Purpose Thin-section (≤2.5 mm) NCCT is a dependable method for measurement of clot length in documented anterior circulation occlusions. A majority of clots in the proximal anterior circulation are ≥8 mm, which have low probability of revascularization with IV rtPA alone. Nevertheless, past studies have had sampling restrictions, and correlations of clot length continue to be classified.

Methods Data was captured to investigate potential correlates of clot length from an ongoing multicenter review. Patients were eligible if presented within 8 h of onset, had thin-section NCCT admission imaging, and evidence of ICA-T, M1, or M2 MCA occlusion. All patients had their occlusions documented by CTA, angiography, or MRI. Patients did not necessarily have thrombectomy performed. Baseline characteristics of interest included age, sex, baseline NIHSS, ASPECTS, occlusion level, IV rtPA dose pre vs. post scan, time from stroke onset to imaging, and IA recanalization. Univariate analyzes were implemented with clot length as a dichotomized variable (≥8 mm vs <8 mm), and multivariate logistic regression was used to define predictors.

Results Consecutive stroke admissions were reviewed at 3 US centers between August 2011 and March 2013 for eligibility, and 175 patients met criteria. Mean age was 70 years old; 56% were female. Median baseline NIHSS score was 17 (IQR 12–22). The level of occlusion was distributed such that 23% were ICA-T, 54% M1, and 23% M2 MCA. Of the 175 confirmed occlusions, hyperdense clot was visible in 89% (156/175) of cases. Visible clot ranged from 2 mm to 65 mm, while mean length was 14 mm. There were 66% (115/175) patients with clot lengths ≥8 mm. In comparing clot length to occlusion level, 90% of ICA-T, 69% of M1, and 34% of M2 occlusions were ≥8 mm (p < 0.001), with median clot lengths of 20.5, 14.1, and 7.2, respectively. The only significant multivariate predictor of clot length was the occlusion level (OR, 95% CI =3.9 (2.2–6.9) per step from M2 to M1 to ICA-T, p < 0.0001).

Conclusion This analysis further supports the idea of measuring hyperdense thrombus by use of thin-section NCCT. Occlusion site is a key predictor of clot length, which may explain the relative ineffectiveness of IV rtPA in more proximal anterior circulation large vessels. These findings suggest a sizeable population who may benefit from a bridging approach.

Disclosures D. Frei: 3; C; Penumbra Inc. 4; C; Penumbra Inc. D. Heck: None. A. Yoo: 1; C; National Institutes of Health, Penumbra Inc., Remedy Pharmaceuticals. D. Loy: None. H. Buell: 5; C; Penumbra Inc. S. Kamalian: 1; C; GE Healthcare, Department of Defense, CIMIT. L. Morais: None. A. Bitner: 3; C; Penumbra Inc. D. Meyer: 5; C; Penumbra Inc. S. Kuo: 5; C; Penumbra Inc. A. Bose: 4; C; Penumbra Inc. 5; C; Penumbra Inc. S. Sit: 4; C; Penumbra Inc. 5; C; Penumbra Inc.