Iron Status, Anemia, and Functional Capacity in Adults with Congenital Heart Disease

Raphael Phinicarides (Düsseldorf)1, I. E. Reuter (Düsseldorf)1, G. Wolff (Düsseldorf)1, K. Klein (Düsseldorf)1, H. Heidari (Düsseldorf)1, T. Zeus (Düsseldorf)1

1Universitätsklinikum Düsseldorf Klinik für Kardiologie, Pneumologie und Angiologie Düsseldorf, Deutschland


This study explores the prevalence of iron deficiency (ID) and anemia in adults with congenital heart disease (ACHD) and investigates their impact on exercise capacity. The goal is to evaluate the relevance of recognizing and managing ID and anemia in ACHD patients, providing valuable insights for healthcare professionals and researchers in the field.
A retrospective analysis utilized data from the ACHD outpatient clinic at the University Hospital Düsseldorf. Anemia was defined based on specific criteria involving hemoglobin (Hb) levels, hematocrit levels, and red blood cell count. ACHD patients were categorized into four subgroups. Cardiac functionality was assessed through echocardiography and magnetic resonance imaging (MRI), documenting parameters like ejection fraction (EF), wall thickness, cardiac dimensions, heart valve functionality, and New York Heart Association (NYHA) stage. Physical endurance was evaluated through spiroergometry, ergometry, and the six-minute walk test. Statistical analysis involved various tests for group comparisons and variable correlations, with a significance level set at 5% alpha.
Between January 2017 and January 2019, data from 310 ACHD patients at the University Hospital Düsseldorf were analyzed. The cohort comprised 51.6% men and 48.4% women, with an average age of 33 years and BMI of 25.1 kg/m². Patients were distributed among shunt lesions (74), left-sided anomalies (78), right-sided anomalies (84), and complex anomalies (74), with balanced gender distribution in each group. Most had primarily acyanotic congenital heart defects (65.2%). Women exhibited lower ferritin and transferrin saturation levels. Anemia prevalence in the cohort was 4.2%, mainly microcytic or normocytic. Exercise capacity limitations were observed in 16.5%, with complex heart defects associated with higher limitations (NYHA class > I). Eight anemic patients met iron deficiency criteria, suggesting an association between anemia and iron deficiency.
The study concluded that while no higher prevalence of iron deficiency or anemia was found in ACHD patients compared to the general population, the prevalence of iron deficiency varied based on the definition used. Lower hemoglobin levels were linked to poorer exercise capacity, especially when patients with Eisenmenger syndrome were excluded.  No correlation could be identified with endurance, neither for the max VO2 in the spiroergometry, nor for METs in the ergometry. However, when graphically presenting the results of spiroergometry for anemic and non-anemic patients (Fig. 2&3), it becomes apparent that patients with anemia on average achieve poorer results.
The study showed that ACHD exhibit similar rates of ID and anemia compared to the general population. 
When patients with Eisenmenger syndrome were excluded, a significant association between anemia and reduced exercise capacity was identified. 
To better define iron deficiency in ACHD patients and investigate the potential benefits of iron supplementation on exercise capacity, further research, including large-scale prospective trials, is necessary. 

Fig. 1: Distribution of Cardiac Anomaly Groups

Fig. 2: Variation in max. Oxygen Uptake per Unit of Body Weight as Influenced by Hb Levels

Fig. 3: Distribution of METs Based on HbLevels
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