The Current Therapy for Mitral Regurgitation

In addressing the current therapy for mitral regurgitation (MR), it is useful to distinguish primary MR from secondary (functional) MR. In primary MR, abnormalities of one or more of the components of the mitral valve cause it to leak, imparting a volume overload on the left ventricle (LV). Severe prolonged primary MR leads to LV remodeling, myocardial dysfunction, heart failure, and death. Correction of MR, preferably by valve repair rather than replacement, is curative. Severe MR by itself is considered an indication for repair in many centers, and mitral surgery (repair or replacement) should take place when even mild symptoms appear or when ejection fraction approaches 0.60 or end systolic dimension approaches 40 mm. In secondary MR, myocardial damage from infarction or cardiomyopathy produces papillary muscle displacement and annular dilatation, causing a normal valve to leak. Because the MR in this case is not the primary problem, the indications for mitral valve intervention are less certain and considerably more data are needed to aid us in selecting the most appropriate patients for surgical therapy. Percutaneous therapies for both primary and secondary MR have generated much interest, and many different percutaneous technologies are being developed. Future data from randomized trials will help clarify when and in whom these therapies are applicable.