Abstract 3846: Contrast Permeation In Hyperdense Artery Sign: Evidence Of Freshly Forming Thrombus Accumulating Around The Initial Clot? Pilot Data From The Interrsect Multicentre Thrombus Imaging Study.

Introduction: Previous work has examined the importance of thrombus density impacting recanalization with systemic thrombolysis. The mechanism underlying thrombus density however is not well understood. RBC content is known to be high in hyperdense thrombi. We evaluated the relationship between density of thrombi and flow characteristics within and adjacent to thrombi in iv tPA treated patients in the INTERRSeCT pilot study. Methods: The pilot data analysed includes any patient (age > 40) with evidence of a visible and symptomatic thrombi on baseline CTA treated with IV t-PA as standard of care. Each patient enrolled in the study had early recanalization assessed on repeat CTA within 3-5 hours of baseline imaging. Imaging data were analyzed in a core-imaging lab. Hyperdense sign on NCCT, length and presence of contrast permeation through thrombus on CTA were assessed on 5 mm image slices using OSIRiX, an image processing software. Results: Of 101 patients enrolled in INTERRSeCT, 35 patients with MCA or intracranial ICA thrombi (mean age 70+− 12.5 yrs, 53% male) treated with IV t-PA were included in this analysis. The hyperdense sign (HDS) was seen in 22/35 (62.8%) and contrast permeation through thrombus was seen in 19/35 (54.2%). Median clot length was significantly higher in patients with HDS when compared to those without (2.46 cm vs 1.33 cm, p=0.03). We noted increased probability of contrast permeation in the presence of HDS (68.1% in HDS+ vs 30.7% in HDS-, p=0.03). (Table and Figure) HDS was associated with significantly lower early recanalization rates (36.3% in HDS+ vs 84.6% in HDS-, p=0.01). Conclusion: The evidence of contrast permeation, increased density and longer length of occlusion support the hypothesis that hyperdense artery sign represents freshly forming thrombus accumulating around the initial clot. These composite clots recanalize less with IV t-PA when compared to native clots. A larger cohort of patients is required to confirm these results.