Impact of Thrombus Length on Outcomes After Intra-Arterial Aspiration Thrombectomy in the THERAPY Trial

Background and Purpose-Increasing thrombus length (TL) impedes recanalization after intravenous (IV) thrombolysis. We sought to determine whether the clinical benefit of aspiration thrombectomy relative to IV r-tPA (recombinant tissuetype plasminogen activator) may be greater at longer TL. Methods-THERAPY was a randomized trial of aspiration thrombectomy plus IV r-tPA versus IV r-tPA alone in largevessel stroke patients with prospective TL measurement >= 8 mm. In this post hoc study, we evaluated the association of TL with trial end points and potential endovascular treatment effect, using univariate, multivariable, and multiplicative interaction analyses. Results-TL data were available for all 108 patients (28% internal carotid artery, 62% M1, and 10% M2). Median TL was 14.0 mm (interquartile range, 9.7-19.5 mm). Longer TL was associated with worse outcome (90-day modified Rankin Scale score: odds ratio, 1.24 per 5-mm TL increment; 95% confidence interval, 1.04-1.52; P=0.02), even after adjusting for key outcome predictors (adjusted P=0.004). Longer TL was also associated with more serious adverse events (adjusted P=0.01), more symptomatic hemorrhages (adjusted P=0.03), and increased mortality (adjusted P=0.01). No significant relationship was observed between TL and angiographic reperfusion (modified thrombolysis in cerebral ischemia 2b-3), but greater TL was associated with longer endovascular procedural times (rho=0.36; P=0.045). Increasing TL was associated with greater aspiration thrombectomy treatment effect (interaction term P=0.03). This might be related to a potentially stronger adverse effect of increasing TL on 90-day modified Rankin Scale for patients treated with IV r-tPA (rho=0.39; P=0.01) compared with intra-arterial therapy (rho=0.20; P=0.165). Conclusions-Ischemic stroke patients with longer symptomatic thrombi have worse 90-day clinical outcomes but may have a greater relative benefit of aspiration thrombectomy over IV r-tPA alone.