Abstract T P297: Arterial Spin Labeled MRI Quantifies Cerebral Blood Flow Changes with Blood Pressure from Acute to Subacute Stroke

Abstract

Background: Hemodynamic interventions, such as blood pressure (BP) manipulation, are often utilized to optimize perfusion of the ischemic territory. Scant data support theoretical effects of permissive hypertension or BP reduction, yet arterial-spin labeled (ASL) MRI may chronicle quantitative cerebral blood flow (CBF) changes. We used serial ASL to measure CBF changes associated with hemodynamic interventions, based on arterial occlusion site and collaterals. Methods: Serial ASL acquired in 148 consecutive cases of acute ischemic stroke at a single center during a 3-year period. A pseudo-continuous ASL pulse sequence with background suppressed 3D GRASE (gradient and spin echo) readout with 4 post-labeling delays was used, with normalization of quantitative CBF on a standard neurovascular template. CBF values and relative changes were measured in the affected hemisphere and in discrete regions of infarct core and collateral territories. Results: 148 cases (median age 68 years (IQR 62-82), 73 women) were studied. Overall, CBF (ml/100g/min) was related to age (r=-0.40, p<0.001) but not gender (male: 39±9.7, female: 40.6±8.2; r=.05, p=NS). Serial studies were obtained in 126 cases, including 2 studies in 91, 3 in 32, and 4 in 3. Median time to 1 st , 2 nd , 3 rd , and 4 th ASL study was 11.3, 39.7, 140.7, and 121.3 hrs and median CBF at these timepoints was 39.9 (IQR 28-48); 42.2 (IQR 29-52); 47.1 (IQR 36-56); and 35.6 (IQR 34-41). Average changes in CBF from study 1 to 2, 2 to 3, 3 to 4 were +2.2; +3.4; -14.8. Average CBF ratio between leptomeningeal and perforating MCA regions was 1.1. The correlation of initial delta CBF (study 1 to 2) with initial delta BP (1 to 2) was r=-0.1, p=NS. Average delta CBF/delta mmHg SBP was 0.25. At studies 1 and 2, lower BP was related to higher CBF (r=-0.148, p=0.102). Overall, delta BP was not linked with CBF (r=0.002, p=NS) or delta CBF (r=-0.108, p=NS). For those with low initial CBF (<40), positive delta BP was strongly associated with lower CBF at study 2 (r=-0.552, p=0.006). Conclusions: Blood pressure modification, permissive or interventional, may differentially affect CBF in the ischemic core and collateral regions. ASL provides a novel method for non-invasive mapping of serial changes in absolute CBF quantification in the ICU and beyond.