Your heart has four valves that act as one-way gates, opening and closing with every heartbeat to keep blood flowing in the right direction. Each valve opens when pressure builds behind it and snaps shut once blood has passed through, preventing any backward flow. Together, these four valves coordinate roughly 100,000 times a day to move blood through the heart’s chambers and out to the lungs and body.
The Four Heart Valves and Where They Sit
The heart has two upper chambers (atria) and two lower chambers (ventricles), and a valve guards the exit of each one. The valves fall into two pairs based on their location and structure.
The first pair sits between the upper and lower chambers:
- Tricuspid valve: controls flow from the right atrium into the right ventricle. It has three flaps, or leaflets.
- Mitral valve: controls flow from the left atrium into the left ventricle. It has two leaflets, making it the only heart valve without three.
The second pair sits where the ventricles connect to the major arteries leaving the heart:
- Pulmonary valve: opens to let blood pump from the right ventricle into the pulmonary artery, which carries it to the lungs to pick up oxygen.
- Aortic valve: opens to let oxygen-rich blood flow from the left ventricle into the aorta, the body’s largest artery, which distributes it everywhere else.
How Valves Open and Close
Heart valves are passive structures. They don’t have muscles of their own. Instead, they respond to pressure differences on either side. When the pressure behind the valve is greater than the pressure in front of it, the leaflets push open and blood flows through. The moment pressure on the other side rises higher, the leaflets swing shut.
This happens in a predictable rhythm during each heartbeat. When the ventricles relax, the tricuspid and mitral valves open so blood can fill them from the atria above. When the ventricles contract, those valves close and the pulmonary and aortic valves open, sending blood out into the arteries. As the ventricles finish contracting, the arterial valves close to prevent blood from sliding back in.
What Keeps the Valves From Flipping Inside Out
The tricuspid and mitral valves face a tough job. When the ventricles squeeze with full force, the pressure could easily push their thin leaflets upward into the atria, like an umbrella blowing inside out in the wind. To prevent this, each leaflet is anchored by thin, cord-like strands of connective tissue called chordae tendineae. These cords connect the edges of the leaflets to small muscles on the ventricle wall (papillary muscles), holding them in position during the most forceful part of each heartbeat.
The pulmonary and aortic valves don’t need this anchoring system. Their leaflets are shaped like crescent moons (which is why they’re called semilunar valves), and this curved design lets them catch blood that tries to flow backward, filling like small pockets and pressing together to form a tight seal.
The Heartbeat Sounds You Can Hear
The classic “lub-dub” sound of a heartbeat comes directly from valve closures. The first sound (“lub”) happens when the mitral and tricuspid valves shut as the ventricles begin to contract. The second sound (“dub”) occurs when the aortic and pulmonary valves close at the end of contraction. Doctors listen to these sounds with a stethoscope because changes in their timing, loudness, or quality can signal valve problems. An extra whooshing noise between the normal sounds, called a murmur, often indicates blood is flowing turbulently through a valve that isn’t fully opening or closing.
What Goes Wrong: Stenosis and Regurgitation
Valve disease generally takes one of two forms. In stenosis, the valve opening becomes too narrow. The leaflets may stiffen, thicken, or fuse together, forcing the heart to pump harder to push blood through a smaller gap. In regurgitation (also called insufficiency or backflow), the valve doesn’t seal completely when it closes. Blood leaks backward, meaning the heart has to pump some of the same blood twice to deliver enough to the body.
Both problems make the heart work harder than it should. Over months and years, this extra workload can enlarge the heart chambers and weaken the muscle. Some people are born with malformed valves, but most valve disease develops later in life. Calcification, where calcium deposits gradually build up on the leaflets, is the leading cause in older adults. The prevalence of aortic and mitral valve disease in people aged 70 to 89 is 20 to 50 times higher than in people aged 50 to 59.
Globally, about 24.2 million people have mitral regurgitation, making it the most common type of valve disease. Around 9.4 million have calcific aortic valve disease.
How Valve Problems Are Detected
An echocardiogram, essentially an ultrasound of the heart, is the primary tool for evaluating valve function. It shows the valves opening and closing in real time, measures how fast blood is moving through each one, and reveals any backward leaking. Doctors can assess the size and shape of the heart chambers, check how strongly the heart is pumping, and spot structural changes in the leaflets themselves. Multiple viewing angles and color Doppler imaging help pinpoint exactly where a valve is leaking and how severe the problem is.
Many valve problems are discovered before symptoms appear, often when a doctor hears a murmur during a routine exam and orders an echocardiogram to investigate.
How Damaged Valves Are Treated
Mild valve disease often needs no treatment beyond regular monitoring. When a valve problem becomes severe enough to cause symptoms like breathlessness, fatigue, or chest tightness, or when imaging shows the heart is straining to compensate, repair or replacement becomes necessary.
Valve repair preserves the patient’s own valve by reshaping leaflets, patching holes, or reinforcing the ring of tissue that supports the valve. It’s preferred when possible, especially for the mitral valve, because outcomes tend to be better and there’s no need for lifelong blood-thinning medication afterward.
When repair isn’t feasible, the valve is replaced entirely. Replacement valves come in two types. Mechanical valves are made from durable synthetic materials and can last a lifetime, but they require daily blood-thinning medication to prevent clots from forming on the artificial surface. Tissue (bioprosthetic) valves are made from animal tissue, typically pig or cow. They don’t usually require long-term blood thinners, but they wear out over time and may eventually need to be replaced again.
For aortic valve replacement specifically, a less invasive option called transcatheter aortic valve replacement (TAVR) allows a new valve to be delivered through a catheter threaded up from the leg, avoiding the need to open the chest. The choice between TAVR and traditional open-heart surgery depends on the patient’s age, overall health, anatomy, and how likely they are to need another valve procedure later in life. Younger patients with longer life expectancies may benefit from surgical replacement to keep more options available for the future.