Abstract 4: Excellent Collaterals in STAR: Minimal Infarct Core Trumps the Degree of Hypoperfusion

Background: Collateral grade on DSA before acute endovascular therapy of stroke predicts revascularization. Excellent collaterals were a potent predictor of good clinical outcomes at 90 days after treatment in Solitaire Flow Restoration Thrombectomy for Acute Revascularization (STAR). We studied whether excellent collaterals could be detected with either CT or MR perfusion imaging acquired immediately before treatment. Methods: Independent angio and CT/MRI core labs analyzed baseline DSA ASITN/SIR collateral grade and CT/MR perfusion imaging volumes (equivalent definitions of infarct core and Tmax > 4, 6, 8, 10, 12, 14 s). Hypoperfusion was defined as Tmax > 6s, with Tmax hypoperfusion intensity ratios of 10/6 and 14/6, and target and malignant profiles based on DEFUSE-2. Excellent collateral grade (3-4) was analyzed by pretreatment CT/MRI patterns. Results: 64 of 202 cases in STAR (mean age 67.9 ± 13.1 years; 53% women; median baseline NIHSS 15 (8-25)) had CT/MR perfusion volumes and ASITN/SIR collateral grade analyzed. Distribution of collateral grade (0, n=2; 1, n=31; 2, n=14; 3, n=15; 4, n=2) was similar to the entire STAR population. Excellent collaterals were unrelated to age and gender, with a trend towards lower NIHSS (OR 0.9, p=0.12). Excellent collaterals in 17/64 (27%) demonstrated very small core volumes (0 cc, n=8; 1-25 cc, n=8; > 25 cc, n=1) compared to other cases. Similarly, clinical-core mismatch (defined as baseline NIHSS ≥8-16 and core ≤ 25 cc; baseline NIHSS ≥17 and ≤ 50 cc) was noted in 16/17 (94%). The extent of hypoperfusion (Tmax > 6s) and degrees of hypoperfusion (Tmax 4-14, 10/6, and 14/6) were not related to the presence of excellent collaterals. Target mismatch (n=53/64, 83%) showed an OR 4.32 (p=0.18) for excellent collaterals and no malignant profiles were associated with grade 3-4. Conclusions: CT/MR perfusion patterns prior to endovascular therapy are associated with excellent collaterals, evident as very small infarct core, target mismatch, and clinical-core mismatch. The degree of Tmax hypoperfusion severity alone cannot be used to identify presence of excellent collaterals.