Abstract WP19: Rate and Speed of Reperfusion Explains Variations in Treatment Effect Sizes Across Recent Trials of Endovascular Therapy for Acute Ischemic Stroke

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Background: Five recent trials demonstrated benefit of endovascular treatment (ET) for large-vessel ischemic stroke. But, while all were positive, the trials differed in their estimates of benefit magnitude. We tested whether trial differences in rate and speed of successful accounted for their variations in effect size estimates.

Methods: We analyzed all 5 recent positive endovascular stroke trials, MR CLEAN, ESCAPE, EXTEND-IA, REVASCAT, and SWIFT-PRIME. An expanded analysis also included the 2 prior neutral trials, IMS-3 and MR RESCUE. Linear regression and correlation coefficients probed variable relations.

Results: Among the 5 positive trials, rates of substantial reperfusion ranged from 59%-88% and OTR from 241-355 minutes. Independent functional outcome rates ranged in the endovascular arms from 32.6% to 71.4%, and in the control arms from 19.1% to 40.0%. Absolute differences in functional independence between treatment arms ranged from 13.5% - 31.4%. In the 2 neutral trials, reperfusion rates were lower, OTR longer, and outcome differences much less. Linear regression demonstrated very strong relation of both trial reperfusion rate and trial reperfusion speed to trial magnitude of treatment benefit (Figure). Across all 7 trials, the correlation between reperfusion rate and treatment effect size was r= 0.98, and between reperfusion speed and treatment effect size was r=0.85. Among just the 5 positive trials, reperfusion rate correlation with treatment effect size was r=0.87, and between reperfusion speed and treatment effect size was r=0.89.

Conclusion: Achievement of successful reperfusion and speed of reperfusion are potent determinants of the degree of benefit with endovascular reperfusion therapy, and account for more than three-quarters of the variation in degree of treatment benefit in the 5 recent positive thrombectomy trials. To maximize patient benefit from endovascular intervention, open arteries fully and fast.

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