MRI-based multiscale models for the hemodynamic and structural evaluation of surgically reconstructed aortic arches.

The surgical reconstruction of the aortic arch is necessary in pediatric patients suffering from different types of congenital heart malformations, in particular, coarctation of the aorta. Among the reconstruction techniques used in surgical practice end-to-end anastomosis (E/E), Gore-tex graft interposition (GGI) and Gore-tex patch graft aortoplasty (GPGA) are compared in this study with a control model, employing a computational fluid-structure-interaction scheme. This study analyzes the impact of introducing synthetic materials on aortic hemodynamics and wall mechanics. Three-dimensional (3D) geometries of a porcine aortic arch were derived from magnetic resonance imaging (MRI) images. Inlet conditions were derived from MRI velocimetry. A multiscale approach was used for the imposition of outlet conditions, wherein a lumped parameter net provided an active afterload. Evidence was found that ring-like repairs increased blood velocity, whereas GPGA limited it. Vortex presence was greater and longer lasting in GGI. The highest power losses corresponded to GPGA. GGI had an intermediate effect, while E/E dissipated only slightly more than the control case. Wall stresses peak in a longitudinal strip on the subject's left side of the vessel, particularly in the frontal area. There was a concentration of stress at the suture lines. All surgical techniques performed equally well in restoring physiological pressures.

Aortic tissue properties in porcine models: A comparison of ex vivo mechanical test results after simulated aortic arch reconstructions.

Surgical interventions on the arterial wall can produce modifications to its tissue characteristics, and the addition of synthetic materials of different types can have implications on hemodynamics and blood vessel wall behavior. This work studies the midterm effects of end-to-end anastomosis (E/E), Gore-tex graft interposition (GGI) and Gore-tex patch graft aortoplasty (GPGA) in aortic arch reconstruction. The study comprised of two groups of healthy Danish sows. The sows in the first group (short term (ST)) weighed about 40 kg, underwent a surgical operation and were sacrificed on the same day. The sows in the second group (midterm (MT)) weighed 5-10 kg, underwent a surgical operation and were then allowed to grow to a weight of about 30-40 kg, before being sacrificed. One sow in each group was scheduled for E/E and one sow for GGI. One sow in ST and two sows in MT received GPGA. The overall average wall thickness was 1.93 mm. Relaxation constant values were significantly higher for ST (5.221 +/- 1.832 sec) than for MT (2.184 +/- 1.216 sec). GPGA showed a greater impact on relaxation than other procedures, enhancing the viscous character. The working-point Young's modulus (Epw ) was not significantly different in ST and MT. Circumferential samples had different Epw (0.419 +/- 0.77 MPa) from longitudinal samples (0.902 +/- 0.378 MPa). There also appeared to be a significant difference between samples cut longitudinally on the left and the right sides of the wall. The overall average Epw value was 0.6609 +/- 0.3641 MPa.