Exercise-Induced Plasma Surfactant Protein B Response in Advanced Heart Failure: Relation to Exercise Limitation, Resting Invasive Hemodynamics, and Clinical Outcomes.

Plasma surfactant protein B (SPB) is a marker of alveolar-capillary barrier injury and is elevated in heart failure (HF). We assessed whether cardiopulmonary exercise testing (CPET) changes plasma SPB in advanced HF and whether the SPB response relates to exercise limitations, resting pulmonary hemodynamics, and outcomes. Fifty-one patients (mean age 55.6 ± 7.5 years) with advanced HF (NYHA II-III, left ventricular ejection fraction ≤ 35%) underwent comprehensive evaluation, including CPET and invasive hemodynamic assessment. Blood samples were collected before and after CPET. Patients were followed for 23.5 ± 12.6 months. The composite endpoint included death, urgent heart transplantation, or left ventricular assist device implantation. SPB concentrations increased after CPET (median [IQR]: 77.5 [60.5-106.5] vs. 87.2 [63.5-111.9] ng/mL; p < 0.001). Greater relative increases occurred in NYHA III patients and correlated with NT-proBNP. Relative SPB changes correlated positively with the VE/VCO2 slope and negatively with the anaerobic threshold but not with resting systolic pulmonary artery pressure or pulmonary vascular resistance. Neither baseline nor post-exercise levels, nor their changes, predicted clinical outcomes. In conclusion, the SPB response to exercise reflects dynamic pulmonary barrier stress related to functional limitations in advanced HF but lacks prognostic value in this cohort.