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

Background:Cardiac magnetic resonance (CMR) enables comprehensive assessment of right ventricular (RV) function and ventricular-vascular interaction in pulmonary arterial hypertension (PAH). This exploratory pilot study compared echocardiographic and CMR-derived surrogate indices of RV-pulmonary arterial (RV-PA) coupling and examined indexed pulmonary artery compliance (PAc) in adolescents and young adults with PAH. Methods:Twenty adolescents and young adults with Group 1 PAH underwent transthoracic echocardiography, CMR, and cardiac catheterization within 7 days. Echocardiographic TAPSE/systolic pulmonary artery pressure (sPAP) and CMR RV stroke volume/end-systolic volume were analyzed as noninvasive surrogates of RV-PA coupling; pressure-volume loop-derived end-systolic elastance/arterial elastance was not measured. Indexed PAc and pulmonary vascular resistance index (PVRi) were derived from catheterization and CMR data. Associations with WHO functional class, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and 6-minute walk distance (6MWD) were explored. Results:Echocardiographic TAPSE/sPAP showed limited associations with clinical severity measures. CMR-derived RV indices showed stronger exploratory associations with NT-proBNP and 6MWD. In the prespecified multivariable model of the exercise endpoint, indexed PAc had the largest standardized coefficient (β = -0.78; 95% CI, -1.48 to -0.09; p = 0.031); PVRi and the imaging surrogates were not statistically significant. Estimates were imprecise because of the small sample. Conclusions:In this small, hypothesis-generating cohort, CMR-derived RV-PA coupling and indexed PAc provided complementary physiologic information beyond the echocardiographic surrogate. These observations require validation against pressure-volume loop-derived coupling and prospective clinical outcomes.