title: Iron deficiency predicts impaired exercise capacity in patients with systolic chronic heart failure.
abstract: BACKGROUND
  Iron is an indispensable element of hemoglobin, myoglobin, and cytochromes, and, beyond erythropoiesis, is involved in oxidative metabolism and cellular energetics. Hence, iron deficiency (ID) is anticipated to limit exercise capacity. We investigated whether ID predicted exercise intolerance in patients with systolic chronic heart failure (CHF).
  
  
  RESULTS
  We prospectively studied 443 patients with stable systolic CHF (age 54 ± 10 years, males 90%, ejection fraction 26 ± 7%, New York Heart Association Class I/II/III/IV 49/188/180/26). ID was defined as: serum ferritin <100 μg/L or serum ferritin 100-300 μg/L with serum transferrin saturation <20%. Exercise capacity was expressed as peak oxygen consumption (VO(2)) and ventilatory response to exercise (VE-VCO(2) slope). ID was present in 35 ± 4% (±95% confidence interval) of patients with systolic CHF. Those with ID had reduced peak VO(2) and increased VE-VCO(2) slope as compared to subjects without ID (peak VO(2): 13.3 ± 4.0 versus 15.3 ± 4.5 mL•min•kg, VE-VCO(2) slope: 50.9 ± 15.8 versus 43.1 ± 11.1, respectively, both P < .001, P < .05). In multivariable models, the presence of ID was associated with reduced peak VO(2) (β = -0.14, P < .01 P < .05) and higher VE-VCO(2) slope (β = 0.14, P < .01 P < .05), adjusted for demographics and clinical variables. Analogous associations were found between serum ferritin, and both peak VO(2) and VE-VCO(2) slope (P < .05).
  
  
  CONCLUSIONS
  ID independently predicts exercise intolerance in patients with systolic CHF, but the strength of these associations is relatively weak. Whether iron supplementation would improve exercise capacity in iron-deficient subjects requires further studies.
authors: Department of Heart Diseases, Wroclaw Medical University, Wroclaw, Poland. ewa.jankowska@antro.pan.wroc.pl
authors: Ewa A
authors: EA
authors: Jankowska
authors: Piotr
authors: P
authors: Rozentryt
authors: Agnieszka
authors: A
authors: Witkowska
authors: Jolanta
authors: J
authors: Nowak
authors: Oliver
authors: O
authors: Hartmann
authors: Beata
authors: B
authors: Ponikowska
authors: Ludmila
authors: L
authors: Borodulin-Nadzieja
authors: Stephan
authors: S
authors: von Haehling
authors: Wolfram
authors: W
authors: Doehner
authors: Waldemar
authors: W
authors: Banasiak
authors: Lech
authors: L
authors: Polonski
authors: Gerasimos
authors: G
authors: Filippatos
authors: Stefan D
authors: SD
authors: Anker
authors: Piotr
authors: P
authors: Ponikowski
mesh_terms: D016001:Confidence Intervals; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005293:Ferritins / Q000097:blood*; D006305:Health Status Indicators; D054143:Heart Failure, Systolic / Q000097:blood* / Q000503:physiopathology; D006801:Humans; D000090463:Iron Deficiencies; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010101:Oxygen Consumption; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors; D013318:Stroke Volume; D016277:Ventricular Function, Left
chemical_list: D005293:Ferritins