SWIFT PRIME: 'Dramatic' Benefit of Stent Retriever in Stroke

February 11, 2015

Nashville, Tennessee — In patients with acute ischemic stroke patients who have confirmed large vessel anterior circulation occlusions treated with thrombolysis, rapid treatment with the Solitaire FR (Flow Restoration) stent retriever (Covidien) reduced poststroke disability and increased the proportion of patients alive and independent at 3 months, in the SWIFT PRIME trial.

"The magnitude of the observed benefit was dramatic," Jeffrey Saver, MD, UCLA Comprehensive Stroke Center, Los Angeles, California, commented. "Among every 100 patients treated, 39 will have a better 3-month disability outcome than with tPA (tissue plasminogen activator) alone, including 25 more achieving functional independence at long-term follow-up.

"We conclude that Solitaire stent retriever is a highly beneficial treatment for patients with emergency large vessel occlusions causing acute ischemic stroke."

Dr Jeffrey Saver

Dr Saver presented the results here at the International Stroke Conference (ISC) 2015.

SWIFT PRIME, along with two other studies presented at the same ISC session, and published simultaneously in the New England Journal of MedicineEXTEND-IA and ESCAPE — add to the recently published MR CLEAN trial. All four studies show convincing evidence of benefit for endovascular therapy in selected stroke patients.

"Very Fresh Data"

SWIFT PRIME was conducted at 39 hospitals in the United States and Europe. Patients were enrolled if they could be treated with the mechanical clot removal device within 6 hours of symptom onset.

Enrollment into the study was placed on hold in November 2014, after recruitment of 196 patients, when the results of the MR CLEAN trial had become available and when the study monitoring committee noted "compelling differences between the treatment groups."

Results on the primary outcome — functional outcome at 90 days — were available only on February 4, "so these are very fresh data," Dr Saver said.

The SWIFT PRIME primary endpoint showed a substantial shift to lower disability levels on the modified Rankin scale (P = .0002. The proportion of patients alive and free of major disability (mRS 0-2) at 3 months also significantly improved, along with mean improvement of National Institutes of Health Stroke Scale (NIHSS) score at 27 hours.

SWIFT PRIME: Secondary Endpoints

Endpoints Endovascular Treatment Control P Value
mRS score of 0 - 2 at 90 d (%) 60.2 35.5 .0008
Mortality (%) 9.2 12.4 .50
Mean improvement in NIHSS score at 27 h (points) 8.5 3.9 <.0001

 

"There was benefit in all subgroups — young, old, small or moderate cores, early or later presentation, NIHSS scores — all showed similar magnitude of benefit," Dr Saver said.

He added that the reperfusion results were "excellent," with successful reperfusion (Thrombolysis in Cerebral Infarction  score of 2b/3) in 88% of patients receiving treatment with the Solitaire device.

Safety results were "good," with serious adverse events occurring in 35.7% of the intervention group vs 30.9% of the tPA-alone group (P = .54). "There was no difference in overall serious adverse events between the two study arms. Symptomatic intracranial hemorrhage also not different between the 2 groups and was only 1% in the Solitaire plus tPA group," Dr Saver reported.

The trial recruited patients with ischemic stroke aged 18 to -80 years, with a prestroke mRS score of 1 or less and NIHSS score of 8 to 29 (median, 17) at randomization and who all received tPA within 4.5 hours of stroke onset. Large vessel occlusion was confirmed by computed tomographic angiography (CTA) or magnetic resonance angiography.

Patients were further selected by advanced imaging to exclude those with large areas of unsalvageable brain tissue. Dr Saver elaborated: "We started with an automated perfusion imaging method to select patients similar to that used in EXTEND-IA. Then we switched to CTA as used in ESCAPE to accommodate more sites."

Like ESCAPE and EXTEND-IA, the SWIFT PRME study achieved fast reperfusion, with a time from imaging to groin puncture (picture to puncture) of 58 minutes and the time to first deployment of device of 252 minutes from symptom onset.

SWIFT PRIME was sponsored by Covidien. Dr Saver is a consultant for Covidien.

International Stroke Conference (ISC) 2015. Invited Presentation. Presented February 11, 2015.

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