Mitral Valve Prolapse.

tant contribution in the evolution and refinement of diagnostic techniques that began when Barlow's angiographic observations provided the first rational basis for the origin of apical late systolic murmurs.3 Intracardiac phonocardiography subsequently recorded the clicks and late systolic murmur within the left atrium, a site appropriate for auscultatory events originating in the mitral apparatus.4 The advent of echocardiography catalyzed an explosion of interest,5 7 and a veritable epidemic of mitral valve prolapse ensued. M-mode records supplied a noninvasive method for detecting systolic mitral leaflet movement toward the left atrium,6,7 and two-dimensionally targeted M-mode echocardiography is still advocated.8 When twodimensional real-time imaging appeared upon the scene, the technique was heralded as ideally equipped to record the range of motion of the mitral leaflets relative to the annulus, and Doppler color flow interrogation soon furnished a sensitive means for detecting the presence and degree of mitral regurgitation.9 It rapidly became an article of faith that the diagnosis of mitral valve prolapse was established if the leaflets ascended above the plane of the annulus on two-dimensional imaging.10 This assumption has been called into question on at least two counts,9 first, by the disturbingly high frequency of the diagnosis of mitral prolapse in otherwise normal general populations,1" and, second, by the observation that mitral leaflets could appear to