Assessment of right ventricular- arterial coupling in pre-capillary pulmonary hypertension by 3D echocardiography: a comparison with tricuspid annular plane systolic excursion /systolic pulmonary artery pressure ratio

Background and aim: Noninvasive and simple surrogates of right ventricular-arterial coupling (RVAC) have been explored, such as the ratio of tricuspid annular plane systolic excursion / systolic pulmonary artery pressure (TAPSE/sPAP) and systolic volume / end-systolic volume (SV/ESV) deduced from the simplified formula of conductance catheterization. Thus we aimed to investigate the value of three-dimensional echocardiography (3DE) derived SV/ESV in evaluating RVAC of pre-capillary pulmonary hypertension (PH) and compare it with TAPSE/sPAP. We also explored the relationship between SV/ESV with right heart function, hemodynamic index, clinical indicators and prognostic risk stratification. Methods: The study included 59 pre-capillary PH patients who completed right heart catheterization (RHC), cardiac magnetic resonance imaging (CMR) and echocardiography within 7 days. The "gold standard" of RVAC indexes were derived by RHC and CMR data, including Ees/Ea for right ventricular pulmonary artery coupling, Ees for right ventricular end-systolic maximum elasticity and Ea for pulmonary artery effective elasticity. The corresponding 3DE coupling parameters were SV/ESV, 3D Ees and 3D Ea, respectively. Spearman test and Bland-Altman test were used to analyze the correlation and consistency between 3DE coupling parameters with RHC-CMR coupling standard and TAPSE/sPAP; With right ventricular ejection fraction (RV EF)＜35% measured by CMR as the standard diagnostic criterion of uncoupling, the ROC curve was adopted to determine the diagnostic threshold of SV/ESV and TAPSE/sPAP uncoupling. According to SV/ESV diagnostic threshold, patients were divided into coupling and uncoupling group. Independent sample t test and Chi-square test were used to compare the two groups in terms of right heart function, hemodynamic index, clinical indicators and prognostic risk stratification. Results: 3DE coupling parameters (SV/ESV, 3D Ees, 3D Ea) were strongly correlated with RHC-CMR coupling standard (Ees/Ea, Ees and Ea) , respectively (r = 0.880, 0.755, 0.759, P < 0.05). SV/ESV and TAPSE/sPAP were moderately related (r = 0.611, P < 0.05). 3DE coupling parameters and RHC-CMR coupling standard were in good agreement with a low bias, respectively (SV/ESV vs Ees/Ea:-0.053, 3D Ees vs Ees: 0.176 mmHg/mL/m 2 , 3D Ea vs Ea: 0.393 mmHg/mL/m 2 ) and a satisfactory limits of agreement. The consistency of SV/ESV with TAPSE/sPAP was acceptable (bias: 0.379, 95% CI: -0.006, 0.765). The ROC curve analysis showed the area under the curve (AUC) of TAPSE/sPAP was 0.714 (95% CI, 0.570–0.832）with a optimal cut-off value 0.199 (sensitivity: 70%, specificity: 61.29%). The AUC of SV/ESV was 0.872 (95% CI, 0.759–0.945）with diagnostic threshold 0.533 (sensitivity: 85%, specificity: 74.36%). Right heart echocardiographic parameters (TAPSE, GLS, S’, FAC, RA area, RV/LV, RVOT act), hemodynamic index (mPAP, PVR), clinical indexes (6-minute walking distance, NT-proBNP, WHO FC) and prognostic risk stratification were statistically significant between coupling and uncoupling group ( P < 0.05). Conclusion: 3DE derived SV/ESV can reliably evaluate RVAC as a new noninvasive surrogate. SV/ESV less than 0.533 predicted decreased right cardiac function, worsening hemodynamic and clinical status, and higher prognostic risk stratification.