Recanalization Does Not Always Equate to Reperfusion: No-Reflow Phenomenon After Successful Thrombectomy

BACKGROUND: Thrombectomy for acute large vessel occlusion is a well-established treatment for stroke prevention. However, futile recanalization cases, where no-reflow occurs despite successful recanalization, have been reported. This study aimed to assess cerebral hemodynamics immediately after thrombectomy and their relationship with clinical outcomes. METHODS: We prospectively enrolled patients who underwent successful thrombectomy (modified Thrombolysis in Cerebral Infarction [TICI] ≥2b) for internal carotid artery or middle cerebral artery occlusions at Nagasaki University Hospital between January 2021 and December 2023. Preoperative magnetic resonance imaging was performed, followed by flat-panel computed tomography perfusion 30 minutes after recanalization. Areas with cerebral blood flow <45%, Tmax >6 seconds, and cerebral blood volume <34%, 38%, and 42% were analyzed, and hypoperfusion intensity ratio and cerebral blood volume index were calculated using Rapid ANGIO. We assessed the correlation of these parameters with infarct expansion, hemorrhagic transformation, and poor outcomes, defined as modified Rankin Scale scores of 4 to 6, at 3 months. RESULTS: A total of 65 cases were analyzed. Infarct expansion, defined as a decrease in Alberta Stroke Program Early CT Score, occurred in 23 cases (12/28 TICI 2b and 11/37 TICI 2c/3). No-reflow, defined as Tmax >6 seconds, was observed in 80% of cases (52/65), regardless of TICI grade. The infarct expansion group in TICI 2b had a significantly larger residual cerebral blood flow <45% area (32.9±30.4 versus 10.6±14.5 mL) and a lower cerebral blood volume index (0.71±0.2 versus 0.92±0.2). Cerebral blood flow <45% (r=−0.57; P <0.001) and cerebral blood volume <34% (r=−0.40; P =0.001), not Tmax >6 seconds, negatively correlated with postoperative Alberta Stroke Program Early CT Score. In logistic regression analysis, cerebral blood flow <45% was an independent predictor of poor outcomes (adjusted odds ratio, 1.05 [95% CI, 1.00–1.11]; P =0.039). CONCLUSIONS: No-reflow is common after thrombectomy, suggesting that successful recanalization does not always result in immediate tissue reperfusion. Hemodynamic impairment postthrombectomy may persist, highlighting the need for adjunctive treatments.