Effect of intravenous insulin infusion on mortality among diabetic patients after myocardial infarction

Association of silent hypoglycemia with cardiac events in non-diabetic subjects with acute myocardial infarction undergoing primary percutaneous coronary interventions

Background

Some studies have shown that hypoglycemic episodes in diabetic patients might be associated with increased cardiovascular events. It is not clear whether episodes of silent hypoglycemia had greater prognostic value on cardiac events compared with normoglycemia or hyperglycemia in non-diabetic patients, so the aim of this study was to investigate the association of silent hypoglycemia and cardiac events in non-diabetic patients with acute ST-segment elevation myocardial infarction (STEMI) who underwent primary percutaneous coronary intervention (p-PCI).

Methods

We enrolled non-diabetic patients with STEMI who underwent p-PCI and whose clinical and laboratory data were collected. Interstitial glucose values were recorded using a continuous glucose monitoring system (CGMS), and Holter monitoring was recorded for 3 days in parallel. Cardiac ischemia and ventricular arrhythmia was evaluated.

Results

Based on the inclusion and exclusion criteria, we enrolled 164 STEMI patients undergoing p-PCI for final analysis. A total of 280 episodes of silent hypoglycemia (CGMS glucose <70 mg/dl) were recorded. Episodes of silent cardiac ischemia were recorded in 50 of 280 hypoglycemic episodes. The incidence of silent cardiac ischemia during hypoglycemia was significantly higher than the incidence during both hyperglycemia and normoglycemia(P < 0.01). Moreover, we found a significantly higher frequency of ventricular extrasystoles (VESs) or nonsustained ventricular tachycardias (NSVTs) in patients with silent hypoglycemia. The average number of events of silent cardiac ischemia was also significantly increased in the silent hypoglycemia group (0.91 ± 0.82 vs. 0.35 ± 0.54, P < 0.01) compared with either hyperglycemia or normoglycemia group.

Conclusions

Hypoglycemia was frequent and most of the time asymptomatic in non-diabetic patients with STEMI undergoing p-PCI. Silent hypoglycemia was associated with silent cardiac ischemia. STEMI patients with silent hypoglycemia had a significantly higher frequency of VESs or NSVTs.

Acute hyperglycaemia enhances oxidative stress and aggravates myocardial ischaemia/reperfusion injury: role of thioredoxin-interacting protein

Hyperglycaemia during acute myocardial infarction is common and associated with increased mortality. Thioredoxin-interacting protein (Txnip) is a modulator of cellular redox state and contributes to cell apoptosis. This study aimed to investigate whether or not hyperglycaemia enhances Txnip expression in myocardial ischaemia/reperfusion (MI/R) and consequently exacerbates MI/R injury. Rats were subjected to 30 min. of left coronary artery ligation followed by 4 hrs of reperfusion and treated with saline or high glucose (HG, 500 g/l, 4 ml/kg/h intravenously). In vitro study was performed on cultured rat cardiomyocytes subjected to simulated ischaemia/reperfusion (SI/R) and incubated with HG (25 mM) or normal glucose (5.6 mM) medium. In vivo HG infusion during MI/R significantly impaired cardiac function, aggravated myocardial injury and increased cardiac oxidative stress. Meanwhile, Txnip expression was enhanced whereas thioredoxin activity was inhibited following HG treatment in ischaemia/reperfusion (I/R) hearts. In addition, HG activated p38 MAPK and inhibited Akt in I/R hearts. In cultured cardiomyocytes subjected to SI/R, HG incubation stimulated Txnip expression and reduced thioredoxin activity. Overexpression of Txnip enhanced HG-induced superoxide generation and aggravated cardiomyocyte apoptosis, whereas Txnip RNAi significantly blunted the deleterious effects of HG. Moreover, inhibition of p38 MAPK or activation of Akt markedly blocked HG-induced Txnip expression in I/R cardiomyocytes. Most importantly, intramyocardial injection of Txnip siRNA markedly decreased Txnip expression and alleviated MI/R injury in HG-treated rats. Hyperglycaemia enhances myocardial Txnip expression, possibly through reciprocally modulating p38 MAPK and Akt activation, leading to aggravated oxidative stress and subsequently, amplification of cardiac injury following MI/R.

Acute Phase Hyperglycemia among Patients Hospitalized with Acute Coronary Syndrome: Prevalence and Prognostic Significance

OBJECTIVES

Regardless of diabetes status, hyperglycemia on arrival for patients presenting with acute coronary syndrome, has been associated with adverse outcomes including death. The aim of this study is to look at the frequency and prognostic significance of acute phase hyperglycemia among patients attending the coronary care unit with acute coronary syndrome over the in-hospital admission days.

METHODS

The study included 287 consecutive patients in the Al-Faiha Hospital in Basrah (Southern Iraq) during a one year period from December 2007 to November 2008. Patients were divided into two groups with respect to admission plasma glucose level regardless of their diabetes status (those with admission plasma glucose of <140 mg/dl (7.8 mmol/L) and those equal to or more than that). Acute phase hyperglycemia was defined as a non-fasting glucose level equal to or above 140 mg/dl (7.8 mmol/L) regardless of past history of diabetes.

RESULTS

Sixty one point seven percent (177) of patients were admitted with plasma glucose of ³140 mg/dl (7.8 mmol/L). There were no differences were found between both groups regarding the mean age, qualification, and smoking status, but males were predominant in both groups. A family history of diabetes, and hypertension, were more frequent in patients with plasma glucose of ³140 mg/dl (7.8 mmol/L). There were no differences between the two groups regarding past history of ischemic heart disease, stroke, lipid profile, troponin-I levels or type of acute coronary syndrome. Again heart failure was more common in the admission acute phase hyperglycemia group, but there was no difference regarding arrhythmia, stroke, or death. Using logistic regression with heart failure as the dependent variable we found that only the admission acute phase hyperglycemia (OR=2.1344, 95% CI=1.0282-4.4307; p=0.0419) was independently associated with heart failure. While male gender, family history of diabetes mellitus, hypertension and diabetes were not independently associated with heart failure.

CONCLUSION

Admission acute phase hyperglycemia of ³140 mg/dl (7.8 mmol/L) was associated with heart failure in this study.

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

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

Acute myocardial infarction in diabetic patients

All patients hospitalized during a 3-year period with an acute myocardial infarction were followed for the occurrence of reinfarction or death. The patients with diabetes mellitus (n = 95) were compared with the non-diabetic population (n = 545). The diabetics had a higher mortality rate (relative death rate of 1.44 vs. 0.93, p less than 0.01) and a higher frequency of reinfarctions (18.9 vs. 10.8%, p = 0.04) than the non-diabetic population. A larger proportion of the diabetics had suffered a previous infarction, but the excess mortality was also present in those without a previous infarction. Established risk factors for death after myocardial infarction, such as age, infarct size, infarct localization and heart size, could not account for the difference in mortality. It is suggested that the increased mortality among the diabetics may be due to an increase in the rate of progression of the atherosclerotic heart disease.

Effects of intravenous nicorandil before reperfusion for acute myocardial infarction in patients with stress hyperglycemia

OBJECTIVE

Stress hyperglycemia increases the risk of mortality and poor outcomes in patients with acute myocardial infarction (AMI). We aimed to assess effects of intravenous nicorandil administered before reperfusion on AMI patients with stress hyperglycemia.

RESEARCH DESIGN AND METHODS

This study consisted of 158 consecutive first AMI patients with stress hyperglycemia who underwent percutaneous coronary intervention (PCI) within 24 h from the onset. They were randomly assigned to receive 12 mg of nicorandil (n = 81) or a placebo (n = 77) intravenously just before reperfusion. Stress hyperglycemia was defined as a blood glucose level > or =10 mmol/l (180 mg/dl). We examined various aspects of epicardial flow and microvascular function as immediate data and major adverse cardiac events (MACEs) (coronary heart disease death or unplanned readmission due to congestive heart failure) as late-phase data.

RESULTS

The incidence of slow flow after PCI was lower in the nicorandil group (13.6 vs. 27.3%, P < 0.04). ST segment resolution >50% was observed in 70.4 and 53.2% on nicorandil and placebo, respectively (P < 0.03). Patients treated with nicorandil had a lower peak creatine kinase level (3,137 +/- 2,577 vs. 4,333 +/- 3,608, P < 0.02). Upon Kaplan-Meier analysis, 5 years' freedom from MACEs was 86.4% in the nicorandil group and 74.0% in the placebo (P < 0.05).

CONCLUSIONS

Adjunctive therapy with administration of intravenous nicorandil before reperfusion on AMI patients with stress hyperglycemia significantly improves epicardial flow and prevents the occurrence of severe microvascular reperfusion injury, resulting in better outcomes in these patients.

A single serum glucose measurement predicts adverse outcomes across the whole range of acute coronary syndromes

OBJECTIVES

To analyse the relation between serum glucose concentration and hospital outcome across the whole spectrum of acute coronary syndromes.

METHODS

This was a prospective cohort study of 2127 patients presenting with acute coronary syndromes. The patients were stratified into quartile groups (Q1 to Q4) defined by serum glucose concentrations of 5.8, 7.2, and 10.0 mmol/l. The relation between quartile group and major in-hospital complications was analysed.

RESULTS

The proportion of patients with acute myocardial infarction increased incrementally across the quartile groups, from 21.4% in Q1 to 47.9% in Q4 (p < 0.0001). The trend for frequency of in-hospital major complications was similar, particularly left ventricular failure (LVF) (Q1 6.4%, Q4 25.2%, p < 0.0001) and cardiac death (Q1 0.7%, Q4 6.1%, p < 0.0001). The relations were linear, each glucose quartile increment being associated with an odds ratio of 1.46 (95% confidence interval (CI) 1.27 to 1.70) for LVF and 1.52 (95% CI 1.17 to 1.97) for cardiac death. Although complication rates were higher for a discharge diagnosis of acute myocardial infarction than for unstable angina, there was no evidence that the effects of serum glucose concentration were different for the two groups, there being no significant interaction with discharge diagnosis in the associations between glucose quartile and LVF (p = 0.69) or cardiac death (p = 0.17). Similarly there was no significant interaction with diabetic status in the associations between glucose quartile and LVF (p = 0.08) or cardiac death (p = 0.09).

CONCLUSION

Admission glycaemia stratified patients with acute coronary syndromes according to their risk of in-hospital LVF and cardiac mortality. There was no detectable glycaemic threshold for these adverse effects. The prognostic correlates of admission glycaemia were unaffected by diabetic status and did not differ significantly between patients with acute myocardial infarction and those with unstable angina.

Is blood glucose an independent predictor of mortality in acute myocardial infarction in the thrombolytic era?

OBJECTIVES

This study was designed to assess the prognostic significance of hyperglycemia in acute myocardial infarction (AMI) in the thrombolytic era using contemporary criteria for hyperglycemia.

BACKGROUND

Most studies that have examined this issue were performed before the widespread use of disease-modifying therapies and varied in their definition of hyperglycemia, assessment of risk factors, and reported outcomes.

METHODS

There were 1,664 consecutively hospitalized patients with AMI between October 1997 and October 1998 from a disease-specific, population-based registry. Patients were stratified according to history of diabetes mellitus and, further, according to whether they had a blood glucose >198 mg/dl (11 mmol/l). The influences of cardiac risk factors, medications, and interventions were analyzed, and multivariate logistic regression was used to determine the influence of blood glucose on mortality.

RESULTS

In patients without a history of diabetes, glucose levels were < or =198 mg/dl in 1,078 patients (Group 1) and >198 mg/dl in 135 (Group 2). Of those with diabetes, glucose levels were < or =198 mg/dl in 169 patients (Group 3) and >198 mg/dl in 282 (Group 4). Compared with Group 1 patients, the odds ratios (95% confidence interval) for in-hospital mortality among those in Groups 2, 3, and 4 were 2.44 (1.42 to 4.20; p = 0.001), 1.87 (1.05 to 3.34; p = 0.035), and 1.91 (1.16 to 3.14; p = 0.011), respectively. These groups also had greater 12-month mortality.

CONCLUSIONS

Hyperglycemia in AMI is associated with poor outcome even among patients without known diabetes. This finding underlines the need for aggressive glucose management in this setting and may support a more vigorous screening strategy for early recognition of diabetes.

Diabetes mellitus increases short-term mortality and morbidity in patients undergoing coronary artery bypass graft surgery

OBJECTIVES

The aim of this study was to determine the impact of diabetes mellitus (DM) on short-term mortality and morbidity in patients undergoing coronary artery bypass surgery (CABG).

BACKGROUND

Diabetes mellitus is present in approximately 20% to 30% of patients undergoing CABG, and the impact of diabetes on short-term outcome is unclear.

METHODS

We performed a retrospective cohort study in 434 hospitals from North America. The study population included 146,786 patients undergoing CABG during 1997: 41,663 patients with DM and 105,123 without DM. The primary outcome was 30-day mortality. Secondary outcomes were in-hospital morbidity, infections and composite outcomes of mortality or morbidity and mortality or infection.

RESULTS

The 30-day mortality was 3.7% in patients with DM and 2.7% in those without DM; the unadjusted odds ratio was 1.40 (95% confidence interval [CI], 1.31 to 1.49). After adjusting for other baseline risk factors, the overall adjusted odds ratio for diabetics was 1.23 (95% CI, 1.15 to 1.32). Patients treated with oral hypoglycemic medications had adjusted odds ratio 1.13; 95% CI, 1.04 to 1.23, whereas those on insulin had an adjusted odds ratio 1.39; 95% CI, 1.27 to 1.52. Morbidity, infections and the composite outcomes occurred more commonly in diabetic patients and were associated with an adjusted risk about 35% higher in diabetics than nondiabetics, particularly among insulin-treated diabetics (adjusted risk between 1.5 to 1.61).

CONCLUSIONS

Diabetes mellitus is an important risk factor for mortality and morbidity among those undergoing CABG. Research is needed to determine if good control of glucose levels during the perioperative time period improves outcome.

Managing myocardial infarction in the diabetic patient

Myocardial infarction is the leading cause of death among persons with diabetes. Recent advances in the understanding and treatment of cardiovascular disease in diabetes have made it increasingly important to tailor therapy when treating this high-risk population. Because patients with diabetes are at significantly higher risk for complications and death from MI, these patients are most likely to benefit from early and aggressive therapeutic intervention. Strong recommendations can be given for the use of beta-blockers, ACE inhibitors, and thrombolysis when indicated in the management of acute MI in the diabetic patient. Acetylsalicylic acid is also likely to be beneficial with little risk of adverse events in this setting. In the absence of more definitive data, cautious use of mechanical intervention in diabetic patients is recommended. The use of intravenous insulin therapy may benefit diabetic patients during the acute phase of MI, but more definitive studies are required before it can be recommended for broad use.

Beneficial and detrimental effects of intensive glycaemic control, with emphasis on type 2 diabetes mellitus

Diabetes mellitus is a major health problem in the world. Several clinical trials have shown that some of the major complications of diabetes mellitus can be partially prevented or delayed by intensive glycaemic control. However, there are benefits and risks in aiming for near normal blood glucose levels. Intensive glycaemic control delays the onset and progression of retinopathy, nephropathy and neuropathy. Epidemiological and observational studies have shown that cardiovascular events may be correlated with the severity and duration of diabetes mellitus, but major randomised trials have only shown weak and nonsignificant benefits of intensive glycaemic management in decreasing event rates. A modest improvement in lipid profile results from blood glucose control although, in the majority of cases, not enough to reach current targets. Detrimental effects of intensive glycaemic control include bodyweight gain and hypoglycaemia. Controversial issues in the management of patients with diabetes mellitus include the unproven increase in cardiovascular morbidity from sulphonylureas and hyperinsulinaemia, and the still unknown long term effects of newer oral antihyperglycaemic agents alone or in combination with traditional therapies (such as sulphonylureas and metformin). It is important to individualise management in setting glycaemic goals. Control of cardiovascular risk factors through blood pressure and lipid control and treatment with aspirin (acetylsalicylic acid) and ACE inhibitors have consistently shown benefits in the prevention of both macro- and microvascular complications in patients with diabetes mellitus; these measures deserve priority.

Stress hyperglycaemia and increased risk of death after myocardial infarction in patients with and without diabetes: a systematic overview

BACKGROUND

High blood glucose concentration may increase risk of death and poor outcome after acute myocardial infarction. We did a systematic review and meta-analysis to assess the risk of in-hospital mortality or congestive heart failure after myocardial infarction in patients with and without diabetes who had stress hyperglycaemia on admission.

METHODS

We did two searches of MEDLINE for English-language articles published from 1966 to October, 1998, a computerised search of Science Citation Index from 1980 to September, 1998, and manual searches of bibliographies. Two searchers identified all cohort studies or clinical trials reporting in-hospital mortality or rates of congestive heart failure after myocardial infarction in relation to glucose concentration on admission. We compared the relative risks of in-hospital mortality and congestive heart failure in hyperglycaemic and normoglycaemic patients with and without diabetes.

FINDINGS

14 articles describing 15 studies were identified. Patients without diabetes who had glucose concentrations more than or equal to range 6.1-8.0 mmol/L had a 3.9-fold (95% CI 2.9-5.4) higher risk of death than patients without diabetes who had lower glucose concentrations. Glucose concentrations higher than values in the range of 8.0-10.0 mmol/L on admission were associated with increased risk of congestive heart failure or cardiogenic shock in patients without diabetes. In patients with diabetes who had glucose concentrations more than or equal to range 10.0-11.0 mmol/L the risk of death was moderately increased (relative risk 1.7 [1.2-2.4]).

INTERPRETATION

Stress hyperglycaemia with myocardial infarction is associated with an increased risk of in-hospital mortality in patients with and without diabetes; the risk of congestive heart failure or cardiogenic shock is also increased in patients without diabetes.

Management of diabetes and hyperglycaemia during myocardial infarction: review of the literature

For many years now, research has firmly demonstrated the increased mortality in patients with diabetes following myocardial infarction (MI), a prognosis which has persisted despite major advances in acute coronary care. Research has also shown higher than usual mortality rates in patients without known diabetes presenting with hyperglycaemia during MI. Due to a lack of research evidence, little has been established about how best to manage glycaemic control in these patients during the acute phase of an MI. However, a recent clinical trial has had considerable impact on coronary care practice. It advocates intravenous insulin therapy for all diabetics and patients with hyperglycaemia during acute MI, followed by subcutaneous insulin for three months, regardless of previous treatment. The evidence for mortality benefit is substantial, but the trial has left some questions unanswered. The aim in this literature review is to examine critically the research basis for using insulin during and after MI, and to identify the potential impact of the research on patients and nurses. The author searched the CINAHL and MEDLINE indexes for relevant texts in English from 1975 to 1998, and has recently implemented relevant knowledge from this research into her own work area, a coronary care unit in the north of England.

Diabetes and myocardial infarction

Myocardial infarction (MI) is a common cause of mortality in people with diabetes. The case fatality from MI is high and may be reduced by thrombolysis and treatment with aspirin, beta-blockers and angiotensin-converting enzyme inhibitors. Poor metabolic control is common among diabetic patients with MI, but the importance of controlling blood glucose during and following an MI is debatable. Treatment with statins reduces cardiovascular end-points in diabetic patients with previous MI (secondary prevention). Large studies in diabetic patients without existing heart disease have shown statistically insignificant reductions in heart disease and MI with improved glycaemic control of the diabetes (primary prevention). The treatment of hypertension in people with diabetes prevents cardiovascular end-points, and studies on whether the treatment of hyperlipidaemia reduces heart disease and MI are proceeding.

Diabetic control in the patient with acute myocardial infarction

Diabetes mellitus affects 2% of the population and up to 5% of people over 65 years of age (Thomas, 1993). Diabetic patients have more coronary artery disease and a higher mortality from acute myocardial infarction (AMI) than the rest of the population (Patmore and Jennings, 1996). They have similar-size infarcts to those without diabetes, but the total mortality post-MI is higher (Karlson et al, 1993). This article examines the literature on AMI in diabetic patients to ascertain the most effective management of these patients and hence improve their prognosis.

Randomized trial of insulin-glucose infusion followed by subcutaneous insulin treatment in diabetic patients with acute myocardial infarction (DIGAMI study): effects on mortality at 1 year

OBJECTIVES

We tested how insulin-glucose infusion followed by multidose insulin treatment in diabetic patients with acute myocardial infarction affected mortality during the subsequent 12 months of follow-up.

BACKGROUND

Despite significant improvements in acute coronary care, diabetic patients with acute myocardial infarction still have a high mortality rate.

METHODS

A total of 620 patients were studied: 306 randomized to treatment with insulin-glucose infusion followed by multidose subcutaneous insulin for > or = 3 months and 314 to conventional therapy.

RESULTS

The two groups were well matched for baseline characteristics. Blood glucose decreased from 15.4 +/- 4.1 to 9.6 +/- 3.3 mmol/liter (mean +/- SD) in the infusion group during the 1st 24 h, and from 15.7 +/- 4.2 to 11.7 +/- 4.1 among control patients (p < 0.0001). After 1 year 57 subjects (18.6%) in the infusion group and 82 (26.1%) in the control group had died (relative mortality reduction 29%, p = 0.027). The mortality reduction was particularly evident in patients who had a low cardiovascular risk profile and no previous insulin treatment (3-month mortality rate 6.5% in the infusion group vs. 13.5% in the control group [relative reduction 52%, p = 0.046]; 1-year mortality rate 8.6% in the infusion group vs. 18.0% in the control group [relative reduction 52%, p = 0.020]).

CONCLUSIONS

Insulin-glucose infusion followed by a multidose insulin regimen improved long-term prognosis in diabetic patients with acute myocardial infarction.

Acute myocardial infarction in diabetic patients in the thrombolytic era

To examine the benefits of thrombolytic therapy in diabetic patients with acute myocardial infarction a retrospective study of all diabetic and non-diabetic patients with acute myocardial infarction admitted to the coronary care unit of the General Hospital, Birmingham between January 1984 and December 1987 was made and findings compared to corresponding groups admitted between January 1990 and May 1992 when thrombolytic therapy was routine. In-hospital mortality and morbidity were assessed in 208 diabetic and 1029 non-diabetic patients with acute myocardial infarction admitted 1984 and 1987 and in 115 diabetic and 501 non-diabetic patients with myocardial infarction between January 1990 and May 1992. Following the introduction of thrombolytic therapy, there was a reduction in mortality among non-diabetic patients from 17% to 8.5%; p < 0.001 (observed reduction: 49%; 95% CI: 30-70%) and in the incidence of left ventricular failure (from 22% to 8%, p < 0.1 (observed reduction: 52%; 95% CI: 40-85.5%). Diabetic patients showed a reduction in mortality from 30% to 17%; p = 0.02 (observed reduction: 42%; 95% CI: 9.4-73.8%) and in the incidence of left ventricular failure from 39% to 21%; p < 0.01 (observed reduction: 45%; 95% CI: 20.3-72.5%). Thrombolytic therapy confers a major benefit on diabetic patients with acute myocardial infarction, although this group remains at a prognostic disadvantage compared to non-diabetic patients.

Ex vivo effect of insulin on normal and diabetic rat hearts hypoperfused with norepinephrine

The effect of ex vivo insulin on contractile and energy metabolism dysfunctions was examined during hypoperfusion (0.6 ml/min per g heart weight) with 10(-6) M norepinephrine in isolated non-diabetic and streptozotocin-diabetic rats hearts. Insulin (2 mU/min per g heart weight) was infused for 15 min before as well as during 60-min hypoperfusion. Insulin significantly reduced the elevated diastolic tension in diabetic hearts (from 3.8 to 0.7 delta g), but not in non-diabetic hearts (from 1.4 to 1.2 delta g). Insulin partly improved the ATP decrease in the subendocardium of the left ventricle of the diabetic hearts (from 3.5 to 10.2 mumol/g dry weight) but did not affect non-diabetic hearts (from 6.9 to 6.8 mumol/g dry weight). Insulin also partly improved the creatine phosphate decrease and the inorganic phosphate increase in diabetic hearts only. Lactate accumulation was greater in non-diabetic than in diabetic hearts, even in the presence of insulin (77 vs. 45 mumol/g dry weight). The results indicate that acute intracoronary application of insulin in diabetic hearts improves hypoperfusion with norepinephrine injury to a level above that of non-diabetic hearts, but does not improve a less severe injury in non-diabetic hearts.

Microangiopathy as a prognostic indicator in diabetic patients suffering from acute myocardial infarction

Diabetic patients have an increased mortality following myocardial infarction (MI) due to left ventricular failure rather than larger infarcts or dysrhythmias. As this may be due to diabetic microangiopathy affecting the myocardium, we have examined the case records of diabetic clinic patients admitted to the Coronary Care Unit (CCU) with proven MI and compared the hospital outcome of those with and without retinopathy or nephropathy, i.e. markers for generalised microangiopathy. Sixty four consecutive records were traced, for the period when diabetic treatment policy was standardised in CCU, 24 patients had retinopathy (7 proteinuria). When compared to non-retinopathy patients they had similar ages 67 +/- 12 yr [+/- SD] v 63 +/- 9yr) but were of longer duration of diabetes p less than 0.05). There were no differences between the groups in size or site of infarct, previous infarct or hypertension history, blood glucose on admission or diabetic treatment before or after admission. Death occurred in 29% of retinopathy patients compared to 3% of non-retinopathy patients (p less than 0.01). Cardiac failure complicated 75% of retinopathy patients and 25% of non-retinopathy patients (p less than 0.001). Dysrhythmia occurred in 50% and 33% of patients respectively (P = NS). Nine patients had clinical peripheral vascular disease and five of these died. This study, of a selected group of diabetic clinic attenders admitted to CCU with acute MI, demonstrates that microangiopathy and peripheral vascular disease are important prognostic factors in determining hospital outcome as these patients are at increased risk of cardiac failure and death.

Metabolic control in diabetic subjects following myocardial infarction: difficulties in improving blood glucose levels by intravenous insulin infusion

Optimal metabolic control during the first twelve hours after myocardial infarction may be associated with improved survival in diabetic subjects. A comparison of an intravenous insulin infusion regimen aimed at improving blood glucose levels (n = 35), with 'routine control' (n = 34) in the post infarction period has been carried out in diabetic subjects admitted to four Coronary Care Units over a two year period. However, glycaemic control was similar in both groups (intravenous infusion regimen, mean +/- SD capillary blood glucose 10.3 +/- 2.1 mmol/l, 'routine control' glucose 10.7 +/- 3.6 mmol/l). There were no differences in the rates of arrhythmias (31% v 32%), heart failure (46% v 47%) or mortality (17% v 18%). Mortality in diabetic subjects was lower than that quoted in previous studies but was higher than in non-diabetic subjects admitted to the Coronary Care Unit during the same period. Attempts to improve glycaemic control by means of intravenous insulin infusion were unsuccessful.

Improvement of hypoperfusion with norepinephrine injury by ex vivo insulin in isolated diabetic rat hearts

Effects of insulin on contractile and energy metabolic dysfunctions during hypoperfusion (2 ml/min/g heart wt., 60 min) with 10(-6) M norepinephrine were studied in paced hearts isolated from streptozotocin-diabetic rats. Insulin (2 mU/min/g heart wt.) was infused 20 min before and during hypoperfusion (pre-treated group) or 30 min after the onset of hypoperfusion (post-treated group). Hearts in the non-treated group were hypoperfused without insulin and other hearts in the control group were not hypoperfused. In the non-treated group, resting contractile force (CF) and resting left ventricular pressure (LVP) were significantly elevated to maximum levels within 30 min after hypoperfusion and these elevations were restored in the pre-treated group but not in the post-treated group. Developed CF was depressed in the non-treated group and improved significantly in the pretreated group but not in the post-treated group. Developed LVP was depressed in the non-treated group, and depression was slightly larger in the pre-treated group. In the non-treated group, ATP and creatine phosphate contents in the left ventricle significantly decreased. Decreases in ATP and creatine phosphate contents in the inner layer were partially restored in the pre-treated group but not in the post-treated group. Lactate significantly increased in the non-treated group and increased even further in the insulin treated groups. These results indicate that contractile dysfunction during hypoperfusion with norepinephrine is improved by pre-treated insulin, as is partial recovery of energy metabolism.

Coronary blood flow in chronic insulin-dependent diabetic dogs

Diabetic patients appear to be at an increased risk for perioperative morbidity and mortality following coronary artery bypass grafting. Many have suggested that microangiopathy is a primary cause. Using radionuclide labelled microspheres, we measured the perfusion of the subendocardium, midmyocardium, subepicardium, and the subendocardium/subepicardium ratio in alloxan-induced diabetic and normal dogs. We found no statistical difference in the myocardial perfusion of dogs made diabetic for five months when compared to normal dogs. By using repeated measures two-factor analysis of variance-regression model, changing blood glucose levels had no effect on coronary blood flow in either the diabetic or normal dogs.

Raised concentrations of glucose and adrenaline and increased in vivo platelet activation after myocardial infarction

Plasma concentration of beta thromboglobulin was used as an index of in vivo platelet activation in 36 patients after acute myocardial infarction. Twelve patients had diabetes, seven had pulmonary oedema or cardiogenic shock (pump failure) or both, and 17 had uncomplicated infarcts. On the first day of admission, concentrations of beta thromboglobulin were higher in the patients with diabetes and those with pump failure than in those with uncomplicated infarcts. Concentrations of beta thromboglobulin in the non-diabetic patients were studied by multiple regression analysis and were significantly associated with plasma concentrations of adrenaline, pump failure, and glucose but not with noradrenaline or infarct size. When all subjects were considered together, glucose, adrenaline, and pump failure were associated with the beta thromboglobulin concentration but diabetes was without significant effect. Hyperglycaemia and raised plasma adrenaline concentration after myocardial infarction may activate platelets, and this could contribute to poor outcome in such patients.

Increased myocardial contractility during intravenous insulin infusion in type 1 (insulin-dependent) diabetic patients: an echocardiographic study

On two occasions eight insulin-dependent diabetic patients were connected to an artificial beta-cell, and insulin was administered by continuous intravenous infusion at a rate of 2 mU/kg/min, producing a moderate hyperinsulinaemia (mean 116 microU/ml). At random, blood glucose was kept constant by concomitant glucose infusion, or allowed to decrease to a mean value of 5.3 mmol/l. M-mode echocardiography was performed before, at 90 and at 180 min of insulin infusion. Following the euglycaemic insulin infusion periods, the fractional shortening of the left ventricle increased from 38.2% to 41.0 and 40.2%, respectively (p less than 0.02). The diastolic diameter (pre-load) and end-systolic meridional wall stress (after-load) remained constant in this experiment. In contrast, no change in fractional shortening could be demonstrated during falling blood glucose, possibly because pre-load was altered to a significant degree during this experimental condition. In conclusion, concomitant infusion of insulin and glucose, producing an euglycaemic hyperinsulinaemia, is followed by increased myocardial contractility.

The relationship of hospital admission and fatality from myocardial infarction to glycohaemoglobin levels

We have performed a study to assess the relative contributions of increased hospital admission rates with acute myocardial infarction and increased hospital case fatality to the excess mortality of subjects with elevated levels of glycohaemoglobin from myocardial infarction. Glycohaemoglobin levels were estimated by isoelectric focussing in 397 subjects without known diabetes mellitus admitted with myocardial infarction and compared with a control population reconstructed from a community sample of 1084 subjects without known diabetes mellitus screened in general practice. In the case-control comparison, glycohaemoglobin levels above the 90th centile were associated with relative risks of 3.1 (95% confidence interval 1.4-6.8) for admission with myocardial infarction and 5.3 (95% confidence interval 2.1-13.4) for death in hospital. Elevated glycohaemoglobin on admission was a predictor of both death and cardiac pump failure among those admitted with myocardial infarction, as was the presence of known diabetes. In those over 40 years of age, the top 1% of the glycohaemoglobin distribution contribute 4.3% of admissions and 9.6% of hospital deaths with myocardial infarction.

The extent of coronary artery disease in diabetic patients with myocardial infarction: an ECG study

In 91 non-diabetics (age 63 +/- 12, mean +/- SD, years range 31-94 years) and 85 patients with known diabetes or clearly abnormal levels of HbA1c (age 66 +/- 10 years, range 36-87 years) electrocardiograms were analysed sequentially after acute myocardial infarction (AMI). There was no significant difference in infarct site between the two groups. Generalized ischaemic change without ST elevation was seen in 33% of diabetics and 22% of non-diabetics (p greater than 0.1). In patients with transmural AMI, cardiogenic shock (CGS) was significantly commoner in diabetics (relative risk 3.1, CL 1.2-8.1) but there was no difference in the frequency of reciprocal change between the two groups. In both diabetic and non-diabetic patients the development of cardiogenic shock was more frequently associated with the presence of reciprocal change, the difference reaching significance in the diabetic group (chi 2 = 4.4, p less than 0.05). Thus cardiogenic shock in both diabetic and non-diabetic patients with AMI may be associated with the presence of extensive coronary artery disease, but differences in the prevalence of extensive disease do not explain the predisposition of diabetic patients to CGS.

Determinants and importance of stress hyperglycaemia in non-diabetic patients with myocardial infarction

Determinants of plasma glucose concentrations were studied in patients on admission to hospital with confirmed acute myocardial infarction but without previous glucose intolerance as evidenced by raised concentrations of glycosylated haemoglobin (HbAlc). Mortality in hospital increased significantly with increasing plasma concentrations of glucose in patients with both normal (p less than 0.0001, n = 311) and borderline (p less than 0.02, n = 70) concentrations of HbAlc. There was a weak relation between plasma glucose concentrations and infarct size as estimated by peak aspartate transaminase activity in both HbAlc groups (rs = 0.26, n = 101 and rs = 0.41, n = 35 respectively). A correlation was found between adrenaline and plasma glucose concentrations (r = 0.47, n = 27) and cortisol and plasma glucose concentrations (r = 0.75, n = 19), but the relation of plasma noradrenaline and plasma glucose suggested a threshold effect. Concentrations of adrenaline, but not those of noradrenaline or cortisol, correlated with infarct size as measured both by peak aspartate transaminase activity and cumulative release of creatine kinase MB isoenzyme. Multiple regression analysis showed that concentrations of cortisol, adrenaline, and noradrenaline (but not the concentration of HbAlc, infarct size, or age) are the main determinants of plasma glucose concentration measured in non-diabetic patients when admitted to hospital after acute myocardial infarction.

Myocardial infarct size and mortality in diabetic patients

The mortality rate from myocardial infarction is disproportionately high in diabetic patients. One explanation for this may be that diabetic patients incur more extensive myocardial necrosis. This possibility was examined in a three part study. Firstly, peak serum aspartate aminotransferase concentrations of all diabetic and non-diabetic patients admitted with myocardial infarction over a 16 year period were compared retrospectively. Secondly, peak aspartate aminotransferase concentrations in a series of diabetic patients and controls matched by age and sex were examined retrospectively. Thirdly, creatine kinase MB release and electrocardiographic measures of infarct size were investigated prospectively in a case/control study. Although cardiac failure and death were more common in the diabetic groups, there were no significant differences in estimates of infarct size between diabetic and non-diabetic patients in any of the studies. Therefore, the high case fatality rate amongst diabetic patients is not caused by increased myocardial damage. Presumably survival is prejudiced by factors operating before the infarction.

Myocardial infarct size and mortality in diabetic patients

The mortality rate from myocardial infarction is disproportionately high in diabetic patients. One explanation for this may be that diabetic patients incur more extensive myocardial necrosis. This possibility was examined in a three part study. Firstly, peak serum aspartate aminotransferase concentrations of all diabetic and non-diabetic patients admitted with myocardial infarction over a 16 year period were compared retrospectively. Secondly, peak aspartate aminotransferase concentrations in a series of diabetic patients and controls matched by age and sex were examined retrospectively. Thirdly, creatine kinase MB release and electrocardiographic measures of infarct size were investigated prospectively in a case/control study. Although cardiac failure and death were more common in the diabetic groups, there were no significant differences in estimates of infarct size between diabetic and non-diabetic patients in any of the studies. Therefore, the high case fatality rate amongst diabetic patients is not caused by increased myocardial damage. Presumably survival is prejudiced by factors operating before the infarction.

Myocardial infarct size and mortality in diabetic patients

The mortality rate from myocardial infarction is disproportionately high in diabetic patients. One explanation for this may be that diabetic patients incur more extensive myocardial necrosis. This possibility was examined in a three part study. Firstly, peak serum aspartate aminotransferase concentrations of all diabetic and non-diabetic patients admitted with myocardial infarction over a 16 year period were compared retrospectively. Secondly, peak aspartate aminotransferase concentrations in a series of diabetic patients and controls matched by age and sex were examined retrospectively. Thirdly, creatine kinase MB release and electrocardiographic measures of infarct size were investigated prospectively in a case/control study. Although cardiac failure and death were more common in the diabetic groups, there were no significant differences in estimates of infarct size between diabetic and non-diabetic patients in any of the studies. Therefore, the high case fatality rate amongst diabetic patients is not caused by increased myocardial damage. Presumably survival is prejudiced by factors operating before the infarction.

Effect of intravenous infusion of insulin in diabetics with acute myocardial infarction

Diabetes mellitus is associated with a high mortality after myocardial infarction. To see whether this may be decreased by improved diabetic control the effect of an insulin infusion regimen was studied in patients with acute myocardial infarction. From April 1982 to April 1983, 33 diabetics were admitted with acute myocardial infarction. Those being treated with diet alone or oral hypoglycaemic drugs continued with this unless control was poor, when they were changed to a "sliding scale" regimen of subcutaneous insulin injections thrice daily. Those already receiving insulin were maintained on thrice daily subcutaneous injections. From April 1983 to April 1984, 29 diabetics had acute myocardial infarction. Those receiving treatment with oral hypoglycaemic drugs or insulin were changed to continuous intravenous infusion of insulin, the aim being to maintain the blood glucose concentration at 4-7 mmol/I (72-126 mg/100 ml). Those being treated with diet alone continued with this if blood glucose concentrations were acceptable. Total mortality fell from 42% in the first year to 17% in the second (p less than 0.05). Over the same period mortality among non-diabetic patients with myocardial infarction did not change significantly. There was a significant fall in cardiac arrhythmias (expressed as the percentage of patients in whom arrhythmias were recorded) from 42% to 17% (p less than 0.05). The most significant fall in the incidence of complications occurred in those who had been receiving oral hypoglycaemic drugs on entry to the study (87% to 50%, p less than 0.05).

Myocardial infarction in the diabetic patient

It has long been thought that the symptomatology and prognosis of coronary events in patients with diabetes may differ from those in nondiabetic persons. A review of recent data demonstrates a higher mortality during the acute phase of myocardial infarction for diabetic patients than for their nondiabetic counterparts, possibly related to a higher incidence of congestive heart failure and cardiogenic shock. The clinical course of diabetic patients with infarction and the role of insulin in myocardial adaptation to ischemia are both reviewed. Diabetic patients surviving the acute phase of myocardial infarction have a lower survival in follow-up than nondiabetic survivors, although some improvement in survival has been noted following beta-adrenergic-blocker therapy.