Carotid Plaque Inflammation Imaged by PET and Prediction of Recurrent Stroke at 5 Years

Abstract

<h3>Background and Objectives</h3> To determine whether carotid plaque inflammation identified by ¹⁸F-fluorodeoxyglucose (¹⁸FDG)-PET is associated with late (5-year) recurrent stroke. <h3>Methods</h3> We did an individual-participant data pooled analysis of 3 prospective studies with near-identical study methods. Eligible patients had recent nonsevere (modified Rankin Scale score ≤3) ischemic stroke/TIA and ipsilateral carotid stenosis (50%–99%). Participants underwent carotid ¹⁸FDG-PET/CT angiography ≤14 days after recruitment. ¹⁸FDG uptake was expressed as maximum standardized uptake value (SUV_max) in the axial single hottest slice of symptomatic plaque. We calculated the previously validated Symptomatic Carotid Atheroma Inflammation Lumen-Stenosis (SCAIL) score, which incorporates a measure of stenosis severity and ¹⁸FDG uptake. The primary outcome was 5-year recurrent ipsilateral ischemic stroke after PET imaging. <h3>Results</h3> Of 183 eligible patients, 181 patients completed follow-up (98.9%). The median duration of follow-up was 4.9 years (interquartile range 3.3–6.4 years, cumulative follow-up period 901.8 patient-years). After PET imaging, 17 patients had a recurrent ipsilateral ischemic strokes at 5 years (recurrence rate 9.4%, 95% confidence interval [CI] 5.6%–14.6%). Baseline plaque SUV_max independently predicted 5-year ipsilateral recurrent stroke after adjustment for age, sex, carotid revascularization, stenosis severity, NIH Stroke Scale score, and diabetes mellitus (adjusted hazard ratio [HR] 1.98, 95% CI 1.10–3.56, <i>p</i> = 0.02 per 1–g/mL increase in SUV_max). On multivariable Cox regression, SCAIL score predicted 5-year ipsilateral stroke (adjusted HR 2.73 per 1-point increase, 95% CI 1.52–4.90, <i>p</i> = 0.001). <h3>Discussion</h3> Plaque inflammation–related ¹⁸FDG uptake improved identification of 5-year recurrent ipsilateral ischemic stroke. Addition of plaque inflammation to current selection strategies may target patients most likely to have late and early benefit from carotid revascularization. <h3>Classification of Evidence</h3> This study provides Class I evidence that in individuals with recent ischemic stroke/TIA and ipsilateral carotid stenosis, carotid plaque inflammation–related ¹⁸FDG uptake on PET/CT angiography was associated with 5-year recurrent ipsilateral stroke.