The mitral valve separates the upper and lower chambers from the left side of the heart, helping the blood in this part to flow in one direction. This valve is closed to prevent blood from returning as soon as the heart beats (contracts). Mitral valve prolapse is a heart problem that occurs when the valve does not close properly. Normally this alteration is harmless, does not affect the health, reason why the majority of the people do not know that they suffer it.