TAPSE/PAi, a practical echocardiographic functional–structural index, better reflects functional severity than TAPSE/sPAP in pulmonary hypertension

BACKGROUND: We evaluated TAPSE/PAi, defined as the ratio of tricuspid annular plane systolic excursion to the indexed main pulmonary artery diameter, as a pragmatic functional-structural index and compared it with TAPSE/sPAP. METHODS: In this retrospective study, 53 patients with PAH were analyzed. Associations of TAPSE/PAi and TAPSE/sPAP with clinical, biomarker, and invasive hemodynamic variables were assessed. Discrimination for WHO-FC ≥ 3, 6MWD < 165 m, and PVR > 5 WU was evaluated by direction-aligned ROC analysis with Youden-optimal thresholds. Age- and sex-adjusted logistic regression models reported odds ratios (ORs) per 1-SD increase. RESULTS: TAPSE/PAi correlated more strongly than TAPSE/sPAP with WHO-FC (ρ=-0.592 vs. -0.384) and 6MWD (ρ = 0.493 vs. 0.378), whereas TAPSE/sPAP correlated more strongly with NT-proBNP/proBNP (ρ=-0.619 vs. -0.484) and with mPAP/PVR. TAPSE/PAi showed better discrimination for WHO-FC ≥ 3 and 6MWD < 165 m while TAPSE/sPAP performed modestly better for PVR > 5 WU The Youden-optimal TAPSE/PAi threshold was ≤ 1.296 for both WHO-FC ≥ 3 and 6MWD < 165 m. The higher TAPSE/PAi remained associated with lower odds of WHO-FC ≥ 3 and 6MWD < 165 m after age- and sex-adjustment. CONCLUSIONS: TAPSE/PAi better reflects functional severity and exercise limitation, whereas TAPSE/sPAP is more closely related to biomarker/hemodynamic burden. The indices appear complementary, and TAPSE/PAi may be a practical TR-independent severity marker in PAH.