title: Cardiac output and pulmonary gas exchange at maximal exercise after atrial redirection for complete transposition.
abstract: OBJECTIVE
  To assess the determinants of exercise capacity and exercise oxygenation after atrial redirection for complete transposition.
  
  
  RESULTS
  At graded bicycle ergometry, including respiratory and arterial blood gas analyses, intra-arterial blood pressure recording, and cardiac output determination (dye-dilution technique), we tested 17 post-Mustard/Senning patients, 8.9-22.0 years old (mean 14.5, SD 4.0). Reference data were obtained by similar methods. At maximal exercise, oxygen uptake (29.6 ml x kg(-1) x min(-1)) and heart rate (167 beats x min(-1)) were low (P<0.001). Right-to-left shunts were detected in five patients. Arterial oxygen partial pressure and saturation fell in all subjects (P<0.0001). In 15/16 (94%) the alveolar-arterial oxygen partial pressure difference was > +2 SD. In 13/15 (87%) stroke volumes fell during exercise. Cardiac output per oxygen uptake was low (P<0.0001), which implies a high arteriovenous oxygen difference and a low mixed venous oxygen content at peak exercise.
  
  
  CONCLUSIONS
  The low exercise capacity was caused by a combination of low maximally attained heart rate and falling stroke volumes. The impaired arterial oxygenation may be caused by a combination of pulmonary ventilation/perfusion mismatch, a low mixed venous content and atrial shunting in some patients.
authors.affiliation: Department of Paediatrics, Sahlgrenska University Hospital, Göteborg, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Gilljam
authors.forename: B O
authors.initials: BO
authors.lastname: Eriksson
authors.forename: R
authors.initials: R
authors.lastname: Sixt
mesh_terms: D000293:Adolescent; D002302:Cardiac Output / Q000502:physiology*; D006348:Cardiac Surgical Procedures / Q000379:methods; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D010100:Oxygen / Q000097:blood; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D013318:Stroke Volume / Q000502:physiology; D014188:Transposition of Great Vessels / Q000503:physiopathology* / Q000601:surgery*
chemical_list: D010100:Oxygen