BACKGROUND: The differentiation between intracranial atherosclerotic stenosis (ICAS) and intracranial embolism as the immediate cause of acute ischemic stroke requiring endovascular therapy is important but challenging. In cases of ICAS, we often observe a phenomenon we call the microcatheter "first-pass effect," which is temporary blood flow through the occluded intracranial artery when the angiographic microcatheter is initially advanced through the site of total occlusion and immediately retrieved proximally. OBJECTIVE: To evaluate whether this microcatheter first-pass effect can be used to differentiate ICAS from intracranial embolism. METHODS: A total of 61 patients with acute ischemic stroke resulting from large intracranial artery occlusion and in whom recanalization was achieved by endovascular treatment were included in the study. The microcatheter first-pass effect was tested in these patients. The sensitivity, specificity, positive predictive values (PPV), and accuracy of the microcatheter first-pass effect for prediction of ICAS were assessed. RESULTS: The microcatheter first-pass effect was more frequently observed in patients with ICAS than in those with intracranial embolism (90.9% vs 12.8%, P < .001). For identifying ICAS, sensitivity, specificity, PPV, and accuracy of the microcatheter first-pass effect were 90.9%, 87.2%, 80.0%, 88.5%, respectively. CONCLUSION: The sensitivity and PPV of the microcatheter first-pass effect are high for prediction of ICAS in patients with acute symptoms.
BACKGROUND: The differentiation between intracranial atherosclerotic stenosis (ICAS) and intracranial embolism as the immediate cause of acute ischemic stroke requiring endovascular therapy is important but challenging. In cases of ICAS, we often observe a phenomenon we call the microcatheter "first-pass effect," which is temporary blood flow through the occluded intracranial artery when the angiographic microcatheter is initially advanced through the site of total occlusion and immediately retrieved proximally. OBJECTIVE: To evaluate whether this microcatheter first-pass effect can be used to differentiate ICAS from intracranial embolism. METHODS: A total of 61 patients with acute ischemic stroke resulting from large intracranial artery occlusion and in whom recanalization was achieved by endovascular treatment were included in the study. The microcatheter first-pass effect was tested in these patients. The sensitivity, specificity, positive predictive values (PPV), and accuracy of the microcatheter first-pass effect for prediction of ICAS were assessed. RESULTS: The microcatheter first-pass effect was more frequently observed in patients with ICAS than in those with intracranial embolism (90.9% vs 12.8%, P < .001). For identifying ICAS, sensitivity, specificity, PPV, and accuracy of the microcatheter first-pass effect were 90.9%, 87.2%, 80.0%, 88.5%, respectively. CONCLUSION: The sensitivity and PPV of the microcatheter first-pass effect are high for prediction of ICAS in patients with acute symptoms.