The Contribution of Individual Exercise Training Components to Clinical Outcomes in Randomised Controlled Trials of Cardiac Rehabilitation: A Systematic Review and Meta-regression

Abstract

BackgroundWhile the clinical benefits of exercise-based cardiac rehabilitation are well established, there is extensive variation in the interventions used within these trials. It is unknown whether variations in individual components of these exercise interventions provide different relative contributions to overall clinical outcomes. This study aims to systematically examine the relationship between individual components of the exercise intervention in cardiac rehabilitation (such as intensity and frequency) and clinical outcomes for people with coronary heart disease.MethodsIn this systematic review, eligible trials were identified via searches of databases (PubMed, Allied and Complementary Medicine, EMBASE, PEDro, Science Citation Index Expanded, CINAHL, The Cochrane Library, SPORTDiscus) from citation tracking and hand-searching. Studies were included if they were randomised trials of a structured exercise intervention (versus usual care) for participants with coronary heart disease and reported at least one of cardiovascular mortality, total mortality, myocardial infarction or revascularisation outcomes. Each included trial was assessed using the Cochrane Risk of Bias Tool. Authors were also contacted for missing intervention details or data. Random effects meta-analysis was performed to calculate a summary risk ratio (RR) with 95% confidence interval (CI) for the effect of exercise on outcomes. Random effects meta-regression and subgroup analyses were conducted to examine the association between pre-specified co-variates (exercise components or trial characteristics) and each clinical outcome.ResultsSixty-nine trials were included, evaluating 72 interventions which differed markedly in terms of exercise components. Exercise-based cardiac rehabilitation was effective in reducing cardiovascular mortality (RR 0.74, 95% CI 0.65 to 0.86), total mortality (RR 0.90, 95% CI 0.83 to 0.99) and myocardial infarction (RR 0.80, 95% CI 0.70 to 0.92). This effect generally demonstrated no significant differences across subgroups of patients who received various types of usual care, more or less than 150 min of exercise per week and of differing cardiac aetiologies. There was however some heterogeneity observed in the efficacy of cardiac rehabilitation in reducing total mortality based on the presence of lipid lowering therapy (I 2 = 48%, p = 0.15 for subgroup treatment interaction effect). No single exercise component was identified through meta-regression as a significant predictor of mortality outcomes, although reductions in both total (RR 0.81, p = 0.042) and cardiovascular mortality (RR 0.72, p = 0.045) were observed in trials which reported high levels of participant exercise adherence, versus those which reported lower levels. A dose-response relationship was found between an increasing exercise session time and increasing risk of myocardial infarction (RR 1.01, p = 0.011) and the highest intensity of exercise prescribed and an increasing risk of percutaneous coronary intervention (RR 1.05, p = 0.047).ConclusionsE...

Physical Activity in the Prevention and Treatment of Coronary Artery Disease

“…Abell et al recently reviewed the contribution of individual exercise training components to clinical outcomes in randomized trials of cardiac rehabilitation and identified adherence to exercise prescription, not exercise intensity, session duration, or frequency, as a predictor of mortality 119. This result was also found in a long‐term analysis of 435 cardiac rehabilitation participants in Leeds, UK 122.…”

“…In patients with heart failure, serious adverse events were numerically higher with HIT than with MCT. This finding and the association of myocardial infarction, need for coronary intervention, and mortality in patients with CAD with exercise session duration or intensity, even though these findings are controversial, should receive attention in future trials 17, 18, 77, 119…”

“…This finding and the association of myocardial infarction, need for coronary intervention, and mortality in patients with CAD with exercise session duration or intensity, even though these findings are controversial, should receive attention in future trials. 17,18,77,119 Nevertheless, the most efficient exercise type, frequency, intensity, session duration (these parameters can be summarized as volume [eg, in metabolic equivalent hours per week]), and program duration are still unknown because the exercise prescriptions used in clinical trials were heterogeneous. The vast number of possible combinations makes absolute recommendations difficult to mandate in every situation.…”

“…130 As outlined previously, it is of prognostic relevance to achieve long-term participation in regular exercise and risk factor control. 119,122 The ongoing IPP (Intensive Intervention Program) trial evaluates the impact of a study nurse-coordinated prevention program consisting of structured education sessions in combination with regular telephone calls and telemetric care on risk factor control during 1 year of follow-up in patients after acute myocardial infarction (URL: http://www.clinicaltrials.gov. Unique identifier: NCT01896765).…”

Early moderate exercise benefits myocardial infarction healing via improvement of inflammation and ventricular remodelling in rats

“…Recent research has revealed that post-MI exercise training is associated with reductions in mortality and reinfarction; therefore, exercise training rather than the traditional instructions to avoid physical activity should be a part of cardiac rehabilitation programmes for MI. 39,40 However, the timing of the exercise training after MI has not yet been optimized. It has been revealed that moderate exercise beginning 5-7 days after MI is safe.…”