The two conditions of a malfunctioning valve are stenosis and insufficiency. Read the transcript of a past WebMD chat on Endocarditis with Dr. Bryan Steinberg. This deposit, or stenosis, prevents the leaflets from opening as widely as they should and once could. The hole the blood must pass through when the leaflets are open becomes progressively smaller. The problem is that the heart still must pump the same amount of blood through a smaller and smaller opening.
Stenosis is one reason why valves are repaired or replaced.
Normally, when the valve leaflets close, they stay shut. This ensures that the blood flows through the heart in one direction only. When a valve does not close tightly, however, it is called valvular insufficiency, or leakage. This valvular insufficiency may allow blood to travel the wrong way. Both valvular stenosis and insufficiency can affect, separately or simultaneously, any heart valve, meaning that sometimes more than one valve is affected.