Occult Anterograde Flow Predicts Early Recanalization After IV tPA | Journal Scan

Study Questions:

Can findings on multimodal computed tomography (CT) imaging identify permeable thrombus that is more likely to lyse, leading to recanalization, after intravenous (IV) tissue-type plasminogen activator (tPA)?


The authors used data from an imaging study of acute ischemic stroke patients who received IV tPA and had multimodal CT imaging (noncontrast CT, CT angiography [CTA], and CT perfusion [CTP]) showing a complete intracranial vessel occlusion. CTP images were co-registered with CTA images to determine when contrast reached the proximal and distal ends of the occluding thrombus. Regions of interest were identified in the vessel, distal to the occlusion, and the timing of contrast arrival in these regions was modeled using linear regression. Flow away from the thrombus suggested occult anterograde flow (OAF) through a permeable thrombus while flow toward the thrombus suggested retrograde filling of the vessel through collaterals. Using multimodal CT imaging data, the authors also divided patients into three groups: anterograde flow, slow retrograde flow, and rapid retrograde flow (suggesting more robust filling through collateral vessels), and used multivariable logistic regression to examine the association between these flow patterns and recanalization on subsequent angiography or CTA.


Sixty-six patients with predominantly anterior circulation strokes (92% of patients) treated with IV tPA a median of 118 minutes after symptom onset were included. Seventeen patients had OAF, and these patients were more likely to show recanalization (odds ratio [OR], 4.57; 95% confidence interval [CI], 1.11-21.42). Patients with anterograde flow were more likely to recanalize than patients with slow retrograde flow (OR, 12.15; 95% CI, 2.05-71.91). Patients with rapid retrograde flow were not more likely to recanalize than patients with slow retrograde flow (OR, 2.15; 95% CI, 0.43-10.72).


The authors concluded that OAF, identified using multimodal CT imaging, predicts recanalization in acute ischemic stroke patients treated with IV tPA.


In acute ischemic stroke, recanalization is associated with better outcomes. In patients with large artery occlusions, early recanalization rates with IV tPA are low. Patients with permeable thrombi and OAF may be more likely to recanalize after IV tPA, and this study provides a quantitative assessment of OAF using multimodal CT imaging. The patients in this study were treated with IV tPA quickly, which may limit the generalizability of these results to other patients treated with IV tPA at longer time frames. The CTP images undergo post-acquisition processing, and it is unclear if different CTP software would yield similar results. The confidence intervals in this study were wide, and additional work needs to be done to validate this technique, but it has the potential to help clinicians make decisions regarding intra-arterial stroke treatment.

Clinical Topics: Dyslipidemia, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Lipid Metabolism, Interventions and Imaging, Angiography, Computed Tomography, Nuclear Imaging

Keywords: Tissue Plasminogen Activator, Stroke, Angiography, Thrombosis, Thrombolytic Therapy, Arteries, Tomography, X-Ray Computed, Perfusion Imaging, Multimodal Imaging, Linear Models, Logistic Models

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