New AHA statement on hyperglycemia during ACS admissions

March 2, 2008 By Benjamin A. Olenchock, M.D. Ph.D. [mailto:bolenchock@partners.org]

The American Heart Association (AHA) Diabetes Committee of the Council on Nutrition, Physical Activity, and Metabolism has issued a scientific statement regarding the importance of hyperglycemia in patients with acute coronary syndromes (ACS). The statement is designed to raise awareness of this issue, propose future research directions in this field, and recommend reasonable guidelines for blood sugar monitoring and treatment in ACS patients based on the limited available evidence.

The association between high blood sugar on admission or later in the course of an ACS admission and poor in-hospital and long-term outcome is well established. Although studies vary, the in-hospital risk of death among non-diabetic patients with significant admission hyperglycemia is almost 4-fold higher than those with normal blood sugar. Data from the Cooperative Cardiovascular Project estimates a 7 to 46% increase in 1-year mortality, depending on the degree of hyperglycemia. Randomized controlled trials of glucose control in ACS patients have been performed, however interpretation of the data is limited by failure to achieve differences in blood sugar control. The AHA statement is clear that data in this important field is unfortunately quite limited.

The mechanism by which elevated blood sugar correlates with poor outcomes is interesting. There are data suggesting that hyperglycemia has direct effects on vascular function, reperfusion injury, cardiomyocyte repolarization, and thrombosis. It remains possible, however, that hyperglycemia is a marker for injury severity. Additionally, it is likely that hyperglycemia identifies a subset of high risk individuals, those with undiagnosed prior diabetes / insulin resistance who are less likely to have close monitoring and correction of hyperglycemia during their ACS admission.

In the absence of straight-forward evidence regarding targets for glucose control and benefits to intense insulin regimens in ACS patients, the new AHA guidelines boil down to this: First, they recommend that glucose level should be part of the admission laboratory tests. In ICU-level patients, they suggest that we follow the data from surgical ICU patients and be aggressive about blood sugar control through use of intravenous insulin, especially in patients with glucose levels over 180 mg/dL. As the precise goal of treatment is not defined, they recommend a goal of normoglycemia (glucose 90 to 140 mg/dL). For non-ICU ACS patients, the recommend the use of subcutaneous insulin in patients with plasma glucose over 180 mg/dL. And of course, a standard diabetes workup should be performed and outpatient blood sugar control should be considered prior to discharge.

The new AHA statement comes soon after the recent media splash made by the early termination of the ACCORD (Action to Control Cardiovascular Risk in Diabetes) study, due to higher rates of death in the intensive blood sugar control arm. Management of blood sugar during an ACS admission is obviously a much different issue than aggressive outpatient management with oral hypoglycemic medicines and insulin. The connection is a sense that more attention is being paid to the important correlation between blood sugar control and cardiovascular risk, and that the targets of therapy – for inpatients or outpatients - is not clearly defined.