Possible mechanisms for systolic anterior motion with anterior displacement of the papillary muscles (PM): (1) the normal posterior component of PM tension is reduced by anterior displacement of the muscle tips; (2) interposing the leaflets into the streamlines of flow causes drag forces with an anterior component; and (3) pulling up the posterior leaflet so that it meets the anterior leaflet closer to its base creates a long, overlapping residual leaflet, as seen clinically. This leaflet portion is relatively free to move anteriorly, unlike the coapted leaflet bodies that are restrained by the balance of ventricular and atrial pressures acting across them. The angle between the posterior leaflet and posterior wall is increased [PMID:7850958].