8.1 / IAGS 2019
Session 8: Emerging Therapies Session 1
Expanding the Frontiers of Acute Stroke Intervention: Viability Imaging and “Facilitating” Devices
Problem Presenter: Gyula Gal, MD
Statement of the problem or issue
Acute ischemic stroke (AIS) is a leading cause of death and disability, especially in older populations. Standard care for AIS consists of routine support, aggressive rehabilitation, and immediate administration of intravenous thrombolysis (IVT) if patients arrive within 6 hours of symptom onset. Beyond 6 hours, infarcted brain tissue is not recoverable. Current care standards improve outcomes, but many patients succumb to their strokes and many others are left with profound disability.
Gaps in knowledge
The effectiveness of intra-arterial thrombectomy (IAT) as an adjunct to medical therapies has only recently been studied in adequately powered randomized trials. New devices for thrombus management have been developed, but their effectiveness is uncertain. Options for care of AIS patients with >6 hours of symptoms are limited.
Possible solutions and future directions
The MR CLEAN randomized clinical trial (Berhemer, et al. NEJM 2015;372:11-20) involved AIS patients with ≤6 hours of symptoms who received IVT or IAT (with or without IVT; the majority had concomitant IVT). This trial showed definitively that use of IAT was associated with better recovery of function than standard care. Based on this trial and other works, interest in IAT has increased. The DAWN randomized clinical trial (Nogueira RG, et al, NEJM 2018;378:11-21) studied AIS patients with >6 hours but <24 hours of symptoms. All patients underwent brain CT or MRI imaging, and patients with more severe clinical disability than expected based on the volume of infarcted brain were randomized to standard care or IAT. The hypothesis was that some brain tissue was ischemic but still viable in these patients, and could be recovered with aggressive treatment. Patients meeting criteria were randomized to standard care or IAT. This trial found superior recovery with IAT for those patients with a “mismatch” between deficit and infarct size. Based on this study and other works, neuro-interventionalists are beginning to use CT or MRI brain imaging to identify patients who may benefit from IAT despite having symptoms for >6 hours.
Several technologies have been developed to accomplish IAT:
Stentriever. This device uses an 8 Fr occluder balloon positioned at the internal carotid artery (ICA) or the vertebral artery (VA) and an expandable wire mesh to extract thrombus from intra-cranial arterial segments. The mesh is placed by advancing a micro-catheter over a guidewire through the thrombus. The guidewire is removed and replaced by a retrieval mesh, which is expanded within the thrombus. This partially relieves the occlusion and allows initial relief of acute ischemia. The occluder balloon is then inflated and the retrieval mesh with thrombus is withdrawn while continuously aspirating through the occluder balloon.
Proximal aspiration. A 6 Fr long sheath is inserted to the ICA or VA. A 6 Fr large-bore soft-tipped aspiration catheter is mounted over a micro-catheter. The micro-catheter is advanced to the thrombus over a guidewire. The aspiration catheter is advanced over the micro-catheter and used to aspirate thrombus.
Combined stentriever and proximal aspiration system. This system aims to capture the benefits of both the stentriever and proximal aspiration methods. An aspiration catheter is advanced to the thrombus as above, and the micro-catheter is advanced through the thrombus. A stentriever device is advanced through the micro-catheter and expanded in the thrombus. The stentriever with thrombus is withdrawn during simultaneous aspiration.
These systems are evolving but they’re having a positive impact on stroke management. The number of neuro-interventionalists worldwide is increasing. Early intervention is still essential, but routine brain imaging with assessment of viability/deficit mismatch is changing the approach to care for AIS patients with >6 hours of symptoms. Comparative studies to assess the relative merits of the various devices, and determine when to select one over another, are needed.