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Exercise training and heart failure: a systematic review of current evidence |
Lloyd-Williams F, Mair F S, Leitner M |
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Authors' objectives To investigate the effects of exercise training upon chronic heart failure patients.
Searching The following electronic databases were searched from 1966 up to December 2000: MEDLINE, the Science Citation Index, the Social Sciences Citation Index, databases via BIDS, Bandolier, the Cochrane Database of Systematic Reviews, the National Research Register, and Current Research in Britain. The search terms used were 'exercise training', 'physical training', 'aerobic', 'anaerobic', 'heart failure', 'left ventricular failure' and 'cardiac failure'. Latest editions of key relevant journals not yet available on electronic databases were also scrutinised. These included the European Heart Journal, American Heart Journal, Journal of the American College of Cardiology, the American Journal of Medicine, JAMA, BMJ, Heart, Circulation, Circulation Research and Hypertension. The reference lists of identified articles were also examined for further studies. Studies reported in languages other than English were excluded.
Study selection Study designs of evaluations included in the reviewAll designs of clinical trial were eligible. The included studies were randomised controlled trials (RCTs), randomised crossover trials, non-randomised clinical studies, and pre-test post-test studies. The authors state that all published trials were included due to the limited number of relevant studies.
Specific interventions included in the reviewStudies of exercise training were eligible for inclusion. In the included studies, this was mostly supervised, hospital-based and short-term. The majority of studies used either a cycle ergometer or combined exercise programmes (such as cycle ergometer, walking, jogging, swimming or circuit training). Other activities included calisthenics, ball games, resistance exercises and step exercises. Five studies focused on anaerobic training (knee-extensor or leg muscle training), and two on a walking programme. Seven studies provided patients with cycle ergometers or treadmills for use in their own homes over a short time-period. Exercise frequency ranged from 1 to 7 times per week, and each session lasted 10 to 60 minutes. The duration of the intervention ranged from 4 to 52 weeks. The treatment of control groups was not described.
Participants included in the reviewPatients with chronic heart failure were eligible for inclusion. In the included studies, the mean age of the patients ranged from 50 to 82 years, and was below 65 years in 74% of the studies. Ten studies included males only, with only one study focusing exclusively on females. The remaining studies had a preponderance of men.
Outcomes assessed in the reviewThe outcomes assessed were improvements in physical performance (e.g. increased peak oxygen uptake, cardiac output, aerobic capacity), quality of life, health care service utilisation, cost-effectiveness and mortality. Research studies were excluded if their main outcome measures were the effects of drugs upon the physical performance of patients with heart failure, and the biomedical changes in patients with heart failure as a result of exercise training.
How were decisions on the relevance of primary studies made?Two reviewers assessed study eligibility by reading the titles and/or abstracts identified by the searches.
Assessment of study quality The methodological quality of the RCTs was scored using the scale of Jadad et al. (see Other Publications of Related Interest). The authors do not report a method for assessing the validity of other study designs, although they do state that data were extracted concerning methodological approaches and any other factors that could affect the validity of the results, including effect modifiers. The RCTs were assessed independently by two reviewers. Any disagreements were resolved by consensus.
Data extraction The data were extracted independently by two reviewers. The details recorded included: bibliographic details, aims, study population, setting, patient selection criteria, information concerning the type of training provided, measurement tools used, outcome measures, study findings and conclusions. Data were also recorded on the number of patients, compliance and completion rates, methodological approaches, and the validity of the findings.
Methods of synthesis How were the studies combined?A narrative synthesis was undertaken.
How were differences between studies investigated?Differences between the studies were not formally investigated. The results were not presented according to the study design, exercise type, intensity or other defining characteristic. Some differences between the studies, in terms of study design, sample size, mean age, gender, types of exercise, duration and frequency of exercise, intensity of exercise, duration of exercise programme and training result (either positive or inconclusive), were tabulated and discussed in the text.
Results of the review Thirty-one studies were included. Of these, 14 were prospective RCTs, 8 were randomised crossover trials, 2 were non-RCTs and 7 were pre-test post-test studies. The total number of participants was 1010: 716 in prospective RCTs, 164 in randomised crossover trials, 73 in pre-test post-test studies, and 57 in non-RCTs.
Most of the primary studies were small: 65% had 25 participants or fewer. Most of the RCTs did not report their recruitment procedures and methods of randomisation clearly. The reported completion and compliance rates were fairly high. Fifteen of the studies cited completion rates of between 90 and 100%, while 12 studies reported over 80% compliance. No studies attempted to assess the acceptability of the exercise programmes prescribed. The patients included were often convenience samples, much younger than the broader population of patients with heart failure, and many studies excluded patients with common co-morbidities such as diabetes or chronic obstructive airways disease. Generalisability of the findings is therefore uncertain.
The majority of the studies considered physiological outcome measures such as oxygen uptake, resting heart rate, sub-maximal heart rate, systolic blood-pressure and ventilation. These studies mostly found a positive training effect. However, few studies followed-up their patients in the medium to longer term to see if these benefits were maintained; 45% of the training programmes lasted 8 weeks or less, and only 2 studies lasted for one year. Eleven of the 16 studies that measured quality of life outcomes reported a beneficial effect, but again, the majority of the studies were short-term. Only 4 studies considered the relationship between physiological outcomes and quality of life. Only one study considered health care utilisation and mortality. This study found a beneficial effect on mortality and hospital readmission rates. Two studies specifically examined exercise among older age groups (mean ages 70 and 81 years); both suggested that physical exercise was safe and beneficial but the studies were small and short-term.
Authors' conclusions Short-term physical exercise training in selected subgroups of patients with heart failure has physiological benefits and positive effects on quality of life. This review highlights the continuing problem of clinical trials that include participants who are not representative of the general population of heart failure patients seen in primary care. Further investigation of the utility and applicability of exercise training is essential.
CRD commentary The review question is clearly defined and important, although the inclusion and exclusion criteria and definition of chronic heart failure are not presented. The search involved a number of electronic databases, as well as the handsearching of key journals and the cross-checking of reference lists from retrieved articles. However, some key terms were missed or have not been reported, and non-English language studies were excluded.
The primary studies were reasonably well described (table 1), although the training effects were summarised merely as 'positive' or 'inconclusive'. Some measure of the size of effect, such as the mean reduction in systolic blood-pressure or resting heart rate for physiological variables, would have been more helpful in determining the potential scale of benefit. The authors also reported the compliance and completion rates without describing how these were measured in the primary studies, or assessing the quality of such measurements. The methodological quality of the primary studies was varied since all the studies identified were included, regardless of rigour. The authors scored the RCTs using a validated scoring system, but neither used these scores in a sensitivity analysis or even reported them in the results. No attempt was made to distinguish between evidence from non-RCTs and other studies, or to present results according to the quality of the evidence. There were some discrepancies in the number of included studies reported by study design in the text and in table 1, indicating a lack of precision in classifying study design.
The narrative pooling of two findings relating to outcome measures was disappointingly superficial. It was not completely clear from the review as presented why data for certain outcome measures, particularly oxygen uptake, could not have been pooled by study design.
The authors' conclusions, being very general, are supported by the review.
Implications of the review for practice and research Practice: The authors state 'At present there remains a paucity of high-quality evidence to support the further development of guidelines for health care providers or patients regarding the subject of exercise and heart failure'.
Research: The authors state 'Larger, long-term trials are required which represent all heart failure patient groups in terms of age, sex, common co-morbidities and location'.
Funding National Health Service Executive North West-funded Cardiovascular Collaborative Group.
Bibliographic details Lloyd-Williams F, Mair F S, Leitner M. Exercise training and heart failure: a systematic review of current evidence. British Journal of General Practice 2002; 52: 47-55 Other publications of related interest Jadad AR, Moore RA, Carroll D, Jenkinson C, Reynolds DJ, Gavaghan DJ, et al. Assessing the quality of reports of randomized clinical trials: is blinding necessary? Control Clin Trials 1996;17:1-12.
Indexing Status Subject indexing assigned by NLM MeSH Adult; Aged; Aged, 80 and over; Chronic Disease; Cross-Over Studies; Exercise Therapy /methods; Female; Heart Failure /rehabilitation; Humans; Male; Middle Aged; Physical Endurance /physiology; Quality of Life; Randomized Controlled Trials as Topic; Treatment Outcome AccessionNumber 12002008021 Date bibliographic record published 31/03/2003 Date abstract record published 31/03/2003 Record Status 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. |
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