Abstract 77: Histopathological Characteristics Of Iv Recombinant Tissue Plasminogen Resistant Thrombi In Patients With Acute Ischemic Stroke

Background: It remains unclear whether certain thrombus characteristics in patients with acute ischemic stroke result in lack of lysis with IV rt-PA. We performed this study to evaluate the histopathological characteristics of in vivo thrombi retrieved from acute ischemic stroke patients resistant to IV rt-PA prior to endovascular treatment. Methods: The thrombus was removed from the device or retrieval catheter by gentle disassociation and processed for paraffin section preparation and hematoxylin and eosin (H&E) staining. Each slide was reviewed by an independent pathologist and classified as RBC dominant, fibrin dominant, and mixed based on the content. The characteristics were compared with thrombi retrieved from IV rt-PA naïve patients. Results: Thrombi were retrieved from a total of 19 patients (mean age±SD; 73.4 ±14.8 years) who underwent mechanical thrombectomy. IV rt-PA resistant thrombi were retrieved in 9 of 19 patients with a time interval (min±SD) between IV rt-PA initiation and thrombus retrieval of 174±48 mins. The IV rt-PA resistant thrombi were characterized as: RBC dominant (n=4), fibrin dominant (n=2), and mixed (n=3). The proportion of mixed thrombi were lower in those who did and who did not receive IV rt-PA prior to endovascular treatment (3 of 9 versus 5 of 10, p=0.2). The rates of partial or complete recanalization were similar between RBC dominant (8 of 9), fibrin dominant (2 of 2), and mixed thrombi (8 of 8, p=0.5). The time interval between symptom onset and thrombus retrieval was 349±98 min±SD for RBC dominant, 242±15 (min±SD) for fibrin dominant, and 456±313 (min±SD) for mixed thrombi (p=0.3). Conclusions: In our preliminary observations, we did not find any differences in histomorphology of IV rt-PA resistant and naïve thrombi in acute ischemic stroke patients.