Objective To investigate the change of N-terminal pro-B-type natriuretic peptide ( NT-proBNP) levels in plasma of patients with stable chronic obstructive pulmonary disease ( COPD) at exertion. Methods Pulmonary function testing, increamental and constant cycle ergometer exercise testing were performed in 19 patients with stable COPD and 10 healthy subjects. Arterial blood gas analysis were measured at rest and maximal exertion in incremental testing. Venous blood samples were drawn both at rest and maximal exercise in constant-load exercise testing and NT-proBNP levels were measured. Results NT-proBNP levels did not change significantly during exercise in the patients with stable COPD[ ( 4803. 86 ±1027. 07 ) ng/L vs ( 4572. 39 ±1243. 33 ) ng /L, P = 0. 542 ] and the control group [ ( 4303. 18 ±771. 74) ng/L vs ( 4475. 71 ±1025. 50) ng /L, P = 0. 676] . NT-proBNP levels were not correlated with parameters of cardiopulmonary exercise testing. Conclusion The factors other than cardiac function may contribute to the exercise intolerance in stable COPD patients without heart failure.
Abstract: Objective To find out the factors which influence plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels and assess whether preoperative plasma NT-proBNP levels can predict postoperative outcomes of cardiac surgery. Methods A total of 120 patients including 83 males and 37 females undergoing various cardiac procedures between December 2008 and May 2009 were included in the study. Their age ranged from 25 to 84 years with an average age of 62.13 years. Through pathological diagnosis, 35 patients had heart valve diseases, 74 had coronary artery diseases, 3 had congenital heart diseases and 8 had aortic aneurysm. NT-proBNP, creatinine, cardiac troponin T (cTnT) and creatine kinase-MB (CK-MB) levels were measured preoperatively and 24 hours after operation. Ventilation time, length of stay in ICU or in hospital, and mortality were closely monitored after operation. The following events were regarded as endpoints: (1) ICU stay timegt;4 d; (2) Ventilation timegt;48 h; (3) Death occurred during the first 30 days after operation. Receiver operating characteristic (ROC) curve was used to analyze the prediction function of NTproBNP on endpoint events. Based on the cutoff value, the patients were divided into the NT-proBNP increasing group and nonincreasing group. Univariate and logistic multifactor analysis were adopted to analyze factors which had an influence on preoperative NT-proBNP level. Results NT-proBNP concentration [CM(159mm]increased significantly from 37.5-30 867.0 pg/ml (1 929.12±3 749.44 pg/ml) preoperatively to 177.7-35 000.0pg/ml(2 950.32±4 006.14 pg/ml) 24 hours after operation (t=-2.599, P=0.012). ROC curve demonstrated that a cutoff value above 867 pg/ml preoperatively could predict endpoint events with a sensitivity of 77.8% and a specificity of 62.7%. Ventilation time and length of stay in hospital for the patients in the NT-proBNP increasing group were significantly longer than those of patients in the nonincreasing group (26.44±32.75 h vs. 14.49±9.23 h, t=2.507, P=0.015; 23.70±24.02 d vs. 16.21±8.11 d, t=2.117,P=0.039). Influencing factors on preoperative NTproBNP level included preoperative atrial fibrillation, heart function classification, left ventricular enddiastolic dimension (LVEDD), ejection fraction (EF), pulmonary artery pressure, preoperative creatinine, cTnT and pathological diagnosis. EF (P=0.007) and preoperative atrial fibrillation (P=0.018) were independently associated with preoperative NT-proBNP level. Preoperative NTproBNP was closely related to ventilation time (P=0.015), and length of stay in hospital (P=0.039). Conclusion Preoperative plasma NT-proBNP level presents a high individual variability in patients undergoing cardiac surgery. Ejection fraction and preoperative atrial fibrillation are independently associated with preoperative NT-proBNP level. Preoperative NT-proBNP is a valuable marker in predicting bad outcome in patients undergoing heart surgery.