Comparison of Tricuspid Annular Plane Systolic Excursion to Pulmonary Artery Systolic Pressure Ratio Measured by Transthoracic Echocardiography and Right Heart Catheterization in Pulmonary Arterial Hypertension: Prognostic Implications

<b>Background/Objectives</b>: Ventricular-arterial (VA) coupling, assessed via the TAPSE/PASP ratio, is a well-established prognostic marker in pulmonary arterial hypertension (PAH). However, transthoracic echocardiography (TTE) often fails to estimate the pulmonary artery systolic pressure (PASP). This study evaluated the prognostic value of TAPSE/PASP when PSAP was obtained both via TEE and RHC and their correlation. <b>Methods</b>: A prospective registry included 90 PAH patients (April 2021-May 2024). TTE and RHC were performed according to clinical guidelines. The correlation and agreement between both techniques were assessed using Spearman's rank correlation and a Bland-Altman analysis. The prognostic utility of TAPSE/PASP for clinical worsening (CW) (death or lung transplantation) was evaluated using Cox models, Harrell's c-statistics, and ROC curve analysis. <b>Results</b>: The median interval between TTE and RHC was 1.5 days (range -3 to +43). TAPSE/PASP showed a strong correlation between both techniques (rho = 0.74, <i>p</i> < 0.001), though TTE slightly overestimated values due to PASP underestimation. The PASP correlation was moderate (rho = 0.56, <i>p</i> < 0.001). CW occurred in 17.8% of patients. According to cut-off points established based on ESC/ERS guidelines, VA coupling via TTE effectively stratified the risk of CW (HR 7.0, <i>p</i> = 0.076 and HR 34.8, <i>p</i> = 0.002 for intermediate and high risk, respectively), whereas VA coupling with PASP measured via RHC showed no association with CW. TAPSE/PASP based on TTE demonstrated superior prognostic performance (C-index = 0.81) over RHC-derived parameters (C-index = 0.58). <b>Conclusions</b>: The TAPSE/PASP ratio showed a strong correlation between TTE and RHC. However, while RHC remains the gold standard for hemodynamic assessments, echocardiographic measurements demonstrated superior performance in risk stratification, supporting its role as a valuable non-invasive tool in PAH.