Low DLCO Can Provide Insights into Treatment Response in PAH Patients Irrespective of the Reason for Its Decrease.

Area of Science:

• Pulmonary Medicine
• Cardiology
• Respiratory Physiology

Background:

• Pulmonary arterial hypertension (PAH) involves diverse etiologies and histological changes affecting gas exchange.
• Decreased diffusing capacity for carbon monoxide (DLCO) in PAH can indicate pathobiology and prognosis but doesn't pinpoint the cause.
• Identifying distinct PAH subpopulations based on DLCO may refine understanding and treatment.

Purpose of the Study:

• To investigate if PAH patients with low DLCO represent a unique subpopulation.
• To characterize the clinical features and treatment response of PAH patients with low DLCO.

Main Methods:

• Retrospective study of 69 PAH patients.
• Division into two groups: DLCO ≥ 45% (Group 1) and DLCO < 45% (Group 2).
• Comparison of demographic, clinical, hemodynamic, and treatment data between groups.

Main Results:

• Group 2 (low DLCO) patients were older, more frequently male, and had a history of smoking compared to Group 1.
• Group 2 exhibited higher pulmonary vascular resistance (PVR) but similar mean pulmonary arterial pressure (PAP).
• Patients in Group 2 showed no improvement in WHO-Functional Class, 6-minute walk distance, or NT-proBNP after treatment.

Conclusions:

• PAH patients with low DLCO possess distinct clinical characteristics, including older age, male sex, and smoking history.
• Low DLCO in PAH is associated with poor prognosis and reduced response to vasodilatory therapies.
• DLCO is valuable for phenotyping PAH patients and guiding therapeutic strategies, especially with emerging treatment targets.