Stenosis of the heart refers to a narrowing of one or more of the heart’s valves, preventing them from opening fully. When a valve can’t open all the way, the heart has to work harder to push blood through the smaller opening, and over time that extra strain can weaken the heart and reduce oxygen delivery throughout the body. It’s one of the most common forms of heart valve disease, particularly in older adults.
How Heart Valves Narrow
Your heart has four valves that act as one-way gates, keeping blood flowing in the right direction: the aortic valve, mitral valve, tricuspid valve, and pulmonary valve. Each valve has thin flaps (called leaflets) that open and close with every heartbeat. In stenosis, those flaps thicken, stiffen, or fuse together so the valve can no longer open completely. Blood has to squeeze through a smaller opening, which raises pressure inside the heart and forces it to pump harder with each beat.
Any of the four valves can develop stenosis, but aortic stenosis is by far the most common and most studied. Mitral stenosis is the next most frequently seen, while tricuspid and pulmonary valve stenosis are relatively rare in adults.
What Causes It
The most common cause in developed countries is age-related calcium buildup on the valve leaflets. Over decades, calcium deposits gradually stiffen the tissue, much like mineral deposits clog a pipe. This process typically affects the aortic valve and becomes clinically significant in people over 65.
Some people are born with a valve that has only two leaflets instead of the normal three (a bicuspid aortic valve). This structural difference accelerates calcium buildup and can lead to stenosis 10 to 20 years earlier than it would otherwise appear. Bicuspid aortic valve is the most common congenital heart defect, affecting roughly 1 to 2 percent of the population.
Rheumatic fever, caused by untreated strep throat, remains a major cause of mitral stenosis worldwide. The infection triggers inflammation that scars and stiffens the valve leaflets over time. While rheumatic heart disease has become uncommon in high-income countries, it still causes significant illness in parts of Africa, South Asia, and the Pacific Islands.
Symptoms and How They Progress
Stenosis often develops slowly over years or even decades, and many people have no symptoms in the early stages. The heart compensates by thickening its muscle wall to maintain adequate blood flow. Eventually, though, the narrowing becomes severe enough that the heart can no longer keep up.
The three hallmark symptoms of significant aortic stenosis are chest pain, fainting (or near-fainting), and shortness of breath. Chest pain during physical activity occurs in 30 to 40 percent of patients with severe aortic stenosis, even when their coronary arteries are completely normal. It happens because the thickened heart muscle demands more oxygen than it can get through the narrowed valve. Fainting episodes can strike suddenly and without warning, typically during exertion, when blood pressure drops because the heart can’t increase its output quickly enough.
Shortness of breath, especially with exertion, signals that the heart is beginning to fail under the strain. Of the three cardinal symptoms, the onset of breathlessness and other signs of heart failure carries the worst outlook. Once any of these symptoms appear, the disease has crossed a critical threshold. Without treatment, survival drops sharply: roughly 62 percent of people with severe symptomatic stenosis survive one year without valve replacement, and only 32 percent make it to five years. For older patients with severe symptomatic disease who don’t receive treatment, two-year mortality rates as high as 68 percent have been reported.
How Stenosis Is Diagnosed
An echocardiogram (an ultrasound of the heart) is the primary tool for diagnosing and grading valve stenosis. It shows the valve’s structure, measures how fast blood is flowing through it, and calculates the effective opening area. Faster blood flow through the valve indicates a tighter narrowing, similar to how water sprays faster when you partially cover a garden hose nozzle.
Doctors classify aortic stenosis as severe when the valve opening shrinks below 1.0 square centimeters (a healthy aortic valve opens to 3 to 4 square centimeters), the peak blood velocity across the valve reaches 4.0 meters per second or higher, or the average pressure difference across the valve hits 40 mmHg or more. Meeting any one of these thresholds is enough to indicate severe disease. Mild and moderate stenosis fall below these cutoffs and are typically monitored with periodic echocardiograms rather than treated immediately.
Treatment Options
No medication can reverse the physical narrowing of a stenotic valve. However, medicines play a supporting role in managing symptoms and complications. Diuretics can remove excess fluid to ease strain on the heart, blood pressure medications help reduce the workload, and drugs to control irregular heart rhythms may be needed as the condition progresses.
The definitive treatment for severe stenosis is replacing the damaged valve. There are two main approaches. Surgical aortic valve replacement (SAVR) is open-heart surgery in which the surgeon removes the diseased valve and sews in a new one, either mechanical or made from biological tissue. Transcatheter aortic valve replacement (TAVR) is a less invasive procedure where a new valve is threaded through a blood vessel (usually in the groin) and expanded inside the old valve, avoiding the need to open the chest.
TAVR was originally developed for patients too frail for open-heart surgery, and it has been a lifesaving option for that group. Its use has since expanded to lower-risk patients, but recent five-year data have raised important questions. A large meta-analysis of randomized trials found that TAVR resulted in a 5-year mortality rate of about 29.7 percent compared to 27.6 percent with surgical replacement in low- to intermediate-risk patients. That translates to a 12 percent higher relative risk of death with TAVR over five years. For younger, healthier patients expected to live well beyond five years, surgical replacement appears to offer better long-term durability. TAVR remains a strong option for older patients or those with limited life expectancy, where the less invasive approach and faster recovery provide a meaningful advantage.
What Happens Without Treatment
When stenosis goes untreated, the heart’s progressive struggle to push blood through the narrowed valve sets off a chain of problems. The heart muscle thickens, then eventually weakens. Pressure backs up into the lungs, causing fluid buildup and worsening shortness of breath. Irregular heart rhythms, particularly atrial fibrillation, become more likely as the heart chambers stretch under increased pressure. In mitral stenosis specifically, the backup of blood into the lungs can lead to pulmonary hypertension, a dangerous rise in pressure in the lung’s blood vessels.
The transition from “no symptoms” to “symptomatic” is the most important turning point in the disease. Before symptoms appear, many people with even moderate stenosis can live normally for years with regular monitoring. Once symptoms develop, the clock starts ticking. That’s why periodic echocardiograms matter so much for anyone diagnosed with valve narrowing: they help detect the progression toward severe disease before the heart sustains irreversible damage.