P172 Pre-operative insights from cardiopulmonary exercise testing in patients with pulmonary arteriovenous malformations

Introduction and Objectives Patients with pulmonary arteriovenous malformations (PAVMs) are difficult to assess for anaesthetic risks. Generally, they display well-preserved exercise tolerance, yet may have very low oxygen saturation due to their anatomical intrapulmonary right-to-left shunts. During pre-operative assessments in the general population, anaerobic threshold and peak VO2, measured by cardiopulmonary exercise testing (CPET), are increasingly recommended to identify high-risk patients, and appropriately plan post-operative management. For example, “high-risk” for major abdominal surgery has been suggested as an anaerobic threshold Methods In order to evaluate “pre-operative” risk categories for PAVM patients, anaerobic threshold and peak VO2, measured by ethically approved research cardiopulmonary exercise tests, were evaluated. Results 26 PAVM patients underwent research CPET evaluations between April 2011-May 2017. Their median age was 57 years (interquartile range (IQR): 42–66). 16 (61.5%) were male. The median oxygen saturation (SaO2) was 92% (IQR: 88–95) and median haemoglobin 15.6 g/dl (IQR: 14.2–16.6). Overall, the PAVM group achieved a median 92% of the predicted maximum work (IQR: 67–106), anaerobic threshold ranged from 7.6–24.5 ml min-1 kg-1 (median: 12.35; IQR: 9.5–17.35), and peak VO2 ranged from 11.2–45.5 ml min-1 kg-1 (median: 19.8; IQR: 16.7–28.4). Anaerobic threshold placed 11/26 (42.3%) in the suggested high-risk category for major abdominal surgery. In this group, the anaerobic threshold ranged from 7.6–10.8 ml min-1 kg-1. Similarly, peak VO2 placed 14/26 (53.8%) in a high-risk category. Their peak VO2 ranged from 11.2–16.5 ml min-1 kg-1. There was full concordance between the categories determined by the 2 measurements. Notably, 6 patients were retested 3–31 months after embolization treatment resulting in increased SaO2. However, there was no increase in anaerobic threshold or peak VO2, and the 3 patients from this group initially in a higher risk category remained. Conclusion Anaerobic threshold and peak VO2 suggest high proportions of PAVM patients are in a high-risk pre-operative risk category. The data suggest an important role for anaesthetic assessments. Noting that 1 in 2600 people are estimated to have PAVMs, further study is recommended to develop appropriate clinical guidance, and allocate resources to optimise care.