Wideman, Brian

Background: CT perfusion (CTP) imaging is an important tool for identifying candidates for mechanical thrombectomy (MT). This modality is increasingly available in regional facilities, but whether pre-transfer perfusion imaging studies may be relied upon for treatment decisions is unclear. We analyzed a cohort of stroke transfers to quantify changes in CTP imaging profiles over time. Methods: A cohort of confirmed ischemic stroke patients who received CTP before and after transfer to a large mid-western comprehensive stroke center (CSC) were identified. We compared perfusion mismatch (MM), core infarct volume (CIV), and favorability of imaging for mechanical thrombectomy (MT) candidacy (defined as the presence of LVO and MM/CIV ratio of >1.8) between studies. Regression models were used to examine predictors of CIV growth including hypoperfusion intensity ratio (HIR) and time between studies. Results: Over a 24-month period, 61 patients met inclusion criteria. Median age was 71 (IQR 60-80), 52% were female, median NIHSS was 14 (IQR 4-19), and most patients had occlusion of the internal carotid and/or middle cerebral arteries (77%). The median time from last known well (LKW) to initial CT was 148 minutes (IQR 71-620) and median time between imaging studies was 149 minutes (IQR 126-194). Median CIV growth was 0 mL (IQR 0-6) and 8% (5/61) had growth ≥25 mL. In linear regression, higher HIR predicted CIV growth (β=24.3, p=0.04), but time from LKW to presentation and time between imaging studies did not. Imaging studies taken at the regional and CSC sites demonstrated excellent agreement in classifying patients as candidates for MT (kappa 0.778 [95% CI: 0.611-0.944]). A favorable regional CTP profile was 93% sensitive for MT delivery at the CSC with a positive predictive value of 63%. Conclusion: In our cohort, CIV growth between facilities was minimal despite relatively long interfacility transport times and was predicted by the regional HIR. A favorable regional imaging profile demonstrated high agreement with the imaging result at the CSC and was strongly associated with MT treatment.

Background: Large vessel occlusion (LVO) stroke patients are often transferred from regional hospitals to comprehensive stroke centers (CSC) for thrombectomy. The need for repeat imaging at CSCs prior to intervention is unclear. We compared regional hospital and CSC perfusion imaging results for interfacility transfers in a single health system. Methods: We analyzed a cohort of patients in western Michigan who received CT perfusion imaging before and after transfer to a CSC. Perfusion mismatch (MM), core infarct volume (CIV), and favorability of imaging for mechanical thrombectomy (MT) candidacy were compared between the regional and CSC studies. A favorable imaging profile was defined as the presence of LVO, MM volume >10 mL, and MM/CIV ratio of >1.2. Linear regression was used to examine predictors of infarct growth during transfer. Results: Over a 10-month period, 25 patients met inclusion criteria. The median age was 76 (IQR 66-81), 60% were male, median NIHSS was 11 (IQR 2-18), and most patients had occlusion of the internal carotid or middle cerebral arteries (72%). The median time from last known well to initial CT was 250 minutes (IQR 85-620). Regional median MM volume was 52 mL (IQR 8-97), CIV was 0 mL (IQR 0-13), and hypoperfusion intensity ratio (HIR) was 0.25 (IQR 0-0.34). The median time between CTs was 152 minutes (IQR 139-226). The median change in MM volume was -3 mL (IQR -27-3) and median CIV growth rate was 0 mL/hr (IQR 0-2.0). In a multivariable regression model, higher HIR (β=23.2, p=0.012) and minutes between imaging studies (β=0.10, p=0.021) were associated with CIV growth. Sixteen patients (64%) had favorable imaging profiles for MT at the regional hospital. Of these, 15 (93.8%) continued to have a favorable CSC imaging profiles and 9 (56.2%) underwent MT. Of the 9 patients without favorable regional imaging profiles, 1 (11.1%) had a favorable CSC imaging profile and 2 (22.2%) underwent MT. Conclusion: In our sample, regional and CSC perfusion imaging patterns were similar and patients infrequently crossed thresholds for MT candidacy between studies. Initial HIR and longer delays between were independently associated with infarct growth during transfers, however overall infarct growth was very small.