Compared with patients with moderately controlled glucose levels, diabetic patients who have heart failure and either too high or too low glucose levels may be at increased risk of death, according to a retrospective study published online July 17 in the Journal of the American College of Cardiology.
David Aguilar, MD, assistant professor of medicine and cardiology at Baylor College of Medicine in Houston, and colleagues sought to examine the relationship between thiazolidinedione (TZD) use and outcomes in ambulatory patients with diabetes and heart failure.
To determine average glucose levels in the blood over a two to three month period, doctors measure glycosylated hemoglobin. In general, higher levels have been associated with increased risk of heart disease, according to Aguilar.
"Most doctors try to keep glucose levels of those with diabetes as low as they can to lower the risk of complications such as eye problems, kidney disease or the development of heart disease," Aguilar said. "However, we found that in diabetic patients with heart failure, glucose levels slightly higher than what are normally recommended had the lowest risk of death."
The researchers identified 7,147 veterans with heart failure and diabetes who were receiving treatment at various VA medical centers across the U.S. They followed the patients for two years, dividing them into five categories based on their glycosylated hemoglobin levels. The outcomes were time to hospitalization for heart failure and time to death.
Of the 7,147 ambulatory heart failure patients receiving diabetic therapy, 11.4 percent were receiving a TZD and 65.8 percent were not receiving insulin sensitizers, the authors wrote. Over two years of follow-up, 134 patients receiving TZDs and 741 patients not receiving insulin-sensitizing medications required heart failure hospitalization. A total of 168 patients receiving TZDs and 1,192 patients not receiving insulin-sensitizing medications died.
In ambulatory patients with established HF and diabetes, Aguilar and colleagues found that the use of TZDs was not associated with an increased risk of HF hospitalization or total mortality when compared with those not receiving insulin-sensitizing medications.
The authors noted that most medical professionals recommend levels at seven and below as the target for optimal health for diabetic patients. However, the results of the study of diabetic patients with heart failure showed that those with levels 7.1 to 7.8 had the lowest rate of death. Those patients at both ends of the spectrum had the higher death risks.
"This doesn't mean that diabetic patients with heart failure should change their target goal for glucose levels," Aguilar said. "The results could simply be telling us that the glycosylated hemoglobin levels are a marker for other risks that are contributing to increased risk of death, but not necessarily the cause of the problem."
Aguilar said that the correlation needs to be further investigated to confirm the findings and see what other factors could be contributing to the mortality rate.