Mitral valve prolapse: a review of the literature

M valve prolapse (MVP) is a common valvular disorder characterized by abnormalities of the mitral valve apparatus that result in “billowing” of 1 or both mitral leaflets into the left atrium during systole, with or without mitral regurgitation (MR).1–3 It is the most frequently diagnosed valve abnormality in the industrial world,4,5 and the most common primary cause for dysfunction requiring mitral valve repair or replacement.6 Clinical classification may have significant overlap and “the pathogenesis of symptoms is not completely understood.”7 The overall incidence (by echocardiography) in the Framingham study was 5%, with a frequency in women approximately twice that of men.8 Table 1 highlights the variability in the prevalence of MVP by different diagnostic methods. MVP is classified as an inheritable connective tissue disorder that is regarded as an autosomal dominant disorder with variable penetrance and is divided into primary and secondary MVP. Primary MVP accounts for the vast majority of the cases and many, but not all, of these are associated with myxomatous degeneration of the mitral valve (MV). Secondary MVP is caused by chordae tendineae rupture and/or abnormal left ventricular (LV) wall motion. Potential causes of secondary MVP include coronary artery disease, rheumatic heart disease, cardiomyopathies, and infective endocarditis.9 Also, MVP may be associated with heritable disorders such as the Marfan syndrome, the Ehlers-Danlos syndrome, and other connective tissue disorders in which myxomatous degeneration of the MV is a prominent feature. Variables that decrease LV size can worsen MVP and similarly, variables that increase LV size can mask MVP. LV size is affected by blood volume, body position (supine, standing, etc.), and maneuvers (eg, Valsalva). A decrease in LV volume is the probable cause of the increased incidence of MVP in atrial septal defect and anorexia nervosa.10–12