What are the differential functions of primary and secondary chordae of the anterior mitral leaflet in an isolated pig heart model?
Primary chordae are essential for mitral valve competence, while secondary chordae play a key role in maintaining left ventricular geometry and function.
BACKGROUND: The aim of this study was to compare the function of the primary chordae attached to the free edge with that of the secondary chordae attached to the ventricular surface of the anterior mitral leaflet. METHODS AND RESULTS: An isolated working pig heart model was used. Three groups of 7 hearts were compared: Group A was the control group with intact leaflets. In group B, the primary chordae of the anterior leaflet were sectioned and the secondary chordae were left intact before assembly of the working heart model. In group C, the secondary chordae were sectioned and the primary chordae left intact. In group B, atrial and ventricular pressure evidenced dramatic mitral regurgitation. Video monitoring showed significant prolapse of the free edge of the anterior leaflet. Acute mitral regurgitation accounted for the decrease in aortic flow rate to 30 mL/min, significantly lower than in the control group (P=.006). In group C, sectioning of the secondary chordae left a competent mitral valve together with good coaptation of the anterior and posterior leaflets shown by video monitoring. However, aortic flow was lower than in the control group (P=.007), and ultrasonomicrometry evidenced impaired function (P=.009). CONCLUSIONS: This study suggests that the primary and secondary chordae of the mitral subvalvular apparatus have different functions. The primary chordae of the anterior leaflet appeared to be more involved in mitral valve competence, whereas the secondary chordae appeared to be more involved in left ventricular geometry and function.
Obadia et al. (Tue,) studied this question.