High HbA1c levels after coronary intervention may predict risk of adverse events

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A new study indicates that patients with glycosylated haemoglobin A (HbA1c) ≥7 at two years after undergoing percutaneous coronary intervention (PCI) have a higher rate of major adverse cardiac and cerebrovascular events (MACCE) than patients with HbA1c <7. This finding, authors Jin Kyung Hwang (Division of Cardiology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea) and others report, suggests that high HbA1c after PCI increases the risk of adverse events.

Writing in Circulation: Cardiovascular Interventions, the authors comment that the association between HbA1c at the time of PCI and subsequent events has been reported “in a few studies with conflicting results,” adding “it is not known if glycaemic control after PCI can improve cardiovascular outcomes, which is a more important issue than glycaemic status at the time of PCI.” Noting that diabetic patients “account for more than a quarter of all patients undergoing PCI and have worse outcomes compared with non-diabetic patients”, Hwang et al observe that “determining the optimal strategy for glycaemic control in these patients after PCI has substantial clinical implications”.

The aim of their study, therefore, was to compare outcomes in type 2 diabetes patients with HbA1c ≥7 at two years after PCI—“with that time point being chosen because it “reflected the stabilised and long-term status of glycaemic control—with those of type 2 diabetes patients with HbA1c <7. The primary outcome was the long-term rate of MACCE, which was defined as a composite of cardiac death, myocardial infarction, any repeat revascularisation, or stroke during the follow-up period.

Of 5,819 consecutive patients who underwent PCI with a drug-eluting stent between January 2003 and December 2011 at the authors’ centre, 1,399 had type 2 diabetes. Of these, 980 had available HbA1c data at baseline and at two years (489 with HbA1c <7 vs. 491 with HbA1c ≥7 at two years). To account for baseline differences between the two groups, the authors used propensity scoring to create 322 matched pairs. They note that among these matched pairs, HbA1c was similar at baseline but significantly different at one year after PCI and remained stable thereafter. “Compared with baseline HbA1c, median HbA1c levels measured every year after PCI were significantly higher in the HbA1c ≥7 group than those in the HbA1c <7 group (p<0.01),” Hwang et al comment.

The rate of MACCE was significantly lower in the HbA1c <7 group than in the HbA1c ≥7 group: 27.5% vs. 37.4%, respectively (p=0.03). This reduced rate was mainly driven by a lower rate of repeat revascularisation in the HbA1c <7 group. The authors report that randomised controlled trials suggest that second-generation drug-eluting stents, compared with first-generation drug-eluting stents, do not reduce the risk of target lesion revascularisation or target lesion failure in diabetic patients. They add: “Therefore, there is still a substantial need to reduce restenosis and target lesion revascularisation in diabetic patients. In our study, the association between glucose control and improved outcomes was consistent without regard to type of drug-eluting stent.”

Joo Yang Hahn

Furthermore, according to Hwang et al, another important finding in the study was that the lower levels of HbA1c were associated with a significantly lower rate of non-target lesion revascularisation. The authors write that, given the cumulative event rate of non-culprit lesions in diabetic patients is higher than in non-diabetic patients, reduction of non-target lesion revascularisation is an important factor in improving the rate of cardiovascular events in diabetic patients “and glucose control may be the appropriate treatment strategy in this respect”.

Hwang et al conclude: “Our data suggest that high HbA1c levels two years after PCI may identify a population at increased risk of adverse events, especially repeat revascularisation.”

Study author Joo-Yong Hahn (Heart Vascular Stroke Institute, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea) told Cardiovascular News: Because our study was a non-randomised, observational study, we cannot make a definite conclusion. However, I believe that an active attempt to reduce HbA1c is needed in patients who have undergone PCI and can improve clinical outcomes. Of note, the effects of glucose control in type 2 diabetes may differ according to patient characteristics such as recent cardiovascular events, glycsemic control status, and duration of diabetes.”