Mitral Regurgitation

Mitral regurgitation (MR) is the most common valvular abnormality worldwide, affecting over 2% of the total population, and has a prevalence that increases with age. MR is the retrograde flow of blood from the left ventricle (LV) into the left atrium (LA) through the mitral valve (MV), causing a systolic murmur heard best at the apex of the heart with the sound radiating to the left axilla (see  Mitral Regurgitation During Systole). The mitral valve consists of 2 leaflets (anterior and posterior) sitting within the annulus. The posterior mitral leaflet originates from the LA endocardium. The leaflets are supported by a subvalvular apparatus comprising 2 papillary muscles (anterolateral and posteromedial) that arise from the LV myocardium and the chordae tendineae.    Mitral regurgitation is subdivided into  and .  Also called degenerative or organic. Resulting from the structural deformity of or damage to the leaflets, chordae, or papillary muscles, causing leaflets to close insufficiently during systole. Common causes: papillary muscle rupture, mitral valve prolapse (MVP), or leaflet perforation . Also called functional or ischemic. Due to left ventricular wall motion abnormalities (ie, ischemic cardiomyopathy) or left ventricular remodeling (ie, dilated cardiomyopathy). No structural problems with the valve itself . Leads to mitral annular dilatation or displacement of papillary muscles, causing retrograde flow from improperly closed mitral valve leaflets. The Carpentier Classification divides mitral regurgitation into 3 types based on the leaflet motion: Type 1: Normal leaflet motion: Caused by annular dilation or leaflet perforation. Regurgitation jet directed centrally. Type 2: Excessive leaflet motion: Caused by papillary muscle rupture, chordal rupture, or redundant chordae. Eccentric jet directed away from the involved leaflet. Type 3: Restricted leaflet motion: IIIa: Leaflet motion restricted in both systole and diastole: Caused by rheumatic heart disease. Normal papillary muscles. Jet may be centrally or eccentrically directed . IIIb: Leaflet motion restricted in systole : Caused by papillary muscle dysfunction or left ventricular dilation. Abnormal papillary muscles. Jet may be centrally or eccentrically directed .