B-Type Natriuretic Peptide in Low-Flow, Low-Gradient Aortic Stenosis

Abstract

Background— The prognostic value of B-type natriuretic peptide (BNP) is unknown in low-flow, low-gradient aortic stenosis (AS). We sought to evaluate the relationship between AS and rest, stress hemodynamics, and clinical outcome. Methods and Results— BNP was measured in 69 patients with low-flow AS (indexed effective orifice area <0.6 cm 2 /m 2 , mean gradient ≤40 mm Hg, left ventricular ejection fraction ≤40%). All patients underwent dobutamine stress echocardiography and were classified as truly severe or pseudosevere AS by their projected effective orifice area at normal flow rate of 250 mL/s (effective orifice area ≤1.0 cm 2 or >1.0 cm 2 ). BNP was inversely related to ejection fraction at rest (Spearman correlation coefficient r s =−0.59, P <0.0001) and at peak stress ( r s =−0.51, P <0.0001), effective orifice area at rest ( r s =−0.50, P <0.0001) and at peak stress ( r s =−0.46, P =0.0002), and mean transvalvular flow ( r s =−0.31, P =0.01). BNP was directly related to valvular resistance ( r s =0.42, P =0.0006) and wall motion score index ( r s =0.36, P =0.004). BNP was higher in 29 patients with truly severe AS versus 40 with pseudosevere AS (median, 743 pg/mL [Q1, 471; Q3, 1356] versus 394 pg/mL [Q1, 191 to Q3, 906], P =0.012). BNP was a strong predictor of outcome. In the total cohort, cumulative 1-year survival of patients with BNP ≥550 pg/mL was only 47±9% versus 97±3% with BNP <550 ( P <0.0001). In 29 patients who underwent valve replacement, postoperative 1-year survival was also markedly lower in patients with BNP ≥550 pg/mL (53±13% versus 92±7%). Conclusions— BNP is significantly higher in truly severe than pseudosevere low-gradient AS and predicts survival of the whole cohort and in patients undergoing valve replacement.