B-Type Natriuretic Peptide in Low-Flow, Low-Gradient Aortic Stenosis
Relationship to Hemodynamics and Clinical Outcome: Results From the Multicenter Truly or Pseudo-Severe Aortic Stenosis (TOPAS) Study
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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 cm2/m2, 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 cm2 or >1.0 cm2). BNP was inversely related to ejection fraction at rest (Spearman correlation coefficient rs=−0.59, P<0.0001) and at peak stress (rs=−0.51, P<0.0001), effective orifice area at rest (rs=−0.50, P<0.0001) and at peak stress (rs=−0.46, P=0.0002), and mean transvalvular flow (rs=−0.31, P=0.01). BNP was directly related to valvular resistance (rs=0.42, P=0.0006) and wall motion score index (rs=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.
Received August 11, 2006; accepted March 19, 2007.