Barlow syndrome: Barlow syndrome is mitral valve prolapse (also known as "click murmur syndrome"), the most common heart valve abnormality, affecting 5-10% of the world population. Most patients have no symptoms and require no treatment. However, the condition can be associated with fatigue and/or palpitations. The mitral valve prolapse can often be detected by a doctor during examination of the heart and can be confirmed with an echocardiogram. Patients are usually given antibiotics prior to any procedure which might introduce bacteria into the bloodstream, including dental work and minor surgery.