Effects of glucose and glucose-insulin-potassium on haemodynamics and enzyme release after acute myocardial infarction

Insulin Therapy and In-Hospital Mortality in Critically Ill Patients: Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

Hyperglycemia is common in critically ill hospitalized patients and has been associated with adverse outcomes, including increased mortality. In this review, we examine the effect of insulin therapy on mortality in critically ill patients.

METHODS

We updated our previous systematic review and meta-analysis to include recently published trials that report data on the effect of insulin therapy initiated during hospitalization on mortality in adult patients with a critical illness. We also include a short primer on the methods of systematic reviews and meta-analyses, outlining the specific steps and challenges of this methodology. We performed an electronic search in the English language of MEDLINE and the Cochrane Controlled Clinical Trials Register and a hand search of key journals and relevant review articles for randomized controlled trials that reported mortality data on critically ill hospitalized adult patients treated with insulin (regardless of method of administration).

RESULTS

We identified 38 relevant studies that entered the analysis. We found that therapy with insulin in adult patients hospitalized for a critical illness, other than hyperglycemic crises, may decrease mortality in certain groups of patients. The beneficial effect of insulin was evident in the surgical intensive care unit (relative risk [RR], 0.58; confidence interval [CI], 0.22-0.62) and in patients with diabetes (RR, 0.76; CI, 0.62-0.92). There was a trend toward benefit in patients with acute myocardial infarction (RR, 0.89; CI, 0.76-1.03). Targeting euglycemia appears to be the main determinant of the benefit of insulin therapy (RR, 0.73; CI, 0.57-0.94).

CONCLUSIONS

Insulin therapy in adult patients hospitalized for a critical illness, other than hyperglycemic crises, may decrease mortality in certain groups of patients.

The effect of insulin on the heart: Part 2: Effects on function during and post myocardial ischaemia

Insulin infusion has been advocated in the treatment of myocardial ischaemia and myocardial infarction. There is evidence from experimental animal studies for a protective effect of high-dose insulin administration in myocardial ischaemia and myocardial infarction. In some relatively small study populations a reduction in mortality was reported in those patients who received glucose-insulin-potassium (GIK) during myocardial infarction, which was confirmed in two meta-analyses. However, it has not been possible to reproduce these positive results in large randomised clinical trials. (Neth Heart J 2010;18:255-9.).

A meta-analysis of glucose-insulin-potassium therapy for treatment of acute myocardial infarction

BACKGROUND

Glucose-insulin-potassium (GIK) therapy has been proposed to provide metabolic support to ischemic myocardium. A meta-analysis that included 1932 patients performed 10 years previously demonstrated that GIK therapy may have an important role in reducing mortality after acute myocardial infarction (AMI). Since then, many larger randomized trials investigating the role of GIK in the setting of AMI have been published; hence, the present study repeats the previous meta-analysis performed by the current authors to include these trials.

METHOD AND RESULTS

A systematic MEDLINE search for all randomized, placebo-controlled studies of GIK therapy in the setting of AMI was conducted and a meta-analysis of the mortality data was performed. A total of 16 randomized trials from 1966 to 2008 were identified, with 28,374 patients included in the current meta-analysis. There was a total of 1367 deaths (9.6%) in the GIK group, with 1351 deaths (9.6%) in the control group. Meta-analysis did not reveal any benefit from GIK treatment (OR 1.0; 95% CI 0.9 to 1.1; P=0.9). Subgroup analysis of patients given high-dose GIK and in patients in whom reperfusion was not obtained did not demonstrate a benefit from GIK therapy.

CONCLUSION

A meta-analysis of 16 randomized trials that spanned 40 years and involved more than 28,000 patients did not reveal any mortality benefit for ST segment elevation AMI using GIK therapy when data from the modern thrombolysis/primary percutaneous coronary intervention era were included.

Glucose-insulin-potassium-albumin infusion in the early phase of acute myocardial infarction--a controlled study

Fifty consecutive patients with acute myocardial infarction admitted to a coronary care unit within 6 hours from onset of symptoms were randomly assigned either to a treatment group (n=27) receiving glucose-insulin-potassium-albumin (GIKA) or to a control group (n=23), comparable regarding clinical data, receiving 5.5% glucose. Both infusions were given intravenously at a rate of 1.2 ml/kg b.wt./hour during 48 hours. The GIKA solution contained 40 mEq K+, 10 ml 20% albumin and 16 IU regular crystalline insulin per 1000 ml 10% glucose. Before the infusion, the treatment group received an i.v. loading dose of 50 ml 50% glucose. Serum time activity curves for creatine kinase (CK) and myoglobin (MG) were established from frequent blood level determinations. A 15-minute single-lead ECG was recorded every fourth hour and subsequently analysed for ventricular arrhythmias. The two patient groups did not differ regarding cumulative MG and CK release. The GIKA group had significantly more patients with high MG/CK ratios (p less than 0.02). No clinically significant difference was found between the two patient groups regarding ventricular arrhythmias, even if ventricular extrasystoles tended to occur less frequently in the GIKA group.

Glucose and potassium derangements by glucose-insulin-potassium infusion in acute myocardial infarction

BACKGROUND

High-dose glucose-insulin-potassium infusion (GIK) has been suggested to be beneficial in acute myocardial infarction (MI). Recently new large trials have shown no effect of GIK on mortality. To investigate whether metabolic derangement could have negated the potential beneficial effect, we studied the relation between systemic glucose and potassium levels and outcome.

METHODS

Patients with signs and symptoms of ST-segment-elevation MI and treated with primary percutaneous coronary intervention (PCI) were randomised to no infusion or high-dose GIK, i.e. 80 mmol potassium chloride in 500 ml 20% glucose at a rate of 3 ml/kg/hour and 50 units short-acting insulin in 50 ml 0.9% sodium chloride for 12 hours.

RESULTS

A total of 6991 glucose values and 7198 potassium values were obtained in 476 GIK patients and 464 controls. Mean serum glucose was significantly higher in the GIK group (9.3±4.5 mmol/l vs. 8.4±2.9 mmol/l, p<0.001). Mean potassium level was significantly higher in the GIK group (4.2±0.5 mmol/l vs. 3.9±0.4 mmol/l, p<0.001). Incidence of hyperglycaemia (glucose >11.0 mmol/l) occurred in 70.8% of GIK patients and 33.8% of controls (p<0.001). Hypokalaemia was less common in the GIK group (23.5 vs. 41.2%, p<0.001). Incidence of hyperkalaemia and hypoglycaemia did not differ significantly between the two groups. In multivariate analysis age, previous cardiovascular disease, Killip class >1, unsuccessful PCI and mean glucose after admission were associated with increased one-year mortality.

CONCLUSION

In ST-segment-elevation MI patients treated with primary PCI, high-dose GIK induced hyperglycaemia and prevented hypokalaemia. Derangement of the glucose metabolism was related to one-year mortality.

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.

A quantitative analysis of the effect of glucose-insulin-potassium in acute myocardial infarction

OBJECTIVE

To review the currently available data to investigate the clinical benefit of high- and low-dose glucose-insulin-potassium (GIK) in patients with ST-segment elevation acute myocardial infarction (STEMI).

DESIGN

Quantitative analysis of all randomised trials on GIK in patients with STEMI. Electronic and manual searches for randomised controlled trials of GIK in STEMI were performed with regard to inclusion criteria, dose of GIK and additional use of reperfusion therapy, and a meta-analysis with the primary endpoint 30-day mortality was performed.

PATIENTS

Data from 16 randomised trials, involving 26,273 patients, were included.

RESULTS

Studies were conducted between 1962 and 2005. Overall, hospital mortality was 9.6% after GIK compared with 10.2% in controls (p=0.088). GIK infusion was not associated with an increase in major adverse events.

CONCLUSION

This quantitative analysis of GIK in patients with STEMI did not show a beneficial or detrimental effect of GIK infusion on 30-day mortality. GIK infusion should not be part of the standard therapy for patients with STEMI.

The impact of glucose-insulin-potassium infusion in acute myocardial infarction on infarct size and left ventricular ejection fraction [ISRCTN56720616]

BACKGROUND

Favorable clinical outcomes have been observed with glucose-insulin-potassium infusion (GIK) in acute myocardial infarction (MI). The mechanisms of this beneficial effect have not been delineated clearly. GIK has metabolic, anti-inflammatory and profibrinolytic effects and it may preserve the ischemic myocardium. We sought to assess the effect of GIK infusion on infarct size and left ventricular function, as part of a randomized controlled trial.

METHODS

Patients (n = 940) treated for acute MI by primary percutaneous coronary intervention (PCI) were randomized to GIK infusion or no infusion. Endpoints were the creatinine kinase MB-fraction (CK-MB) and left ventricular ejection fraction (LVEF). CK-MB levels were determined 0, 2, 4, 6, 24, 48, 72 and 96 hours after admission and the LVEF was measured before discharge.

RESULTS

There were no differences between the two groups in the time course or magnitude of CK-MB release: the peak CK-MB level was 249 +/- 228 U/L in the GIK group and 240 +/- 200 U/L in the control group (NS). The mean LVEF was 43.7 +/- 11.0 % in the GIK group and 42.4 +/- 11.7% in the control group (P = 0.12). A LVEF < or = 30% was observed in 18% in the controls and in 12% of the GIK group (P = 0.01).

CONCLUSION

Treatment with GIK has no effect on myocardial function as determined by LVEF and by the pattern or magnitude of enzyme release. However, left ventricular function was preserved in GIK treated patients.

ST-segment elevation resolution and outcome in patients treated with primary angioplasty and glucose-insulin-potassium infusion

BACKGROUND

To evaluate the impact of adjunctive high-dose glucose-insulin-potassium (GIK) on ST-segment elevation resolution in patients with ST-segment elevation myocardial infarction (MI).

METHODS

As part of a randomized controlled trial of GIK versus no GIK in patients treated with primary percutaneous coronary intervention (PCI) for ST-elevation MI in a tertiary referral center, we analyzed ST-segment elevation resolution. Paired electrocardiographic recordings (baseline and 3 hours after primary PCI) were available in 612 (65%) of 940 patients.

RESULTS

We analyzed paired electrocardiograms of 310 patients randomized to GIK and 302 control patients. Baseline characteristics of the groups were comparable. Combined complete (>70%) and partial (30%-70%) resolution was more commonly observed in the GIK group (87%) when compared with the control group (78%), odds ratio 1.92 (95% CI 1.23-3.02, P = .004); 1-year mortality was lower in patients with combined complete and partial resolution compared with patients without resolution (3.8% vs 10.3%, P = .011). There was no difference in 1-year mortality between GIK and control patients (5.5% vs 4.3%, P = .58).

CONCLUSIONS

In patients with ST-elevation MI treated with primary PCI, addition of GIK is associated with improved ST-segment elevation resolution. ST-segment elevation resolution is related to improved 1-year survival. No benefit of GIK on 1-year outcome was observed. Future trials should investigate whether GIK-induced improvement of ST-segment elevation resolution results in more favorable clinical outcome.

Potential beneficial mechanisms of insulin (glucose-potassium) in acute myocardial infarction

In the time-span of almost a century, a large amount of experimental evidence has been accumulated that underlines the importance of glucose metabolism during ischaemia/reperfusion of the heart. As early as 1912, Goulston suggested that treatment with glucose could be beneficial in several heart diseases. The first experimental results on the mechanical effects of insulin and glucose in the isolated heart were reported by Visscher and Muller in 1926. In 1935, Evans and colleagues showed that the uptake of glucose is increased in the ischaemic myocardium. Almost 30 years later, Sodi-Pallares and colleagues suggested that metabolic interference during myocardial ischaemia with GIK infusion decreased electrocardiographic signs of ischaemia. They also showed that glucose-insulin-potassium (GIK) infusion resulted in a lower occurrence of arrhythmias. They attributed this effect mainly to the influx of potassium in ischaemic cardiomyocytes. In order to further stimulate potassium transport into the cell, insulin was administered. Consequently, the rise of intercellular calcium is curtailed by the influx of potassium and so the incidence of arrhythmias is reduced. However, systemic infusion of insulin stimulates the uptake of glucose in many celltypes, which may result in hypoglycaemic episodes. Consequently, it is not possible to administer potassium and insulin in high concentrations without adding glucose. Interventions in the glucose metabolism in the clinical arena, whether or not used to correct acute hyperglycaemia, encompass three potentially effective elements: glucose, insulin and potassium.

Challenges in the conduct of large simple trials of important generic questions in resource-poor settings: the CREATE and ECLA trial program evaluating GIK (glucose, insulin and potassium) and low-molecular-weight heparin in acute myocardial infarction

Background

Approximately 15.5 million deaths from cardiovascular diseases occur every year. About half are due to acute myocardial infarction (AMI), and 80% occur in low- and middle-income countries. Therefore, low-cost therapies would be invaluable. Although glucose-insulin-potassium (GIK) infusion and low-molecular-weight heparin (LMWH) appear to be promising in AMI, the available trials are inconclusive and these treatments require rigorous evaluation.

Methods

The Clinical Trial of Reviparin and Metabolic Modulation in Acute Myocardial Infarction Treatment and Evaluation-Estudios Clínicos Latino America (CREATE-ECLA) study is a randomized controlled trial in ST-elevation AMI patients evaluating a 24-hour infusion of Glucose-Insulin-Potassium (GIK) intravenous vs usual care (control) on 30-day mortality in 20 000 patients from 21 countries. Patients from India and China (n = 15 000) are also randomized using a factorial design to receive low-molecular-weight heparin (Reviparin) or placebo injection twice daily for 7 days to assess the impact on the composite outcomes of death, reinfarction or stroke (first co-primary outcome) or the composite + refractory ischemia (second co-primary outcome).

Results

Twenty thousand two hundred and one (20,201) GIK/control patients and 15,570 Reviparin/placebo patients have been included, with results expected in November 2004.

Conclusions

The CREATE-ECLA trial will provide definitive answers to the role of 2 practical, promising and low-cost therapies, LMWH and GIK, in AMI patients. If effective, these therapies could be used in small medical centers in low- and middle- income countries. The experiences in this trial indicate that large trials of important questions can be successfully conducted in resource-poor settings, by academic groups without industry involvement.

Cardioprotection by glucose-insulin-potassium: dependence on KATP channel opening and blood glucose concentration before ischemia

We tested the hypothesis that glucose-insulin-potassium (GIK)-induced protection against myocardial infarction depends on ATP-dependent K(+) (K(ATP)) channel activation and is abolished by hyperglycemia before the ischemia. Dogs were subjected to a 60-min coronary artery occlusion and 3-h reperfusion in the absence or presence of GIK (25% dextrose; 50 IU insulin/l; 80 mM/l KCl infused at 1.5 ml x kg(-1) x h(-1)) beginning 75 min before coronary artery occlusion or 5 min before reperfusion. The role of K(ATP) channels was evaluated by pretreatment with glyburide (0.1 mg/kg). The efficacy of GIK was investigated with increases in blood glucose (BG) concentrations to 300 or 600 mg/dl or experimental diabetes (alloxan/streptozotocin). Infarct size (IS) was 29 +/- 2% of the area at risk in control experiments. GIK decreased (P < 0.05) IS when administered beginning 5 min before reperfusion. This protective action was independent of BG (13 +/- 2 and 12 +/- 2% of area at risk; BG = 80 or 600 mg/dl, respectively) but was abolished in dogs receiving glyburide (30 +/- 4%), hyperglycemia before ischemia (27 +/- 4%), or diabetes (25 +/- 3%). IS was unchanged by GIK when administered before ischemia independent of BG (31 +/- 3, 27 +/- 2, and 35 +/- 3%; BG = 80, 300, and 600 mg/dl, respectively). The insulin component of GIK promotes cardioprotection by K(ATP) channel activation. However, glucose decreases K(ATP) channel activity, and this effect predominates when hyperglycemia is present before ischemia.

Optimal care of patients with type 2 diabetes mellitus and coronary artery disease

Although cardiovascular mortality rates for the general population have declined during the past several decades, mortality among individuals with diabetes mellitus has increased. Given that the prevalence of type 2 diabetes is increasing dramatically and that current treatment strategies appear inadequate, there is a critical need for well-designed studies to address treatment of coronary artery disease in patients with diabetes to help guide clinical decision making in this setting. The Bypass Angioplasty Revascularization Investigation (BARI)-2D focuses on 2 specific treatment issues in the management of patients with type 2 diabetes. The first issue is the incremental value of early use of coronary revascularization procedures, and the second is the value of treating with an insulin-sensitizing agent versus an insulin-providing therapy. It is essential to determine whether treatment to enhance insulin sensitivity improves cardiovascular survival. Data indicate that outcomes of patients with diabetes and myocardial infarction are improved by administration of insulin or a regimen of glucose, insulin, and potassium (GIK). The Diabetes Mellitus Insulin-Glucose Infusion in Acute Myocardial Infarction (DIGAMI) study showed that administration of an insulin infusion followed by subcutaneous insulin therapy for > or =3 months improved the long-term prognosis of diabetic patients with acute myocardial infarction. However, there appears to be a lack of acceptance of these interventions by health care providers. Clinical trials of GIK and insulin sensitizers are needed to define further the optimal treatment of patients with type 2 diabetes and cardiovascular disease.

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.

Diabetes and hyperglycemia impair activation of mitochondrial K(ATP) channels

Hyperglycemia is an important predictor of cardiovascular mortality in patients with diabetes. We investigated the hypothesis that diabetes or acute hyperglycemia attenuates the reduction of myocardial infarct size produced by activation of mitochondrial ATP-regulated potassium (K(ATP)) channels. Acutely instrumented barbiturate-anesthetized dogs were subjected to a 60-min period of coronary artery occlusion and 3 h of reperfusion. Myocardial infarct size (triphenyltetrazolium chloride staining) was 25 +/- 1, 28 +/- 3, and 25 +/- 1% of the area at risk (AAR) for infarction in control, diabetic (3 wk after streptozotocin-alloxan), and hyperglycemic (15% intravenous dextrose) dogs, respectively. Diazoxide (2.5 mg/kg iv) significantly decreased infarct size (10 +/- 1% of AAR, P < 0.05) but did not produce protection in the presence of diabetes (28 +/- 5%) or moderate hyperglycemia (blood glucose 310 +/- 10 mg/dl; 23 +/- 2%). The dose of diazoxide and the degree of hyperglycemia were interactive. Profound (blood glucose 574 +/- 23 mg/dl) but not moderate hyperglycemia blocked the effects of high-dose (5.0 mg/kg) diazoxide [26 +/- 3, 15 +/- 3 (P < 0.05), and 11 +/- 2% (P < 0.05), respectively]. There were no differences in systemic hemodynamics, AAR, or coronary collateral blood flow (by radioactive microspheres) between groups. The results indicate that diabetes or hyperglycemia impairs activation of mitochondrial K(ATP) channels.

[Therapy with glucose-insulin-potassium reduces the complications in the acute phase of myocardial infarct. Arguments in favor]

Several therapeutic approaches have been proposed for the management of acute myocardial infarction (AMI). In 1961, Sodi-Pallarés presented the Glucose-Insulin-Potassium (GIK) infusion as a valid adjunctive therapy for the treatment of the acute phase. He observed a decrease in mortality which could be explained by some mechanisms such as: arrhythmia prevention, hypoxic cell nutrition, diminution of infarct size and others. Due to the lack of Coronary Care Units at that time, acute myocardial ischemia was considered a high mortality disease. Therefore, the first studies concerning the efficacy of this treatment showed a significant decrease in mortality. After the development of better care and medical attention of AMI patients, and above all after the introduction of fibrinolysis, mortality dramatically diminished. Thus, GIK was considered to give no additional benefit, and its use became restricted to a small number of centers. In this review the physiopathological bases of GIK solution use are given, as well as the results of the main experimental studies and a critical analysis of the scarce clinical studies available. It is concluded that there are enough data to support the use of GIK solution in non-thrombolized AMIs. It could probably also benefit thrombolised ones, although there is no available evidence in this context.

Glucose-insulin-potassium therapy for treatment of acute myocardial infarction: an overview of randomized placebo-controlled trials

BACKGROUND

Glucose-insulin-potassium (GIK) therapy has been advocated for the treatment of acute myocardial infarction. However, the results from the clinical trials have been inconclusive, largely because of the small number of patients recruited and discrepancies between protocols used in these studies.

METHOD AND RESULTS

A systematic MEDLINE search for all the randomized placebo-controlled studies of GIK therapy in acute myocardial infarction was made, and a meta-analysis of the mortality data was performed. Fifteen trials were identified, 5 were excluded because of poor randomization, and 1 was excluded because recruitment was limited to diabetic patients. The 9 remaining trials with a total of 1932 patients were included in the analysis. Hospital mortality was reduced from 21% (205 of 972 patients) in the placebo group to 16.1% (154 of 956) in the GIK group (P=.004; odds ratio, 0.72; 95% confidence interval [CI], 0.57 to 0.90). The proportional mortality reduction was 28% (CI, 10% to 43%). The number of lives saved per 1000 patients treated was 49 (95% CI, 14 to 83).

CONCLUSIONS

The findings indicate that GIK therapy may have an important role in reducing the in-hospital mortality after acute myocardial infarction. The value of this therapy in the era of thrombolysis and acute revascularization by primary angioplasty can be fully resolved only by conducting a large randomized mortality study.

An algorithm for tight glycaemic control in diabetic infarct survivors

An algorithm has been developed to provide predictable control of blood glucose for 48 h following acute myocardial infarction. In 29 diabetic patients intravenous infusion of soluble insulin was started upon admission to hospital and the rate adjusted hourly on the basis of bedside capillary glucose estimations. Insulin infusion rates related to glycaemia were higher in obese patients and those with severe cardiac failure. For all patients mean admission glucose levels were reduced from 18.3 +/- 5.9 mmol l-1 to 9.1 +/- 3.3 mmol l-1 at 4 h and to 8.8 +/- 2.5 mmol l-1 at 6 h. Mean glucose concentrations for 48 h after admission were 8.2 +/- 1.3 mmol l-1 for all patients. Admission glucose levels were slightly higher in patients with severe, compared to those without or mild, cardiac failure (P less than 0.1), but levels over the following 48 h were similar. Doubling insulin infusion rates before meals did not achieve tighter glycaemic control. Hypoglycaemia (glucose less than 3 mmol l-1) occurred on 11 occasions in six patients; only two episodes were symptomatic and only two episodes occurred when the insulin rates were doubled before meals. This algorithm produced tighter glycaemic control than previously published protocols, particularly in patients with severe cardiac failure. Hypoglycaemia is uncommon and the algorithm easy to administer by nursing staff.

Hemodynamic and electrocardiographic effects of fructose-1,6-diphosphate in acute myocardial infarction

Acute hemodynamic and electrocardiographic effects of fructose-1,6-diphosphate (FDP), an agent that is supposed to restore anaerobic glycolytic flux in the ischemic myocardium, were studied in 40 patients with acute myocardial infarction who were grouped into 4 subsets: subset 1, normal (15 mm Hg or less) pulmonary artery (PA) wedge pressure and normal (35 g-m/m2 or greater) left ventricular (LV) stroke work index; subset 2, elevated (more than 15 mm Hg) PA wedge pressure and normal LV stroke work index; subset 3, normal PA wedge pressure and reduced (less than 35 g-m/m2) LV stroke work index; subset 4, elevated PA wedge pressure and LV stroke work index moderately reduced to a range between 16 and 34 g-m/m2. Patients were randomized into an FDP (250 mg/kg body weight in isotonic saline solution intravenously in 20 minutes) and into a placebo group. Each subset contained 5 FDP- and 5 placebo-treated patients. After basal measurements, hemodynamic measurements were reassessed at 60, 90 and 120 minutes from the infusions, while a standard 12-lead electrocardiogram was recorded in the basal state and 120 minutes after infusion. Nonsignificant hemodynamic change was observed in the placebo subsets, and FDP failed to exert any effect in subsets 1, 2 and 3. A 24% (p less than 0.02) increase in cardiac index occurred 60 minutes after FDP in subset 4. LV stroke work index also increased, while PA wedge pressure remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased congestive heart failure after myocardial infarction of modest extent in patients with diabetes mellitus

To elucidate the factors involved in the reduced survival rate of diabetic patients after acute myocardial infarction (AMI), we prospectively evaluated 100 patients with well-documented diabetes and 426 control patients. We characterized infarct size and analyzed the incidence and severity of congestive heart failure (CHF) and subsequent death with respect to infarct size. The extent of the index infarct was less in diabetic compared to nondiabetic patients, 16.2 +/- 2.2 CK-gm-eq/m2 compared with 19.2 +/- 0.9 (p less than 0.02). However, CHF was more prevalent in diabetic patients (31.2% of the diabetic patients compared to 15.7%). The difference was most prominent in diabetic patients who had sustained prior infarction (50% compared to 16%), but was evident also in diabetic patients with initial infarction (26% compared to 16%). The mortality rate was greater in diabetic patients (p less than 0.04). When diabetic and nondiabetic patients were stratified with respect to the presence or absence of CHF, survival curves were comparable. The increased incidence of CHF despite a smaller infarct size suggests that additional factors must contribute to myocardial dysfunction and the resultant excess in mortality.

A protective effect of insulin on reperfusing the ischaemic rat heart shown using 31P-NMR

The effect on the recovery of mechanical function, ATP, phosphocreatine, Pi and pH of various lengths of total global ischaemia in the insulin-treated, perfused rat heart has been studied using 31P-NMR. Insulin-treated hearts recovered stable mechanical function after 18 min ischaemia when their intracellular pH was 6.0 and 70% of the pre-ischaemic ATP remained. Hearts perfused without insulin fail to recover after 18 min ischaemia, having an intracellular pH of 6.3 and 40% of ATP remaining (Bailey, I.A., Seymour, A.-M.L. and Radda, G.K. (1981) Biochim, Biophys. Acta 637, 1-7). Thus, ATP maintenance in ischaemia is more important to recovery on reperfusion than is maintaining intracellular pH. The importance of this observation in devising biochemical strategies for the clinical protection of the myocardium is discussed.

The effects of insulin and potassium on infarcting canine tissue: an in vitro study

The electrophysiologic effects of insulin (40 mU/ml) and elevated potassium (4 to 6 mM) on glucose-superfused normal and infarcting tissue from 24 hour coronary artery ligated canine myocardium were studied. With standard intracellular microelectrode techniques, it was observed that insulin infusion for 30 minutes produced an increase in resting membrane potential and a prolongation of action potential duration. In the normal myocardium, the hyperpolarization and the repolarization delay were minimal, but in infarcting tissue with depressed electrophysiologic function, resting membrane potential and action potential duration were significantly improved. This was particularly evident in the presence of an increased potassium concentration (6 mM) when insulin hyperpolarized infarcting cells (n = 8) from 73 +/- 6 to 85 +/- 7 mV (p less than 0.01). In the same studies, action potential amplitudes were increased from 75 +/- 7 to 95 +/- 11 mV (p less than 0.01). In addition, action potential durations at 40 and 80% repolarization were extended from 64 +/- 25 and 141 +/- 46 ms to 132 +/- 34 and 198 +/- 27 ms, respectively (p less than 0.01). Thus, these data are in accord with the reduced ST segment elevation observed in patients treated with glucose-insulin-potassium and support the use of this intervention in the management of acute infarction.

Influence of myocardial substrate utilization on the oxygen consumption of the heart

The effect of changing myocardial metabolism from predominantly lipid to predominantly carbohydrate utilization on myocardial oxygen consumption (MVO2) was studied in 10 closed-chest dogs. Oxygen saving potency of different metabolic interventions was quantified over a wide hemodynamic range by comparing the directly determined MVO2 with the hemodynamic parameter total left ventricular energy demand (Et), which correlates closely under control conditions with MVO2 (r = 0.98). Stimulation of carbohydrate metabolism by addition of glucose and beta-pyridyl carbinol or by activation of pyruvate dehydrogenase with dichloroacetate (DCA) shifted the cardiac respiratory quotient during beta-stimulation from 0.73 to 1.00 and 0.89, respectively, the nonesterified fatty acid/albumin ratio decreased from 4.0 to 0.5, or remained unchanged with DCA, and MVO2 was reduced by 25 and 16%, respectively. Therapeutic approaches aimed at decreasing MVO2 by changing substrate utilization are discussed.

Comparison of enzymic with cineangiocardiographic estimations of myocardial infarct size

Comparisons were made between enzymic indices of myocardial infarct size (total creatine kinase appearance and peak enzyme activity) measured during the acute state of a first myocardial infarct in 32 male patients, and analysis of contraction abnormalities in biplane left ventricular cineangiocardiograms performed one month later. The cineangiocardiograms were analysed independently by two radiologists, each using two different methods for quantification of subjectively classified abnormalities of left ventricular wall motion. A very strong correlation was found between the two enzymic indices of infarct size and somewhat weaker correlations between assessment of contractility abnormalities made by the two radiologists using the same method, or by the same radiologist using the two different methods. Comparisons between enzymic and angiocardiographic indices for all infarcts showed correlation coefficients (r) within the range of 0.53 to 0.72. With all comparisons of enzymic with radiological indices r values were higher for anterior infarcts than for inferior infarcts, and there was a tendency for higher enzyme levels for a given degree of left ventricular damage in inferior than in anterior infarction. This may be the result of variable degrees of right ventricular damage in inferior infarction.