N-Terminal pro-Brain Natriuretic Peptide Plasma Levels in Healthy Subjects and Patients with Heart Diseases ^†

Purpose: N-terminal pro-Brain Natriuretic Peptide (NT-proBNP) was recently introduced as a simple tool for the diagnosis of congestive heart failure (CHF). The aim of this study was primarily to evaluate NT-proBNP as a marker of CHF in a large, unselected population and in addition to investigate the relationship between NT-proBNP and clinical parameters such as age, gender, body mass index, exercise parameters, chest pain, blood pressure, heart rate, comorbidities, any therapy. Methods: The studied population consisted of 432 subjects undergoing a cardiological workup in a large cruise ship’s medical center, during a 7-day sea voyage in May 2003 and May 2004. Designed as a cross sectional study, the subjects filled in a medical questionnaire, underwent a physical examination, were assessed for NT-proBNP plasma levels and performed a bicycle exercise test. Furthermore, in a subgroup of 88 subjects an echocardiographic examination was performed. Results: Of the 432 subjects (mean age 66 ± 10 years; 48.8% male) 8.3% were clinically healthy, whereas 71.2% were hypertensive and 46.8% had symptoms of CHF. Median NT-proBNP levels increased from 78.8 ng/l in subjects without CHF to 87.1 ng/l in subjects with NYHA-class I, to 121.6 ng/l in subjects with NYHA-class II and to 157.2 ng/l in subjects with NYHA-class III CHF. The association of NT-proBNP with NYHA-classes was highly significant (p = 0.0001). Furthermore, NT-proBNP was an independent predictor of NYHA class II chronic heart failure (p = 0.02). There were significant positive correlations of the natural logarithm of NT-proBNP with age and pulse pressure and significant inverse correlations with Body Mass Index, maximum exercise level, left ventricular ejection fraction, heart rate and diastolic blood pressure. Strong independent predictors of NT-proBNP were age (p <0.0001), betablocker therapy (p = 0.02), gender (p <0.0001), angiotensinconverting- enzyme (ACE) inhibitor therapy (p = 0.02), heart rate (p = 0.006), chest pain (p = 0.02). Conclusions: This study confirms NT-proBNP as a valuable diagnostic tool for CHF in an unselected population. Several physiological and clinical parameters were found to be significantly related to NT-proBNP levels, the strongest being age, betablocker therapy, gender, ACE inhibitor therapy.