Study overview and clinical question
Good venous outflow (VO) is associated with favorable outcomes and a higher likelihood of reperfusion following endovascular thrombectomy (EVT). Can early tPA administration in acute ischemic stroke patients improve the VO profile in the baseline CTA performed before EVT?
The study authors (Dr. Tobias Faizy et al.) hypothesize that tPA administration within 4.5 hours after stroke onset and before EVT triage can result in favorable VO profiles on baseline CTA in LVO patients.
Venous outflow reflects the efficiency of cerebral microvascular drainage and has emerged as an important imaging marker associated with tissue viability and clinical outcomes in acute ischemic stroke.
Understanding whether early intravenous thrombolysis can favorably influence venous outflow before endovascular treatment may help refine imaging-based triage and treatment strategies for large vessel occlusion stroke.
Key takeaways:
- Administering tPA before EVT in acute ischemic stroke patients with LVO was independently associated with favorable VO profiles on baseline CTA imaging.
- Patients who received tPA before EVT also had more favorable functional outcomes 90 days after treatment.
These findings suggest that tPA administration before EVT may provide physiologic benefits beyond clot dissolution by improving downstream venous drainage.
Imaging analysis and study design
This study used a retrospective, imaging-based cohort design to evaluate the relationship between early tPA administration and venous outflow on baseline CT angiography.
All patients had confirmed anterior circulation large vessel occlusion and underwent standardized multimodal CT imaging as part of EVT triage.
The retrospective cohort study included 717 patients from two hospitals, Stanford University and University Medical Centre Hamburg-Eppendorf. The patients had anterior LVO, and baseline NCCT, CTA, and CTP scans were available. They received tPA, EVT, or both within 16 hours of symptoms onset.
The patients were divided into two groups: those who received tPA before performing baseline CTA and those who didn't receive tPA.
Baseline imaging and scoring methods
Each imaging metric was selected to assess different aspects of cerebral perfusion, collateral circulation, and tissue injury relevant to acute stroke outcomes.
- The Alberta Stroke Program Early CT Score was determined on baseline NCCT.
- The VO profile was assessed using Cortical Vein Opacification Score (COVES) on baseline CTA.
- Pial arterial collaterals were evaluated using a modified Tan scale on baseline CTA.
- The CTP scans were processed using Rapid CTP to determine the core and penumbra volumes.
- The final infarct volume was evaluated on follow-up NCCT scans.
tPA administration and VO profile
Administering tPA before EVT was independently associated with favorable VO profiles on baseline CTA imaging (p<0.001). Patients who received tPA before EVT also had more favorable functional outcomes 90 days after treatment (p<0.001).
In addition to tPA administration, good pial collaterals in baseline CTA, lower presenting NIHSS, and age were also independently associated with favorable VO profiles on baseline CTA.
Clinical implications for EVT in LVO stroke
The benefits of tPA plus EVT versus EVT alone have been widely debated and studied in several trials. This study shows that tPA administration could help improve VO before EVT and increase the likelihood of successful reperfusion in LVO patients.
Imaging support for acute stroke decision-making
Rapid CTP is the only FDA-cleared software to aid patient selection for mechanical thrombectomy.
FAQs
What is venous outflow in acute ischemic stroke?
Answer:
Venous outflow refers to the drainage of blood from the brain through the cortical veins after arterial inflow. In acute ischemic stroke, favorable venous outflow on CT angiography is associated with better tissue perfusion, higher likelihood of reperfusion, and improved clinical outcomes.
How is venous outflow assessed on CT angiography?
Answer:
Venous outflow is commonly assessed on baseline CT angiography using the Cortical Vein Opacification Score (COVES). This score evaluates the degree of contrast opacification in key cortical veins and provides a quantitative measure of cerebral venous drainage.
Does administering tPA before EVT improve venous outflow?
Answer:
In this retrospective study, administering intravenous tPA before endovascular thrombectomy was independently associated with more favorable venous outflow profiles on baseline CTA. This association remained significant after adjusting for collateral status and other clinical variables.
Why is venous outflow important for endovascular thrombectomy outcomes?
Answer:
Favorable venous outflow reflects effective microvascular perfusion and efficient cerebral blood drainage. Patients with good venous outflow are more likely to achieve successful reperfusion and experience less infarct progression after endovascular thrombectomy.
How does venous outflow differ from arterial collateral assessment?
Answer:
Arterial collateral assessment evaluates alternative pathways of blood inflow to ischemic tissue, while venous outflow reflects downstream microvascular drainage. Both provide complementary information, but venous outflow may better capture tissue-level perfusion status.
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