SWIFT PRIME
Solitaire with the Intention for Thrombectomy as Primary Endovascular Treatment (SWIFT PRIME) trial
Clinical Question
In patients with acute ischemic stroke due to occlusions in the proximal anterior intracranial circulation, does stent-retriever thrombectomy in addition to intravenous t-PA improve long-term functional outcome compared to intravenous t-PA alone?
Bottom Line
In patients receiving intravenous t-PA for acute ischemic stroke due to proximal anterior intracranial circulation occlusions, thrombectomy with a stent retriever within 6 hours after onset significantly improved functional outcomes at 90 days, without significantly increasing mortality or symptomatic intracranial hemorrhage.
Major Points
- One of five landmark 2015 thrombectomy RCTs. Unique for being the only trial to require IV tPA in both arms (bridging therapy mandatory) and the only industry-sponsored trial in the group.
- Stopped early at 196 patients (target 833) after interim analysis showed overwhelming efficacy — the largest absolute treatment effect among the 2015 trials.
- Functional independence (mRS 0–2) at 90 days: 60% thrombectomy vs 35% IV tPA alone (NNT 4, p<0.001) — the highest absolute benefit of any 2015 thrombectomy trial.
- mRS ordinal shift analysis also significant (p<0.001). 0% sICH in the thrombectomy group vs 3% in control — the only 2015 trial with lower sICH in the intervention arm.
- 88% achieved substantial reperfusion (mTICI 2b/3) — among the highest rates in the 2015 trials, reflecting experienced operators and Solitaire device efficacy.
- Imaging criteria evolved mid-trial: initially required target-mismatch perfusion profile (CT perfusion using RAPID software), later changed to small-to-moderate core strategy (ASPECTS-based). Both criteria yielded positive results.
- Occlusion sites: ICA ~17%, M1 ~72%, M2 ~10%. Solitaire FR or Solitaire 2 was the mandated first-line device.
- Workflow was fast: median qualifying image to groin puncture 57 min, ED arrival to groin puncture 90 min, onset to first stent retriever deployment 252 min.
- 24-hour reperfusion on perfusion imaging: 83% thrombectomy vs 40% control (p<0.001). NIHSS improvement at 27h: −8.5 vs −3.9 (p<0.001).
- 90-day mortality: 9% vs 12% (p=0.50) — numerically lower in thrombectomy group but not significant.
- Contributed to the 2015 AHA/ASA Class IA recommendation for thrombectomy in LVO stroke within 6 hours.
Design
Study Type: Randomized, double-blind, placebo-controlled, parallel-group trial
Randomization: 1
Blinding: Blinded assessment of neurovascular images
Enrollment Period: December 2012 through November 2014
Follow-up Duration: 90 days
Centers: 39
Countries: United States, Europe
Sample Size: 196
Analysis: Cochran-Mantel-Haenszel test for primary outcome; dual success criteria with group sequential-analysis plan
Inclusion Criteria
- Patients with acute ischemic stroke
- Moderate-to-severe neurologic deficits
- Imaging-confirmed occlusion of the intracranial internal carotid artery, the first segment of the middle cerebral artery, or both
- Met imaging eligibility requirements (initially target-mismatch penumbral profile, later small-to-moderate core-infarct strategy)
- Receiving or had received intravenous t-PA
- Able to undergo initiation of endovascular treatment within 6 hours after the time that they were last known to be well before the onset of acute stroke symptoms
Exclusion Criteria
- Large ischemic-core lesion on imaging (ASPECTS <6 or core volume >50 mL on perfusion).
- Pre-stroke disability (mRS >1).
- No confirmed proximal anterior circulation occlusion on CTA/MRA.
- Not receiving or not eligible for IV tPA (all patients required bridging therapy).
- NIHSS <8 (mild stroke).
- Posterior circulation occlusion.
- Known hemorrhagic diathesis or INR >3.0.
- Platelet count <40,000.
- Blood glucose <50 mg/dL.
- Severe allergy to contrast media.
- Pregnancy or suspected pregnancy.
Arms
| Field | Control | Stent Retriever plus Intravenous t-PA |
|---|---|---|
| Intervention | IV alteplase 0.9 mg/kg (max 90 mg), 10% bolus over 1 min followed by 90% infusion over 60 min, started within 4.5h of symptom onset. Standard post-tPA care including BP management (<180/105), neurological monitoring, and 24h CT before starting antithrombotics. No endovascular intervention permitted. | IV alteplase (same protocol as control) followed by endovascular thrombectomy using Solitaire FR or Solitaire 2 stent retriever within 6 hours of onset. Solitaire was the mandated first-line device; rescue with other FDA-approved devices permitted. Up to 3 passes recommended. General anesthesia or conscious sedation at operator discretion. Balloon guide catheter recommended. Continuous quality improvement program implemented to optimize workflow. Target: qualifying image to groin puncture <60 min. |
| Duration | 90 days follow-up | 90 days follow-up |
Outcomes
| Outcome | Type | Control | Intervention | HR / OR / RR | P-value |
|---|---|---|---|---|---|
| Severity of global disability at 90 days, as assessed by means of the modified Rankin scale (scores 0 [no symptoms] to 6 [death]). Both overall distribution shift and proportion of patients with functional independence (mRS 0-2) were used as simultaneous success criteria. | Primary | Median mRS: 3 (IQR 2-5) | Median mRS: 2 (IQR 1-4) | 2.6 | <0.001 |
| Functional independence at 90 days (modified Rankin scale score, ≤2) | Secondary | 33/93 (35%) | 59/98 (60%) | 1.7 | <0.001 |
| Change in NIHSS score at 27 hr | Secondary | -3.9±6.2 | -8.5±7.1 | <0.001 | |
| Death at 90 days | Secondary | 12/97 (12%) | 9/98 (9%) | 0.74 | 0.50 |
| Substantial reperfusion immediately after thrombectomy (modified Thrombolysis in Cerebral Infarction score of 2b or 3) | Secondary | NA | 73/83 (88%) | NA | |
| Successful reperfusion at 27 hr (reperfusion of ≥90% by perfusion CT or MRI) | Secondary | 21/52 (40%) | 53/64 (83%) | 2.05 | <0.001 |
| Any serious adverse event at 90 days | Adverse | 30 (31%) | 35 (36%) | 1.15 | 0.54 |
| Symptomatic intracranial hemorrhage at 27 hr | Adverse | 3 (3%) | 0 | 0.00 (NA) | 0.12 |
| Parenchymal hematoma | Adverse | 7 (7%) | 5 (5%) | 0.71 | 0.57 |
| Parenchymal hematoma Type 1 | Adverse | 3 (3%) | 4 (4%) | 1.32 | 1.00 |
| Parenchymal hematoma Type 2 | Adverse | 4 (4%) | 1 (1%) | 0.25 | 0.21 |
| Subarachnoid hemorrhage | Adverse | 1 (1%) | 4 (4%) | 3.96 | 0.37 |
Criticisms
- Mandatory IV tPA in both arms — excludes patients ineligible for thrombolysis (late presenters, anticoagulated, recent surgery), limiting generalizability to the direct thrombectomy population.
- Stopped early at 196/833 patients (24%) — the most extreme early termination among the 2015 trials, potentially overestimating treatment effect.
- Industry-sponsored (Covidien/Medtronic) — the only 2015 thrombectomy trial with full industry sponsorship, raising potential conflict of interest concerns.
- Imaging eligibility changed mid-trial from perfusion-based target mismatch to ASPECTS-based core strategy — introduces heterogeneity in patient selection.
- All sites were tertiary centers with experienced neurointerventionalists and a continuous quality-improvement program — workflow times may not be achievable in community settings.
- Excluded M2 and posterior circulation occlusions — later addressed by trials like ASTER 2 and BASICS.
- Keywords field contains erroneous semaglutide/diabetes terms — likely a data entry error from the original trial database.
- No comparison with aspiration-first technique (ADAPT) — only Solitaire stent retriever evaluated.
- 6-hour time window — does not address late-presenting patients, who were later shown to benefit in DAWN and DEFUSE 3.
Subgroup Analysis
No heterogeneity of treatment effect across 8 prespecified subgroups: sex (male OR 1.57, female OR 2.02), age (<65: OR 1.85, ≥65: OR 1.55), NIHSS (<17: OR 1.73, ≥17: OR 1.67), occlusion site (ICA: OR 2.10, M1: OR 1.61), geographic region (US vs Europe), ASPECTS (≤8: OR 1.79, >8: OR 1.61), tPA given at enrolling vs outside hospital, time from onset to randomization (<3h: OR 1.81, ≥3h: OR 1.47). All subgroups showed consistent benefit. Mid-trial imaging protocol change (target mismatch → ASPECTS-based) yielded positive results under both criteria. Trial underpowered (n=196) for formal interaction tests.
Funding
Covidien
Based on: SWIFT PRIME (The New England Journal of Medicine, 2015)
Authors: Jeffrey L. Saver, M.D., Mayank Goyal, ..., and Reza Jahan
Citation: N Engl J Med 2015;372:2285-95.
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