Iron deficiency in heart failure: Impact on response to cardiac resynchronization therapy

The effect of iron deficiency on cardiac resynchronization therapy: results from the RIDE-CRT Study

Aims

Cardiac resynchronization therapy (CRT) improves functional status, induces reverse left ventricular remodelling, and reduces hospitalization and mortality in patients with symptomatic heart failure, left ventricular systolic dysfunction, and QRS prolongation. However, the impact of iron deficiency on CRT response remains largely unclear. The purpose of the study was to assess the effect of functional and absolute iron deficiency on reverse cardiac remodelling, clinical response, and outcome after CRT implantation.

Methods and results

The relation of iron deficiency and cardiac resynchronization therapy response (RIDE‐CRT) study is a prospective observational study. We enrolled 77 consecutive CRT recipients (mean age 71.3 ± 10.2 years) with short‐term follow‐up of 3.3 ± 1.9 months and long‐term follow‐up of 13.0 ± 3.2 months. Primary endpoints were reverse cardiac remodelling on echocardiography and clinical CRT response, assessed by change in New York Heart Association classification. Echocardiographic CRT response was defined as relative improvement of left ventricular ejection fraction ≥ 20% or left ventricular global longitudinal strain ≥ 20%. Secondary endpoints were hospitalization for heart failure and all‐cause mortality (mean follow‐up of 29.0 ± 8.4 months). At multivariate analysis, iron deficiency was identified as independent predictor of echocardiographic (hazard ratio 4.97; 95% confidence interval 1.15–21.51; P = 0.03) and clinical non‐response to CRT (hazard ratio 4.79; 95% confidence interval 1.30–17.72, P = 0.02). We found a significant linear‐by‐linear association between CRT response and type of iron deficiency (P = 0.004 for left ventricular ejection fraction improvement, P = 0.02 for left ventricular global longitudinal strain improvement, and P = 0.003 for New York Heart Association response). Iron deficiency was also significantly associated with an increase in all‐cause mortality (P = 0.045) but not with heart failure hospitalization.

Conclusions

Iron deficiency is a negative predictor of effective CRT therapy as assessed by reverse cardiac remodelling and clinical response. Assessment of iron substitution might be a relevant treatment target to increase CRT response and outcome in chronic heart failure patients.

Association Between Norepinephrine Levels and Abnormal Iron Status in Patients With Chronic Heart Failure: Is Iron Deficiency More Than a Comorbidity?

Background

Mechanisms underlying iron homeostasis dysregulation in patients with chronic heart failure remain unsettled. In cardiomyocyte models, norepinephrine may lead to intracellular iron depletion, but the potential association between catecholamines (sympathetic activation markers) and iron metabolism biomarkers in chronic heart failure is unknown.

Methods and Results

In this cross‐sectional analysis, we studied the association between plasma norepinephrine levels and serum iron status biomarkers indicating iron storage (ferritin), iron transport (transferrin saturation), and iron demand (soluble transferrin receptor) in a prospective cohort of 742 chronic heart failure patients (mean age, 72±11 years; 56% male). Impaired iron status was defined as ferritin <100 μg/L or transferrin saturation <20%. Impaired iron status was observed in 69% of patients. In multivariate models, greater norepinephrine levels were associated with impaired iron transport (transferrin saturation <20%, odds ratio=2.28; 95% CI [1.19–4.35]; P=0.013), but not with impaired iron storage (ferritin <100 μg/L, odds ratio=1.25; 95% CI [0.73–2.16]; P=0.415). Norepinephrine was a significant predictor of increased iron demand (soluble transferrin receptor, standardized β‐coefficient=0.12; P=0.006) and low transferrin saturation (standardized β‐coefficient=−0.12; P=0.003). However, norepinephrine levels were not associated with iron or ferritin levels (P>0.05). Adjusted norepinephrine marginal means were significantly higher in patients with impaired iron status compared with those with normal iron status (528 pg/mL [505–551] versus 482 pg/mL [448–518], respectively; P=0.038).

Conclusions

In chronic heart failure patients, increased sympathetic activation estimated with norepinephrine levels is associated with impaired iron status and, particularly, dysregulation of biomarkers suggesting impaired iron transport and increased iron demand. Whether the relationship between norepinephrine and iron metabolism is bidirectional and entails causality need to be elucidated in future research.

Iron deficiency in chronic and acute heart failure: A contemporary review on intertwined conditions

Iron Deficiency (ID) is increasingly recognized as a prevalent comorbid condition in Heart Failure (HF). Despite this, the pathophysiological mechanisms for progressive ID in either chronic or acute HF are still poorly understood. Beyond the traditional factors for iron deficit in the general population, we ought to review the specificities of such paucity in the HF patient, particularly focusing on the interplay between heightened inflammation, overactivity of the sympathetic nervous system and the so-called cardio-renal-anaemia-ID syndrome. Currently, ID constitutes not only an independent prognostic marker but also a novel safe therapeutic target. Particularly, in selected stable HF patients with reduced left ventricular ejection fraction, intravenous (IV) iron improves symptomatic burden and reduces hospitalizations due to worsening HF. On this topic, the main trials of IV iron with either iron sucrose (Toblli et al., FERRIC-HF and IRON-HF) or ferric carboxymaltose (FAIR-HF, CONFIRM-HF and EFFECT-HF) will be summarized and discussed. Finally, we debate the gaps in knowledge of ID in special populations, namely the unreliability of routine plasmatic surrogate markers to assess iron status in acute and advanced HF, the challenging patient with both HF and Chronic Kidney Disease, as well as efficacy and safety concerns in these settings and the potential role of iron correction in cardiac resynchronization therapy candidates.

Iron Therapy in Heart Failure: Ready for Primetime?

There is an increasing awareness of the prevalence of iron deficiency (ID) in patients with heart failure (HF) and its contributory role in the morbidity and mortality of HF. It is important to note that many HF patients have ID without being anaemic, hence it is vital to screen for ID even in patients with haemoglobin within the normal laboratory range. This review summarises the pathophysiology and epidemiology of ID in HF before discussing the evidence for iron replacement therapy in HF patients. Finally, it discusses the ongoing large outcome trials evaluating iron replacement in HF.