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Cardiac rehabilitation (CR) has been defined as: ‘the coordinated sum of activities required to influence favourably the underlying cause of cardiovascular disease, as well as to provide the best possible physical, mental and social conditions, so that the patients may, by their own efforts, preserve or resume optimal functioning in their community and through improved health behaviour, slow or reverse progression of disease’.1
While exercise training is a cornerstone of CR, it is recommended that ‘comprehensive’ programmes also include education (eg, provision of information about a healthy lifestyle) and psychological intervention (eg, counselling to reduce stress).
The first systematic reviews and meta-analyses of CR were published more than 20 years ago, and reported a 20%–25% reduction in all-cause and cardiovascular mortality, pooling data from up to 22 randomised trials, comparing exercise-based CR and no-exercise control in over 4300 patients with postmyocardial infarction. In 2001, Jolliffe et al2 published the first Cochrane review of exercise-based CR, including 32 randomised controlled trials (RCTs) in 8440 patients with postmyocardial infarction and revascularisation. Since then, a further five Cochrane reviews of CR have been published—exercise-based rehabilitation for heart failure, home-based versus centre-based CR, psychological interventions for coronary heart disease, patient education in the management of coronary heart disease and promoting patient uptake and adherence in CR. The portfolio of Cochrane CR review remains dynamic with the publication of regular review updates.
The development of this portfolio of Cochrane reviews reflects many of the key areas of evolution in the model provision of CR, and how this model can vary across international healthcare jurisdictions. These include the shift from exercise training alone to comprehensive secondary prevention, including risk factor and dietary education and management of psychological factors; the broadening of the population of patients receiving CR services, including those with heart failure; and the development of alternative settings of CR delivery, including home provision alongside to the traditional supervised hospital-based or centre-based programmes and the need to focus the outcomes of CR to inform the needs of healthcare policy-makers (eg, rates of hospital admission, health-related quality of life and economic considerations).
Overviews are a relatively new approach to summarising evidence and synthesising results from multiple systematic reviews into a single document. By providing a single synthesis of all relevant evidence in a particular area, overviews are particularly useful for clinical and policy decision-making, providing a comprehensive ‘friendly front end’ to the evidence. Overviews can also help inform the strategic direction of conduct and structuring of future systematic reviews and also provide an opportunity to identify potential ‘evidence gaps’ informing areas in which new Cochrane reviews should be prioritised.
An overview was undertaken to provide a contemporary review of the evidence for CR3 (see table 1). The overview included six Cochrane reviews across 148 RCTs in 97 486 participants. Based on assessment using the R-AMSTAR tool, the six systematic reviews scored 35–41 (maximum score 44), and were, therefore, deemed of high methodological quality. The findings of the overview are summarised in table 2 in the format of GRADE summary of evidence table for each of the reviews. In brief, the overview findings are summarised as follows: compared with usual care alone (no exercise intervention), exercise-based CR reduces hospital admissions and improves participant health-related quality of life in those with low-to-moderate risk heart failure and coronary heart disease. At 12 months’ or more follow-up, there was evidence of some reduction in mortality in people with coronary heart disease; psychological-based and education-based interventions appear to have little impact on mortality or morbidity, but may improve health-related quality of life of those with coronary heart disease; home-based and centre-based programmes are equally effective in improving quality of life and have similar costs; and selected interventions can increase the uptake of CR programmes, but evidence to support interventions that improve adherence is weak.
PICO summary
Anderson and Taylor Cochrane CR overview3—GRADE summary of evidence
Study limitations
The first limitation of this overview was that due to the heterogeneity of populations, interventions and outcomes in the included Cochrane reviews, it was not considered appropriate to undertake a network meta-analysis. In other words, to use the randomised trials identified by this overview in order to make indirect comparisons either across systematic reviews interventions (eg, to assess the relative effectiveness of exercise-training vs education interventions) or across systematic review populations (eg, to assess the relative effectiveness of exercise-based CR in patients with postmyocardial infarction and revascularisation vs patients with heart failure).
The second limitation was that the quality of the primary trials in the included systematic reviews was variable. The main sources of bias were inadequate reporting of allocation concealment and randomisation methods and lack of outcome blinding. Another potential source of inconsistency was differential use of outcome data by the trials, that is, some reported only postinterventional data, while others reported pre–post change.
Finally, this overview included randomised trials conducted over a wide period of time (1974–2013). During this time, there have been major advances in medical management, such as the increased use of statins since the mid-1990s. Indeed, it has been hypothesised that major advances in post-MI medical management since the mid-2000s have led to a reduction in the incremental effect on mortality of CR compared with usual care alone.4
Implications
The evidence compiled by this overview supports current international clinical guidelines that state that the addition of CR to medical management is effective (improving health-related quality of life and reducing the risk of future hospitalisations) and safe (with no increase in short-term mortality), compared with a no-exercise training control for clinically stable participants following myocardial infarction or percutaneous coronary intervention or who have heart failure.
This overview also highlights several potential areas for consideration in future research—systematic reviews and randomised trials. CR is a complex intervention with heterogeneity in interventions (content and methods of delivery) and the population of people who receive it. Future reviews of CR need to explore this complexity using approaches that include stratification (‘splitting’) of outcome results by patient indication (eg, postmyocardial infarction vs post-percutaneous coronary intervention) or intervention type (ie, exercise training only vs comprehensive CR interventions), reporting within trial subgroup analyses and use of meta-regression to explore the association between intervention characteristics and outcomes across trials. Consideration should also be given to the appropriate use of indirect comparison/mixed treatment methods in reviews or broadening the inclusion criteria of reviews to include active comparator arms of trials that would allow assessment of the comparative effectiveness of different CR interventions (or both). Theory-based approaches to systematic reviews of CR are also needed.5
Future trials of CR need to include patients at higher risk who are older, female and from a broader range of ethnicities and socioeconomic groups. Reporting of trial methods should be improved (eg, details of the process of randomisation and outcome blinding), and consistency is needed in the collection and reporting of outcome measures, including the use of validated quality-of-life measures, cardiac-related events, readmissions and costs. Finally, future trials need to better ‘open the black box’ of CR.5 In other words, to determine the incremental benefits of the various components of CR, future trials to provide more precise descriptions of their CR interventions are required, so that these comparisons can be more explicitly and reliably undertaken in future systematic reviews. This would also be aided by ‘head-to-head’ trials of different combinations of CR interventions (eg, an ‘exercise only’ CR intervention vs ‘exercise plus’ CR intervention).
Footnotes
Contributors RST drafted the manuscript. LJA revised the manuscript for its intellectual content. Both authors contributed substantially to this manuscript and have approved its final version.
Competing interests RST was a coauthor on five of the six Cochrane reviews included in the overview and is the Chief Investigator on an ongoing National Institute of Health Research Programme Grants for Applied Research (RP-PG-1210-12004): Rehabilitation Enablement in Chronic Heart Failure (REACH-HF).
Provenance and peer review Commissioned; internally peer reviewed.