Mechanical analysis of ovine and pediatric pulmonary artery for heart valve stent design

Abstract

Transcatheter heart valve replacement is an attractive and promising technique for congenital as well as acquired heart valve disease. In this procedure, the replacement valve is mounted in a stent that is expanded at the aimed valve position and fixated by clamping. However, for this technique to be appropriate for pediatric patients, the material properties of the host tissue need to be determined to design stents that can be optimized for this particular application. In this study we performed equibiaxial tensile tests on four adult ovine pulmonary artery walls and compared the outcomes with one pediatric pulmonary artery. Results show that the pediatric pulmonary artery was significantly thinner (1.06 ± 0.36 mm (mean ± SD)) than ovine tissue (2.85 ± 0.40 mm), considerably stiffer for strain values that exceed the physiological conditions (beyond 50% strain in the circumferential and 60% in the longitudinal direction), more anisotropic (with a significant difference in stiffness between the longitudinal and circumferential directions beyond 60% strain) and presented stronger non-linear stress-strain behavior at equivalent strains (beyond 26% strain) compared to ovine tissue. These discrepancies suggest that stents validated and optimized using the ovine pre-clinical model might not perform satisfactorily in pediatric patients. The material parameters derived from this study may be used to develop stent designs for both applications using computational models.

Back to the root: a large animal model of the Ross procedure

“…Previous studies have described ovine aortic valve cusps to be thinner and more compliant than those of pigs and elderly humans (36,37). Similarly, the ovine pulmonary arterial wall may be less stiff than in humans (38). While this may simply be related to differences in hemodynamic demands, it might impact the extrapolation of data from an ovine model to the clinical situation.…”

In Vitro Degradation Behaviours of PDO Monofilament and Its Intravascular Stents with Braided Structure

“…Flexibility is a complex of stiffness and pliability. The stiffness made the delivery process easy to handle, while the pliability enabled the deployed stent to follow vessel contour to diseased region and reduce injury to lumen wall [20]. The generally employed testing method was cantilever beam [21], three-point bending [22] and four-point bending [23].…”

Population-specific material properties of the implantation site for transcatheter aortic valve replacement finite element simulations

“…Indeed, whilst cardiovascular imaging enables accurate representation of the 3D anatomy, current techniques do not allow acquisition of the patient-specific in vivo mechanical characteristics. Response to device deployment depends not only on the material properties of the implantation site itself, but also on the presence of surrounding structures ( Kim et al, 2013 ), thus limiting in some contexts the value of ex-vivo data from arterial tissue ( Avril et al, 2010 , Badel et al, 2011 , Cabrera et al, 2013 , Flamini et al, 2015 , García-Herrera et al, 2013 , Li et al, 2008 , Ning et al, 2010 , O’Dea and Nolan, 2012 , Veljković et al, 2014 ). In addition, non-invasive, inverse computational methods, based on simultaneous acquisition of pressure gradients and diameters, ( De Heer et al, 2012 , Hamdan et al, 2012 , Karatolios et al, 2013 , Masson et al, 2008 , Schlicht et al, 2013 , Schulze-Bauer and Holzapfel, 2003 , Smoljkić et al, 2015 , Wittek et al, 2013 , Zeinali-Davarani et al, 2011 ), are limited to describe the patient-specific behaviour during the cardiac cycle, but not at overload due to device expansion ( Bosi et al, 2015 , Bosi et al, 2016a , Bosi et al, 2016b ).…”