Timing, testing, and standardization of endovascular therapy

The Society of Vascular & Interventional Neurology (SVIN) roundtable meeting concerning endovascular therapy highlights the rapid advances in technologic approaches to revascularization in acute stroke patients. Although the new technology is exciting, the road to scientifically proven advances that improve outcomes for patients will depend upon minimizing the time to revascularization, scientific testing of the technology in clinical trials, and standardization of training and delivery of endovascular therapy.

One consistent theme from the single-arm clinical trials of endovascular therapy is that the clinical outcome after revascularization is highly dependent upon the time from stroke onset to revascularization. The IMS (Interventional Management of Stroke) I and II Trials,¹ the Penumbra Trial,² and the French Recanalyze Study³ demonstrated a strong relationship between time to revascularization and a good functional outcome, as measured by a modified Rankin Scale score of 0–2 at 3 months. In the IMS I and II pilot trials, revascularization beyond 6 hours resulted in outcomes similar to those for patients without revascularization. The discrepancy between increasingly higher rates of recanalization with the new endovascular devices and relatively disappointing clinical outcomes at 90 days, in comparison with findings in the NINDS tPA (National Institute of Neurological Disorders and Stroke tissue plasminogen activator) trial and PROACT (Prolyse in Acute Cerebral Thromboembolism) II trial,^2,4,–,7 also reflects the importance of time to revascularization. The most recent technologic advance, self-expanding retrievable stents, temporarily restores blood flow and then removes the occluding thrombus. It is not surprising that a number of companies are pursuing this particular technology, which appears to represent an advance over previous devices cleared by the US Food and Drug Administration for thrombus removal in acute stroke. Using imaging to determine a physiologic time window to perform endovascular therapy is under study, but imaging is most likely to be helpful as a guide to futility and the decision not to proceed with endovascular treatment.

Testing and comparison of devices in animals and humans must focus not only on revascularization and safety but clinical outcomes as compared to standard therapy. Eventually, these devices must be tested in randomized trials comparing endovascular therapy to IV tPA within 4 1/2 hours and against standard therapy beyond 4 1/2 hours. Long-term acceptance, use, and reimbursement for these devices in clinical practice must be based upon demonstration of clinical effectiveness, not just revascularization. In addition, clinical and angiographic outcomes in pilot studies of these devices must be standardized if we are to truly compare devices. All trials should use the thrombolysis in cerebral ischemia (TICI) designation^8,9 as well as recanalization of the primary occluded vessels. The use of imaging to select patients should also be noted and described, because the included populations of patients may vary substantially between trials. Finally, assessment of devices must recognize that the quality of data varies greatly by source (from highest to lowest): randomized controlled trials against standard therapy > single-arm trials > registries > case series. The latter 2 categories are extremely susceptible to reporting bias and less reliable outcome measurements. Thus, it is not surprising that the clinical outcomes in registries and case series as described in the roundtable articles are often much better than outcomes in clinical trials.

Finally, we are still in the infancy of endovascular therapy for acute stroke. As the technology begins to be better defined, the stroke community will need to define and standardize the overall training of stroke endovascular specialists, training and experience with given devices, and the angiographic procedure itself, including sedation and anesthesia. Recent reports indicate that conscious sedation, rather than routine general anesthesia, is associated with improved outcomes.^10,11 This requires further study. With regard to standardization, the field of cardiology is far ahead of us in that current national American Heart Association guidelines speak to all parts of the pre- and post-angiographic procedure and recommend criteria for ongoing experience and volume of cases, both by operator and by center. As our field moves forward, improved patient outcomes—not reimbursement, turf issues, or technology per se—should be the principle that guides our journey.

• Received July 10, 2011.
• Accepted August 17, 2011.

• Copyright © 2012 by AAN Enterprises, Inc.