Objective: Brain natriuretic peptide (BNP) is a peptide, which has recently been used in the differential diagnosis and follow-up of patients with heart failure. Our aim in the present prospective and diagnostic designed study is to investigate the role of BNP in determining the etiology of dyspnea and to evaluate its relation with newer echocardiographic parameters.
Methods: Thirty-four patients presenting to the emergency department with dyspnea and fulfilling the Framingham criteria for heart failure were included in the study. Blood samples were obtained in the first hour of presentation for measurement of BNP levels from all patients. Detailed transthoracic two-dimensional, Doppler and tissue Doppler echocardiographic studies were then performed within 24 hours of presentation. Statistical analyses were performed using Student's t-test for independent samples, Mann Whitney U test and Pearson or Spearman correlation tests.
Results: Plasma BNP levels were found to be significantly correlated with left ventricular end-systolic and end-diastolic diameter, left atrial diameter and the degree of mitral insufficiency (r=0.46, p=0.007; r=0.39, p=0.02; r=0.32, p=0.065; r=0.50, p=0.014, respectively). A significant inverse correlation was observed between plasma BNP levels and left ventricular ejection fraction (r=-0.5, p=0.003). When the patients were grouped according to their BNP levels, the mean ejection fraction of the group with BNP levels below median (578 pg/l) was 60.65+/-13.84%, whereas the mean ejection fraction of the group with BNP levels of 578 pg/l or above (BNP 2) was 49.41+/-15.26% (p=0.027). Out of parameters reflecting left ventricular diastolic functions, only transmitral Epeak/Apeak ratio was found to be significantly associated with BNP levels (r=0.4, p=0.05). Tissue Doppler study revealed significant correlations between BNP levels and right ventricular basal and midsystolic velocities (r=-0.507, p=0.008; r=-0.562, p=0.005, respectively) while none of the left ventricular tissue velocities displayed significant correlation with BNP values.
Conclusion: Plasma BNP levels are found to be significantly associated with conventional echocardiographic parameters reflecting left ventricular systolic and diastolic functions and tissue Doppler velocities reflecting right ventricular functions. Our findings are in agreement with the notion that plasma BNP levels are beneficial in the differential diagnosis of patients admitted to emergency service with acute dyspnea.