Routine CBC-Derived Markers of Systemic Inflammation Are Associated With Growth of the Dilated Ascending Aorta During CT Surveillance

Background: Ascending aortic surveillance relies on diameter thresholds, yet most dissections occur below them. Inflammation drives aortic wall remodeling independent of diameter. Inflammation drives aortic wall remodeling independent of diameter. Inflammatory indices derived from routine blood counts, such as neutrophil-to-lymphocyte ratio (NLR), red cell distribution width (RDW), and systemic immune-inflammation index (SII) have been show to predict adverse cardiovascular outcomes, but their association with ascending aortic growth is unclear. Methods and Results: We retrospectively studied adults with 2 computed tomography (CT) scans of the native ascending aorta 6 months apart at a single center (2000-2023), excluding those with aortitis or no complete blood count during follow-up. Markers were summarized as 95th percentile values per patient and per scan interval. Growth was defined as a 2-mm increase in mid-ascending aortic diameter. Patient-level logistic regression and interval-level generalized estimating equation models were adjusted for age, sex, body mass index, baseline diameter, systolic blood pressure, diabetes, and heritable thoracic aortic disease. Among 3,262 patients, data were available in 1,882 for RDW, 1,471 for NLR, and 1,468 for SII; 192 (10.2%) met criteria for growth. Only RDW was independently associated with growth in the overall cohort (patient level: odds ratio [OR] 1.071, 95% CI 1.002-1.144, p=0.043; interval level: OR 1.075, 95% CI 1.012-1.141, p=0.019); NLR (p=0.080) and SII (p=0.164) were not. Among patients with guideline-defined ascending aortic dilation (40 mm), all three markers were associated with interval growth (RDW OR 1.14, NLR OR 1.05, SII OR 1.01 per 100 units; all p 0.014), whereas none were among aortas <40 mm; effect modification was significant for NLR (p=0.01). Conclusions: RDW was modestly associated with ascending aortic growth overall, and all three markers were associated with interval growth in patients with guideline-defined aortic dilation, suggesting that systemic inflammation may contribute to progression of aortic dilation. Prospective studies with more specific inflammatory markers are needed.