An overview of glycemic control in the coronary care unit with recommendations for clinical management

Acute Hyperglycemia-Induced Injury in Myocardial Infarction

Acute hyperglycemia is a transient increase in plasma glucose level (PGL) frequently observed in patients with ST-elevation myocardial infarction (STEMI). The aim of this review is to clarify the molecular mechanisms whereby acute hyperglycemia impacts coronary flow and myocardial perfusion in patients with acute myocardial infarction (AMI) and to discuss the consequent clinical and prognostic implications. We conducted a comprehensive literature review on the molecular causes of myocardial damage driven by acute hyperglycemia in the context of AMI. The negative impact of high PGL on admission recognizes a multifactorial etiology involving endothelial function, oxidative stress, production of leukocyte adhesion molecules, platelet aggregation, and activation of the coagulation cascade. The current evidence suggests that all these pathophysiological mechanisms compromise myocardial perfusion as a whole and not only in the culprit coronary artery. Acute hyperglycemia on admission, regardless of whether or not in the context of a diabetes mellitus history, could be, thus, identified as a predictor of worse myocardial reperfusion and poorer prognosis in patients with AMI. In order to reduce hyperglycemia-related complications, it seems rational to pursue in these patients an adequate and quick control of PGL, despite the best pharmacological treatment for acute hyperglycemia still remaining a matter of debate.

Selective protein kinase C inhibition switches time-dependent glucose cardiotoxicity to cardioprotection

Hyperglycaemia at the time of myocardial infarction has an adverse effect on prognosis irrespective of a prior diagnosis of diabetes, suggesting glucose is the damaging factor. In ex vivo models of ischaemia, we demonstrated that deleterious effects of acutely elevated glucose are PKCα/β-dependent, and providing PKCα/β are inhibited, elevated glucose confers cardioprotection. Short pre-treatments with high glucose were used to investigate time-dependent glucose cardiotoxicity, with PKCα/β inhibition investigated as a potential mechanism to reverse the toxicity. Freshly isolated non-diabetic rat cardiomyocytes were exposed to elevated glucose to investigate the time-dependence toxic effects. High glucose challenge for >7.5 min was cardiotoxic, proarrhythmic and lead to contractile failure, whilst cardiomyocytes exposed to metabolic inhibition following 5-min high glucose, displayed a time-dependent protection lasting ∼15 min. This protection was further enhanced with PKCα/β inhibition. Cardioprotection was measured as a delay in contractile failure and K_ATP channel activation, improved contractile and Ca²⁺ transient recovery and increased cell survival. Finally, the effects of pre-ischaemic treatment with high glucose in a whole-heart coronary ligation protocol, where protection was evident with PKCα/β inhibition. Selective PKCα/β inhibition enhances protection suggesting glycaemic control with PKC inhibition as a potential cardioprotective therapeutics in myocardial infarction and elective cardiac surgery.

A novel form of glycolytic metabolism-dependent cardioprotection revealed by PKCα and β inhibition

KEY POINTS

Acute hyperglycaemia at the time of a heart attack worsens the outcome for the patient. Acute hyperglycaemia is not limited to diabetic patients and can be due to a stress response in non-diabetics. This study suggests that the damaging cardiac effects of hyperglycaemia can be reversed by selective PKC inhibition. If PKCα/β isoforms are inhibited, then high glucose itself becomes protective against ischaemic damage. Selective PKC inhibition may therefore be a useful therapeutic tool to limit the damage that can occur during a heart attack by stress-induced hyperglycaemia.

ABSTRACT

Hyperglycaemia has a powerful association with adverse prognosis for patients with acute coronary syndromes (ACS). Previous work shows that high glucose prevents ischaemic preconditioning and causes electrical and mechanical disruption via protein kinase C α/β (PKCα/β) activation. The present study aimed to: (i) determine whether the adverse clinical association of hyperglycaemia in ACS can be replicated in preclinical cellular models of ACS and (ii) determine the importance of PKCα/β activation to the deleterious effect of glucose. Freshly isolated rat, guinea pig or rabbit cardiomyocytes were exposed to simulated ischaemia after incubation in the presence of normal (5 mm) or high (20 mm) glucose in the absence or presence of small molecule or tat-peptide-linked PKCαβ inhibitors. In each of the four conditions, the following hallmarks of cardioprotection were recorded using electrophysiology or fluorescence imaging: cardiomyocyte contraction and survival, action potential stability and time to failure, intracellular calcium and ATP, mitochondrial depolarization, ischaemia-sensitive leak current, and time to K_ir 6.2 opening. High glucose alone resulted in decreased cardiomyocyte contraction and survival; however, it also imparted cardioprotection in the presence of PKCα/β inhibitors. This cardioprotective phenotype displayed improvements in all of the measured parameters and decreased myocardium damage during whole heart coronary ligation experiments. High glucose is deleterious to cellular and whole-heart models of simulated ischaemia, in keeping with the clinical association of hyperglycaemia with an adverse outcome in ACS. PKCαβ inhibition revealed high glucose to show a cardioprotective phenotype in this setting. The results of the present study suggest the potential for the therapeutic application of PKCαβ inhibition in ACS associated with hyperglycaemia.

Glycated hemoglobin, admission blood glucose delta, and associated mortality in patients with acute ST-segment elevation myocardial infarction

The importance of glucose metabolism in patients with acute coronary syndrome has been increasingly recognized. We conducted a retrospective study of the associations between prior glycated hemoglobin (HbA1c) levels, admission glucose values, HbA1c-derived estimated average glucose levels (eAG), admission glucose delta (admission glucose - eAG), and mortality in patients presenting with ST-segment elevation myocardial infarction. A total of 676 and 566 patients were included in the in-hospital and 12-month mortality models, respectively. Mean admission blood glucose values were higher in the in-hospital and 12-month mortality groups in patients with no prior diagnosis of diabetes (P < 0.001). Pre, post, and admission HbA1c levels and eAG levels were not associated with in-hospital or 12-month all-cause mortality. The admission glucose delta was higher in patients with in-hospital mortality (87.3 ± 122.7 mg/dL) than in patients who survived (35.88 ± 81.23 mg/dL; P = 0.040). The in-hospital death rate was significantly higher (17% vs 4%, P = 0.017) for patients with admission glucose delta ≥140 mg/dL compared to lower values. In conclusion, HbA1c-derived admission glucose delta is associated with in-hospital mortality in patients with ST-segment elevation myocardial infarction. The mechanisms for the association of acute hyperglycemia with increased acute coronary syndrome mortality are unclear.

Role of plasma glucose level on myocardial perfusion in ST-segment elevation myocardial infarction patients

AIMS

Hyperglycemia is frequent in patients with ST elevation myocardial infarction (STEMI) and is associated with adverse outcome. Aim of our study was to evaluate the correlation between admission plasma glucose level (PGL) and coronary arteries flow velocity.

METHODS

We enrolled 149 STEMI patients successfully treated with primary percutaneous coronary intervention (pPCI). The study population was divided into two groups based on PGL (< or >140 mg/dl) and on history of diabetes, and the groups compared in terms of corrected TIMI frame count (cTFC).

RESULTS

Hyperglycemic patients had a significantly higher cTFC in both the culprit (p < 0.0001) and non-culprit vessel (p: 0.0002); diabetes history impairs as well cTFC of the culprit (p < 0.0001) and non-culprit vessel (p: 0.0001). Within the subpopulation of diabetic patients hyperglycemic ones showed higher cTFC in both the culprit (p 0.0013) and non-culprit vessel (p: 0.0006). Moreover in the whole population cTFC values of both arteries increase linearly with the increment of admission PGL.

CONCLUSIONS

Admission PGL affects coronary flow of both culprit and non-culprit vessel. The impairment of coronary flow is also demonstrated in known diabetic patients, suggesting to consider hyperglycemia an additional risk factor. We finally demonstrated for the first time a positive linear relationship between PGL and cTFC.

Effect of Acarbose on Long-Term Prognosis in Acute Coronary Syndromes Patients with Newly Diagnosed Impaired Glucose Tolerance

OBJECTIVE

To investigate the effect of acarbose therapy on the long-term prognosis of patients with acute coronary syndromes (ACS) complicating newly diagnosed impaired glucose tolerance (IGT).

METHODOLOGY

135 patients hospitalized for ACS who had been newly diagnosed with IGT were randomly assigned to acarbose group (150 mg/day, n = 67) or control group (no acarbose, n = 68). All cases in each group were given the same elementary treatment. Mean follow-up was 2.3 years. The incidence of major adverse cardiovascular event (MACE) and carotid intima-middle thickness (CIMT) were statistically analyzed.

RESULTS

During the mean follow-up of 2.3 years, the risk of recurrent MACE in acarbose group was decreased significantly compared with that in control group (26.67% versus 46.88%, P < 0.05); at the same time, thickening of the CIMT was significantly slower than the control group ((1.28 ± 0.42) mm versus (1.51 ± 0.64) mm, P < 0.05).

CONCLUSIONS

Acarbose can effectively reduce the risk of MACE in ACS patients with newly diagnosed IGT, simultaneously retarding the progression of carotid intima-media thickness.

Glucose management in critically ill adults and children

Blood glucose management in people with acute myocardial infarction and critical illness has always attracted controversy. Compared with the era before 2001 when no attention was given to blood glucose management, DIGAMI-1 in 1995 and the first Leuven study in 2001 showed improved outcomes with strict control of blood glucose, thereby suggesting a causal association between hyperglycaemia and mortality risk. These landmark trials have set the standard in clinical practice that excessive hyperglycaemia is not acceptable. Multicentre trials contradicted the benefits of tight control of patients' blood glucose and results showed that different standard operating procedures for blood glucose control (eg, blood glucose meters or algorithms), divergent concomitant feeding strategies, and varying patient populations are important confounders. The general consensus now is that excessive hyperglycaemia (>10 mmol/L) and severe hypoglycaemia (<2·2 mmol/L) should be avoided in critically ill adults. If adequate blood glucose meters and clinically validated protocols for insulin-dosing are available, targeting of blood glucose concentrations to less than 8 mmol/L (moderate glycaemic control), while avoiding mild hypoglycaemia (<3·9 mmol/L), is a reasonable strategy in adult patients who are critically ill. This recommendation is not based on findings from randomised controlled trials, but merely represents a very common, pragmatic approach by physicians at the bedside. As a result of the few properly validated technologies for tighter blood glucose control, targeting blood glucose concentrations to less than 6 mmol/L is not recommended, because its risk-to-benefit ratio becomes questionable. Because blood glucose control in the target of adult ranges does not improve patient outcomes for children in the intensive care unit, glucose management in this patient population should be limited to avoid excessive hyperglycaemia (>10 mmol/L).

Blood glucose control for patients with acute coronary syndromes in Qatar

Background: Blood glucose is known to be elevated in patients presenting with acute coronary syndromes. However a gap in knowledge exists regarding effective management strategies once admitted to acute care units. It is also unknown what factors (if any) predict elevated glucose values during initial presentation. Objectives: Objectives of the study were to characterize blood glucose control in patients admitted to the cardiac care unit (CCU) in Qatar and to determine predictive factors associated with high glucose levels (>10 mmol/l) on admission to the CCU. Setting: All data for this study were obtained from the CCU at Heart Hospital in Doha, Qatar. Method: A retrospective chart review was completed for patients admitted to the CCU in Qatar from October 1st, 2012 to March 31st, 2013, of which 283 were included. Baseline characteristics (age, gender, nationality, medical history, smoking status, type of acute coronary syndrome), capillary and lab blood glucose measurements, and use of insulin were extracted. Time spent in glucose ranges of <4, 4 to <8, 8 to <10, and >10 mmol/1 was calculated manually. Univariate and multivariate logistic regression were performed to assess factors associated with high glucose on admission. The primary analysis was completed with capillary data and a sensitivity analysis was completed using laboratory data. Main outcome measure: Blood glucose values measured on admission and throughout length of stay in the CCU. Results: Capillary blood glucose data showed majority of time was spent in the range of >10 mmol/l (41.95%), followed by 4–8 mmol/l (35.44%), then 8–10 mmol/l (21.45%), and finally <4 mmol/l (1.16%). As a sensitivity analysis, laboratory data showed very similar findings. Diabetes, hypertension, and non-smoker status predicted glucose values >10 mmol/l on admission (p < 0.05) in a univariate analysis but only diabetes remained significant in a multivariate model (OR 23.3; 95% CI, 11.5–47.3). Conclusion: Diabetes predicts high glucose values on hospital admission for patients with ACS and patients are not being adequately controlled throughout CCU stay.

Elective percutaneous coronary intervention: the relationship between preprocedural blood glucose levels and periprocedural myocardial injury

Regardless of the diabetic status of patients with coronary artery disease, hyperglycemia and hypoglycemia are adversely associated with cardiovascular events. The relationship between glucose levels and increased mortality risk in acute myocardial infarction has been shown through various glucose metrics; however, there is a dearth of multivariate analysis of the relationship between elective coronary angioplasty and preprocedural blood glucose levels. We evaluated the relationship between preprocedural blood glucose levels and myocardial injury in 1,012 consecutive patients who underwent elective percutaneous coronary angioplasty. The patients were classified into 4 glycemic groups on the basis of blood glucose levels measured immediately before the procedure: hypoglycemic, euglycemic, mildly hyperglycemic, and hyperglycemic. Samples for troponin I and creatine kinase-MB fraction were collected before each procedure and at 8, 16, and 24 hours after each procedure. Bivariate analysis revealed that postprocedural troponin I levels were significantly higher in the hyperglycemic group (P=0.027). Although postprocedural levels of creatine kinase-MB fraction rose insignificantly in the hypoglycemic patients, our results showed that these patients were more likely to have postprocedural levels 2 to 5 times the upper limit of normal (P=0.013). We tentatively conclude that abnormally low preprocedural plasma glucose levels-together with a recent history of smoking-are associated with an increased incidence of periprocedural myocardial injury in patients undergoing elective percutaneous coronary intervention.

The prognostic role of in-hospital peak glycemia in stemi patients with and without diabetes

Due to the lack of appropriately designed randomized trials, the definitive answer in regard to the prognostic role of in-hospital glucose values in patients with AMI is lacking. We prospectively assessed the prognostic role of in-hospital peak glycemia (≤1.40, 141-180 and >180 g/l) in 611 consecutive STEMI patients (diabetic and without previously known diabetes) submitted to percutaneous coronary intervention. One hundred and fifteen (18.8%) were diabetic and the remaining 496 (81.2%) without previously known diabetes. At multivariable logistic regression analysis, peak glycemia was an independent predictor for in-ICCU death in the overall population and in patients without previously known diabetes. At follow-up, in the overall population (as well as in diabetic and non-diabetic patients), patients with peak glycemia >1.8 g/l showed the lowest survival rate, those with peak glycemia <1.4 g/l the highest and patients with peak glycemia >1.4 and <1.8 g/l intermediate survival rates. In-hospital peak glycemia is an independent predictor for early death in patients without previously known diabetes, but not in diabetic STEMI patients. At follow-up, in-hospital peak glycemia is able to affect long-term survival in diabetic and non-diabetic patients. Our data underscore strongly suggest that different glucose targets and thresholds may be pursued in diabetic and non-diabetic STEMI patients.

Admission hyperglycemia and acute myocardial infarction: outcomes and potential therapies for diabetics and nondiabetics

Hyperglycemia, in both diabetic and nondiabetic patients, has a significant negative impact on the morbidity and mortality of patients presenting with an acute myocardial infarction (AMI). Contemporary evidence indicates that persistent hyperglycemia after initial hospital admission continues to exert negative effects on AMI patients. There have been a number of studies demonstrating the benefit of tight glucose control in patients presenting with AMI, but a lack of convincing clinical data has led to loose guidelines and poor implementation of glucose targets for this group of patients. The CREATE-ECLA study, which hypothesized that a fixed high dose of glucose, insulin, and potassium (GIK) would change myocardial substrate utilization from free fatty acids to glucose and therefore protect ischemic myocardium, failed to demonstrate improved clinical outcomes in AMI patients. Studies that specifically investigated intensive insulin therapy, including DIGAMI-2 and HI-5, also failed to improve clinical outcomes such as mortality. There are a number of reasons that these trials may have fallen short, including the inability to reach glucose targets and inadequate power. There is now a need for a large placebo-controlled randomized trial with an adequate sample size and adherence to glucose targets in order to establish the benefit of treating hyperglycemia in patients presenting with AMI.

Glucose control in acute myocardial infarction: a pilot randomized study controlled by continuous glucose monitoring system comparing the use of insulin glargine with standard of care

BACKGROUND

This pilot study aimed to verify if glycemic control can be achieved in type 2 diabetes patients after acute myocardial infarction (AMI), using insulin glargine (iGlar) associated with regular insulin (iReg), compared with the standard intensive care unit protocol, which uses continuous insulin intravenous delivery followed by NPH insulin and iReg (St. Care).

PATIENTS AND METHODS

Patients (n=20) within 24 h of AMI were randomized to iGlar or St. Care. Therapy was guided exclusively by capillary blood glucose (CBG), but glucometric parameters were also analyzed by blinded continuous glucose monitoring system (CGMS).

RESULTS

Mean glycemia was 141±39 mg/dL for St. Care and 132±42 mg/dL for iGlar by CBG or 138±35 mg/dL for St. Care and 129±34 mg/dL for iGlar by CGMS. Percentage of time in range (80-180 mg/dL) by CGMS was 73±18% for iGlar and 77±11% for St. Care. No severe hypoglycemia (≤40 mg/dL) was detected by CBG, but CGMS indicated 11 (St. Care) and seven (iGlar) excursions in four subjects from each group, mostly in sulfonylurea users (six of eight patients).

CONCLUSIONS

This pilot study suggests that equivalent glycemic control without increase in severe hyperglycemia may be achieved using iGlar with background iReg. Data outputs were controlled by both CBG and CGMS measurements in a real-life setting to ensure reliability. Based on CGMS measurements, there were significant numbers of glycemic excursions outside of the target range. However, this was not detected by CBG. In addition, the data indicate that previous use of sulfonylurea may be a potential major risk factor for severe hypoglycemia irrespective of the type of insulin treatment.