Implantation with bioresorbable vascular scaffold (BVS) is more often associated with post-procedural asymmetric and eccentric morphology compared with metallic everolimus-eluting stent (EES), according to results from the ABSORB II trial.

Researchers compared BVS and metallic EES in the treatment of de novo coronary artery stenosis in 470 patients (n=308 with BVS; n=162 with metallic EES) to determine the impact of post-procedural scaffold/stent asymmetry, expansion, and eccentricity indices on early and late clinical events.

The primary outcome was a device-oriented composite end point (DoCE) at 1 year, which was defined as a composite of cardiac death, myocardial infarction (MI), and ischemia-driven target lesion revascularization (ID-TLR) via coronary bypass graft surgery or percutaneous coronary intervention (PCI).


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Patients were randomly assigned to either the BVS or metallic EES treatment arm. No significant differences in baseline characteristics were reported. However, there was a higher post-procedural diameter stenosis and lower acute gain among patients treated with BVS compared to the patients treated with metallic EES. The post-dilation balloon size and pressure among BVS patients were also lower than in metallic EES patients. 

The presence of calcium and the sum arc of calcium were similar for both devices prior to the procedure. Patients in the metallic EES arm had lower lumen eccentricity index (EI) pre-procedure compared to patients in the BVS arm (0.59 vs 0.61; P=.048), but the pre-procedural asymmetry index (AI) was not significantly different.

Post-procedure, the minimum scaffold/stent area (MSA) in the BVS group measured 4.87 mm2 and 5.72 mm2 in the metallic EES group (P<.001). Lesions treated with BVS were more eccentric (27.3% vs 4.5%; P<.001) and asymmetric (62.1% vs 29.5%; P<.001) compared with lesions treated using metallic EES.

Researchers noted that of the 506 total lesions, the scaffold/stent expansion index was calculated in 425 lesions—the remaining 71 could not be calculated because of side branches at both the proximal and distal edges of the scaffold/stent. Only a few lesions could achieve optimal scaffold stent expansion (8.0% in BVS and 20.0% in metallic EES; P<.001).

At 1 year, the DoCE rates were 5.2% in BVS and 3.1% in metallic EES arms (P=.29). The optimal stent expansion (OSE) and suboptimal stent (SSE) groups had similar DoCE rates (4.2% vs 4.4%; P=.93). The asymmetric group was associated with a higher risk of DoCE compared with the symmetric group when stratified by the AI (1.8% vs 6.9%; P=.007). The asymmetric group had a higher event rate, mostly driven by a higher MI incidence, but incidences of cardiac death, definite or probable scaffold/stent thrombosis were not significantly different between groups. Eccentric lesions did have higher rates of DoCE, TLR, and definite or probable scaffold/stent thrombosis compared with concentric lesions when stratified by the EI.

An AI >0.30 after implantation was determined as an independent predictor for DoCE after subsequent multivariate analysis of both models (adjusted hazard ratio: 3.43; P=.037). There was no consistency of statistical significances of pre-procedural diameter stenosis, pre-procedural negative remodeling lesion, total stent length, or overlapping implantation.

In comparing patients with asymmetric vs symmetric lesions, researchers found a lower prevalence of diabetes (22% vs 27.2%; P=.04), more complex lesions, and more moderate to severe calcification. “Furthermore, the baseline MLA [minimal lumen area], post-procedural MSA, and EI were lower in the asymmetric group, along with a higher prevalence of eccentric device after implantation (38.1% vs 0%; P<.001, respectively).”

The interaction between subgroup and asymmetry status was performed to confirm if there was a consistent influence of asymmetry among that patient subgroup. “Post-implantation device asymmetry compared with symmetry was consistent in all subgroups,” researchers wrote. “As the sample size was small for most subgroups, caution should be used in the interpretation of these results and in drawing conclusions.”

“The current study suggested that a single variable of the EI is not enough to predict future events without taking into consideration the homogeneity of the stent/scaffold expansion and it seemed that AI was a more discriminate parameter compared to the EI,” they concluded.

Disclosure: The ABSORB II trial was sponsored by Abbot Vascular.

Reference

Suwannasom P, Sotomi Y, Ishibashi Y, et al. The impact of post-procedural asymmetry, expansion and eccentricity of bioresorbable everolimus-eluting scaffold and metallic everolimus-eluting stent on clinical outcomes in the ABSORB II trial. JACC Cardiovasc Interv. 2016. doi:10.1016/j.jcin.2016.03.027.