PurposeTo examine the relationship between hyperdense artery sign/susceptibility vessel sign (HAS/SVS) and thrombus composition, and evaluate the effect of HAS/SVS status on the association between first-line thrombectomy techniques and outcomes in patients with acute anterior-circulation large vessel occlusion (LVO). Materials and MethodsFrom January 2018 to June 2021, 103 consecutive acute anterior-circulation LVO patients (75 [63.1%] male; median age, 66 years) who underwent thrombectomy, and for whom the removed clot was available for histological analyses were retrospectively reviewed. The presence of HAS and SVS was respectively assessed in noncontrast computed tomography (NCCT) and susceptibility-weighted imaging (SWI). Association of first-line thrombectomy techniques [stent retriever combined with contact aspiration (SR+CA) versus contact aspiration (CA)] with outcomes was assessed by the HAS/SVS status. ResultsAmong the included patients, 55 (53.4%) were HAS/SVS(-), and 69 (67.0%) chose first-line SR+CA. Higher relative densities of fibrin/platelets (0.56 vs. 0.51, p<0.001) and lower relative densities of erythrocytes (0.32 vs. 0.42, p<0.001) were observed in HAS/SVS(-) than HAS/SVS(+) patients. First-line SR+CA was associated with reduced odds of distal embolization (aOR, 0.18; 95% CI, 0.04–0.83; p=0.027) and a more favorable 90-day functional outcome (aOR, 5.29; 95% CI, 1.06–26.34; p=0.042) in HAS/SVS(-) patients, and a longer recanalization time (53 min vs. 25 min, p=0.025) and higher risk of subarachnoid hemorrhage (24.2% vs. 0%, p=0.044) in HAS/SVS(+) patients. ConclusionsHAS/SVS(-) may indicate a higher density of fibrin/platelets in the thrombus, and first-line SR+CA may have a possible better performance than CA in acute LVO patients without HAS/SVS.