The TAPSE/sPAP ratio as an objective echocardiographic correlate of functional impairment in pulmonary arterial hypertension: a retrospective cross-sectional study

Right ventricular–pulmonary arterial (RV–PA) coupling is a key determinant of disease severity and prognosis in pulmonary arterial hypertension (PAH). The tricuspid annular plane systolic excursion to systolic pulmonary arterial pressure (TAPSE/sPAP) ratio is an established non-invasive surrogate of RV–PA coupling; however, its relationship with clinically assessed functional impairment remains incompletely characterized. We investigated the association between TAPSE/sPAP and World Health Organization functional class (WHO-FC) in patients with PAH. This retrospective study included 150 consecutive patients with established PAH receiving PAH-specific therapy who underwent routine clinical evaluation, transthoracic echocardiography, laboratory testing, and six-minute walk testing during the same scheduled outpatient follow-up visit. Patients were categorized as WHO-FC I–II or WHO-FC III–IV. Associations between TAPSE/sPAP and clinical, haemodynamic, echocardiographic, and laboratory parameters were evaluated using correlation and multivariable logistic regression analyses. The previously reported TAPSE/sPAP threshold (≤ 0.31 mm/mmHg) was assessed for identifying advanced functional impairment. Patients with WHO-FC III–IV demonstrated significantly lower TAPSE/sPAP ratios, reduced exercise capacity, and higher pulmonary vascular resistance and lower cardiac output at the diagnostic right heart catheterisation than those with WHO-FC I–II (all p < 0.001). TAPSE/sPAP declined progressively across increasing WHO-FC ( p for trend < 0.001) and showed significant correlations with pulmonary vascular resistance (PVR) and cardiac output recorded at the diagnostic catheterisation, with TAPSE, and with six-minute walk distance. In multivariable analysis, TAPSE/sPAP and six-minute walk distance remained independently associated with WHO-FC III–IV, whereas RDW-SD and the CRP/albumin ratio did not. Analysed as a continuous variable, TAPSE/sPAP identified WHO-FC III–IV with an area under the receiver operating characteristic curve of 0.874; when the prespecified threshold of ≤ 0.31 mm/mmHg was applied as a binary classifier, specificity was 96.7% and sensitivity 64.4%. The TAPSE/sPAP ratio showed consistent associations with clinically assessed functional impairment and exercise capacity, and was also correlated with selected haemodynamic parameters obtained at diagnostic assessment.These findings support TAPSE/sPAP as an objective echocardiographic correlate of functional impairment that may complement, rather than replace, conventional symptom-based functional assessment.