Association of the Right Ventricle Cardiac Power Index with Glucose Metabolism and Prognosis in Pulmonary Arterial Hypertension Patients—PET/MRI Study

Background: In pulmonary arterial hypertension (PAH), there is still a need for new prognostic markers to precisely identify patients before clinical deterioration. We investigated the right ventricle cardiac power index (RV CPI) as a tool to assess RV function. We also hypothesized that hemodynamic changes occurring in PAH assessed with the RV CPI are related with cardiac metabolism alterations in PET imaging, which affects prognosis. Methods: Twenty-eight stable PAH patients (51.4 ± 15.9 years old) had PET/CMR and heart catheterization performed at baseline and after 24 months. The PET-derived SUV RV/LV ratio was used to estimate cardiac glucose uptake. Clinical endpoints (CEPs—death or clinical deterioration) were assessed between visits. The RV CPI was defined as cardiac index × mean pulmonary artery pressure × 2.22 × 10−3. Results: The baseline RV CPI was 0.28 ± 0.09 W/m2 and correlated significantly with the SUV RV/LV ratio (r = 0.55, p = 0.002), confirming a relationship between RV hemodynamics and glucose metabolism. After 24 months of PAH-specific therapy, we observed significant improvement in the follow-up RV CPI—0.23 ± 0.04 W/m2 (p = 0.04). During 2-year observations, 16 patients (57%) experienced CEPs (including four deaths). Patients with CEPs had a higher baseline CPI than stable patients (0.32 ± 0.09 vs. 0.21 ± 0.05, p = 0.0006). The cut-off value of the RV CPI to predict worse prognosis was 0.24 W/m2 (log-rank test, p = 0.003). Conclusions: To sum up, the indexed cardiac power output parameter may reflect RV efficiency and is related to its glucose metabolism alterations in PAH. Its low value may help to identify stable patients at higher risk of death or clinical deterioration in long-term prognosis.