Effect of the Location of Strut Chordae Insertion on Computational Modeling and Biomechanical Evaluation of Mitral Valve Dynamics  
[PERSON]  
Department of Biomechatronic Engineering, Sungkyunkwan University, Suwon 16419, Korea; [EMAIL_ADDRESS] (W.H.J.; [EMAIL_ADDRESS] (S.J.); [EMAIL_ADDRESS] (M.K.); [EMAIL_ADDRESS] (H.H.K.)  
*Correspondence: [EMAIL_ADDRESS]; Tel.: +82-31-290-7821  
[PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], H.  
and/or directly from the LV wall and are tied to the basal regions of the posterior leaflets; the (2) marginal (or primary) chordae are attached to the margin of the leaflets, and the space between the two marginal chordae is known to not exceed 3 mm with an attachment to the leaflet that is often bifurcated or trifurcated; and the (3) intermediary (or secondary) chordae extend from the papillary muscles and are attached to the LV side of the leaflets. The present study focuses on the intermediary chordae, which are also known as the strut chordae (SC).  
In the anterior leaflets, the two thick and resistant SC are located originating in the medial aspect of the ventricular side of the leaflet and provide resistance to the leaflet at closing during systole to thus avoid a prolapse [4; 5; 6]. As the LV pressure increases, the tension along the SC raises rapidly, and the maximum SC tension value becomes three times larger than the surrounding chordae in the anterior leaflet [3; 7; 8]. Although the SC do not show much direct impact on leaflet coaptation, they play a vital role in creating a tunnel-shaped morphology of the MV throughout the cardiac cycle and maintaining MV function [5; 9; 10; 11]. The large leaflet stress distribution over the anterior leaflet spreads from the fibrous trigone across the anterior central region towards the zone where the SC are connected [2; 6; 12]. All of these studies have emphasized the SC are critical to maintaining the long-term function of the MV.  
Recent excellent studies have revealed diverse advancement in computational MV modeling, more specifically in terms of modeling of the chordae tendineae [13; 14; 15; 16]. Moreover, solid mechanical evaluation of the chordae tissue and improved mathematical modeling of the chordae tendineae [17; 18; 19; 20; 21] as well as experimental and computational blood flow studies with respect to the chordae structure [22; 23; 24] have revealed the importance of chordae tendineae studies. However, there is still a lack of biomechanical information of the role of the SC; therefore, it is important to investigate the biomechanical effects of the insertion location of the SC in computational MV evaluations.  
We employed our previously developed and validated computational MV modeling and evaluation protocols [25; 26; 27; 28; 29; 30; 31] to investigate the effect of varying the SC insertion location on normal MV function and dynamics to better understand the complex MV structures. Computational evaluations were conducted to assess the physiologic and biomechanical features of nine types of MVs with various insertion locations of the SC. Detailed information of the leaflet coaptation, stress distribution, coaptation length, coaptation angle, bulging height, and bulging distance with respect to the SC insertion location were investigated.