China 
Africa 
Explore chapters and articles related to this topic
Biological Properties of Suture Materials
Published in Chih-Chang Chu, J. Anthony von Fraunhofer, Howard P. Greisler, Wound Closure Biomaterials and Devices, 2018
M. K. Hirko, P. H. Lin, H. P. Greisler, C. C. Chu
Recently, Revuelta et al.106 and David et al.107 used Gore-Tex sutures for the surgical repair of raptured or elongated chordae tendineae of the anterior leaflet of the mitral valves by replacing the chordae tendineae with the Gore-Tex sutures. After 3 months of implantation in sheep, the chordae made of Gore-Tex suture was completely surrounded by a sheath with either no adverse tissue reaction or a mild inflammatory cell reaction of the mononuclear type at the sheath-suture interface.106 There was no sign of microscopic calcification at the Gore-Tex chordae. The sheath had three layers: an inner dense concentrical core of collagenous tissue with bundles arranged parallel to the longitudinal direction of the Gore-Tex suture, a loose spongiosa as the middle layer, and endothelium on the surface of the regenerated chorda without platelet accumulation or thrombus formation. Revuelta et al. thus suggested that owing to the good biocompatibility and tissue regeneration capability, Gore-Tex suture could be a viable alternative as a stent for the formation of chordae tendineae with a structure similar to the native one. When experimenting in human beings, David et al. reported that the replacement of diseased chordae tendineae of 43 patients with Gore-Tex sutures is a simple means to reconstructing mitral valves in patients who would otherwise require a more tedious, complicated, and costly surgical replacement of mitral valves by prosthetic valves.107 Histologic evaluation of a 9-month-old Gore-Tex chordae retrieved from a patient showed that the interstices of Gore-Tex suture had plasma proteins. Contrary to the histologic findings in animals, the portion of the Gore-Tex chordae in human beings that was not in contact with the leaflets and papillary muscles was not covered by any cellular components. No thrombi were found on the surface of Gore-Tex suture chordae.
Mitral Valve Mechanics
Published in Michel R. Labrosse, Cardiovascular Mechanics, 2018
A. Tran, T. G. Mesana, V. Chan
Chordae tendinae are fibrous strands originating at the papillary muscle or ventricular wall and inserting into the valve apparatus. They consist of an inner layer of tightly bound collagen intertwined with elastin fiber and aligned in the direction of tension. An outer looser layer of collagen and elastic fibers surrounds the core [18,19]. Using porcine hearts, Ritchey et al. described longitudinal vessels running from papillary muscle, through the chordae, into the mitral valve. Strut chordae were found to have the highest number of vessels [19]. There have been several proposed classification systems for chordal structures [12,18,19]. More modern definitions have separated chords based on insertion point and function. Lam et al. examined the morphology of 50 normal mitral valves and described three types of chordae [12]. Their classification included chordae inserting into the rough zone, leaflets (including clefts), and commissures. The anterior and posterior mitral leaflets have different configurations of chordal attachment. The chordae of the anterior leaflet insert into the apex, at the thicker free edge of leaflets termed the rough zone. In addition, there are typically two thicker chordae that insert into the ventricular surface of the valve at the posteromedial and anterolateral regions of the anterior leaflet, away from the free margin; these are known as strut chordae and have been measured to be on average 1.86 ± 0.43 cm in length and 1.24 ± 0.51 cm in thickness. For comparison, rough zone chordae were 1.75 ± 0.25 cm and 0.84 ± 0.28 cm in length and thickness, respectively [12]. The posterior leaflet possesses more defined scallops than the anterior leaflet. In addition to rough zone chordae, there are also basal chordae, which may originate from the wall of the ventricle or trabeculae carneae and insert into the annulus. Two cleft chordae, with insertions into the free margin of the cleft on the leaflet, are also present. Together, they aid in defining the three scallops of the posterior leaflet [12]. Lam et al. also described chordae fanning out at the commissure in the anterolateral and posteromedial regions, with some chords extending as far as the base of the scallop. Average length and diameter of chordae, measured by Lam et al., were found to be lower in the posterior leaflet chordae than in the anterior leaflet chordae.
Tailoring superelastic and transformation-induced plastic response of shape memory multilayers with wavy architectures
Published in Mechanics of Advanced Materials and Structures, 2023
Multilayers with wavy architectures are found wide-ranging applications in various engineering practices as they can improve certain performance characteristics, such as toughness and thermal stability, or exist naturally in biological tissues to meet certain targeted performances [44–46]. A case in point is the chordae tendinae which are tendons composed of collagen fibers arranged in planar crimped patterns which control the opening and closing of a heart valve. The waviness and layer thickness have been shown to significantly affect the homogenized and localized elastoplastic response of multilayered wavy architectures, as discussed by Khatam and Pindera [47]. To the authors’ best knowledge, there is no reported work that describes the shape memory response and the underpinning mechanisms during the deformation of multilayered wavy architectures. Thus, the current work is motivated to contribute to this subject, which is important in SMA composite design and applications.