title: Physiological cardiac reserve: development of a non-invasive method and first estimates in man.
abstract: OBJECTIVE
  To investigate whether physiological cardiac reserve can be measured in man without invasive procedures and whether it is a major determinant of exercise capacity.
  
  
  METHODS
  Development of method of measurement and an observational study.
  
  
  METHODS
  A regional cardiothoracic centre.
  
  
  METHODS
  70 subjects with a wide range of cardiac function, from heart failure patients to athletes.
  
  
  METHODS
  Subjects underwent treadmill, symptom limited cardiopulmonary exercise tests to measure aerobic exercise capacity (represented by VO2max) and cardiac reserve. Cardiac output was measured non-invasively using the CO2 rebreathing technique.
  
  
  RESULTS
  Cardiac power output (CPOmax) at peak exercise was found to be significantly related to aerobic capacity: CPOmax (W) = 0.35 + 1.5 VO2max (1/min), r = 0.87, p < 0.001. It also correlated well with exercise duration (r = 0.62, p < 0.001), suggesting that cardiac reserve is a major determinant of exercise capacity. In the study, cardiac reserve ranged from 0.27 to 5.65 W, indicating a 20-fold difference between the most impaired cardiac function and that of the fittest subject.
  
  
  CONCLUSIONS
  A non-invasive method of estimating physiological cardiac reserve was developed. The reserve was found to be a major determinant of exercise capacity in a population of normal subjects and patients with heart disease. This method may thus be used to provide a clearer definition of the extent of cardiac impairment in patients with heart failure.
authors.affiliation: Institute for Cardiovascular Research, University of Leeds, UK.
authors.forename: G A
authors.initials: GA
authors.lastname: Cooke
authors.forename: P
authors.initials: P
authors.lastname: Marshall
authors.forename: J K
authors.initials: JK
authors.lastname: al-Timman
authors.forename: D J
authors.initials: DJ
authors.lastname: Wright
authors.forename: R
authors.initials: R
authors.lastname: Riley
authors.forename: R
authors.initials: R
authors.lastname: Hainsworth
authors.forename: L B
authors.initials: LB
authors.lastname: Tan
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001944:Breath Tests; D004562:Electrocardiography; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D006321:Heart / Q000502:physiology* / Q000503:physiopathology; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D010101:Oxygen Consumption; D015203:Reproducibility of Results; D013177:Sports / Q000502:physiology*