What would happen if a valve in the heart stopped working properly?

One result could be heart failure, which despite the sound of it is not an acute sudden and complete termination of heart function. If the 'left heart' fails, the part of the heart that specializes in moving blood from the lungs to the body, then there is usually a build-up over time of fluid in the lungs. If the 'right heart' fails, the part of the heart that moves blood from the body to the lungs for oxygenation, then there may be edema (swelling) in the body's extremities.