Importance of iron deficiency in patients with chronic heart failure as a predictor of mortality and hospitalizations: insights from an observational cohort study

Soluble Transferrin Receptor as Iron Deficiency Biomarker: Impact on Exercise Capacity in Heart Failure Patients

The soluble transferrin receptor (sTfR) is a marker of tissue iron status, which could indicate an increased iron demand at the tissue level. The impact of sTfR levels on functional capacity and quality of life (QoL) in non-anemic heart failure (HF) patients with otherwise normal systemic iron status has not been evaluated. We conducted an observational, prospective, cohort study of 1236 patients with chronic HF. We selected patients with normal hemoglobin levels and normal systemic iron status. Tissue iron deficiency (ID) was defined as levels of sTfR > 75th percentile (1.63 mg per L). The primary endpoints were the distance walked in the 6 min walking test (6MWT) and the overall summary score (OSS) of the Minnesota Living with Heart Failure Questionnaire (MLHFQ). The final study cohort consisted of 215 patients. Overall QoL was significantly worse (51 ± 27 vs. 39 ± 20, p-value = 0.006, respectively), and the 6 MWT distance was significantly worse in patients with tissue ID when compared to patients without tissue ID (206 ± 179 m vs. 314 ± 155, p-value < 0.0001, respectively). Higher sTfR levels, indicating increased iron demand, were associated with a shorter distance in the 6 MWT (standardized β = -0.249, p < 0.001) and a higher MLHFQ OSS (standardized β = 0.183, p-value = 0.008). In this study, we show that in patients with normal systemic iron parameters, higher levels of sTfR are strongly associated with an impaired submaximal exercise capacity and with worse QoL.

Association between iron deficiency and hospitalization rate in community-dwelling older adults: A 3-year prospective observational study of DO-HEALTH

BACKGROUND

Iron deficiency (ID) is associated with negative health outcomes in older adults. However, data on the impact of ID on the number of hospitalizations and length of hospital stay (LOS) is lacking.

OBJECTIVE

To explore the associations between baseline ID and the number of hospitalizations and between baseline ID and at least one LOS ≥5 days in community-dwelling older adults.

METHODS

This is a secondary observational analysis of a randomized controlled trial including 2157 community-dwelling adults aged ≥70 years without major diseases at baseline. The main exposure was defined as ID (soluble transferrin receptor [sTfR] concentrations >28.1 nmol/L) at baseline. The primary outcome was the number of hospitalizations over a 3-year follow-up. The secondary outcome was having at least one LOS ≥5 days over the study period among individuals with one or more hospitalizations. Interaction between ID and anemia (hemoglobin <130 g/L for men and <120 g/L for women) was also investigated.

RESULTS

Baseline sTfR concentration was determined in 2141 participants (median age 74.0 years). At 3 year, 1497 hospitalizations were reported with an incidence rate of hospitalization of 0.26 per person-year (95% CI: 0.24, 0.28). Overall, baseline ID was associated with a 24% increased incidence rate of hospitalization (incidence rate ratio: 1.24; 95% CI: 1.05, 1.45) over 3 years. This association was independent of anemia status at baseline since the interaction between ID and anemia at baseline was not significant. Moreover, ID was not significantly associated with having a LOS ≥5 days (OR: 1.40; 95% CI: 1.00, 1.97) among participants with at least one hospitalization over 3 years.

CONCLUSIONS

ID is associated with increased hospitalization rate and not associated with LOS ≥5 days among generally healthy older adults. Efforts to minimize ID in older adults may improve overall health and optimize healthcare costs.

Why Iron Deficiency in Acute Heart Failure Should Be Treated: A Real-World Clinical Practice Study

Background. This study aims to determine whether the administration of ferric carboxymaltose (FCM) in patients with acute heart failure (AHF) and iron deficiency (ID) improves morbidity and mortality. Methods. We studied 890 consecutive patients admitted for AHF. Patients were divided into six groups according to reduced left ventricular ejection fraction (HFrEF) or preserved (HFpEF), presence of ID, and administration of FCM. Emergency visits, re-admissions, and all-cause mortality were assessed at 6 months. Results. The overall prevalence of ID was 91.2%. In the HFrEF group, no differences were found in isolated events when patients with untreated vs. treated ID were compared, while differences were found in the combined event rate (p = 0.049). The risk calculation showed an absolute risk reduction (ARR) of 10% and relative risk reduction (RRR) of 18%. In HFpEF there was a positive trend with regard to the combined event (p = 0.107), with an ARR of 9% and an RRR of 15%. The number of patients we needed to treat to prevent a combined event was 10.5 in HFrEF and 10.8 in HFpEF. Conclusions. FCM in AHF reduced the combined event rate of emergency visits, re-admission, and all-cause death at 6 months in HF with left ventricular ejection fraction <50%, and showed a positive trend in HFpEF.

Blood Differential Gene Expression in Patients with Chronic Heart Failure and Systemic Iron Deficiency: Pathways Involved in Pathophysiology and Impact on Clinical Outcomes

Background: Iron deficiency is a common disorder in patients with heart failure and is related with adverse outcomes and poor quality of life. Previous experimental studies have shown biological connections between iron homeostasis, mitochondrial metabolism, and myocardial function. However, the mechanisms involved in this crosstalk are yet to be unfolded. Methods: The present research attempts to investigate the intrinsic biological mechanisms between heart failure and iron deficiency and to identify potential prognostic biomarkers by determining the gene expression pattern in the blood of heart failure patients, using whole transcriptome and targeted TaqMan^® low-density array analyses. Results: We performed a stepwise cross-sectional longitudinal study in a cohort of chronic heart failure patients with and without systemic iron deficiency. First, the full transcriptome was performed in a nested case-control exploratory cohort of 7 paired patients and underscored 1128 differentially expressed transcripts according to iron status (cohort1#). Later, we analyzed the messenger RNA levels of 22 genes selected by their statistical significance and pathophysiological relevance, in a validation cohort of 71 patients (cohort 2#). Patients with systemic iron deficiency presented lower mRNA levels of mitochondrial ferritin, sirtuin-7, small integral membrane protein 20, adrenomedullin and endothelin converting enzyme-1. An intermediate mitochondrial ferritin gene expression and an intermediate or low sirtuin7 and small integral membrane protein 20 mRNA levels were associated with an increased risk of all-cause mortality and heart failure admission ((HR 2.40, 95% CI 1.04–5.50, p-value = 0.039), (HR 5.49, 95% CI 1.78–16.92, p-value = 0.003), (HR 9.51, 95% CI 2.69–33.53, p-value < 0.001), respectively). Conclusions: Patients with chronic heart failure present different patterns of blood gene expression depending on systemic iron status that affect pivotal genes involved in iron regulation, mitochondrial metabolism, endothelial function and cardiovascular physiology, and correlate with adverse clinical outcomes.

Impact of change in iron status over time on clinical outcomes in heart failure according to ejection fraction phenotype

Aims

The importance of iron deficiency (ID) in heart failure with preserved ejection fraction (HFpEF) is unknown. In HF with reduced ejection fraction (HFrEF), ID is reported as an independent predictor of mortality in HF although not all published studies agree. Different definitions of ID have been assessed, and the natural history of untreated ID not established, which may explain the conflicting results. This study aimed to assess the relationship between ID and mortality in HFpEF, clarify which definition of ID correlates best with outcomes in HFrEF, and determine the prognostic importance of change in ID status over time.

Methods and results

Analyses were conducted on data from 1563 patients participating in a prospective international cohort study comparing HFpEF with HFrEF. Plasma samples from baseline and 6 month visits were analysed for the presence of ID. Two ID definitions were evaluated: ID_Ferritin = ‘ferritin < 100 mcg/L or ferritin 100–300 mcg/L + transferrin saturation < 20%’ and ID_Tsat = ‘transferrin saturation < 20%’. The risk of all‐cause mortality and death/HF hospitalization associated with baseline ID (ID_Ferritin or ID_Tsat) and change in ID status at 6 months (persistent, resolving, developing, or never present) was estimated in multivariable Cox proportional hazards models. Of 1563 patients, 1115 (71%) had HFrEF and 448 (29%) HFpEF. Prevalence of ID was similar in HFpEF and HFrEF (58%). Patients with ID were more likely to be female, diabetic, and have a higher co‐morbid burden than patients without ID. ID by either definition did not confer independent risk for either all‐cause mortality or death/HF hospitalization for patients with HFpEF [ID_Ferritin hazard ratio (HR) 0.65 (95% confidence interval 0.40–1.05), P = 0.08; ID_Tsat HR 1.16 (0.72–1.87), P = 0.55]. In the overall study cohort (HFrEF + HFpEF) and HFrEF subgroup, ID_Ferritin was inferior to ID_Tsat in prediction of all‐cause mortality [overall cohort: HR 1.21 (0.95–1.53), P = 0.12 vs. HR 1.95 (1.52–2.51), P < 0.01; HFrEF: HR 1.12 (0.85–1.48), P = 0.43 vs. HR 1.57 (1.15–2.14), P < 0.01]. Persistence of ID_Tsat at 6 months was strongly associated with poor outcomes compared with never having ID_Tsat [HR 2.22 (1.42–3.46), P < 0.01] or having ID_Tsat at baseline self‐resolve by 6 months [HR 1.40 (1.06–1.86), P = 0.02].

Conclusions

Iron deficiency is equally prevalent in HFpEF and HFrEF but is negatively prognostic only in HFrEF. The natural history of ID is important; persistent ID is strongly associated with mortality whereas resolution is not. ID_Tsat is the superior definition of ID and should inform future trials investigating the efficacy of intravenous iron replacement in patients with HFrEF.

Iron Deficiency: A New Target for Patients With Heart Failure

Iron deficiency (ID) is one of the most frequent comorbidities in patients with heart failure (HF). ID is estimated to be present in up to 50% of outpatients and is a strong independent predictor of HF outcomes. ID has been shown to reduce quality of life, exercise capacity and survival, in both the presence and absence of anemia. The most recent 2016 guidelines recommend starting replacement treatment at ferritin cutoff value <100 mcg/l or between 100 and 299 mcg/l when the transferrin saturation is <20%. Beyond its effect on hemoglobin, iron plays an important role in oxygen transport and in the metabolism of cardiac and skeletal muscles. Mitochondria are the most important sites of iron utilization and energy production. These factors clearly have roles in the diminished exercise capacity in HF. Oral iron administration is usually the first route used for iron repletion in patients. However, the data from the IRONOUT HF study do not support the use of oral iron supplementation in patients with HF and a reduced ejection fraction, because this treatment does not affect peak VO₂ (the primary endpoint of the study) or increase serum ferritin levels. The FAIR-HF and CONFIRM-HF studies have shown improvements in symptoms, quality of life and functional capacity in patients with stable, symptomatic, iron-deficient HF after the administration of intravenous iron (i.e., FCM). Moreover, they have shown a decreased risk of first hospitalization for worsening of HF, as later confirmed in a subsequent meta-analysis. In addition, the EFFECT-HF study has shown an improvement in peak oxygen consumption at CPET (a parameter generally considered the gold standard of exercise capacity and a predictor of outcome in HF) in patients randomized to receive ferric carboxymaltose. Finally, the AFFIRM AHF trial evaluating the effects of FCM administration on the outcomes of patients hospitalized for acute HF has found significantly fewer hospital readmissions due to HF among patients treated with FCM rather than placebo.

Neurohormonal activation induces intracellular iron deficiency and mitochondrial dysfunction in cardiac cells

Background

Iron deficiency (ID) is common in patients with heart failure (HF) and is associated with poor outcomes, yet its role in the pathophysiology of HF is not well-defined. We sought to determine the consequences of HF neurohormonal activation in iron homeostasis and mitochondrial function in cardiac cells.

Methods

HF was induced in C57BL/6 mice by using isoproterenol osmotic pumps and embryonic rat heart-derived H9c2 cells were subsequently challenged with Angiotensin II and/or Norepinephrine. The expression of several genes and proteins related to intracellular iron metabolism were assessed by Real time-PCR and immunoblotting, respectively. The intracellular iron levels were also determined. Mitochondrial function was analyzed by studying the mitochondrial membrane potential, the accumulation of radical oxygen species (ROS) and the adenosine triphosphate (ATP) production.

Results

Hearts from isoproterenol-stimulated mice showed a decreased in both mRNA and protein levels of iron regulatory proteins, transferrin receptor 1, ferroportin 1 and hepcidin compared to control mice. Furthermore, mitoferrin 2 and mitochondrial ferritin were also downregulated in the hearts from HF mice. Similar data regarding these key iron regulatory molecules were found in the H9c2 cells challenged with neurohormonal stimuli. Accordingly, a depletion of intracellular iron levels was found in the stimulated cells compared to non-stimulated cells, as well as in the hearts from the isoproterenol-induced HF mice. Finally, neurohormonal activation impaired mitochondrial function as indicated by the accumulation of ROS, the impaired mitochondrial membrane potential and the decrease in the ATP levels in the cardiac cells.

Conclusions

HF characteristic neurohormonal activation induced changes in the regulation of key molecules involved in iron homeostasis, reduced intracellular iron levels and impaired mitochondrial function. The current results suggest that iron could be involved in the pathophysiology of HF.

Biomedical, Socioeconomic and Demographic Predictors of Heart Failure Readmissions: A Systematic Review

AIMS

To identify the biomedical, socioeconomic and demographic predictors of heart failure (HF) related readmissions in adult patients with HF.

METHODS

This systematic review was conducted in March 2020 using the databases EMBASE, CINAHL and Medline to identify publications between 2015-2020. The resulting articles were systematically reviewed according to the PRISMA guidelines.

RESULTS

Eighteen (18) studies were included in this review. Unemployment (HR=1.09; 95%CI=1.05-1.14; p=0.03) was the only socioeconomic factor predictive of HF-readmissions. Socio-Economic Indexes for Areas (SEIFA) scores did not predict HF readmissions in adults with HF (p>0.05). All patients included in the studies had pre-existing HF. Based on the included studies, Indigenous status was identified as a risk factor for HF readmissions in 1 study (p<0.05), and age or sex did not affect HF readmission patterns (p>0.05). New York Heart Association (NYHA) class, brain natriuretic peptide (BNP) levels, and heart rate were also predictive of HF readmission (p<0.05). Left ventricular ejection fraction and blood pressure, however, were non-significant risk factors of HF readmissions (p>0.05).

CONCLUSIONS

This review identified unemployment, Indigenous status, NYHA class, heart rate, and BNP levels to predict HF related readmissions in adult patients with HF. Adding demographic and socioeconomic variables to readmission risk models has the potential to more accurately target patients at risk of readmissions.

Use of intravenous iron in patients with iron deficiency and chronic heart failure: Real-world evidence

INTRODUCTION AND OBJECTIVES

Treatment with intravenous iron in patients with heart failure (HF) and iron deficiency (ID) improves symptoms, however its impact on survival and safety is unknown. We aimed to evaluate the management of ID and anemia with intravenous iron in patients with HF and long-term safety of intravenous iron.

METHODS

We evaluated anemia and ID in patients with chronic HF at 3 university hospitals. Anemia was defined using the World Health Organization definition and ID was defined as ferritin <100 ug/L or a Transferrin Saturation <20% if ferritin between 100 and 299 ug/L. We assessed treatment with intravenous iron during follow-up and its association with mortality and HF hospitalizations using multivariate cox regression analysis.

RESULTS

We included 2,114 patients, median age 72 years and 57% had reduced left ventricular ejection fraction. ID was present in 55% and ID and anemia in 29%. Treatment with intravenous iron was used in 24% of patients with ID and 34% of patients with ID and anemia. In patients with ID, after multivariate adjustment, treatment with intravenous iron was associated with lower all-cause mortality: HR = 0.38 (0.28-0.56), lower cardiovascular mortality: HR = 0.34 (0.20-0.57) and no differences in HF hospitalizations: HR = 1.15 (0.88-1.50). Similar outcomes were found for patients with anemia and ID.

CONCLUSIONS

In a real-world cohort of patients with HF, treatment with intravenous iron was used in one third of patients with ID and anemia and appears safe in mid-term follow-up.

Why is Iron Deficiency Recognised as an Important Comorbidity in Heart Failure?

There is an increasing awareness of the prevalence of iron deficiency in patients with heart failure (HF), and its contributory role in the morbidity and mortality of HF. Iron is a trace element necessary for cells due to its capacity to transport oxygen and electrons. The prevalence of iron deficiency increases with the severity of HF. For a long time the influence of iron deficiency was underestimated, especially in terms of worsening of cardiovascular diseases and developing anaemia. In recent years, studies with intravenous iron agents in patients with iron deficiency and HF showed new insights into the improvement of iron therapy. Additionally, experimental studies supporting the understanding of iron metabolism and the resulting pathophysiological pathways of iron have been carried out. The aim of this mini review is to highlight why iron deficiency is recognised as an important comorbidity in HF.

Iron deficiency is associated with higher mortality in patients undergoing cardiac surgery: a prospective study

BACKGROUND

Iron deficiency is frequent in patients undergoing cardiac surgery. The relevance of iron deficiency, however, is ill defined. Therefore, our study aimed to investigate the impact of iron deficiency (ferritin <100 μg L^-1) with or without concomitant anaemia on clinical outcome after cardiac surgery.

METHODS

In this prospective observational study, 730 patients undergoing elective cardiac surgery were assigned into four groups according to their iron status and anaemia. Mortality, serious adverse events (SAEs), major cardiac and cerebrovascular events (MACCEs), allogenic blood transfusion requirements, and length of hospital stay were assessed during a 90-day follow-up period. The effect of iron deficiency on these outcomes was first calculated in models adjusting for anaemia only, followed by two multivariate models adjusting for anaemia and either the EuroSCORE II or any possible confounders.

RESULTS

The presence of iron deficiency (ferritin <100 μg L^-1) was associated with an increase in 90-day mortality from 2% to 5% in patients without anaemia, and from 4% to 14% in patients with anaemia. Logistic regression resulted in an odds ratio of 3.5 (95% confidence interval: 1.5-8.4); P=0.004. The effect persisted in both multivariate models. Moreover, iron deficiency was associated with an increased incidence of SAEs, MACCEs, transfusion, and prolonged hospital stay.

CONCLUSIONS

Preoperative iron deficiency (ferritin <100 μg L^-1) was independently associated with increased mortality, more SAEs, and prolonged hospital stay after cardiac surgery. These findings underline the importance of preoperative iron deficiency screening in the context of a comprehensive patient blood management programme, and highlight its importance as a research topic in cardiac surgery.

CLINICAL TRIAL REGISTRATION

NCT02031289.