Importance of Anterior Mitral Basal Stay Chords for Left Ventricular Outflow Hemodynamics: A Computational Study

Abstract

Anterior mitral basal stay chords are transferred to correct prolapse of the anterior mitral leaflet (AML) and it has been supposed to transect the stay chords to treat functional ischemic mitral regurgitation. This numerical study seeks to clarify the effect of stay-chord transection (SCT) on hemodynamic aspects of left ventricular outflow. Two threedimensional left ventricular models including the left ventricular outflow tract and saddle-shaped mitral valve before and after SCT were constructed. After SCT, the anterior mitral leaflet was specified to be more concave and the aorto-mitral angle to be narrower than before SCT. Time-dependent turbulent flow in a flow range of 10∼28 L/min during rapid ejection was simulated using commercial software FLUENT. Left ventricular outflow before SCT was streamlined along the AML throughout rapid ejection. After SCT this flow was redirected in the vicinity of the AML creating a zone of persistent lowmomentum recirculation associated with additional energy loss. Consequently, the axial forward flow delivered into the aorta after SCT was diminished. High wall shear stress, concentrated at the fibrous trigones before SCT, was redistributed along the inter-trigonal distance after SCT. The stay chords, which maintain the natural profile of the AML, are essential to streamline left ventricular outflow, facilitate flow delivery into the aorta, minimize dissipation of potential energy, and create an optimum wall shear stress pattern that conforms to the fibrous trigones. Transection of stay chords compromises local hemodynamics, resulting in greater energy loss and unfavorable wall shear stress distribution. The study emphasizes the importance of preserving stay-chord function in mitral valve surgeries.