Impact of Iron Deficiency in Adults With Fontan Circulation

Background Iron deficiency (ID) is common in patients with heart failure and associated with worse outcomes, regardless of the presence of anemia. However, the prevalence and clinical implications of ID in adults after the Fontan operation has not been elucidated. Methods This was a retrospective cohort of adults after the Fontan operation who underwent laboratory tests and cardiopulmonary exercise testing (CPET). ID was defined as ferritin <100 μg/L or ferritin 100-300 μg/L and a transferrin saturation (TSAT) <20%. The prevalence of ID and its relationships with CPET findings and the composite outcome of all-cause death, hospitalization for heart failure, or ventricular arrhythmia were evaluated. Results Of the 105 adults who underwent the Fontan operation, 94 were enrolled (mean age 25±11 years, females 46.8%). ID was found in 73.4% of patients (n=69 of 94): absolute ID 59 patients, functional ID 10 patients. The percentages of predicted anaerobic threshold, maximum oxygen uptake (peak VO 2 ), and the slope of the increase in the VO 2 to the increase in the work rate were lower in the ID group than in the non-ID group after adjusting for confounders, whereas ventilation versus carbon dioxide production was not significantly different between the two groups. During median follow-up of 3.3 years, the composite outcome was observed in 11 patients in the ID group (15.9%) and no patients in the non-ID group (log-rank test, p=0.048). Conclusions ID was highly prevalent in adults with Fontan circulation and was significantly associated with worse exercise capacity and prognosis.