To establish the effect of exercise therapy in patients with intermittent claudication, and to identify outcome predictors for exercise training.

MEDLINE, Excerpta Medica, AMED, and the database of the Dutch National Institute of Allied Health Professions were searched using the terms provided; the search dates were unclear. A cross-reference search was conducted on the bibliography of each key review article and information was obtained from specialists in the field. Papers had to be published in English, German, French or Dutch to be included in the review.

Study designs of evaluations included in the review

Randomised controlled trials (RCTs) with untreated controls, including placebo drugs or other intervention treatments, were eligible. The treatment programmes lasted from 6 weeks to 6 months; details of the follow-up periods were not provided.

Specific interventions included in the review

The exercise programme interventions included walking only, 'physical training' or dynamic leg exercise, and treadmill training. The type, frequency, duration and intensity of exercise varied between studies. The intensity varied from moderate pain, to the point of pain, beyond pain and unknown. The control treatments comprised placebo drugs, no treatment, a combination of drugs and exercise therapy, surgery, drugs and percutaneous transluminal angioplasty.

Participants included in the review

The participants were patients with intermittent claudication, where the level of arterial disease included: no arteriography, atherosclerotic lesion below or above the inguinal ligament, or combined lesions, and not reported. Most trials studied men between the ages of 60 and 76 years. The mean age of participants ranged from 58 to 67 years, and the proportion of men was between 72 and 100%.

Outcomes assessed in the review

Walking capacity as assessed on a treadmill, although not all of the individual studies used the same outcome measure. Improved walking performance was assessed as the improvement in pain-free or maximum walking distance or walking time. The overall improvement in walking distance or walking time was either adopted from the articles, or calculated from the data or figures provided.

How were decisions on the relevance of primary studies made?

Eligible studies were subjected to a blinded qualitative assessment by two independent reviewers. To guard against assessor bias, the authors' names, the setting of the study, the name of the journal, the date of publication, and the reference list were blinded.

A list of methodological criteria was developed based on the generally accepted principles of intervention research. The criteria referred to various aspects of study population, description of interventions, outcome measures, and data presentation and analysis. The criteria were proposed by Chalmers et al. (see Other Publications of Related Interest no.1) and modified by Bouter (see Other Publications of Related Interest no.2). Criteria specific to the study population were adopted. A weight was attached to each criterion, resulting in a maximum score of 100 points for each study. RCTs were considered to be of good quality if the methodological score was at least 60 points.The studies were rated independently by two reviewers, and any disagreements were resolved by consensus or by consulting a third researcher who acted as a referee.

The authors do not state how the data were extracted for the review, or how many of the authors performed the data extraction.

How were the studies combined?

The studies were combined narratively due to the general low methodological quality of the trials, and the heterogeneity of the the study groups, outcome measures, follow-up time and (reference) treatments.

How were differences between studies investigated?

The authors tested for heterogeneity but they did not state which specific test was used.

Ten RCTs (conducted between 1966 and 1996) with a total of 291 participants were included in the analysis. Most of the studies had a small sample size. Only one study had 25 patients enrolled, the remaining studies had less than 20.

Seven RCTs had a methodological score of at least 60 points out of a maximum of 100, and were considered to be of good quality. The median score was 61 and the range was 47 to 75 (mean 62.5, standard deviation 8.5).

The improvement in pain-free or maximum walking distance or time ranged from 28 to 210% (mean 105, standard deviation 55.8). All studies showed the benefit of exercise therapy on walking capacity in patients with intermittent claudication.

Only one study evaluated outcome predictors for exercise therapy. In this study, the possible effects of exercise therapy on walking performance in patients who had reconstructive vascular surgery were investigated. Age, gender, history of myocardial ischaemic disease, diabetes and level of stenosis were not significantly correlated to increases in walking distance.

All studies reported a positive effect of exercise therapy on walking in patients with intermittent claudication. However, from the trials studied in the current systematic review, it became clear that an optimal exercise programme for intermittent claudication does not exist. Only general recommendations can be given based on the current studies.

No predictive factors were clearly identified.

This was a well-conducted review with a comprehensive review question and clear inclusion criteria.

Sufficient details of the individual studies were presented.

The validity of included studies was adequately assessed, although the authors did not appear to exclude studies that were not of good quality, i.e. those scoring below 60 on the 100-point validity assessment scale.

The literature search was relatively comprehensive, although the time period that the searches covered was not stated.

The sources of heterogeneity could have been investigated. The primary studies were summarised appropriately.

The results should be viewed with caution due to the small sample sizes and inclusion of studies of low methodological quality.

Due to the limitations of the current study, more trials with larger sample sizes should be conducted. The authors state that future research should focus on the following questions.

What is the optimal exercise therapy (frequency, type, mode, intensity and duration of non-supervised or supervised programmes)?

Will an improved performance translate into improved functional status, a reduction in cardiovascular morbidity and mortality and, eventually, result in a decreased number of interventions?

Are there any factors that predict the outcome of exercise therapy?

The authors also suggest that better defined guidelines are needed for exercise training of high-risk patients, such as those with angina pectoris. Prospective cost-effectiveness studies should be conducted that evaluate supervised vascular rehabilitation programmes with regard to improvements in functional capacity, modifications of risk factors, long-term compliance, quality of life, and medical costs incurred.

Netherlands Heart Foundation, grant number 45.015.

1. Chalmers TC, Smith H, Blackburn B, Silverman B, Schroeder B, Reitman D, et al. A method for assessing the quality of a randomized control trial. Control Clin Trials 1981;2:31-49. 2. Bouter LM. Meta-analysis: controleerbaar en reproduceerbaar literatuuronderzoek als basis voor rationele beslissingen in de gezondheidszorg. Amsterdam: Amsterdam University Press; 1994.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.