SWIFT PRIME Analysis Underscores Importance of ‘Time Is Brain’ Concept in Acute Stroke

Using stent retrievers to treat acute strokes caused by large-vessel occlusions has been shown to boost functional outcomes in multiple trials, and a new analysis of the SWIFT PRIME trial affirms that faster reperfusion is better.

In the stent retriever arm of the trial, 91% of patients treated within 2-and-a-half hours achieved functional independence at 90 days, report Mayank Goyal, MD (University of Calgary, Canada), and colleagues.

That rate drops by an absolute 10% over the next hour, however, and by an absolute 20% for each additional 60-minute delay after that, they report online April 19, 2016, ahead of print in Radiology.

“Time is brain,” Goyal told TCTMD in an email. “This effect is very powerful.”

Because of that, there must be a focus on optimizing workflow to eliminate delays, according to Goyal and colleagues. That was achieved across the 39 hospitals in SWIFT PRIME by the setting of aggressive time goals, provision of real-time feedback, and implementation of a continuous quality-improvement program.

That success in bringing times down across centers “suggests that it can be done,” Goyal said, noting that even shorter times might be possible in everyday practice because participation in a trial can sometimes slow down workflow. “Of course,” he added, “it will require teamwork, training, and commitment.”

Commenting on the study for TCTMD, Jeffrey Carpenter, MD (West Virginia University, Morgantown, WV), who was a trial investigator but not involved in the current study, said achieving the process times seen in SWIFT PRIME is challenging but doable for centers already equipped to deliver endovascular stroke therapies.

At his center, speeding workflow did not require additional resources. Changing how decisions were made and various tasks were performed—in parallel instead of in sequence—was key to shortening the steps from when a patient arrived at the emergency department to when the blocked vessel was opened, he said.

Rather than waiting for perfusion images to be fully processed before activating the stroke team, for example, his group started activating the team before the images came back. That alone saved about 10 minutes, which is substantial when looking at early time frames, Carpenter said.

“All it is is coordination of existing resources,” he said.

Earlier Trials Show Need for Faster Treatment

Earlier trials of endovascular therapy for acute stroke—including IMS III and SYNTHESIS Expanded—failed to show a benefit over IV thrombolysis alone, but they also demonstrated that there was much room for improvement in terms of workflow and more rapid treatment.

Based on those lessons, SWIFT PRIME was designed with a program aimed at accelerating workflow. The primary target of workflow efficiency was a time from qualifying imaging acquisition to groin puncture of less than 70 minutes.

That focus on speed likely contributed to the results of the 196-patient trial, which was stopped early after showing that adding thrombectomy with the Solitaire stent retriever (Covidien) to IV thrombolysis improved functional outcomes compared with IV thrombolysis alone.

In the current study, Goyal and colleagues delved deeper into the time spent on each step of the process of treating patients and looked at the impact of time to treatment on outcomes.

The median time from qualifying imaging acquisition to groin puncture in the trial was 52 minutes, with the goal of less than 70 minutes achieved in 61% of patients.

Greater speed in treatment, assessed using the time either from symptom onset to reperfusion or from qualifying imaging to reperfusion, was associated with an increased likelihood of achieving functional independence, defined as a modified Rankin Scale score of 0 to 2 at 90 days.

The researchers also looked at the impact of transferring patients to receive endovascular therapy. Most patients in the trial (64%) presented directly to a center capable of delivering endovascular therapy, but the rest came via transfer from a referral facility, where IV thrombolysis was started. Transfer was associated with a substantial delay in presentation to the endovascular-capable center that was only partially offset by shorter times during some parts of the workflow after transfer. Ultimately, median symptom onset to groin puncture time was nearly 100 minutes longer for transferred patients (275.0 vs 179.5 minutes; P < 0.001).

Quicker Treatment, Better Devices Behind Recent Endovascular Success

Goyal and colleagues point out that workflow was much speedier in SWIFT PRIME than in the earlier endovascular trials. In IMS III, for example, the interval from randomization to reperfusion was 182.5 minutes; it was just 54 minutes in SWIFT PRIME. Other recent trials—MR CLEAN, ESCAPE, EXTEND-IA, and REVASCAT—have also demonstrated the benefits of endovascular therapy, and a common thread is quicker treatment.

The key to speeding up the process is performing activities in parallel, according to both Carpenter and the study authors.

Ensuring that workflow stays optimized is dependent on several factors, Goyal said. A system should be created so that patients who are most likely to need endovascular treatment arrive directly at a center capable of delivering the therapy, and that center should have a cohesive team with members who understand their roles and focus on efficiency. In addition, he said, there should be a focus on relevant and expeditious imaging and a system in place to provide feedback to allow continued improvement in processes.

At Carpenter’s center, monthly meetings are held to go over all endovascular cases and to address any issues with workflow that might be resulting in times drifting upward.

Carpenter said that workflow improvements are not the whole story when it comes to the recent success of endovascular therapy in clinical trials, however. The newer devices—stent retrievers, in particular—are superior to devices used in the earlier trials for achieving reperfusion, he said.

“Time to treatment and recanalization are the primary two drivers,” he said. “You can throw almost everything else out.”

Related Stories:

• Endovascular Treatment Shows Dramatic Benefits for Large Strokes in 3 Trials
• Another Meta-analysis Strengthens Case for Endovascular Therapy in Acute Stroke
• Thrombectomy for Acute Stroke Works Across Subgroups, but Best When Done Early