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Cardiac Rehab Improves Outcomes After Percutaneous Coronary Intervention
Abstract & Commentary
By Andrew J. Boyle, MBBS, PhD, Assistant Professor of Medicine, Interventional Cardiology, University of California, San Francisco
Source: Goel K, et al. Impact of cardiac rehabilitation on mortality and cardiovascular events after percutaneous coronary intervention in the community. Circulation 2011;123:2344-2352.
The benefits of cardiac rehabilitation following myocardial infarction (MI) are well known. However, whether these benefits are also seen in ambulant community-based patients who undergo percutaneous coronary intervention (PCI) is not known. Goel and colleagues examined the Mayo Clinic PCI database for patients who resided in Olmsted County, Minnesota, who underwent PCI between 1994 and 2008; they compared the outcomes of those who attended cardiac rehabilitation (CR) following PCI against those who did not. Their primary endpoint was all-cause mortality.
They identified 2395 patients, of whom 964 (40%) participated in at least one CR session within 3 months of PCI. Interestingly, after the Centers for Medicare and Medicaid changed the regulations to include PCI as a reimbursement indication for CR in 2006, there was an approximate 3-fold increase in the rates of attendance at CR. The mean number of sessions attended was 13 per patient; however, they included in their analysis all patients who attended one or more sessions as having received CR. Independent factors that were positively associated with CR participation include age, year of PCI, history of acute MI, involvement of minor branches of the coronary artery, antiplatelet therapy during PCI, and occurrence of in-hospital MI or coronary artery bypass graft surgery. On the other hand, smoking, history of diabetes mellitus, previous PCI, and use of drug-eluting stents were independently associated with decreased participation in CR after PCI. To assess the effect of CR on clinical outcomes, the authors used three different statistical techniques to enhance the accuracy of their results: propensity score-matched analysis (n = 1438), propensity score stratification (n = 2351), and regression adjustment with propensity score in a 3-month landmark analysis (n = 2009). Significant baseline differences existed between those who received CR and those who did not receive CR, but after propensity score matching, there were no clinical differences between groups.
CR was associated with a significant 45%-47% reduction in all-cause mortality by all three statistical analyses (HR 0.53 to 0.55; P < 0.001). However, there were no differences in the rates of non-fatal MI and repeat revascularization. There was a trend toward reduction in cardiovascular mortality (significant reduction by one statistical method but non-significant by the other two methods). The authors conclude that CR participation after PCI was associated with a significant reduction in mortality rates and these findings add support for current guidelines, practice standards, and insurance coverage policies that recommend CR for patients after PCI.
Goel and colleagues present an important dataset that advances our knowledge of the effects of CR on patients who have undergone PCI. Several strengths and limitations of the study bear discussing. Because their center was the only CR facility in the county during the time of the study, and they only included patients residing in their county, their data are likely to be inclusive. This cohort has been well studied and is representative of other community cohorts. However, they are a predominantly white, non-hispanic community, and so the results here may not be generalizable to more racially heterogeneous communities.
Another important factor to consider is the retrospective observational nature of this study. Although these data are collected prospectively, one must interpret retrospectively analyzed data with caution. There is likely to be inherent selection bias in who is referred for CR, as well as who actually attends. There are obvious confounders that were not collected in this dataset, such as education level and socioeconomic status, that are known to influence outcomes in patients with coronary artery disease. Although the rigorous statistical methodologies used by the authors strengthen their conclusions from these data, there will always be unmeasured confounders in non-randomized studies, and the results should be interpreted with this in mind.
The mechanism of this mortality reduction is not addressed in this study, and one is left to ponder the mechanism underlying such a large reduction in all-cause mortality, despite no reduction in cardiovascular mortality and no reduction in MI. CR may have physiological benefits for many organ systems, not just the heart, and may result in lower mortality from other disease states. This finding is, however, consistent with prior studies. This study confirms that CR is an important part of our treatment of patients with coronary artery disease who have undergone PCI.