Absorb Bioresorbable Vascular Scaffold is Associated with Low Wall Shear Stress Compared to Xience V: A Biomechanical Analysis of the Absorb III Imaging Study.

AIMS: The Absorb bioresorbable vascular scaffold (BVS) has higher rates of target lesion failure (TLF) at 3 years. Low wall shear stress (WSS) promotes several mechanisms related to device TLF. We investigated the impact of BVS compared to Xience V (XV) on coronary WSS after device deployment. METHODS AND RESULTS: In the prospective, randomized, controlled ABSORB III Imaging study [BVS (n=77) or XV (n = 36)], computational fluid dynamics were performed on fused angiographic and intravascular ultrasound (IVUS) images of post-implanted vessels. Low WSS was defined as < 1 Pa. There were no differences in demographics, clinical risks, angiographic reference vessel diameter and IVUS minimal lumen diameter between the BVS and XV patients. A greater proportion of vessels treated with BVS compared to XV demonstrated low WSS across the whole device [BVS: 17/77 (22%) vs XV: 2/36 (6%), p<0.029]. Compared to XV, BVS demonstrated lower median circumferential WSS (1.73 vs 2.21 Pa; p=0.036), outer curvature WSS (p=0.026), and inner curvature WSS (p=0.038). Similarly, BVS had lower proximal 3rd WSS (p=0.024), middle 3rd WSS (p=0.047) and distal 3rd WSS (p=0.028) when compared to XV. In a univariable logistic regression analysis, patients who received BVS were 4.8 more likely to demonstrate low WSS across the scaffold/stent when compared to XV. Importantly, in a multivariable linear regression model, hypertension (Beta: 0.186, p =0.023), lower contrast frame count velocity (Beta: - 0.411, p<0.001), lower post stent residual plaque burden (Beta: -0.338, p<0.001), lower % underexpanded frames (Beta: -0.170, p=0.033) and BVS deployment (Beta: 0.251, p = 0.002) remained independently associated with greater percentage of stented coronary vessel areas exposed to low WSS. CONCLUSIONS: In this randomized controlled study, the Absorb BVS was 4.8 times more likely than the XV metallic stent to demonstrate low WSS. BVS implantation, lower blood velocity and lower residual post stent plaque burden were independently associated with greater area of low WSS.