In patients with type 1 diabetes, poor glycemic control was associated with increased long-term risk for death and major adverse CV events after CABG in a population-based cohort study.

Researchers investigated whether preoperative HbA1c levels predicted death or CV events after CABG for patients with type 1 diabetes.

Using data from the Swedish National Diabetes Register and the SWEDEHEART registry, they analyzed 764 patients in Sweden with type 1 diabetes who underwent primary isolated nonemergency CABG between 1997 and 2012.

The primary outcome was death or major adverse CV events — defined as MI, stroke, HF or repeat revascularization — in relation to HbA1c levels. Median follow-up was 4.7 years.

Thomas Nyström, MD, PhD, and colleagues found that during the follow-up period, 44% of patients died or experienced a major adverse CV event, for an incidence rate of 82 per 1,000 person-years.

Nyström, from the department of clinical science and research, Karolinska Institutet, and the division of internal medicine, Södersjukhuset, both in Stockholm, and colleagues found that the risk for death or major adverse CV events increased with increasing preoperative HbA1c level.

Compared with patients with HbA1c levels less than 7%, the researchers observed the following HRs for the primary endpoint:

  • patients with HbA1c 7.1% to 8%, HR = 1.34; 95% CI, 0.82-2.21;
  • patients with HbA1c 8.1% to 9%, HR = 1.59; 95% CI, 1-2.54;
  • patients with HbA1c 9.1% to 10%, HR = 1.73; 95% CI, 1.03-2.9; and
  • patients with HbA1c > 10%, HR = 2.25; 95% CI, 1.29-3.94.

When the researchers analyzed HbA1c as a continuous variable, they observed an HR of 1.18 (95% CI, 1.06-1.32) for each 1% increase in HbA1c.

Adjustment for age, sex and risk factors did not change the results.

In a related editorial, Thomas M. Maddox, MD, MSc, FACC, FAHA, and T. Bruce Ferguson Jr., MD, wrote that the results support the American Diabetes Association’s guidelines calling for tight glycemic control among patients with type 1 diabetes to minimize CV morbidity and mortality.

“The methods were rigorous, and the findings were convincing,” wrote Maddox, cardiologist at the Veterans Administration Eastern Colorado Health Care System, associate director of the VA CART program and associate professor of medicine at the University of Colorado School of Medicine, Aurora, and Ferguson, from the East Carolina Heart Institute department of cardiovascular sciences, Brody School of Medicine at East Carolina University, Greenville, North Carolina. “These insights will provide useful information to clinicians regarding prognosis of post-CABG patients with [type 1 diabetes] and to researchers needing baseline risks to inform sample size calculations in interventional trials.” 

Disclosure: The researchers, Maddox and Ferguson report no relevant financial disclosures. 

Maddox TM, Ferguson TB. J Am Coll Cardiol. 2015;doi:10.1016/j.jacc.2015.05.050.
Nyström T, et al. J Am Coll Cardiol. 2015;doi:10.1016/j.jacc.2015.05.054.

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