More than 8 million people in Europe and the US suffer from moderate to severe mitral valve regurgitation. It is defined as backflow (leaking) of blood from the left ventricle into the left atrium of the heart due to insufficient valve closure. Symptoms include light-headedness, shortness of breath, fatigue and chest pain. While small leaks are usually not considered a problem, more severe cases weaken the heart over time and lead to heart failure.