In a normal, healthy heart, the blood flows freely through the valves when they are open but cannot leak through them when the valves are closed. Heart valves can become diseased, however, leading either to improper opening or improper closing of the valve.

In some disease states, the normal valve elasticity and compliance is lost over time and the valve becomes stiff, immobile, and unable to open completely, causing an obstruction to the free flow of blood (stenosis). Examples of diseases in which this occurs are mitral valve stenosis ensuing from rheumatic heart disease and aortic stenosis due to calcification and thickening of the aortic valve.

Alternatively, valves may close improperly and become leaky (regurgitant). This may occur because the heart has become enlarged or because the valve tissue has become degenerative for various reasons (valve infection, severe mitral valve prolapse, phen-fen use). Both valvular stenosis and regurgitation may cause an audible heart murmur.

Typical symptoms of valvular disease consist of shortness of breath and fatique. In severe cases, dizziness or fainting may occur. Valvular disease may also lead to heart rhythm disturbances.

Valvular disease is quantified and graded as mild, moderate, or severe. Mild or moderate valve stenosis or regurgitation are usually treated with medications. However, severe valvular stenosis or regurgitation requires surgical treatment. This involves open heart surgery with repair or removal of the diseased valve and replacement with a prosthetic valve. Two main types of prosthetic valves are currently used: mechanical tilting disc valves (made of metal and plastic) and tissue bioprosthetic valves (made of porcine or bovine tissue). Mechanical valves require that the patient be placed on lifelong blood thinner (warfarin), whereas bioprosthetic valves do not. However, mechanical valves in general are more durable and less likely to degenerate with time.

Patients with significant valvular disease or prosthetic valves are instructed to take prophylactic antibiotics prior to having any dental work, in order to prevent infection of the diseased/prosthetic valve.