title: Living at an altitude adversely affects exercise capacity in Fontan patients.
abstract: BACKGROUND
  Data assessing the effect of altitude on Fontan haemodynamics are limited to experimental models and case reports. Both suggest a detrimental impact. This study describes exercise performance in patients with Fontan circulation and matched controls at a low altitude versus at sea level. We sought to assess the impact of increasing altitude on functional capacity in patients with Fontan palliation.
  
  
  METHODS
  A retrospective review of 22 patients at low altitude (1602 metres) and 119 patients at sea level with Fontan circulation, as well as age-, gender-, and altitude-matched controls, underwent maximal cardiopulmonary exercise testing. Linear regression models were created to determine the influence of altitude on differences in exercise variables between Fontan patients and their matched controls.
  
  
  RESULTS
  Peak oxygen consumption was 28.4 millilitres per kilogram per minute (72% predicted) for the sea-level cohort and 24.2 millilitres per kilogram per minute (63% predicted) for the moderate altitude cohort. The matched case-control differences for patients at moderate altitude were greater for peak oxygen consumption (-29% against -13%, p = 0.04), anaerobic threshold (-36% against -5%, p = 0.001), and oxygen pulse (-35% against -18%, p = 0.007) when compared with patients living at sea level. When compared to institution-matched controls, the same parameters fell by 3%, 8.9%, and 4.2%, respectively, for each increase of 1000 feet in residential altitude (p = 0.03, p = 0.001, and p = 0.05, respectively).
  
  
  CONCLUSIONS
  Patients with Fontan circulation at a higher altitude have impairment in aerobic capacity when compared with patients at sea level. Reduction in exercise capacity is associated with a reduction in stroke volume, likely related to increased pulmonary vascular resistance.
authors.affiliation: The Heart Institute, The Children's Hospital, Aurora, Colorado, USA. darst.jeffrey@tchden.org
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Darst
authors.forename: Marko
authors.initials: M
authors.lastname: Vezmar
authors.forename: Brian W
authors.initials: BW
authors.lastname: McCrindle
authors.forename: Cedric
authors.initials: C
authors.lastname: Manlhiot
authors.forename: Amy
authors.initials: A
authors.lastname: Taylor
authors.forename: Jennifer
authors.initials: J
authors.lastname: Russell
authors.forename: Anji T
authors.initials: AT
authors.lastname: Yetman
mesh_terms: D000293:Adolescent; D000531:Altitude; D015308:Anaerobic Threshold; D001794:Blood Pressure; D016022:Case-Control Studies; D002648:Child; D017079:Exercise Tolerance; D005260:Female; D018729:Fontan Procedure; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D012119:Respiration