Asymmetric and eccentric expansion of metallic everolimus-eluting stents (EES) or bioresorbable vascular scaffolds (BVS) can be linked to adverse events, according to a substudy of ABSORB II. The combination of death, myocardial infarction, and ischemia-driven target lesion revascularization were more likely with device asymmetry (6.9% versus 1.8% for symmetric implants, P=0.007) and eccentricity (8.2% versus 3.5%, P=0.04) seen on post-procedure intravascular ultrasound (IVUS). After multivariable adjustment, asymmetric implants remained a predictor of device-related events (hazard ratio 3.43, 95% CI 1.08-10.92), Patrick W. Serruys, MD, PhD, of the Imperial College London, and colleagues reported online in JACC: Cardiovascular Interventions. “Post-procedural devices asymmetry were independently associated with [the] device-oriented composite endpoint following percutaneous coronary intervention. However, this approach should be viewed as hypothesis generating due to low event rates,” the investigators wrote. Serruys’s group noted that in current practice “minimal stent area and expansion index have been widely used as indicators of optimal scaffold/stent expansion whereas there [has been] less attention dedicated to post-implantation device asymmetry and eccentricity.” In an accompanying editorial, Myeong-Ki Hong, MD, PhD, and Jung-Sun Kim, MD, both of Severance Cardiovascular Hospital in Korea, posed the question: “How can we achieve optimal and symmetric stent expansion?” “The adequate and symmetric expansion of BVS is usually affected by underlying plaque characteristics and burden,” they wrote. “Imaging guidance such as IVUS or optical coherence tomography can provide more accurate information regarding vessel size and plaque characteristics for obtaining adequate modifications of plaque for optimal stent expansion.” “Although the current study hints that there might be unfavorable effects of asymmetric EES expansion, the number of EES-treated patients enrolled in this study was too small to draw clear conclusions,” the editorialists noted. The 470 patients in the ABSORB II substudy had IVUS before and after device implantation (308 assigned to BVS and 162 given EES). EES recipients had their stents placed more symmetrically (P<0.001) and concentrically (P<0.001) than the BVS group, though the lesions treated were themselves more eccentric and asymmetric in the BVS cohort (P<0.001 for both). Only 8.0% of the BVS cohort achieved optimal device expansion, compared with 20.0% of the EES arm (P<0.001). There was no difference between groups in device-related events (5.2% versus 3.1%, P=0.29) at 1 year, however. Disclosures The ABSORB II trial was sponsored by Abbott Vascular. Serruys declared serving on the international advisory board of Abbott Vascular. Hong and Kim disclosed no relevant conflicts of interest.