title: Cardiopulmonary exercise testing demonstrates maintenance of exercise capacity in patients with hypoxemia and pulmonary arteriovenous malformations.
abstract: BACKGROUND
  Patients with pulmonary arteriovenous malformations (PAVMs) are unusual because hypoxemia results from right-to-left shunting and not airway or alveolar disease. Their surprisingly well-preserved exercise capacity is not generally appreciated.
  
  
  METHODS
  To examine why exercise tolerance is preserved, cardiopulmonary exercise tests were performed while breathing room air in 21 patients with radiologically proven PAVMs, including five restudied 3 to 12 months after embolization when their PAVMs had regressed. Where physiologic matching was demonstrable, comparisons were made with 12 healthy control subjects.
  
  
  RESULTS
  The majority of patients achieved their predicted work rate despite a resting arterial oxygen saturation (SaO₂) of 80% to 96%. Peak work rate and oxygen consumption (VO₂) were no lower in patients with more hypoxemia. Despite higher SaO₂ following embolization (median, 96% and 90%; P = .009), patients achieved similar work rates and similar peak VO₂. Strikingly, treated patients reset to virtually identical peak oxygen pulses (ie, VO₂ per heart beat) and in many cases to the same point on the peak oxygen pulse/work rate plot. The 21 patients had increased minute ventilation (VE) for given increases in CO₂ production (VE/VCO₂ slope), but perceived dyspnea was no greater than in the 12 control subjects or in the same patients before compared to after embolization comparison. Overall, work rate and peak VO₂ were associated not with oxygenation parameters but with VE/VCO₂ slope, BMI, and anaerobic threshold.
  
  
  CONCLUSIONS
  Patients with hypoxemia and PAVMs can maintain normal oxygen delivery/VO₂ during peak exercise. Following improvement of SaO₂ by embolization, patients appeared to reset compensatory mechanisms and, as a result, achieved similar peak VO₂ per heart beat and peak work rates.
authors.affiliation: Divisions of Cardiovascular Medicine, Imperial College Healthcare NHS Trust.
authors.forename: Luke S G E
authors.initials: LSGE
authors.lastname: Howard
authors.affiliation: National Heart and Lung Institute Cardiovascular Sciences, Imperial College London, London, England; Respiratory Sciences, Imperial College London, London, England; Imperial College School of Medicine, Imperial College London, London, England.
authors.forename: Vatshalan
authors.initials: V
authors.lastname: Santhirapala
authors.affiliation: Respiratory Medicine, Imperial College Healthcare NHS Trust.
authors.forename: Kevin
authors.initials: K
authors.lastname: Murphy
authors.affiliation: Divisions of Cardiovascular Medicine, Imperial College Healthcare NHS Trust.
authors.forename: Bhashkar
authors.initials: B
authors.lastname: Mukherjee
authors.affiliation: Clinical Chemistry, Imperial College Healthcare NHS Trust.
authors.forename: Mark
authors.initials: M
authors.lastname: Busbridge
authors.affiliation: Respiratory Medicine, Imperial College Healthcare NHS Trust.
authors.forename: Hannah C
authors.initials: HC
authors.lastname: Tighe
authors.affiliation: Imaging, Imperial College Healthcare NHS Trust.
authors.forename: James E
authors.initials: JE
authors.lastname: Jackson
authors.affiliation: Respiratory Medicine, Imperial College Healthcare NHS Trust; National Heart and Lung Institute Cardiovascular Sciences, Imperial College London, London, England; Respiratory Sciences, Imperial College London, London, England.
authors.forename: J Michael B
authors.initials: JMB
authors.lastname: Hughes
authors.affiliation: Respiratory Medicine, Imperial College Healthcare NHS Trust; National Heart and Lung Institute Cardiovascular Sciences, Imperial College London, London, England. Electronic address: c.shovlin@imperial.ac.uk.
authors.forename: Claire L
authors.initials: CL
authors.lastname: Shovlin
mesh_terms: D000368:Aged; D015308:Anaerobic Threshold / Q000502:physiology; D001164:Arteriovenous Fistula / Q000503:physiopathology*; D015992:Body Mass Index; D002245:Carbon Dioxide / Q000378:metabolism; D016022:Case-Control Studies; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology*; D011651:Pulmonary Artery / Q000002:abnormalities* / Q000503:physiopathology; D011667:Pulmonary Veins / Q000002:abnormalities* / Q000503:physiopathology
chemical_list: D002245:Carbon Dioxide