Assessment of lung glucose uptake in patients with systemic lupus erythematosus pulmonary arterial hypertension: a quantitative FDG-PET imaging study.

Abstract

Pulmonary arterial hypertension (PAH) is a recognized complication of systemic lupus erythematosus (SLE-PAH) patients and its lung pathology shares similarity to idiopathic PAH (IPAH) with distinctive inflammatory feature. FDG-PET reports glucose metabolism from both hyperproliferative and inflammatory cellular elements of vascular pathology in PAH. We explored the application of FDG-PET in reporting SLE-PAH pulmonary vascular pathology. Sixty-minute dynamic FDG-PET imaging was applied in 14 SLE-PAH patients, 20 IPAH patients and 10 healthy volunteers. Patlak analysis was used to quantify lung FDG uptake (influx rate Ki). Mean lung FDG uptake in SLE-PAH (Ki 0.00714 ± 0.000602mL/g/min) was significantly higher than that of the healthy volunteers (Ki 0.000262 ± 0.000168mL/g/min) (p < 0.05). SLE-PAH patients with SLE disease activity score SLEDAI ≥ 5 demonstrated significantly increased lung FDG uptake (Ki 0.001075 ± 0.00055mL/g/min) than those with SLEDAI < 5 (Ki 0.000233 ± 0.00017mL/g/min) (p = 0.0038) and IPAH (Ki 0.000524 ± 0.000314mL/g/min) (p = 0.0025). Lung FDG uptake in SLE-PAH correlated with SLEDAI score and plasma complement C3 and C4 levels (Ki vs SLEDAI, r = 0.607, p = 0.021; Ki vs C3, r = -0.568, p = 0.034; Ki vs C4, r = -0.661, p = 0.010). There were no significantly correlations between lung FDG uptake and pulmonary vascular haemodynamics and 6min walking distance in both IPAH and SLE-PAH patients. Our data indicated that increased lung FDG uptake in SLE-PAH patients correlates with SLE disease activity (SLEDAI) and immune/inflammatory status (C3 and C4). FDG-PET imaging may be developed as a potential intrapulmonary disease activity marker in SLE-PAH patients.