Glucose-insulin-potassium and reperfusion in acute myocardial infarction: rationale and design of the Glucose-Insulin-Potassium Study-2 (GIPS-2)

Cardiac Metabolism, Reprogramming, and Diseases

Cardiovascular diseases (CVD) account for the largest bulk of deaths worldwide, posing a massive burden on societies and the global healthcare system. Besides, the incidence and prevalence of these diseases are on the rise, demanding imminent action to revert this trend. Cardiovascular pathogenesis harbors a variety of molecular and cellular mechanisms among which dysregulated metabolism is of significant importance and may even proceed other mechanisms. The healthy heart metabolism primarily relies on fatty acids for the ultimate production of energy through oxidative phosphorylation in mitochondria. Other metabolites such as glucose, amino acids, and ketone bodies come next. Under pathological conditions, there is a shift in metabolic pathways and the preference of metabolites, termed metabolic remodeling or reprogramming. In this review, we aim to summarize cardiovascular metabolism and remodeling in different subsets of CVD to come up with a new paradigm for understanding and treatment of these diseases.

An Overview of the Molecular Mechanisms Associated with Myocardial Ischemic Injury: State of the Art and Translational Perspectives

Cardiovascular disease is the leading cause of death in western countries. Among cardiovascular diseases, myocardial infarction represents a life-threatening condition predisposing to the development of heart failure. In recent decades, much effort has been invested in studying the molecular mechanisms underlying the development and progression of ischemia/reperfusion (I/R) injury and post-ischemic cardiac remodeling. These mechanisms include metabolic alterations, ROS overproduction, inflammation, autophagy deregulation and mitochondrial dysfunction. This review article discusses the most recent evidence regarding the molecular basis of myocardial ischemic injury and the new potential therapeutic interventions for boosting cardioprotection and attenuating cardiac remodeling.

Targeting fatty acid and carbohydrate oxidation--a novel therapeutic intervention in the ischemic and failing heart

Cardiac ischemia and its consequences including heart failure, which itself has emerged as the leading cause of morbidity and mortality in developed countries are accompanied by complex alterations in myocardial energy substrate metabolism. In contrast to the normal heart, where fatty acid and glucose metabolism are tightly regulated, the dynamic relationship between fatty acid β-oxidation and glucose oxidation is perturbed in ischemic and ischemic-reperfused hearts, as well as in the failing heart. These metabolic alterations negatively impact both cardiac efficiency and function. Specifically there is an increased reliance on glycolysis during ischemia and fatty acid β-oxidation during reperfusion following ischemia as sources of adenosine triphosphate (ATP) production. Depending on the severity of heart failure, the contribution of overall myocardial oxidative metabolism (fatty acid β-oxidation and glucose oxidation) to adenosine triphosphate production can be depressed, while that of glycolysis can be increased. Nonetheless, the balance between fatty acid β-oxidation and glucose oxidation is amenable to pharmacological intervention at multiple levels of each metabolic pathway. This review will focus on the pathways of cardiac fatty acid and glucose metabolism, and the metabolic phenotypes of ischemic and ischemic/reperfused hearts, as well as the metabolic phenotype of the failing heart. Furthermore, as energy substrate metabolism has emerged as a novel therapeutic intervention in these cardiac pathologies, this review will describe the mechanistic bases and rationale for the use of pharmacological agents that modify energy substrate metabolism to improve cardiac function in the ischemic and failing heart. This article is part of a Special Issue entitled: Mitochondria and Cardioprotection.

The role of insulin therapy and glucose normalisation in patients with acute coronary syndrome

Patients with acute myocardial infarction (AMI) and diabetes mellitus, as well as patients admitted with elevated blood glucose without known diabetes, have impaired outcome. Therefore intensive glucose-lowering therapy with insulin (IGL) has been proposed in diabetic or hyperglycaemic patients and has been shown to improve survival and reduce incidence of adverse events. The current manuscript provides an overview of randomised controlled trials investigating the effect of IGL. Furthermore, systematic glucose-insulin-potassium infusion (GIK) has been studied to improve outcome after AMI. In spite of positive findings in some early studies, GIK did not show any beneficial effects in recent clinical trials and thus this concept has been abandoned. While IGL targeted to achieve normoglycaemia improves outcome in patients with AMI, achievement of glucose regulation is difficult and carries the risk of hypoglycaemia. More research is needed to determine the optimal glucose target levels in AMI and to investigate whether computerised glucose protocols and continuous glucose sensors can improve safety and efficacy of IGL.

Insulin therapy in acute coronary syndromes: an appraisal of completed and ongoing randomised trials with important clinical end points

Insulin therapy was first proposed as an adjunctive therapy in patients with acute coronary syndromes (ACS) in the 1960s. Since then, numerous randomised clinical trials have been conducted to determine the efficacy and to define the role of insulin therapy in ACS. This review will discuss: 1) completed trials of insulin therapy in ACS, including both glucose-insulin-potassium (GIK) approaches and non-GIK approaches; 2) trials of insulin therapy in critically ill non-ACS patients and the lessons from these trials that can be applied to trials of insulin in ACS patients; and 3) a summary of ongoing and planned trials of insulin in ACS patients.

Glycemic control and prevention of perioperative infection

PURPOSE OF REVIEW

Hyperglycemia is common during perioperative management of surgical and critically ill patients. There is extensive ongoing study of detrimental effects associated with hyperglycemia, with several remaining unanswered questions. This review discusses recent literature on tight glucose control with insulin therapy and its effects in prevention and management of infection.

RECENT FINDINGS

Hyperglycemia affects multiple pathways of the immune system, resulting in decreased phagocytic and chemotactic functions in neutrophils and monocytes, as well as increased rates of apoptosis of the former and decreased ability of the latter to present antigen. Intensive insulin therapy has been shown to counteract many of these deleterious effects. Clinically, the benefits of tight glucose control have been evaluated in different patient populations with conclusions that remain varied. Hypoglycemia as a complication of tight glucose control continues to be an issue and has led to discontinuation of two large-scale studies. The clinical relevance of hypoglycemic events remains unclear.

SUMMARY

Hyperglycemia impairs the cellular immune system, stimulates inflammatory cytokines, and affects the microcirculation, thus increasing risk for infection and preventing normal wound healing. Additional investigation is needed to define appropriate patient populations and to develop effective treatment strategies for preventing perioperative morbidity.

Intensive insulin therapy for acute hyperglycemia

There is growing evidence that control of hyperglycemia in the critically ill patient improves outcome. Normalizing blood glucose levels decreases the risk of developing sepsis, end-organ damage, and hospital mortality. Critical care clinicians must be familiar with current and benchmark research supporting control of hyperglycemia and use this knowledge to ensure appropriate application of evidence-based practice for decreasing or preventing complications in the critically ill patient. This article describes the effects of hyperglycemia and discusses the evidence supporting tight glycemic control in such patients. The necessary steps to implement an intensive insulin therapy protocol for control of acute hyperglycemia are detailed.

Intensive insulin therapy in the intensive cardiac care unit

Treatment in the intensive cardiac care unit (ICCU) enables rigorous control of vital parameters such as heart rate, blood pressure, body temperature, oxygen saturation, serum electrolyte levels, urine output and many others. The importance of controlling the metabolic status of the acute cardiac patient and specifically the level of serum glucose was recently put in focus but is still underscored. This review aims to explain the rationale for providing intensive control of serum glucose levels in the ICCU, especially using intensive insulin therapy and summarizes the available clinical evidence suggesting its effectiveness.

One year outcomes after glucose-insulin-potassium in ST elevation myocardial infarction. The Glucose-insulin-potassium study II

BACKGROUND

There are conflicting data concerning the effect of treatment with glucose-insulin-potassium (GIK) in ST segment elevation myocardial infarction (STEMI). Early studies showed beneficial effects of GIK, however, recent large sample size trials did not confirm this, or suggested only benefits in patients without heart failure. We aimed to evaluate long-term effects of GIK in patients with STEMI without signs of heart failure, all treated with reperfusion therapy.

METHODS

From August 2003 to December 2004, 889 STEMI patients without signs of heart failure were randomized to standard care (N=445) or additional GIK infusion (N=444). Glucose-potassium (20% glucose with 80 mmol potassium/l) was infused at 2 ml/kg body weight per hour for 12 h through a peripheral line. Short-acting insulin was started according to admission glucose and adjusted based on hourly measured glucose. Clinical end points were of number of death, reinfarction and revascularization at 1 year.

RESULTS

One year follow-up was available in 864 patients (97.2%), 432 in the GIK group and 432 in the control group. Mortality rate was 5.3% in GIK and 3.9% in control patients, p=0.33. Rates of reinfarction and revascularization 4.6% vs. 4.6% and 15.5% and 15.0%, in GIK vs. control patients.

CONCLUSION

In patients with STEMI without signs of heart failure treated with reperfusion therapy, GIK therapy offers no clinical benefit at 1 year.

Haemodynamic patterns in ST-elevation myocardial infarction: incidence and correlates of elevated filling pressures

OBJECTIVES.: We sought to study the incidence and clinical correlates of elevated filling pressures in ST-elevation myocardial infarction (STEMI) patients, without physical signs of heart failure and treated with primary coronary angioplasty. BACKGROUND.: Haemodynamic data, as measured with a Swan-Ganz catheter, are not routinely obtained in STEMI patients. At admission, low blood pressure, increased heart rate, sweating, increased respiration rate, rales, oedema, and a third heart sound are indicative of heart failure. METHODS.: All consecutive STEMI patients were monitored by a Swan-Ganz catheter and central venous pressure (CVP), pulmonary capillary wedge pressure (PCWP), pulmonary artery pressure (PAS) and cardiac index (CI) were measured. To investigate the clinical correlates of the haemodynamic status patients were classified according to previously defined haemodynamic criteria. RESULTS.: We studied 90 patients, aged 60.5+/-13.1 year, 76% were male. Mortality at 30 days was 2/90 (2.2%). Patients with impaired haemodynamics presented later and had larger myocardial infarct sizes. CVP, PCWP and PAS were above normal in 36 (40%) patients. CONCLUSION.: A large proportion of STEMI patients without physical signs of heart failure have elevation of right- as well as left-sided cardiac filling pressures. (Neth Heart J 2007;15:95-9.).

Glucose, insulin and myocardial ischaemia

PURPOSE OF REVIEW

The importance of glucose metabolism and insulin therapy during myocardial ischaemia is increasingly being investigated. Insulin is used to achieve a tight glucose control or as part of glucose-insulin-potassium therapy. We have reviewed (1) the physiological and physiopathological consequences of hyperglycaemia focusing on potential machanisms of myocardial ischaemia, (2) the effects of insulin on vascular tone, on the release of free fatty acids, on inflammatory pathways, on the switch of energy source and on apoptosis, and (3) clinical data reporting the effects of intensive insulin therapy and glucose-insulin-potassium solutions during myocardial ischaemia and ischaemic heart failure.

RECENT FINDINGS

In addition to its known toxic cellular effects, hyperglycaemia increases the activity of inducible nitric oxide synthase and promotes inflammation. Conversely insulin exerts anti-inflammatory and anti-apoptotic effects. Glucose-insulin-potassium solutions could improve survival after acute myocardial infarction or after surgery, according to recent meta-analyses, but confirmation of these data is eagerly awaited.

SUMMARY

Hyperglycaemia is toxic, while insulin is beneficial during acute myocardial ischaemia. Some recent evidence confirms a substantial benefit of insulin administered either alone to achieve a tight glucose control or as a component of glucose-insulin-potassium therapy. Further research is needed to confirm that tendency and to define the threshold of tight glucose control.

Glucose-insulin-potassium infusion in acute myocardial infarction: a hemodynamic study

BACKGROUND

In this study, we investigated whether adjunction of glucose-insulin-potassium (GIK) infusion to primary percutaneous coronary intervention (PCI) affects hemodynamics in patients with an acute myocardial infarction.

METHODS

Hemodynamic measurements were performed in a subset of patients (n = 81) in the GIPS 2, starting immediately after PCI and continued for 12 hours.

RESULTS

Cardiac index values were stable in both groups. During the first measurements, diastolic pulmonary artery pressure and the pulmonary capillary wedge pressure (PCWP) were significantly higher in the non-GIK group (diastolic pulmonary artery pressure 15 +/- 5 vs 18 +/- 7 mm Hg, P = .028 and PCWP 14 +/- 6 vs 18 +/- 7 mm Hg, P = .030). There was a decrease in PCWP from 18 +/- 7 to 15 +/- 6 mm Hg in the non-GIK group during the first 6 hours, whereas the pressures remained at 14 +/- 6 mm Hg in the GIK group. This difference in pattern of change did not reach statistical significance in the analysis of the interaction of PCWP by GIK group (P = .065).

CONCLUSIONS

Glucose-insulin-potassium infusion as adjunctive therapy to PCI in patients with acute myocardial infarction, without overt signs of heart failure, did not negatively affect hemodynamics.