Ex Vivo Biomechanical Study of Apical Versus Papillary Neochord Anchoring for Mitral Regurgitation

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.

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Section: Methodsmentioning

confidence: 99%

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

Paulsen

Imbrie-Moore

Wang

et al. 2019

European Journal of Cardio-Thoracic Surgery

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“…Diagram of the left heart simulator (a) with each component labeled. Mitral valve tacked onto silicone sewing ring[43] (Reprinted with permission from Elsevier copyright 2019) ((b) and (c)) with interrupted sutures to obtain proper alignment. Final prototype of FSN implanted onto a mitral valve chordae tendineae (d) with the green arrow denoting the FSN, white arrows denoting the PTFE sutures attaching the chordae to the FSN proximally and distally to the sensor, and the orange arrow denoting the instrumented chordae.…”

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confidence: 99%

Development and Ex Vivo Validation of Novel Force-Sensing Neochordae for Measuring Chordae Tendineae Tension in the Mitral Valve Apparatus Using Optical Fibers With Embedded Bragg Gratings

Paulsen

Bae

Imbrie-Moore

et al. 2019

Journal of Biomechanical Engineering

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Few technologies exist that can provide quantitative data on forces within the mitral valve apparatus. Marker-based strain measurements can be performed, but chordal geometry and restricted optical access are limitations. Foil-based strain sensors have been described and work well, but the sensor footprint limits the number of chordae that can be measured. We instead utilized fiber Bragg grating (FBG) sensors—optical strain gauges made of 125 μm diameter silica fibers—to overcome some limitations of previous methods of measuring chordae tendineae forces. Using FBG sensors, we created a force-sensing neochord (FSN) that mimics the natural shape and movement of native chordae. FBG sensors reflect a specific wavelength of light depending on the spatial period of gratings. When force is applied, the gratings move relative to one another, shifting the wavelength of reflected light. This shift is directly proportional to force applied. The FBG sensors were housed in a protective sheath fashioned from a 0.025 in. flat coil, and attached to the chordae using polytetrafluoroethylene suture. The function of the force-sensing neochordae was validated in a three-dimensional (3D)-printed left heart simulator, which demonstrated that FBG sensors provide highly sensitive force measurements of mitral valve chordae at a temporal resolution of 1000 Hz. As ventricular pressures increased, such as in hypertension, chordae forces also increased. Overall, FBG sensors are a viable, durable, and high-fidelity sensing technology that can be effectively used to measure mitral valve chordae forces and overcome some limitations of other such technologies.

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“…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.…”

Section: Left Heart Simulatormentioning

confidence: 99%

“…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.…”

Section: Left Heart Simulatormentioning

confidence: 99%

“…The simulators feature programmable pumps that expose heart valves to their physiologic environment-including relevant pressure and flow waveforms-while haemodynamic, strain and motion metrics are recorded. 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].…”

Section: Introductionmentioning

confidence: 99%

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

Imbrie-Moore

Park

Paulsen

et al. 2020

J. R. Soc. Interface.

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Papillary muscles serve as attachment points for chordae tendineae which anchor and position mitral valve leaflets for proper coaptation. As the ventricle contracts, the papillary muscles translate and rotate, impacting chordae and leaflet kinematics; this motion can be significantly affected in a diseased heart. In ex vivo heart simulation, an explanted valve is subjected to physiologic conditions and can be adapted to mimic a disease state, thus providing a valuable tool to quantitatively analyse biomechanics and optimize surgical valve repair. However, without the inclusion of papillary muscle motion, current simulators are limited in their ability to accurately replicate cardiac biomechanics. We developed and implemented image-guided papillary muscle (IPM) robots to mimic the precise motion of papillary muscles. The IPM robotic system was designed with six degrees of freedom to fully capture the native motion. Mathematical analysis was used to avoid singularity conditions, and a supercomputing cluster enabled the calculation of the system's reachable workspace. The IPM robots were implemented in our heart simulator with motion prescribed by high-resolution human computed tomography images, revealing that papillary muscle motion significantly impacts the chordae force profile. Our IPM robotic system represents a significant advancement for ex vivo simulation, enabling more reliable cardiac simulations and repair optimizations.

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Ex Vivo Biomechanical Study of Apical Versus Papillary Neochord Anchoring for Mitral Regurgitation

Cited by 38 publications

References 26 publications

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

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

Development and Ex Vivo Validation of Novel Force-Sensing Neochordae for Measuring Chordae Tendineae Tension in the Mitral Valve Apparatus Using Optical Fibers With Embedded Bragg Gratings

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

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