Revisiting RV-PA coupling in advanced heart failure: TAPSExPACT for predicting functional capacity in difficult-to-assess patients
B Kultursay, M Karacam, S Tanyeri, D Mutlu, B Guven, S C Efe, G S Halil, O Y Akbal, C Dogan, M K Kirali, R D AcarAbstract
Background and Purpose
Right ventricular–pulmonary arterial (RV–PA) coupling is a key determinant of functional capacity in advanced heart failure (HF). The conventional noninvasive index TAPSE/PASP cannot be calculated in patients with absent or severe tricuspid regurgitation (TR), limiting its clinical applicability. We evaluated whether TAPSE×PACT—a PASP-independent surrogate—provides comparable predictive value for peak VO₂ and offers advantages in technically challenging scenarios.
Methods
A total of 194 patients with advanced HF (LVEF ≤25%) who underwent standardized echocardiography, cardiopulmonary exercise testing (CPET), and right-heart catheterization within a 1-week interval were retrospectively evaluated. Patients with severe pulmonary disease, contraindications to CPET/RHC, or non-measurable tricuspid Doppler signals were excluded. TAPSE×PACT was divided into tertiles for phenotypic characterization. Variable screening was performed using LASSO regression, followed by two predefined multivariable linear models: (1) baseline predictors + TAPSE/PASP and (2) baseline predictors + TAPSE×PACT. Peak VO₂ was the primary outcome. Model performance was assessed using adjusted R², RMSE, and AIC.
Results
Higher TAPSE×PACT tertiles exhibited progressively smaller RV dimensions, lower pulmonary pressures, more favorable RV deformation indices, and higher peak VO₂ (11.3 vs. 13.4 vs. 15.3 mL/kg/min; p<0.001). Both coupling indices independently predicted peak VO₂. The TAPSE/PASP model demonstrated slightly superior global performance (AIC 980.8 vs. 985.0; RMSE 2.66 vs. 2.69; adjusted R² 0.510 vs. 0.500). TR severity was not significant in the TAPSE/PASP model but emerged as an independent predictor in the TAPSE×PACT model.
Conclusion
Although TAPSE/PASP showed marginally better overall statistical performance, TAPSE×PACT achieved nearly equivalent predictive accuracy and offered clear practical advantages, particularly when PASP estimation is unreliable due to inadequate TR Doppler signals. TAPSE×PACT may therefore serve as a robust PASP-independent alternative for assessing RV–PA coupling and functional capacity in advanced HF.For image description, please refer to the figure legend and surrounding text.ScatterplotFor image description, please refer to the figure legend and surrounding text.