Abstract TP91: Unfavorable Baseline Hypoperfusion Intensity Ratio is Associated With Infarct Growth and Poor Outcome in Patients With Distal MCA Occlusions

Abstract

Background: A low hypoperfusion intensity ratio (HIR) predicts good collateral vessel status and correlates with infarct growth and functional outcome in early window patients with proximal large vessel anterior circulation occlusions. Its performance in predicting clinical and radiologic outcome has not been assessed in patients with more distal occlusions. In this retrospective analysis of the CT Perfusion to Predict Response to Recanalization in Ischemic Stroke (CRISP) study, we hypothesized that a favorable baseline HIR would predict less infarct growth in patients with distal middle cerebral artery (MCA) occlusions. Methodology: Patients with occlusions of an M2 or M3 branch of the MCA on catheter angiography were included; all patients underwent mechanical thrombectomy with TICI2B/3 reperfusion. Baseline ischemic core volume and HIR (Tmax >10s / Tmax >6s) were assessed with RAPID software; late follow-up infarct volumes (>36 hours from initial CT perfusion) were manually determined from DWI MRI. Excellent functional outcome was defined as a modified Rankin score of 0-1. Results: Fourteen patients with baseline perfusion and late follow-up imaging were included; nine patients presented with M2 occlusions, and 5 with M3 occlusions. The mean baseline HIR of 0.48 was used to dichotomize patients into favorable or unfavorable baseline profiles. Patients with a favorable baseline HIR had significantly smaller baseline ischemic core volumes (0 mL [IQR 0-3.3] vs. 14.0 mL [IQR 8.7-22.1], p=0.01), smaller final infarct volumes (16.1 mL [IQR 12.7-41.2] vs. 71.4 mL [IQR 43.8-113.5], p=0.01) and less infarct growth (16.1 mL [IQR 9.4-31.9] vs. 49.0 mL [IQR 31.1-100.8], p=0.03). Excellent functional outcome was achieved in 6/6 (100%) of those with favorable baseline HIR, versus 3/8 (37.5%) with unfavorable baseline profile (p=0.03). Conclusion: In patients with distal MCA occlusions, poor collateral status at baseline as demonstrated by a high HIR score is associated with more infarct growth and worse clinical outcomes. HIR may be helpful for guiding thrombectomy decisions in patients with distal occlusions and warrants further prospective study in this population.