title: What maintains the metabolic cost at maximal exercise in heart transplant recipients and coronary artery disease patients?
abstract: BACKGROUND
  In this study we assess the influence of disease status on hemodynamic and cardiac output values, as measured by oxygen utilization at peak aerobic exercise, in heart transplant recipients (HTRs) and coronary artery disease patients (CAD).
  
  
  METHODS
  Fifteen CAD patients and 13 HTRs (40.2 +/- 12.6 and 41.7 +/- 11.7 years, respectively) underwent a peak cardiopulmonary exercise test on bicycle ergometry. Arterial oxygen was defined on the basis of echocardiography and venous oxygen content.
  
  
  RESULTS
  At rest, except for cardiac output, oxygen uptake and lactate levels, all variables were significantly (p < 0.01) different between groups. At peak exercise, compared with HTRs, CAD patients had significantly (p < 0.0001) higher values for cardiac output (12.4 +/- 0.8 and 20.2 +/- 1.7 liters/min, respectively), stroke volume (87.3 +/- 5.4 and 129.3 +/- 9.7 ml, respectively) and oxygen uptake (22.7 +/- 3.6 and 29.7 +/- 2.7 ml/kg/min, respectively) (p < 0.01), whereas (a - v)O2 was significantly lower (127.0 +/- 4.3 and 141.9 +/- 6.4 O2 ml/liter, respectively; p < 0.0001).
  
  
  CONCLUSIONS
  The differences in oxygen utilization at peak exercise may be attributed to differences in energy metabolism, namely higher oxygen extraction in HTRs, compensating for the dramatically reduced oxygen delivery. It is further suggested that CAD patients and HTRs respond to a greater extent to maximal aerobic testing by reducing their left ventricular systolic function despite increased after-load.
authors.affiliation: Sports Medicine and Rehabilitation Division, Zinman College of Physical Education and Sport Sciences, Wingate Institute, Netanya, Israel.
authors.forename: Moran
authors.initials: M
authors.lastname: Sagiv
authors.forename: Ehud
authors.initials: E
authors.lastname: Goldhammer
authors.forename: David
authors.initials: D
authors.lastname: Ben-Sira
authors.forename: Ruthie
authors.initials: R
authors.lastname: Amir
mesh_terms: D000328:Adult; D001794:Blood Pressure; D002302:Cardiac Output; D003327:Coronary Disease / Q000503:physiopathology*; D004734:Energy Metabolism; D005080:Exercise Test; D005500:Follow-Up Studies; D006339:Heart Rate; D016027:Heart Transplantation / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000503:physiopathology