Abstract Background Iron deficiency (ID) is a common comorbidity in cardiovascular disease, associated with reduced exercise capacity and adverse clinical outcomes. Purpose To assess the prevalence of ID and its association with peak oxygen uptake (VO₂ max) in patients undergoing outpatient cardiac rehabilitation (CR) following myocardial infarction (MI). Methods A prospective cohort of patients referred for CR (12-week CR program, 3 times per week) in two centres between 2019 and 2022 was analysed. Cardiopulmonary exercise testing (CPET) was conducted at baseline and after program completion. ID was defined as ferritin 100 mcg/L or ferritin 100–300 mcg/L with transferrin saturation (TSAT) 20%. Multivariate regression models were used to evaluate the impact of ID parameters on VO₂ max before and after CR, adjusting for age and sex. Results Among 316 patients (61 (+/-11), 24% female), ID was present in 87(27%), primarily with low ferritin (66, 22%). TSAT 20% was present in 60 (19%) patients, mostly in combination with low ferritin - Figure. Ferritin levels correlated modestly with baseline VO₂max (r = 0.176, p = 0.02) and after CR (r = 0.114, p = 0.045), while TSAT showed a stronger correlation at both time points (r = 0.327, p 0.001; r = 0.212, p 0.001). The median improvement in VO2max for the No ID group was 2.37 (IQR = 5.05), while for the ID group, it was 2.10 (IQR = 4.58). The results revealed no statistically significant difference between the groups regarding ID (U = 8559.000, p = 0.974) - Figure. In multivariate analysis only TSAT (β =0.05, p = 0.010), but not ferritin (β =0.01 77, p = 0.4) predicted poor exercise capacity at baseline. However, this effect was not observed at the end of CR, neither ID parameter predict impaired poor improvement in VO2max following CR. Conclusion Iron deficiency is common in post-MI patients enrolled in CR, primarily due to low ferritin. Low TSAT was better predictor of baseline exercise capacity. Patient improvement in exercise capacity during CR was not dependent on ID, ferritin or TSAT.
Zavrtanik et al. (Sat,) studied this question.