High Intensity Interval Training In pATiEnts With Intermittent Claudication

This INITIATE study evaluates the use of high-intensity interval training as a treatment modality for patients with intermittent claudication - an ambulatory leg pain caused by narrowed arteries that supply the lower limbs.

It is an observational cohort study considering high-intensity interval training (HIIT) as a treatment for intermittent claudication, consisting of two workstreams. Workstream 1: an initial observational cohort study to consider the feasibility of the intervention and exclusion criteria. Workstream 2: a proof of concept study utilising the altered intervention and exclusion criteria following recommendations highlighted during workstream 1.

Patients with peripheral vascular disease (PVD) may develop a reproducible pain in their legs when they walk, which usually subsides with rest. This is known as intermittent claudication (IC) and is caused by a reduced blood supply to the legs as a result of narrowed or hardened arteries that supply the lower limbs. This ambulatory pain impedes on activities of daily living, functional capacity and quality of life.

National Institute for Health and Care Excellence (NICE) clinical guidance recommends a 12-week supervised exercise programme as first-line treatment for IC, whereby patients are encouraged to walk to the point of maximal pain. Robust clinical trials have demonstrated that supervised exercise programmes are efficacious for improving both pain-free and maximal walking distances, whilst also potentially improving quality of life.

Despite this, supervised exercise programmes are vastly under-utilised and not always available to consultant vascular surgeons. This means that further programmes need to be developed in order to provide a range of options to patients to improve uptake and adherence rates. One such programme is a 6-week high-intensity interval training programme.

An initial observational cohort study of the 6 week HIIT programme will be conducted to determine to determine the feasibility of the intervention and inclusion criteria. The results from this will be used to make any necessary changes to the HIIT intervention before moving into a proof of concept study, considering the utility, safety, acceptability and potential clinical efficacy of this programme.

Eligibility Criteria:
Workstream 1

Inclusion criteria:

* Aged \>18 years
* Ankle-brachial pressure index (ABPI) \<0.9 at rest or a systolic pressure drop of ≥20mmHg at the ankle after exercise testing
* Ability to walk unaided
* English speaking and able to comply with exercise instructions

Exclusion criteria:

* Unable to provide informed consent
* Critical limb threatening ischaemia / rest pain / tissue loss
* Active cancer treatment
* Significant comorbidities precluding safe participation in exercise testing and / or training according to the American College of Sports Medicine (ACSM) guidelines (28)
* Resting/uncontrolled tachycardia (\>100 beats per minute \[bpm\]) and/or resting/uncontrolled hypertension (systolic blood pressure \>180 millimetres of mercury \[mmHg\] or diastolic blood pressure \>100mmHg)
* Symptomatic hypotension

Additional exclusion criteria:

Following baseline cardiopulmonary exercise test (CPET), patients will be withdrawn and prevented from continuing their involvement in the study if there is any evidence of:

* Exercise-induced myocardial ischaemia or significant haemodynamic compromise (manifesting as anginal symptoms, significant ECG changes or an abnormal blood pressure response).
* An inability to complete a maximal effort CPET

Workstream 2:

Inclusion criteria:

* Aged \>18 years
* ABPI \<0.9 at rest or a systolic pressure drop of ≥20mmHg at the ankle after exercise testing
* Ability to walk unaided
* English speaking and able to comply with exercise instructions

Exclusion criteria:

* Unable to provide informed consent
* Critical limb threatening ischaemia / rest pain / tissue loss
* Active cancer treatment
* Significant comorbidities precluding safe participation in exercise testing and / or training according to the American College of Sports Medicine (ACSM) guidelines (28)
* Resting/uncontrolled tachycardia (\>100bpm) and/or resting/uncontrolled hypertension (systolic blood pressure \>180mmHg or diastolic blood pressure \>100mmHg)
* Symptomatic hypotension

Additional exclusion criteria:

Following baseline CPET, patients will be withdrawn and prevented from continuing their involvement in the study if there is any evidence of:

● Exercise-induced myocardial ischaemia or significant haemodynamic compromise (manifesting as anginal symptoms, significant ECG changes or an abnormal blood pressure response).