Neuromuscular electrical stimulation as an adjunct to standard care in improving walking distances in intermittent claudication patients: the NESIC RCT
Authors: Burgess Laura , Smith Sasha , Babber Adarsh , Shalhoub Joseph , Fiorentino Francesca , de la Rosa Consuelo Nohpal , Klimowska-Nassar Natalia , Epstein David M , Pérez Troncoso Daniel , Braithwaite Bruce , Chetter Ian , Coulston James , Gohel Manjit , Hinchliffe Robert , Stansby Gerard , Davies Alun H 
Published: September 2023

Background
Peripheral arterial disease is common and associated with increased cardiovascular morbidity and mortality. While patients with peripheral arterial disease are known to benefit from supervised exercise therapy, it is not always available. Neuromuscular electrical stimulation devices may offer a similar benefit. A randomised controlled trial was required to ascertain whether such devices can benefit patients who receive supervised exercise therapy and those who do not.

Objective(s)
The primary objective was to assess the mean difference in absolute walking distance at 3 months in intermittent claudication patients receiving either a neuromuscular electrical stimulation device and local standard care (intervention), or local standard care alone (control).

Design
A pragmatic, multicentre, randomised controlled trial stratified by centre.

Setting
Secondary-care National Health Service hospitals in the United Kingdom.

Participants
Patients aged ≥18 years, with a diagnosis of intermittent claudication according to the Edinburgh Claudication Questionnaire and ankle–brachial pressure index (or stress test), without contraindications to neuromuscular electrical stimulation were deemed eligible to partake.

Interventions
Participants were randomised 1 : 1 to either local standard care or local standard care and neuromuscular electrical stimulation. Due to the nature of the intervention, it was unfeasible to blind the research nurse or participant to the study allocation.

Main outcome measures
The primary outcome measure was absolute walking distance measured by treadmill testing at 3 months. Secondary outcomes included change in initial claudication distance, quality of life, compliance with interventions and haemodynamic assessments.

Results
Two hundred patients underwent randomisation, with 160 patients having analysable primary outcome data for the intention-to-treat analysis intervention (n = 80); control (n = 80). As the data were right-censored, a Tobit regression model was used to analyse the primary outcome, utilising the square root of the absolute walking distance to accommodate the skewed data. However, as this made the data difficult to interpret, a Tobit regression model using raw absolute walking distance data was used as well. Neuromuscular electrical stimulation improved the difference in absolute walking distance at 3 months but this was not statistically significant (square root of absolute walking distance: 0.835 units, 95% confidence interval −0.67 to 2.34 units; p = 0.28/absolute walking distance raw data: 27.18 m, 95% confidence interval −26.92 to 81.28 m; p = 0.323). Supervised exercise therapy participants showed a markedly improved absolute walking distance compared with patients receiving best medical therapy only at 3 months (square root of absolute walking distance: 3.295 units 95% confidence interval 1.77 to 4.82; p < 0.001/absolute walking distance raw data: 121.71 m, 95% confidence interval 67.32 to 176.10; p ≤ 0.001). Neuromuscular electrical stimulation significantly improved absolute walking distance at 3 months for mild claudicants (square root of absolute walking distance: 2.877 units, 95% confidence interval 0.51 to 5.25; p = 0.019/absolute walking distance raw data: 120.55 m, 95% confidence interval 16.03 to 225.06; p = 0.03) compared to the control arm. This was an unplanned (post hoc) analysis.
There were no clear differences in mechanistic measurements between the two treatment groups over the follow-up period.
Serious adverse events were evenly reported between the two groups; all being classified as either not related or unlikely to be related to the study device.

Limitations
Absolute walking distance was used as the primary outcome measure; there was a large range of baseline distances in both groups with right-skewed distribution. We did not stratify by baseline absolute walking distance for the primary outcome analysis. Additionally, only 160 patients had analysable primary outcome data due to missing treadmill data.

Conclusions
Supervised exercise therapy is an effective treatment for intermittent claudication. Neuromuscular electrical stimulation appears to be beneficial as an adjunct to supervised exercise therapy and on its own in mild claudicants.

Future work
Further studies are needed to confirm the effectiveness of neuromuscular electrical stimulation in combination with supervised exercise therapy, and in mild to moderate claudicants in a larger sample size.

Study registration
This trial is registered as ISRCTN18242823.

Funding
This project was funded by the Efficacy and Mechanism Evaluation (EME) Programme, a Medical Research Council (MRC) and National Institute for Health and Care Research (NIHR) partnership (project number 15/180/68). This will be published in full in Efficacy and Mechanism Evaluation; Vol. 10, No. 2. See the NIHR Journals Library website for further project information.
Infrastructure support for this research was provided by the NIHR Imperial Biomedical Research Centre (BRC) (with others, e.g. NIHR Imperial CRF, Imperial College ECMC, NIHR Imperial PSTRC, NIHR London MIC, etc.).