Persistent Pulmonary and Vascular Inflammation After Mild–Moderate COVID-19 Detected by ¹⁸F-FDG PET/CT

18F-FDG PET/CT shows persistent metabolic activity in the lungs and arterial walls months after mild–moderate COVID-19, identifying a subgroup that may merit closer cardiovascular surveillance. The signal comes from community‑managed survivors scanned a median 97 days (IQR 77–112.5) after symptomatic recovery.

That observation prompted a quantitative cohort analysis of 59 recovered individuals versus eight COVID‑naive controls that specifically reported persistent pulmonary inflammation. The control arm was small (n=8), which limits precision and the generalisability of between‑group comparisons.

Quantitatively, SUVmax and TBRmax were the most sensitive lung metrics in this cohort, with mean values above typical physiological ranges. Patterns were heterogeneous—often subpleural and posterior–basal—and focal SUVmax peaks were more discriminatory than averaged measures (SUVmean or TBRmean). Vascular inflammation was assessed by thoracic aorta TBRmax and an MDS TBRmax normalized to right‑atrial blood‑pool SUVmean. For post‑COVID PET/CT reporting, highlight contracted‑lung SUVmax, per‑lung TBRmax and the TLGindex as the primary metrics to record and communicate.

Correlation analyses identified a consistent, positive association between lung and arterial uptake without implying causation: total thoracic aorta TBRmax correlated with RLC TBRmax (ρ = 0.44, p<0.001) and with several lung TBR/TLG indices (ρ ≈ 0.30–0.47, all p<0.05). This pattern supports a parallel systemic inflammatory signal—plausibly reflecting endothelial activation and endothelitis—mechanisms that can promote atherogenesis and thrombogenic dysfunction. Notably, CRP levels were low and did not reliably track PET metrics, indicating that imaging‑detected inflammation may be subclinical. Taken together, the imaging–vascular correlations link persistent pulmonary metabolic activity to a potential increase in cardiovascular vulnerability.

In practice, PET/CT is likely most informative when selective: target cardiovascular risk assessment to patients with persistent respiratory symptoms, unexplained systemic inflammation, or elevated biomarkers rather than scanning all survivors. When PET is obtained, integrate PET metrics with CT structural assessment and conventional testing (echocardiography, biomarkers) to prioritize downstream work‑up; reserve CT or echocardiography when the clinical question is anatomical or functional rather than metabolic. Important evidence gaps remain—this is cross‑sectional data with limited controls and no causal demonstration—so PET‑detected inflammation should prompt closer surveillance or trial enrollment rather than immediate, widespread therapy. Selective PET/CT can inform risk stratification while underscoring the need for longitudinal outcome data.