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How Can We Use Advanced Neuroimaging in the ED to Optimize Treatment Options for Acute Stroke Patients?.

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  1. How Can We Use Advanced Neuroimaging in the ED to Optimize Treatment Options for Acute Stroke Patients?

  2. Andrew Asimos, MDDirector of Emergency Stroke CareCarolinas Medical CenterCharlotte, NCAdjunct Associate Professor Department of Emergency MedicineUniversity of North Carolina School of Medicine at Chapel Hill

  3. Attending PhysicianEmergency MedicineCarolinas Medical CenterDepartment of Emergency MedicineCharlotte, NC

  4. Disclosure • None related to the content of this presentation

  5. Session Objectives • Acknowledge latest guidelines and systematic review related to advanced neuroimaging • Review important unenhanced CT concepts • Review CTA/CTP concepts and supporting data • Overview of latest MRI data

  6. Clinical Questions What is the goal of initial neuroimaging for presumed acute stroke patients? How can CTP/CTA or MRI/MRA be utilized To optimize the use of IV tPA and the triage of ED stroke patients for advanced IR therapeutics? To detect the site of the vascular occlusion, and CTP (DWI/PWI) the size of the ischemic penumbra and the infarct core? To maximize the potential benefit and minimize risk when using IV tPA in ED stroke patients?

  7. Clinical Questions What are perfusion scans, what do they demonstrate, and how are they interpreted? What software or technology is necessary for advanced neuroimaging? How can these capabilities be developed at my hospital? What usage of these advanced diagnostics is the standard of care in 2007?

  8. Case:Patient presenting within 3 hour window • 50 yo male • CT less than 2 hours within symptom onset • Awake, alert, dysarthric • Fixed right sided gaze • Left sided weakness

  9. Case:Patient presenting within 3 hour window

  10. Case:Patient presenting within 3 hour window Initial BF BV TTP

  11. Case:“Wake up” Stroke 0735 at outside hospital

  12. Case: “Wake up” Stroke

  13. Case: “Wake up” Stroke 1030 at stroke center

  14. Impact of Neuroimaging on Decision Making • Both art and science to treatment decision making for acute stroke • Lots of non-imaging related factors increase SICH risk after treatment with tPA • Average EM physician cannot keep up with advances in neuroradiologic technology and literature regarding its impact on decision making • Guidelines cannot keep up

  15. Essential Imaging Questions • Is there hemorrhage? • Are findings consistent with acute ischemic stroke? • Can this imaging modality’s results add to my risk/benefit analysis? • Is there large vessel occlusion? • Is there “irreversibly” infarcted core? • Is there “salvageable” penumbra? • Are other findings present that should be considered • Microbleeds • Leukoaraiosis

  16. The Four P’s of Acute Stroke Imaging Rowley HA et al. Am J Neuroradiol 2001;22:599-601.

  17. 2007 Imaging Guidelines Adams HP et al. Stroke 2007;38:1655-1711.

  18. Systematic Review of DWI/PWI Mismatch and Thrombolysis in Acute Stroke

  19. Class I Recommendations • Imaging of the brain is recommended before initiating any specific therapy to treat acute ischemic stroke • In most instances, CT will provide the information to make decisions about emergency management • The brain imaging study should be interpreted by a physician with expertise in reading CT or MRI studies of the brain • Some findings on CT, including the presence of a dense artery sign, are associated with poor outcomes after stroke • Multimodal CT and MRI may provide additional information that will improve diagnosis of ischemic stroke Adams HP et al. Stroke 2007;38:1655-1711.

  20. Unenhanced CT:Beyond Hemorrhage

  21. Unenhanced CT:HDMCA Sign • Overall poor prognosis if HDMCA sign on CT • Limited data suggest IV-t-PA ineffective in treating acute stroke in the setting of HDMCA sign Somford DM et al. Radiology 2002;223:667–671. Barber PA et al. Stroke 2001;32:84–88.

  22. From the 2007 Guidelines “Several studies have suggested that perfusion CT may be able to differentiate thresholds of reversible and irreversible ischemia and thus identify the ischemic penumbra.114,115” Klotz E et al. Eur J Radiol 1999; 30: 170–184. Wintermark M et al. Ann Neurol 2002; 51: 417–432.

  23. Class II Recommendations • Data are insufficient to state that, with the exception of hemorrhage, any specific CT finding (including evidence of ischemia affecting more than one third of a cerebral hemisphere) should preclude treatment with rtPA within 3 hours of onset of stroke • Vascular imaging is necessary as a preliminary step for intra-arterial administration of pharmacological agents, surgical procedures, or endovascular interventions Adams HP et al. Stroke 2007;38:1655-1711.

  24. Unenhanced CT:ASPECTS System

  25. ASPECTS Example

  26. ASPECTS Score andFunctional Outcome Weir NU et al. Neurology 2006;67(3):516-8.

  27. Usefulness of ASPECTS Score at Predicting Outcome of Individual Patients Weir NU et al. Neurology 2006;67(3):516-8.

  28. ASPECTS Score Applied to tPA Treated Patients • Used ECASS II Database • 788 baseline CT scans • 6 hour treatment window Dzialowski I et al. Stroke 2006:37(4):973-8.

  29. 90 Day Outcome by ASPECTS > 7 Dzialowski I et al. Stroke 2006:37(4):973-8.

  30. Class III Recommendations • Emergency treatment of stroke should not be delayed in order to obtain multimodal imaging studies • Vascular imaging should not delay treatment of patients whose symptoms started <3 hours ago and who have acute ischemic stroke Adams HP et al. Stroke 2007;38:1655-1711.

  31. Therapeutic Window • Time from ictus used for theoretical and practical reasons • Increasingly will rely on imaging studies to determine tissue salvageability and clot burden

  32. Good Collateral Flow will Buy you Some Time and Brain

  33. Advanced CT Imaging for Acute Stroke:CTP versus MRI Muir KW et al. Lancet Neurology 2006; 5:755-768

  34. MRI/MRA in Acute MCA Ischemic Stroke Treated Successfully with t-PA

  35. MRI/MRA in Acute MCA Ischemic Stroke Not Treated with t-PA

  36. CT Perfusion Terminology Blood Flow Blood Volume Mean Transit Time or Time to Peak

  37. Definitions

  38. Changes in Cerebral Vascular Physiology with Worsening Circulatory Impairment

  39. Relationship between CBV, CBF, and MTT Blood Flow Blood Volume Mean Transit Time or Time to Peak MTT= CBV/CBF

  40. Example of the Progression of Advanced Images

  41. Pure Penumbra Parsons MW et al. Neurology 2007;68(10):730-6.

  42. Core Infarct and Penumbra Parsons MW et al. Neurology 2007;68(10):730-6.

  43. Largely Completed Infarction Parsons MW et al. Neurology 2007;68(10):730-6.

  44. Are CTP Techniques Ready for Prime Time? • CTP more accurate than unenhanced CT for detecting stroke and determining the extent of stroke • Possible to distinguish penumbra from infarcted tissue • Correlation between PCT/CTA and MRI is excellent • Already used in DIAS and DEDAS Wintermark M et al. Am J Neuroradiol 2005;26(1):104-12. Wintermark M et al. Stroke 2006;37:979-985. Wintermark M et al. Neurology 2007;68(9):694-697.

  45. Important Remaining CTP Questions • What is the interrater reliability of visual estimation of lesion volumes? • Is that variability clinically important? • Can computerization automate measurement of absolute perfusion thresholds and lesion volume in a clinically meaningful way? • Will the current perfusion thresholds for penumbra and infarct be maintained with rigorous future testing?

  46. Relative MTT is the Best CTP Parameter for Identifying Penumbra Wintermark M et al. Stroke 2006;37:979-985

  47. Absolute CBV is the Best CTP Parameter for Identifying Infarct Wintermark M et al. Stroke 2006;37:979-985

  48. DEFUSE Study • Prospective pilot study (n=74) • Patients treated with IV tPA 3-6 hours after symptom onset • Goal to identify MRI patterns that predict the clinical response to early reperfusion Albers GW et al. Ann Neurol 2006:60(5):508-17.

  49. Key Results of theDEFUSE STUDY • Target Mismatch pattern • Identifies patients who appear to benefit substantially from early reperfusion • Malignant MRI pattern • Predicts severe ICH following reperfusion • Small DWI and PWI lesions • Associated with favorable outcomes Albers GW et al. Ann Neurol 2006:60(5):508-17.

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