The geometric distribution of chordae tendineae and their importance in compensating for papillary muscle (PM) displacement, was examined. Anatomic, chordal mechanics and hemodynamic measurements were performed with porcine mitral valves. For hemodynamic measurements, physiological pulsatile flow conditions were maintained, and PM positions varied. Leaflet coaptation was documented by 2-D echocardiography, and regurgitation measured directly. The sum of marginal leaflet and marginal chordal lengths exceeded basal chordal length (1.8 ± 0.4 versus 2.8 ± 0.7 cm for anterior leaflets; 1.6 ± 0.3 versus 2.5 ± 0.6 cm for posterior leaflets). Triangular structures existed between basal chordae and marginal chordae, with the marginal leaflet as the third side. Basal chordae resisted apical PM displacement in static experiments; marginal chordae governed leaflet closure in hemodynamic experiments. Under pulsatile flow, apical PM displacement reduced leaflet coaptation length and increased regurgitation (9.4 ± 2.1 versus 4.0 ± 1.6 ml). Fusing marginal chordae to basal chordae eliminated the role of the marginal chordae and caused severe regurgitation (28.5 ± 5.0 ml with apical PM displacement). In conclusion, based on triangular structures involving the basal and marginal chordae, a compensatory mechanism was described which explains how mitral regurgitation severity varies following PM displacement. Basal chordae provide a constant connection between the annulus and papillary muscles, while marginal chordae maintain marginal leaflet flexibility, governing proper valve closure. This study relates chordal distribution to normal valve function, and provides an understanding of breakdown in valve function under pathophysiological conditions.