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

Background: Congenital heart disease (CHD) affects approximately 9 per 1,000 live births worldwide, with increasing prevalence due to improved survival. Today, over 90% of individuals with CHD reach adulthood, resulting in a growing population of adults with congenital heart disease (ACHD). Despite its clinical relevance, iron deficiency (ID) and anemia have been insufficiently studied in this group. Objectives: To evaluate the prevalence and clinical impact of iron deficiency and anemia in ACHD, particularly their relationship with exercise capacity. Methods: We retrospectively analyzed 310 ACHD patients at University Hospital Düsseldorf between January 2017 and January 2019. Iron status was assessed using serum ferritin, transferrin saturation (TSAT), and hemoglobin levels. Exercise capacity was measured by cardiopulmonary exercise testing (VO₂ max). Prevalence and clinical as-sociations were compared with those reported in heart failure populations, using ESC guideline criteria. Analyses were adjusted for age, sex, and defect complexity. Results: ID was present in 59.0% (183/310). Anemia was observed in 4.2% (13/310), mostly microcytic (46%) or normocytic (38%). Reduced exercise capacity (VO₂ max < 80% pre-dicted) occurred in 16.5% (51/310), more frequently in complex CHD (31.3% vs. 11.3%, p < 0.001). ID was associated with a trend towards lower VO₂ max (21.3 vs. 23.5 mL/min/kg, p = 0.068), while anemia correlated with significantly reduced performance (19.8 ± 4.1 vs. 22.9 ± 6.3 mL/min/kg, p = 0.041). Conclusion: Iron deficiency and anemia are frequent in ACHD and may impair func-tional capacity. These findings highlight the need for targeted screening and manage-ment strategies in this growing patient population.