Here, I‘m going to answer adult valves only.
The most known sign of valve function or abnormalities is HEART MURMUR. During a physical examination, the doctor can hear an ABNORMAL MURMUR either from leakage or from narrowing in the heart valve. Sometimes, leakage and narrowing can be seen together. VALVE murmurs in young children and adolescents can sometimes be benign and may not cause any symptoms and may gradually disappear. Usually, in adults with valve problems, the valve develops slowly abnormal function, either leakage, narrowing, or both
Sometimes, a valve may have a minor defect at birth, but causes no problems in function until age 60 or older, when a valve starts to cause some symptoms and may need to be repaired or replaced. RARELY, A SUDDEN LEAKAGE IN A VALVE MAY OCCUR and may cause life-threatening shortness of breath and needs emergency surgery. It happens for the mitral valve in the presence of serious weakness in the mitral valve from a genetic disorder.
Symptoms are usually insidious or minor and develop very slowly over a few years. These symptoms usually slowly develop as shortness of breath during exercise of significant effort. An individual would notice that with time, doing the same physical effort becomes more taxing. When the function of the valve becomes worse, the symptoms become worse and shortness of breath would occur with much less effort. Chest discomfort may also develop as above depending on which valve. Serious narrowing in the aortic valve is more likely to cause chest pain than serious leakage in the mitral valve. DIZZINESS or fainting spells may occur. Palpitations and a tendency to have atrial fibrillation are not uncommon with serious leakage or narrowing in the mitral valve. Narrowing of the mitral valve is rarely seen nowadays and is typically caused by rheumatic fever, which is not much seen in the US and in the developed world. It still presents problems in the rest of the world.