title: Pulmonary gas exchange during exercise in Fontan patients at a long-term follow-up.
abstract: Desaturation during exercise in the Fontan type of circulation may be due to known right-to-left shunts in some patients, while in others there are no obvious signs of shunts.
  
  
  OBJECTIVE
  To evaluate the gas exchange and exercise capacity in patients with Fontan circulation.
  
  
  METHODS
  Twenty patients with the Fontan type of circulation, median age at operation 7.5 years (3.0-35 years), follow-up time 12.1 years (8.3-20.4 years), were included. The intrapulmonary gas mixing (N(2)-slope) and diffusion capacity for carbon monoxide (D(LCO)) was evaluated and determination of cardiac output was performed at rest and during exercise with measurements of ventilation, oxygen uptake, respiratory rate, carbon dioxide production and heart rate. Samples for blood gases (P(a)O(2), S(a)O(2)) were obtained at rest and at the end of each work load.
  
  
  RESULTS
  The median exercise capacity was 1.47 l min(-1). During exercise, all the patients had an alveolar-arterial oxygen partial pressure difference (P(A-a)O(2)) above 2 SD. Patients with known right-to-left shunts had lower P(a)O(2) and S(a)O(2) values and higher P(A-a)O(2) values both at rest, median 7.5 kPa, 90%, and 7.2 kPa, respectively, and during exercise, median 5.8 kPa, 77% and 10.1 kPa, compared with those with no shunts, median 11.2 kPa, 97% and 4.1, respectively, at rest and 9.7 kPa, 94%, and 6.3 during exercise (P<0.01). No correlation was found between cardiac index, the N(2)-slope or the D(LCO) at rest and the P(a)O(2) and S(a)O(2) at rest or during exercise.
  
  
  CONCLUSIONS
  In patients with the Fontan type of circulation, right-to-left shunts are the major cause of desaturation during exercise.
authors.affiliation: Department of Paediatric Cardiology, The Queen Silvia Children's Hospital, SE-416 85 Göteborg, Sweden. eva.stromvall-larsson@vgregion.se
authors.forename: Eva
authors.initials: E
authors.lastname: Strömvall-Larsson
authors.forename: Bengt O
authors.initials: BO
authors.lastname: Eriksson
authors.forename: Daniel
authors.initials: D
authors.lastname: Holmgren
authors.forename: Rune
authors.initials: R
authors.lastname: Sixt
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D018729:Fontan Procedure; D006330:Heart Defects, Congenital / Q000503:physiopathology* / Q000601:surgery*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D010807:Physical Endurance; D005082:Physical Exertion; D011659:Pulmonary Gas Exchange; D016896:Treatment Outcome