Hospital Transfer Linked to Worse Stroke Thrombectomy Outcome

March 07, 2017

HOUSTON — New data from a large registry study of mechanical thrombectomy for acute ischemic stroke suggest that the procedure can safely be performed in the real world with timing and clinical outcomes similar to those observed in the key randomized trials.

But results from the STRATIS registry also suggest that patients who are first taken to a primary stroke center and then transferred to the comprehensive center have significant delays to treatment and a significantly lower chance of good outcome.

"Strategies to facilitate more rapid identification of ischemic stroke patients with large vessel occlusions and direct routing of these patients to endovascular centers may help to improve outcomes." Michael Froehler, MD, Vanderbilt University Medical Center, Nashville, Tennessee, concluded.

The results were presented here at the International Stroke Conference (ISC) 2017.

He reported another analysis of the STRATIS data suggesting that if all patients within 20 miles of a comprehensive center had been taken directly there instead of first going to a nearer primary stroke center, this would delay tissue plasminogen activator (tPA) treatment by just 2 minutes but reduce time to endovascular therapy by 90 minutes.

Dr Froehler told Medscape Medical News: "This is just one hypothetical preliminary analysis with many assumptions made, but I think it is enough to show us that there probably is a subgroup of patients who will benefit from going straight to the endovascular center rather than going to nearest primary stroke hospital. I don't think we yet know exactly who these patients are and I also think those patients will differ based on different geographical regions."

Commenting on this data for Medscape Medical News, Eric Smith, MD, University of Calgary, Alberta, Canada, said, "This is really important data. This is the big question that everyone is struggling with — how we redesign our stroke systems of care to get as many eligible patients as possible to mechanical thrombectomy in a timely manner. The dilemma is whether to stop at primary stroke center first on the way. These data have given us a starting point in how to make some guidelines on this."

Also commenting for Medscape Medical News, chair of the ISC session at which the analysis was presented, Valeria Caso, MD, University of Perugia, Italy, called the data "impressive."

"It does appear that going straight to the endovascular center will improve outcomes," she said. "But for the best results we need good preselection of patients in the field to go directly to the correct center, and we need to completely reorganize our systems for this. We need to improve skills of preselection by training paramedics.

"We're not quite at the stage yet to know which patients to take directly," she added. "This is still very preliminary data. For now, I would still recommend going to nearest primary stoke center and to get there as soon as possible."

The STRATIS registry is a prospective, multicenter, observational, single-arm study designed to capture the real-world experience of mechanical thrombectomy without the requirement of specialized imaging, age limits, or technique exclusions specified in some of the randomized trials.

The registry study, which is sponsored by Medtronic, manufacturer of the Solitaire stent retriever, includes patients from academic and nonacademic centers in the United States who received thrombectomy within 8 hours from symptom onset.

The registry includes a total of 984 patients from 55 sites. They had a mean age of 67 years and a mean National Institutes of Health Stroke Scale score of 17.3; 64% received tPA. The median time from stroke onset to start of the procedure was 208 minutes, which is shorter than in the randomized trials. And at 90 days, good outcome (modified Rankin Scale [mRS] score, 0 - 2) was achieved in 56.6% of patients — very similar to results from the randomized trials, researchers reported.

Data on time to get to the endovascular treatment center in the STRATIS study was the focus of a separate presentation at the ISC meeting.

Results showed that the overall median time between emergency services arrival to the patient and the start of the endovascular procedure was 152 minutes, and each hour delay in this interval was associated with an 8.3% relative decline in the likelihood of achieving a good outcome (mRS score, 0 - 2), or a number needed to harm of 18 per hour of delay.

A key factor in time delays was transferring patients from a primary stroke centre to a comprehensive center where endovascular treatment could be given.

Dr Froehler presented data showing that median time from stroke onset to revascularization was 202 minutes for patients taken directly to the comprehensive center vs 312 minutes for patients going initially to a primary stroke center and then transferred to the comprehensive center (P < .0001).

Clinical outcomes at 90 days were also better in the direct group, with 60.0% (299 of 498) achieving an mRS score of 0 - 2 compared with 52.5% (214 of 408) in the transfer group (P = .02).

After accounting for differences in outcome related to time to endovascular treatment, the administration of intravenous t-PA did not have a significant effect on outcome, he said.

Dr Froehler reported a hypothetical "bypass" scenario, which was calculated by comparing door-to-tPA times for both groups and adding the transfer time to the direct group for a conservative estimate of additional travel time.

This suggested that taking patients directly to the comprehensive center would delay tPA administration by as much as 22 minutes but thrombectomy would be performed 90 minutes sooner.

In a further analysis, the researchers calculated that if patients within 20 miles of an endovascular center were taken directly to that center, then tPA would be delayed by only 2 minutes, with only 3% of patients missing out on thrombolytic therapy. But overall time to endovascular treatment was reduced from 240 to 148 minutes.

"In this sort of scenario, a few patients will miss the opportunity to receive tPA. However, if they have a large-vessel occlusion, it is unlikely that tPA will have much benefit anyway. The major problem is trying to identify those patients in the field," Dr Froehler said.

Dr Smith added: "This data does suggest that taking patients within a certain cutoff distance to the comprehensive center directly enables much faster endovascular treatment at the cost of a small delay to tPA. But these decisions are particularly challenging if the patient misses out on tPA as a result of this."

The STRATIS registry is supported by Medtronic.

International Stroke Conference (ISC) 2017. Abstracts LBP3 and LB15. Presented February 22 and 23, 2017.

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