In patients with diabetes and severe coronary artery disease (CAD), prior research found an association between coronary artery bypass grafting (CABG) and improved long-term mortality and freedom from major cardiovascular and cerebrovascular events (MACCEs), as compared with percutaneous coronary intervention (PCI) in subgroup analyses of revascularization trials.
These hypothesis-generating findings from the diabetic subgroups of revascularization trials led investigators to conduct a dedicated trial to compare PCI with CABG in those who have diabetes—the Future Revascularization Evaluation in Patients with Diabetes Mellitus: Optimal Management of Multivessel Diseases (FREEDOM) randomized clinical trial (RCT). This trial randomized 1,900 patients with diabetes to intervention with PCI with drug-eluting stents or CABG and demonstrated a mortality benefit and reduced risk of nonfatal myocardial infarction (MI) that favored CABG.
RCT Vs Real-World Efficacy
The FREEDOM trial led to important guideline changes in North America that recommended CABG over PCI. However, despite the finding of superiority for CABG over PCI in patients with diabetes and multivessel disease, it remains unclear if the efficacy observed in RCTs translates to comparative effectiveness in real-word practice.
On this background, we and our colleagues sought to compare both trends in revascularization practices and long-term outcomes between CABG and PCI in the real-world setting in patients with diabetes, using multiple administrative and clinical data sets housed at ICES (formerly known as the Institute for Clinical and Evaluative Sciences) in Ontario, Canada’s most populous province of 13 million people.
In our first paper, we used interrupted time series models to assess the impact made by the publication of the FREEDOM trial and the subsequent publication of the American Heart Association (AHA) guideline updates. In our second manuscript, due to potential differences in baseline characteristics of the patient populations in this study, a propensity score-matched analysis was conducted between CABG and PCI patients to help minimize these differences.
CABG Supported by Evidence Yet Underutilized Vs PCI
We made several interesting observations in our study. In our trends paper, we found that the publication of FREEDOM in 2012, followed by guideline changes in 2014, did not impact the proportion of patients with diabetes undergoing CABG or PCI. Specifically, we found that in patients treated at centers that only offered PCI, there was a decreased trend in CABG referral and use.
This helped explain findings from our more recent Journal of the American College of Cardiology manuscript, which showed that in patients who underwent PCI, only 10% ever had a pre-operative consult with a cardiac surgeon. Overall, in follow-up to 10 years, our study found that CABG was linked with improved long-term survival and freedom from MACCEs compared with PCI in patients with diabetes and multivessel disease (Figure). These findings were consistent with the FREEDOM trial and suggest that the RCT findings were generalizable to the real-world population.
Clinical & Health Policy Implications
Several important policy implications result from these two manuscripts. In patients with diabetes and multivessel CAD, CABG remains the preferred revascularization option in those who are surgical candidates, with PCI being the alternative treatment. This finding is consistent in clinical trial and real-world settings. In addition, patients who undergo coronary catheterization at centers without cardiac surgical expertise may be more likely to receive inferior treatment, highlighting the importance of a heart team care approach, even at centers without on-site cardiac surgery.
Cardiac surgeons should be more involved in decision making for the treatment of these high-risk patients, while cardiologists should consider a cardiac surgical consult for every patient with diabetes and multivessel CAD prior to performing PCI. Overall, both the FREEDOM trial and our large observational study illustrate that CABG remains the treatment of choice for patients with diabetes and multivessel CAD, offering both a survival advantage and freedom from late adverse cardiac events.
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