The trileaflet aortic valve is the normal, healthy anatomy found in the vast majority of people. This structure serves as a gateway within the heart, positioned at the exit of the main pumping chamber. Its proper form and function are necessary for the circulation of blood throughout the body.
The Essential Role of the Aortic Valve
The aortic valve is located between the heart’s left ventricle and the aorta, the body’s largest artery. This placement makes it the final barrier blood must cross before entering the systemic circulation. When the left ventricle contracts, pressure forces the valve open, allowing oxygenated blood to flow into the aorta.
The valve’s purpose is to ensure blood flows in only one direction. Immediately after contraction, the valve must snap shut to prevent blood from leaking backward into the left ventricle. This rapid, complete closure is maintained by the valve’s resilient structure, which manages tremendous pressure changes with every heartbeat.
Trileaflet: The Normal Structure vs. Bicuspid
The normal aortic valve is structurally defined as trileaflet, composed of three distinct cusps or leaflets. These three leaflets are typically equal in size, allowing them to open fully and uniformly for blood flow. When the heart relaxes, the three cusps meet perfectly at the center, ensuring a tight seal that prevents backflow. This robust design distributes mechanical stress evenly across the valve structure over a lifetime of use.
The most common deviation is the Bicuspid Aortic Valve (BAV), a congenital defect present from birth. BAV has only two leaflets instead of three, often with one leaflet being larger or having a seam-like ridge called a raphe. This two-leaflet condition is the most frequent congenital heart defect, affecting approximately 0.5% to 2% of the general population. The abnormal structure and uneven size fundamentally alter the mechanics of the valve’s opening and closing motions.
Long-Term Implications of Abnormal Valve Structure
The structural difference of a bicuspid valve causes it to handle mechanical stress differently, leading to earlier wear and tear. Uneven flexing and turbulent flow patterns eventually cause the leaflets to become stiff and calcified sooner. This process leads to Aortic Stenosis, a condition where the valve opening narrows and restricts the amount of blood exiting the heart.
The abnormal structure may also fail to close completely, resulting in Aortic Regurgitation. This means the valve leaks, allowing blood to flow backward into the left ventricle after each heartbeat. Both stenosis and regurgitation force the left ventricle to work harder, which can lead to progressive heart failure. People with BAV are also at increased risk of developing an enlarged aorta (aortopathy or aneurysm) and are more susceptible to infective endocarditis due to irregular blood flow patterns.