18F-FDG SPECT myocardial imaging of right ventricle in patients with idiopathic pulmonary hypertension

Objective To investigate the value of 18F-FDG SPECT myocardial imaging in evaluating haemodynamic change,treatment outcome and prognosis for idiopathic pulmonary arterial hypertension (IPAH).Methods All 24 patients with IPAH underwent 18 F-FDG SPECT myocardial imaging.Right ventricle/left ventricle (RV/LV)-FDG uptake was calculated by ROI method drawing over the central areas of left and right ventricular free walls.All patients underwent right heart catheterization within 3 days after imaging studies.Mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR) were recorded.After six month pharmaceutical treatment,15 IPAH patients were re-examined with 18F-FDG SPECT myocardial imaging followed by repeated right heart catheterization within 3 days.Plasma N-terminal pro-brain naturetic peptide (NT-proBNP) and endothelin-1 ( ET-1 ) were measured in 17 patients using electrochemiluminescent immunoassay and enzyme immunoassay respectively.All patients were followed up for 12 months at least.Correlations between RV/LV-FDG uptake and mPAP and PVR were determined by simple linear regression analysis.Change of RV/LV-FDG before and after treatment was calculated using Student's t-test.Survival in groups with RV/LV FDG uptake ≥ 1.15 and RV/LV-FDG uptake ＜ 1.15 were compared using Log-rank test.Results Significant correlations were found between RV/LV-FDG uptake and mPAP (r =0.562,P ＜ 0.01 ),and between RV/LV-FDG uptake and PVR ( r =0.574,P ＜ 0.01 ).There were no significant correlation between RV/LV-FDG uptake and NT-proBNP( r =0.18 1,P ＞ 0.05 ),but a significant correlation between RV/LV-FDG and ET-1 was observed (r =0.669,P ＜ 0.01 ).The RV/LV-FDG uptake in patients with positive treatment outcome ( n =6) decreased from 1.38 ± 0.52 to 0.92 ±0.26 (t =4.018,P ＜ 0.05) after 6 months treatment.In contrast,no significant change of RV/LV-FDG uptake was seen in those patients (n =9) with negative treatment outcome ( t =1.861,P ＞ 0.05 ).The mean follow-up time was (21 ±8) months.Mean survival time for the patients with RV/LV- FDG uptake ≥ 1.15was 28 months (95％ confidence interval:24-32 months),which was significantly lower than 34 months survival (95％ confidence interval:33-35 months) for the patients with RV/LV-FDG ＜ 1.15 (x2 =3.956,P ＜0.05 ).Conclusions Detection of right ventricle myocardial glucose metabolism level with 18F-FDG SPECT may be a practical method for evaluating haemodynamic change,treatment outcome and prognosis of IPAH. Key words: Hypertension, pulmonary;  Myocardium;  Tomography, emission-computed,single-photon;  Deoxyglucose