Abstract P509: Signal Intensity in the Middle Cerebral Artery as a Practical and Feasible Index of Hemodynamic Insufficiency Due to Carotid Artery Stenosis
Introduction: Intracranial hemorrhage occasionally occurs after carotid revascularization in presents with hemodynamic insufficiency. Positron emission tomography is unavailable in most facilities, and a feasible index is required to identify high-risk patients. Reduced signal intensity (SI) of the middle cerebral artery (MCA) on magnetic resonance angiography (MRA) is associated with postoperative hyperperfusion. Hypothesis: Reduced signal intensity (SI) of the MCA on MRA is associated with decreased regional cerebral blood flow (rCBF) on single-photon emission CT (SPECT) and increased blood-sampling whole-brain oxygen extraction fraction (wb-OEF). Methods: We included patients who: 1) were admitted from 2015 to 2019 for carotid artery stenting (CAS), 2) MRA, and SPECT before CAS, and 3) examined the wb-OEF immediately before CAS. We measured bilateral MCA SI on MRA and defined the MCA relative SI as (SI in the affected MCA)/ (SI in the contralateral MCA). We defined the rCBF% as rCBF in the affected MCA territory against the ipsilateral cerebellum. Before CAS, we sampled blood, measured the arterial oxygen and the venous oxygen content in the dominant-sided jugular vein, and calculated the wb-OEF. We evaluated the correlation between the MCA relative SI, the MCA slow flow, the rCBF%, and the wb-OEF. We estimated the upper limits of the MCA relative SI for the rCBF% < 80% or wb-OEF ≥ 0.40 using the area under the curve (AUC) values derived from the receiver operating characteristic (ROC) curves. Results: During the study period, 150 patients met our inclusion criteria. The MCA relative SI was positively correlated with rCBF% and negatively with the wb-OEF. The ROC curve for the rCBF% < 80% showed that the upper limit of the relative SI was 0.77 (the sensitivity of 53.9%, the specificity of 83.9%, AUC of 0.723). The ROC curve for the wb-OEF ≥ 0.40 showed that the upper limit of the relative SI was 0.95 (the sensitivity of 67.7%, the specificity of 55.2%, AUC of 0.625). Conclusion: Reduced MCA SI on MRA ≤ 0.77 is a practical and feasible index of hemodynamic insufficiency, indicating the decreased rCBF and increased wb-OEF.