Prognostic value of alveolar surfactant type-B in acute heart failure: a long-term comparative analysis vs NT-proBNP

Abstract Background In heart failure (HF) biomarkers are an integral component of prognostic assessment. Natriuretic peptides are the gold standard, but they do not directly reflect lung vascular injury. Surfactant type B (Surf-B) is released by type 2 alveolar cells under pressure induced trauma, with few reports just addressing its plasmatic levels in stable chronic HF (CHF). Information on acute HF (AHF) is lacking. Purpose To clarify the prognostic value of Surf-B changes vs NT-proBNP levels after decongestion therapy and to compare their prognostic ability at 1-year follow-up. Methods Patients with acute pulmonary edema (APE) underwent a combined evaluation of Surf-B and NT-proBNP serum levels with quantification of B-lines at hospital admission (time 0), discharge (time 1) and at 1 year (time 2). Results 54 patients (mean age 72.1 ± 11 years; mean LVEF 36% ± 13%; 65% men) were enrolled. At time 1, the average Surf-B, NT-proBNP and B-lines were significantly reduced compared to time 0 (p<0.0001). No correlation between Surf-B and NT-proBNP was observed either at time 0 (r=-0.21; p=0.12) or at time 1 (r=0.05; p=0.71). Despite the significant decrease in Surf-B levels from time 0 to time 1, 18.5% of patients behaved as non-responders exhibiting no changes in Surf-B; conversely, only 5.5% did not show significant reduction in NT-proBNP, despite significant decongestion. 38 patients were followed up to time 2: of these, 13 (34%) reached the composite endpoint of death or hospitalization for HF. Surf-B measured at time 1 was a strong predictor of adverse outcome. Patients with Surf-B above median at discharge displayed a worse survival-free from HF hospitalization compared to the remainders (Log rank p=0.012) (Figure). Also, patients with Surf-B above median at discharge had a more than 4-fold increased risk of the composite endpoint (HR 4.5, 95%CI 1.4-20.2, p=0.023). Conversely, NT-proBNP at discharge was not significantly associated with HF-free survival (Log rank p=0.26) (Figure) and was not a significant predictor of the composite outcome (HR 1.9, 95%CI 0.6-9.3, p=0.25). At ROC analysis, discharge Surf-B levels showed a higher area under the curve (AUC=0.763, p=0.011) than NT-proBNP values (AUC=0.69, p=0.063). Conclusions These data suggest that Surf-B, an organ specific biomarker of lung injury, is highly sensitive to the effectiveness of decongestion therapy, outperforming NT-proBNP. Given the high rate of patients who do not improve their Surf-B levels over time, the reparative processes of alveolar break damage may dissociate from mere decongestion and cardiac healing in AHF.Figure:1yr Kaplan-Meier survival curves