Significance of diffusing capacity of the lungs for carbon monoxide on chronic thromboembolic pulmonary hypertension

Reduced diffusing capacity of the lungs for carbon monoxide (DLco) reflects microvasculopathy in chronic thromboembolic pulmonary hypertension, yet its clinical value is uncertain. In a Japanese nationwide registry (2018–2023) we studied 1270 patients: 486 formed an event cohort and 299 a treatment cohort who underwent pulmonary endarterectomy or balloon pulmonary angioplasty. Lower baseline DLco was indicative of smaller postprocedural improvements in mean pulmonary artery pressure, pulmonary vascular resistance and cardiac index (all p≤0.023) and a higher risk of clinical events (HR 0.971, p=0.005). Outcomes deteriorated below 59.6%, indicating DLco may help stratify prognosis and treatment benefit.