Transection of anterior mitral basal stay chords alters left ventricular outflow dynamics and wall shear stress.
OBJECTIVE
Anterior mitral basal stay chords are relocated to correct prolapse of the anterior mitral leaflet (AML); it has also been suggested that their transection might be used to treat functional ischemic mitral regurgitation. The study aim was to clarify the effect of stay chord transection (SCT) on the hemodynamic aspects of left ventricular outflow.


METHODS
Two three-dimensional left ventricular models including the left ventricular outflow tract and saddle-shaped mitral valve before and after SCT were constructed. After SCT, the AML was specified to be more concave and the aortomitral angle to be narrower than before SCT. Time-dependent turbulent flow in a flow range of 10 to 28 l/min during rapid ejection was simulated using the commercial software, FLUENT.


RESULTS
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, thereby creating a zone of persistent low-momentum recirculation associated with additional energy loss. Consequently, the axial forward flow delivered into the aorta after SCT was diminished. The high wall shear stress, which was concentrated at the fibrous trigones before SCT, was redistributed along the intertrigonal distance after SCT.


CONCLUSIONS
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 to create an optimum wall shear stress pattern that conforms to the fibrous trigones. Transection of the stay chords compromises local hemodynamics, resulting in greater energy loss and unfavorable wall shear stress distribution. The study results emphasize the importance of preserving stay chord function in mitral valve surgeries.
Xiong
Fangli
F
School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore.
Yeo
Joon Hock
JH
Chong
Chuh Khiun
CK
Chua
Yeow Leng
YL
Lim
Khee Hiang
KH
Ooi
Ean Tat
ET
Goetz
Wolfgang A
WA
D001783:Blood Flow Velocity / Q000502:physiology*; D006348:Cardiac Surgical Procedures / Q000379:methods*; D002815:Chordae Tendineae / Q000503:physiopathology / Q000601:surgery*; D003198:Computer Simulation; D006352:Heart Ventricles / Q000503:physiopathology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008943:Mitral Valve / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D008944:Mitral Valve Insufficiency / Q000503:physiopathology / Q000601:surgery*; D008955:Models, Cardiovascular; D033081:Shear Strength; D016277:Ventricular Function, Left / Q000502:physiology*