Poor Glycemic Control Linked With Improved Survival in Diabetics With Heart Fail

Contrary to what has been shown in otherwise healthy diabetics, elevated HbA1c levels, an indicator of poor glycemic control, are associated with improved survival among diabetics with advanced systolic heart failure, new research shows.

"The presumption was that better glycemic control would be associated with better outcomes" senior author Dr. Gregg C. Fonarow, from the University of California at Los Angeles, told Reuters Health. "Yet, in previous studies, a number of factors normally tied to adverse outcomes, such as high cholesterol levels, have been linked to improved outcomes in patients with heart failure." So, it was unclear what to expect with elevated HbA1c levels, he added.

In the study, reported in the American Heart Journal for January, the outcomes of 49 diabetics with HbA1c levels no greater than 7.0 were compared with those of 74 patients with higher HbA1c levels. All of the patients had advanced systolic heart failure.

"The American Diabetes Association recommends a target HbA1c of 7.0 or lower, which is why we used this" cutoff, Dr. Fonarow explained.

The subjects had diabetes for 8.6 years, on average, and had a mean ejection fraction of 25%, the report indicates. The HbA1c groups were comparable in terms of heart failure severity, BMI, and diabetes duration and treatment.

Subjects in the elevated HbA1c group had higher ejection fractions and were more likely to use beta-blockers and sulfonylurea than their peers in the recommended HbA1c group.

Poor glycemic control was associated with an all-cause mortality of 20%, significantly lower than the 35% rate seen in patients with recommended control. Multivariate analysis showed that an HbA1c level of 7.0 or lower raised the risk of death by 2.3-fold.

"This study alone should not change the diabetes management of patients with heart failure, but hopefully it will spur further research in this patient population," Dr. Fonarow said.

As to how poor glycemic control might yield improved outcomes, Dr. Fonarow said there are several possible explanations. "Patients with worse control tend to have higher cholesterol levels and there is evidence that circulating cholesterol and lipoproteins can deactivate toxins associated with heart failure. Another possibility is that patients with worse control have a greater metabolic reserve to handle the catabolic stress of heart failure."

Am Heart J 2006;151:91.e1-91.e6