What happens with valves that don't open well (stenosis)?

stenosis cause the chamber behind the narrowed valve to have to work harder. Just as when a hose is kinked, the pressure in that chamber will increase. The heart can usually compensate for this when the narrowing is mild by becoming thicker and stronger. If the narrowing progresses however, this mechanism will no longer be effective, and congestive heart failure and arrhythmias may occur.