Aortic stenosis: What happens when a key heart valve narrows?

Think of your heart's four valves as toll gates. They open and close to ensure traffic — in this case, blood — flows in an orderly, one-way direction. However, if a gate only partially opens, less traffic gets through, and you're bound to have gridlock. This is what happens during aortic stenosis.

The aortic valve is the last toll gate for oxygenated blood on its journey to the rest of the body. Aortic stenosis, or a narrowing of the valve, prevents it from opening all the way. This forces the heart to work harder to push blood through. Over time, the extra burden on the muscle can lead to serious issues, such as heart failure.

Aortic stenosis is treatable with therapies ranging from keeping a close eye on the condition to medications and surgery. A cardiologist can help determine the best treatment for you.

Aortic stenosis causes and risk factors

Narrowing of the aortic valve mostly affects older adults, occurring in about 2% of people older than 65, according to the National Institutes of Health. Why is this group at higher risk? The most common cause of aortic stenosis is calcium buildup on the valve, which can take years to occur. As more calcium accumulates on the valve, the opening can narrow, which leads to aortic stenosis. Aortic stenosis can also be hereditary. You may be more likely to develop the condition if a parent or sibling had it.

Less common causes of aortic stenosis include:

• Bicuspid aortic valve. Normally, the aortic valve has three flaps called leaflets that open and close. However, some people are born with only two leaflets, which is called bicuspid aortic valve. These flaps can stiffen and struggle to open, causing aortic stenosis.
• Rheumatic fever. A rare cause of aortic stenosis, this disease can develop from poorly treated strep throat or scarlet fever. Rheumatic fever is most common in children, and it can damage the aortic valve. This can lead to aortic stenosis years later.

How aortic stenosis can harm your health

For oxygen-rich blood to reach your organs and tissues, it must leave the left ventricle, one of the heart's two lower chambers. From there, it passes through the aortic valve into a major artery called the aorta. Smaller arteries carry blood from the aorta to many destinations throughout your body.

Aortic stenosis makes it harder for the heart to pump blood and for blood to get where it needs to go. As the heart tries to send blood through a smaller opening, the left ventricle wall may grow thicker from the extra effort. Thicker walls may leave less room for blood inside the ventricle, and the heart may not be able to supply all the blood the body needs. This is known as heart failure.

Severe aortic stenosis can be life-threatening, especially if it leads to heart failure. Aortic stenosis can contribute to other serious heart problems, including atrial fibrillation, the most common type of abnormal heart rhythm. A narrow aortic valve may also lead to pulmonary hypertension, or high blood pressure in the lung arteries. It could also cause a stroke.

Symptoms show up late

Aortic stenosis progresses at different rates in different people. You can feel this condition's effects, but usually not until it's far along. For example, when blood flow through the valve is significantly reduced, you may feel chest pain after physical activity.

Additional aortic stenosis symptoms include:

• Coughing
• Difficulty breathing during exercise
• Difficulty sleeping
• Dizziness or lightheadedness
• Fainting
• Rapid heartbeat
• Shortness of breath
• Swelling in the ankles or feet
• Tiring easily

Diagnosing a narrow aortic valve

If you feel unusually tired or are struggling to complete normal physical activities, such as walking to the mailbox, it may be a sign of aortic stenosis. It's worth notifying your primary care provider about it — and he or she may refer you to a cardiologist.

Your provider will ask about your health history and conduct a physical exam. Tests or procedures that may help diagnose aortic stenosis include:

• Cardiac catheterization. During this minimally invasive procedure, a cardiac specialist will measure blood pressure and flow in your heart. He or she will also inject dye to watch how it moves through the heart's arteries.
  
• Chest X-ray. This imaging test may show signs of aortic stenosis, such as thickening of the heart muscle.
  
• Echocardiogram. A type of ultrasound, an echocardiogram can show narrowing of the aortic valve.
  
• Electrocardiogram. This test measures your heart's electrical activity, which may be affected by a calcium buildup and a thickening of the muscle.
  
• Exercise stress test. During this test, you'll walk on a treadmill while connected to heart monitoring equipment to see how your heart responds to physical activity.

Aortic stenosis treatment

How your provider decides to treat aortic stenosis depends on a variety of factors, such as whether you have symptoms and, if so, their level of severity.

If your symptoms are mild, you may not need any treatment other than seeing your provider regularly to check your status. During these appointments, your provider will ask about your symptoms, conduct a physical exam, and see how the valve looks by performing an echocardiogram. If you have a heart condition related to aortic valve narrowing, such as heart failure or atrial fibrillation, you'll take medications to control symptoms.

Sometimes, the best treatment option is to repair or replace a damaged aortic valve. One repair option is a procedure called a balloon valvuloplasty. Using a catheter, a specialist will deliver a tiny balloon to the heart and inflate it inside the aortic valve to improve blood flow.

A heart surgeon can replace the aortic valve by performing open-heart surgery. Increasingly, many patients are eligible to undergo transcatheter aortic valve replacement, or TAVR, a less invasive catheter-based procedure. During TAVR, an interventional cardiologist sends a replacement valve through a catheter to the aortic valve. The new valve sits inside the old one, pushes the damaged leaflets aside, and allows blood to pass through normally.

Curious about cardiac risk factors and how to reduce them? Take our quiz to learn more about heart health.