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

Abstract

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.

Comprehensive Ex Vivo Comparison of 5 Clinically Used Conduit Configurations for Valve-Sparing Aortic Root Replacement Using a 3-Dimensional–Printed Heart Simulator

“…To perform an in-depth study of the biomechanical parameters—including hemodynamics, graft compliance, and leaflet kinematics, among other factors—of the aortic valve within the various conduits, we used our ex vivo left heart simulator, which has been comprehensively described previously (Figure 4 A and 4 B). 18 , 29 – 33 Briefly, the system is comprised of a modular 3-dimensional–printed (Carbon M2, Carbon 3D Inc., Redwood City, CA) and machined enclosure mounted to a pulsatile linear actuator (Superpump, Vivitro Labs, Vancouver, Canada). The enclosure consists of a main ventricular chamber attached to the piston with a left atrial chamber with venous reservoir, and an aortic outflow assembly that connects in a complete circuit through a series of compliance chambers, flow meters, a heat exchanger, and a peripheral resistance valve.…”

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

“…We designed a customized left heart chamber and prototyped the device using 3D printing (Carbon M2, Carbon3D Inc., Redwood City, CA, USA) and milling, which we have previously described (Fig. 2 A) [ 19 , 20 ]. Briefly, the chamber was mounted to a pulsatile linear actuator (ViVitro Superpump, ViVitro Labs, Victoria, BC, Canada) and outfitted with left atrial, ventricular and aortic pressure transducers (Utah Medical Products Inc., Midvale, UT, USA), as well as electromagnetic flow probes (Carolina Medical Electronics Inc., East Bend, NC, USA) in the mitral and aortic positions.…”

“…We developed customized chordae tendineae force sensors with high accuracy and a small footprint using Fibre Bragg Grating (FBG) sensors, which we have described previously [ 20 ]. Briefly, FBGs are optical fibres with a series of spatial period gratings that reflect a particular wavelength of light transmitted by an optical interrogator.…”

Fiber Bragg Gratings for Medical Applications and Future Challenges: A Review

“…Not only the biomechanics of soft tissues from the lower limbs but also from other body districts have been studied in the literature. Recently, an FBG encapsulated in a protective sheath was used for measuring chordae tendineae tension in the cardiac mitral valve [30]. The sensor shape and movement mimicked the ones of the native biological tissue.…”