Mitral regurgitation is a heart condition where the mitral valve does not close properly, allowing blood to flow backward into the left atrium when the left ventricle contracts. This can lead to increased pressure in the heart and lungs, causing symptoms like shortness of breath and fatigue. The condition can be caused by various factors, including heart valve disease, rheumatic fever, or degenerative changes in the valve. Treatment options may include medication to manage symptoms or surgical procedures to repair or replace the damaged valve, depending on the severity of the condition.