## 4 Discussion  
In this study, a validated OCT-based reconstruction methodology was employed to analyze a scaffolded coronary artery geometry involving a bifurcation. The actual configuration of the implanted Absorb BVS was part of the physical domain and patient's hemodynamics was simulated with a commercial CFD software. Then, it was demonstrated: (i) The possibility of calculating the WSS distribution and blood flow patterns in bifurcation segments treated with an Absorb BVS; (ii) the potential application of such simulations in the clinical setting by matching the numerical methods with imaging and clinical outcomes in patients. In the authors' opinions, the proposed approach can improve the understanding of the hemodynamic impact of any scaffold design at coronary bifurcations. The additional 9-months follow-up intravascular images enabled the quantification of vessel remodeling after the implantation of a bioresorbable scaffold when treating non-complex bifurcations with a provisional strategy.  
In the literature, the effect of the presence of Absorb BVS on WSS has been limited to relatively straight coronary vessels without bifurcations and the CFD physical domain did not include the scaffold, as the innermost lumen boundary was traced. [PERSON] and colleagues [18] evaluated the effect of WSS after two years from the intervention in the scaffolded segment. Results were compared with the vascular healing response of eight patients from the ABSORB A cohort that underwent 5-year invasive follow-up OCT acquisition. It was found that regions exposed to low shear stress had thinner fibrous caps. In 12 patients from the ABSORB B cohort, [PERSON] and colleagues [17] investigated the effect of WSS after BVS implantation on neointimal growth at 1 year. Similar to studies with metal stents, areas that were exposed to low WSS showed more intimal thickening at follow-up. Analysis of the peri-strut flow distribution showed regions of low WSS as well as recirculation zones on both sides of the struts, and regions of high WSS at the top. This hemodynamic profile may explain the higher thrombotic rate of the Absorb BVS compared to drug eluting stents [19]. One of the postulated mechanisms is the activation of platelets induced by high WSS on top of struts and sequestration in low recirculation zones adjacent to struts causing thrombus formation [20].  
According to the most recent computational works about the application of polymeric bioresorbable scaffolds, such as the work of [PERSON] and co-authors [21], and the review presented by [PERSON] and colleagues [3], the study here described is the first that includes the reconstruction of coronary bifurcations with an implanted scaffold, the actual deployed configuration of which was included in the model [6]. Nevertheless, the applied method has limitations related to the periodic deformation of the coronary artery that affects the change of lumen cross-section area during the OCT pullback. Moreover, rigid wall conditions, with the coronary artery model fixed in the space domain,  
Figure 7: Boxplots of the computed percentage of restenosis area (**left**) and neo-intimal thickening (**right**) grouped according to the position. Results were grouped in side branch (SB), scaffolded proximal (prox) and distal (dist) regions, as well as the percentage of restenosis area was reported also for the entire scaffolded region (tot).  
were assumed for the CFD simulation. Although it has been shown that the assumption of rigid walls is acceptable in case of stented geometries [21], it is still unclear whether the coronary motion due to heart contraction can be neglected [3]. The performed CFD simulation resembled the flow condition at baseline. The scaffold bioresorption process was not modeled. Finally, it was not possible to associate each baseline and follow-up OCT images to compute the neo-intima thickening. Hence, we defined the baseline lumen contour from the follow-up OCT image dataset, as done in a previous study [17].