CTA and CTP in the Evaluation and Treatment of Acute Ischemic Stroke Patients: Opportunities, Standards, and Special Considerations
Presented by Edward Sloan, MD, MPH, FACEP
What is the role of multi-modal CT testing in the diagnosis and treatment of patients with acute ischemic stroke?
When do non-contrast CT, CT angiography (CTA), and CT perfusion (CTP) assist in decision making when treating acute ischemic stroke patients?
How can the care of ischemic stroke patients be optimized to improve patient outcomes with best practices in the Emergency Department?
Educational Objectives:
(1) Enhance understanding of pathophysiology of acute ischemic stroke.
(2) Understand what are CTA and CTP neuroimaging and how they are performed.
(3) Know when CTA and CTP are indicated in the diagnosis of AIS patients, and how patient outcomes are influenced by this testing.
(4) Review AHA ASA guidelines recs with respect to neuroimaging for AIS patients.
(5) Conclude the role of NCCT, CTA, CTP, and MR for Emergency Department AIS patients.
(6) Consider the additional value of MR imaging, MRA, MR DWI in neuroimaging of acute ischemic stroke patients.
(7) Make it possible to learn based on key clinical questions.
Is the use of CTA the standard of care in AIS patients?
In centers where NCCT CTA can be rapidly performed serially, this approach is optimal.
Baseline creatinine may not be universally required.
Identification of LVO and subsequent EVT possible use can often be achieved with NCCT CTA.
CTA use, however, is not required for thrombolytic Rx up to 4.5 hours in AIS patients
Is the use of CTP standard of care in AIS patients?
CTP more consistently able to predict disease with AI
CTP results may vary across CTP AI software packages
CTP AI not likely used as broadly as NCCT, CTA
CTP mostly in comprehensive stroke centers /systems
NCCT+CTA+CTP may be most cost effective (Martinez 2020)
Qualifiers in literature suggest more to be learned prior to standard use with common AI decision making that is generalizable to all centers caring for AIS patients.
What is the role of MR imaging and perfusion studies for AIS patients?
MR detects hemorrhage and stroke etiologies well
MRA similar utility to CTA, but more often subacute
MRA can be done without gadolinium contrast
MR DWI detects hyperacute ischemia (Sens, spec, accurate)
+ DWI without FLAIR changes suggests over 6 hours
Diffusion-perfusion mismatch selects patients for extended window for reperfusion Rx (DEFUSE-3)
MRV useful when venous occlusion suspected
What do the AHA ASA guides say about imaging, TT, ETV?
NCCT and MR both exclude ICH prior to thrombolysis
CTA CTP or MRA DWI useful in: Wakeup stroke, ?? ictus time, and EVT an option
Give IV alteplase prior to MRI exclude microbleeds
Don’t delay IV alteplase to obtain perfusion studies
Wakeup stroke or ?? ictus time: use MR to find DWI+FLAIR- patients for IV alteplase within 4.5 hours (large penumbra and small core infarct)
If patient meets ETV criteria, CTA MRA to image CNS vessels
If LVO is suspected, CTA MRA to image CNS vessels
If no renal history, no need for creatinine prior
If ETV in play, image extracranial carotids, vertebrals
Image collaterals when considering mechanical EVT
Anterior LVO, 6-24 hours, use CTP or DW-MRI to verify eligibility for EVT
AIS patients less than 6 hours, ASPECTS score over 6 with LVO: CT CTA or MR MRA can guide EVT referral as opposed to adding perfusion studies to the decision making
Neuroimaging in AIS Conclusions
NCCT and IV thrombolytic therapy are key
CTA quickly without creatinine to show LVO
CTP provides Rx guidance to experts when available as part of neuroimaging workflow
MRA, DWI for semi-urgent and unusual stroke
Knowing which patients benefit from EVT is key
Awareness of stroke system allows for optimal EVT triage even with NCCT alone
AHA/ASA guidelines address AIS neuroimaging
Conclusions: MRA & MRI-DWI
MR detects microhemorrhage (not necessary)
MRA no better than CTA (CTA is good)
CTP and MRI-DWI correlate well
MRI-DWI better for posterior circulation, lacunar infarcts, watershed, small vessel infarcts
No substantial benefit except with above
MRI-DWI requires subacute evaluation (not available acutely unless “MR light” possible, with 10-minute table time at EVT center)
The Foundation for the Education and Research in Neurological Emergencies (FERNE) is an independent not-for-profit organization committed to the following principles:
1. Patients with neurologic emergencies deserve quality emergency care.
2. The emergency care for neurologic emergencies can be enhanced through quality scientific research.
3. Emergency medical care providers can provide optimal medical care for patients with neurological emergencies through participation in quality medical education that highlights state-of-the-art neurologic care.
Go to FERNE.org to learn more and participate in improving the care of all patients with neurological illnesses and injuries.
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