Valvular heart disease refers to a condition where one or more of the heart's valves do not function properly. The heart has four valves—aortic, mitral, pulmonary, and tricuspid—that help regulate blood flow. When these valves become narrowed (stenosis) or leak (regurgitation), it can lead to various symptoms, including shortness of breath, fatigue, and swelling in the legs. This disease can result from various causes, including congenital defects, rheumatic fever, or age-related changes. Diagnosis typically involves imaging tests like echocardiograms, and treatment options may include medication or surgical procedures to repair or replace the affected valves.