Impairment of Iodine-123-Metaiodobenzylguanidine (I-MIBG) Uptake in Patients with Pulmonary Artery Hypertension.

According to recent studies, lung uptake of iodine-123-metaiodobenzylguanidine (I-MIBG) is impaired in many lung diseases and low lung uptake of I-MIBG suggests endothelial dysfunction of the pulmonary artery. I-MIBG scintigraphy in patients with pulmonary hypertension (PH) has not yet been clinically evaluated. We hypothesized that the lung uptake of I-MIBG is reduced in patients with PH and differs among PH subtypes. The purpose of the present study was to analyze the lung uptake of I-MIBG in patients with PH and compare it with the data obtained by echocardiography or right heart catheterization. I-MIBG scintigraphy was performed in 286 consecutive patients from 2003 to 2014. We enrolled 21 patients with PH and 8 control patients. The 21 patients with PH were categorized into those with pulmonary artery hypertension (PAH, n = 12) and those with chronic thromboembolic pulmonary hypertension (CTEPH, n = 9). The mean pulmonary artery pressure was not significantly different between patients with CTEPH and PAH (37.7 ± 6.8 versus 32.3 ± 5.3 mmHg respectively; P = 0.054). There were no significant differences in any other hemodynamic parameters between the two groups. The lung uptake of I-MIBG in PAH patients (early image: 1.54 ± 0.18, delayed image: 1.41 ± 0.16) was significantly lower than that of CTEPH patients (early image: 2.17 ± 0.25, P < 0.0001; delayed image: 1.99 ± 0.20, P = 0.0001, adjusted for age and World Health Organization classification) and controls (early image: 2.32 ± 0.27, P = 0.0007; delayed image: 1.92 ± 0.19, P = 0.0007). In conclusion, we found for the first time that the lung uptake of I-MIBG in patients with PAH is lower than that in patients with CTEPH and controls.