Effect of short-term exercise training on aerobic fitness in patients with abdominal aortic aneurysms: a pilot study

Background: Patients with abdominal aortic aneurysms (AAA) represent a high-risk surgical group. Despite medical optimization and radiological stenting interventions, mortality remains high and it is difficult to improve fitness. The aim of this pilot study was to evaluate the effect of a 6 week, supervised exercise programme (30 min continuous moderate intensity cycle ergometry, twice weekly) on anaerobic threshold (AT) in subjects with AAA.
Methods: Thirty participants with an AAA under surveillance were randomized to either the supervised exercise intervention (n=20) or a usual care control group (n=10). AT was measured using cardiopulmonary exercise testing, at baseline (AT1), week 5 (AT2), and week 7 (AT3). The change in AT (AT3–AT1) between the groups was compared using a mixed model ANCOVA, providing the mean effect together with the standard deviation (SD) for individual patient responses to the intervention. The minimum clinically important difference (MCID) was defined as an improvement in AT of 2 ml O2 kg–1 min–1.
Results: Of the 30 participants recruited, 17 of 20 (exercise) and eight of 10 (control) completed the study. The AT in the intervention group increased by 10% (equivalent to 1.1 ml O2 kg–1 min–1) compared with the control (90% confidence interval 4–16%; P=0.007). The SD for the individual patient responses to the intervention was 8%. The estimated number needed to treat (NNT) for benefit was 5 patients.
Conclusions: The small mean benefit was lower than the MCID. However, the marked variability in the individual patient responses revealed that a proportion of patients did benefit clinically, with an estimated NNT of 5.