Abstract 5: Dynamic Perfusion Assessment of Collateral Blood Flow in MCA Occlusion as Indicator of Tissue Fate

Abstract

Objective: M1 occlusions with concomitant large cortical infarcts can result in life long severe disabilities. Therapeutic decisions for iv thrombolysis only or bridging to endovascular treatment require sufficient information of collateral flow. Hence, we tried to evaluate the potential of dynamic perfusion in the assessment of collateral flow with respect to tissue fate and outcome. Method: Between 1/2009 until 1/2012 ninety patients with MCA infarcts due to M1 occlusions were examined in a 3 T MR scanner. Selection criteria were DWI, PI, MR angiography, NIHSS on admission; FLAIR, MR angiography day 6 and mRS day 90, which left 30 patients for further evaluation. For evaluating dynamic perfusion the second previous image was subtracted from each frame of the raw perfusion data and the final images were assessed according to Higashida′s scale (Stroke 2003;34: e109-37). Rapid collateral flow was defined as arrival of signal drop in the ischemic side before the last arterial phase signal in the unaffected side. The ischemic region was monitored for complete or incomplete filling and flow direction. Results: Collateral flow was inversely correlated with infarct size on day 1 (p=0.005) and day 6 (p=0.006) as well as infarct growth (p=0.025) indicating collateral flow can influence infarct development. Collateral grade was significantly better in proximal M1 occlusions than in distal ones (p<0.001), however the capillary filling was significantly delayed (p<0.001). Mismatch volume was found to directly correlate with the delay of capillary filling (p=0.015) but not with infarct growth (p=0.064) or infarct size on day 6 (p=0.15). Higher NIHSS was directly correlated with capillary delay (p=0.042) and inversely correlated with collateral grade (p=0.027). mRS at day 90 correlated inversely with collateral grade (p=0.027), directly with infarct size on day 1 (p=0.006) and day 6 (p=0.011) demonstrating good collateral flow beneficial for tissue survival. Conclusion: Dynamic perfusion can provide additional information of collateral flow and capillary delay, which showed strong associations with infarct size and infarct growth, as well as clinical scores, such as NIHSS and mRS at follow-up. It can add to the assessment of tissue fate before therapy decision.