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In patients with diabetes, coronary artery bypass graft (CABG) surgery is associated with less mortality but more nonfatal myocardial infarction (MI) compared with percutaneous coronary intervention (PCI), according to a study in the February 26, 2013, issue of the Journal of the American College of Cardiology.

The study was stopped because of slow recruitment after only enrolling 25% of the intended sample size and hence can only produce hypothesis-generating results, the authors caution.

Masoor Kamalesh, MD, of the Krannert Institute of Cardiology, Veterans Affairs Medical Center (Indianapolis, IN), and colleagues looked at 198 male US veterans with diabetes and severe coronary artery disease being treated at 22 institutions. Patients were randomized to CABG (n = 97) or PCI (n = 101) between August 26, 2006, and March 24, 2010.

After a mean follow-up of 2 years, the risk of all-cause mortality was higher in the PCI arm, while the risk of nonfatal MI was higher in the CABG arm (table 1).

Table 1. Two-Year Clinical Outcomes

These 2 risks offset each other, such that the combined incidence of death or nonfatal MI was 18.4% for CABG and 25.3% for PCI (HR 0.89; 95% CI 0.47-1.71).

The study was too small to find any significant differences in the composite endpoint or its components in any predefined subgroups, with the exception of all-cause mortality (3.5% for CABG vs. 28.3% for PCI; P = 0.05) in patients with glycosylated hemoglobin less than 8%, which represented the largest subgroup.

Patients in the PCI arm who died were slightly older (P = 0.01) than those who survived, and they had slightly worse ventricular function (P = 0.04). There were no differences between PCI survivors and nonsurvivors related to Syntax score or stent model used.

Supporting Prior Studies

“We were surprised that we got significant results with such a small sample size,” Dr. Kamalesh told TCTMD in a telephone interview. He blamed competing therapies, a limited domestic patient base, and “very strict entry criteria” for the study’s low enrollment.

Still, “our results . . . are clearly in line with all the prior data suggesting that bypass surgery is definitely more durable in the long term for managing patients with multivessel disease and diabetes, or those who have single-vessel left anterior descending artery stenosis,” Dr. Kamalesh said, adding that the results hold true regardless of the Syntax score.

Reimbursement may affect treatment decisions in light of the increasing prevalence of diabetic patients with coronary artery disease and continuing frustration over how to control diabetes and risk factors, he said. Insurers “will demand that patients with multivessel disease and diabetes be offered bypass surgery first because they want to get the best bang for their buck.”

Results from both the ASCERT and FREEDOM studies are in line with the findings of the current trial, he said, but “diabetics make up a third of patients with coronary artery disease, so [cardiovascular surgeons] still have some work to do.”

Chance, MI Definition May Play Roles

In an accompanying editorial, Stephen G. Ellis, MD, of the Cleveland Clinic (Cleveland, OH), questions how to best interpret the dubious significance of the mortality difference at 2 years between PCI and CABG. “Acknowledging the small number of events, one must recognize that this apparent difference may be due to the play of chance. It would have been useful if the investigators had provided the causes of death for these patients,” he writes. “That said . . . one cannot ignore these findings.”

Dr. Ellis also focuses on the higher rate of MI in the CABG group, noting that with the “novel” definition used (fivefold increase in CK-MB plus diagnostic new Q waves on ECG), “some events that might be considered periprocedural PCI MIs were missed.”

“It seems, on the basis of the current body of evidence, that CABG should be preferred over PCI in patients with diabetes and multivessel disease with complex anatomy exemplified by SYNTAX scores > 22, and perhaps even all patients with diabetes with multivessel disease,” he concludes. “That said, we still need further data regarding the important interaction between lesion number and complexity and clinical outcomes with the 2 approaches.”

Mortality, MI Going in Different Directions

In a telephone interview with TCTMD, Michael E. Farkouh, MD, MSc, of Mount Sinai School of Medicine (New York, NY), also touched on the “excess rate of myocardial infarction in the bypass group compared with PCI, [because] this is the exact opposite of what we’ve seen in the other trials.”

The trial “had a definition which was too stringent for PCI, and therefore there was an [over-identification] of the MIs in the bypass arm due to using enzymes and not just Q waves,” he said. “So I think the definition of MI is misleading and gives the impression that there are more MIs in the bypass arm, which is exactly the opposite of what we saw in FREEDOM.

“From an epidemiological perspective it’s very unusual to see mortality go in one direction and MI go in the other direction,” Dr. Farkouh continued. “They usually go together with coronary disease.”

Future studies should evaluate how newer-generation stents may change the equation, while clinicians should acknowledge “the idea that at some point we have to accept that bypass appears to be superior to PCI for patients with diabetes and complex coronary disease,” he said. “The real issue is how we can improve PCI outcomes with optimizing medical therapy.”

Study Details

The stents used were Taxus (n = 35; Boston Scientific; Natick, MA), Cypher (n = 20; Cordis; Miami Lakes, FL), Xience/Promus (n = 18; Abbott Vascular; Santa Clara, CA), Endeavor (n = 2; Medtronic, Minneapolis, MN), mixed DES (n = 16), and mixed BMS (n = 1).

Sources:

1. Kamalesh M, Sharp TG, Tang C, et al. Percutaneous coronary intervention versus coronary bypass surgery in United States veterans with diabetes. J Am Coll Cardiol. 2013;61:808-816.
2. Ellis SG. Coronary revascularization for patients with diabetes: Updated data favor coronary artery bypass grafting. J Am Coll Cardiol. 2013;61:817-819.

Related Stories:

• FREEDOM: CABG Superior to PCI in Diabetic Patients with Multivessel Disease
• PCI, Surgery Show Similar Long-term Mortality in Diabetic, Nondiabetic Patients
• Study Compares Stents, Surgery in Diabetics with Multivessel Disease