Pulmonary Surfactant Protein B in the Peripheral Circulation and Functional Impairment in Patients With Chronic Heart Failure

INTRODUCTION AND OBJECTIVES Surfactant protein B (SP-B) is a marker of damage to the alveolar-capillary barrier that could be useful for monitoring functional impairment in patients with chronic heart failure (HF). METHODS Dyspnea-limited cardiopulmonary exercise testing was carried out in 43 outpatients with chronic HF (age 51+/-10 years, 77% male, left ventricular ejection fraction [LVEF] 33+/-11%). Peripheral blood serum samples were obtained at rest and during the first minute of peak exercise. The presence and concentration of SP-B in the serum samples were determined by Western blot analysis. RESULTS At rest, SP-B was detected in 35 (82%) patients compared with only six (23%) healthy volunteers in a control group (n=26, age 51+/-10 years, 77% male). The median circulating SP-B level was higher in HF patients, at 174 [interquartile range, 70-283] vs. 77 [41-152] (P< .001) in the control group. In HF patients, the presence of circulating SP-B was associated with a lower LVEF (31.4+/-9.6% vs. 41.8+/-15%; P=.01). Multivariate analysis showed that the resting SP-B level correlated with a greater VE/VCO2 slope (beta=1.45; P=.02). The peak-exercise SP-B level correlated almost perfectly with the resting level (r=0.980; P< .001), but there was no significant increase with exercise (P=.164). Nor was there a correlation with any other exercise parameter. CONCLUSIONS In patients with chronic HF, the level of pulmonary surfactant protein B in the peripheral circulation is increased and is correlated with ventilatory inefficiency during exercise, as indicated by the VE/VCO2 slope.