to treat infants and children with aortic stenosis. Whereas in adults with calcific aorta, the leaflets become stiff, in children the leaflets are usually more pliable, and it is easier to widen the aortic opening via balloon valvuloplasty.

People with aortic stenosis are at increased risk for certain complications, including:

• Heart failure
• Chest pain or discomfort (angina)
• Fainting episodes (syncope)
• Heart arrhythmias such as atrial fibrillation
• Sudden cardiac death
• Worsening of coronary artery disease (CAD)
• Pulmonary hypertension
• Infective endocarditis
• Blockage of blood vessels in the heart, kidneys, brain (causing stroke or transient ischemic attack), or other organs due to blood clots or tiny pieces of calcium that break off from the aortic valve

The outlook for people with aortic stenosis can vary based on several factors, including the severity of the condition, the presence of symptoms, and the timeliness of diagnosis and treatment.

Those with asymptomatic aortic stenosis typically do not require treatment and can participate in everyday activities, including strenuous exercise, without restriction. However, because aortic stenosis may worsen over time, they should undergo regular monitoring with echocardiography. People with mild asymptomatic stenosis may only need to get an echocardiogram every three to five years. Those with moderate asymptomatic aortic stenosis should be monitored every one to two years, and people with severe asymptomatic disease should be monitored every six to 12 months.

The rate at which aortic stenosis progresses can vary considerably; however, certain factors, including metabolic syndrome and smoking, may speed up its progression. Once symptoms develop, however, without treatment, the prognosis is poor. In general, the most effective treatment for aortic stenosis is aortic valve replacement, which may be performed via open-heart surgery or TAVR, a non-surgical procedure. The outlook for people who undergo an aortic valve replacement procedure is typically excellent.