Right ventricular to pulmonary artery coupling in chronic thromboembolic pulmonary hypertension

Background: Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by increased pulmonary vascular resistance (PVR) and pressure and right ventricular (RV) dysfunction. We aimed to evaluate the correlation of RV to pulmonary artery coupling, measured as the tricuspid annular plane systolic excursion/pulmonary arterial systolic pressure (TAPSE/PASP) ratio, and invasive hemodynamic measurements, and to assess the changes in this ratio following CTEPH treatment. Methods: We conducted a retrospective cohort study of CTEPH patients treated at Aarhus University Hospital with pulmonary angioplasty (BPA), pulmonary endarterectomy (PEA), and or medical therapy only. Patients underwent transthoracic echocardiography and right heart catheterization at baseline and follow-up. The primary endpoint was the association between TAPSE/PASP and PVR. Secondary endpoints included other hemodynamic and functional parameters. Results: The study included 139 patients. Mean TAPSE/PASP at baseline was 0.22 [0.16, 0.29] mm/mmHg. An exponential decay correlation was found between TAPSE/PASP and PVR (correlation coefficient - 0.67, p < 0.001). The TAPSE/PASP ratio improved from 0.23 [0.18; 0.29] to 0.33 [0.26; 0.46] mm/mmHg, p < 0.0001, following BPA, and from 0.20 [0.15;0.27] to 0.35 [0.21;0.41] mm/mmHg, p = 0.0007 following PEA, indicating enhanced RV to pulmonary artery coupling. Conclusion: In patients with CTEPH, the echocardiographic TAPSE/PASP ratio as a measure of RV-PA coupling correlates well with invasively measured pulmonary vascular resistance. The TAPSE/PASP ratio improved after BPA or PEA treatments suggesting a potential use for monitoring patient outcomes. Further prospective studies are warranted to establish the prognostic value of the TAPSE/PASP ratio and ability to guide treatment decisions.