Author + information
- Received February 6, 2015
- Revision received February 25, 2015
- Accepted March 9, 2015
- Published online August 1, 2015.
- Antoni Bayés-Genís, MD, PhD∗,†∗ (, )
- Jaume Barallat, MD‡,
- Domingo Pascual-Figal, MD, PhD§,
- Julio Nuñez, MD, PhD‖,¶,
- Gema Miñana, MD#,
- Jesús Sánchez-Mas, PhD§,
- Amparo Galan, MD, PhD‡,
- Juan Sanchis, MD, PhD¶∗∗,
- Elisabet Zamora, MD, PhD∗,†,
- María Teresa Pérez-Martínez, MD§ and
- Josep Lupón, MD, PhD∗,†
- ∗Cardiology Service and Heart Failure Unit, Hospital Universitari Germans Trias i Pujol, Badalona, Spain
- †Department of Medicine, Autonomous University of Barcelona, Barcelona, Spain
- ‡Biochemistry Service, Hospital Universitari Germans Trias i Pujol, Badalona, Spain
- §Cardiology Department, Hospital Virgen de la Arrixaca, Department of Medicine, University of Murcia, Murcia, Spain
- ‖Biochemistry Service, Hospital Clínico Universitario, Valencia, Spain
- ¶University of Valencia, Valencia, Spain
- #Cardiology Service, Hospital Clínico Universitario, Valencia, Spain
- ∗∗Cardiology Service, Hospital de Manises, Valencia, Spain
- ↵∗Reprint requests and correspondence:
Dr. Antoni Bayés-Genís, Cardiology Service, Hospital Universitari Germans Trias i Pujol, Carretera de Canyet s/n 08916, Badalona, Spain.
Objectives This study sought to examine the prognostic value of the soluble form of neprilysin (sNEP) in acute heart failure (AHF) and sNEP kinetics during hospital admission.
Background sNEP was recently identified in chronic heart failure (HF) and was associated with cardiovascular outcomes.
Methods A total of 350 patients (53% women, mean 72.6 ± 10.7 years of age) were included in the study. Primary endpoints were composites of cardiovascular death or HF hospitalizations at short-term (2 months) and long-term (mean: 1.8 ± 1.2 years) follow-up. sNEP was measured using an ad hoc–modified enzyme-linked immunosorbent assay, and its prognostic value was assessed using Cox regression analyses. In a subgroup of patients, sNEP was measured both at admission and at discharge (n = 92).
Results Median admission sNEP concentrations were 0.67 ng/ml (Q1 to Q3: 0.37 to 1.29), and sNEP was significantly associated, in age-adjusted Cox regression analyses, with the composite endpoint at short-term (hazard ratio [HR]: 1.29; 95% confidence interval [CI]: 1.04 to 1.61; p = 0.02) and long-term (HR: 1.23; 95% CI: 1.01 to 1.05; p = 0.003) follow-up. In multivariate Cox analyses that included clinical variables and N-terminal prohormone of brain natriuretic peptide (NT-proBNP) concentration, sNEP concentration at admission showed a clear trend toward significance for the composite endpoint at 2 months (HR: 1.22; 95% CI: 0.97 to 1.53; p = 0.09) and remained significant at the end of follow-up (HR: 1.21; 95% CI: 1.04 to 1.40; p = 0.01). At discharge, sNEP levels decreased from 0.70 to 0.52 ng/ml (p = 0.06).
Conclusions Admission sNEP concentration was associated with short- and long-term outcomes in AHF, and dynamic sNEP concentrations were observed during hospital admission. These preliminary data may be hypothesis-generating for the use of NEP inhibitors in AHF.
The enzyme neprilysin (NEP) plays a central role in neurohormonal regulation in heart failure (HF) by breaking down a plethora of vasoactive peptides (1). The extracellular domain of NEP was identified recently in ambulatory chronic HF patients as a circulating soluble form of NEP (sNEP) (2). In a large, real-life, consecutive cohort of 1,069 patients with long-term follow-up, sNEP was found to be a good pathobiological surrogate for cardiovascular mortality and morbidity (2).
In acute HF (AHF), a multitude of regulatory and counter-regulatory neurohormonal axes are acutely overexpressed (3), but no evidence is available for sNEP concentrations in AHF. Therefore, this pilot multicenter study aimed to identify the concentrations and prognostic values of sNEP in AHF and the sNEP kinetics during hospital admission.
From May 2008 to December 2013, 350 patients (mean 72.6 ± 10.7 years of age) admitted for AHF were consecutively included in the study. Inclusion criteria and blood sample collection descriptions have been described elsewhere (4,5). All participants provided written informed consent, and the local ethics committees approved the study. Primary outcomes were a composite of cardiovascular death or HF hospitalization at 2 months and at the end of follow-up.
Human NEP concentrations were measured using a modified sandwich immunoassay (human NEP/Cd10 enzyme-linked immunosorbent assay [ELISA] kit; product no. SK00724-01, lot no. 20112070; Aviscera Biosciences, Santa Clara, California) with previously reported ad hoc modifications to improve the analytical sensitivity of the method (2). Intra- and interassay coefficients of variation were 3.7% and 8.9%, respectively.
Categorical variables were expressed as percentages. Continuous variables were expressed as mean ± SD or medians (quartiles [Q]1 to Q3) according to normal or nonnormal distributions. Normal distribution was assessed with normal Q-Q plots. Values for sNEP and N-terminal prohormone of brain natriuretic peptide (NT-proBNP) concentrations were log-transformed, and 1 SD was used to calculate the hazard ratio (HR). Cox regression analyses including sNEP with age as a covariate and multivariate Cox regression analyses were performed.
Clinical characteristics of patients are shown in Table 1. Median sNEP concentration was 0.67 ng/ml (Q1 to Q3: 0.37 to 1.29). At 2 months, 60 composite endpoints, 28 cardiovascular deaths, and 36 HF rehospitalizations had occurred. At the end of follow-up (mean 1.8 ± 1.2 years), 158 composite endpoints, 81 cardiovascular deaths, and 120 HF rehospitalizations had occurred. As a continuous variable in age-adjusted Cox regression analyses, sNEP concentrations were significantly associated with the composite endpoint at 2 months (HR: 1.29; 95% confidence interval [CI]: 1.04 to 1.61; p = 0.02) and at the end of follow-up (HR: 1.23; 95% CI: 1.01 to 1.05; p = 0.003). sNEP concentration was also associated with cardiovascular death at 2 months (HR: 1.38; 95% CI: 1.01 to 1.88; p = 0.04). Figure 1 shows survival-free event curves for composite endpoint at 2 months and long-term follow-up for patients with sNEP concentrations below or above the median.
In a multivariate Cox regression analyses that included clinical variables (age, sex, cause of ischemia of HF, left ventricular ejection fraction [LVEF], hemoglobin and creatinine concentrations) and NT-proBNP values, sNEP showed a clear trend toward significance for the composite endpoint at 2 months (HR: 1.22; 95% CI: 0.97 to 1.53; p = 0.09). In the long-term follow-up analysis, if treatment was not incorporated in the model, both sNEP and NT-proBNP were independent predictors of the composite endpoint (p = 0.015 and p = 0.006, respectively). However, when treatment with beta-blockers, angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers, and mineralocorticoid receptor antagonists were also incorporated in the model, sNEP remained significant at the end of follow-up (HR: 1.21; 95% CI: 1.04 to 1.40; p = 0.01), but NT-proBNP lost its prognostic significance for the combined endpoint (HR: 1.19; 95% CI: 0.96 to 1.47; p = 0.12).
In a small sample of 92 patients, sNEP was also measured at discharge. In these patients, the median value decreased from 0.70 ng/ml at admission to 0.52 ng/ml at discharge (p = 0.06). We did not find significant differences between patients with and without sNEP reduction relative to age, sex, LVEF, cause of ischemia, treatment during admission, number of hospitalization days, or initial NT-proBNP and sNEP concentrations; nevertheless, sNEP reduction tended to be more frequent in nonischemic patients (62% vs. 42%, respectively, in ischemic patients; p = 0.06). In the subgroup of patients with serial sNEP, HRs for outcomes at 60 days were 0.70 (95% CI: 0.22 to 2.33) and 0.55 (95% CI: 0.91 to 3.27) for the composite endpoint and cardiovascular death, respectively; although in a positive direction, in both cases, p values were nonsignificant, very likely due to the limited number of events.
Assessing risk in the context of AHF is a challenging proposal. Currently, natriuretic peptides are state-of-the-art prognostic biomarkers in AHF patients (6). However, use of biomarkers beyond natriuretic peptides for risk assessment in patients with AHF is under examination. Here, we provide evidence for sNEP as a novel prognostic biomarker in AHF in both the short and the long term. Indeed, NEP is responsible for the breakdown of a plethora of vasoactive neurohormones activated in AHF, including natriuretic peptides. Remarkably, in long-term follow-up, sNEP concentrations, reflective of comprehensive neurohormonal activation, remained strongly significant for the combined endpoint, whereas NT-proBNP, which is reflective only of the natriuretic peptide axis, lost significance.
The dynamic behavior of sNEP observed in the setting of AHF is similar to that of other biomarkers, such as natriuretic peptides and ST2. The decreased sNEP concentrations as the clinical status stabilizes may mirror the return to quiescence of the acutely activated neurohormonal axes. In our chronic HF cohort, we found a median sNEP concentration of 0.64 ng/ml (2), lower than that found in the present AHF cohort. Although the subsample with sNEP kinetics was small, a reduction with stability was clearly suggested, an observation that conforms to the lower sNEP concentration found in chronic patients. Additional studies beyond the scope of the present report are needed to address whether sNEP kinetics respond to specific therapeutic strategies.
NEP inhibition may become mainstream during 2015 as LCZ696 is approved by regulatory agencies. Results of the PARADIGM-HF (Prospective Comparison of ARNI with ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure) trial indicate that chronic ambulatory HF patients are candidates for replacement of enalapril with LCZ696 (7), but what to do in AHF in the post-PARADIGM era is uncertain. Some argue that LCZ696 therapy should be initiated as soon as possible during hospital admission, whereas others argue that hospitalized patients should receive enalapril first. Our data provide a better understanding of sNEP in AHF and may be hypothesis generating for the use of NEP inhibitors in AHF.
As main limitations, we must acknowledge that drawing definitive conclusions is limited by the sample size and that we have no data for sNEP stability while the samples were frozen, so we cannot ignore the possibility that sNEP concentrations would have been different in fresher samples.
In summary, this pilot multicenter study suggests that admission sNEP concentrations are associated with short- and long-term outcomes in AHF and that sNEP concentrations are dynamic during hospital admission. These preliminary data may argue in favor of the use of NEP inhibitor in AHF.
COMPETENCY IN MEDICAL KNOWLEDGE: Neprilysin is a crucial enzyme that breaks down a multitude of vasoactive peptides in patients with HF, and inhibition of neprilysin as a therapeutic target is associated with reductions in cardiovascular morbidity and mortality.
TRANSLATIONAL OUTLOOK: Prospective trials are needed to assess whether neprilysin inhibition based on measurements of plasma neprilysin concentrations in patients with acute HF is clinically useful.
The authors thank the nurses in the heart failure units for collecting data and for their invaluable work.
This work was supported by research network Red de Investigación Cardiovascular grants RD12/0042/0047, RD12/0042/0049, and RD12/0042/0010. The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- acute heart failure
- angiotensin receptor neprilysin inhibitor
- heart failure
- left ventricular ejection fraction
- N-terminal prohormone of brain natriuretic peptide
- soluble neprilysin
- Received February 6, 2015.
- Revision received February 25, 2015.
- Accepted March 9, 2015.
- American College of Cardiology Foundation
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