Persistent lung and vascular inflammation in mild to moderate COVID-19 survivors detected by ¹⁸F-FDG PET/CT: A quantitative imaging study with implications for cardiovascular risk.

Abstract

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. 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. 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. 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.