RACE Trial: Effect of Balloon Pulmonary Angioplasty and Riociguat on Right Ventricular Afterload and Function in Chronic Thromboembolic Pulmonary Hypertension

Even though pulmonary endarterectomy is the treatment of choice for chronic thromboembolic pulmonary hypertension (CTEPH), up to 40% of patients are not candidates because of distal lesions or comorbidities. For these cases, there is specific medical treatment and balloon pulmonary angioplasty (BPA).

This post hoc analysis of the RACE trial compared the effects of Riociguat and BPA on right ventricular (RV) afterload and function in 100 patients with inoperable CTEPH: 49 were treated with Riociguat and 51 with BPA. Also, 18 patients received Riociguat after BPA, and 36 BPA after Riociguat; patients were followed up to 26 weeks and reassessed hemodynamically at week 52.

Mean patient age was 63 ± 11, and 63 % were women. Left ventricular ejection fraction (LVEF) was normal in all patients, while RV function was reduced, with RV fractional area change (FAC) 27 ± 8 %. Mean pulmonary arterial pressure (mPAP) was 40 ± 9 mmHg, pulmonary vascular resistance (PVR) 6.9 ± 2.6 WU, cardiac output 3.9 ± 1.1 L/min and right atrial pressure (RA) 7 ± 3 mmHg. In the BPA group, procedures were done to mean three vessels per patient, with an average of three interventions to complete treatment. 

Primary end point was relative change in RV afterload at 26 weeks, measured by PVR. Secondary end points included cardiac output, systolic volume, mPAP and RV function parameters such as stroke volume and right atrial pressure.

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Both strategies, Riociguat and BPA, achieved significant improvement in RV afterload. However, BPA showed greater relative reduction of PVR (−41 % vs. −22 %; p<0.001), mainly DUE to decreased mPAP (−9.5 mmHg). Also, BPA alone produced significant RV function improvement: reduced RAP pressure (−2 mmHg; p=0.02), increased stroke volume (+0.12 J; p=0.002) and increased RVFAC (+6 %; p=0.04). Riociguat also contributed to RV afterload reduction, mainly by increasing cardiac output (+0.7 L/min), though with no significant changes in RV function parameters. 

At week 12, patients receiving BPA after an initial treatment with Riociguat presented additional and sustained RV afterload reduction (−30 %) and improved RVFAC (+6 %). Those who started with BPA maintained hemodynamic and functional improvement reached at week 26, with no evidence of subsequent deterioration. 

Conclusion

Even though both Riociguat and BPA were effective to reduce RV afterload in patients with inoperable CTEPH, BPA showed a superior impact on said reduction and was the only strategy associated to significantly improved RV function parameters. 

Original Title: Effect of Balloon Pulmonary Angioplasty and Riociguat on Right Ventricular Afterload and Function in CTEPH: Insights From the RACE Trial.

Reference: Christian Gerges, et al. Circulation: Cardiovascular Interventions, Volumen 18, e014785, 2025.