Geometric distribution of chordae tendineae: An important anatomic featurein mitral valve function

Background and aim of the study: This study examined the geometric distribu tion of chordae tendineae and their importance in compensating for papillar y muscle (PM) displacement. Methods: Anatomic, chordal mechanics and hemodynamic measurements were perf ormed with porcine mitral valves. For hemodynamic measurements, physiologic al pulsatile flow conditions were maintained, and PM positions varied. Leaf let coaptation was documented by 2-D echocardiography, and regurgitation me asured directly. Results: Anatomic measurements showed the sum of marginal leaflet and margi nal chordal lengths to exceed 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 pos terior leaflets). Triangular structures existed between basal chordae and m arginal chordae with the marginal leaflet as the third side. Basal chordae resisted apical PM displacement in static experiments, while marginal chord ae governed leaflet closure in hemodynamic experiments. Under pulsatile flo w conditions, apical PM displacement decreased leaflet coaptation length an d increased regurgitation (9.4 +/- 2.1 versus 4.0 +/- 1.6 mi). When margina l chordae were fused to the basal chordae, eliminating the role of the marg inal chordae, severe regurgitation resulted (28.5 +/- 5.0 mi with apical PM displacement). Conclusion: Based on triangular structures involving the basal and marginal chordae, a compensatory mechanism was described which explains how the sev erity of mitral regurgitation can vary following PM displacement. Basal cho rdae provide a constant connection between the annulus and papillary muscle s, while marginal chordae maintain marginal leaflet flexibility, governing proper valve closure. This study relates chordal distribution to normal val ve function, and provides a better understanding of breakdown in valve func tion under pathophysiological conditions.