Research and Literature
The Link Between Blood Glucose and Heart FailureJanuary 11, 2017 /
A study done in Canada and published online January 7, 2015 in the European Heart Journal found that even a slightly elevated blood glucose level when a patient is hospitalized for heart failure is associated with early all-cause and cardiovascular mortality. It is also an indicator of new diabetes diagnosed among patients not previously diagnosed with diabetes.
The study analyzed 16524 patients with a median age of 79 years who presented with acute heart failure to hospital emergency departments in Ontario between 2004 and 2007. Risk analysis was completed for 30-day mortality, new diabetes diagnoses, and hospitalization outcomes. Fifty-six percent of the cohort did not have pre-existing diabetes. The median blood glucose in people with diabetes was 160 mg/dL and was 116 mg/dL among individuals without pre-existing diabetes. The reference group was patients with blood glucose between 70 and 110 mg/dL. In total, 51% of the patients without pre-existing diabetes had blood glucose levels technically below the threshold for diabetes diagnosis, but over 110 mg/dL.
The risk of new diabetes diagnosis increased linearly in this study, with higher blood glucose at presentation leading to an almost four times the amount of risk of new diabetes diagnoses. Anyone with a blood glucose greater than 110 mg/dL, especially among patients with no pre-existing diabetes, was found to be at a much higher risk of having a poor outcome. In this study, the risk of death within a month was 26% higher among patients with elevated blood sugar levels who had never been diagnosed with diabetes compared to patients with normal blood sugar levels. Individuals whose blood glucose levels were almost high enough to meet the criteria for diabetes diagnosis, but whom had never been diagnosed with diabetes, had a 50% higher risk of death within a month. Patients with pre-existing diabetes were 48% more likely to die within a month and they carried a 29% increased risk of being hospitalized for diabetes-related reasons such as hyperglycemia, skin and soft tissue infections, and amputation if their blood glucose levels were > 200 mg/dL upon presentation to the emergency departments. The risk of death from cardiovascular causes was 28% higher for those with a blood glucose of 110-140 mg/dL and 64% higher among those with a blood glucose of 170-200 mg/dL. Among all patients, with and without pre-existing diabetes, having a blood glucose level above 206 mg/dl increased the risk of hospitalization for heart failure or other cardiovascular reasons by 9-15%.
In another study published in Diabetes Care in 2005, baseline morning blood glucose levels were evaluated with respect to subsequent heart failure using records of 20810 patients. Patients were excluded from the study if they had a pre-existing diagnosis of diabetes, a diagnosis of heart failure less than one year after initial blood glucose determinations, had a blood glucose of > 125 mg/dL, or who took corticosteroids, loop diuretics, insulin, or oral hypoglycemic medications. Higher baseline morning glucose levels were associated with an increase in heart failure from 3.5% among those with fasting glucose < 90 mg/dL, to 4.8% with fasting glucose of 90-99 mg/dL, and to 6% with fasting glucose of 110-125 mg/dL over a mean 4-5 year evaluation period. The incidence rate increased from 7.5 cases per 1,000 person years with fasting glucose of < 90 mg/dL, to 8.4 cases per 1000 person years with a fasting glucose of 90-99 mg/dL, to 11.1 cases per 1000 person years among those with a fasting blood glucose of 100-109 mg/dL, and to 13.7 cases per 1000 person years for people with a fasting blood glucose of 110-125 mg/dL. Adjustments were made for age, sex, BMI, creatinine, hypertension, lipids, smoking, medications, and coronary disease.
Impaired glucose tolerance and impaired fasting glucose have been linked to macrovascular disease, increased mortality, and left ventricular hypertrophy. Glucose intolerance is believed to affect over 35 million adults in the United States and the lifetime risk of heart failure may exceed 20%.
These adverse effects of impaired glucose tolerance and impaired fasting glucose may be due to direct effects of hyperglycemia, increased free fatty acids, increased reactive oxygen species, formation of advanced glycation products, change in cardiac metabolism, and mitogenic effects of insulin.
Although insulin infusion may improve exercise function in heart failure, and some research done on animals has found that good glycemic control can improve cardiac function, there is not much clinical evidence that improved glycemic control can improve cardiac function and prevent heart failure.
Researchers note that it is difficult to determine whether elevated blood glucose is the cause or the result of heart failure, but state that all patients presenting with heart failure should have a fasting blood glucose and hemoglobin A1c test done and, even if they don’t meet the criteria for diabetes, they should be monitored more often than other patients and treated early if they do progress to diabetes. These simple tests could identify patients at high risk for early death, further hospitalizations, or the development of diabetes.
References and recommended readings
Harrison P. Elevated blood glucose levels on heart-failure hospitalization increase mortality risk. Medscape website. http://www.medscape.com/viewarticle/837600. Published January 6, 2015. Accessed February 26, 2015.
Nielson C and Lange T. Blood glucose and heart failure in nondiabetic patients. Diabetes Care. 2005; 28(3): 607-611. doi:10.2337/diacare.28.3.607.
Preidt, R. High blood sugar in heart failure patients may point to risk of early death. U.S. News and World Report website. http://health.usnews.com/health-news/articles/2015/01/07/high-blood-sugar-in-heart-failure-patients-may-point-to-risk-of-early-death. Published January 7, 2015. Accessed February 27, 2015.
Sud M, Wang X, Austin PC, et al. Presentation blood glucose and death, hospitalization, and future diabetes risk in patients with acute heart failure syndromes [published online January 8, 2015]. Eur. Heart J. doi:http://dx.doi.org/10.1093/eurheartj/ehu462.