Biomechanical behavior of pericardial human tissue: a constitutive formulation

Hemodynamic evaluation of biomaterial-based surgery for Tetralogy of Fallot using a biorobotic heart, in silico, and ovine models

Tetralogy of Fallot is a congenital heart disease affecting newborns and involves stenosis of the right ventricular outflow tract (RVOT). Surgical correction often widens the RVOT with a transannular enlargement patch, but this causes issues including pulmonary valve insufficiency and progressive right ventricle failure. A monocusp valve can prevent pulmonary regurgitation; however, valve failure resulting from factors including leaflet design, morphology, and immune response can occur, ultimately resulting in pulmonary insufficiency. A multimodal platform to quantitatively evaluate the effect of shape, size, and material on clinical outcomes could optimize monocusp design. This study introduces a benchtop soft biorobotic heart model, a computational fluid model of the RVOT, and a monocusp valve made from an entirely biological cell-assembled extracellular matrix (CAM) to tackle the multifaceted issue of monocusp failure. The hydrodynamic and mechanical performance of RVOT repair strategies was assessed in biorobotic and computational platforms. The monocusp valve design was validated in vivo in ovine models through echocardiography, cardiac magnetic resonance, and catheterization. These models supported assessment of surgical feasibility, handling, suturability, and hemodynamic and mechanical monocusp capabilities. The CAM-based monocusp offered a competent pulmonary valve with regurgitation of 4.6 ± 0.9% and a transvalvular pressure gradient of 4.3 ± 1.4 millimeters of mercury after 7 days of implantation in sheep. The biorobotic heart model, in silico analysis, and in vivo RVOT modeling allowed iteration in monocusp design not now feasible in a clinical environment and will support future surgical testing of biomaterials for complex congenital heart malformations.

Influence of inflammation and cardiac hypertrophy on mechanical properties of human pericardium

Different devices for mechanical circulatory support (MCS) have been developed for the treatment of refractory cardiogenic shock. However, all of them are associated with direct blood contact, the need for anticoagulation and bleeding complications. To overcome these limitations the pericardial sac got into the focus as a promising implantation site for MCS. For this purpose, further knowledge about the mechanical properties of human pericardium is required. In this prospective, monocentric, experimental pilot study 56 samples of human pericardium were extracted postmortem from 13 critically ill patients. After preparation of test specimens uniaxial tensile tests were performed. The primary end points were load at fracture per sample width and strain at fracture. Acute inflammation was assessed by blood levels of C-reactive protein, white blood count and procalcitonin measured at several times during hospital stay. Inflammatory load was estimated by area under the inflammatory curves. Correlation and regression analysis were used to assess the relationship of primary end points to inflammation, comorbidities and postmortem time to preparation. Human pericardium showed a load at fracture per sample width of 1.95 [1.38–2.94] N/mm (median [inter quartile range]) and a strain at fracture of 89.29 [73.84–135.23] %. Markers of acute inflammation and cardiac hypertrophy did not correlate to load or strain at fracture. However, strain at fracture increased with higher body mass index and an increasing number of postmortem days. In contrast, higher patient age was associated with a lower strain at fracture. Inflammation and cardiac hypertrophy did not influence mechanical properties of human pericardium.

Assessment of untreated fresh autologous pericardium as material for construction of heart valve: Result at 5 years

Introduction

Tetralogy of Fallot requiring transannular repair of the right ventricular outflow tract (RVOT) are exposed to free pulmonary insufficiency and hence inevitable right ventricular dysfunction. This study analyzes the function and structure of untreated autologous pericardium monocusp used to create a competent pulmonary valve.

Materials and Methods

This is a retrospective analysis of 52 cases operated between December 2006 and December 2012. Untreated autologous pericardium was used for creating a competent pulmonary valve following a transannular patch. They are followed for functional and structural assessment of the pulmonary valve by echocardiography. Positron emission tomography (PET) with 18 fluorodeoxyglucose was performed in two cases for profiling the pulmonary valve.

Results

Median age was 10.5 years (1-38). The follow-up was complete for 42 (80.76%) patients for 3 years and 25 (48.07%) patients for 5 years. The RVOT gradient was 42 mmHg (16-96) in the year of surgery, which reduced to 26 mmHg (10-58) and pulmonary insufficiency that was present in 8.3% of patients in 1st year was witnessed in 22.7% in the 5th year of follow-up. The monocusp patch was successful in creating a competent valve while maintaining its structure at 3 years; however, it became distorted and retracted at 5 years of follow-up. There was no calcification in any of the patients. PET-computed tomography confirmed the uptake of glucose by monocusp at 1 year of follow-up.

Conclusion

The untreated autologous pericardium functioned well when it was used to create a competent pulmonary valve at short term and midterm. Although it changed in its structure; there was no calcification at 5 years of follow-up.