Heart failure patients with diabetes may benefit from higher glucose levels
Lowering glucose levels for people with diabetes is normally critical to improving health outcomes. But for diabetes patients with heart failure, that might not always be the case, say UCLA researchers.
A new study found that for advanced heart failure patients with diabetes, having higher blood glucose levels may actually help improve survival rates.
Published online in the American Journal of Cardiology, the study by UCLA researchers compared levels of glycosylated hemoglobin, a marker used to track glucose levels, in advanced heart failure patients with and without diabetes. The marker is gauged through a simple blood test.
The study assessed the relationship between levels of the marker and mortality outcomes. Researchers found that among heart failure patients with diabetes, there was a 15 percent decrease in mortality for every unit increase in the marker.
"We were surprised that the optimal level of glycosylated hemoglobin in this patient population with diabetes was higher than levels in current treatment guidelines," said senior author Dr. Tamara Horwich, an assistant professor of cardiology at the David Geffen School of Medicine at UCLA. "We may find that doctors who treat patients who have both advanced heart failure and diabetes may not need to focus on aggressively lowering blood sugar, but rather keep it under moderate control."
Approximately 25 to 50 percent of patients with heart failure also have diabetes, compared with just 7 percent of the general population. The relation could be due to similar physiological processes that underlie both conditions, such as oxidative stress, patterns of hormonal activity and vascular-lining dysfunction that can lead to conditions like atherosclerosis.
For the study, researchers assessed the medical records of 845 patients with advanced heart failure who were referred to a single university center, the Ahmanson–UCLA Cardiomyopathy Center. Most of the patients were men (72 percent), and the average age was 55.
Patients were classified as having diabetes or not, and they were also grouped into four levels based on their amount of glycosylated hemoglobin. Using statistical analysis, the researchers calculated patients' risk of death or need for an urgent heart transplant.
"We found that for heart failure patients with diabetes, higher — not lower — levels of the marker had better outcomes," said first author Sofia Tomova, a medical student in the division of cardiology at the Geffen School of Medicine.
The researchers found that for the diabetic heart failure patients, two-year event-free survival was highest among patients with the highest elevated glycosylated hemoglobin levels: a 65 percent survival rate for patients with Level 4 (greater than 8.6 percent of the marker) and a 61 percent survival rate for those with Level 3 (7.3–8.5 percent of the marker).
Patients with lower levels of the marker had worse survival rates: a 48 percent survival rate for patients with Level 1 (less than 6.4 percent of the marker) and a 42 percent survival rate for those with Level 2 (6.5–7.2 percent of the marker).
According to the researchers, the ideal level of glycosylated hemoglobin in heart failure patients with diabetes appears to be in the 8.3–8.9 percent range. Current national treatment targets aim much lower, at 7 percent.
In the heart failure patients without diabetes, there was no significant mortality risk difference between the glycosylated hemoglobin levels.
The researchers noted that for those without heart failure, having diabetes and elevated glycosylated hemoglobin levels is a risk factor for developing heart failure. However, the study shows that if a patient already has heart failure, having higher glycosylated hemoglobin levels may be protective.
According to the researchers, the next steps in research will include studies to test the optimal glucose-management goals, as well as to assess the best anti-diabetic medications for heart failure patients with diabetes.
Heart failure affects 6 million people in the United States alone and is caused by weakened heart muscle function, which can result in a build up of fluid in the lungs and other organs due to the heart's inability to pump effectively.
No outside funding was used for the study.
Additional UCLA study authors included Vani Nimbal.