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Thrombus and Recanalization in Acute Ischemic Stroke
Study Questions:
What clinical and imaging characteristics are associated with vessel recanalization in acute ischemic stroke?
Methods:
This was a multicenter, prospective cohort study performed at 12 centers in North America, Europe, and East Asia between March 2010 and March 2016. The authors enrolled patients with acute ischemic stroke who presented within 12 hours from their last known well time who had a computed tomographic angiography (CTA) of the head showing a symptomatic intracranial (non-vertebrobasilar) thrombus. Information regarding clinical features, comorbidities, timing of imaging, and alteplase administration and endovascular stroke treatment, if applicable, was collected. Patients underwent a follow-up CTA of the head at 4 (±2) hours after the initial CTA unless conventional angiography was done. A blinded expert characterized the location of the intracranial thrombus. A clot burden score and a clot permeability score assessed thrombus characteristics. The primary outcome was successful recanalization, evaluated on follow-up imaging—either CTA or angiography. Patients who received intravenous (IV) alteplase were analyzed separately from those who did not receive IV alteplase.
Results:
There were 575 patients included in the analyses. The median age was 72 years, 52% were men, the median National Institutes of Health Stroke Scale score was 14, and the median time from last known well to baseline CTA was 114 minutes. About half (47.8%) of the patients received IV alteplase only, 33.9% were treated with IV alteplase and endovascular thrombectomy, 8.3% received endovascular thrombectomy alone, and 9.9% did not receive thrombolysis. Recanalization was assessed by CTA in 57.7% and angiography in the remainder. The median time from baseline CTA to recanalization assessment was 158 minutes. Successful recanalization occurred in 157 patients (27.3%). Of patients who received IV alteplase, 30.4% had successful recanalization versus 13.3% of patients who were not treated with IV alteplase.
In patients treated with IV alteplase, after adjustment, predictors of recanalization were distal thrombus location, greater clot permeability, lower clot burden, and longer time from alteplase start to recanalization assessment. In patients not treated with IV alteplase, only male sex was associated with recanalization in multivariable analysis.
Conclusions:
Imaging findings and time are associated with successful recanalization in patients treated with IV alteplase.
Perspective:
In acute ischemic stroke, recanalization is associated with improved outcomes. Prior work has shown that patients who receive IV alteplase have higher rates of recanalization, a finding that is supported by this research. With new paradigms of stroke care, such as endovascular thrombectomy, which are only available at specialized centers, identifying patients who are likely to recanalize after IV alteplase may prevent unnecessary transfers. The thrombus factors identified have strong face validity for predicting recanalization. As time elapses, there is more time for thrombolysis to occur, which likely explains the association between assessment time and recanalization.
This study is strengthened by the authors’ use of CTA and angiography to evaluate for recanalization rather than more limited techniques (such as transcranial Doppler). A potential weakness is the relatively small number of patients included over 7 years, suggesting that patients not included in the study may differ from those in the analyses in important ways. By identifying imaging factors associated with recanalization, this work will inform future trials aiming to determine optimal transfer strategies.
Clinical Topics: Cardiac Surgery, Dyslipidemia, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Vascular Medicine, Aortic Surgery, Lipid Metabolism, Interventions and Imaging, Interventions and Vascular Medicine, Angiography, Computed Tomography, Nuclear Imaging
Keywords: Brain Ischemia, Coronary Angiography, Diagnostic Imaging, Endovascular Procedures, Intracranial Thrombosis, Stroke, Thrombectomy, Thrombosis, Tissue Plasminogen Activator, Tomography, X-Ray Computed, Vascular Diseases
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