Mitral stenosis is a heart condition where the mitral valve does not open fully, restricting blood flow from the left atrium to the left ventricle. This narrowing can lead to increased pressure in the heart and lungs, causing symptoms like shortness of breath, fatigue, and palpitations. The condition is often caused by rheumatic fever, a complication of untreated strep throat, or can be due to age-related changes. Diagnosis typically involves echocardiography, which uses sound waves to create images of the heart, allowing doctors to assess the severity of the stenosis and plan appropriate treatment.