Predictive value of B-type natriuretic peptides in detecting latent left ventricular diastolic dysfunction in beta-thalassemia major.

BACKGROUND: Beta-thalassemia major is a unique disease characterized by early diastolic dysfunction, related exclusively to iron myocardial deposition. N-terminal-proBNP(amino-terminal) (NT-proBNP) and B-type natriuretic peptide (BNP) are sensitive biomarkers for the detection of asymptomatic left ventricular (LV) dysfunction, and they have important diagnostic and prognostic implications. Using beta-thalassemia as a model disease with isolated diastolic dysfunction, we sought to investigate the predictive value of NT-proBNP and BNP levels in comparison with the conventional and new Doppler echocardiography indexes in detecting this disorder.

METHODS: Seventy beta-thalassemia major patients (mean age 27.2 +/- 12.5 years) with normal LV systolic function (mean LV ejection fraction = 59% +/- 6.8%), and 50 healthy age-matched adults (control group: mean age 25.5 +/- 10.1 years, mean LV ejection fraction = 60% +/- 4.5%) were included. All subjects were studied thoroughly by tissue Doppler echocardiography and blood samples were taken for plasma NT-proBNP and BNP measurements at the same time. To examine LV diastolic function, patients were divided in 3 groups according to the E mitral/E mitral annulus ratio (E/E'): group A, patients without diastolic dysfunction: E/E' ratio <8; group B, patients with suspected diastolic dysfunction: E/E' ratio 8 to 15; group C, patients with documented diastolic dysfunction: E/E' ratio, >15.

RESULTS: NT-proBNP and BNP levels were higher in thalassemic patients compared with the control group (NT-proBNP levels: 80 +/- 19 vs 21 +/- 4 pg/mL, P < .001; BNP levels: 34 +/- 6 vs 9 +/- 3 pg/mL, P < .001). NT-proBNP levels showed a statistically significant increase in group C in comparison to groups A and B, which was also detected between groups A and B (A vs B: P < .05). BNP levels were also significantly increased in group C in comparison to the other 2 groups, but there was no statistically significant difference between groups A and B. Using receiver operating characteristic analysis, NT-proBNP at a cut point of 49.2 pg/mL was highly accurate (area under curve: 0.97, P < .001) in ruling out diastolic dysfunction (E/E' <8) with a sensitivity of 93.7% and a specificity of 89.6%.

CONCLUSIONS: BNP and NT-proBNP levels are significantly increased in documented left ventricular diastolic dysfunction, while NT-proBNP seems to have better predictive value in detecting latent left ventricular diastolic dysfunction in beta-thalassemia major.