Dose-Dependent Association of Inflammatory Cytokines with Carotid Atherosclerosis in Transient Ischaemic Attack: Implications for Clinical Trials

Introduction: The 5-year recurrence risk after ischaemic stroke and transient ischaemic attack (TIA) is 25-30%. Although inflammation may be a target for prevention trials, the contribution of plaque inflammation to acute cerebrovascular events remains unclear. We investigated the association of acute inflammatory cytokines and high-sensitivity C-reactive protein (CRP) with recently symptomatic carotid atherosclerosis in a prospective cohort study. Methods: Blood and Imaging markers of TIA BIO-TIA) is a multicentre prospective study of imaging and inflammatory markers in patients with TIA. Exclusion criteria were infection and other co-morbid illnesses associated with inflammation. CRP and serum cytokines (interleukin [IL]-6, IL-1 beta, IL-8, IL-10, IL-12, interferon-gamma [IFN-gamma] and tumour necrosis factor-alpha [TNF-alpha]) were measured. All patients had carotid imaging. Results: Two hundred and thirty-eight TIA cases and 64 controls (TIA mimics) were included. Forty-nine (20.6%) cases had symptomatic internal carotid artery stenosis. Pro-inflammatory cytokine levels increased in a dose-dependent manner across controls, TIA without carotid stenosis (CS), and TIA with CS (IL-1 beta, p(trend) = 0.03; IL-6, p(trend) < 0.0001; IL-8, p(trend) = 0.01; interferon (IFN)-gamma, p(trend) = 0.005; TNF-alpha, p(trend) = 0.003). Results were unchanged when DWI-positive cases were excluded. On multivariable linear regression, only age (p = 0.01) and CS (p = 0.04) independently predicted log-IL-6. On multivariable Cox regression, CRP was the only independent predictor of 90-day stroke recurrence (adjusted hazard ratio per 1-unit increase 1.03 [95% CI: 1.01-1.05], p = 0.003). Conclusion: Symptomatic carotid atherosclerosis was associated with elevated cytokines in TIA patients after controlling for other sources of inflammation. High-sensitivity CRP was associated with recurrent ischaemic stroke at 90 days. These findings implicate acute plaque inflammation in the pathogenesis of cerebral thromboembolism and support a rationale for randomized trials of anti-inflammatory therapy for stroke patients, who were excluded from coronary trials.