Insuffisances mitrales ischémiques: Mécanisme et pronostic

Ischemic mitral regurgitation (IMR) is mitral regurgitation (MR) due to complications of coronary artery disease. Two mechanisms can be individualized. Acute MR secondary to ruptured papillary muscle is a rare but often fatal complication of myocardial infarction. We focus on functional MR, much more common, which occurs without any intrinsic valve disease. It was often underrated because of low murmur intensity but is observed between 15 and 20% after a myocardial infarction. The presence and degree of the regurgitation are related to local left ventricular remodeling. The apical and posterior displacement of papillary muscles leads to excess valvular tenting which in turn, in association with loss of systolic annular contraction, determines the severity of the regurgitation. IMR presence is associated with an excess mortality. The mortality risk is directly related to the degree of the regurgitation and a regurgitant volume ≥ 30 ml or an effective regurgitant orifice ≥ 20 mm² define a high-risk group. In current clinical practice, IMR is mainly corrected with ring annuloplasty. However, this technique does not correct local alterations of left ventricular remodeling and its benefits on long-term outcome remains to be demonstrated.