Right ventricular energetics and hemodynamic forces in pulmonary arterial hypertension: a 4D flow cardiac magnetic resonance study

Background: Pulmonary arterial hypertension (PAH) leads to progressive right ventricular (RV) overload and failure. While cardiac magnetic resonance (CMR) is the gold standard for RV assessment, conventional parameters mainly reflect late disease stages. 4D Flow MRI allows comprehensive evaluation of intracardiac flow, offering new insights into RV energetics and hemodynamics. Objectives: To investigate RV kinetic energy (KE), viscous energy loss (EL), dissipation index (DI), and hemodynamic forces (HDF) in PAH patients, and to explore their correlations with invasive hemodynamic data, clinical risk stratification (REVEAL Lite 2), and outcomes. Methods: Twenty-five PAH patients and ten controls underwent 4D Flow MRI and clinical assessment. Sixteen PAH patients had analyzable 4D Flow datasets. RV global and regional KE, EL, DI, and HDF were quantified and compared between groups, and correlations with right heart catheterization parameters were assessed. Results: PAH patients showed significantly reduced global and regional systolic KE (p = 0.007–0.029) and loss of the normal biphasic diastolic pattern. The systolic apical–basal HDF amplitude was significantly decreased (p = 0.01), reflecting impaired flow directionality. Moreover, several indices of viscous energy dissipation (EL and DI), both during systole and diastole, showed a moderate positive correlation with mean pulmonary arterial pressure (mPAP). KE parameters decreased progressively across REVEAL Lite 2 risk categories (p < 0.05). Conclusions: 4D Flow MRI identifies RV flow derangements in PAH, providing quantitative markers of contractile inefficiency and altered hemodynamics. Systolic KE correlates with invasive and prognostic parameters, suggesting potential for non-invasive risk assessment and therapy monitoring.