Assessment of RV-PA Coupling in Advanced Heart Failure Using TAPSE×PAAT and Its Association With Functional Capacity

Right ventricular-pulmonary arterial (RV-PA) coupling plays a central role in determining functional capacity in advanced heart failure (HF). Although the TAPSE/PASP ratio is widely used as a noninvasive surrogate of RV-PA coupling, its applicability may be limited by the availability and quality of tricuspid regurgitation Doppler signals. Pulmonary artery acceleration time (PAAT) is a TR-independent marker of pulmonary vascular load, and the composite index TAPSE×PAAT has emerged as a potential alternative.

This retrospective single-center study included 194 patients with advanced HF who underwent comprehensive transthoracic echocardiography, cardiopulmonary exercise testing, and right heart catheterization. Patients were stratified according to TAPSE×PAAT tertiles. Associations between RV-PA coupling indices (TAPSE/PASP and TAPSE×PAAT) and functional capacity, assessed by peak oxygen uptake (peak VO₂), were evaluated using multivariable regression models after variable selection with LASSO. Model performance was compared using adjusted R², AIC, and RMSE.

Higher TAPSE×PAAT values were associated with progressively better exercise performance. Peak VO₂ increased stepwise across TAPSE×PAAT tertiles (11.3 ± 3.7 vs. 13.4 ± 3.7 vs. 15.3 ± 3.9 mL/kg/min, p < 0.001). In multivariable analyses, both TAPSE/PASP and TAPSE×PAAT remained independently associated with peak VO₂. The TAPSE/PASP model demonstrated slightly better global fit statistics (adjusted R² = 0.511 vs. 0.500; AIC = 980.8 vs. 985.0; RMSE = 2.66 vs. 2.69), whereas TAPSE×PAAT showed consistent statistical significance across models. Agreement between predicted peak VO₂ values derived from both indices was high.

In advanced HF, TAPSE×PAAT, and TAPSE/PASP showed comparable relationships with functional capacity, supporting TAPSE×PAAT as a complementary echocardiographic surrogate of RV-PA coupling, particularly in clinical settings where PASP estimation is limited.