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Page 8 of 10 Prescott et al. Vessel Plus 2019;3:13 I http://dx.doi.org/10.20517/2574-1209.2018.70

chordae. Again, the peak stress has been reduced by the introduction of the MitraClip to a value of 85 kPa
during diastole.

DISCUSSION
Previous clinical trials have reported the successful use of the MitraClip system as a solution for severe MR
in the context of HOCM. A study of six patients suffering from the disease concluded that percutaneous
mitral repair using the MitraClip is feasible and may be performed safely in HOCM, and this technique can
[21]
be effective in reducing MR and improving symptoms . This is supported by clinical trial which reported
that patients experienced a reduction in MR and a reduction in the left ventricular outflow tract (LVOT)
[22]
gradient from a mean of 75.8 ± 39.7 to 11.0 ± 5.6 mmHg . Nearly all patients demonstrated improvements
[22]
in symptoms by either new NYHA class designations or improved exercise tolerance .
The results of our FE simulations provided further evidence to support that MitraClip implantation is a
viable approach for solving MR in the case of posterior leaflet prolapse due to HOCM leaflet extensibility
and chordae rupture. The introduction of the clip has prevented the leaflet from prolapsing and aided in
almost complete closure of the valve during peak systole. The general order of magnitude of stress across the
leaflets has not been affected significantly by the clip during systole and diastole. In fact, in the previously
prolapsed region where the chordae are present, the MitraClip has alleviated stress significantly.

There have been a number of previous studies into FE modelling of the MV apparatus with a focus on
topics such as nonlinear tissue response, annulus dilation and relative papillary muscle motion. However,
the literature is limited regarding simulations of the MitraClip system in an FE environment, and also
addressing the diastolic stage. The novelty of the current study lies with the concise side-by-side comparison
of the same diseased valve, operating under the same loading conditions, with and without the MitraClip,
respectively. The performance of the valve has been assessed under both peak systolic and peak diastolic
conditions, and a quantifiable improvement in MV function has been established after introduction of the
clip. Therefore, the results should aid in a better understanding of the implications that the MitraClip system
has on both the stress distribution and deformation of the MV leaflets. This information may aid in further
development of the MitraClip and should encourage further research into advanced, minimally invasive
treatments for severe MR in high risk patients.

Further work is also needed to refine the FE method employed in the current study to more accurately
capture the impact of HOCM and produce more comprehensive results in the future. Notably, the effects of
annulus dilation and relative papillary motion will have to be accounted for to produce a less conservative
model. Furthermore, a deeper analysis into simulating systolic anterior motion would be beneficial due to
[23]
the risk of LVOT obstruction and MR, which is associated with a 20% risk of sudden death . That being
said, the current study has provided a solid ground to extend to these related areas. In addition, a fluid-
structure interaction (FSI) model would be more helpful for analysing MitraClip behaviour during diastolic
stage. Some previous computational studies have employed FSI approach in modelling and understanding
the function of mitral valve [24,25] , but not in the context of MitraClip repair. To run an appropriate FSI
analysis for mitral valve repaired with MitraClip, it will require tremendous additional efforts and times,
and seems beyond the scope of current study. Nevertheless, the research group are currently undertaking
such analyses and the results will be reported in future.

DECLARATIONS
Authors’ contributions
Contributed to the research and the preparation of the manuscript: Prescott B, Abunassar CJ, Baxevanakis
KP, Zhao L
Carried out the work, processed the results and drafted the manuscript: Prescott B