Thrombectomy performed within 6 hours of symptom onset has been demonstrated to significantly improve clinical outcomes after stroke. Though there is generally diminishing benefit with increased time interval from last known well to the time of intervention, some previous data suggested that patients with “salvageable” brain tissue on diffusion weighted imaging (DWI) may still benefit from reperfusion despite being beyond the 6 hour window. Recently published randomized controlled trials including the DAWN and DEFUSE-3 trials now provide further evidence supporting this practice, though to a selected population of patients.

Here’s an overview of the DAWN (DWI or CTP Assessment with Clinical Mismatch in the Triage of Wake-Up and Late Presenting Strokes Undergoing Neurointervention with Trevo) trial:

  • Population: multicenter study, 206 patients with ICA/MCA infarcts with a last known well of 6-24 hours prior to randomization and with a greater than expected neuro deficit compared to the infarct volume on neuroimaging
  • Intervention: thrombectomy + usual care
  • Control: usual care alone
  • Outcomes: the average disability scores (utility-weighted modified Rankin scale) and the rate of functional independence at 90 days.
    •  significantly improved UW-mRS in the intervention vs control group (5.5 vs 3.4 out of 10 point scale)
    • 49% vs 13% functionally independent at 90 days in the intervention and control groups, respectively
    • NNT to gain functional independence = 2.8
    • Trial stopped early after interim analysis showed clear benefit of thrombectomy
    • Recanalizaton achieved in 77% vs 36% of patients
    • similar symptomatic ICH and stroke-related death rates at 90 days
  • Limitations:
    • infarct volumes overall very small (median 8-9 mL) though inclusion criteria ranged from <21 mL to max 51 mL. I couldn’t find data on typical acute MCA stroke volumes, but, for comparison, in another small study, the mean final infarct volumes in MCA strokes was 195 mL. Authors predict that 1/3 of patients
    • patients with milder symptoms (NIHSS <10) were excluded, further limiting generalizability
    • Stryker-sponsored study (though authors had full access to data and no writing assistance from the sponsor)

Despite the limitations, it seems that this study demonstrates potentially significant benefit in quality of life and little harm to the carefully chosen stroke patient, and it makes sense that we are now involving neurology and calling stroke codes for patients with delayed stroke presentations and wake-up strokes.

Nogueira et al. Thrombectomy 6 to 24 Hours after Stroke with a Mismatch between Deficit and Infarct. NEJM 2018.

August 2022