Valvular heart disease can cause mitral regurgitation and mitral stenosis. Rheumatic fever is a common cause of valvular heart disease and results in scarring of the heart valves over multiple attacks. Mitral stenosis causes the mitral valve to narrow over time, increasing the pressure in the lungs and right side of the heart. Mitral regurgitation occurs when the mitral valve does not close properly, allowing blood to flow back into the left atrium. Both conditions can cause shortness of breath and heart failure if left untreated. Echocardiography is the primary test used to diagnose valvular heart disease and determine severity.