The impact of specific pulmonary arterial hypertension therapy on cardiac fluorodeoxyglucose distribution in PET/MRI hybrid imaging–follow-up study

BACKGROUND: PET/MRI hybrid imaging in pulmonary arterial hypertension (PAH) provides important prognostic information identifying patients who might benefit from early therapy escalation, as right ventricle (RV) metabolic alterations are linked with hemodynamics and might precede clinical deterioration. Now, we hypothesize that adequate PAH therapy escalation may result in reversal of unfavourable increased glucose uptake of RV, which is associated with improved prognosis. METHODS: Out of twenty-six initially clinically stable PAH patients who had baseline PET/MRI scans, twenty (49.9 ± 14.9 years) had second PET/MRI after 24 months. SUV(RV)/SUV(LV) ratio was used to estimate and compare cardiac glucose uptake. Occurrences of clinical endpoints (CEP), defined as death or clinical deterioration, were assessed during 48-month follow-up from baseline. RESULTS: In first 24 months of observation, sixteen patients had CEP and needed PAH therapy escalation. At follow-up visits, we observed significant improvement of RV ejection fraction (45.1 ± 9.6% to 52.4 ± 12.9%, p = 0.01), mean pulmonary artery pressure (50.5 ± 18.3 to 42.8 ± 18.6 mmHg, p = 0.03), and SUV(RV)/SUV(LV), which tended to decrease (mean change -0.20 ± 0.74). Patients with baseline SUV(RV)/SUV(LV) value higher than 0.54 had worse prognosis in 48 months observation (log-rank test, p = 0.0007); follow up SUV(RV)/SUV(LV) > 1 predicted CEP in the following 24 months, regardless of previously escalated treatment. CONCLUSIONS: PAH therapy escalation may influence RV glucose metabolism, what seems to be related with patients’ prognosis. PET/MRI assessment may predict clinical deterioration regardless of previous clinical course, however its clinical significance in PAH requires further studies. Importantly, even mild alterations of RV glucose metabolism predict clinical deterioration in long follow-up. Clinical Trial Registration ClinicalTrials.gov, NCT03688698, 05/01/2016, https://clinicaltrials.gov/ct2/show/study/NCT03688698?term=NCT03688698&draw=2&rank=1