Plasma Surfactant Protein-B

Abstract

Background— In chronic heart failure (CHF), elevated pulmonary microvascular pressure (P mv ) results in pulmonary edema. Because elevated P mv may alter the integrity of the alveolocapillary barrier, allowing leakage of surfactant protein-B (SP-B) from the alveoli into the circulation, we aimed to determine plasma levels of SP-B in CHF and their relation to clinical status. Methods and Results— Fifty-three outpatients with CHF had plasma SP-B and N-terminal proBNP (NT-proBNP) assayed, in addition to a formalized clinical assessment at each clinic review over a period of 18 months. The control group comprised 19 normal volunteers. Plasma SP-B was elevated in CHF ( P <0.001), and levels increased with New York Heart Association classification ( P <0.001). SP-B correlated with objective clinical status parameters and NT-proBNP. During follow-up, major cardiovascular events occurred in patients with higher plasma SP-B ( P <0.01) and NT-proBNP ( P <0.05). Furthermore, on conditional logistic regression analysis, only SP-B was independently associated with CHF hospitalization ( P =0.005). The 53 patients underwent a total of 210 outpatient visits. When the diuretic dosage was increased on clinical grounds, SP-B had increased 39% ( P <0.001) and NT-proBNP had increased 32% ( P <0.001). Conversely, at the next visit, SP-B fell 12% ( P <0.001), whereas NT-proBNP fell 39% ( P <0.001). Conclusions— Plasma SP-B is increased in CHF, and levels are related to clinical severity. Furthermore, within individual patients, SP-B levels vary with dynamic clinical status and NT-proBNP levels. Because plasma SP-B is independently associated with CHF hospitalization, it may, by virtue of its differing release mechanism to NT-proBNP, be a clinically useful biomarker of the pulmonary consequences of raised P mv .