Computational and experimental mechanical performance of a new everolimus-eluting stent purpose-built for left main interventions

Abstract

Left main (LM) coronary artery bifurcation stenting is a challenging topic due to the distinct anatomy and wall structure of LM. In this work, we investigated computationally and experimentally the mechanical performance of a novel everolimus-eluting stent (SYNERGY MEGATRON) purpose-built for interventions to large proximal coronary segments, including LM. MEGATRON stent has been purposefully designed to sustain its structural integrity at higher expansion diameters and to provide optimal lumen coverage. Four patient-specific LM geometries were 3D reconstructed and stented computationally with finite element analysis in a well-validated computational stent simulation platform under different homogeneous and heterogeneous plaque conditions. Four different everolimus-eluting stent designs (9-peak prototype MEGATRON, 10-peak prototype MEGATRON, 12-peak MEGATRON, and SYNERGY) were deployed computationally in all bifurcation geometries at three different diameters (i.e., 3.5, 4.5, and 5.0 mm). The stent designs were also expanded experimentally from 3.5 to 5.0 mm (blind analysis). Stent morphometric and biomechanical indices were calculated in the computational and experimental studies. In the computational studies the 12-peak MEGATRON exhibited significantly greater expansion, better scaffolding, smaller vessel prolapse, and greater radial strength (expressed as normalized hoop force) than the 9-peak MEGATRON, 10-peak MEGATRON, or SYNERGY (p < 0.05). Larger stent expansion diameters had significantly better radial strength and worse scaffolding than smaller stent diameters (p < 0.001). Computational stenting showed comparable scaffolding and radial strength with experimental stenting. 12-peak MEGATRON exhibited better mechanical performance than the 9-peak MEGATRON, 10-peak MEGATRON, or SYNERGY. Patient-specific computational LM stenting simulations can accurately reproduce experimental stent testing, providing an attractive framework for cost- and time-effective stent research and development.

Patient-specific computational simulation of coronary artery bifurcation stenting

“…Computational mesh The 3D reconstructed bifurcation models were meshed with 0.25 mm hexahedral elements (ICEM CFD 17.2, ANSYS Inc., Canonsburg, PA, USA). Mesh convergence study using different element sizes (from 0.50 to 0.25 mm) showed minimal difference (< 1%) in stent expansion 18 . The stent design models were provided by the manufacturer (Medtronic Vascular) in their nominal dimensions.…”

“…Material properties In computational simulations, the wall thickness, lumen area, plaque eccentricity and plaque material were determined by OCT, as previously described 18 . A novel plaque scoring system was established based on the experimental data represented by the stress-strain graph of the constitutive equation with multiple coefficients (Online Figure 2 ) 18 , 19 . The area, circumference, and thickness of the lipid, fibrous, and calcified material were assessed in each OCT frame of MV and SB pullback by an imaging expert (YSC).…”

“…− 0.25, 0, + 0.25 etc.) ranging from + 2 (calcium only, very stiff) to − 2 (lipid only, very soft) 18 . The normal wall thickness and tapering were assessed by OCT.…”

“…Stent and balloon crimping, positioning, and bending All stents were first crimped from their nominal states using surface elements driven by radial displacement 18 . The crimped stents and balloons were positioned and bent along the centerline (Fig.…”

“…Computational simulations All steps of the PCI procedures were computationally replicated through a multi-step, large-deformation, quasi-static finite element analysis using the central difference method (Abaqus/Explicit solver; Table 3 ) 18 . In all analyses, the duration of balloon inflation and deflation was set to 0.05 s and the target time increments were set as 5 × 10 –8 s (adjusted via mass scaling) to obtain fast quasi-static results while avoiding dynamic effects.…”