Stenosis literally means narrowing. When heart valves are stenotic, they do not fully open and the passageway for blood flow is narrowed. And sometimes valves with stenosis do not close properly, allowing blood to flow backwards (regurgitate). Stenotic heart valves cause the heart to work harder, trying to pump blood through a smaller opening.
Stenosis can be present at birth, when valve leaflets or cusps are partially fused and narrow the passageway. Stenosis can also be a result of a condition, like rheumatic heart disease. But most commonly, stenosis is an age-related condition in which calcium deposits build up in the valve tissue over time and lead to stiffening and poor function.
Valve stenosis can occur in any of the four valves of the heart but is most common in the aortic and mitral valves.