Effects of glucose and fatty acids on myocardial ischaemia and arrhythmias

Hospital management of diabetes

The evidence continues to strengthen our understanding that improved glycemic control with the use of insulin therapy may significantly improve morbidity and mortality in hospitalized patients with hyperglycemia, with or without a previous diagnosis of diabetes. However, many questions remain concerning the impact and relative contributions of blood glucose and insulin per se. Nevertheless, the publication of numerous and consistent studies have made it clear that the topic of glycemic management in the hospital requires a larger priority among clinicians caring for these patients. The recently published guidelines by the American Association of Clinical Endocrinologists are the first formal recommendations on this topic,but national guidelines for blood glucose levels cannot take into account all of the different challenges facing different hospitals. This suggests that each institution will require individualization of protocols even though the ultimate metabolic goals are identical. Furthermore, it is not realistic to expect those unfamiliar with diabetes therapy to appreciate all of the nuances and vagaries of insulin treatment. Like any medical treatment, a significant amount of time will need to be invested by the providers involved with the.care of these patients before a mastery of the therapy can be achieved. Nevertheless, because the rewards to our patients can be significant, we need to strive to improve the systems where we work. Individual clinicians with vast experience in diabetes care cannot be successful for the inpatient with diabetes unless the hospital has systems in place to effectively and efficiently facilitate the management of the metabolic needs of this population. The main challenge now is the safe and effective implementation of these guidelines in both small and large hospitals given the limited level of re-sources available in today's medical environment. Therefore, our single most important recommendation is to ensure that all clinicians involved in the management of these patients are in agreement about general philosophies of diabetes management. We would recommend that there are "champions" for each discipline: endocrinology, cardiology, anesthesiology, surgery, nursing,and pharmacy, all of which have developed hospital-specific guidelines for glycemic management. These recommendations can be slowly adapted, one unit at a time, until the entire hospital has transitioned to a more "diabetes-friendly" environment. The ultimate goal of well-controlled glycemia with minimal hypoglycemia should be possible for most hospitals, and we hope this review will assist clinicians in achieving this objective. We await additional outcome research with carefully controlled studies to confirm the value of these recommendations at different levels of glycemic control. We believe that we can already state with confidence that the preliminary evidence shows that, like outpatient diabetes management,metabolic control matters during acute illness.

High-dose glucose-insulin-potassium treatment reduces myocardial apoptosis in patients with acute myocardial infarction

BACKGROUND

Several clinical trials have suggested that a metabolic cocktail of glucose-insulin-potassium (GIK) decreases mortality rates in patients with acute myocardial infarction (AMI). It has also been reported that Fas-mediated apoptosis plays an important role in ischaemic/reperfusion injury in the rat model. This study was designed to evaluate the interaction of ischaemic/reperfusion and reperfusion therapy coadministered with high-dose GIK treatment on soluble Fas/APO-1 (sFas) and Fas ligand (sFasL) plasma concentration in patients with AMI.

MATERIALS AND METHODS

Seventy-four patients presenting with AMI who underwent reperfusion therapy were randomized into a GIK group (n = 35) receiving high-dose GIK for 24 h or a vehicle group (n = 39). Thirty-four control subjects were also enrolled in the present study. Strepavidin-biotin ELISA was used to determine the soluble sFas and sFasL plasma concentration at baseline, 24 h (h), 3 day (d), 7 d and 14 d.

RESULTS

Soluble Fas and sFas-L serum concentrations ([sFas] and [sFas-L]) of patients with AMI were significantly elevated at baseline as compared with normal controls (NCs; P < 0.01 vs. NC). The sFas in the GIK and vehicle groups markedly decreased 24 h after the GIK infusion (10.7-->5.9 ng mL(-1) and 9.7-->6.5 ng mL(-1); P < 0.01 vs. baseline) and then increased during the 3-7-d period (5.9-->12.1 ng mL(-1) and 6.5-->11.1 ng mL(-1); P < 0.01 vs. 24 h). The GIK group demonstrated reduced sFas (12.1-->5.9 ng mL(-1)) at 14 d (P < 0.01 vs. 7 d), with no concomitant changes in the vehicle group. The sFas-L in the GIK and vehicle groups was not significant different during the 14-d period.

CONCLUSIONS

These results indicate that the sFas and sFasL in patients with AMI increased significantly compared with NC. Owing to the cardioprotective effects reported here and by others, a high-dose GIK infusion co-administered with the timely re-establishment of nutritive perfusion should be strongly considered as a treatment of choice for AMI. Additionally, sFas may be a valuable marker of the physiological response to ischaemic/reperfusion injury and reperfusion associated with high-dose GIK treatment.

Cardiac autonomic activity and Type II diabetes mellitus

CAN (cardiac autonomic neuropathy) is a common complication of diabetes. Meta-analyses of published data demonstrate that reduced cardiovascular autonomic function, as measured by heart rate variability, is strongly associated with an increased risk of silent myocardial ischaemia and mortality. A major problem in ischaemia-induced impairment of vascular performance in the diabetic heart is unrecognized cardiac sympathetic dysfunction. Determining the presence of CAN is based on a battery of autonomic function tests and techniques such as SPECT (single-photon emission computed tomography) and PET (positron emission tomography). Nevertheless, spectral analysis of heart rate variability seems to remain the primary technique in evaluating CAN, due to its low cost, easy use and good intra-individual reproducibility.

Perioperative blood glucose control during adult coronary artery bypass surgery

Coronary artery bypass graft (CABG) procedures are among the most frequently performed surgical procedures in the United States. People with cardiovascular disease who also have diabetes have a greater risk of poor outcomes after CABG procedures than patients who do not have diabetes. This literature review examines current information regarding perioperative blood glucose (BG) control. It emphasizes BG control in adults during the hypothermic period of cardiopulmonary bypass. Hyperglycemia, not the diagnosis of diabetes, significantly increases the risk of adverse clinical outcomes, longer hospitalizations, and increased health care costs.

Thiazolidinediones and Insulin

The range of therapeutic modalities to treat type 2 diabetes mellitus has broadened in recent years. Biguanides and thiazolidinediones are the two currently available classes of anti-hyperglycemic agents with insulin-sensitizing properties. Thiazolidinediones, in particular, have received much attention, not only for the well documented hepatotoxicity of troglitazone that led to its removal from the market in 2000, but also for the emerging data that support the beneficial effects of the thiazolidinedione class of drugs on beta-cell rejuvenation and cardiovascular risk reduction. In the US, thiazolidinediones are indicated either as monotherapy or in combination with a sulfonylurea, metformin, or insulin in cases where diet, exercise, and a single drug fail. In contrast, the UK National Institute for Clinical Excellence included in its re-appraisal of 'glitazones' in August 2003 the continued exclusion from licensed use in the UK of combination therapy with thiazolidinediones and insulin. When added to insulin therapy, thiazolidinediones appear to effectively lower glucose levels and reduce insulin dosage in clinical trials involving individuals with poorly controlled type 2 diabetes. However, weight gain, hypoglycemia, and fluid retention pose problems in certain patients. The fluid retention may exacerbate or even precipitate congestive heart failure, which usually necessitates discontinuation of the drug. Risk stratification and careful management of patients at risk for heart failure, including those taking insulin concomitantly, allow healthcare providers to safely administer combination therapy with thiazolidinediones in patients with type 2 diabetes. Hepatic toxicity with currently available thiazolidinediones has been found to be minimal overall.

Fatty acid oxidation inhibitors in the management of chronic complications of atherosclerosis

Ischemic heart disease is characterized by a modification of the normal energy balance of the heart. During and following an ischemic event, circulating fatty acids are elevated, resulting in the acceleration of fatty acid oxidation at the expense of glucose oxidation. Despite the reduction in glucose oxidation, the rate of glycolysis increases, leading to an uncoupling of glucose metabolism. This results in the accumulation of metabolic byproducts, which leads to a decrease in cardiac efficiency. A novel therapeutic strategy involves improving the efficiency of oxygen utilization by the ischemic heart by the modulation of energy metabolism. This can be achieved by a reduction in the levels of circulating fatty acids using beta-blockers, glucose-insulin-potassium infusions, and nicotinic acid. Alternatively, fatty acid oxidation can be directly inhibited using trimetazidine, ranolazine, or glucose oxidation directly activated using dichloroacetate, which significantly improves the efficiency of the heart.

Improving glycemic control in the cardiothoracic intensive care unit: Clinical experience in two hospital settings

OBJECTIVE

Recent studies suggest that strict perioperative glycemic control improves clinical outcomes after cardiothoracic surgery. However, optimal methods and targets for controlling blood glucose (BG) levels in this setting have not been established. Currently published intensive insulin infusion protocols (IIPs) have important practical limitations, which may affect their utility. In this article, the authors present their experience with a safe, effective, nurse-driven IIP, which was implemented simultaneously in 2 cardiothoracic intensive care units (CTICUs).

DESIGN

Prospective cohort study.

SETTING

Tertiary referral hospital and community teaching hospital.

PARTICIPANTS

CTICU patients.

INTERVENTIONS

A standardized, intensive IIP was used for all patients admitted to both CTICUs. Hourly BG levels, relevant baseline variables, and clinical interventions were collected prospectively from the active hospital chart and CTICU nursing records.

MEASUREMENTS AND MAIN RESULTS

The IIP was used 137 times in 118 patients. The median time required to reach target BG levels (100-139 mg/dL) was 5 hours. Once BG levels decreased below 140 mg/dL, 58% of 2,242 subsequent hourly BG values fell within the narrow target range, 73% within a "clinically desirable" range of 80 to 139 mg/dL, and 94% within a "clinically acceptable" range of 80 to 199 mg/dL. Only 5 (0.2%) BG values were less than 60 mg/dL, with no associated adverse clinical events.

CONCLUSIONS

The IIP safely and effectively improved glycemic control in 2 CTICUs, with minimal hypoglycemia. Based on prior studies showing the benefits of strict glycemic control, the implementation of this IIP should help to reduce morbidity and mortality in CTICU patients.

The endocrine system during sepsis

Endocrinopathy during sepsis can manifest as hyperglycemia and insulin resistance or as insufficient production of either adrenal corticosteroids or vasopressin. The results of a recent large clinical trial have demonstrated that tight glycemic control with insulin can confer survival benefit to selected intensive care unit patients. Relative impairment of adrenocortical reserve has been suggested to be an important contributor to the pathogenesis of shock in sepsis. Replacement doses of glucocorticoids and mineralocorticoids have been associated with improved survival in the subset of patients with blunted results on adrenocorticotropin hormone stimulation tests. Posterior pituitary production of vasopressin is diminished in septic shock while sensitivity to its vasopressor effects is enhanced. Clinical trials are underway to determine whether administration of vasopressin can improve outcomes in patients with septic shock. Whether the euthyroid sick syndrome represents an adaptive or a maladaptive response to severe illness remains unclear.

Early postoperative hyperglycaemia is not a risk factor for infectious complications and prolonged in-hospital stay in patients undergoing oesophagectomy: a retrospective analysis of a prospective trial

INTRODUCTION

Treating hyperglycaemia in hospitalized patients has proven to be beneficial, particularly in those with obstructive vascular disease. In a cohort of patients undergoing resection for oesophageal carcinoma (a group of patients with severe surgical stress but a low prevalence of vascular disease), we investigated whether early postoperative hyperglycaemia is associated with increased incidence of infectious complications and prolonged in-hospital stay.

METHODS

Postoperative glucose values up to 48 hours after surgery were retrieved for 151 patients with American Society of Anesthesiologists class I or II who had been previously included in a randomized trial conducted in a tertiary referral hospital. Multivariate regression analysis was used to define the independent contribution of possible risk factors selected by univariate analysis.

RESULTS

In univariate regression analysis, postoperative glucose levels were associated with increased length of in-hospital stay (P < 0.001) but not with infectious complications (P = 0.21). However, postoperative glucose concentration was not found to be an independent risk factor for prolonged in-hospital stay in multivariate analysis (P = 0.20).

CONCLUSION

Our data indicate that postoperative hyperglycaemia is more likely to be a risk marker than a risk factor in patients undergoing highly invasive surgery for oesophageal cancer. We hypothesize that patients with a low prevalence of vascular disease may benefit less from intensive insulin therapy.

Can n-3 PUFA reduce cardiac arrhythmias? Results of a clinical trial

Dietary n-3 polyunsaturated fatty acids (PUFA) derived from fatty fish or fish oil may reduce the incidence of lethal myocardial infarction and sudden cardiac death. This might be due to a prevention of fatal cardiac arrhythmias. So far, however, only few clinical data are available being adequate to define indications for an antiarrhythmic treatment with n-3 PUFA. In a randomized, double-blind, placebo-controlled study 65 patients with cardiac arrhythmias without coronary heart disease or heart failure were subdivided into 2 groups. One group (n = 33) was supplemented with encapsulated fish oil (3g/day, equivalent to 1g/day of n-3 PUFA) over 6 months. The other group (n = 32) was given 3g/day of olive oil as placebo. In the fish oil group a decrease of serum triglycerides, total cholesterol, LDL cholesterol, plasma free fatty acids and thromboxane B2 as well as an increase of HDL cholesterol were observed. Moreover, a reduced incidence of atrial and ventricular premature complexes, couplets and triplets were documented. Accordingly, higher grades of Lown's classification switched to lower grades at the end of the dietary period. No changes were seen in the placebo group. The data indicate an antiarrhythmic action of n-3 PUFA under conditions of clinical practice which might help to explain the reduced incidence of fatal myocardial infarction and sudden cardiac death in cohorts on a fish-rich diet or supplemented with n-3 PUFA. Further studies elucidating the possible link between the reduced incidence of cardiac arrhythmias and sudden cardiac death by dietary intake of n-3 PUFA are warranted.

The effect of diabetes on heart rate and other determinants of myocardial oxygen demand in acute coronary syndromes

AIMS

To compare major determinants of myocardial oxygen demand (heart rate, blood pressure and rate pressure product) in patients with and without diabetes admitted with acute coronary syndromes.

METHODS

A cross-sectional study of the relation between diabetes and haemodynamic indices of myocardial oxygen demand in 2542 patients with acute coronary syndromes, of whom 1041 (41.0%) had acute myocardial infarction and 1501 (59.0%) unstable angina.

RESULTS

Of the 2542 patients, 701 (27.6%) had diabetes. Major haemodynamic determinants of myocardial oxygen demand were higher in patients with than without diabetes: heart rate 80.0 +/- 20.4 vs. 75.2 +/- 19.2 beats/minute (P < 0.0001); systolic blood pressure 147.3 +/- 30.3 vs. 143.2 +/- 28.5 mmHg (P = 0.002); rate-pressure product 11533 +/- 4198 vs. 10541 +/- 3689 beats/minute x mmHg (P < 0.0001). Multiple regression analysis confirmed diabetes as a significant determinant of presenting heart rate [multiplicative coefficient (MC) 1.05; 95% confidence interval (CI) 1.03-1.07; P < 0.0001], rate pressure product (MC 1.09; CI 1.05-1.12; P < 0.0001) and systolic blood pressure, which was estimated to be 3.9 mmHg higher than in patients without diabetes (P=0.003). These effects of diabetes were independent of a range of baseline variables including acute left ventricular failure and mode of presentation (unstable angina or myocardial infarction).

CONCLUSIONS

In acute coronary syndromes, heart rate and other determinants of myocardial oxygen demand are higher in patients with than without diabetes, providing a potential contributory mechanism of exaggerated regional ischaemia in this high-risk group.

Reversal of Glucose-Insulin-Potassium-Induced Hyperglycemia by Aggressive Insulin Treatment in Postoperative Heart Failure

Metabolic support with glucose-insulin-potassium (GIK) significantly reduces the morbidity and mortality of patients in cardiogenic shock after hypothermic ischemic arrest for aortocoronary bypass surgery. However, a small subset of these patients develops postoperative insulin resistance regardless of their preoperative diabetic status. Whether GIK directly contributes to higher mortality in these patients is unknown. We reviewed the records of 322 patients whose treatment for postoperative cardiogenic shock included GIK. Ten patients (3%) had postoperative hyperglycemia (serum glucose > or =250 mg/dl or 13.9 mmol/l) due to insulin resistance. These were compared to randomly selected GIK-treated, insulin-responsive patients (n = 10) and non-GIK-treated patients (n = 10) for comparison. The insulin-resistant patients required increasing amounts of regular insulin up to 130 U/h until blood glucose levels fell below 250 mg/dl. However, short-term outcomes (IABP support time, length of stay in ICU, 7-day mortality) for insulin- resistant patients were indistinguishable from those for insulin-responsive patients. These data indicate that postoperative iatrogenic hyperglycemia in patients after cardiopulmonary bypass may not be detrimental per se and is reversible when treated with supplemental insulin.

Ischemic heart disease and congestive heart failure in diabetic patients

Ischemic heart disease and heart failure are major contributors to the morbidity and mortality associated with diabetes mellitus. With growing knowledge of how the metabolic derangements of diabetes contribute to the pathogenesis of cardiovascular disease, we must continuously refine our understanding of optimal screening and strategies for prevention and treatment for these interlinked disorders. This article summarizes our current understanding of ischemic heart disease and heart failure in patients with diabetes mellitus, highlighting gaps in our knowledge about the relationship between diabetes and cardiovascular disease. Special consideration is given to new strategies for treating the adverse effects of abnormal glucose metabolism on the cardiovascular system.

A randomized evaluation of the effects of glucose-insulin-potassium infusion on myocardial salvage in patients with acute myocardial infarction treated with reperfusion therapy

BACKGROUND

Intravenous glucose-insulin-potassium (GIK) may have a positive metabolic influence in patients with acute myocardial infarction (AMI) who receive reperfusion therapy. The objective of this randomized trial was to assess for the first time whether GIK improves myocardial salvage in patients with AMI.

METHODS

The Reevaluation of Intensified Venous Metabolic Support for Acute Infarct Size Limitation (REVIVAL) trial is a randomized, open-label study conducted among 312 patients with AMI. Patients were randomly assigned to either the GIK therapy group (n = 155) or the control group (n = 157). All patients were intended to receive reperfusion treatment, which was given in all but 5 patients (1.6%). The primary end point of the study was salvage index, measured as the proportion of initial perfusion defect (acute technetium-99m sestamibi scintigraphy) salvaged by therapy (follow-up scintigraphy performed after 7 to 14 days).

RESULTS

The primary end point of the study, the salvage index, was in median 0.50 (25th, 75th percentiles: 0.18, 0.87) in the GIK group and 0.48 (25th, 75th percentiles: 0.27, 0.78) in the control group (P =.96). By 6 months, the mortality rate was 5.8% in the GIK group and 6.4% in the control group (P =.85; relative risk, 0.92; 95% CI, 0.37 to 2.26). Subgroup analyses showed that GIK therapy was associated with increased salvage index only among diabetic patients (mean difference, 0.19; 95% CI, 0.01 to 0.37).

CONCLUSIONS

The routine use of GIK therapy in patients with AMI is not associated with enhanced myocardial salvage. This therapy appears to improve myocardial salvage only among diabetic patients.

Intensive Insulin Therapy for Critically III Patients

OBJECTIVE:

To evaluate the clinical outcomes of glycemic control of intensive insulin therapy and recommend its place in the management of critically ill patients.

DATA SOURCES:

Searches of MEDLINE (1966—March 2004) and Cochrane Library, as well as an extensive manual review of abstracts were performed using the key search terms hyperglycemia, insulin, intensive care unit, critically ill, outcomes, and guidelines and algorithms.

STUDY SELECTION AND DATA EXTRACTION:

All articles identified from the data sources were evaluated and deemed relevant if they included and assessed clinical outcomes.

DATA SYNTHESIS:

Mortality among patients with prolonged critical illness exceeds 20%, and most deaths are attributable to sepsis and multisystem organ failure. Hyperglycemia is common in critically ill patients, even in those with no history of diabetes mellitus. Maintaining normoglycemia with insulin in critically ill patients has been shown to improve neurologic, cardiovascular, and infectious outcomes. Most importantly, morbidity and mortality are reduced with aggressive insulin therapy. This information can be implemented into protocols to maintain strict control of glucose.

CONCLUSIONS:

Use of insulin protocols in critically ill patients improves blood glucose control and reduces morbidity and mortality in critically ill populations. Glucose levels in critically ill patients should be controlled through implementation of insulin protocols with the goal to achieve normoglycemia, regardless of a history of diabetes. Frequent monitoring is imperative to avoid hypoglycemia.

Retrospective analysis of the impact of a low glycaemic index diet on hospital stay following coronary artery bypass grafting: a hypothesis

OBJECTIVE

Glucose tolerance and insulin resistance influence medical outcome in subjects with coronary artery disease, these metabolic parameters also influence general perioperative surgical outcome. We hypothesize that glucose tolerance and insulin resistance can be favourably modified by reducing the glycaemic index of the diet.

DESIGN

The present study is a retrospective analysis of a low and high glycaemic index diet on glucose tolerance, insulin resistance and perioperative outcome, as assessed by the length of hospital stay following coronary artery bypass surgery. Thirty-five adults awaiting bypass surgery were randomized, for the 4 weeks prior to surgery, to either a low glycaemic index diet (17 subjects) or high glycaemic index diet (18 subjects). Glucose and insulin responses during a 75 g oral glucose tolerance test were assessed before and after dietary intervention and insulin-mediated glucose uptake was assessed in isolated adipocytes obtained at surgery.

RESULTS

The patients who consumed a low glycaemic diet had improved glucose tolerance and significantly greater in vitro adipocyte insulin sensitivity at the time of surgery compared with the high glycaemic diet group (78.87 +/- 10.64% versus 41.11 +/- 7%, respectively). The total length of stay in the patients on the low glycaemic diet was less than patients consuming the high glycaemic diet (7.06 +/- 0.38 days versus 9.53 +/- 1.44 days, P < 0.5).

CONCLUSION

This study provides further support that carbohydrate and fat metabolism influence cardiac outcome and provides new evidence that dietary modification prior to coronary artery bypass surgery can shorten hospital stay.

Effects of amino acid supplementation on left ventricular remodeling in patients with chronic heart failure with decreased systolic function and diabetes mellitus: rationale and design of a magnetic resonance imaging study

A considerable number of patients with reduced systolic function caused by primary or ischemic cardiomyopathy have viable and noncontractile myocardium. This may be related to numerous and perhaps overlapping factors, such as chronic ischemia (stunning/hibernation), neurohormonal abnormalities, oxidative stress, metabolic imbalances, and/or nutritional depletion. Changes in myocardial substrate utilization have adverse effects on the metabolism of the viable but noncontractile myocardium. Shifting the energy substrate preference away from fatty acids and replenishing the tricarboxylic acid cycle components via amino acids rather than via fatty acids would increase adenosine triphosphate production, with positive effects on cellular metabolism. A proposed study design is described and will be piloted through the Effects of Diatrofen on Myocardial Function in Patients with Chronic Heart Failure trial (D-CHF), an evaluation of an oral amino acid supplementation treatment in outpatients with heart failure.

Diabetic cardiomyopathy: a metabolic perspective

Patients with diabetes mellitus have a >3-fold increased risk of coronary ischemic events and congestive heart failure. Several hypotheses have been provided to explain the increased cardiac vulnerability in individuals with diabetes; among these are the metabolic abnormalities. Diabetes is associated with profound changes in cardiac metabolism, characterized by diminished glucose utilization, diminished rates of lactate oxidation, and increased use of fatty acids. Very few investigations have focused on amino acid disturbances at the level of the heart. This area of research is potentially relevant because cardiac amino acid alterations may not only result in a reduced energy reserve but could also lead to quantitative and qualitative abnormalities of contractile protein present in the diabetic heart.

Type 2 diabetes and intravenous thrombolysis outcome in the setting of ST elevation myocardial infarction

OBJECTIVE

There are conflicting results regarding the impact of type 2 diabetes on intravenous thrombolysis effectiveness during ST elevation myocardial infarction (STEMI). The present study, using a continuous 12-lead electrocardiogram, examined the possible association of type 2 diabetes with both acute intravenous thrombolysis effectiveness and long-term prognosis in this setting.

RESEARCH DESIGN AND METHODS

The study included 726 consecutive subjects (214 type 2 diabetic subjects) with STEMI who received intravenous thrombolysis in the first 6 h from index pain and were followed up for 3.5 years.

RESULTS

Type 2 diabetic subjects had significantly lower incidence of sustained > or = 50% ST recovery than nondiabetic subjects (P = 0.03). Additionally, the former required a significantly greater time interval through the achievement of this criterion than the latter (P < 0.001). In both type 2 diabetic (P < 0.001) and nondiabetic subjects (P < 0.001), those who had not attained > or = 50% ST recovery were at significantly higher risk of cardiac death than subjects who had reached this criterion. The subjects who attained the above electrocardiographic criterion in > or = 60 min after thrombolysis initiation were at significantly higher risk compared with those who achieved this criterion in <60 min (P = 0.02). However, this association was true only for type 2 diabetic subjects (P = 0.01) and not for nondiabetic subjects (P = 0.9).

CONCLUSIONS

The present study suggests that type 2 diabetes is a strong predictor of acute intravenous thrombolysis failure during STEMI. This finding may significantly contribute to the worse prognosis for type 2 diabetic subjects compared with nondiabetic ones in this setting.

Glucose-insulin-potassium solution improves left ventricular energetics in chronic ovine diabetes

BACKGROUND

Therapeutic modulation of myocardial metabolism improves outcomes in diabetic patients following myocardial infarction and coronary artery surgery. However, the mechanism of this beneficial effect has not been fully elucidated. This study evaluated the effect of glucose-insulin-potassium solution (GIK) on left ventricular (LV) energetics and oxygen utilization efficiency in a chronic ovine model of diabetes.

METHODS

Diabetes was induced in sheep with streptozotocin. Experiments were performed following 12 months untreated diabetes (n = 6) and in controls (n = 6). Open-chest anesthetized sheep were instrumented to determine the LV pressure-volume relationship, oxygen consumption, and free fatty acid uptake. Glucose-insulin-potassium was infused at 1.5 mL x kg(-1) x h(-1) for 60 minutes and assessment repeated.

RESULTS

Glucose-insulin-potassium decreased LV free fatty acid uptake in control: 0.090 +/- 0.047 microg/beat/100 g to 0.024 +/- 0.022 microg/beat/100 g, p = 0.02 and diabetes: 0.33 +/- 0.32 microg/beat/100 g to 0.11 +/- 0.13 microg/beat/100 g, p = 0.04. Similarly, GIK decreased unloaded left ventricular oxygen consumption (LVVO(2)) in both control (0.42 +/- 0.05 to 0.37 +/- 0.13J/beat/100 g, p < 0.001) and diabetic sheep (0.40 +/- 0.24 to 0.23 +/- 0.23J/beat/100 g, p < 0.001). The slope of the LVVO(2)-pressure-volume area relation (contractile efficiency) was unchanged in either group. Glucose-insulin-potassium improved LV contractility 58% +/- 37% (p = 0.005) and stroke work efficiency 18% +/- 10% (p = 0.009) in diabetic animals but not controls. Therefore, oxygen utilization efficiency (stroke work-LVVO(2)) increased only in diabetic animals (16.6% +/- 4.8% to 26.9% +/- 3.6%, p = 0.002) following GIK.

CONCLUSIONS

This study provides in vivo evidence that GIK improves LV energetics in diabetes. Oxygen utilization efficiency is improved as a result of improved stroke work efficiency and decreased unloaded LVVO(2). Improved efficiency of oxygen utilization provides a physiologic rationale for the beneficial effect of GIK in diabetic patients.

Anti-ischemic effects and long-term survival during ranolazine monotherapy in patients with chronic severe angina

OBJECTIVES

The primary objective of the Monotherapy Assessment of Ranolazine In Stable Angina (MARISA) trial was to determine the dose-response relationship of ranolazine, a potentially new anti-anginal compound, on symptom-limited exercise duration.

BACKGROUND

Fatty acids rise precipitously in response to stress, including acute myocardial ischemia. Ranolazine is believed to partially inhibit fatty acid oxidation, shift metabolism toward carbohydrate oxidation, and increase the efficiency of oxygen use.

METHODS

Patients (n = 191) with angina-limited exercise discontinued anti-anginal medications and were randomized into a double-blind four-period crossover study of sustained-release ranolazine 500, 1,000, or 1,500 mg, or placebo, each administered twice daily for one week. Exercise testing was performed at the end of each treatment during both trough and peak ranolazine plasma concentrations.

RESULTS

Exercise duration at trough increased with ranolazine 500, 1,000, and 1,500 mg twice daily by 94, 103, and 116 s, respectively, all greater (p < 0.005) than the 70-s increase on placebo. Dose-related increases in exercise duration at peak and in times to 1 mm ST-segment depression at trough and peak and to angina at trough and peak were also demonstrated (all p < 0.005). Ranolazine had negligible effects on heart rate and blood pressure. One year survival rate combining data from the MARISA trial and its open-label follow-on study was 96.3 +/- 1.7%.

CONCLUSIONS

In chronic angina patients, ranolazine monotherapy was well tolerated and increased exercise performance throughout its dosing interval at all doses studied without clinically meaningful hemodynamic effects. One-year survival was not lower than expected in this high-risk patient population. This metabolic approach to treating myocardial ischemia may offer a new therapeutic option for chronic angina patients.

Insulin therapy in critically ill patients

PURPOSE OF REVIEW

The recent publication of the results of an aggressive approach to the treatment of hyperglycaemia in critically ill patients, and a rekindling of interest in the use of an infusion of glucose insulin and potassium as adjunctive therapy in a diverse group of patients with cardiovascular disease, warrants a review of the multiple effects of insulin and a review of laboratory and clinical studies.

RECENT FINDINGS

The use of an aggressive protocol to maintain normoglycaemia in critically ill patients has been demonstrated to be a beneficial technique in the critical care setting. Implementation of the protocol outside of a research setting appears to be feasible. Recent studies on the use of insulin in addition to glucose and potassium in patients with diverse cardiovascular diseases have also demonstrated positive results.

SUMMARY

This review will summarize some of the putative beneficial effects of insulin as a pharmacological agent, and review recent clinical data. Although the relative benefits of normoglycaemia in the critical care setting and the beneficial effects of insulin are difficult to differentiate, a substantial overlap exists. The extent to which these converging therapies (aggressive normoglycaemia and insulin pharmacotherapy) will be applicable to diverse clinical settings has yet to be determined.

Effect of Hyperglycemia on Stroke Outcomes

OBJECTIVE

To review published data about the relationship between hyperglycemia and the outcome of patients with stroke.

RESULTS

Stroke is the most frequent cause of permanent disability in the Western world and the third leading cause of death among Americans. Each year, more than 500,000 Americans have a cerebrovascular accident. In the medical literature, numerous reports have discussed how hyperglycemia during acute stroke, regardless of a patient's prior diabetes status, has been associated with significantly higher morbidity, higher mortality, longer hospital stays, reduced long-term recovery, and diminished ability to return to work. In the United States alone, an estimated $300 million in additional health-care costs are incurred among hospitalized patients with stroke who also have high blood glucose levels. Treatment of hyperglycemia has safely, successfully, and effectively yielded glucose levels in the normal range in the hospital setting under the direction of specialty physicians and should be implemented in patients with stroke.

CONCLUSION

Until convincing randomized prospective trials prove that tight glycemic control does not improve stroke outcomes, the overwhelming preponderance of data suggests that aggressive glucose management should be the standard care in all patients with stroke and hyperglycemia.

Molecular Mechanisms by Which Metabolic Control May Improve Outcomes

OBJECTIVE

To summarize available evidence providing potential explanations for metabolic and nonmetabolic abnormalities during conditions of acute stress and possible mechanisms whereby insulin therapy may affect these changes.

RESULTS

Recent studies have demonstrated a remarkable effect of intensive insulin therapy and reductions in morbidity and mortality in patients in intensive-care units and other hospital settings. The mechanisms involved in these effects are under thorough investigation. Insulin therapy improves glucose and lipid homeostasis, both of which are deleterious to the tissues, especially during severe stress. In addition, insulin has direct effects on the levels of inflammatory cytokines and other proteins that may influence the overall outcome of patients undergoing various stressful conditions.

CONCLUSION

Analysis of published studies suggests that the beneficial effects of insulin therapy may be derived from both direct and indirect mechanisms.

The effects of glucose-insulin-potassium solution and BN 52021 in intestinal ischemia-reperfusion injury

The objective of this study was to investigate effects of glucose-insulin-potassium (GIK) solution and BN 52021, a platelet-activating factor antagonist, on intestinal ischemia-reperfusion injury. Fifty male Sprague-Dawley rats (200-225 g) were divided into 5 groups each containing 10 rats; group SO, sham operation group; group I, mesenteric ischemia group (for 30 minutes); group R, ischemia plus reperfusion (for 60 minutes); group BR, ischemia-reperfusion plus BN 52021; group GR, ischemia-reperfusion plus GIK solution. Samples for malondialdehyde (MDA) and ileum (for mucosal injury score) were obtained. The mucosal injury scores of group R were significantly higher than those of group I (4 +/-0.20 and 3 +/-0.16, respectively, p<0.0001). The scores of groups BR and GR were significantly lower than those of group R (p<0.0001 and p<0.0001, respectively). When it was compared with the injuries in BR and GR groups, similar results were obtained in both groups (p=0.190). Mean MDA levels of group R were significantly higher than those of group I, BR and GR (131.33 +/-3.99 nmol/g, 93.74 +/-3.22 nmol/g, 104.81 +/-2.56 and 100.34 +/-5.30, respectively, p<0.0001). MDA levels of group BR and GR were significantly lower than those of group I (p<0.0001 and p=0.003, respectively). These observations suggest that treatment with GIK solution and BN 52021 before reperfusion and during reperfusion period may be useful in decreasing intestinal reperfusion injury.

Implementation of a safe and effective insulin infusion protocol in a medical intensive care unit

OBJECTIVE

In a recent randomized controlled trial, lowering blood glucose levels to 80-110 mg/dl improved clinical outcomes in critically ill patients. In that study, the insulin infusion protocol (IIP) used to normalize blood glucose levels provided valuable guidelines for adjusting insulin therapy. In our hands, however, ongoing expert supervision was required to effectively manage the insulin infusions. This work describes our early experience with a safe, effective, nurse-implemented IIP that provides detailed insulin dosing instructions and requires minimal physician input.

RESEARCH DESIGN AND METHODS

We collected data from 52 medical intensive care unit (MICU) patients who were placed on the IIP. Blood glucose levels were the primary outcome measurement. Relevant clinical variables and insulin requirements were also recorded. MICU nurses were surveyed regarding their experience with the IIP.

RESULTS

To date, our IIP has been employed 69 times in 52 patients admitted to an MICU. Using the IIP, the median time to reach target blood glucose levels (100-139 mg/dl) was 9 h. Once blood glucose levels fell below 140 mg/dl, 52% of 5,808 subsequent hourly blood glucose values fell within our narrow target range; 66% within a "clinically desirable" range of 80-139 mg/dl; and 93% within a "clinically acceptable" range of 80-199 mg/dl. Only 20 (0.3%) blood glucose values were <60 mg/dl, none of which resulted in clinically significant adverse events. In general, the IIP was readily accepted by our MICU nursing staff, most of whom rated the protocol as both clinically effective and easy to use.

CONCLUSIONS

Our nurse-implemented IIP is safe and effective in improving glycemic control in critically ill patients.

Insulin: an endogenous cardioprotector

This review discusses the myocardial protective property of the insulin/glucose-insulin-potassium regimen and the mechanisms involved in this beneficial action. Several recent studies suggest that insulin not only is useful to control hyperglycemia and maintain glucose homeostasis but also may have the unique property to protect the myocardium from reperfusion injury and ischemia and prevent apoptosis of myocardial cells. The insulin/glucose-insulin-potassium (GIK) regimen suppresses the production of tumor necrosis factor-alpha, interleukin-6, macrophage migration inhibitory factor and other pro-inflammatory cytokines, and free radicals; and enhances the synthesis of endothelial nitric oxide and anti-inflammatory cytokines interleukin-4 and interleukin-10. Thus, the insulin/GIK regimen brings about its cardioprotective action. This may also explain why the insulin/GIK regimen is useful in sepsis and septic shock, myocardial recovery in acute myocardial infarction, and critical illness. It is suggested that the infusion of adequate amounts of insulin to patients with acute myocardial infarction, congestive heart failure, cardiogenic shock, and critical illness preserves myocardial integrity and function and ensures rapid recovery. In view of the suppressive action of insulin on the synthesis of proinflammatory cytokines and free radicals, it is possible that the insulin/GIK regimen, when used in a timely and appropriate fashion, may also protect other tissues and organs and facilitate in the recovery of patients who are critically ill.

Mitochondria respiration and susceptibility to ischemia-reperfusion injury in diabetic hearts

Cardiovascular complications are the primary cause of death for diabetic patients. Clinical and experimental observation has showed the development of dysfunctional cardiomyopathy as one of the main complications of diabetes. Whether the cardiomyopathy results from an increased susceptibility of cardiac tissue to ischemic insult or from a specific functional defect of cardiac mitochondria is a controversial issue. The investigation of possible functional defect in cardiac mitochondria from diabetic rats indicates a decline in state 3 respiration only in animals presenting a marked decrease in body weight. Mitochondria from rats presenting a level of hyperglycemia similar to diabetic animals but not the marked weight loss typical of the latter group show no decline in state 3 respiration, the values being indistinguishable from those of control mitochondria. Mitochondria from hyperglycemic rats, however, show a 15-20% increase in state 4 oxygen consumption but only when glutamate is used as energetic substrate, as compared to a 40-50% increase in state 4 respiration in mitochondria from diabetic rats under similar experimental conditions. This phenomenon is unrelated to diabetes duration, as it is observed at 2 as well as 8 weeks after diabetes onset. Taken together, these data argue against hyperglycemia per se being a direct cause of the decline in state 3 oxygen consumption observed in cardiac mitochondria of type-I diabetic rats and indicate that differences exist in cardiac mitochondrial function in rats generically labeled as diabetic. These differences can contribute to explain discrepancies in experimental results reported by various groups in the field and provide an additional parameter to be taken into consideration in evaluating the varying sensitivity of diabetic hearts to ischemia-reperfusion injury.

A shift in myocardial substrate, improved endothelial function, and diminished sympathetic activity may contribute to the anti-anginal impact of very-low-fat diets

A new category of anti-anginal drug - exemplified by ranolazine - is believed to work by partially inhibiting cardiac oxidation of fatty acids; oxidation of glucose requires less oxygen per mol of ATP generated, and thus is preferable to fat oxidation when oxygen availability is limiting in underperfused cardiac tissue. Unfortunately, there is no reason to believe that these drugs inhibit fat oxidation selectively in the heart; thus, chronic use of these drugs can be expected to increase body fat stores until the original rate of fat oxidation is restored by mass action - presumably negating the therapeutic benefit in angina, while exacerbating the manifold adverse effects of insulin resistance syndrome. The rational way to decrease cardiac metabolic reliance on fatty acids is to consume a very-low-fat quasi-vegan diet (i.e., 10% fat calories). Indeed, such diets are known to have a rapid and substantial therapeutic impact on anginal symptoms, while concurrently benefiting insulin sensitivity, markedly improving serum lipid profile, promoting leanness, and lessening coronary risk. A reduction in diurnal insulin secretion might also be achieved, which would be expected to decrease sympathetic activity. While reduced myocardial demand for oxygen doubtless contributes to the beneficial impact of such diets on angina, it is likely that improved cardiac perfusion consequent to improved endothelium-dependent vasodilation also plays a role in this regard. Supplemental carnitine, also beneficial in angina, appears to improve utilization of glucose in the ischemic myocardium by lowering elevated acetyl-coA levels and thereby disinhibiting pyruvate dehydrogenase. Certain other nutraceuticals may aid control of angina by improving endothelial function. In the longer term, these measures have the potential to slow or reverse the progression of stenotic lesions that underlie most cases of angina. These safe and relatively inexpensive nutritional strategies for coping with angina deserve far more attention than orthodox medical practice has thus far accorded them.

Critical issues in endocrinology

Endocrine emergencies are commonly encountered in the ICU. This article focuses on several important endocrine emergencies, including diabetic hyperglycemic states, adrenal insufficiency, myxedema coma, thyroid storm, and pituitary apoplexy. Other endocrine issues that are related to intensive care, such as intensive insulin therapy, relative adrenal insufficiency, and thyroid function test abnormalities are also covered in detail.

Short- and long-term beneficial effects of trimetazidine in patients with diabetes and ischemic cardiomyopathy

BACKGROUND

Trimetazidine (TMZ) has been shown to partially inhibit free fatty acid oxidation by shifting substrate utilization from fatty acid to glucose. The aim of this study was to assess the effects of TMZ in patients with diabetes and ischemic cardiomyopathy.

METHODS

Sixteen patients with diabetes and ischemic hypokinetic cardiomyopathy (all males) on conventional therapy were randomized to receive either placebo or TMZ (20 mg 3 times per day), each arm lasting 15 days, and then again to receive either placebo or TMZ for 2 additional 6-month periods, according to a double-blind, crossover design. At the end of each period, all patients underwent exercise testing, 2-dimensional echocardiography, and hyperinsulinemic/euglycemic clamp. Among the others, New York Heart Association class, ejection fraction, exercise time, fasting blood glucose, end-clamp M value (index of total body glucose disposal) and endothelin-1 levels were evaluated.

RESULTS

Both in the short and long term (completed by 13 patients), on TMZ compared to placebo, ejection fraction (47 +/- 7 vs 41 +/- 9 and 45 +/- 8 vs 36 +/- 8%, P <.001 for both) and M value (4.0 +/- 1.8 vs 3.3 +/- 1.6, P =.003, and 3.5 +/- 1.5 vs 2.7 +/- 1.6 mg/kg body weight/min, P <.01) increased, while fasting blood glucose (121 +/- 30 vs 136 +/- 40, P =.02 and 125 +/- 36 vs 140 +/- 43, P =.19) and endothelin-1 (8.8 +/- 3.8 vs 10.9 +/- 3.8, P <.001 and 6.2 +/- 2.4 vs 9.2 +/- 4.3 pg/mL, P =.03) decreased. In the short term, 10 patients decreased 1 class on the NYHA scale during treatment with TMZ (P =.019 vs placebo). Eight patients decreased 1 NYHA class while on long-term TMZ treatment, while on placebo 1 patient increased 1 NYHA class and none improved (P =.018 vs placebo).

CONCLUSIONS

In a short series of patients with diabetes and ischemic cardiomyopathy, TMZ improved left ventricular function, symptoms, glucose metabolism, and endothelial function. Shifting energy substrate preference away from fatty acid metabolism and toward glucose metabolism by TMZ appears an effective adjunctive treatment in patients with diabetes with postischemic cardiomyopathy.

Impact of acute hyperglycemia on left ventricular function after reperfusion therapy in patients with a first anterior wall acute myocardial infarction

OBJECTIVE

This study was undertaken to assess the relationship between acute hyperglycemia and left ventricular function after reperfusion therapy for acute myocardial infarction (AMI).

METHODS

This study consisted of 529 patients with a first anterior wall AMI who underwent coronary angiography followed by coronary angioplasty or thrombolysis within 12 hours after the onset of chest pain. Plasma glucose was measured at the time of hospital admission. Acute hyperglycemia was defined as plasma glucose >10 mmol/L.

RESULTS

Although acute hyperglycemia was associated with both lower acute left ventricular ejection fraction (LVEF) (46% +/- 12% vs 48% +/- 10%, P =.026) and lower predischarge LVEF (51% +/- 15% vs 56% +/- 15%, P =.001), the difference was more pronounced in the latter and the change in LVEF was significantly smaller in patients with acute hyperglycemia (4.8% +/- 11.2% vs 8.0% +/- 13.8%, P =.022). Multivariable analysis showed that there was a significant correlation between plasma glucose and impaired predischarge LVEF, even after adjustment of acute LVEF (r = -0.13, P =.005). Thirty-day mortality tended to be higher in patients with acute hyperglycemia than in patients without (7.1% vs 3.5%, P =.06). Multivariable analysis showed that plasma glucose (per 1 mmol/L increase) was an independent predictor of 30-day mortality after AMI (odds ratio 1.12, 95% CI 1.03-1.22, P =.009).

CONCLUSION

Acute hyperglycemia was independently associated with impaired left ventricular function and higher 30-day mortality after AMI. These results may provide a potential explanation for poor outcomes of patients with AMI and acute hyperglycemia.

Glucose-insulin-potassium infusion inpatients treated with primary angioplasty for acute myocardial infarction: the glucose-insulin-potassium study: a randomized trial

OBJECTIVES

In this study we considered the question of whether adjunction of glucose-insulin-potassium (GIK) infusion to primary coronary transluminal angioplasty (PTCA) is effective in patients with an acute myocardial infarction (MI).

BACKGROUND

A combined treatment of early and sustained reperfusion of the infarct-related coronary artery and the metabolic modulation with GIK infusion has been proposed to protect the ischemic myocardium.

METHODS

From April 1998 to September 2001, 940 patients with an acute MI and eligible for PTCA were randomly assigned, by open-label, to either a continuous GIK infusion for 8 to 12 h or no infusion.

RESULTS

The 30-day mortality was 23 of 476 patients (4.8%) receiving GIK compared with 27 of 464 patients (5.8%) in the control group (relative risk [RR] 0.82, 95% confidence interval [CI] 0.46 to 1.46). In 856 patients (91.1%) without signs of heart failure (HF) (Killip class 1), 30-day mortality was 5 of 426 patients (1.2%) in the GIK group versus 18 of 430 patients (4.2%) in the control group (RR 0.28, 95% CI 0.1 to 0.75). In 84 patients (8.9%) with signs of HF (Killip class > or =2), 30-day mortality was 18 of 50 patients (36%) in the GIK group versus 9 of 34 patients (26.5%) in the control group (RR 1.44, 95% CI 0.65 to 3.22).

CONCLUSIONS

Glucose-insulin-potassium infusion as adjunctive therapy to PTCA in acute MI did not result in a significant mortality reduction in all patients. In the subgroup of 856 patients without signs of HF, a significant reduction was seen. The effect of GIK infusion in patients with signs of HF (Killip class > or =2) at admission is uncertain.

Glycometabolic status and acute myocardial infarction: has the time come for glucose-insulin-(potassium) therapy?

Glucose-insulin-potassium infusion as a metabolic therapy was first advocated for the management of acute myocardial infarction (AMI) in 1960s. Over the subsequent decades, enthusiasm for its use has been patchy, especially with the availability of other effective treatments such as reperfusion therapy for AMI. Several clinical studies in the mid-1990s revived the interest in the glycometabolic aspects of patients with AMI. The somewhat conflicting results of these recent studies have generated debate over the significance of the glycometabolic state following acute coronary occlusion and the role of insulin-based infusion therapy. Although most of the available evidence is in favour of an insulin-based therapy, there are still many aspects of this therapy that require clarification. More evidence will be required from further clinical trials before it is adopted in routine clinical practice.

Beneficial effects of trimetazidine in ex vivo working ischemic hearts are due to a stimulation of glucose oxidation secondary to inhibition of long-chain 3-ketoacyl coenzyme a thiolase

High rates of fatty acid oxidation in the heart and subsequent inhibition of glucose oxidation contributes to the severity of myocardial ischemia. These adverse effects of fatty acids can be overcome by stimulating glucose oxidation, either directly or secondary to an inhibition of fatty acid oxidation. We recently demonstrated that trimetazidine stimulates glucose oxidation in the heart secondary to inhibition of fatty acid oxidation. This inhibition of fatty acid oxidation was attributed to an inhibition of mitochondrial long-chain 3-ketoacyl CoA thiolase (LC 3-KAT), an enzyme of fatty acid beta-oxidation. However, the accompanying Research Commentary of MacInnes et al suggests that trimetazidine does not inhibit cardiac LC 3-KAT. This discrepancy with our data can be attributed to the reversible competitive nature of trimetazidine inhibition of LC 3-KAT. In the presence of 2.5 micromol/L 3-keto-hexadecanoyl CoA (KHCoA), trimetazidine resulted in a 50% inhibition of LC-3-KAT activity. However, the inhibition of LC 3-KAT could be completely reversed by increasing substrate (3-keto-hexadecanoyl CoA, KHCoA) concentrations to 15 micromol/L even at high concentrations of trimetazidine (100 micromol/L). The study of MacInnes et al was performed using concentrations of 3K-HCoA in excess of 16 micromol/L, a concentration that would completely overcome 100 micromol/L trimetazidine inhibition of LC 3-KAT. Therefore, the lack of inhibition of LC 3-KAT by trimetazidine in the MacInnes et al study can easily be explained by the high concentration of KHCoA substrate used in their experiments. In isolated working hearts perfused with high levels of fatty acids, we found that trimetazidine (100 micromol/L) significantly improves functional recovery of hearts subjected to a 30-minute period of global no-flow ischemia. This occurred in the absence of changes in oxygen consumption resulting in an improved increase in cardiac efficiency. Combined with our previous studies, we conclude that trimetazidine inhibition of LC 3-KAT decreases fatty acid oxidation and stimulates glucose oxidation, resulting in an improvement in cardiac function and efficiency after ischemia. The full text of this article is available online at http://www.circresaha.org.

Heart failure: the frequent, forgotten, and often fatal complication of diabetes

There is a high frequency of heart failure (HF) accompanied by an increased mortality risk for patients with diabetes. The poor prognosis of these patients has been explained by an underlying diabetic cardiomyopathy exacerbated by hypertension and ischemic heart disease. In these patients, activation of the sympathetic nervous system results in increased myocardial utilization of fatty acids and induction of fetal gene programs, decreasing myocardial function. Activation of the renin-angiotensin system results in myocardial remodeling. It is imperative for physicians to intercede early to stop the progression of HF, yet at least half of patients with left ventricular dysfunction remain undiagnosed and untreated until advanced disease causes disability. This delay is largely because of the asymptomatic nature of early HF, which necessitates more aggressive assessment of HF risk factors and early clinical signs. Utilization of beta-blockade, ACE inhibitors, or possibly angiotensin receptor blockers is essential in preventing remodeling with its associated decline in ventricular function. beta-Blockers not only prevent, but may also reverse, cardiac remodeling. Glycemic control may also play an important role in the therapy of diabetic HF. The adverse metabolic side effects that have been associated with beta-adrenergic inhibitors in the diabetic patient may be circumvented by use of a third-generation beta-blocker. Prophylactic utilization of ACE inhibitors and beta-blockers to avoid, rather than await, the need to treat HF should be considered in high-risk diabetic patients.

Effects of glucose-insulin-potassium solution on myocardial salvage and left ventricular function after primary angioplasty

OBJECTIVE

To evaluate the effects of glucose-insulin-potassium (GIK) therapy on infarct size and left ventricular function when used as an adjuvant therapy to primary angioplasty.

DESIGN

Prospective, randomized, double-blind, placebo-controlled study.

SETTING

Cardiac intensive care unit at a university hospital.

PATIENTS

Thirty-seven patients with acute myocardial infarction for whom primary angioplasty was indicated.

INTERVENTIONS

Eligible patients were randomized by a blinded pharmacist to GIK solution (30% glucose in water with insulin 50 U/L, and KCl 40 mM/L) vs. placebo at 1.5 mL/kg/hr for 24 hrs.

MEASUREMENTS AND MAIN RESULTS

Tc 99m sestamibi myocardial scintigraphy was performed at admission and at 3 months. Primary end points were the changes in left ventricular ejection fraction (LVEF) and the size of salvaged myocardium. Baseline clinical characteristics were similar in both groups. At the 3-month follow-up, a significant overall decrease in infarct size (37 +/- 16% vs. 12 +/- 10%, p <.005) and an increase in LVEF (34 +/- 13% vs. 49 +/- 9%, p =.005) were observed. Patients randomized to GIK solution experienced a significant increase in their LVEF at 3 months (39 +/- 12 to 51 +/- 13, p =.002). Patients who received placebo had no significant differences between baseline and 3-month measurements (44 +/- 13 vs. 49 +/- 14, p = NS). There was a trend toward an increase in myocardial salvage in the GIK group, which did not reach statistical significance. When patients from both groups were compared directly, differences in LVEF improvement were no longer significant.

CONCLUSIONS

GIK solution did not improve LVEF or decrease the infarct size among patients undergoing primary angioplasty.

Effects of glucose-insulin-potassium on baroreflex sensitivity, left ventricular function and ventricular arrhythmia in the subacute phase of myocardial infarction in rats

Glucose-insulin-potassium (GIK) is clinically used for reducing mortality in acute myocardial infarction (MI). It is known that ventricular arrhythmia, left ventricular dysfunction and impaired baroreflex sensitivity (BRS) are the three major determinants for predicting the mortality after acute MI. The present work was designed to study the effects of GIK on BRS, ventricular arrhythmia, and left ventricular function in rats with coronary artery ligature. Sprague-Dawley rats were used and the myocardial infarction was produced by ligature of the left anterior descending artery. Five weeks after coronary artery ligation, BRS was measured in conscious state with a computerized blood pressure monitoring system and left ventricular function and electrocardiogram were determined in the anaesthetized state in the subacute phase of myocardial infarction. It was found that GIK did not affect the blood pressure and heart period in both conscious and anaesthetized rats. GIK did not enhance BRS, but reduced ventricular arrhythmia and improved left ventricular function by reducing left ventricular end diastolic pressure in anaesthetized rats with MI. It is proposed that reducing ventricular arrhythmia and improving left ventricular function contribute to the effect of GIK on reducing the mortality after MI.