The cut flow index revisited: utility of intraoperative blood flow measurements in extracranial-intracranial bypass surgery for ischemic cerebrovascular disease

Abstract

OBJECTIVEIn extracranial-intracranial (EC-IC) bypass surgery, the cut flow index (CFI) is the ratio of bypass flow (ml/min) to donor vessel cut flow (ml/min), and a CFI ≥ 0.5 has been shown to correlate with bypass patency. The authors sought to validate this observation in a large cohort of EC-IC bypasses for ischemic cerebrovascular disease with long-term angiographic follow-up.METHODSAll intracranial bypass procedures performed at a single institution between 2003 and 2018 were reviewed. Demographic, clinical, angiographic, and operative data were recorded and analyzed according to bypass patency with univariate and multivariate statistical analyses.RESULTSA total of 278 consecutive intracranial bypasses were performed during the study period, of which 157 (56.5%) were EC-IC bypasses for ischemic cerebrovascular disease. Intraoperative blood flow measurements were available in 146 patients, and angiographic follow-up was available at a mean of 2.1 ± 2.6 years after bypass. The mean CFI was significantly higher in patients with patent bypasses (0.92 vs 0.64, p = 0.003). The bypass patency rate was 83.1% in cases with a CFI ≥ 0.5 compared with 46.4% in cases with a CFI < 0.5 (p < 0.0001). Adjusting for age, sex, diagnosis, and single versus double anastomosis, the CFI remained a significant predictor of bypass patency (p = 0.001; OR 5.8, 95% CI 2.0–19.0). A low CFI was also associated with early versus late bypass nonpatency (p = 0.008).CONCLUSIONSA favorable CFI portends long-term EC-IC bypass patency, while a poor CFI predicts eventual bypass nonpatency and can alert surgeons to potential problems with the donor vessel, anastomosis, or recipient bed during surgery.