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

Background and Objectives

To determine whether carotid plaque inflammation identified by 18F-fluorodeoxyglucose (18FDG)-PET is associated with late (5-year) recurrent stroke.

Methods

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 (SUVmax) 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.

Results

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 SUVmax 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, p = 0.02 per 1–g/mL increase in SUVmax). 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, p = 0.001).

Discussion

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.

Classification of Evidence

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.

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