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High levels of hemoglobin A1C appear to increase risk of complications following CABG

Monday, October 13 2008 | Comments
Evidence Grade 11 What's This?
High levels of hemoglobin A1C increase the likelihood of complications after coronary artery bypass grafting (CABG), a recent study suggests.

Researchers used a multivariate logistic regression model to determine whether high levels of preoperative A1C were linked with renal failure, myocardial infarction (MI), deep sternal wound infection, cerebrovascular accident (CVA), or in-hospital mortality after CABG.

Of 3,555 consecutive patients who underwent primary, elective CABG at a single academic facility from April 1, 2002 through June 30, 2006, preoperative levels of A1C were measured in 3,089 (86.9%) and entered into a computer database. Of that number, 2,275 had A1C <7%, while 814 had levels that were >=7%. The American Diabetes Association recommends that patients with diabetes achieve A1C levels <7%, which is associated with a lower risk of complications from the disease.

Among the patients with available A1C levels, 31 (1.0%) died in the hospital. Receiver operating characteristic curve analysis revealed that A1C >=8.6% was associated with a 4.4-fold increase in mortality. For each unit increase in A1C, there was a significantly increased risk of MI and deep sternal wound infection. In addition, A1C >=6.7% increased the odds of renal failure (OR, 2.10; 95% CI, 1.16-3.30), A1C >=7.6% increased the odds of CVA (OR, 2.23; 95% CI, 1.06-4.70), and A1C>=7.8% increased the odds of deep sternal wound infection (OR, 5.29; 95% CI, 2.00-14.00).

"A1C may be a more accurate predictor of outcomes than merely a diagnosis of diabetes, with the added benefit of quantification of diabetes as a risk factor," researchers said.

Indeed, a simple lab test drawn before surgery "may provide the clinician with a more accurate risk profile and provide additional prognostic information when discussing morbidity and mortality risks with patients and their families."

Further data are needed to determine whether results of the study warrant practice changes in patients with poorly controlled or newly diagnosed diabetes, researchers added. (Halkos ME, et al. J Thorac Cardiovasc Surg 2008;136:631-640.)

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