Measurement of Intraoperative Graft Flow Predicts Radiological Hyperperfusion during Bypass Surgery in Patients with Moyamoya Disease

INTRODUCTION: Moyamoya disease (MMD) is a rare cerebrovascular disease associated with cerebral infarction or hemorrhage. Hyperperfusion is the most significant complication of direct bypass surgery. Previous research has shown that an increase in cerebral blood flow (CBF) is strongly related to symptomatic hyperperfusion and highlighted the importance of postoperative assessment of CBF. OBJECTIVE: The principal aims of this study were to quantitatively analyze the relationship between intraoperative graft flow and increase in CBF and to evaluate the effectiveness of intraoperative graft flow measurement during bypass surgery for patients with MMD. METHODS: This study included 91 surgeries in 67 consecutive adult patients with MMD who underwent direct revascularization surgery at our institution between November 2013 and September 2018. Intraoperative graft flow of the branches and main trunk was measured in all patients, after anastomosis had been established. Postoperative CBF measurements were performed under sedation, immediately after surgery. Radiological hyperperfusion was defined as focal high uptake, as determined by CBF imaging immediately after surgery. Patients were divided into two groups (radiological hyperperfusion and nonradiological hyperperfusion groups), and the relationship between intraoperative graft flow and radiological hyperperfusion was analyzed. RESULTS: Significant differences were observed between the radiological hyperperfusion and nonradiological hyperperfusion groups in terms of intraoperative graft flow of both the branch (median 72 vs. 42 mL/min, respectively; p < 0.01) and main trunk (median 113 vs. 68 mL/min, respectively; p < 0.01). A receiver-operating characteristic analysis was performed to test the utility of intraoperative flow as a quantitative measure. We set the cutoff values for the intraoperative branch and main trunk flow at 57 mL/min (sensitivity: 0.707, specificity: 0.702; area under the curve [AUC]: 0.773; 95% confidence interval [CI]: 0.675–0.871) and 84 mL/min (sensitivity: 0.667, specificity: 0.771; AUC: 0.78; 95% CI: 0.685–0.875), respectively. CONCLUSIONS: Measuring intraoperative graft flow during bypass surgery may be an effective means of predicting hyperperfusion and could serve to facilitate early therapeutic intervention such as strict blood pressure control.