Mitral chordae tendineae force profile characterization using a posterior ventricular anchoring neochordal repair model for mitral regurgitation in a three-dimensional-printed ex vivo left heart simulator

Abstract

OBJECTIVES Posterior ventricular anchoring neochordal (PVAN) repair is a non-resectional technique for correcting mitral regurgitation (MR) due to posterior leaflet prolapse, utilizing a single suture anchored in the myocardium behind the leaflet. This technique has demonstrated clinical efficacy, although a theoretical limitation is stability of the anchoring suture. We hypothesize that the PVAN suture positions the leaflet for coaptation, after which forces are distributed evenly with low repair suture forces. METHODS Porcine mitral valves were mounted in a 3-dimensional-printed heart simulator and chordal forces, haemodynamics and echocardiography were collected at baseline, after inducing MR by severing chordae, and after PVAN repair. Repair suture forces were measured with a force-sensing post positioned to mimic in vivo suture placement. Forces required to pull the myocardial suture free were also determined. RESULTS Relative primary and secondary chordae forces on both leaflets were elevated during prolapse (P < 0.05). PVAN repair eliminated MR in all valves and normalized chordae forces to baseline levels on anterior primary (0.37 ± 0.23 to 0.22 ± 0.09 N, P < 0.05), posterior primary (0.62 ± 0.37 to 0.14 ± 0.05 N, P = 0.001), anterior secondary (1.48 ± 0.52 to 0.85 ± 0.43 N, P < 0.001) and posterior secondary chordae (1.42 ± 0.69 to 0.59 ± 0.17 N, P = 0.005). Repair suture forces were minimal, even compared to normal primary chordae forces (0.08 ± 0.04 vs 0.19 ± 0.08 N, P = 0.002), and were 90 times smaller than maximum forces tolerated by the myocardium (0.08 ± 0.04 vs 6.9 ± 1.3 N, P < 0.001). DISCUSSION PVAN repair eliminates MR by positioning the posterior leaflet for coaptation, distributing forces throughout the valve. Given extremely low measured forces, the strength of the repair suture and the myocardium is not a limitation.

Heart Valve Biomechanics: The Frontiers of Modeling Modalities and the Expansive Capabilities of Ex Vivo Heart Simulation

“…Novel research is expanding the capabilities and applications of ex vivo modeling, focusing on generating immediately, clinically translatable insights for valvular treatment and surgical care. In a series of recent studies, researchers evaluated the biomechanical effects of apical and papillary neochord anchoring locations for MR repair, exploring the mechanical outcomes of novel percutaneous neochordoplasty technologies ( 82 , 83 ). These studies were enabled by the development of optical fiber-based force-sensing neochordae, which provide minimally invasive, highly sensitive chordal strain measurements ( 84 ).…”

Biomimetic six-axis robots replicate human cardiac papillary muscle motion: pioneering the next generation of biomechanical heart simulator technology

“…In this study, mitral valves were carefully excised from locally obtained fresh porcine hearts, preserving the annulus, leaflets, papillary muscles and chordae tendineae; in select circumstances, a valve could not be tested on the day of explanation and was placed in vacuum-sealed bag with normal saline and frozen for preservation. To mount the valve within our custom left heart simulator [6,7,10], a small cuff of left atrium was also preserved as the attachment for a 3D-printed, elastomeric, silicone sewing ring fixed between the left atrial and left ventricular simulator chambers. The sewing ring material provided elasticity to reduce annulus fixation and the left atrial cuff aided in retaining the natural elasticity of the valve.…”

“…Forces on the chordae tendineae were measured with calibrated fibre Bragg grating (FBG) strain gauge sensors (DTG-LBL-1550 125 µm FBGS International, Belgium) as previously described [7,10,29]. FBGs are optical strain gauges with a thin profile and low mass, enabling the use of the sensors on multiple chordae without disrupting the haemodynamics and mechanics of the valve apparatus.…”

“…Numerous previous studies feature analyses of disease states and optimization of surgical valve repair techniques and devices [1][2][3][4][5][6][7][8]. These studies are unique in their ability to immediately inform the current practice of cardiac surgery and have already had a meaningful impact on patient care through the analysis of surgical repairs [9,10]. However, the fidelity of these biomechanics analyses and surgical optimizations is dependent on the ability of the simulator to accurately mimic the in vivo environment, particularly for patient-specific surgical optimization.…”

Commentary: Mitral valve repair using adjustable posterior leaflet neochords

“… 4 Several studies documented that posterior leaflet resection results in decreased posterior leaflet mobility, coaptation length, and increased posterior leaflet stress when compared with the nonresectional neochord technique. 5 , 6 , 7 In a recently published meta-analysis, implantation of neochords improved left-sided long-term ventricular function, 8 but this did not reach statistical significance in a randomized controlled trial. 9 On the other side, implantation of neochords is quite challenging, even for skilled surgeons.…”