Title: A Feasibility Study of High-intensity Interval Exercise Training before Abdominal Aortic Aneurysm Repair (HIT AAA)
Funder: Department of Health (England)

Abstract: Abdominal aortic aneurysm (AAA) is a frequently lethal disease affecting 4 to 8% of men aged >65 years. Mechanical intervention (i.e., open surgery using a prosthetic graft to repair the aneurysm or endovascular placement of a stent graft) is the only effective treatment for preventing aneurysm-related rupture and death; however, aneurysm repair itself carries high risk. The 30-day mortality rate associated with elective open repair is higher in the UK than in comparable countries: 7 versus 3.5%. Hence, there is currently a national drive, coordinated through the AAA Quality Improvement Plan, to improve outcomes for AAA repair. Low cardiopulmonary fitness increases the risk of early post-operative complications and death after open AAA repair and other major non-cardiac procedures. Therefore, fitness should be optimised before aneurysm repair. High-intensity interval exercise training (HIT) is a potent, time-efficient and low-cost strategy for enhancing cardiopulmonary fitness. However, the feasibility and effectiveness of HIT in patients awaiting AAA repair is unknown. We are proposing a feasibility study for a definitive randomised controlled trial of a pre-operative HIT intervention to improve post-operative outcomes in patients undergoing elective repair of an AAA. The main aim is to identify the primary outcome and estimated sample size for the subsequent trial. A secondary aim is to investigate the suitability of HIT, primarily in terms of compliance, acceptability, and its impact on cardiopulmonary fitness. This is a two-centre, two-arm, parallel-group randomised trial. A minimum of 50 patients awaiting elective repair of a 5.5 to 7.0 cm infra-renal AAA will be randomised, in a 1:1 ratio of open surgical to endovascular repair, to HIT or usual care control. Patients randomised to HIT will complete three hospital-based exercise sessions per week, for 4 weeks. Each session will include 4 minutes of hard-to-very hard cycling followed by 4 minutes of easy cycling, repeated 4 times. Outcomes to be assessed before randomisation and 24 to 48 hours before aneurysm repair (week 5 where possible) include ventilatory threshold via cardiopulmonary exercise testing, maximum AAA diameter via trans-abdominal ultrasound, and health-related quality of life using the SF-36 and EQ-5D questionnaires. In the post-operative period, we will record destination (ward or critical care unit), organ-specific morbidity using the Post-operative Morbidity Survey Score, mortality, and the durations of critical care and hospital stay. Twelve weeks after discharge, participants will be interviewed via telephone to re-assess quality of life and determine post-discharge healthcare utilisation. The costs associated with the exercise intervention and healthcare utilisation (in-hospital and post-discharge) will be calculated. A definitive randomised trial will be considered feasible if an appropriate primary outcome is identified and if the lower limit of the 90% confidence interval for the proportion of the exercise group complying with the intervention is ≥67%. A patient will be deemed compliant if they complete ≥75% of the scheduled sessions plus all maintenance sessions if surgery is delayed. For the potential primary outcomes of a definitive trial, the likely effect of the exercise intervention will be estimated via standard intervention minus control comparisons. We will examine the disposition of the 90% confidence interval for the observed effect to the minimum clinically important difference for each variable. A prospective economic evaluation will also be rehearsed to develop and refine methods for the subsequent trial. The potential patient benefits of pre-operative HIT include increased cardiopulmonary fitness, reduced rates of early post-operative complications and death, and reduced hospital length of stay. Given the low cost of implementing pre-operative HIT, the potential reduction in healthcare resource utilisation would likely make this a cost-effective intervention for the NHS.


Research activity codes: 6.4 SURGERY;6.7 PHYSICAL
Health categories: CARDIOVASCULAR