The usefulness of evaluating FDG uptake in right ventricle and in pulmonary fibrotic lesions for monitoring right ventricular function before and after pulmonary transplantation in patients with chronic respiratory failure.

Introduction: Right ventricular failure is one of serious complication due to chronic respiratory failure with pulmonary fibrosis. The lung transplantation is one of curative surgical methods for chronic respiratory dysfunction with right ventricular failure. Few research regarding the course of right ventricular function before and after lung transplantation using FDG-PET have been reported. In the present study, we evaluated the alteration of right ventricular function by monitoring FDG uptake both of right ventricular myocardium and pulmonary fibrotic lesions before and after lung transplantation.

Methods: Eighteen patients who were undergone lung transplantation for the fundamental therapy of chronic refractory pulmonary failure were analyzed. Regard as right ventricular function, we measured right ventricular systolic pressure (RVSP), tricuspid regurgitant pressure gradient (TR-PG) and acceleration time/right ventricular ejection time (Act/ET) by ultrasonic cardiogram (UCG). All patients were done FDG-PETCT before and after lung transplantation and they were divided into 2 groups, according to the presence or absence of FDG uptake of right ventricle. Namely, the right ventricle FDG uptake (RVU)(n=7) and the right ventricle FDG no uptake (NRVU) group (n=11). In the quantitative analyzes by on FDG-PET CT, the ratios of SUV max between right ventricle myocardium and left ventricle myocardium (R/L ratio) were obtained. Myocardial ROIs were set referencing CT anatomical contours. In addition, both lung fibrotic indices namely, Metabolic fibrotic volume (MFV) and Total lung fibrosis (TLF), were obtained by setting ROI of pulmonary fibrotic lesions referencing CT. Quantitative parameters were compared among subgroups before and after pulmonary transplantation.

Results: In the comparison before the transplantation, the RVU group showed significantly higher values in both RVSP (44.6 vs. 29.8) and TR-PG (38.6 vs. 27.1) compared with those of the NRVU group. No statistical significance was noted regarding the value in Act/ET (0.35 vs. 0.39) Similarly, both values of pulmonary fibrotic indices were higher in RVU (MFV90.1 TLF 175.3) compared with those in NRVU (MFV 40.4 TLF 70.0). As for the value of R/L ratio, RVU showed also significantly higher value than NRVU (0.73 vs. 0.32). After the transplantation, FDG right ventricular uptake decreased significantly in the RVU group compared with the value before the transplantation (0.73 vs. 0.18). The values of UCG’s right ventricular parameters significantly improved, RVSP 29.8, TR-PG23.8 and Act/ET was 0.45 in the RVU group. Similarly, pulmonary fibrotic indices using PETCT decreased significantly in the RVU group (MFV0.16 TLF 0.26). As for NRVU group, both MFV 0.12 and TLF0.21 improved significantly but right ventricular function and R/L value did not change significantly.

Conclusions: In chronic respiratory failure due to idiopathic pulmonary fibrosis, both right ventricular FDG uptake and pulmonary fibrosis FDG uptake suggested right ventricular dysfunction before the pulmonary transplantation. In addition, both FDG uptake parameters of right ventricular myocardium and pulmonary fibrosis will useful parameters for monitoring serial changes of right ventricular dysfunction before and after the pulmonary transplantation.