A prosthetic aortic valve is an artificial device implanted to replace a diseased or damaged native aortic valve, which controls blood flow from the heart’s main pumping chamber to the body. While these devices significantly improve life expectancy and quality of life, they are not impervious to complications over time. One such complication is prosthetic aortic valve stenosis, a condition where the implanted valve narrows. This narrowing obstructs the normal flow of blood, requiring the heart to work harder to pump blood through the restricted opening. The development of stenosis in a prosthetic valve can occur gradually, affecting the long-term function of the replacement valve.
What is Prosthetic Aortic Valve Stenosis?
Stenosis in the context of a prosthetic aortic valve refers to a narrowing or obstruction of the valve’s opening, impeding blood flow from the left ventricle into the aorta. This condition can develop through several mechanisms, primarily calcification and pannus formation. Calcification involves the buildup of calcium deposits on the valve leaflets or components. This process leads to hardening and reduced flexibility of the valve, hindering its ability to open fully. Over time, this negatively affects the valve material, causing the artificial valve to narrow and impairing blood flow.
Pannus formation involves the growth of fibrous tissue on its leaflets. This tissue overgrowth can gradually encroach upon the valve opening, leading to a physical obstruction. Structural valve degeneration, an irreversible process, includes both calcification and pannus growth, along with leaflet fibrosis and tears, ultimately leading to valve failure.
There are two main types of prosthetic aortic valves: mechanical and bioprosthetic (tissue) valves. Mechanical valves are durable and generally have a longer lifespan, often lasting approximately 20 years. However, they require patients to take lifelong anticoagulant medication to prevent blood clots from forming on the valve.
Bioprosthetic valves, typically made from animal tissue, offer the advantage of not requiring long-term anticoagulation. Their durability is limited, with typical lifespans ranging from 10 to 15 years due to susceptibility to calcification and material fatigue. Calcification is a more common mode of failure for bioprosthetic valves, while pannus formation can affect both types but is a recognized cause of obstruction in mechanical valves as well.
Recognizing the Symptoms
If a prosthetic aortic valve begins to narrow, individuals may experience several symptoms as the heart works harder to pump blood through the restricted opening. One common sign is shortness of breath, particularly during physical activity. Chest pain, also known as angina, can occur.
Fatigue is another frequent symptom, often described as persistent tiredness. Dizziness or lightheadedness, and fainting spells, can result from reduced blood flow to the brain, especially during exertion. Heart palpitations, sensations of a rapid, fluttering, or pounding heart, may also be noticed. These symptoms often develop gradually, making them easy to dismiss as signs of aging or other less serious conditions, delaying diagnosis.
Diagnosing the Condition
The diagnostic process for prosthetic aortic valve stenosis typically begins with a physical examination. During this examination, a healthcare provider might detect a heart murmur, an abnormal whooshing sound caused by turbulent blood flow through the narrowed valve.
The primary diagnostic tool for assessing prosthetic aortic valve stenosis is transthoracic echocardiography (TTE). This non-invasive imaging technique uses sound waves to create detailed images of the heart and valves, assessing the prosthetic valve’s structure and function. TTE helps detect abnormal densities like calcium deposits or tissue overgrowth, and measures blood flow velocities and pressure gradients across the valve. Elevated pressure gradients or velocities across the valve can indicate stenosis.
For a more detailed evaluation, transesophageal echocardiography (TEE) may be performed. TEE involves a probe passed down the esophagus, providing clearer images. Cardiac CT scans can also provide additional anatomical information, particularly regarding calcification patterns or pannus formation. These techniques help quantify stenosis severity and its impact on heart function.
Treatment and Management
For mild cases, a conservative approach involves regular monitoring with echocardiograms to track the progression of the stenosis. When the stenosis becomes more severe and starts to cause significant symptoms or impact heart function, interventional or surgical options are considered. Surgical aortic valve re-replacement (SAVR) involves removing the failing prosthetic valve and implanting a new one through open-heart surgery.
A less invasive option, transcatheter aortic valve replacement (TAVR), is common, especially for patients at higher surgical risk. TAVR involves delivering a new valve through a catheter and expanding it within the existing failing prosthetic valve, a procedure often referred to as “valve-in-valve.” This technique is particularly valuable for failing bioprosthetic valves. Following intervention, ongoing follow-up care, including regular check-ups and imaging, is necessary to monitor the new valve’s function.