Abstract 3773: The Impact Of Reperfusion On Vasogenic Edema Following Middle Cerebral Artery Occlusion In Experimental Ischemia

Abstract

Objective: In order to assess the impact of reperfusion on the degree of subsequent cerebral edema following cerebral ischemia, this work sought to compare 24 hour infarct volume progression between permanent and transient middle cerebral artery occlusion (MCAO) in a canine model. Methods: Using a previously published endovascular transient MCAO method, 5 mongrel canines underwent 1-hour transient MCAO and 5 underwent permanent MCAO. Model parameters were altered to result in varying infarct volumes. Magnetic resonanace imaging (MRI) (3T Achieva, Philips) was performed one hour and 24 hours following reperfusion as well as 60 minutes following permanent occlusion. Infarct volumes were calculated using a previously published threshold technique by two observers using 1 hour mean diffusivity (MD) maps and 24hour FLAIR MRI. Reproducibility was assessed using Bland-Altman statistic. Average infarct volumes between the observers were calculated. Bivariate linear fit analysis were used to assess the correlation between immediate and 24 hours infarct volume determinations. Results: R square (r2) for linear fit was 0.964 (p=0.0005) for permanent occlusion and 0.971 (p= 0.0022) for transient occlusion ( figure 1 ). The infarct volumes measured at 1 hour increased by a factor of 1.42 relative to 24 hour infarct volumes for permanent occlusion and 2.05 for transient occlusion. Bland-Altman statistic indicates that reproducibility using the MD maps (15.9%) and FLAIR images (13.3%) is not substantially different. None of the animals demonstrated hemorrhagic conversion by 24 hours. Conclusion: MD maps generated one hour post reperfusion following transient and permanent MCAO in a canine model can serve as a reliable assessment for infarct volume determination. Increase in infarct volume at 24 hours, presumably due to vasogenic edema, was greater in reperfused infarctions than with permanent occlusion. Figure 1: Bivariate linear fit analysis comparing immediate and 24-hour infarct volume calculations for permanent and transient occlusions.