Multimodal Characterization of High-risk PH-HFpEF phenogroup with Right Ventricular Dysfunction: Vascular Mechanics and Myocardial Transcriptomics

Background Pulmonary hypertension due to heart failure with preserved ejection fraction (PH-HFpEF) is a highly heterogeneous disease associated with right ventricular (RV) failure and adverse outcomes. Current diagnostic tools inadequately characterize pulmonary vascular disease and RV dysfunction, limiting treatment precision. We hypothesized that deep phenotyping—including invasive hemodynamics, advanced imaging, and myocardial transcriptomics—would identify high-risk PH-HFpEF phenotypes with distinct clinical, physiologic, and molecular characteristics. Methods 42 PH-HFpEF participants (and 25 pre-capillary PH participants, as a comparison group) underwent clinical evaluation, echocardiography, cardiac MRI (cMRI), and invasive cardiopulmonary exercise testing (iCPET). K-means clustering considering clinical, iCPET, and cMRI data stratified participants into distinct clusters (phenogroups). A subset underwent further characterization by invasive pulmonary vascular mechanics (n=17 PH-HFpEF, n=5 pre-capillary PH) and 4D flow cMRI (n=10 PH-HFpEF, n=5 pre-capillary PH). Endomyocardial biopsies from 10 PH-HFpEF participants were analyzed using long-read RNA-sequencing for differential gene and transcript expression. Results Clustering revealed two PH-HFpEF phenogroups with significantly different outcomes at one-year follow-up (HR=11.96, CI: 2.66–53.86). High-risk participants had greater left ventricular mass, reduced RV ejection fraction, worse exercise-induced PH, impaired gas exchange (↓peak oxygen consumption, ↑slope of minute ventilation/carbon dioxide production), and lower myocardial strain. Pulmonary vascular mechanics showed higher proximal pulmonary artery stiffness (↑characteristic impedance), increased RV energy expenditure (↑compression waves), and abnormal distal vascular reflections (↓diastolic reflection index) in the high-risk group. 4D flow MRI revealed disturbed flow in pulmonary vasculature (both arteries and veins) in high-risk participants. Transcriptomic analysis implicated differences in post-transcriptional RNA processing and translational control, as well as mitochondrial function, in phenotypic divergence between these HFpEF subgroups. In particular, differential transcript usage for the TTN gene, encoding the giant sarcomeric protein titin, may be particularly relevant to elevated myocardial stiffness, which worsens vascular remodeling and precipitates RV dysfunction and failure. Conclusions In PH-HFpEF, unsupervised clustering using deep physiologic and imaging data identified a high-risk group with impaired RV function and unique transcriptomic profiles. Our findings suggest that proximal and distal pulmonary vascular remodeling, as well as differences in titin isoform expression, may underlie RV failure in this phenogroup. This comprehensive approach provides a framework for mechanistically driven precision medicine strategies in PH-HFpEF. Clinical perspectives 1. What is new? Unsupervised clustering integrating exercise hemodynamics, cardiac MRI, and clinical features revealed a distinct PH-HFpEF subgroup at significantly higher risk for adverse outcomes (HR = 11.96), independent of traditional IpcPH/CpcPH classification. Invasive wave mechanics (impedance and wave separation analyses) and non-invasive 4D flow cardiopulmonary MRI reveal unique patterns of proximal stiffness, RV energy inefficiency, and abnormal distal reflections in high-risk PH-HFpEF, providing insights into segmental vascular dysfunction. Long-read RNA sequencing of endomyocardial biopsies from PH-HFpEF patients revealed distinct transcriptomic signatures between high- and low-risk PH-HFpEF phenogroups. Long-read RNA-seq identified distinct transcript usage of gene TTN, encoding a giant sarcomeric protein (titin) that is a key determinant for myocardial stiffness, suggesting a potential underlying mechanism for RV dysfunction in PH-HFpEF. 2. What are clinical implications? These findings offer a framework for more refined patient classification beyond traditional PVR-based methods, which may improve identification of high-risk individuals who require closer monitoring or targeted therapy. The integrative approach highlights titin isoform imbalance and vessel-specific stiffness as potential therapeutic targets, supporting the development of biology-informed, phenotype-specific interventions for PH-HFpEF with RV dysfunction.