Editing Heart (section)

==== Valvular heart disease ====<!-- Murmurs-->
{{main|Valvular heart disease}}{{listen|filename=Mitral Valve Prolapse.wav|title=Mitral Valve Prolapse murmur|description=Heart sounds of a 16 year old girl diagnosed with mitral valve prolapse and mitral regurgitation. Auscultating her heart, a systolic murmur and click is heard. Recorded with the stethoscope over the mitral valve.|format=[[wav]]}}Healthy heart valves allow blood to flow easily in one direction, and prevent it from flowing in the other direction. A diseased heart valve may have a narrow opening ([[stenosis]]), that restricts the flow of blood in the forward direction. A valve may otherwise be leaky, allowing blood to leak in the reverse direction ([[Regurgitation (circulation)|regurgitation]]). Valvular heart disease may cause breathlessness, blackouts, or chest pain, but may be asymptomatic and only detected on a routine examination by hearing abnormal heart sounds or a [[heart murmur]]. In the developed world, valvular heart disease is most commonly caused by degeneration secondary to old age, but may also be caused by infection of the heart valves ([[endocarditis]]). In some parts of the world [[Rheumatic Heart Disease|rheumatic heart disease]] is a major cause of valvular heart disease, typically leading to mitral or aortic stenosis and caused by the body's immune system reacting to a [[Group A streptococcal infection|streptococcal]] throat infection.<ref name=":4" />{{sfn|Davidson's|2010|pp=612–613}}