Advanced Endovascular Therapy for Acute Stroke: The Evidence Is In

A longtime hypothesis has now been confirmed with Level I, Class A evidence: Endovascular therapy can be highly beneficial in patients with acute ischemic stroke compared with IV t-PA alone.

That’s the resounding message out of this year’s International Stroke Conference, where results of five randomized clinical trials — MR CLEAN, EXTEND-IA, ESCAPE, SWIFT PRIME and REVASCAT — were presented. The studies consistently showed that, compared with IV t-PA alone, endovascular therapy within six to eight hours after stroke onset:

• Yielded superior recanalization rates
• Produced higher rates of functional independence at 90 days
• Was safe, with no significant increase in symptomatic brain hemorrhage or mortality

‘Turning a historic corner’ in acute stroke

The five studies are now published in the New England Journal of Medicine and represent the “turning of a historic corner” in acute stroke therapy, according to a statement from the National Institute of Neurological Disorders and Stroke.

The studies compared interventional therapy using new-generation mechanical thrombectomy devices (“stent retrievers” such as Medtronic’s Solitaire™ FR and Stryker’s Trevo®) vs. best medical management for acute ischemic stroke caused by large vessel occlusion, which represents a large subset of ischemic stroke cases.

Benefits from better stent-retriever devices

The new studies put to rest lingering uncertainties about the efficacy of endovascular stroke therapy that arose from results of three trials released in 2013 that showed no advantage over IV t-PA alone. One of the key reasons for the shift in results since then appears to be related to the introduction of stent-retriever technology.

The new-generation catheter-based devices used in the latest studies deploy a metal mesh within the clot, in contrast to earlier devices that acquired control of the clot proximally or distally. The moment the mesh is deployed, a channel is opened to permit blood flow to starved brain tissue. The mesh expands to become one with the clot, allowing clot and mesh to be retrieved as a unit. The result is faster, more complete recanalization.

New-generation stent retrievers deploy a metal mesh within the clot, allowing clot and mesh to be extracted as a unit.

Progress in patient selection too

Another reason for the improvements in endovascular therapy outcomes is the use of better neuroimaging criteria for selection of endovascular therapy candidates.

Criteria in the latest studies are similar to those in the “hyperacute MRI protocol” used for the past several years by Cleveland Clinic’s Cerebrovascular Center. “This protocol promotes the use of advanced MRI techniques (in conjunction with CT or CT angiography) to enable more precise determination of tissue viability and occlusion impact before acute stroke intervention,” says Cerebrovascular Center specialist Gabor Toth, MD. This has allowed Cleveland Clinic stroke specialists to better select patients within traditional time windows for intra-arterial stroke therapy and to extend the window for acute interventional treatment.

Left: Noncontrast brain CT without evidence of an acute infarct despite left middle cerebral artery (MCA) syndrome on examination. Right: Axial diffusion trace MRI in the same patient within 20 minutes, showing infarction of the entire left MCA territory.

The Cerebrovascular Center’s positive outcomes with this protocol have included the following, as reported recently in Stroke:

• Significant increase in the percentage of patients achieving a good clinical outcome (modified Rankin Scale score ≤ 2) at 30 days
• Significant reduction in mortality
• Achievement of the above two outcomes despite a 50 percent reduction in patients receiving endovascular therapy
• No reduction in average time to initiation of endovascular therapy

A new era in care — with new challenges

With the latest clinical trial data, a new era in endovascular stroke therapy is at hand — one where many more acute stroke patients can be saved from death or severe, lifelong disability.

Yet this new era has major implications for the delivery of acute stroke care. “Effective use of modern endovascular therapy devices demands that systems of care be in place to rapidly identify appropriate patients and swiftly get them to the neuroangiography suite for intervention,” says Dr. Toth.

To that end, Cleveland Clinic’s Cerebrovascular Center uses new-generation endovascular therapy devices on a daily basis in neuroangiography suites on Cleveland Clinic’s main campus as well as in regional hospitals on Cleveland’s east and west sides.

Their expert use of these technologies is enhanced by the following:

• Deep experience with an acute MRI protocol refined over more than five years of use to ensure patient selection that optimizes patient benefits while minimizing harm to inappropriate candidates
• Telestroke offerings and workflow efficiencies to streamline ED and neuroimaging throughput, in full recognition that time is brain
• Use of a mobile stroke treatment unit, one of only two such units operating in the U.S., to enable evaluation and treatment of stroke patients at the site of stroke onset and to accelerate initiation of management

“We are committed to collaborating with colleagues in the community to offer these advantages to reduce the burden of stroke disability in our shared patient population,” says Dr. Toth.