Multimodality magnetic resonance evaluating the effect of enhanced physical exercise on the growth rate, flow haemodynamics, aneurysm wall and ventricular-aortic coupling of patients with small abdominal aortic aneurysms (AAA MOVE trial): a study protocol for an open-label randomised controlled trial

Abstract

Introduction

The best lifestyle for small abdominal aortic aneurysms (sAAA) is essential for its conservative management. Physical exercise can improve the cardiopulmonary function of the patients, but it remains unclear which specific type of exercise is most beneficial for individuals with sAAA. The current study was designed to investigate the effect of physician-guided enhanced physical exercise programme on the aorto-cardiac haemodynamic environment, aneurysm sac wall, cardiac function and growth rate of sAAA by multimodality MRI.

Methods and analysis

AAA MOVE study is a prospective, parallel, equivalence, randomised controlled trial. Eligible individuals will be recruited if they are diagnosed with sAAA (focal dilation of abdominal aorta with maximum diameter <5 cm), without contraindication for MRI scanning, or severe heart failure, or uncontrolled arrhythmia. Participants will be randomly allocated to intervention group (physician-guided enhanced physical exercise programme: mainly aerobic training) and control group (standard clinical care) separately in a 1:1 ratio. The primary outcome is 12-month growth rate of sAAA. The first set of secondary outcomes involve multimodality MRI parameters covering flow haemodynamics, aortic wall inflammation and cardiac function. The other secondary outcome (safety end point) is a composite of exercise-related injury, aneurysm rupture and aneurysm intervention. Follow-up will be conducted at 6 and 12 months after intervention.

Ethics and dissemination

This study was approved by the Ethics Committee on Biomedical Research of West China Hospital (approval number: 2023-783) on 16 June 2023. Main findings from the trial will be disseminated through presentations at conferences, peer-reviewed publications and directly pushed to smartphone of participants.

Trial registration number

ChiCTR2300073334.

STRENGTHS AND LIMITATIONS OF THIS STUDY.

• This trial was designed to investigate the effect of physician-guided enhanced physical exercise programme on the aorto-cardiac haemodynamic environment, aneurysm sac wall, cardiac function and growth rate of small abdominal aortic aneurysms (sAAA) by multimodality MRI.

• The physician-guided enhanced physical exercise programme mainly involves aerobic training and stretching, evaluated by the validated Borg’s rating of perceived exertion.

• Outcome assessors and data analysts are blinded to the group allocation of participants.

• The primary outcome was the 12-month AAA growth rate; the secondary outcomes were multidimensional aorto-cardiac alterations including aortic flow haemodynamics, aneurysm wall inflammation and cardiac function and exercise-related injury; patient-centred outcomes were cardiopulmonary capacity, anthropometry, frailty, quality of life and clinical outcomes.

• Due to the difficulty of continuous monitoring, the compliance to the exercise regimen may represent a potential limitation when interpreting our results.

Introduction

Abdominal aortic aneurysm (AAA) is one the most common aortic diseases in the elderly population, affecting 4%–8% individuals during screening studies.^{1 2} According to recent publications, AAA rupture or related complications were considered as the 10th leading cause of death in elderly male patients.³ Current guidelines from European Society of Vascular Surgery and North American Society of Vascular Surgery recommended close surveillance with conservative management for small abdominal aortic aneurysm (sAAA) <5.0 cm.^{4 5} However, there were still 10%–20% sAAA that may need intervention or rupture during the surveillance,^{6 7} and these proportions may even be underestimated.⁸ Thus, understanding the factors and patterns of sAAA progression during follow-up is vital for conservative management.

Physical exercise is a useful lifestyle intervention which can improve body function and long-term outcomes for cardiovascular pathologies.^{9 10} As for patients with AAA, the clinical application of exercise prescription should be balanced for the advantages of cardiopulmonary improvement against risk of AAA progression and exercise-related injury. Recently, the Abdominal Aortic Aneurysm Get Fit trial revealed that enhanced physical exercise in patients with AAA could provide more improvements in peak oxygen uptake, anaerobic threshold, triglycerides and health-related quality of life.¹¹ However, only one publication revealed a modest inverse association between AAA growth and moderate-intensity exercise.¹² Moreover, the effect of enhanced physical exercise on the flow haemodynamic environment, local wall inflammation and upstream ventricular-aortic coupling of sAAA remains unknown.

In the recent decade, multimodality MRI is increasingly applied to evaluate the progression of various pathologies from multiple dimensions.¹³ Four-dimensional (4D) flow MRI was developed to attain comprehensive real-time visualisation and quantification of ventricular-aortic coupling and blood flow haemodynamics, ranging from basic aspects such as peak velocity and flow volume to more advanced parameters such as wall shear stress (WSS), pulse wave velocity (PWV), viscous energy loss (VEL) and visualisation of flow pathways.^{14 15} In addition, mounting evidence indicated that T1 mapping could reflect the degree of myocardial fibrosis, while T2 mapping could reveal high-risk pathologies, for example, wall oedema and intramural haemorrhage.^{16 17}

Therefore, we designed a prospective, parallel, equivalence, randomised controlled trial (RCT) to evaluate the effect of enhanced physical exercise on the progression of sAAA by multimodality MRI, covering growth rate, flow haemodynamics, aneurysm sac wall and ventricular-aortic coupling in the upstream heart and downstream abdominal aorta. The primary focus would be 12-month growth rate of sAAA. Our primary hypothesis was that the growth rate of sAAA was equivalent between the two arms (enhanced physical exercise vs conventional medical care). The secondary hypothesis was that enhanced physical exercise may improve multidimensional cardiovascular function involving aortic flow haemodynamics, aneurysm wall and ventricular-aortic coupling.

Methods and analysis

Study setting and ethics

The multimodality evaluating exercise on sAAA (AAA MOVE) trial is an open-label, equivalence RCT conducted in a tertiary academic hospital with high-volume of AAA treatment, West China Hospital of Sichuan University. The study was approved by the Ethics Committee on Biomedical Research of West China Hospital (approval number: 2023-783) on 16 June 2023. The trial was registered in the Chinese Clinical Trial Registry (registration number: ChiCTR2300073334) on 7 July 2023. The protocol of AAA MOVE trial was reported according to the Standard Protocol Items: Recommendations for Interventional Trials guidelines.¹⁸

Participants enrolment

Patients diagnosed with AAA in the outpatient or inpatient clinics will be assessed for inclusion eligibility if they meet all of the following criteria: (1) the maximum diameter of the AAA <5.0 cm in women and 5.5 cm in men, (2) no need for surgical intervention judged with the morphology and symptom and (3) willing to sign the informed consent.

Participants will be excluded if they meet one of the following criteria: (1) patients had contraindications for MRI scanning, for example, pacemaker implantation, claustrophobic, etc, (2) patients had severe heart failure who cannot lie down for half an hour, (3) patients had persistent controlled arrhythmia, (4) partially or totally dependent patients who need daily care or support from others, (5) patients had severe cardiac, pulmonary and cerebral comorbidities who cannot tolerate enhanced physical exercise and (6) patients with connective tissue diseases and infectious AAA.

After admission, the researcher will inform the eligible individuals with the trial participation, then the participants will sign the informed consent and fill an information collection form prior to the initial multimodality MRI screening. After participation, withdrawal from the study is permitted at any time for any reason without any alteration to treatment plans. To achieve adequate enrolment, we will provide fast-track (priority) channel for outpatient appointments and online follow-up consultation for participants. Patients were involved in the conduct of our research.

Assignment of intervention

Eligible participants will be randomly allocated to intervention group (enhanced physical exercise programme) and control group (standard clinical care) separately in a 1:1 ratio. Assignment of intervention will be performed at the beginning. A biostatistician will generate the allocation sequence using stratified randomisation according to gender. The allocation concealment is ensured by sequentially numbered, opaque, sealed envelopes. The participants will be dropped out of the study if they cannot fulfil the exercise regimen or suffer from exercise-related adverse events during follow-up. The outcome assessors and data analysts are blinded to interventions. The participant timeline is shown in figure 1.

Figure 1.

Participant timeline of AAA MOVE trial. AAA, abdominal aortic aneurysm; C, control; D, dropped out due to intolerance of intervention; E, end of observation due to occurrence of aneurysm progression; I, intervention; mITT, modified intention-to-treat; N1, participants assigned to intervention; N2, participants assigned to control; PP, per-protocol; P, participants, Q, quit from the trial unrelated to aneurysm or intervention; R, randomizsation.

The details of the physician-guided enhanced physical exercise programme are as follows:

1. Content: ideal physical exercise programme for patients with sAAA mainly focus on aerobic training and stretching, based on schedule of elderly patients with cardiovascular diseases.^{19 20} Considering the potential effect on intra-abdominal pressure, resistance training is not considered. The safety of the physical exercise has been verified in previous research.²¹ An example of the exercise regimen is shown in table 1. The patients are also encouraged to do exercise outside of the programme.

2. Intensity and duration: the intensity of exercise is evaluated by the validated Borg’s rating of perceived exertion (RPE), ranging from 6 (no exertion) to 20 (maximal exertion).²² The required intensity of intervention is classified into two groups according to the age of the patients: 14–16 scores for patients aged ≤65 years; 12–14 scores for patients aged >65 years. The frequency of exercise is at least four times a week, and each session may last 30–45 min every time. The duration of intervention is 12 months.

Table 1.

Example regimen of enhanced physical exercise

Stage	Item	Intensity	Duration
Warm up	Shoulder rolls	RPE 7	1 min
	Ankle rolls	RPE 7	1 min
	Calf flexes	RPE 7	1 min
	Regular to fast walking	RPE 10–12	10 min
Lower extremity strength	Horse stance	RPE 13–14	1 min each rep (or as long as you can)/3 sets
	Sit to stand	RPE 13–14	8–12 reps/3 sets
Aerobic training (select one or several combinations)	Running	RPE 13–16	20 min
	Cycling	RPE 13–16
	Elliptical trainer/Treadmill	RPE 13–16
	Swimming	RPE 13–16
Ball games* (select one or several combinations)	Table tennis (ping pong)	RPE 13–16	20 min
	Badminton	RPE 13–16
	Gateball	RPE 11–12
Stretching	Stretching	RPE 7	1 min

*Encouraged but not required in the regimen.

rep, replication; RPE, rating of perceived exertion.

Control group will receive standard clinical care including lifestyle intervention (diet control, weight loss, smoking cessation) and best medical management (control of blood pressure and plasma lipid level). Intervention group also share the same standard clinical care except for extra exercise programme.

Multimodality MRI

All participants will be assessed by the multimodality MRI at enrolment, 6 and 12 months in AAA MOVE trial. The multimodality MRI is performed at a 3.0 T magnetic resonance system (Ingenia Elition, Philips Healthcare) equipped with a 32-channel phased array body coil, covering the following four dimensions:

1. Diameter measurement: two-dimensional (2D) phase-contrast MRI.

2. Aortic flow haemodynamics: 4D flow MRI with echo planar imaging readout acquisition.

3. Aortic wall assessment: three-dimensional (3D) T1-weighted black-blood volumetric isotropic turbo spin echo (TSE) acquisition (3D-T1-BB-VISTA), T1 mapping and T2 mapping.

4. Ventricular-aortic coupling: ECG-gated balance steady-state free precession cine sequence.

The detailed multimodality MRI acquisition in AAA MOVE trial is described in online supplemental appendix 1.

Imaging processing

The multimodality MRI datasets are analysed using a postprocessing software, CVI 42 (Circle Cardiovascular Imaging, Calgary, Canada). Offset correction and phase unwrapping are applied to any phase offset aliasing and image noise. Both planar and segmental haemodynamic parameters were analysed from the 4D flow datasets. A total of 10 planes were set at the following regions of interest (ROI) perpendicular to the vessel centreline: beginning of aneurysm neck (planes beneath the lower renal artery), end of aneurysm neck (origin of aneurysm sac), the plane of AAA at maximum diameter, aortic bifurcation, origin of bilateral common iliac arteries (CIA), planes of bilateral CIA at maximum diameter, end of bilateral CIA (figure 2A). Segmental haemodynamic parameters are calculated based on whole range of aorta and infrarenal abdominal aorta. The endovascular and extravascular of the neck of AAA and the plane of AAA at maximum diameter were delineated manually in 2D BB T1-weighted TSE/3D-T1-BB-VISTA (figure 2B), T1 mapping and T2 mapping. The endocardial and epicardial borders of the ventricle were automatically delineated at the end-diastolic and end-systolic phases in each short axis cine image (figure 2C). If the delineation is not accurate, the ROI will be adjusted manually.

Figure 2.

Image postprocessing. The placement of regions of interest in four-dimensional flow MRI (A); the measurement of thickness of aorta wall (B); the measurement of cardiac function and stress parameters in cine images (C). AAA, abdominal aortic aneurysm; CIA, common iliac arteries.

Primary and secondary outcomes

The primary study end point: change in AAA diameter at 12 months, measured from outer edge to outer edge of the vessel wall.

Secondary outcomes include changes of the parameters, at 6 and 12 months, that are discussed ahead.

Aortic flow haemodynamics

• Basic flow haemodynamics: flow volume, regurgitation fraction, peak systolic velocity at each ROI.

• WSS: overall WSS, circumferential WSS, axial WSS at each ROI.

• Pressure drop.

• Qualitative description of the flow regime in AAA: with 4D flow MRI, we will describe the flow regime based on our previous flow pattern classification.²³

• Quantification of vortical flow: vorticity (defined as the curl of the flow velocity vector), maximum vortex volume, accumulated vortex volume,²⁴ vortex growth (change in volume during one cardiac cycle), vortex core displacement (the displacement of vortex core during one cardiac cycle)²⁵ and temporal vortical existence.

• Quantification of helical flow: helicity (defined as the integrated dot product of the local velocity vector and the vorticity vector), helicity density and relative helicity density, maximum helical volume, accumulated helical volume and temporal helical existence.²⁴ All volumetric parameters of vortical and helical flow were calculated as an index which normalised to the body surface area.

  ${\displaystyle Vorticity=\overrightarrow{\omega }=\mathrm{\nabla }\times \overrightarrow{u}}$(1)

  ${\displaystyle Helicity=\int \overrightarrow{u}\cdot \overrightarrow{\omega }dV}$(2)

  ${\displaystyle Helicitydensity=\overrightarrow{u}\cdot \overrightarrow{\omega }}$(3)

  ${\displaystyle Relativehelicitydensity=\frac{\overrightarrow{u}\cdot \overrightarrow{\omega }}{\overrightarrow{\left|u\right|}\cdot \overrightarrow{\left|\omega \right|}}=cos\theta }$(4)

  where $\overrightarrow{u}$ is velocity vector (m/s), $\nabla$ is the spatial gradient operator and $dV$ is the unit voxel volume.

• Other flow parameters: flow transition (from vortex to helical flow or vice versa), VEL of infrarenal aorta, describing the overall attrition of kinetic energy resulted from abnormal flow pattern.

As shown in figure 3, basic haemodynamic parameters are generated by CVI 42 (Circle Cardiovascular Imaging) and analysed by two radiologists with 3 years of cardiovascular magnetic resonance (CMR) experience. Advanced parameters, mainly quantification of flow characteristics, are handled by custom-made Python scripts (www.python.org) and MATLAB scripts (Mathworks, Natick, Massachusetts, USA). Segmentation and vascular modelling are performed by MIMICS V.21.0 (Materialise, Leuven, Belgium). Postprocessing and visualisation are using an open-source engine (Paraview, Kitware, Clifton, New York, USA) (figure 4).

Figure 3.

Methods for measuring haemodynamic parameters. ROI, regions of interest.

Figure 4.

Methods for quantification of flow characteristics. ROI, regions of interest.

Aneurysm sac wall assessment

• 2D BB T1-weighted TSE/3D-T1-BB-VISTA: mural thrombus thickness, vessel wall thickness.

• T1 value.

• T2 value.

Ventricular-aortic coupling

• Stiffness of aorta: PWV of whole aorta.²⁶

• Afterload of left ventricle assessed by the VEL of whole aorta.²⁷

• Ventricular structure: left ventricle wall thickness, ventricular long axis, left ventricle mass index.

• Ventricular function: end-diastolic volume, end-systolic volume, stroke volume, ejection fraction (EF), cardiac output (CO).

• Myocardial strain: global radial strain, global circumferential strain and global longitudinal strain.

Safety end point

Freedom of exercise-related injury at 12 months, defined as a composite end point consisting of fracture, immobility, aneurysmal rupture resulted from exercise-related fall or injury. The safety end point was reported by participants through online software WeChat at any time, and recorded by outcome assessors. Observation will stop if AAA progression (receiving intervention or rupture) occurs.

Other outcomes of interest (patient-centered outcomes)

In addition to multimodality imaging outcomes, we also evaluate comprehensive body changes from the following five dimensions:

1. Cardiopulmonary capacity: measured by resting heart rate, peripheral oxygen saturation.

2. Anthropometry: triceps skinfold,²⁸ anterior abdominal subcutaneous fat thickness.

3. Frailty: measured by the modified frailty index,²⁹ hand grip strength,³⁰ psoas major area.³¹

4. Quality of life: measured by EuroQol 5-dimensions 5-level (EQ-5D-5L) scale.³²

5. Clinical outcomes: overall survival, major adverse cardiovascular events, pulmonary infection, renal function decline, etc.

Data collection

In AAA MOVE trial, all data including participant personnel information will be kept in the form of a cryptographic web spreadsheet, which can only be accessed and edited with specific permissions. Personal information will not be disclosed without their written consent. Apart from imaging data, baseline characteristics of participants will be recorded before assignment involving age, gender, body mass index, smoking, comorbidities, cardiopulmonary capacity, exercise ability, frailty status and quality of life, etc.

Sample size calculation

According to previous data,³³ the normal growth rate of sAAA with baseline diameter between 3.5 and 5.0 cm was approximately 1.9±1.4 mm/year. Our preliminary study revealed a mean growth rate of 1.2 mm/year in 10 patients with sAAA who received enhanced physical exercise intervention. Based on the Tukey’s g-and-h distribution of AAA growth rate, we adopted Mann-Whitney U test for means from two independent groups with 1000 computer simulations. Assuming the g of 0.4, a total of 146 patients (73 in each group) is needed to achieve a power of 0.906, allowing for a 10% attrition rate. The detailed simulation results are shown in online supplemental appendix 2.

Statistical analysis

The primary alternative hypothesis was the difference of growth rate of sAAA in the two arms within the equivalence margin. The equivalent limit was determined by the difference between test group mean and reference group mean. The secondary alternative hypothesis was that the multidimensional cardiovascular function in the enhanced physical exercise group was superior to that in the standard clinical care group. The superiority margin was set to be 5% of reference group mean. The AAA MOVE trial will perform both modified intention-to-treat (mITT) and per-protocol (PP) analysis, with mITT analysis as the main summary of primary and secondary outcomes, while PP analysis as the sensitivity analysis. Patients who quit the study unrelated to exercise or aneurysm will not be counted in the mITT population, otherwise, people who quit the trial due to intolerance of exercise programme or aneurysm-related cause will be still counted in the intervention group in mITT analysis, but considered in control group in PP analysis. If patients stop observation due to AAA progression (receive intervention or rupture) within the 12 months, the measured outcomes at the end point will be counted in the mITT analysis instead of PP analysis.

As for the comparison of primary outcome, Mann-Whitney U test is used, because AAA diameter meets the Tukey’s g-and-h distribution. Other continuous outcomes are compared by independent sample t-test if normally distributed. Dichotomous outcomes are compared by χ² test or Fisher’s exact test. Effect measures are presented as mean or OR with related 95% CI from generalised linear model. As for comparison of repeated measures, difference of outcome changes from baseline over time between groups are compared by generalised additive mixed model, presented as absolute marginal mean values with associated 95% CI. The interaction between repeated measure time and groups for each variable are reported as p values. Differences in the long-term clinical outcomes will be evaluated graphically using Kaplan-Meier curves and compared by log-rank test. Multivariate Cox proportional hazard regression analysis is used to assess adjusted HR and corresponding 95% CI for long-term outcomes. Potential confounders like age, gender, smoking cessation, major comorbidities and oral medications will be adjusted during the multivariate regression analysis. Missing data for covariates will be refilled by multiple imputation. The missing value interpolation is based on the distribution of other variables in the data, and the continuous iterative interpolation method is used to impute the missing value.

Prespecified subgroup analyses will be performed in the following populations: (1) female and male, (2) aged ≤65 years and >65 years, (3) current smokers, ex-smokers and non-smokers, (4) frail and non-frail patients, (5) body mass index (BMI) ≥25 kg/m² and BMI <25 kg/m².

Monitoring

The Data Monitoring Committee (DMC) will be in charge of the data review and interim analysis independent of the study team. When half of the participants have been randomly assigned and followed up for 12 months, the DMC will perform the interim analysis based on the primary and safety end points. Next, the DMC will decide whether to continue the trial or adjust the sample size according to the results of the interim analysis. The protocol of this trial is subject to potential amendments based on peer-review feedback. Additionally, adjustments to the details of MRI scanning may be made to accommodate updates in scanning sequences. Furthermore, the sample size could be modified in response to the interim analysis results. Adverse events, especially exercise-related injury and aneurysm events, will also be monitored by investigators every 3 months. Participants can also report adverse events to outcome assessors through online software WeChat at any time. Severe adverse events resulting in death, disability, permanent impairment and prolonged hospital stay will be reported promptly to the ethics committee. Details of all adverse events will be recorded by the investigators.

Patient and public involvement statement

Actually, the research question, whether physical exercise was safe in sAAA, was inspired by patients in the outpatient clinic. A considerable proportion of patients with sAAA had high demand in quality of life, and worried about various exercises might affect the growth rate of AAA. Furthermore, patients were inquired about their main focus and expectation during follow-up by questionaries during the study design stage of the trial, which were modified as patient-centred outcomes in our study, involving cardiopulmonary capacity, anthropometry, frailty, quality of life and clinical outcomes. The enhanced physical exercise intervention was also checked with patients with sAAA during preliminary experiments. As for the dissemination of our trial findings, posters will be exhibited in the outpatient clinic, and website link to trial findings will be spread among participants by WeChat.

Discussion

The present study describes the design and protocol of the AAA MOVE trial, an RCT that aims to evaluate the effect of enhanced physical exercise on the AAA progression, aortic flow dynamics, aneurysm sac wall and ventricular-aortic coupling of patients with sAAA by multimodality MRI. To the best of our knowledge, the AAA MOVE trial is the first RCT that investigates the multidimensional effect of enhanced physical exercise on the morphology, haemodynamics, vessel wall atherosclerosis and inflammation as well as cardiac function of patients with AAA, hoping to provide a state-of-the-art advice on the exercise prescription of patients with sAAA.

Lifestyle intervention and close surveillance is now considered as the main component of conservative management of sAAA before reaching threshold of surgery. Previous work confirmed that physical exercise can improve the cardiopulmonary capacity of patients with AAA,^{11 12} but few studies reported the changes of AAA diameter, let alone effect on other aspects of aorta and heart. Optimal lifestyle prescription of best physical exercise for patients with AAA should balance the benefit of cardiopulmonary function improvement and risk of aneurysm progression and rupture. Potential impacts on the upstream cardiac output, downstream aortic flow dynamics and local aortic wall may shed light on the uncovered mechanism of AAA progression. Thus, our study will carve out a multi-interdisciplinary way of exploring the natural history and progression of AAA under lifestyle intervention, with the assistance of multimodality MRI.

Progression of AAA is a complex multidimensional process, involving the following two essential elements: (1) haemodynamic impact of blood flow on the aortic wall and (2) strength and local vascular characteristics of aortic wall, involving metabolism, calcification, intraluminal thrombus and compliance. The role of blood flow haemodynamics in the AAA progression has been established for the long-term in the vascular field. From the view of macroscopic fluid haemodynamics, the progression of AAA can be actually considered as a biomechanical process which the mechanical stress within the aneurysmal wall exceeds the tensile strength of the tissue.³⁴ WSS, flow pattern, patient-specific pulsatile velocity and pressure boundary conditions play crucial roles in the process of AAA rupture. From a micro-hydrodynamics perspective, perturbed flow with low shear stress can expose the endothelial cells to higher shear stress gradients, which leads to intensive monocyte infiltration and lipid accumulation in the aortic wall.³⁵ Furthermore, constant disturbed flow can stimulate oxidative stress by accumulating redox-sensitive gene expression and losing compensatory antioxidant defenses in endothelial cells, which can finally result in autophagy and apoptosis.³⁶ Thus, quantification of flow haemodynamics by computational fluid dynamics or 4D flow MRI has been used as effective methods to capture the subtle changes of aneurysm and predict the AAA progression.

Apart from haemodynamic impact of blood flow, pathological changes of aortic wall, for instance, atherosclerosis, calcification and inflammation, also contributed to the progression of AAA. AAA is now considered a chronic inflammatory disease.³⁷ A recent systematic review suggested aneurysm wall inflammation and metabolism, assessed by ultra-small superparamagnetic iron oxide (USPIO) uptake, might predict AAA rupture.³⁸ However, current evidence only revealed a trend towards an association between USPIO uptake and AAA rupture without statistical significance.³⁸ Moreover, the USPIO contrast media has not been widely used in the clinics. By contrast, magnetic resonance vessel wall imaging, using 2D BB T1-weighted TSE/3D-T1-BB-VISTA sequence, is a promising non-invasive MRI technique for evaluating aortic wall disease, which can provide superior reproducibility for quantification of aortic wall characteristics and detect subtle vascular wall changes of atherosclerosis and inflammation.³⁹ Accordingly, attempt through multimodality MRI may serve as a good alternative for assessing the atherosclerosis and inflammation of aortic wall.

The development of pathological aortic wall degeneration is inevitably associated with the upstream cardiac output, which may act as the source of dynamic impact of high-pressure blood flow in the downstream abdominal aorta. Most researches focused on the effect of cardiac dynamic output on the progression of AAA, but few studies pay attention to the reverse impact of AAA progression on cardiac function. From a biomechanical view, the enlargement of downstream abdominal aorta can lead to perturbed blood flow with increasing energy loss and afterload of left ventricle,²⁷ hence reversely affecting the ventricular function and structure. The AAA MOVE trial aimed to investigate this bidirectional relationship between upstream cardiac function and downstream AAA progression, hoping to provide a more comprehensive perspective of the ventricular-aortic coupling in patients with AAA. The potential findings might influence current management strategies of cardiac issues in patients with AAA during surveillance.

Several limitations existed in this trial, the first being the difficulty of monitoring the exercise intensity of participants. As the intervention of enhanced physical exercise mainly take place in the community and last for 1 year, it is hard to continuously monitor the compliance to the exercise regimen. Regarding this issue, the investigators who are responsible for follow-up will trace the step numbers and daily calories of participants based on a smartphone online platform (WeChat), which can reflect the intensity of exercise among enrolled patients. Second, in common with most RCTs, patients who are willing to participate in the study tend to be more motivated than those who refuse. Besides, partially or totally dependent patients are excluded in our study, still representing a non-negligible proportion of patients with AAA. Proper exercise regimen regarding this population remains to be explored in the future.

AAA MOVE trial enrolled its first patient on 13 July 2023, and as of 15 August 15 2023 has enrolled 11 participants. Full study completion including 12-month surveillance is expected to occur by August 2026.

The AAA MOVE trial will evaluate the effect of enhanced physical exercise on sAAA progression during follow-up, from various dimensions by multimodality MRI, covering AAA growth rate, aortic flow haemodynamics, aneurysm sac wall and ventricular-aortic coupling. Combined with multimodality imaging and biomechanical analysis, this multidisciplinary study will hopefully provide the much needed evidence to best lifestyle management and might open new horizons to cardiac risk control in patients with AAA.

Ethics and dissemination

This study was approved by the Ethics Committee on Biomedical Research of West China Hospital (approval number: 2023-783) on 16 June 2023.

Main findings from the trial will be disseminated through presentations at conferences, peer-reviewed publications and directly pushed to smartphone of participants. Project datasets will be housed on the online platform created for the study, and all datasets will be password protected. Others will have access to trial data by request. To ensure confidentiality, data dispersed to project team members will be blinded of any identifying participant information.

Ethics statements

Patient consent for publication

Not applicable.