Original article
Prognostic utility of NT-proBNP in acute exacerbations of chronic pulmonary diseases

https://doi.org/10.1016/j.ejim.2010.12.002Get rights and content

Abstract

Background

The prognostic value of NT-proBNP levels in patients admitted to hospital due to acute exacerbations of chronic pulmonary diseases (CPDs) is unknown.

Setting

Internal Medicine units at two general hospitals.

Methods

NT-proBNP levels were obtained within 72 h after admission in 192 consecutive patients with acute exacerbations of CPDs and no history of heart failure or diuretic treatment. Clinical characteristics and main outcomes were assessed over a 12-month follow-up. NT-proBNP cut-points for outcomes were obtained by ROC (receiver operating characteristics) curve analysis.

Results

Chronic obstructive lung disease (69.3%) and chronic asthma (22.4%) were the most prevalent CPDs, and non-pneumonic acute respiratory infection (72.4%) and pneumonia (22.9%) were the most frequent causes of exacerbation. Atrial flutter or fibrillation rate was 11%. During the one-year follow-up period, 22 patients died, 42 were re-admitted, 46 received new long-term oxygen therapy, and 39 received new diuretic treatment.

NT-proBNP values correlated with hospitalisation days. NT-proBNP values over 587.9 pg/ml were associated with significantly raised one-year mortality (OR = 3.90; 95% IC 1.46–10.47; p = 0.006) and over 782.2 pg/ml with cardio-pulmonary deaths (OR = 6.38; 95% IC 1.91–21.3; p = 0.002). That association persisted after adjustment for age, gender, creatinine levels and cardiac rhythm. NT-proBNP values over 628.7 pg/ml were associated with significantly higher probability of new diuretic treatment (OR = 4.38; IC 95% 2.07–9.25; p < 0.001). The negative predictive values for these cut-points ranged from 89% to 97%.

Conclusion

NT-proBNP levels below 587.9 pg/ml in patients with acute exacerbations of CPD were associated with favourable one-year outcomes.

Introduction

B-type natriuretic peptides (BNP and NT-proBNP) are released by the heart to the bloodstream in response to increased ventricular volume or pressure [1], [2]. B-type natriuretic peptides concentration correlates clearly with pulmonary capillary pressure [3], telediastolic intraventricular pressure and left ventricular ejection fraction [4], [5]. There is also a weak-positive correlation between BNP concentration and main pulmonary arterial pressure, as assessed by echocardiography [6]. B-type natriuretic peptides have been used in clinical practice in the screening of patients with dyspnoea [7], [8], [9], asymptomatic ventricular dysfunction, and in the management of patients particularly those with cardiac diseases [10]. Moreover, B-type natriuretic peptides possess prognostic value for general and cardiovascular morbidity, even in patients without heart failure [11], [12].

NT-proBNP levels have been less extensively studied in pulmonary diseases. Raised NT-proBNP levels have been found in patients with chronic pulmonary diseases (CPD) [13], cor pulmonare [6], [14], and pulmonary embolism [15] as a consequence of pulmonary hypertension [13]. As well as this, B-type natriuretic peptide is a short-term independent predictor of mortality in patients with CPD [13] and primary pulmonary hypertension [16].

We hypothesize that elevated NT-proBNP levels could help to stratify patients with acute exacerbations of CPD before they develop symptomatic right heart failure. The aim of the study was to determine the prognostic utility of NT-proBNP in that scenario.

Section snippets

Patients and setting

Consecutive patients admitted to the hospital due to acute exacerbation of chronic pulmonary diseases and interviewed within 72 h of admission were included in the study. Eligible chronic pulmonary diseases were chronic bronchitis, emphysema, chronic asthma, pulmonary fibrosis, pleural fibrosis, and pneumoconiosis. Eligible patients had basal functional statuses II–IV (using the NYHA scale as a reference) and no previous history of symptoms related to pulmonary hypertension or right heart

Results

One-hundred ninety two patients were included in the study. Table 1 shows the baseline demographic and clinical characteristics of these patients. Most of them (78.6%) were male and median age was 75 years. Smoking-related chronic obstructive pulmonary disease and chronic asthma accounted for 92% of the underlying pulmonary diseases. Acute deterioration was due to acute exacerbation without chest X-ray infiltrates or pneumonia in 95% of the cases. Atrial flutter or fibrillation was present in

Discussion

The prognostic value of NT-proBNP levels in unselected populations is well known [11], [19]. Our study found that NT-proBNP levels are significantly raised during acute exacerbations of CPD, in the absence of clinically apparent heart failure. Also, NT-proBNP levels associated with adverse outcomes were within the non-diagnostic range for heart failure. NT-proBNP levels above 587.9 pg/ml on admission showed a significant association with any cause mortality, and above 780 pg/ml due to

Learning points

  • NT-proBNP levels below 600 pg/ml on presentation have a high negative predictive value for adverse outcomes in patients with acute exacerbations of chronic pulmonary diseases.

Acknowledgements

Supported in part by the Project 06061-00, Junta de Comunidades de Castilla La-Mancha, Spain. We are grateful to Uta M. Klepzig for helping in the preparation of the manuscript.

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