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.