Patterns and determinants of functional and absolute iron deficiency in patients undergoing cardiac rehabilitation following heart surgery

Anaemia and iron deficiency are frequent following major surgery. The present study aims to identify the iron deficiency patterns in cardiac surgery patients at their admission to a cardiac rehabilitation programme, and to determine which perioperative risk factor(s) may be associated with functional and absolute iron deficiency.

This was a retrospective study on prospectively collected data.

The patient population included 339 patients. Functional iron deficiency was defined in the presence of transferrin saturation <20% and serum ferritin ≥100 µg/l. Absolute iron deficiency was defined in the presence of serum ferritin values <100 µg/l.

Functional iron deficiency was found in 62.9% of patients and absolute iron deficiency in 10% of the patients. At a multivariable analysis, absolute iron deficiency was significantly (p = 0.001) associated with mechanical prosthesis mitral valve replacement (odds ratio 5.4, 95% confidence interval 1.9–15) and tissue valve aortic valve replacement (odds ratio 4.5, 95% confidence interval 1.9–11). In mitral valve surgery, mitral repair carried a significant (p = 0.013) lower risk of absolute iron deficiency (4.4%) than mitral valve replacement with tissue valves (8.3%) or mechanical prostheses (22.5%). Postoperative outcome did not differ between patients with functional iron deficiency and patients without iron deficiency; patients with absolute iron deficiency had a significantly (p = 0.017) longer postoperative hospital stay (median 11 days) than patients without iron deficiency (median nine days) or with functional iron deficiency (median eight days).

Absolute iron deficiency following cardiac surgery is more frequent in heart valve surgery and is associated with a prolonged hospital stay. Routine screening for iron deficiency at admission in the cardiac rehabilitation unit is suggested.