B-Type Natriuretic Peptide and High-Sensitivity Cardiac Troponin for Risk Stratification in Low-Flow, Low-Gradient Aortic Stenosis: A Substudy of the TOPAS Study

Abstract

Objectives: The objective of this study was to determine the prognostic value of combined measures of B-type natriuretic peptide (BNP) and high-sensitivity cardiac troponin T (hsTnT) in patients with low-flow, low-gradient aortic stenosis (LF-LG AS) who had either a preserved or reduced left ventricular ejection fraction (LVEF).

Background: An elevated BNP level is associated with increased risk of mortality in patients with LF-LG AS. The incremental prognostic value of hsTnT in these patients is unknown.

Methods: Ninety-eight patients (74 ± 10 years; 75% men) with LF-LG AS (LVEF <50% and/or stroke volume index <35 ml/m², mean gradient <40 mm Hg, indexed aortic valve area <0.6 cm²/m²) who were prospectively enrolled in the TOPAS (Truly or Pseudo-Severe Aortic Stenosis) study were included. The cohort was divided into 3 groups according to BNP and hsTnT levels: group A: BNP <550 pg/ml and hsTnT <15 ng/l; group B: BNP ≥550 pg/ml or hsTnT ≥15 ng/l; and group C: BNP ≥550 pg/ml and hsTnT ≥15 ng/l. The primary endpoint was all-cause mortality.

Results: Twenty-seven patients (27%) were in group A, 39 (40%) were in group B, and 32 (33%) were in group C. During a median follow-up of 2.8 years, 43 patients died. Two-year mortality was higher in group C (41 ± 9%) than in group B (23 ± 7%) and group A (5 ± 4%) (p = 0.002). In group B, there was no significant difference in 2-year mortality rates between the subgroup with hsTnT ≥15 ng/l (n = 29) and the subgroup with BNP ≥550 pg/ml (n = 10) (26 ± 9% vs. 11 ± 10%, respectively; p = 0.21). In multivariable analysis adjusted for age, type of treatment (aortic valve replacement vs. conservative therapy), coronary artery disease, and LVEF, being in group C remained independently associated with an increased risk of mortality (hazard ratio [HR]: 4.25; p = 0.023), and group B tended to have higher mortality (HR: 3.63; p = 0.058) compared with group A.

Conclusions: This study demonstrated the usefulness of combined measures of BNP and hsTnT to enhance risk stratification in patients with LF-LG AS. Patients with elevation of both BNP and hsTnT had a markedly increased risk of mortality. (Multicenter Prospective Study of Low-Flow Low-Gradient Aortic Stenosis [TOPAS]; NCT01835028).

Keywords: BNP; LV function; aortic stenosis; echocardiography; high-sensitivity troponin; low-flow; low-gradient.