title: Heart rate recovery is impaired after maximal exercise testing in children with sickle cell anemia.
abstract: OBJECTIVE
  To examine heart rate recovery (HRR) as an indicator of autonomic nervous system dysfunction after maximal exercise testing in children and young adults with sickle cell anemia (SCA).
  
  
  METHODS
  Recovery phase heart rate (HR) in the first 5 minutes after maximal exercise testing in 60 subjects with SCA and 30 matched controls without SCA was assessed. The difference between peak HR and HR at both 1-minute (ΔHR1min) and 2-minutes recovery was our primary outcome.
  
  
  RESULTS
  Compared with controls, subjects with SCA demonstrated significantly smaller mean ΔHR1min (23 beats per minute [bpm], 95% CI 20-26 vs 32 bpm, 95% CI 26-37, P = .006) and the difference between maximal HR and HR at 2 minutes (39 bpm, 95% CI 36-43 vs 48 bpm, 95% CI 42-53, P = .011). Subjects with SCA also showed smaller mean changes in HR from peak HR to 1 minute, from 1 minute to 2 minutes, and from 2 through 5 minutes of recovery by repeated-measures testing. In a multivariable regression model, older age was independently associated with smaller ΔHR1min in subjects with SCA. Cardiopulmonary fitness and hydroxyurea use, however, were not independent predictors of ΔHR1min.
  
  
  CONCLUSIONS
  Children with SCA demonstrate impaired HRR after maximal exercise. Reduced postexercise HRR in SCA suggests impaired parasympathetic function, which may become progressively worse with age, in this population.
authors.affiliation: Hematology, Oncology, & Stem Cell Transplant, Ann & Robert H. Lurie Children's Hospital of Chicago, Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL.
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Alvarado
authors.affiliation: Cardiology, Ann & Robert H. Lurie Children's Hospital of Chicago, Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL.
authors.forename: Kendra M
authors.initials: KM
authors.lastname: Ward
authors.affiliation: Hematology, Oncology, & Stem Cell Transplant, Ann & Robert H. Lurie Children's Hospital of Chicago, Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL.
authors.forename: Devin S
authors.initials: DS
authors.lastname: Muntz
authors.affiliation: Hematology, Oncology, & Stem Cell Transplant, Ann & Robert H. Lurie Children's Hospital of Chicago, Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL.
authors.forename: Alexis A
authors.initials: AA
authors.lastname: Thompson
authors.affiliation: Rodeghier Consultants, Chicago, IL.
authors.forename: Mark
authors.initials: M
authors.lastname: Rodeghier
authors.affiliation: Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, IL.
authors.forename: Bo
authors.initials: B
authors.lastname: Fernhall
authors.affiliation: Hematology, Oncology, & Stem Cell Transplant, Ann & Robert H. Lurie Children's Hospital of Chicago, Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL. Electronic address: rliem@luriechildrens.org.
authors.forename: Robert I
authors.initials: RI
authors.lastname: Liem
mesh_terms: D000293:Adolescent; D000755:Anemia, Sickle Cell / Q000503:physiopathology*; D005080:Exercise Test / Q000379:methods; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D011446:Prospective Studies; D020127:Recovery of Function