Absence of susceptibility vessel sign is associated with aspiration-resistant fibrin/platelet-rich thrombi.

BACKGROUND: The composition of the thrombus influences its retrievability by mechanical thrombectomy. PURPOSE: Our study aimed to report on thrombi resistant to aspiration, regarding susceptibility vessel sign and histologic composition. METHODS: This observational study was based on a prospective database of acute anterior circulation ischemic strokes treated by mechanical thrombectomy. Endovascular first-line strategy was aspiration and in case of failure, combined therapy-rescue was performed. The positivity of susceptibility vessel sign (SVS+) or its negativity (SVS-) was assessed on T2* sequences. The thrombus composition was analyzed with hematoxylin eosin staining. RESULTS: Histological analysis was performed on 102 clots. Thrombi with SVS- were significantly richer in fibrin/platelets, p = 0.04. Out of 210 mechanical thrombectomy, aspiration first pass strategy was performed in 131/210 (62%) patients. Combined therapy-rescue was needed in 37% of aspiration first pass strategy cases (n = 131). Clots retrieved combined therapy-rescue were richer in fibrin/platelets 63.9% versus 50.8% for aspiration first pass strategy, p = 0.03. Logistic regression analysis showed that fibrin/platelet-poor clots (<60%) were significantly more likely to be recanalized by aspiration first pass strategy compared to fibrin/platelet-rich clots (>60%) that were more likely recanalized by combined therapy-rescue after aspiration first pass strategy failure (OR = 3.5; 95% CI = 1.2-10.8; p = 0.0054). CONCLUSIONS: Our results confirm that SVS- clots are rich in fibrin/platelets and suggest that these "white clots" are less likely to be retrieved by aspiration alone and more often require the use of combined therapy.

External Validation of the ELAPSS Score for Prediction of Unruptured Intracranial Aneurysm Growth Risk.

Background and PURPOSE: Prediction of intracranial aneurysm growth risk can assist physicians in planning of follow-up imaging of conservatively managed unruptured intracranial aneurysms. We therefore aimed to externally validate the ELAPSS (Earlier subarachnoid hemorrhage, aneurysm Location, Age, Population, aneurysm Size and Shape) score for prediction of the risk of unruptured intracranial aneurysm growth. METHODS: From 11 international cohorts of patients ≥18 years with ≥1 unruptured intracranial aneurysm and ≥6 months of radiological follow-up, we collected data on the predictors of the ELAPSS score, and calculated 3- and 5-year absolute growth risks according to the score. Model performance was assessed in terms of calibration (predicted versus observed risk) and discrimination (c-statistic). RESULTS: We included 1,072 patients with a total of 1,452 aneurysms. During 4,268 aneurysm-years of follow-up, 199 (14%) aneurysms enlarged. Calibration was comparable to that of the development cohort with the overall observed risks within the range of the expected risks. The c-statistic was 0.69 (95% confidence interval [CI], 0.64 to 0.73) at 3 years, compared to 0.72 (95% CI, 0.68 to 0.76) in the development cohort. At 5 years, the c-statistic was 0.68 (95% CI, 0.64 to 0.72), compared to 0.72 (95% CI, 0.68 to 0.75) in the development cohort. CONCLUSION: s The ELAPSS score showed accurate calibration for 3- and 5-year risks of aneurysm growth and modest discrimination in our external validation cohort. This indicates that the score is externally valid and could assist patients and physicians in predicting growth of unruptured intracranial aneurysms and plan follow-up imaging accordingly.