Efficacy of Exercise-Based Cardiac Rehabilitation Post-MI
Background Exercise-based cardiac rehabilitation (CR) remains an underused tool for secondary prevention post–myocardial infarction (MI). In part, this arises from uncertainty regarding the efficacy of CR, particularly with respect to reinfarction, where previous studies have failed to show consistent benefit. We therefore undertook a meta-analysis of randomized controlled trials (RCTs) to (1) estimate the effect of CR on cardiovascular outcomes and (2) examine the effect of CR program characteristics on the magnitude of CR benefits.
Methods We systematically searched MEDLINE as well as relevant bibliographies to identify all English-language RCTs examining the effects of exercise-based CR among post-MI patients. Data were aggregated using random-effects models. Stratified analyses were conducted to examine the impact of RCT-level characteristics on treatment benefits.
Results We identified 34 RCTs (N = 6,111). Overall, patients randomized to exercise-based CR had a lower risk of reinfarction (odds ratio [OR] 0.53, 95% CI 0.38–0.76), cardiac mortality (OR 0.64, 95% CI 0.46–0.88), and all-cause mortality (OR 0.74, 95% CI 0.58–0.95). In stratified analyses, treatment effects were consistent regardless of study periods, duration of CR, or time beyond the active intervention. Exercise-based CR had favorable effects on cardiovascular risk factors, including smoking, blood pressure, body weight, and lipid profile.
Conclusions Exercise-based CR is associated with reductions in mortality and reinfarction post-MI. Our secondary analyses suggest that even shorter CR programs may translate into improved long-term outcomes, although these results need to be confirmed in an RCT.
Despite guidelines recommending the use of cardiac rehabilitation (CR) programs for patients with ST-segment elevation myocardial infarction (MI) and non–ST-segment elevation MI/unstable angina, participation in these programs continues to be low; only 10% to 20% of patients who survive an acute MI participate in an exercise-based secondary prevention CR program. The reason for such low participation is likely multifactorial, but 1 important obstacle is the infrastructure to support prolonged participation in these programs. Another barrier to usage is likely the absence of large randomized controlled trials (RCTs) evaluating its efficacy and insufficient data on what features of CR programs result in the greatest efficacy.
Individual RCTs studying the efficacy of exercise-based CR have provided conflicting results, and the most recent meta-analysis (published in 2004) found that CR decreased all-cause and cardiac mortality but had no beneficial effects on reinfarction. In addition, considerable heterogeneity among programs exists, and the factors that define "effective" CR on a program-level—including optimal duration — are currently unclear. Given these areas of uncertainty, we undertook a meta-analysis of RCTs to (1) accurately estimate the effect of CR on cardiovascular outcomes and (2) conduct stratified analyses to examine the effect of RCT-level characteristics on the benefits of CR.
Abstract and Introduction
Abstract
Background Exercise-based cardiac rehabilitation (CR) remains an underused tool for secondary prevention post–myocardial infarction (MI). In part, this arises from uncertainty regarding the efficacy of CR, particularly with respect to reinfarction, where previous studies have failed to show consistent benefit. We therefore undertook a meta-analysis of randomized controlled trials (RCTs) to (1) estimate the effect of CR on cardiovascular outcomes and (2) examine the effect of CR program characteristics on the magnitude of CR benefits.
Methods We systematically searched MEDLINE as well as relevant bibliographies to identify all English-language RCTs examining the effects of exercise-based CR among post-MI patients. Data were aggregated using random-effects models. Stratified analyses were conducted to examine the impact of RCT-level characteristics on treatment benefits.
Results We identified 34 RCTs (N = 6,111). Overall, patients randomized to exercise-based CR had a lower risk of reinfarction (odds ratio [OR] 0.53, 95% CI 0.38–0.76), cardiac mortality (OR 0.64, 95% CI 0.46–0.88), and all-cause mortality (OR 0.74, 95% CI 0.58–0.95). In stratified analyses, treatment effects were consistent regardless of study periods, duration of CR, or time beyond the active intervention. Exercise-based CR had favorable effects on cardiovascular risk factors, including smoking, blood pressure, body weight, and lipid profile.
Conclusions Exercise-based CR is associated with reductions in mortality and reinfarction post-MI. Our secondary analyses suggest that even shorter CR programs may translate into improved long-term outcomes, although these results need to be confirmed in an RCT.
Introduction
Despite guidelines recommending the use of cardiac rehabilitation (CR) programs for patients with ST-segment elevation myocardial infarction (MI) and non–ST-segment elevation MI/unstable angina, participation in these programs continues to be low; only 10% to 20% of patients who survive an acute MI participate in an exercise-based secondary prevention CR program. The reason for such low participation is likely multifactorial, but 1 important obstacle is the infrastructure to support prolonged participation in these programs. Another barrier to usage is likely the absence of large randomized controlled trials (RCTs) evaluating its efficacy and insufficient data on what features of CR programs result in the greatest efficacy.
Individual RCTs studying the efficacy of exercise-based CR have provided conflicting results, and the most recent meta-analysis (published in 2004) found that CR decreased all-cause and cardiac mortality but had no beneficial effects on reinfarction. In addition, considerable heterogeneity among programs exists, and the factors that define "effective" CR on a program-level—including optimal duration — are currently unclear. Given these areas of uncertainty, we undertook a meta-analysis of RCTs to (1) accurately estimate the effect of CR on cardiovascular outcomes and (2) conduct stratified analyses to examine the effect of RCT-level characteristics on the benefits of CR.
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