B-type natriuretic peptide (BNP) - application in differential diagnosis of dyspnoea

Objective:
To assess the benefit of determination of B-type natriuretic peptide (NT-pro BNP) in differential diagnosis of dyspnoea (differentiation of dyspnoea associated with myocardial affection from other type of dyspnoea) in settings of our admission internal outpatient clinic of the hospital Na Františku.


Patient population:
We have enrolled 68 patients (37 women and 31 men) of an average age of 75.2 years complaining of dyspnoea during preliminary examination at the outpatient clinic in the study.


Procedures:
We have drawn blood samples from patients immediately on admission for an immediate examination (statim) with complete biochemical profile including levels of NT-pro BNP. During hospitalisation we completed a variety of examinations, which were essentially necessary to the establishment of final diagnosis. On the basis of examinations performed and their results we divided patients into three groups: I.a - patients with cardiac aetiology of dyspnoea without LV dysfunction, I.b - patients with cardiac aetiology of dyspnoea with LV dysfunction, II. - patients with non-cardiac aetiology of dyspnoea (control group).

Results: 68 probands were examined in total. 51 patients with cardiac aetiology of dyspnoea were enrolled in the first group, 17 patients with non-cardiac aetiology of dyspnoea were enrolled in the second group (controls). Mean value of NT-pro BNP in the first group was 9,198.45 ng/l, standard deviation was 10,596.1; in the second group with non-cardiac diagnosis the mean value of NT-pro BNP was 304.1 ng/l, standard deviation was 566.64. Relatively higher value of NT-pro BNP in non-cardiac group compared to literature sources (norm in men is up to 100 ng/l and in women up to 150 ng/l) [15,23,26] was influenced by one patient with decompensated liver cirrhosis, mean value of NT-pro BNP was 2,519.0 ng/l, and by the relatively small number of patients in control group. Nevertheless mean values of NT-pro BNP in the group with cardiac aetiology of dyspnoea are statistically significantly higher than in the control non-cardiac group (p < 0.01). In the follow-up we focused on the subgroup formed by patients with left ventricular dysfunction. We divided patients into 3 groups based on NYHA classification and we compared values of NT-pro BNP with results of echocardiographic examinations we performed during hospitalisation in our hospital in two days after the admission. We noticed statistically significant increase of NT-pro BNP in the relationship to NYHA classification (correlation coefficient 0.41). We found that the value of NT-pro BNP significantly correlates with left ventricular ejection fraction (correlation coefficient 0.46). In NYHA II group the mean LVEF was 43.75%, mean value of NT-pro BNP was 1,167.3 ng/l; in NYHA III group the mean LVEF was 38.70% and the mean value of NT-pro BNP was 4276.5 ng/l; in NYHA IV group the mean value of LVEF was 31.20% and the mean value of NT-pro BNP was 19,581.2 ng/l.

Conclusions:
The determination of natriuretic peptides is simple method, which belongs among essential parts especially in diagnosis of advanced forms of heart failure. The great advantage of this method is its availability, good reproducibility, high negative predictive value and independence on the presence of qualified specialist. The determination of NT-pro BNP became an important helper in stratification of patients coming with dyspnoea and markedly helps and advances the decision making process of the proper therapeutic approach.

Keywords: B-type natriuretic peptide; dyspnoea; differential diagnosis of dyspnoea; left ventricular ejection fraction