Mitral regurgitation: what causes the leakage is fundamental to the outcome of valve repair.

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Mitral regurgitation (MR) has become the predominant mitral valve disease as a result of the regression of rheumatic diseases and the aging of the population. The high prevalence in the elderly of degenerative and ischemic MR implies that MR is currently a public health problem. Recent data suggest that MR has severe outcome implications that are dependent on the degree of regurgitation, both for MR due to organic disease of the mitral valve and MR due to ischemic heart disease. This combination of high prevalence and relatively high risk requires careful examination of therapies applicable to MR. Unfortunately for patients with MR, therapeutic approaches for both medical and surgical treatment have not been evaluated by the state-of-the-art method—ie, by randomized clinical trials. Therefore, observational studies form the basis of our clinical decision-making process, and the quality of evidence is less than optimal. Our assessment of the improvement of outcome provided by various strategies (eg, medical treatment versus untreated observation, surgical treatment versus medical treatment of asymptomatic patients, valve repair versus valve replacement in patients who require surgery) is based on observational studies that have intrinsic limitations. The first implication of this situation is that we need (for a lack of a stronger word) appropriately designed randomized clinical trials comparing various strategies of treatment. The second implication is that it is not surprising that various observational studies, such as that presented by Thourani and colleagues in the present issue of Circulation ,1 may have findings different from each other in accordance with the population examined. Consequently, it is essential to examine the current status of our knowledge and determine how to interpret data that may seem to contradict existing information. See p 298 What does the current literature say about the potential outcome benefit of mitral valve repair for patients …