Mitral regurgitation (MR) is a heart condition in which blood leaks backwards from the left ventricle into the left atrium as a result of impaired closure of the valvular leaflets.
As a result of this condition, the heart fails to pump blood efficiently and is forced to work harder, with clinical outcomes that may include fatigue, pulmonary edema, shortness of breath while resting and ultimately, heart failure.
Mitral regurgitation is divided into two types: degenerative (primary) and functional (secondary). Primary MR is due to mitral valve pathology, such as prolapse of the mitral valve leaflets or ruptured chordae. Secondary MR is commonly caused by left ventricular remodelling and/or left atrial dilatation, which leads to incomplete leaflet coaptation.
The survival rate decreases in patients with moderate to severe MR. Treatment of MR attempts to minimize the formation or worsening of pathological implications (such as ventricular remodeling), delay heart failure (thereby lengthening time to transplant) and improve survival rate .
1. Dariush Mozaffarian et al., Heart Disease and Stroke Statistics—2015
Mitral valve regurgitation can progress slowly and patients may exhibit no symptoms for many years. MR symptoms are dependent on the severity and speed at which the condition develops and can include heart murmur, shortness of breath (especially when lying down), dizziness, fatigue during increased physical activity (and even at rest), and irregular heartbeat.
Treating Mitral Regurgitation
MR cannot be treated with medications. Medications are prescribed to relieve symptoms, to reduce risk of stroke and to maintain heart rhythm. In addition to a very high rate of heart failure hospitalization, patients’ one-year mortality rate is 20% and five-year mortality rate is 50%, indicating very poor outcomes for medically managed patients with severe functional MR. 
Mitral valve repair or replacement is performed via open-heart surgery while using a cardiopulmonary bypass. However, many patients who require surgery have other co-morbidities that preclude it. According to Duke Databank, out of 1,538 patients, only 5.9% of patients with severe FMR who demonstrated an ejection fraction of less than 30% were found to be compatible with surgery. 
PERCUTANEOUS TRANSCATHETER PROCEDURE
Transcatheter mitral interventions constitute a therapeutic alternative to surgery with prognostic and symptomatic benefits for patients for whom surgery poses a high risk. 
5. Sachin S. Goel et al., J Am Coll Cardiol. 2014;63(2):185-186
6. As presented by Dr. Michael Mack in ACC 2015.
7. Glower DD et al. Percutaneous mitral valve repair for mitral regurgitation in high-risk patients: results of the EVEREST II study Am Coll Cardiol. 2014 Jul 15;64(2):172-81