Fig. 1.

Subvalvular left ventricular (LV) base and papillary muscle (PM) dynamics in normal subjects (top) and patients with late systolic mitral valve prolapse (MVP, bottom). Top: from early to late systole, the mitral valve (MV) annulus-to-PM base distance (distance 1) shortens to distance 1′. The PM base-to-tip distance (distance 2) shortens to distance 2′. Consequently, the PM tip depth from the MV annulus (distance 3) remains approximately constant (distance 3 = distance 3′). These dynamics allow approximately constant MV coaptation depth throughout systole in normal subjects. Bottom: in contrast, PM tip depth (distance 3) significantly shortens in patients with late systolic MVP (distance 3 > distance 3′), accompanying a progressive superior shift of MV during systole (equal to late systolic MVP as indicated by red arrows). Details and causal relation of these subvalvular abnormalities have yet to be clarified.