Configuration of the mitral valves subvalvular complex and its effect on the chordal force distribution

Three mitral valves (MV) with annulus, leaflets, chordae tendineae (CT) and papillary muscles (PM) were extracted intact from fresh porcine hearts. The valves were inserted in an in vitro left heart simulator that provided physiological flow and transmitral pressures. Four C-shaped chordal force transducers were attached to four chordae tendineae; anterior strut, basal posterior, marginal posterior stem and a commissure. All four chordae originated from the posteromedial papillary muscle. The force transducers measured the force exerted on the four individual chordae during cardiac cycles, under different conditions: two peak transmitral pressures (120 mmHg and 150 mmHg) and three papillary muscle positions (normal, taut and slack). Taut was 5 mm from normal position, and slack 3 mm from normal position. The chordal force distribution changed with papillary muscle displacement. The anterior strut and the basal posterior chordae bore the biggest tension in normal and taut position, whereas the posterior marginal stem bore most of the tension in the slack papillary muscle position. Increasing transmitral pressure increased the magnitude of the chordal forces, but not the force distribution between the chordae.