Reduced lung uptake of iodine-123 metaiodobenzylguanidine in high-altitude pulmonary oedema

Background and objective: Iodine-123 metaiodobenzylguanidine (I-123-MIBG) uptake in the lungs is a potentially suitable marker of pulmonary endothelial function because MIBG behaviour in the pulmonary circulation is quantitatively similar to that of norepinephrine. In addition, hypoxia reduces I-123-MIBG transport in pulmonary endothelial cells in vitro. The present study was undertaken to evaluate I-123-MIBG uptake in the lungs of patients with high-altitude pulmonary oedema (HAPE). Methods: I-123-MIBG scintigraphy was performed in eight patients with HAPE. The findings were compared with those in 24 patients with congestive heart failure due to idiopathic dilated cardiomyopathy (DCM) and in 13 normal control subjects. In patients with HAPE, the I-123-MIBG examination was performed 7-14 days after admission. Anterior planar images were acquired 15 min after injection of I-123-MIBG and the total lung to upper mediastinum ratio (L/M ratio) was calculated for both lungs. Results: The L/M ratio in patients with HAPE (1.39 +/- 0.15, mean +/- SD) was significantly lower than in those with congestive heart failure/DCM (1.66 +/- 0.16) or in normal controls (1.53 +/- 0.14). There were no significant differences among the groups in I-123-MIBG accumulation in the heart. Conclusions: Although the mechanism of altered I-123-MIBG kinetics in HAPE remains obscure, decreased I-123-MIBG uptake in the lungs may potentially be a suitable technique for the assessment of pathological conditions associated with the pulmonary endothelium.