Abstract
PURPOSE: Lingering inflammation after COVID-19 has been proposed as a contributor to long-term cardiovascular risk, yet the link between pulmonary and vascular inflammation remains insufficiently defined. This study aimed to quantify residual lung and vascular inflammation in individuals recovered from mild-to-moderate COVID-19 using ¹⁸F-FDG PET/CT and assess their association. METHODS: Fifty-nine participants underwent ¹⁸F-FDG PET/CT imaging at a median of 97 days (IQR: 77-112.5) following clinical recovery from COVID-19. Lung inflammation was assessed using standardised uptake value maximum (SUV(max)), target-to-background ratio maximum and mean (TBR(max), TBR(mean)), and total lung glycolysis (TLG) in contracted lung volumes to reduce spill-in from mediastinal structures. Metrics were indexed to blood pool activity (TBR) and lung volume (TLG(index)). Vascular inflammation was evaluated using TBR(max) values of the thoracic aorta and the most diseased segment (MDS). Results were compared with eight COVID-naive individuals using identical protocols. RESULTS: Compared with controls, individuals post-COVID-19 exhibited significantly elevated SUV(max) in both lungs (p < 0.001), TBR(max) in the left (p = 0.037) and right (p = 0.010) lungs, and TLG in the left lung (p = 0.018). Measures of vascular inflammation correlated significantly with TBR(max), TBR(mean), and TLG(index) in both lungs (all p < 0.05), suggesting a parallel inflammatory response. CONCLUSION: Persistent pulmonary inflammation is evident following mild-to-moderate COVID-19 and is associated with increased vascular inflammation. These findings suggest a mechanistic link between post-infectious lung and vascular inflammation, potentially contributing to elevated cardiovascular risk. ¹⁸F-FDG PET/CT enabled sensitive detection of subclinical inflammation in both compartments, highlighting the value of quantitative PET metrics in elucidating systemic inflammatory response following viral infection.