Multimodality Assessment of Right Ventricular–Pulmonary Arterial Coupling and Pulmonary Artery Compliance in Youth with Pulmonary Arterial Hypertension: A Pilot Study

Figure 1. Standardized univariable associations between multimodality physiologic indices and clinical severity measures. Scatterplots demonstrate associations of echocardiographic RV–PA coupling (TAPSE/sPAP), CMR-derived RVEF, CMR-derived RV–PA coupling (RVSV/RVESV), indexed pulmonary artery compliance, and catheter-derived PVRi with WHO functional class, 6MWD, and NTproBNP. All variables were standardized using Z-score transformation. Solid lines represent fitted univariable linear regression lines; horizontal and vertical dashed lines indicate Z = 0. Standardized regression coefficients (β), coefficients of determination (R²), and p values are displayed within each panel. These cross-sectional associations are exploratory and do not constitute validation against pressure–volume loop-derived Ees/Ea. 6MWD, 6-minute walk distance; CMR RVEF, Cardiac MRI derived RV ejection fraction; CMR RV-PA, CMR-derive RV-PA coupling; ECHO RV-PA, Echo-derived RV-PA coupling; NT-pro BNP, N-terminal pro–B-type natriuretic peptide; PVRI, Pulmonary vascular resistance index; WHO, World health organization.

Figure 2. Exploratory discriminative performance of echocardiographic, CMR-derived, and hemodynamic indices for clinical severity measures. Receiver-operating-characteristic curves compare echocardiographic RV–PA coupling (TAPSE/sPAP), CMR-derived RVEF, CMR-derived RV–PA coupling (RVSV/RVESV) and indexed pulmonary artery compliance for identifying (A) WHO functional class III–IV, (B) elevated NT-proBNP, and (C) reduced 6MWD, according to the prespecified study definitions. Discrimination is summarized using the area under the receiver-operating-characteristic curve (AUC). For variables in which lower values represent worse physiology, including RVEF, RV– PA coupling, and pulmonary artery compliance, the direction was aligned so that a higher AUC consistently represents better discrimination. Given the small sample size, the AUC estimates are exploratory and should not be interpreted as validated thresholds or evidence of comparative prognostic superiority. CMR RVEF, Cardiac MRI derived RV ejection fraction; CMR RVPA, CMR-derive RV-PA coupling; ECHO RVPA, Echo-derived RV-PA coupling; WHO, World health organization.

Figure 3. Central Figure: Multimodality assessment of right ventricular function and pulmonary vascular load in youth with pulmonary arterial hypertension. The central illustration summarizes the prospective cohort, contemporaneous multimodality evaluation, physiologic domains assessed, and principal interpretation. Echocardiographic TAPSE/sPAP and CMR-derived RVSV/RVESV were evaluated as surrogate indices of RV–PA coupling; reference-standard pressure–volume loop-derived Ees/Ea was not measured. Indexed pulmonary artery compliance represents the pulsatile component of RV afterload, whereas PVRi represents resistive pulmonary vascular load. CMR-derived volumetric indices and indexed pulmonary artery compliance may complement but should not replace echocardiography and invasive hemodynamic assessment. Because of the small, etiologically heterogeneous cohort, all observed clinical associations are hypothesis-generating and require validation against pressure–volume loop-derived Ees/Ea and longitudinal clinical outcomes. 6MWD, 6-minute walk distance; AUC, area under the receiver-operating-characteristic curve; CMR, cardiac magnetic resonance; Ea, arterial elastance; Ees, end-systolic…