Which Is the Best Technique for Stroke Thrombectomy?

February 23, 2022

While the routine use of endovascular thrombectomy has revolutionized the treatment of large vessel occlusion ischemic stroke in recent years, a new a study is addressing whether individual approaches to the procedure have an effect on outcomes.

Preliminary results of the ASSIST registry have shown some differences in time to reperfusion and early response rate between the various approaches, but 90-day neurological outcomes looked similar with all strategies.

These interim results from the ASSIST study were presented at the International Stroke Conference (ISC), held in New Orleans and online.

The study compared three different thrombectomy techniques to remove the occluding clot: use of a classic stent retriever, direct aspiration with an aspiration catheter, or a combination approach of a stent retriever together with an aspiration catheter.

"This is a global registry study of three different approaches — all using Stryker products — as the first step in stroke thrombectomy," said David Liebeskind, MD, professor of neurology at University of California, Los Angeles, who presented the study at the ISC meeting. "We are comparing different ways of opening the plumbing based on each center's preferred technique up front."

Overall, there were some small technical differences between the approaches, he said. "For example, there was a faster degree of reperfusion with the classic stent retriever, and the combination technique took longer as it is more complicated. But in terms of neurological outcomes at 90 days, we did not see any differences across the board."

Liebeskind noted, however, that the study is not yet complete, with more data to come on use of large bore catheters, site of occlusion, and other patient factors such as the size of the stroke.

"These additional results are planned to be presented at the European Stroke Organisation Conference in May and preliminary analyses suggest that there may be some interesting findings," he told theheart.org | Medscape Cardiology.

Lead author of the study, Rishi Gupta, MD, co-director of the Neurosciences Institute at Wellstar Health System, Marietta, Georgia, explained that the study was performed to identify whether one of the several currently employed operator techniques for thrombectomy in acute stroke may deliver more effective and efficient results.

He noted that there are currently operator and institutional biases based on experience, training, and comfort as to which technique is employed. "All three techniques evaluated in this study have some levels of evidence in the literature with success rates that appear similar. ASSIST selected sites with experience using one of these three techniques as their preferred strategy. This is important because the operators were proficient with this technique."

The ASSIST registry has so far included 1300 patients undergoing thrombectomy from 71 sites across North America, Europe, and Asia.

"The number of patients, quality of data, and site selection of centers who perform one of the three techniques primarily allowed for a type of cluster analysis. This is the closest we will be able to come to identifying if differences exist amongst techniques particularly with a core lab independent adjudication," Gupta said.

Results of the study so far show that the classic stent retriever had the highest rates of reperfusion with the first pass.

The primary procedural outcome was reperfusion defined as eTICI 2c flow or greater on first pass. This was achieved in 47.6% of patients who underwent thrombectomy with the classic stent retriever, 45.5% of those in the combination group, and 39.4% in the direct aspiration group, a nonsignificant difference (P = .230).

A secondary outcome of TIMI 3 flow on first pass occurred in 34.4% in the classic stent retriever group, 24.1% in the combination group, and 20.3% in the direct aspiration group (P = .013).

And TICI 2c or greater flow at the end of the procedure was reported in 70.8% in the classic stent retriever group, 66.0% in the combination group, and 68.4% of patients in the direct aspiration group (P = .012).

The study also found that direct aspiration required significantly more passes to remove the clot.

Another key finding was that use of a balloon-guided catheter lengthened the procedure time without improving the quality of reperfusion. "This is counter to what has been thought to be of benefit in the literature," Gupta said.

But all three arms fared well with overall 90-day neurological outcomes and reperfusion grade on final angiography, he reported.

The primary clinical endpoint was 90-day good functional outcome defined as modified Rankin Scale (mRS) score of 0 to 2, which was achieved in 58.4% in the classic stent retriever group, 52.3% in the combination group, and 59.3% in the direct aspiration group (P = .195).

A good early response, defined as a drop of 10 points or more from baseline in the National Institutes of Health Stroke Scale (NIHSS) score or an NIHSS of 0 or 1, assessed at day 5 to 7 postprocedure, occurred in 64.6% of the classic stent retriever group, 55.2% in the combination group, and 53.4% in the direct aspiration group (P = .072).

"The main clinical significance from this study so far is that balloon guides may not improve reperfusion grade/success and the first pass effect may not be as important as final reperfusion grade as long as this is achieved efficiently," Gupta commented. "But there is still quite a bit of analysis left with 200 additional patients in whom a larger bore aspiration catheter was used."

Asked if there was enough information to recommend one approach over another, Gupta said: "As we unlock the final data, there is hope that this can be answered more thoroughly. Currently all three techniques achieved good technical and clinical results. Analysis of costs and changing techniques is ongoing, which we believe will provide clinicians a more thorough perspective on this question."

He added: "This is a critical study to help hopefully identify if certain techniques may not be the best strategy for patients. When we add in costs and time factors, it will allow operators to make important decisions of how best to deliver timely, cost-effective, efficient reperfusion for their patients."

"Importance of Registry Data"

Commenting on the study for theheart.org | Medscape Cardiology, Mitchell Elkind, MD, immediate past president of the American Heart Association/American Stroke Association and professor of neurology at Columbia University, New York City, said: "This study illustrates the kind of important information we can get from comparative effectiveness studies using registry data. The details of how individual interventionalists approach thrombectomy is the kind of question that may be hard to study in a fully randomized, controlled trial since it may require quick adaptations on the part of the treating team. These kinds of changes may not lend themselves to highly protocolized care."

Elkind added: "The study provides evidence that use of a stent retriever as first approach may provide optimal reperfusion. Further confirmatory studies, and comparison against other approaches not included in this registry, will help to further refine thrombectomy in the future."

Also commenting on the study, Patrick Lyden, MD, professor of physiology and neuroscience and neurology, University of Southern California, Los Angeles, said: "The registry is important as there remains some doubt about consistent application of thrombectomy across new stroke centers. That is, as technology diffuses from specialized research centers into daily, typical clinical practice, there may be some diminution of benefit and perhaps accumulation of greater risks. The data here is reassuring: Outcomes in the real world match those seen in the pivotal research trials."

The authors noted some differences among the various thrombectomy techniques, but these differences are minor and not clinically important, Lyden added. "The bottom-line message for me is that thrombectomy is useful for a small number of stroke patients, those presenting with qualifying large-vessel occlusion, and can be done well in a variety of settings."

The ASSIST study is sponsored by Stryker Neurovascular. Liebeskind reported acting as a consultant as imaging core lab for Cerenovus, Genentech, Medtronic, Rapid Medical, and Stryker.

International Stroke Conference 2022: Abstract LBS23. Presented February 11, 2022.

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