Even 'high normal' glucose levels may increase the risk of hospitalization for heart failure

Fasting glucose levels may independently predict the risk of being hospitalized with congestive heart failure in heart attack survivors and others who are at high risk of developing the disorder, researchers reported in Circulation: Journal of the American Heart Association.

Drawing on data from 31,546 high-risk patients participating in two international trials, researchers found that even small increases in fasting glucose raised the risk of congestive heart failure in both diabetes patients and those whose blood sugar fell within the normal range.

"This illustrates that blood glucose by itself is a continuous risk factor for developing heart failure because all of these patients were free of heart failure when they enrolled in the trials," said Claes Held, M.D., Ph.D., lead author of the study.

"However, these are only associations," said Held, an associate professor of cardiology at the Karolinska Institutet in Stockholm, Sweden. "They do not prove that elevated blood glucose causes heart failure. To demonstrate a causal relationship, you would have to do a study that showed lowering blood glucose levels would reduce the incidence of heart failure."

About 5.2 million Americans evenly divided between males and females suffer from heart failure, according to the American Heart Association. Each year about 550,000 new cases are diagnosed and about 57,700 people die from it. Heart failure is a debilitating condition in which the heart fails to pump an adequate supply of blood throughout the body. Established heart failure risks include uncontrolled high blood pressure, diabetes and heart attack.

To examine the relationship between blood glucose levels and congestive heart failure, Held and colleagues performed an interim analysis on the blinded data from the ONgoing Telmisartan Alone and in combination with the Ramipril Global Endpoint Trial (ONTARGET) and Telmisartan Randomized AssessmeNt Study in aCE iNtolerant subjects with cardiovascular Disease (TRANSCEND) trials. Both were randomized, controlled, parallel clinical studies testing drug regimens aimed at reducing fatal and nonfatal cardiovascular events. ONTARGET had 25,620 patients enrolled and TRANSCEND had 5,926, and both included patients with and without diabetes. Researchers obtained fasting blood glucose levels for patients when they entered the trials and periodically thereafter.

"We know that diabetes is a strong risk factor for cardiovascular disease including heart failure, but these studies included patients with and without diabetes," Held said. "This was a great opportunity to evaluate a broad population of high-risk individuals and study the association between blood glucose and cardiovascular disease, regardless of the diabetic state."

Patients in the two trials were average age 67 at entry, and 69 percent were men. Thirty-seven percent had been previously diagnosed with diabetes and 3.2 percent were diagnosed with the disease at the time of entry.