Cardiac rehab after CABG: More grist for guidelines

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 - cardiac rehabilitation

Cardiac rehabilitation (CR) after CABG improved long-term survival in a community-based study, supporting American Heart Association and American College of Cardiology Foundation guidelines recommending CR for this group of patients.

Using data on 846 patients from Olmsted County, Minn., who had a CABG procedure between 1996 and 2007, researchers from the Mayo Clinic compared the long-term survival rates of those who underwent CR post-CABG and those who did not.

“We found in our large contemporary, community-based, mixed age, post-CABG cohort that CR participation was significantly associated with an approximate 45 percent reduction in all-cause mortality,” wrote lead author Quinn R. Pack, MD, of the Division of Cardiovascular Disease and Internal Medicine, and colleagues. The study was published online July 8 in Circulation.

More than 300,000 patients have CABG surgery in the U.S. every year, according to the researchers, but there have been few robust studies examining CR’s impact on survival after the procedure.

For the study, the researchers eliminated patients who died or were lost to follow-up within six months, letting all participants have equal opportunity to undergo CR.  Participation in CR was defined as attending at least one session within six months of the CABG procedure. 

Most patients started CR within a month after discharge, and all started within six months. Overall attendance was 69 percent, and the average number of CR sessions was 14. Sex, age, diabetes and MI history had no significant impact on the results. There was also no association between the number of CR sessions and mortality.

During the average follow-up time of nine years, the 10-year all-cause mortality rate was 28 percent. Before adjustments, the 10-year cumulative all-cause mortality rate for the CR group was 20 percent, compared with 45 percent for the non-CR group.

“We found in our large contemporary, community-based, mixed age, post-CABG cohort that CR participation was significantly associated with an approximate 45 percent reduction in all-cause mortality,” they wrote.

The authors offered two possible reasons for their findings. First, there is an actual association between CR and a lower risk of dying, related to how CR affects the implementation of secondary prevention measures in CABG patients.

“Previously published studies support this concept, showing that CR participation is associated with improvements in coronary heart disease factor control as well as long-term follow-up and adherence to secondary prevention medications,” the authors wrote. 

In their study, they noted better control of low-density lipoprotein (LDL), better measurement of LDL and better outpatient follow-up.

It is also possible that patients who participate in CR are healthier and more willing to adopt a healthier lifestyle, but the authors said they controlled for factors associated with this “healthy cohort” bias.

The study also limited inclusion to patients living in Olmsted County, which could affect generalizability of the findings.

The 68 percent of study patients who went to CR was considerably higher than the 20 to 30 percent rate nationwide. 

“This implies that, nationally, higher participation rates are clearly achievable and that many more patients would attend CR if given the opportunity,” the authors explained.

And they contended that despite any bias that may confound the results, the association between CR and reduced mortality risk would still be significant. Their findings “strongly support national standards that recommend CR for this group.”