Left Ventricular Ejection Index as a Marker of Early Myocardial Dysfunction in Primary Mitral Regurgitation

Mitral valve prolapse (MVP) is a common disorder affecting 2% to 5% of the general population (7.8 million individuals in the United States and 176 million individuals worldwide),1–4 and it is the most important cause of primary mitral regurgitation (MR) requiring surgery.5 In addition to progressive MR, MVP is associated with endocarditis, heart failure, and even sudden death.4 In the setting of severe primary MR, the left ventricle (LV) is affected by a significant volume load leading to compensatory adaptations that vary considerably depending on the prolonged clinical course of MR.6 In acute MR, late systolic volume is reduced and afterload is low, but as the ventricle enlarges and adapts to the chronic volume overload, afterload gradually increases. During the compensated stage of chronic MR, LV enlargement results from remodeling of the extracellular matrix with dissolution of collagen and rearrangement of myocardial fibers.7 Moreover, new sarcomeres are added in series, and at the ventricular level, eccentric hypertrophy develops.6 Consequently, preload (at the sarcomere level), afterload (at the ventricular level), and LV ejection fraction (LVEF) are normal, whereas total stroke volume is increased as a result of the large end-diastolic volume. The transition to decompensated chronic MR may occur as a consequence of a progressive increase in regurgitant volume, a decrease in LV contractile function, an increase in afterload, or a combination of these factors. During this stage, LVEF typically declines to 50% to 60%. Finally, decompensated MR is characterized by substantial and progressive LV dilation, elevated LV diastolic pressure, increased systolic wall stress, and an LVEF of u003c50%. The decline in LVEF is a consequence of depressed myocardial contractile state, LV afterload excess, or both.6 Although predominantly based on mitral valve replacement data, early echocardiographic studies have demonstrated a frequent decline …