Abstract TP72: Should Hypoperfusion Intensity Ratio Influence Patient Selection for Mechanical Thrombectomy?

Abstract

Background: Current data utilizes clinical-radiographic mismatch (core and mismatch ratio) as patient selection criteria for mechanical thrombectomy in LVO. High HIR (Hypoperfusion Intensity Ratio) is known to correlate with core size, infarct growth and outcome though influence on patient selection has not been yet determined. Hypothesis: Patients with High HIR and malignant profile (Tmax >10s greater than 50% of penumbra) indicative of fast growing infarct may influence final clinical outcome irrespective of reperfusion. Methods: We retrospectively identified all AIS patients with LVO who underwent CTP imaging between January and June2018 within 24 hours from symptom onset. Demographics, CTP imaging variables, reperfusion status and outcomes (discharge NIHSS and mRS) were analyzed. HIR was dichotomized by proportion of greater and less than 0.5 into malignant vs favorable profile. Association with core size, infarct growth velocity, reperfusion (defined as TICI 2b or 3) and impact on outcomes was analyzed using Wilcoxon Ranked Sum tests for the (skewed) continuous and ordinal variables; chi-square test of proportion were used for categorical variables. The independent contribution of HIR and reperfusion predicting the major outcomes was assessed with logistic regression. Results: A total of 67 patients with LVO were identified with a median age of 78 (IQR 62-87), NIHSS of 16 (IQR 11-21) and time from last seen normal to CT 404 minutes (IQR 113-734). Five patients were excluded due inadequate CTP data. Patients with high HIR (n=23) had a higher core size (median 39 cc; IQR 16-73) compared to 0 cc (IQR 0-12) than patients with low HIR (n=39; median 0; IQR 0-12) (p=<0.001) and faster Infarct growth rate 14.8 cc/hr (IQR 3.6-29.7) vs. 0 cc/hr (IQR 0-1.12) (p=<0.001). After adjusting for reperfusion, median discharge NIHSS was not significantly different (p=0.22) in groups with low vs high HIR, however in-hospital mortality differed (p=0.02). Conclusion: Higher HIR and malignant profile is associated with larger index core size and faster growth rate. However, the influence of this profile on clinical outcomes after recanalization is yet to be established. Ongoing studies evaluating the utility of HIR on patient selection for thrombectomy are needed.