Background: Previous randomized trials of endovascular therapy for stroke have shown better rates of functional independent outcome (mRS 0-2 at 90 days) with earlier initiation of endovascular therapy. In these trials no information was available to assess the volume of salvageable brain tissue prior to intervention or tissue reperfusion post- intervention. We sought to determine the associations between times to treatment, mismatch volume, reperfusion rates and functional independent outcome (FIO) in patients with the Target mismatch (TMM) profile in SWIFT PRIME.
Methods: Patients with TMM on CT or MR perfusion, as determined by an automated software package (RAPID), were included in the analysis. We compared the rate of FIO and factors associated with FIO in patients randomized early (<3h) vs. late (>3h) from stroke symptom onset (SSO). Age, NIHSS, core volume, mismatch volume and successful reperfusion at 27 h (>90% reduction in perfusion lesion volume on CT or MR Perfusion) were included in univariate and a multivariate logistic regression analysis.
Results: A total of 131/195 patients had TMM. FIO was 62.3% (33/53) in the early vs. 43.6% (34/78) in the late group, p=0.0498. In the Solitaire arm, FIO was 72.4% (21/29) in early group vs. 55.0% (22/40) in the late group. In the tPA arm FIO was 50.0% (12/24) in the early group vs. 31.6% (12/38) in the late group. There was no significant difference in age, baseline NIHSS, core volume, or mismatch volume among the overall early vs late groups but successful reperfusion at 27h occurred in 76% of the early vs. 55% of the late group (p<0.05). The rate of successful reperfusion at 27h was 92% (early) vs. 81% (late) for Solitaire; p=0.28 and 61% (early) vs. 27% (late) for tPA; p=0.032). The 27 hour CTA or MRA TICI 2b-3 rates were 92% (early) vs. 84% (late) for Solitaire group and 71% (early) vs. 38% (late) for tPA group.
Conclusions: Earlier lytic and stent-retriever thrombectomy interventions are associated with higher rate of FIO in patients with Target mismatch profiles in SWIFT Prime trial. This improved outcome is likely due to higher reperfusion rates that are achieved with earlier intervention, suggesting greater responsiveness of less organized and less compacted thrombi to fibrinolysis and potentially stent retrieval.