Jellis, C.L.

Abstract Introduction Interstitial lung disease-associated pulmonary hypertension (ILD-PH) is a clinically challenging entity that lies on a pathophysiologic spectrum between pulmonary arterial hypertension (PAH) and interstitial lung disease (ILD). We compared the metabolomes of patients with ILD-PH to those with PAH and ILD to characterize the PAH-ILD axis and determine whether ILD-PH patients can be phenotyped based on their metabolomic similarity to PAH. Methods Using untargeted metabolomics profiles from patients with PAH, ILD, and ILD-PH in the large, U.S.-based, NIH-funded, multi-center PVDOMICS cohort, we trained an anchor-based classifier on PAH and ILD metabolomes using supervised PLS-DA with a 75/25 train/test split. Primary and secondary PH or risk-group classifications in PVDOMICS were based on expert adjudication of clinical data including right heart catheterization hemodynamics, pulmonary function testing, chest imaging, and laboratory results. We then applied the trained model to each ILD-PH patient to assign a PAH similarity score. We classified patients as having a PAH-like or ILD-like metabolomic phenotype using an optimal PAH similarity score cutoff of 0.5 then compared PAH metabolomic similarity to expert-adjudicated primary and secondary WSPH classifications in PVDOMICS. We implemented FELLA, a network-based metabolomics enrichment method, to holistically characterize the biologic underpinnings of PAH, ILD-PH, and ILD metabolomes. Results We analyzed 244 patients with PAH, 54 with ILD, and 47 with ILD-PH. The anchor-based classifier demonstrated high train-test performance with a c-statistic of 0.81 and 78% agreement with expert-adjudicated diagnoses. Among the ILD-PH patients, 23 were classified as PAH-like and 24 as ILD-like (74% agreement with expert adjudication, Cohen’s kappa 0.49, Hedge’s g estimate of 0.86). FELLA enrichment revealed core glycolytic and bioenergetic pathways were enriched in both pure PAH and ILD-PH. Comparison of diffusion Z-scores between groups demonstrated subtle but biologically coherent differences in several reaction-level nodes, including lactate, NADPH oxidoreductase, and phosphofructokinase, which were enriched in ILD-PH. Conclusion Patients with ILD-PH demonstrate clinically relevant metabolomic phenotypes. Examination of the network biology underlying ILD-PH may point to potential therapeutic targets in this vulnerable subgroup with lagging clinical outcomes. This abstract is funded by: Pulmonary Fibrosis Foundation PFF Scholars Program

Abstract Rationale: Although guidelines recommend the use of provocative testing to diagnose pulmonary venous hypertension (PVH) that is unapparent at normal resting right heart catheterization (RHC), the incremental value of provocative testing is unknown. We aim to evaluate the incremental diagnostic capability of inhaled nitric oxide (iNO), fluid challenge (FC) or invasive cardiopulmonary exercise testing (iCPET) to unmask PVH using previously defined hemodynamic cutoffs. Methods: We included subjects from the NHLBI-funded Pulmonary Vascular Disease Phenomics (PVDOMICS) study. Our analysis included patients with World Symposium on Pulmonary Hypertension (WSPH) Group 2 disease (G2PH) and G2PH comparators (WSPH Group 2 phenotype without a diagnosis of PH) as determined by the PI or adjudication panel. We then applied a protocol-driven provocative approach based on the feasibility of modalities available in most catheterization labs. Using a pulmonary capillary wedge pressure (PCWP) cutoff of >15, frequencies were identified for subjects based on resting PCWP and with iNO. Frequencies were also identified for: those who received FC with a PCWP cutoff of ≥18 or those who received iCPET with PCWP cutoff of >20 (upright) or >25 (supine). Results: There were 419 subjects identified with WSPH Group 2 disease (Figure). Roughly half were found to have a PCWP >15 during resting RHC (N = 207). Of the remaining subjects with a resting PCWP ≤15 (N = 150), 42 subjects were found to have a PCWP >15 with iNO administration (40.0%). Of the remaining 63 subjects with PCWP ≤15 following iNO administration, nearly half (N = 26, 48.0%) demonstrated a PCWP ≥18 following FC while 8 subjects (14.8%) demonstrated an elevated PCWP following iCPET. Conclusions: There is a high proportion of G2PH patients (∼35%) who appear hemodynamically similar to precapillary PH at rest. Inhaled nitric oxide vasodilatory challenge unmasks G2PH in many patients. In situations where iNO does not disclose the G2PH phenotype, provocation with FC or iCPET can be useful as a supplementary provocative maneuver. Future directions will focus on agnostically assessing the utility of provocation based on grouping subjects by resting hemodynamics as well as assessing the use of provocation in other forms of PH.