Jan 2023 – Diagnosis, Workup, Risk Reduction of Transient Ischemic Attack in the Emergency Department Setting: A Scientific Statement from the American Heart Association

MONTHLY FEATURE BEST PRACTICE  STATEMENT SUMMARY

BPS Citation:  Amin HP, Madsen TE, Bravata DM, Wira CR, Johnston SC, Ashcraft S, Burrus TM, Panagos PD, Wintermark M, Esenwa C; American Heart Association Emergency Neurovascular Care Committee of the Stroke Council and Council on Peripheral Vascular Disease.  DIagnosis, Workup, Risk Reduction of Transient Ischemic Attack in the Emergency Department Setting: A Scientific Statement from the American Heart Association.  Stroke. 2023 Mar;54(3):e109-e121. doi: 10.1161/STR.0000000000000418. Epub 2023 Jan 19.

Downloadable at:    https://www.ahajournals.org/doi/10.1161/STR.0000000000000418

Summary download – click

Key Guidance:    

1. Clinical Evaluation:
   1. Definition of TIA = acute onset of focal neurological symptoms followed by complete resolution/return to baseline.
   2. TIA mimics are summarized in Table 1 below.
2. Diagnostic Evaluation:  
   • Laboratory/Cardiac Testing:  The usual ED work-up for query TIA/CVA are applicable (eg. ECG, POCT glucose, CBC, chemistry, HBA1C, troponin and fasting lipid profiles).  For suspected temporal arteritis (age>50), consider adding CRP and ESR levels.  Infection and toxicology tests can be added as clinically warranted.
     1. Initial ECG can detect atrial fibrillation in 7% of ED TIA/CVA patients, but longer telemetry could have higher detection rates.
   • Risk Stratification Tools
     1. Assess for usual CVA/CVS vascular risk factors (eg. smoking, HTN, hyperlipidemia, diabetes, family history).
     2. The different ABCD risk score variants have different levels of validation in ED settings.  The ABCD² score has high sensitivity but low specificity to risk-stratify low- (score 0-3) vs high- (sore 6-7) risk patients (meta-analysis of 33 studies, >16000 patients); low-risk early stroke occurred in 2.1% of patients, whereas high-risk patients had 7% stroke incidence.
     3. Patients with dual/crescendo TIAs (2+ episodes of TIA symptoms within 1 week, increasing duration/frequency/severity of events) are higher risk and may warrant admission for expedited workup for ipsilateral carotid stenosis (ie. “unstable angina of the brain.”)
   • Imaging: Summary characteristics of DI modalities are summarized in Table 2 below.  In the ED setting, NCCT is not very sensitive to rule out small acute strokes, but can help rule out TIA mimics.  MRI (with DWI) is the preferred modality for acute small infarcts, but may not be readily accessible in ED settings.  NCCT and CTA may be useful to evaluate intra-cranial hemorrhages or symptomatic stenoses.  Risk of contrast-nephropathy is low with CTA, and worth the risk in cases of suspected stroke/bleed.
3. Disposition:  It may not be practical to complete a comprehensive TIA workup in the ED setting.  As such, creating an ED discharge protocol with expeditious follow-up for TIA patients is critical to reduce the risk of early post-TIA stroke (ideally within 48hrs).  Use of structured ED TIA diagnostic pathways have been shown to reduce time to imaging, ED LOS, admissions and cost-savings without sacrificing short term strokes or mortatlity.  Many of these pathways have been developed/validated in certified stroke centers, so generalizability to non-stroke ED centers may not be valid.  The Figure below outlines the key elements of a successful ED TIA pathway, and requires all elements to be functioning cooperatively with appropriate partners (eg. radiology, neurology outpt clinics).  

Table 4 provides suggestions for post ED discharge secondary prevention.  For patients with ABCD² >4pts (higher risk), they should be started on ASA 81mg PLUS clopidogrel 75mg daily (dual antiplatelet therapy; DAPT) until further f/u and consolidation to monotherapy.  For lower risk patients <4, one can consider ASA 81mg, clopidogrel 75mg daily OR dipyramidole 200mg BID.  For patients with new-onset Afib, initiation of oral anticoagulants are likely warranted (warfarin, DOACs).  If ED-available, use of DWI-MRI can be useful to identify micro-bleeds that may influence use of antithrombotic agents.  For patients with severe HTN, then starting/advancing anti-hypertensive therapy may be necessary to control future risk.  Similarly, severe hyperglycemia for diabetics (with high HbA1C levels) may warrant immediate intervention, and/or admission to hospital for risk factor control.  Initiation of statins for hyperlipidemia is less likely an urgent ED intervention, and could be deferred for outpt f/u discussion.

Simple counselling for behaviour/lifestyle modification should include the benefits of physical exercise, healthy diets (Mediterranean, DASH), limiting alcohol intake and smoking cessation.  

CLINICAL COMMENTARY:   TIAs comprise about 250K visits to US EDs, and can be a strong 

predictor of subsequent stroke.  The 90day risk of stroke can be as high as 17.8%, and almost

50% of these can occur within 2days.  Usual vascular risk factors can be applied for risk stratifying ED TIA patients. Unfortunately, Black Americans have 1.4x greater risk of completed early stroke than Caucasians, and men have a substantially lower rate of TIA/stroke than women (suggesting common inequities in ED vascular care).

Benefits of Recommendations:   This document provides guidance for key elements of ED management of TIA, including lab investigations, imaging options, risk stratification scores, and disposition decision-making.  Suggestions can be adopted/adapted into ED workplaces, and operationalized quite readily.

Harms/Adverse Effects of Recommendations:  It is not clear how to advance antithrombotic Rx in patients who are already on single-agents and are still experiencing TIA symptoms (treatment failures?).  

Facilitators of Uptake:

1. Useful tables for TIA vs mimics, imaging test performance, and risk stratification scores are included.  
2. A care pathway is included in the Figure, which can be adopted/adapted for ED TIA implementation.
3. Creation of regional TeleStroke programs can be beneficial in linking under-resourced/ rural ED physicians with regional expert stroke supports, especially for those patients presenting with acute strokes within thrombolytic windows.  These programs may also be leveraged for ED TIA risk stratification and expedited admission vs. follow-up care.

Barriers to Uptake:

1. Access to DWI-MRI or acute phase vascular imaging may be problematic in ED settings.  
2. Various ABCD scores have limitations for ED settings.  ABCD² does not account for “posterior” circulation symptoms (ataxia, hemianopsia, dysmetria), TIA mechanisms, recurrent/crescendo TIAs, nor presence of large vessel disease.  The latter three have higher risk of recurrent stroke or neurologic worsening.  Lack of access to carotid imaging or advanced brain imaging preclude the use of ABCD³ or ABCD³-I scores.
3. Extensive counselling/behaviour modification for lifestyle change may be inaccessible in most ED settings; ideally this would be available in outpt clinic settings and with primary care providers.
4. Under-served/racialized/rural patients may have specific social determinant barriers that need to be addressed in order to provide equitable and rapid ED TIA care 

Prior Guideline Recommendations/Relevant Evidence:  A comprehensive review by Perry et al (CMAJ 2022; doi: 10.1503/cmaj.220344) make similar recommendations for ED TIA work-up, risk stratification and disposition decisions.  Salient points are listed as follows:

1. TIA and minor stroke are less likely to be diagnosed in women, even though there are similar cerebral ischemia rates with men.
2. These authors (from Ottawa) recommend the use of the Canadian TIA Score, derived/validated to predict 7d stroke risk as Low (<1%), Moderate (1-5%) or High (>5%); available online free calculator at https://emottawablog.com/canadian-tia-score/, and listed on MedCalc.  Scoring tool summarized in figure below.
3. The Canadian Stroke Best Practices Guidelines call for early CT head for all patients with TIA/early stroke to assess stroke mimics; any abnormal findings can increase the subsequent 3mo stroke risk considerably.  They also report that patients with transient resolved symptoms may still have abnormal MRI findings (13.5%); it is not clear, however, what impact widespread MRI would have on management changes, subsequent strokes, ED over-crowding and resource costs (likely last two would be much higher).  
4. After disposition for expedited neuro/stroke clinic follow-up, decisions re: Holter monitoring, echocardiography and vascular imaging can be made later.
5. Secondary prevention with ASA 81mg (Low risk) or DAPT (Mod/High risk) is warranted for at least 21days until further outpt follow-up visits.  Give a loading dose in ED prior to discharge (ASA 160mg or clopidogrel 300-600mg).  Substituting ticagrelor for clopidogrel is also reasonable.  Patients with AFib on ECG may also warrant starting a DOAC (assuming no active bleeding on CT head); 66% risk reduction for future stroke.  HTN control (optimal target BP unknown?) is important, as uncontrolled HTN contributes 40% to stroke burden.  All other recommendations (statins, behaviour/lifestyle modification) are congruent with those presented in this AHA Statement.

Disclaimer (if any stated):  None reported.

Funding:   Not reported

Conflicts of Interested:  Reported; fully disclosed for writers/reviewers (pg e10).

Methodological Threats to Validity:  This Best Practice Statement (BPS) does not meet basic requirements for traditional clinical practice guidelines (eg. focused questions, robust evidence reviews/ quality assessments, formulation of recommendations).  Nonetheless, this document summarizes best current practices for ED TIA care.

*May also need to consider patient who live in under-serviced areas, or have transportation issues for outpatient f/u clinic visits that preclude a safe discharge.