Randomized Trials in Moderate Ischemic Mitral Regurgitation

Ischemic mitral regurgitation (MR) occurs as a consequence of left ventricular (LV) remodeling after myocardial infarction and is a reproducible marker of reduced event-free survival over the intermediate to long term.1–4 Mortality risk increases as a function of MR severity and is higher among patients with moderate or severe ischemic MR compared with patients with trivial or mild MR. In this context, the mitral valve has been described as an anatomically normal innocent bystander, although structural changes in leaflet architecture consequent to abnormal stretching have been described.5 MR results from a combination of apical and lateral papillary muscle displacement, leaflet tethering, annular dilatation, and reduced closing forces. Ischemic MR and its natural history derive more from underlying LV dysfunction and less from primary (organic) valve failure, although both mechanisms may contribute in individual patients. The pathophysiological principles that underlie treatment recommendations for patients with organic MR from myxomatous degeneration (eg, fibroelastic deficiency or Barlow syndrome) are, therefore, not directly applicable to the management of patients with functional, ischemic MR. In addition, there are important differences in the Doppler echocardiographic thresholds used to define organic and functional MR severity. Although severe organic MR is usually characterized by an effective regurgitant orifice area ≥0.4 cm2 and regurgitant volume (RV) >60 mL/beat, these cut points are significantly lower for patients with functional MR (effective regurgitant orifice area ≥0.2 cm2 and RV >30 mL/beat, respectively).6,7 MR severity in any individual patient should not be defined solely on the basis of 1 or 2 quantitative parameters but rather on an integrative assessment that takes into account additional supportive findings, such as left atrial and LV chamber sizes, the density of the Doppler continuous wave regurgitant signal, mitral E wave height, and the pattern of pulmonary vein …