Prognostic implications of iron deficiency and supplementation in patients undergoing valvular heart surgery

Abstract

Abstract Background Iron deficiency is common in patients with cardiovascular diseases, present in up to 60% of patients with coronary artery disease, heart failure, or pulmonary hypertension. Its role in valvular heart disease, including its prevalence, determinants, and prognostic implications, remains unclear. Purpose The present study aimed to evaluate the prognostic significance of iron deficiency in patients undergoing valvular heart surgery. Methods Pre-operative haematology and iron profiles were retrospectively collected in all patients undergoing valvular heart surgery in Hong Kong between 2010 and 2021. Iron deficiency was defined referencing the ESC 2021 guidelines as a ferritin level <100 ng/mL or a transferrin saturation <20% with a ferritin level of 100 to 299 ng/mL. Logistic regression analyses were conducted to determine variables associated with guideline-defined iron deficiency. Stepwise Cox proportional hazards regression was applied to identify predictors of 5-year mortality. The impact of iron supplementation on outcomes was estimated in iron-deficient patients, modelled by inverse probability of treatment-weighted logistic regression. Results Our study included 578 patients; the median age was 62 (interquartile range 54-70) years, and 47.4% were males. Iron deficiency was present in 324 (56.1%) patients. Independent correlates of iron deficiency were age, male sex, diabetes mellitus, atrial fibrillation, heart failure, diuretics and warfarin use, aortic stenosis, and tricuspid regurgitation (Table 1). Death from any cause occurred in 99 patients over five years of follow-up, of which 45 were due to cardiovascular events. Iron deficiency was associated with a two- to three-fold excess risk of all-cause (hazard ratio [HR] 1.89, 95% CI 1.23-2.90; P = 0.004) and cardiovascular mortality (HR 2.84, 95% CI 1.23-2.90; P = 0.004). Results were consistent in multivariable models incorporating comorbidities, medications, type of valvular intervention, and cardiac surgery risk-scoring systems, even after adjustment for haemoglobin levels (Table 2). For individual components of the guideline criteria, transferrin saturation <20% and ferritin <300 ng/mL were associated with worse all-cause and cardiovascular mortality. Among 324 patients with iron deficiency, 61 (18.8%) received iron supplementation before valvular surgery. Iron supplementation was associated with a 58% lower risk of death in multivariable models with IPTW (HR 0.42; 95% CI, 0.19–0.99; P = 0.047). Conclusions In patients undergoing valvular surgery, iron deficiency is associated with worse survival. This elevated risk may be mitigated by iron supplementation before valvular surgery.Table 1Table 2