ABSTRACT
Mitral regurgitation [MR] resulting from prior myocardial infarction is now recognized as an important clinical sequel that directly impacts the long-term outcome of patients.' Defining Ischemic MR. Carpentier's pathophysiologic triad I defines the relationship between etiology, lesion[s] [pathological changes in the valve], and dysfunction [abnormalities of leaflet motion] that results in MR. Carpentier's classification of leaflet dysfunction is based on the motion of the margin of the leaflet in relation to the annular plane. Often authors use an etiologic definition for ischemic MR such as "mitral regurgitation resulting from prior myocardial infarction associated with normal mitral valve leaflets and chordae. In terms of defining ischemic MR it is important to note that the majority of patients have an etiologic basis of prior myocardial infarction, not an acute myocardial infarction or papillary ischemic event. Resulting wall motion abnormalities and left ventricular remodeling leading to lateral and apical displacement of papillary muscles are the key pathophysiologic events. The predominant mitral valve lesion, therefore, is leaflet tethering, mainly of the posterior-medial scallop of the posterior leaflet [P-3] adjacent to the posterior commissure area, particularly in the setting of posterior infarction. Mitral annular dilatation often accompanies leaflet tethering as an associated lesion. The leaflet dysfunction resulting in the most common form of ischemic MR is Type IIIb. with restricted motion of the margin of the leaflet[s] in systole. Therefore for the majority of patients ischemic MR is defined by the presence of the following [a] prior history of myocardial infarction [b] tethering of predominantly the posterior-medial scallop of the posterior leaflet, and [c] Type III b Carpentier dysfunction with restricted leaflet motion in systole. Other forms of ischemic MR are less common. Type I dysfunction without leaflet restriction [normal leaflet motion] and isolated annular dilatation can occur in the setting of isolated basilar rnyocardial infarction Some patients with ischemic MR have Type II dysfunction [excess leaflet motion], resulting from either an acute [ruptured papillary muscle] or chronic [fibrotic and elongated papillary muscle] myocardial ischemic event. It should be emphasized that the prior concept of "acute ischemia with papillary muscle dysfunction" that would reverse with revascularization is now recognized to be valid in only a small percentage of patients with ischemic MR. This review will concentrate on ischemic MR with restricted leaflet motion that is most frequently seen in clinical practice