MITRAL SUBVALVULAR APPARATUS - DIFFERENT FUNCTIONS OF PRIMARY AND SECONDARY CHORDAE

Background The aim of this study was to compare the function of the pr imary chordae attached to the free edge with that of the secondary cho rdae attached to the ventricular surface of the anterior mitral leafle t. Methods and Results An isolated working pig heart model was used. T hree groups of 7 hearts were compared: Group A was the control group w ith intact leaflets. In group B, the primary chordae of the anterior l eaflet were sectioned and the secondary chordae were left intact befor e assembly of the working heart model. In group C, the secondary chord ae were sectioned and the primary chordae left intact. In group B, atr ial and ventricular pressure evidenced dramatic mitral regurgitation. Video monitoring showed significant prolapse of the free edge of the a nterior leaflet. Acute mitral regurgitation accounted for the decrease in aortic flow rate to 30 mL/min, significantly lower than in the con trol group (P=.006). In group C, sectioning of the secondary chordae l eft a competent mitral valve together with good coaptation of the ante rior and posterior leaflets shown by video monitoring. However, aortic flow was lower than in the control group (P=.007), and ultrasonomicro metry evidenced impaired function (P=.009). Conclusions This study sug gests that the primary and secondary chordae of the mitral subvalvular apparatus have different functions. The primary chordae of the anteri or leaflet appeared to be more involved in mitral valve competence, wh ereas the secondary chordae appeared to be more involved in left ventr icular geometry and function.