Abstract W MP23: Effect of Blood Pressure and Collateral Flow on Infarct Growth Rate

Abstract

Objectives: To determine the effect of collateral flow and modifiable risk factors on infarct growth rate. Methods: Consecutive acute ischemic stroke patients admitted with witnessed-onset involving middle cerebral artery (MCA) stem (M1) occlusions underwent brain MRI before intra-arterial therapy. Admission CT angiography was graded for regional leptomeningeal collateral score (rLMC) and infarct volume was measured on diffusion-weighted MRI, both blinded to clinical data. Infarct growth rate was estimated as the ratio between admission infarct volume and time from symptom onset to MRI. Multivariable analysis was performed adjusting for age, sex, vessel occlusion location, smoking and arterial fibrillation. Results: We studied 98 patients over a 10-year period, age 66 +/- 17, median NIH Stroke Scale of 16. Most (36%) patients had isolated M1 occlusions, followed by M1/M2 segment occlusions (34%), M1/distal internal carotid (17%) and M1/distal carotid + anterior cerebral artery occlusions (12%). In the multivariable model, only admission systolic blood pressure (SBP) was significantly associated with infarct growth rate (6.3% lower infarct growth rate for every 10mmHg increase in SBP, 95% confidence interval = 0.3-12.1%, p=0.038). Collateral flow was associated with infarct growth rate among normotensive individuals (13% decrease in infarct growth rate for every 1 point increase in rLMC, 95% confidence interval = 3-23%, p=0.012), but not hypertensive individuals (p=0.019 for interaction). Conclusions: Infarct growth behavior is different between hypertensive and normotensive individuals. While acute high blood pressure is associated with decreased infarct growth rate in both groups, better collateral flow only limits infarct growth in normotensive individuals.