Pediatric pulmonary valve replacements: Clinical challenges and emerging technologies

Figures

• 

  FIGURE 1. Pulmonary valve structure. (a) Unidirectional blood flow through the heart is facilitated by four heart valves (pulmonary, aortic, mitral, and tricuspid). The pulmonary valve mediates flow between the right ventricle and pulmonary artery. (b) A semilunar valve during systole (left) and diastole (right), marking the leaflet (L), annulus (A) and commissural area (C). Adapted from Schoen et al. 2018 32 ; (c) Cellular and extracellular composition of a heart valve leaflet. Adapted from del Monte‐Nieto et al. 33

• 

  FIGURE 2. Pulmonary valve function. (a) Pressure profiles in the right ventricle and pulmonary artery, and flow profile through the PV during the cardiac cycle. Adapted from Emmert et al. 2018. 39 (b) Flow simulation through a prosthetic aortic valve, noting the vortices formed in the sinuses. Adapted from Sotiropoulos et al. 2016. 40 (c) Visualization of the structure–function relationship between leaflet ECM and valve opening. Adapted from Schoen et al. 2018. 32 (d) Tensile properties of aortic (A) and pulmonary (P) valve leaflets in the circumferential (C) and radial (R) directions. Adapted from Stradins et al. 2004. 41 (e) Anisotropic flexural properties of porcine heart valve leaflets. Adapted from Gloeckner et al. 1999. 42

• 

  FIGURE 3. Introduction timeline of HVRs with application in the pediatric population. The first ball‐and‐cage mechanical valve was introduced in 1952, 55 with the first generation of bileaflet mechanical valves introduced in 1963. 56 The first homograft was implanted in 1962, 57 the first use of an autograft in the Ross procedure was reported in 1967. 58 The first chemically‐treated bioprosthesis was described in 1968 59 and the first transcatheter bioprosthesis was successfully deployed in 2000. 60

• 

  FIGURE 4. Consequences of biofouling. (a) The nonspecific adsorption of blood proteins occurs within seconds of biomaterial exposure, inducing various adverse biological events including (b) thrombosis, (c) immune responses and FBR, (d) calcification, and (e) infection. Scale and relative sizes between components are not realistic.