A patient-specific computational analysis from imaging for annuloplasty ring assessment for the treatment of ischemic mitral regurgitation

Purpose: Ischemic mitral regurgitation (IMR) is usually treated through restrictive annuloplasty via rigid rings, which constrain the annular shape, or flexible rings, which preserve annular dynamics. The choice between these two options is still debated and several methodologies have been adopted to identify the best solution. Among those, finite element (FE) models have provided useful insight,but past models suffered of simplifications that could have limited and biased the conclusions. We aimed at analyzing the effects of ring's flexibility in restrictive annuloplasty through mitral valve (MV) patient-specific realistic FE models based on cardiac magnetic resonance (CMR) imaging, thus overcoming previous limitations. Methods: CMR imaging of 18 evenly rotated long-axis planes (one every 10°) along the left ventricular long-axis was performed in 7 ischemic patients (55 timeframes/cardiac cycle). In each plane and for each systolic frame, MV annulus, leaflets, and papillary muscles were manually identified using custom software. These structures were then automatically reconstructed in the 3-D space, and used as input to the MV FE models. MV tissue response was modeled as nonlinear elastic and anisotropic. A physiological transvalvular pressure load was applied to the leaflets to simulate valve closure up to peak systole. For each patient, three conditions were simulated: (i) pre-operative, (ii) after insertion of a ring with closed profile and regionally varying bending stiffness (CV ring), and (iii) after implanting a rigid ring with partially open profile at saddle-horn (RO ring). Results: The RO ring restored MV competence in 7/7patients resulting in higher coaptation length, while CV ring succeeded only in 5/7. Conversely, annular dynamics was lost with the RO ring, while CV ring partially preserved it. Both rings significantly reduced leaflets stresses and tensions on chordae tendineae and papillary muscles. Conclusions: While RO rings seem resulting in a good performance,flexible CV rings could not always guarantee to counterbalance the effect of leaflets tethering associated to IMR. Moreover, despite their flexibility,annular dynamics was not completely preserved. Our patient-specific FE approach could provide new insight in optimizing tuning of local stiffness, thus potentially improving the performance of new ring design, as well as help in surgery planning.