How to Interpret CT/CTA for Acute Stroke in the Age of Endovascular Clot Retrieval

Transcription

1 How to Interpret CT/CTA for Acute Stroke in the Age of Endovascular Clot Retrieval Peter Howard MD FRCPC Disclosures No conflicts to disclose How to Interpret CT/CTA for Acute Stroke in the Age of Endovascular Clot Retrieval Part 1 Historical Review Why is this the Age of Endovascular Clot Retrieval? Part 2 How do I need to interpret CT/CTA for CT- Aspects score CTA major vessel occlusion CTA collaterals CTA access for thrombectomy Part 1: Human History A Stroke Interventionalists Perspective Stone Age simple tools Obvious limitations Stone Age : The PROACT ERA (1994-5) interarterial pro-urokinase versus placebo for proximal MCA occlusion 46 patients randomized Recanalization 58% versus 14% placebo (no TPA) Symptomatic ICH in 15.4% versus 7.1% placebo Legacy of Proact Showed interarterial therapy could recanalize MCA Concerns regarding intracranial hemorrhage Coincident with NINDS and ECASS which launched IV TPA Further trials of IA therapy to look for impact on patient outcome, versus IV TPA 1

2 Iron Age Improved tools Cumbersome/slow Effective enough? Iron Age The IMS III Era ( ) IMS III pragmatic trial allowing any approved recanalization device (most IA TPA), also MERCI clot retrieval device CT used for enrollment, CTA not required IMS-3 ( ) 656 patients randomized 2:1 to IV TPA plus interarterial thrombolysis (IA TPA or MERCI) versus IV TPA alone Endovascular therapy did not achieve superior clinical outcomes (functional independence at 3 months) Similar safety outcomes, symptomatic ICH 6.2 % IA, 5.9 % IV TPA alone Lessons Learned from IMS-3 Better identify target clot CTA not CT Need better IA equipment Merci Clot retriever and penumbra used in IMS -3 towards the end Need to intervene faster, minimize time to recanalization Five trials published in NEJM show improved functional outcome in patients treated with mechanical thrombectomy 2

3 Trials used stent retrievers MR. CLEAN Trial 500 patients with proximal intracranial arterial occlusion randomized to IA therapy versus standard care 89% treated with IV TPA prior to randomization Stent retrievers provide good recanalization and improved patient outcomes Recanalization 75% versus 33% controls 14% absolute increase in good outcomes NNT around 7 SICH 7.7% versus 6.4% controls New ischemic stroke in a different territory 5.6% Escape Trial 316 patients randomized Proximal occlusion anterior circulation M1 or ICA on CTA Small infarct core ASPECTS 6-10 on CT Moderate to good collaterals >50% filling MCA pial vessels on CTA Randomized to endovascular clot retrieval or standard care Target of vessel recanalization within 90 minutes of CT Most in intervention (73%) and control (79%) had IV TPA Escape Trial Results Trial stopped early due to efficacy Clot retrieval with stent retrievers improved patient outcomes Recanalization 72% versus 31% controls 24% absolute increase in good outcomes NNT around 4 9% absolute decrease in 90 day mortality SICH 3.6% versus 2.7% controls CT/CTA give four key pieces of information to choose endovascular clot retrieval vs IV TPA CT Aspects score Infarct core, potential benefit of procedure CTA location of vessel occlusion potential risks and benefits of procedure CTA collateral score viability of brain, potential benefit of procedure CTA vascular access tortuousity of CCA and ICA, risks of procedure likelihood of success 3

4 CT Aspects score Infarct core, potential benefit of procedure Aspects should be 6 or higher to consider clot retrieval Lower Aspects scores, higher risks of reperfusing dead brain, lower potential for good functional outcome CTA location of vessel occlusion Best targets for clot retrieval supraclinoid ICA M1 segment of MCA Others to consider proximal M2 with high NIHSS basilar Smaller branches = IV TPA more effective, endovascular more difficult Location of occlusion and risk of spreading emboli outside affected vascular territory CTA collateral score Poor collaterals <50% pial MCA branches likely large infarct, less likely good functional outcome Good collaterals > 50% pial MCA branches good candidate for clot retrieval hope for good functional outcome with recanalization CTA vascular access Highly tortuous proximal CCA/ICA difficulty placing guide catheter longer procedure times higher dissection risk higher risk distal emboli Proximal ICA occlusion/high grade stenosis/dissection difficulty placing guide catheter longer procedure times higher dissection risk may require stent/antiplatelets higher risk distal emboli 2015 Canadian Stroke Best Practice recommendations endovascular therapy inclusion criteria on imaging: A small-to-moderate ischemic core (with ASPECTS score of 6 or higher). For patients with ASPECTS score less than 6, the decision to treat should be based on the potential benefits and risks of the therapy, made by a physician with stroke expertise in consultation with the patient and/or family/substitute decision-makers. Intracranial artery occlusion in the anterior circulation, including proximal large vessel occlusions in the distal ICA, MCA/ACA and immediate branches. For patients with basilar artery occlusions, the decision to treat with endovascular therapy should be based on the potential benefits and risks of the therapy, made by a physician with stroke expertise in consultation with the patient and/or decision-makers. Either of: Moderate-to-good collateral circulation demonstrated using multiphase or dynamic CTA. OR If CT perfusion imaging is used, the specific imaging characteristics to define perfusion mismatch and a small-to-moderate ischemic core should be adapted based on available CT scanner and software technology. Case 1 55 year old female Left hemiplegia for 2 hours NIH Stroke Score of 18 Prior mitral valve replacement, atrial fibrillation On Warfarin, INR of 2.7 4

5 Case 1 Case 1 Unenhanced CT Coronal CTA Transit time Blood Flow Blood Volume Further Management The most appropriate treatment now is: A. IV TPA B. IA TPA C. Mechanical thrombolysis D. ASA 81 mg and Plavix 75 mg E. All of the above Further Management The most appropriate treatment now is: A. IV TPA B. IA TPA C. Mechanical thrombolysis D. ASA 81 mg and Plavix 75 mg E. All of the above Mechanical Thrombolysis with Stent-Retriever Take Home Messages 1. Exciting new era, endovascular clot retrieval improves functional outcomes and reduces mortality in stroke 2. CT with CTA is key to identify patients who might benefit 3. Time is brain; no delay for CT WITH CTA 5

6 The End 6