Update on Imaging, thrombolysis and stenting in Stroke Flashcards
What is the background for stroke?
11% of all deaths in England and Wales
500,000 dependent for ADLs
What has changed in the last 6 years for acute stroke care?
- RCP audit highlights shortcomings for UK stroke care
- Thrombolysis rate gradually improving vs up to 1-% in continental Europe
- National Stroke Strategy published
- NICE guidelines on Stroke
- Stroke moved up the DOH agenda in England
- Stroke Networks formed
- Hyperacute stroke units set up
- Thrombectomy becoming standard of care
Brain imaging should be performed immediately for people with acute stroke if any of the following apply:
- Indication for thrombolysis or early anticoagulation treatment
- On anticoagulant treatment
- Known bleeding tendency
- Depressed level of consciousness, GCS < 13
- Unexplained progressive or fluctuating symptoms
- Papilloedema, Neck stiffness or fever
- Severe headache at an onset of stroke’s symptoms
What should be done for people with acute stroke without indication for immediate brain imaging scanning?
should be performed within 1 hour of arrival in hospital
What do we need know from acute CT scan in a patient with a clinical diagnosis of acute stroke:
- Is the scan normal? i.e. can we start Thrombolysis refer for thrombectomy
- Confirm diagnosis of acute stroke and size
- Exclude haemorrhage
- Exclude stroke mimic
What happens if CTA is available?
- Looks at all the blood vessels
- If you have a stroke 20% of patients will have disease of the carotid artery that needs treatment with carotid endarterectomy (CEA)
- 10% of patients who are suitable for thrombectomy
- Exclude significant stenosis of the carotid and vertebral arteries and any intracranial stenosis
- Enables fast tract to endarterectomy or discharge from a HASU to SU
What should patients with suspected TIA undergo?
diffusion weighted MRI except where contraindicated
TIA at MRI superior to CT
pick up small diffusion abnormalities that may not be seen on a CT
NASCET and ECST:
- Long term benefit of carotid endarterectomy compared with medical treatment
- If you have a stenosis greater than 70% - absolute risk reduction is pretty good
- Not good treating less than 50% stenosis
- Above 99%, the flow drops in the carotid
When was benefit from surgery greatest in?
men, patients aged 75 years or older, and those randomised within 2 weeks after their last ischaemic event
What does the benefit from endarterectomy depend on?
not only on the degree of carotid stenosis, but also on several other clinical characteristics such as delay to surgery after the presenting event
What is readily availble on all A&e for acute stroke?
CT
What are the features for CT?
- Acute haemorrhage, may show infarct
- CTA for vessels
- CTP for extent of perfusion defect, CBV predicts infarct volume (DWI)
- Convenient
- Very quick < 5 minutes scan time
- Some time on workstation; new packages coming
- CT easy in ill patients
- Radiation secondary importance of having acute stroke
What are the features for MRI?
- Sequences to detect lesion and blood
- Gradient echo (T2*) greater than CT (microbleed)
- DWI >CT
- MRA
- Perfusion – whole head
- Longer scan time, less post processing
- Access
- New sequences
- Will become easier to use in the future
What is the Alberta Stroke Program Early CT score ‘‘ASPECTS’’?
10-point quantitative topographic CT scan score used in patients with middle cerebral artery stroke
What has the ASPECT score been adapted for?
Posterior circulation
What do we see in CT for acute stroke?
- Thrombus in the vessels
- Altered tissue perfusion
- Cytotoxic oedema
- Vasogenic oedema
Where to look in CT in Acute Stroke?
- Vessels
- Grey: white differentiation
- Basal ganglia/capsules
- Insular ‘’ribbon’’
- Cortex
- Swelling: sulci effaced
What can easily be seen on the CT, and picked up quicker than MRI?
Haemorrhage
What can’t MRI be used as ?
Single sequence investigation (‘‘turbo charged CT’’)
What must haemorrhage include?
Blood sensitive sequence
- GRE or parenchyma
- FLAIR for SAH
What should not be used alone for acute stroke imaging?
DWI
What is Low Grade Glioma and what to look for?
- Can be peripheral, wedge shaped and non-enhancing
- Look for:
- Age and History
- Density, swelling but non-enhancing
- DWI characteristics and age of lesion
What is the most common cause of stroke for pregnant ladies?
Venous thrombus
Where is Core observed in?
diffusion, reduction in blood volume and an increase in MTT [mean transient time]
• Due to block of middle cerebral artery
What is the aim of thrombolysis?
reperfuse penumbra before it infarcts
What is TIA?
Like a stroke without core infarct in eloquent area
- Milder perfusion deficit
- Often has DWI lesion
What does ASPECT aid?
Methodical image analysis and prognosticatio
What is not very dark ?
Infarct less than 24 hours
What do infarcts not usually present with?
Fits
Especially in young people
What must be included if using MRI for acute stroke?
Gradient echo imaging
What are a few tips for looking at scans?
- Ambient lighting, monitor quality etc
- Hang as well as scroll
- Correct window/centring
- Provide/obtain clinical info
- Think about anatomy
(speech not always left dominant) - Eye deviation
What should be compared with initial scan?
Routinely obtain post thrombolysis follow up imaging
What are the objectives of I.V. Thrombolysis?
- To improve clinical outcome at 3 month
- Proportion of patients without handicap (mRS 0-1)
- Proportion of patients without dependency (mRS 0-2)
What are the Modified Rankin scale?
0 - no symptoms 1- No significant disability despite symptoms 2- Slight disability 3- Moderate disability 4- Moderately severe disability 5- Severe disability 6- Dead
What cannot be the objectives of I.V. thrombolysis?
- To reduce mortality only
- To reduce handicap only
- To improve recanalization only [return of blood flow to a venous segment that had previously been occluded]
Meta-analysis of trials
NNT to prevenet 1 death or dependency (mRS 2-6)
- <90 minutes: 2
- 90-180 minutes: 7
- 180-270 minutes: 14
For every 20 patients treated
- 1 extra will be cured (Rankin 0)
- 1 extra will do very well (Rankin 1)
So, whom would you thrombolyse?
- Patient whom you think had a stroke
- Within 4 ½ hours
- Normal scan
- No contraindications
What are the contraindications of thrombolysis?
- Age under 18 or over 8- years
- Very severe stroke
- Prior stroke and concomitant diabetes
- History of haemorrhagic diabetic retinopathy
- Receiving oral anticoagulants e.g. warfarin
- Blood pressure limits >185/110
- IV medication needed to reduce BP to these limits
- Extensive infarction on CT
What are the 5 trials for thrombectomy for acute ischaemic stroke?
- MR CLEAN
- ESCAPE
- EXTEND IA
- SWIFT-PRIME
- REVASCAT
- THRACE
Number needed to treat: 3-7
- Within 2-3 hours: 3
- Within 41/2 hours: 7
- PCI 35-45- to get benefit
What can marked benefits be observed in?
Endovascular treatment
What are the inclusion criteria for Throbectomy?
Achieved within 6 hours of onset of symptoms and where:
- Inadequate response to IV thrombolysos by time of groin puncture
- Patients unable to receive IV thrombolysis because recent surgery or on anticoagulants
What is the challenge for Thrombectomy?
- STAFF
- CTA n DGH Local HASU
- Drip and ship or mothership
- Ambulance transfer HEMS
- Repatriation
What is the patient pathway?
- Admission to nearest hospital with an hyperacute stroke unit
- Undergo initial investigations - CT and CTA
- Start treatment whee appropriate with IV tPA
- Critical transfer to nearest thrombectomy centre
