Cardiopulmonary exercise testing demonstrates maintenance of exercise capacity in patients with hypoxemia and pulmonary arteriovenous malformations

Chest. 2014 Sep;146(3):709-718. doi: 10.1378/chest.13-2988.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Anaerobic Threshold / physiology
  • Arteriovenous Fistula / physiopathology*
  • Body Mass Index
  • Carbon Dioxide / metabolism
  • Case-Control Studies
  • Exercise Test*
  • Exercise Tolerance / physiology*
  • Female
  • Humans
  • Hypoxia / physiopathology*
  • Male
  • Middle Aged
  • Oxygen Consumption / physiology
  • Physical Endurance / physiology*
  • Pulmonary Artery / abnormalities*
  • Pulmonary Artery / physiopathology
  • Pulmonary Veins / abnormalities*
  • Pulmonary Veins / physiopathology


  • Carbon Dioxide

Supplementary concepts

  • Pulmonary Arteriovenous Fistulas