title: Hemodynamic causes of exercise intolerance in Fontan patients.
abstract: BACKGROUND
  Exercise intolerance is frequent among Fontan patients and an important determinant for quality of life. This study investigated the hemodynamic causes of impaired exercise capacity in Fontan patients with particular focus on the influence of stroke volume index (SVI) and heart rate (HR).
  
  
  RESULTS
  In 38 Fontan patients, peak oxygen consumption (VO2), SVI and HR were recorded during incremental load exercise test and compared with 19 age and gender matched controls. SVI (ml/m(2)) was lower in patients than controls during warm-up (28[26-31] vs. 35[30-39], p=0.0093), at submaximal (40[37-43] vs. 55[51-59], p<0.0001) and at maximal exercise (38[35-40] vs. 54[51-58], p<0.0001). Similarly, HR (% of expected maximum) was lower in patients at warm-up (45[43-48]% vs. 64[57-64]%, p<0.0001), submaximal (71[68-75]% vs 85[82-88]%, p<0.0001) and maximal exercise (84[80-88]% vs. 97[95-99]%, p<0.0001). Furthermore, SVI dropped 14% (from 44[41-48] to 38[35-40] ml/m(2)) in Fontan patients from the peak plateau to maximal exercise vs. 5% (from 57[53-61] to 54[51-58] ml/m(2)) in controls, p<0.0001. The low SVI and HR explained 67% and 20% of the difference in peak VO2 between Fontan patients and controls respectively.
  
  
  CONCLUSIONS
  SVI decreased significantly in Fontan patients near the end of maximal effort exercise. The low SVI at maximal exercise was the most important hemodynamic factor limiting exercise capacity in Fontan patients, whereas chronotropic impairment had a smaller impact. The low SVI and HR at maximal exercise accounted for the difference in peak VO₂ between Fontan patients and controls in this study.
  
  
  BACKGROUND
  http://www.cvk.sum.dk/CVK/Home/English.aspx (protocol nr: H-3-2010-045).
authors.affiliation: Department of Cardiology, Copenhagen University Hospital, Rigshospitalet, Denmark. Electronic address: andershebert@gmail.com.
authors.forename: Anders
authors.initials: A
authors.lastname: Hebert
authors.affiliation: Department of Cardiology, Copenhagen University Hospital, Rigshospitalet, Denmark.
authors.forename: Annette S
authors.initials: AS
authors.lastname: Jensen
authors.affiliation: Institute of Sports Medicine, Department of Orthopedic Surgery, Bispebjerg Hospital and Center for Healthy Ageing, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
authors.forename: Ulla R
authors.initials: UR
authors.lastname: Mikkelsen
authors.affiliation: Department of Cardiology, Copenhagen University Hospital, Rigshospitalet, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Idorn
authors.affiliation: Department of Cardiology, Aarhus University Hospital, Skejby, Aarhus, Denmark.
authors.forename: Keld E
authors.initials: KE
authors.lastname: Sørensen
authors.affiliation: Department of Cardiology, University Hospital of Lund, Sweden.
authors.forename: Ulf
authors.initials: U
authors.lastname: Thilen
authors.affiliation: Department of Pediatric Cardiology, University Hospital of Lund, Sweden.
authors.forename: Katarina
authors.initials: K
authors.lastname: Hanseus
authors.affiliation: Department of Cardiology, Copenhagen University Hospital, Rigshospitalet, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Søndergaard
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002648:Child; D005080:Exercise Test / Q000379:methods / Q000639:trends*; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D018729:Fontan Procedure / Q000639:trends*; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology; D055815:Young Adult
keywords: Cardio-pulmonary exercise test; Chronotropic impairment; Fontan; Stroke volume