Type IV Pili of Streptococcus sanguinis Contribute to Pathogenesis in Experimental Infective Endocarditis

This work provides evidence that type IV pili produced by Streptococcus sanguinis SK36 are critical to the ability of these bacteria to attach to and colonize the aortic heart valve (endocarditis). We found that an S. sanguinis type IV pili mutant strain was defective in causing platelet-dependent aggregation in a 24-h infection assay but not in a 1-h platelet aggregation assay, suggesting that the type IV pili act at later stages of vegetation development.

The concept of automated functional design of heart valve prostheses

Aim. To develop an algorithm for the automated functional design of the heart valve leaflet apparatus.Methods. The geometry of the aortic valve leaflet was designed in the Matlab programming environment (MathWorks, Massachusetts, USA). Numerical modeling of the opening process was performed using Abaqus/CAE (Dassault Systemes, France).Results. We developed an algorithm, with the help of which a set of models of the leaflet apparatus was designed. 8 models were subjected to numerical modeling of the stress-strain state. The locking pressure simulation has shown that the smallest von Mises stress value was recorded for a sample with a larger surface area of the leaflet belly and it equals 0.422 MPa. The results obtained show that the value of the radius of curvature significantly affects the behavior of the entire valve, which leads to the conclusion that it is necessary to carefully select the design of the valve apparatus for its correct functioning.Conclusion. The study provides the primary confirmation that the concept of the algorithm is efficient for the automated functional design of the aortic heart valve leaflet apparatus.

Mechanical and Degradation Properties of Hybrid Scaffolds for Tissue Engineered Heart Valve (TEHV)

In addition to biocompatibility, an ideal scaffold for the regeneration of valvular tissue should also replicate the natural heart valve extracellular matrix (ECM) in terms of biomechanical properties and structural stability. In our previous paper, we demonstrated the development of collagen type I and hyaluronic acid (HA)-based scaffolds with interlaced microstructure. Such hybrid scaffolds were found to be compatible with cardiosphere-derived cells (CDCs) to potentially regenerate the diseased aortic heart valve. This paper focused on the quantification of the effect of crosslinking density on the mechanical properties under dry and wet conditions as well as degradation resistance. Elastic moduli increased with increasing crosslinking densities, in the dry and wet state, for parent networks, whereas those of interlaced scaffolds were higher than either network alone. Compressive and storage moduli ranged from 35 ± 5 to 95 ± 5 kPa and 16 ± 2 kPa to 113 ± 6 kPa, respectively, in the dry state. Storage moduli, in the dry state, matched and exceeded those of human aortic valve leaflets (HAVL). Similarly, degradation resistance increased with increasing the crosslinking densities for collagen-only and HA-only scaffolds. Interlaced scaffolds showed partial degradation in the presence of either collagenase or hyaluronidase as compared to when exposed to both enzymes together. These results agree with our previous findings that interlaced scaffolds were composed of independent collagen and HA networks without crosslinking between them. Thus, collagen/HA interlaced scaffolds have the potential to fill in the niche for designing an ideal tissue engineered heart valve (TEHV).

A Patient-Specific Model of Transcatheter Valve Replacement in a Bicuspid Heart Valve

Bicuspid Aortic Valves (BAVs) are a common congenital heart disease where two cusps of the aortic heart valve become fused together, this leads to two unequally sized leaflets compared to the normal trileaflet valve. Transcatheter Aortic Valves are currently used in off-label treatmet of stenosed BAVs, however, due to the abnormal valve anatomy, debate surrounds the sizing of transcatheter valves. In this study, finite element models were developed to simulate the deployment of two different valves sizes (a 25 mm and a 27 mm) of the Lotus valve into the patient-specific aortic root geometry of a clinical stenosed BAV case. These models were used to investigate and compare the eccentricity, stress and mal-apposition of the two valve sizes. The results demonstrated that the 25 mm valve was the most suitable in terms of eccentricity and stress reduction. It was also shown that the smaller 25 mm valve size did not increase the likelihood of mal-apposition. As the 25 mm valve was deemed suitable based on current sizing algorithms, on the basis of these results traditional annulus measurement and device sizing may be suitable in the case of the Lotus valve.