Abstract 18230: Iron Deficiency Impairs Exercise Capacity in Patients With Systolic Chronic Heart Failure, Beyond its Negative Effects on Erythropoiesis
Background: Iron is an indispensable element of hemoglobin, myoglobin and cytochromes. Beyond erythropoiesis, it is involved in oxidative metabolism and cellular energetics. Hence, iron deficiency (ID) is anticipated to impair exercise capacity. We studied links between ID and exercise intolerance in patients with chronic heart failure (CHF).
Methods: We examined 443 patients with systolic CHF (age: 54±10 years, males: 90%, LVEF: 26±7%, NYHA class I/II/III/IV: 49/188/180/26). Several biomarkers were assessed in serum for description of iron status: iron, ferritin, total iron biding capacity, transferrin saturation (Tsat), soluble transferrin receptor (sTfR). Serum sTfR increases proportionally to the magnitude of ID detected in target tissues, e.g. erythropoietic cells. ID was defined as: ferritin <100 ug/L, or ferritin 100–300 ug/L and Tsat <20%. Body iron amount (mg/kg) was estimated with a Skikne equation using serum sTfR and ferritin. Anemia was defined: hemoglobin<12 g/dL in women and<13 g/dL in men.
Results: ID was present in 155 (35%) of all patients (in 46 [56%] and 109 [30%] of anemics and non-anemics). ID was related to impaired exercise capacity in both anemic (peak oxygen consumption [VO2]: 12.7±4.1 vs 14.6±4.4 mL/min/kg; ventilatory response to exercise VE-VCO2 slope: 54.5±16.4 vs 45.1±12.4 – both p<0.05) and non-anemic subjects (peak VO2: 13.5±3.9 vs 15.5±4.5 mL/min/kg; VE-VCO2 slope: 49.3±15.3 vs 42.9±10.9 – both p<0.001). In multivariable models, ID (p<0.01) was associated with reduced peak VO2 and high VE-VCO2 slope, after an adjustment for demographics, NYHA class, LVEF, NT-proBNP, CHF etiology, hsCRP, co-morbidities (renal dysfunction, diabetes, anemia). Among biomarkers of iron metabolism, the strongest correlation was found between sTfR and peak VO2 (r=-0.22, p<0.001). There was a positive correlation between body iron amount and peak VO2, and its strength grew in subsequent hemoglobin quartiles: below or equal 13.1, 13.2–14.1, 14.2–15.1, equal or above 15.2 g/dL — r=0.18 (p=0.07), r=0.20 (p<0.05), r=0.24 (p=0.01), r=0.33 (p=0.001).
Conclusions: ID relates to exercise intolerance in patients with CHF. Whether iron supplementation would improve exercise capacity in iron deficient subjects, requires further studies.
- © 2010 by American Heart Association, Inc.