Abstract W MP8: The Natural History of Acute Ischemic Stroke from Large Vessel Proximal Occlusion: A Comparison with the IMS III Patients

Purpose: The recent termination of the IMS III trial due to futility has led to further controversies surrounding the use of IA endovascular therapy for stroke intervention. But since not all IMS patients had confirmed large vessel occlusion, it remains unclear if the study population was appropriate for endovascular therapy. The purpose of this study was to assess the natural history of a stroke cohort eligible for IA intervention and compare its outcome with the IMS III results. Methods: The FIRST Trial is a prospective natural history study of a stroke cohort eligible for but untreated by endovascular therapy and ineligible or refractory to IV rtPA. The primary endpoint is functional outcome as defined by 90-day mRS ≤2. All patients were assessed for 90 days from stroke onset. Results: Among the 62 patients who met entry criteria, mean age was 68 ± 16 years; median admission NIHSS was 18 (IQR 14-22). Occlusions were in the ICA (31%), MCA (66%) and other (3%). At admission, the TIMI 0-1 rate was 100%, and the TICI 0-1 rate was 98%, with 52% refractory to IV rtPA. Spontaneous recanalization to TIMI 2-3 or TICI 2a-3 was only seen in 10% or 13%, respectively. Good 90-day outcome was achieved in 21%; 42% died. When compared to the FIRST patients, the IMS III IA-treated group had significantly higher recanalization (p<0.0001) and functional independence (p=0.00363) rates; and lower mortality (p=0.00013). The IV control group also had a higher rate of recanalization and 90-day functional independence, and a lower rate of mortality. In another analysis, pooled patients (N=942) treated by the aspiration-based Penumbra System had a higher rate of recanalization (p<0.0001), lower mortality (p=0.00052) and greater functional independence at 90 days (p=0.00719). Conclusion: These results indicate selection of an appropriate study population is important in assessing the safety and effectiveness of endovascular therapy in large vessel occlusion.