Abstract 76: Collateral Circulation in Endovascular Therapy for Acute Ischemic Stroke: Smaller Strokes, Improved Reperfusion, Less Hemorrhagic Transformation and Better Outcomes

Background: Collateral circulation moderates the impact of acute cerebral occlusion and may influence outcome from recanalization treatment. Noninvasive angiography provides some information on collateral status, but catheter angiography prior to endovascular therapy remains a unique opportunity to verify collateral grade. We conducted a comprehensive study of collaterals in acute anterior circulation occlusion to substantiate previous associations with collaterals and their impact on endovascular stroke therapy. Methods: Consecutive patients undergoing endovascular therapy for acute ischemic stroke due to anterior circulation occlusion were analyzed with respect to collaterals. Collateral grade was assessed with the ASITN/SIR scale on baseline angiography. Univariate and multivariate regression analyses detailed the relationship of collateral grade with clinical, laboratory and imaging parameters. Results: Among 113 patients, mean age was 66.9±17 years, 61.9% were female, and pretreatment NIHSS was median 17 (range 2-38). The proportion of patients in each collateral grade was: 0 - 3.5% 1 - 13.3 %; 2 - 38.9%; 3 - 31%; 4 - 13.3%. Age and gender were not associated with the degree of collateral circulation. Among medical history and laboratory variables, on multivariate ordinal regression, the sole predictor of more robust collaterals was current statin use (b 1.413, p=0.020) and predictors of worse collaterals were history of hyperlipidemia (b -1.872, p=0.001), White population (b -1.361, p=0.007) and higher WBC (b -0.306, p=0.044). More extensive collaterals correlated with smaller baseline DWI lesion volume (b 0.025, p=0.001). Interestingly, angiographic collateral grade did not correlate with PWI lesion volumes for Tmax thresholds at 2, 4, 6, or 8 seconds. More robust collaterals were associated with higher TICI reperfusion rates (ρ 0.191, p=0.043), and lower hemorrhagic transformation rates (ρ -0.229, p=0.015). mRS at discharge inversely correlated with collateral grade (ρ -0.317, p=0.001). Conclusions: The extent of collateral circulation prior to endovascular therapy exhibits a striking impact on achievement of reperfusion, tissue fate and functional outcome. Further research is needed to delineate mechanisms linking statins with better collaterals and biomarkers, such as elevated WBC, for arteriogenesis when collaterals are insufficient.