Admission Blood Pressure Modifies the Perfusion Collateral Impairment Score and Outcome in Anterior Circulation Large Vessel Occlusion Stroke

<h3>BACKGROUND AND PURPOSE:</h3> The Perfusion Collateral Impairment Score (PCIS), a 3-component perfusion metric, is an ordinal composite correlated with 90-day outcome in large vessel occlusion (LVO) stroke. It remains unclear whether admission blood pressure is an interaction factor. <h3>MATERIALS AND METHODS:</h3> We studied 245 patients with acute anterior circulation LVO and an admission NIHSS &gt; 5, from two hospitals within one health system. We calculated average admission diastolic blood pressure (DBP) and mean arterial pressure (MAP) from a minimum of three measurements taken within the first 2 hours. The PCIS interaction with DBP or MAP on 90-day outcome (mRS 3-6) was tested in an adjusted model using the likelihood ratio test. <h3>RESULTS:</h3> One hundred thirty-eight (56.3%) patients had an unfavorable outcome (mRS 3–6). The interaction was most apparent at the severe-disability end (mRS 4–6), with higher admission DBP and MAP producing a steeper slope relating PCIS to outcome (DBP OR, 1.54; 95% CI, 1.07–2.21; MAP OR, 1.60; 95% CI, 1.11–2.32). Odds ratios were above 1.0 at every outcome level, and the predicted-probability difference between low and high PCIS widened from 11% to 39% with increasing DBP. At the primary threshold (mRS 3–6) the interaction was directionally consistent but did not reach significance (DBP OR, 1.40; <i>P</i> = .048; MAP OR, 1.34; <i>P</i> = .09) and did not survive correction for multiple comparisons. No interaction was seen between PCIS and NIHSS. <h3>CONCLUSIONS:</h3> The primary interaction at mRS 3–6 did not reach significance after adjustment. Nonetheless, the association of PCIS with 90-day outcome after anterior circulation LVO stroke may be modified by admission blood pressure, especially in the subset with severe outcomes, independent of admission clinical deficit. Admission pressure may enhance interpretation of PCIS rather than act as a predictor itself, and the relationship requires prospective, externally validated study before clinical translation.