Sharp Increase in US Stroke Thrombectomy After Major Trials

March 03, 2017

HOUSTON, Texas — Use of endovascular treatment for stroke in the United States has risen sharply since the randomized trials showing its efficacy were published in early 2015, new data show.

The study was presented at the International Stroke Conference (ISC) 2017. Another presentation at the same meeting reported that outcomes were still good with endovascular treatment in stroke patients who did not meet top-tier evidence criteria, and the authors suggest that thrombectomy is not withheld from patients who do not meet the strict inclusion criteria of the randomized trials.

In a presentation of latest trends in endovascular thrombectomy in acute ischemic stroke from the American Heart Association/American Stroke Association "Get With The Guidelines" (GWTG) stroke registry, Eric Smith, MD, University of Calgary, Alberta, Canada, said the figures showed a dramatic increase in the number of these procedures being conducted, related to both new hospitals providing endovascular therapy and higher case volumes at hospitals already delivering such care.

The GWTG registry has collected data on 2,403,635 stroke patients seen at 2203 hospitals since 2003.

"New data show that right away within a year of the publication of the major studies showing benefit of endovascular therapy in stroke, about one third more hospitals in the GWTG registry started providing endovascular thrombectomy, and of those hospitals already proving such therapy the case volume about doubled," Dr Smith noted.

Commenting on the stats for Medscape Medical News, chair of the ISC session at which the analysis was presented, Valeria Caso, MD, University of Perugia, Italy, said, "These are wonderful figures. It means data from randomized trials are being translated into clinical practice. The science is being applied appropriately."

Dr Smith reported that mean annualized average case volumes at endovascular capable hospitals rose from 25.0 patients in the fourth quarter of 2014 to 52.7 patients in the second quarter of 2016.

And latest figures show that 27.3% of potentially eligible patients were being treated with thrombectomy at these hospitals at the end of 2016, representing 7.5% of all patients with ischemic stroke admitted to endovascular capable hospitals.

Among all patients at all hospitals (those providing and not providing endovascular therapy), the proportion of potentially eligible patients treated was 15.1% at the end of 2016, representing 3.5% of all ischemic strokes.

"The number of patients receiving mechanical thrombectomy has increased from around 2% of all ischemic strokes to over 3% in less than 2 years since these trials were published," Dr Smith told Medscape Medical News. "We estimate that perhaps about 10% of all ischemic stroke patients may be eligible for such treatment so we still have a long way to go, but it is very encouraging to see such a fast early improvement after publication of the data."

He added: "This shows the value of doing randomized trials powered to show patient outcomes and shows how this evidence has led to us reorganizing stroke systems so quickly to maximize use of this therapy in as many patients as possible."

Dr Smith noted, however, that the centers capable of endovascular therapy were not equally distributed throughout the country.

"I do get a sense that there is some maldistribution of comprehensive stroke centers and the specialists able to do these procedures across the country, and this is going to be one of the focuses in future analysis of our data," he said. "We need to train more interventionalists and ensure they are distributed geographically to make sure all patients ideally can get to a comprehensive stroke center offering this service within 30 to 60 minutes."

Top-Tier Criteria

Data on patients undergoing thrombectomy who did not meet top-tier criteria came from a separate observational study of 583 consecutive patients with acute ischemic stroke and emergent large-vessel occlusions who underwent mechanical thrombectomy at six high-volume endovascular centers.

Results showed that 40% of these patients did not fulfill top-tier evidence criteria for the procedure but still had high rates of good clinical outcome and low complication rates.

Patients meeting the criteria tended to have higher functional independence rates at 3 months (47% vs 39%; P = .055), while the rates of symptomatic intracerebral hemorrhage were similar (9%) in both groups.

But in multivariable logistic regression models, adherence to top-tier criteria was not independently related to any safety or efficacy outcome after adjustment for potential confounders.

The study is published in the March issue of the Journal of NeuroInterventional Surgery.

Presenting the study as a moderated poster at the ISC meeting, Nitin Goyal, MD, University of Tennessee Health Science Center, Memphis, noted that the most common reason for not meeting top-tier guidelines was the location of occlusions (distal anterior circulation or posterior circulation occlusions).

"Our study indicates that thrombectomy can be performed safely and effectively in this group. Although unadjusted mortality rates were higher in this subgroup, after adjusting for potential confounders, there was no association between adherence to top-tier guidelines for location of occlusion and the likelihood of 3-month mortality in multivariable analyses."

He added: "The higher mortality rates for the subgroup of patients not meeting top-tier evidence in our cohort can be largely explained by the inclusion of patients with basilar artery occlusions. Despite the higher mortality of basilar artery occlusions after thrombectomy, these patients should be offered timely intervention, considering the extremely poor natural history of the untreated disease, with mortality rates up to 80%."

Dr Goyal said another common reason for not meeting top-tier evidence was delayed treatment window (symptom onset to groin puncture time of more than 6 hours).

"The adjusted analysis of our data suggests that thrombectomy can be performed in this group with equal effectiveness, and at no increased cost of symptomatic intracranial hemorrhage rates and mortality when compared with the group meeting top-tier criteria for treatment time window," he said. "Our preliminary observations are partly supported by the findings of the ESCAPE trial, in which 49 patients underwent randomization at 6 or more hours after stroke onset, with the direction of effect in this subgroup favoring MT [mechanical thrombectomy] for mRS [modified Rankin Scale score] of 0 to 2 at 90 days."

Senior author, Adam Arthur, MD, professor of neurosurgery at the University of Tennessee, stated: "Although findings from the 5 successful thrombectomy trials have significantly improved our knowledge of the benefit of mechanical thrombectomy, we argue that further calls to stifle the provision of this treatment outside clinical trials in patients not meeting top-tier evidence may be unjustified, given the grim natural history of severe strokes with persisting occlusions.

"We feel that postmarket registries rather than future randomized controlled trials may be more feasible in certain patient subgroups for examining the value of thrombectomy in patients with NIHSS [National Institutes of Health Stroke Scale] scores under 6, ASPECT [Alberta Stroke Program Early CT] score less than 6, prestroke mRS score more than 1, occlusion of the M2 or M3 portion of the middle cerebral artery, anterior cerebral arteries, vertebral arteries, basilar arteries, or posterior cerebral arteries and treatment beyond 6 hours from symptom onset for patients with acute ischemic stroke who have causative occlusion of the internal carotid artery or proximal middle cerebral artery (M1)," he added.

International Stroke Conference (ISC) 2017. Abstracts LB14 and TMP6. Presented February 23, 2017.

J Neurointervent Surg. 2017;9:225-228. Abstract

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