The diagnostic value of N-terminal B-type natriuretic peptide in diastolic heart failure: comparison with echocardiographic findings

Objectives: We investigated the value of N-terminal pro-B-type natriuretic peptide (NT-proBNP) to diagnose diastolic heart failure (DHF) without left ventricular (LV) hypertrophy.
Study design: The study included 33 patients (17 males, 16 females) with DHF, who had acute pulmonary congestion and LV ejection fraction (EF) >50% on admission, and were stable for at least six months of follow-up. The control group consisted of 18 hypertensive patients (9 males, 9 females) without cardiac symptoms, whose LV mass indices matched the study group, and EF was >50%. Plasma NT-proBNP levels were measured and all patients were evaluated by echocardiography to examine the relationship between NT-proBNP levels and the ratio of peak early diastolic mitral velocity to peak early diastolic mitral annular velocity (E/E’).
Results: NT-proBNP levels were significantly increased in the DHF group (293.4±52.1 pg/ml vs. 123.1±23.5 pg/ml, p=0.043). Concerning the severity of diastolic dysfunction and NT-proBNP levels, patients with delayed relaxation (n=24) did not differ from the controls, whereas those with pseudonormal (n=5) and restrictive (n=4) forms had significantly elevated NT-proBNP levels (p=011). In ROC analysis, an NT-proBNP level of ≥490 pg/ml predicted DHF with 40% sensitivity and 94% specificity. The mean E/E’ values were 5.4, 15.4, and 17.6 in patients with delayed relaxation, pseudonormal, and restrictive forms, respectively. When all the patients were examined in three groups according to the E/E’ values (E/E’<8; E/E’=8-15; E/E’>15), those having E/E’ >15 had significantly higher NT-proBNP levels (p=0.0001). There was a highly significant relationship between E/E’ and NT-proBNP (r=0.761, p=0.001). In ROC analysis, a threshold of 269.1 pg/ml for NT-proBNP predicted E/E’ >15 with 90% sensitivity and 73% specificity. In logistic regression analysis, left atrial diameter (p=0.018) and E/E’ (p=0.05) were independent factors affecting the NT-proBNP level.
Conclusion: Plasma NT-proBNP levels are elevated in DHF independently from LV hypertrophy. NT-proBNP levels provide estimation of LV end-diastolic pressure in symptomatic hypertensive patients with preserved systolic LV function.

Keywords: Echocardiography, Doppler, heart failure, diastolic/diagnosis; natriuretic peptide, brain; ventricular function, left.