In low-flow, low gradient aortic stenosis (LFLG-AS i.e. with low left ventricular [LV] ejection fraction), there is no data on the value of the clinical activation ratios of B-type natriuretic peptide (BNP-ratio) versus aminoterminal-proBNP (NT-proBNP-ratio) as surrogates of LV impairment to risk-stratify the patients.

BNP and NT-proBNP-ratios were calculated by dividing the actual serum level by the upper normal reference value for age and sex in 238 prospectively recruited LFLG-AS patients.

After adjustment for the severity of AS, initial treatment (aortic valve replacement [AVR] vs. conservative management), age, sex and the euroSCORE (Model#1), BNP-ratio>7.4 had a trend to predict time to death (HR=2.14[1.00–4.58], P=0.05). NT-proBNP ratio significantly predicted one and three-year mortality (area under the curve [AUC]=0.67±0.04 and 0.66±0.05, both P=0.001), and independently predicted mortality (HR=1.39 [1.11–1.74], per unit LogNT-proBNP-ratio, P=0.004). In a head-to-head comparison, the AUCs for one and three-year mortality were higher with NT-proBNP-ratio versus BNP-ratio (P<0.009). NT-proBNP-ratio but not BNP-ratio independently predicted mortality and significantly improved Model#1 (Likelihood ratio test Chi²=15.953, P=0.0003). The category-free net reclassification index of NT-proBNP-ratio when added to the multivariable model was 0.71 (P=0.008) versus 0.38 (P=0.15) for BNP-ratio. Furthermore, there was a marked survival benefit associated with AVR in patients with NT-proBNP-ratio>11 (62% with severe AS), while those<11 (46% with severe AS) had excellent short-term survival under conservative management (Figure 1).

NT-proBNP-ratio strongly predicts the risk of mortality and is superior to BNP-ratio to risk stratify LFLG-AS patients. The assessment of LV function impairment using NT-proBNP-ratio has important clinical implications and should be complementary to the determination of true AS severity.