Your heart consists of 4 chambers that receive and send blood to the lungs and body.
Disorders affecting valves can either cause stenosis (a narrowing) or regurgitation (leakage after the valve has closed). Depending on what valve is involved and how severe the damage is it may result in symptoms of heart failure (see above), as it makes the heart pump inefficiently.
Suspicion of a heart valve problem is usually picked up by your doctor when they listen to your heart and hear a murmur. A murmur is heard with the stethoscope and is turbulence of blood flow that occurs through a narrowed or leaky valve. Not all heart murmurs mean serious problems but are best investigated further.