The Effect of Ivacaftor in Adolescents With Cystic Fibrosis (G551D Mutation): An Exercise Physiology Perspective

Purpose: The purpose of this report was to evaluate the influence of 12 weeks of ivacaftor treatment on the aerobic function of 2 teenage patients with cystic fibrosis (CF; Delta F508/G551D) using a maximal cardiopulmonary exercise test. Summary of Key Points: One patient, with relatively mild disease, demonstrated no clinically meaningful changes in maximal oxygen uptake (VO2max). However, in the second case, with more established lung disease on imaging, VO2max improved by approximately 30%, an improvement out of proportion with early lung function changes. This improvement resulted from increased muscle oxygen delivery and extraction. Statement of Conclusions: Cardiopulmonary exercise testing can monitor the extent and cause(s) of change following interventions such as ivacaftor, with the potential to identify functional changes independent from spirometry indices. Recommendations for Clinical Practice: Cardiopulmonary exercise testing represents an important and comprehensive clinical assessment tool, and its use as an outcome measure in the functional assessment of patients with CF is encouraged.