Heart valves are four small gates inside your heart that open and close with every heartbeat, keeping blood flowing in one direction. Each valve opens to let blood pass into the next chamber or artery, then snaps shut to prevent it from leaking backward. Your heart beats roughly 100,000 times a day, and these valves coordinate that entire flow.
The Four Heart Valves and Where They Sit
Your heart has four chambers: two upper chambers (atria) and two lower chambers (ventricles). A valve sits at each exit point, controlling traffic between chambers and into the major blood vessels.
- Tricuspid valve: Located between the right atrium and right ventricle. It lets blood drop down into the right ventricle and prevents it from washing back up.
- Pulmonary valve: Sits between the right ventricle and the pulmonary artery, which carries blood to the lungs to pick up oxygen.
- Mitral valve: Located between the left atrium and left ventricle. Oxygen-rich blood returning from the lungs passes through this valve on its way to being pumped out to the body.
- Aortic valve: Sits between the left ventricle and the aorta, the large artery that delivers blood to the rest of your body.
These four valves fall into two structural categories. The tricuspid and mitral valves sit between upper and lower chambers, and they’re anchored by cord-like strings that tether their flaps to the heart muscle below, preventing them from blowing backward when pressure builds. The pulmonary and aortic valves sit at the exits to major arteries and have a simpler cup-shaped design. The tricuspid valve has three flaps (leaflets), the mitral valve has two, and both the pulmonary and aortic valves have three crescent-shaped cusps.
How Blood Moves Through All Four Valves
Blood follows a single loop through the heart, passing through every valve in a set order. Oxygen-poor blood from the body enters the right atrium, flows through the tricuspid valve into the right ventricle, then gets pumped through the pulmonary valve toward the lungs. In the lungs, blood picks up fresh oxygen and releases carbon dioxide.
That oxygen-rich blood returns to the left atrium, passes through the mitral valve into the left ventricle, and finally gets pushed through the aortic valve into the aorta, where it flows to the rest of your body. The left ventricle generates the strongest pressure because it needs to push blood the farthest, which is why the mitral and aortic valves handle the heaviest workload.
The valves don’t have muscles of their own. They open and close passively based on pressure differences. When a chamber contracts and pressure behind the valve rises, the valve swings open. Once blood passes through and pressure drops, the valve falls shut. This happens so precisely that a healthy valve barely allows a drop of backflow.
What Heart Valves Are Made Of
Heart valve tissue is surprisingly complex. Each leaflet is built from layered sheets of connective tissue, not just a single membrane. The core layers include a dense collagen sheet (the fibrosa) that gives the valve its structural strength and a looser, sponge-like layer (the spongiosa) that acts as a shock absorber during the constant opening and closing cycle. Thin surface layers line each side, helping the valve interact smoothly with flowing blood.
This layered construction is what allows valves to withstand decades of nonstop mechanical stress. When those tissue layers degenerate from age, infection, or disease, the valve stops sealing properly.
Common Valve Problems
Heart valve disease affects tens of millions of people worldwide. A 2021 global estimate found roughly 54.8 million cases of rheumatic heart disease (caused by untreated strep infections damaging valve tissue), 13.3 million cases of calcific aortic valve disease, and 15.5 million cases of degenerative mitral valve disease. In the United States alone, over 3.6 million people live with degenerative mitral valve disease and about 2.5 million with calcific aortic valve disease.
The three main types of valve malfunction are:
Stenosis happens when a valve opening becomes too narrow for blood to pass through easily. The flaps may thicken, stiffen, or fuse together over time, often from calcium buildup. The heart compensates by pumping harder, which can eventually exhaust the muscle. Aortic stenosis is the most common form in older adults.
Regurgitation (also called insufficiency or backflow) occurs when a valve doesn’t seal tightly, letting blood leak backward. This can happen because the leaflets are the wrong size or shape, or because the valve opening has stretched. The heart ends up doing extra work because some blood flows in the wrong direction with every beat.
Prolapse is most common in the mitral valve. One or both flaps bulge backward into the upper chamber instead of closing flat. Many people with mild mitral valve prolapse never notice symptoms, but in some cases, the bulging prevents a tight seal, leading to regurgitation.
Signs That a Valve Isn’t Working Well
Mild valve problems often produce no symptoms for years. As the condition progresses, common signs include shortness of breath during activity or when lying flat, unusual fatigue, swelling in the ankles or feet, dizziness, and a fluttering or racing heartbeat. Some people first learn about a valve issue when a doctor hears an unusual sound (a heart murmur) through a stethoscope during a routine exam.
Symptoms tend to appear gradually. By the time you feel them during everyday activities like climbing stairs or walking across a parking lot, the valve problem is usually moderate to severe. An echocardiogram, which uses ultrasound to create a live image of the heart, is the standard way to see how well the valves are opening, closing, and handling blood flow.
Repair and Replacement Options
When a damaged valve causes significant symptoms or threatens heart function, the two main approaches are repairing the existing valve or replacing it entirely. Repair is generally preferred when possible, especially for the mitral valve, because it preserves your own tissue and avoids the trade-offs that come with an artificial valve.
When replacement is necessary, there are two types of artificial valves. Biological (bioprosthetic) valves are made from pig or cow tissue. They feel more natural to the body and don’t require lifelong blood-thinning medication, but they wear out over time. On average, a biological valve lasts about 10 years, though some hold up for over 20 years and others need replacing closer to seven. Mechanical valves are made primarily from a specialized form of carbon. They’re extremely durable and essentially last a lifetime, but the body tends to form clots on their surface, so you’ll need to take blood-thinning medication every day for the rest of your life.
The choice between the two depends on your age, lifestyle, and tolerance for either reoperation down the road or daily medication. Younger patients sometimes receive mechanical valves to avoid repeat surgeries, while older patients often choose biological valves to skip blood thinners. For certain valve conditions, newer catheter-based procedures allow a replacement valve to be delivered through a blood vessel rather than through open-chest surgery, significantly shortening recovery time.