Differential tension between secondary and primary mitral chordae in an acute in-vivo porcine model.

Background And Aim Of The Study: Chordae tendineae may be instrumental for valvular-ventricular interaction, i.e. the reciprocal exchange of force between the left ventricular myocardium and the mitral apparatus. Chordae tendineae are divided into primary leading edge chordae and secondary belly chordae, and differences in thickness and distribution may reflect different functions of the two types. Primary chordae may be fundamental for leading edge control and for correct leaflet coaptation, while secondary chordae may act as the main mediators of valvular-ventricular interaction. It was postulated that tension in secondary chordae of the anterior leaflet is greater than in the primary chordae. The study aim was to investigate the distribution of chordae tendineae tension in the porcine mitral valve in vivo.

Methods: During extracorporeal bypass, miniature chordal force transducers were implanted on four chordae in 23 Danish Landrace pigs. Chordae tendineae tension was recorded online in the open-chest condition with spontaneous circulation in three different hemodynamic conditions: baseline with no intervention; partial aortic occlusion; and during dobutamine infusion.

Results: Systolic tension in secondary chordae under baseline conditions was significantly higher than in primary chordae (0.7 N versus 0.2 N, respectively). No significant impact on this distribution by changing the hemodynamic condition could be identified.

Conclusion: Chordal tension is distributed towards the secondary chordae, with a tension more than three-fold that in the primary counterpart. The magnitude of chordal tension seems to be determined primarily by ventricular pressure. This finding supports the hypothesis that secondary chordae are more important mediators of the valvular-ventricular interaction than are primary chordae.