Background The thrombus enhancement sign (TES) is thought to be associated with the source of the stroke and thrombus composition. We investigated whether this imaging sign along with other thrombus characteristics could be used to predict the successful first pass effect (FPE) of mechanical thrombectomy.

Methods 246 consecutive patients with acute ischemic stroke in the anterior circulation with large vessel occlusion who underwent thrombectomy with a stent retriever and clot collection were included. Patients were divided into FPE (modified Thrombolysis in Cerebral Infarction (mTICI) grade 2c or 3)/non-FPE (mTICI 0–2b) and modified FPE (mFPE) (mTICI 2b–3)/non-mFPE (mTICI 0–2a) groups based on flow restoration after the first pass. TES presence, thrombus density, thrombus length, clot burden score, and thrombus composition were compared. The association between FPE and imaging biomarkers, along with clinical and interventional parameters, was investigated by univariate and multivariate analysis.

Results FPE was achieved in 85 (34.6%) patients. TES presence was significantly lower in the FPE group (64.7% vs 80.7% in the non-FPE group, p=0.008) and mFPE group (69.1% vs 81.0% in the non-mFPE group, p=0.039). Histopathological examination revealed that TES (+) thrombi contained a higher fibrin/platelet proportion (50.9% vs 46.9% in TES (−) thrombi, p=0.029) and fewer erythrocytes (43.3% vs 47.3% in TES (−) thrombi, p=0.030). Thrombus characteristics, namely shorter thrombus length (p=0.032), higher erythrocyte proportions (p=0.026), and less fibrin/platelets (p=0.014), were confirmed in patients with FPE. In multivariable analysis, TES was the only independent predictor of FPE failure (OR 0.51, 95% CI 0.28 to 0.94; p=0.031).

Conclusions TES was independently associated with first pass angiographic failure in patients treated with a stent retriever.