Introduction/Purpose Direct cerebral bypass has been shown to decrease risk of stroke in well selected patients. Surgical decisions, including bypass construct geometry, may influence the hemodynamic environment and results. However, few studies have quantitatively assessed the impact of parameters on bypass hemodynamics. As a result, surgical decisions are often subjective. In this study, we investigated how vessel flow rates and graft vessel anastomosis angle affect perfusion using both in vitro experiments and in silico simulations.

Materials and Methods Direct bypass surgery models with varying graft angles (30–90°) were manufactured as polydimethylsiloxane blocks. An in vitro flow loop was designed to simulate the in vivo conditions. Stereo particle image velocimetry (PIV) was used to assess flow. Computational fluid dynamic (CFD) simulations were also performed. A total of 45 cases were evaluated with varying inlet and graft flow rates. The best performing scenarios were defined as those that yielded the largest retrograde flow rate in the inlet vessel.

Results The 90° angle yielded only forward flow, while the 60° angle resulted in minimal flow. By increasing the graft vessel flow rate to 20 mL/min, backflow was observed in all cases, with the 60° case yielding optimal flow (figure 1). There was agreement between the PIV and CFD velocity fields.

Conclusion This work presents a novel multi-modal investigation aimed at improving outcomes in direct cerebral bypass surgery. To our knowledge, this is the first such study to evaluate how graft angle affects bypass hemodynamics. Compared with the 90° cases, the 60° bypass delivered more fluid to the target area, with a higher percentage of reverse flow across the inlet. Furthermore, no retrograde flow was observed until the graft (cut) flow was increased to 10 ml/min. Future studies will incorporate other features of bypass constructs as well as patient-specific bypass geometries.

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Abstract E-135 Figure 1

PIV velocity fields for (a) 90°and (b) 60°graft angles with 5 ml/min inlet and 5 ml/min graft flow rates. PIV/CFD velocity fields for (c)/(e) 90° and (d)/(f) 60°graft angles with 5 ml/min inlet and 20 ml/min graft flow rates

Disclosures E. Church: 2; C; Stryker Neurovascular. C. Peng: None. M. Brindise: None.