Prospective study of heart disease in untreated maturity onset diabetics

Left ventricular function in newly diagnosed non-insulin-dependent (type 2) diabetics evaluated by systolic time intervals and echocardiography

Systolic time intervals (STI) and echocardiography were recorded in 133 (70 men, 63 women) newly diagnosed non-insulin-dependent diabetics aged 45-64 years and in 144 (62 men, 82 women) non-diabetic control subjects of the same age. Both male and female diabetics had significantly increased pre-ejection period/left ventricular ejection time ratio (PEP/LVET) in STI as compared with the respective non-diabetic control subjects. Male diabetics showed a reduced ejection fraction (EF) in echocardiography, but no significant difference was found in this respect between female diabetics and controls. A significant negative correlation was found between 2-hour postglucose serum insulin level and EF in male and female diabetics. After adjusting for the effect of age, coronary heart disease, hypertension, obesity and haemoglobin concentration, male diabetics still had a higher PEP/LVET ratio and a lower EF than male controls. In women, no significant differences were found between diabetics and controls in the PEP/LVET ratio or EF adjusted for the above factors. The results of this study are compatible with the view that impaired left ventricular function may be an early phenomenon in the clinical course of non-insulin-dependent diabetes.

Effect of correction of hyperglycemia on left ventricular function in non-insulin-dependent (type 2) diabetics

Systolic time intervals (STI) were recorded in 33 newly diagnosed non-insulin-dependent diabetics (19 men, 14 women, aged 44-64 years) before and after 3-8 months' dietary therapy. The mean (+/- SD) fasting blood glucose was 11.1 +/- 2.6 mmol/l before treatment and 7.8 +/- 1.8 at the second examination (p less than 0.001). Concomitantly with the decline in blood glucose concentration, the heart rate corrected pre-ejection period (PEP) decreased from 139 +/- 11.9 to 135 +/- 14.4 msec (mean +/- SD) (p less than 0.05), the heart rate corrected left ventricular ejection time (LVET) increased from 400 +/- 15.1 to 410 +/- 20.7 msec (p less than 0.0025) and the PEP/LVET ratio decreased from 0.39 +/- 0.06 to 0.36 +/- 0.06 (p less than 0.005). When the diabetics were divided into two groups according to the degree of the decline in blood glucose concentration, only those whose fasting blood glucose decreased by greater than or equal to 3 mmol/l showed significant changes in STI. No significant changes were observed in the mean heart rate or systolic blood pressure during the treatment. Cardiac dysfunction occurring in untreated non-insulin-dependent diabetics may be caused by metabolic factors and it may be reversed at least partially by correction of hyperglycemia.

Role of Exercise and Metabolism in Heart Failure with Normal Ejection fraction

Left ventricular dysfunction associated with metabolic disorders has a number of features that might shed light on the integrity of heart failure with normal ejection fraction. First, although these patients may be dyspneic and have a normal ejection fraction, their diastolic dysfunction is not isolated. Both experimental models and sensitive new parameters in humans have shown abnormal systolic function, even though the less sensitive parameters (such as ejection fraction) become abnormal only with stress. Moreover, the mechanistic contributors to myocardial dysfunction, including structural changes and metabolic influences on the cardiac myocyte, interstitial fibrosis, vascular disease, and altered loading, are likely to influence systolic as much as diastolic function. The responses of systolic and diastolic heart failure to exercise training show analogies, particularly with respect to the importance of peripheral adaptation, as well as a similar training response. Together, these features are more supportive of a continuum of pathophysiology between systolic and diastolic heart failure, rather than the 2 representing discreet phenomena.

The diabetic myocardium

Heart failure and diabetes mellitus are frequently associated, with diabetes potentiating the development of heart failure after other myocardial insults. This review documents the evidence in support of a specific primary myocardial disease in diabetes. The strongest clinical evidence relates to the detection of otherwise unexplained diastolic dysfunction in apparently healthy diabetic subjects, but recent studies with sensitive echocardiographic markers have shown systolic disturbances as well. The mechanism of this myocardial disease is multifactorial, with contributions from metabolic effects on the myocyte, structural changes in the myocardium and interstitium, autonomic neuropathy, and perhaps coronary vascular disease. The common pathway appears to be related to glycemic control and new evidence suggests better metabolic control to be beneficial, as well as angiotensin-converting enzyme inhibition and cross-link breakers.

Diabetic cardiomyopathy: evidence, mechanisms, and therapeutic implications

The presence of a diabetic cardiomyopathy, independent of hypertension and coronary artery disease, is still controversial. This systematic review seeks to evaluate the evidence for the existence of this condition, to clarify the possible mechanisms responsible, and to consider possible therapeutic implications. The existence of a diabetic cardiomyopathy is supported by epidemiological findings showing the association of diabetes with heart failure; clinical studies confirming the association of diabetes with left ventricular dysfunction independent of hypertension, coronary artery disease, and other heart disease; and experimental evidence of myocardial structural and functional changes. The most important mechanisms of diabetic cardiomyopathy are metabolic disturbances (depletion of glucose transporter 4, increased free fatty acids, carnitine deficiency, changes in calcium homeostasis), myocardial fibrosis (association with increases in angiotensin II, IGF-I, and inflammatory cytokines), small vessel disease (microangiopathy, impaired coronary flow reserve, and endothelial dysfunction), cardiac autonomic neuropathy (denervation and alterations in myocardial catecholamine levels), and insulin resistance (hyperinsulinemia and reduced insulin sensitivity). This review presents evidence that diabetes is associated with a cardiomyopathy, independent of comorbid conditions, and that metabolic disturbances, myocardial fibrosis, small vessel disease, cardiac autonomic neuropathy, and insulin resistance may all contribute to the development of diabetic heart disease.

Cardiac abnormalities in diabetic patients with neuropathy: effects of aldose reductase inhibitor administration

OBJECTIVE

The goal of this study was to determine whether treatment with an aldose reductase inhibitor (ARI) has beneficial effects on asymptomatic cardiac abnormalities in diabetic patients with neuropathy.

RESEARCH DESIGN AND METHODS

Diabetic subjects with neuropathy (n = 81) with either a low diastolic peak filling rate or impaired augmentation of left ventricular (LV) ejection fraction (LVEF) during maximal bicycle exercise were identified by gated radionuclide ventriculography. Coronary artery disease, left ventricular hypertrophy, and valvular heart disease were excluded by clinical evaluation, myocardial perfusion imaging, and echocardiography. Subjects were randomized to receive blinded treatment with either the placebo or the ARI zopolrestat 500 or 1,000 mg daily for 1 year.

RESULTS

After 1 year of ARI treatment, there were increases in resting LVEF (P < 0.02), cardiac output (P < 0.03), LV stroke volume (P < 0.004), and exercise LVEF (P < 0.001). In placebo-treated subjects, there were decreases in exercise cardiac output (P < 0.03), stroke volume (P < 0.02), and end diastolic volume (P < 0.04). Exercise LVEF increased with ARI treatment independent of blood pressure, insulin use, or the presence of baseline abnormal heart rate variability. There was no change in resting diastolic filling rates in either group.

CONCLUSIONS

Diabetic patients with neuropathy have LV abnormalities that can be stabilized and partially reversed by ARI treatment.

Magnetic resonance imaging analysis of cardiac cycle events in diabetic rats: the effect of angiotensin-converting enzyme inhibition

Non-invasive magnetic resonance imaging (MRI) was used to characterize changes in left and right ventricular cardiac cycles following induction of experimental, streptozotocin (STZ)-induced, diabetes in male Wistar rats at different ages. The effects of the angiotensin-converting enzyme (ACE) inhibitor captopril upon such chronic physiological changes were then evaluated, also for the first time. Diabetes was induced at the age of 7 weeks in two experimental groups, of which one group was subsequently maintained on captopril (2 g l(-1))-containing drinking water, and at 10 and 13 weeks in two further groups. The fifth group provided age-matched controls. All groups (each n = 4 animals) were scanned consistently at 16 weeks, in parallel with timings used in earlier studies that employed this experimental model. Cine magnetic resonance (MR) image acquisition provided transverse sections through both ventricles at twelve time points covering systole and most of diastole. These yielded reconstructions of cardiac anatomy used to derive critical functional indices and their dependence upon time following the triggering electrocardiographic R waves. The left and right ventricular end-diastolic (EDV), end-systolic (ESV) and stroke volumes (SV), and ejection fractions (EF) calculated from each, control and experimental, group showed matching values. This confirmed a necessary condition requiring balanced right and left ventricular outputs and further suggested that STZ-induced diabetes produced physiological changes in both ventricles. Absolute left and right ventricular SVs were significantly altered in all diabetic animals; EDVs and EFs significantly altered in animals diabetic from 7 and 10 but not 13 weeks. When normalized to body weight, left and right ventricular SVs had significantly altered in animals diabetic from 7 and 10 weeks but not 13 weeks. Normalized left ventricular EDVs were also significantly altered in animals diabetic from 7 and 10 weeks. However, normalized right ventricular EDVs were significantly altered only in animals made diabetic from 7 weeks. Diabetic hearts showed major kinetic changes in left and right ventricular contraction (ejection) and relaxation (filling). Both the initial rates of volume change (dV/dt) in both ventricles and the plots of dV/dt values through the cardiac cycle demonstrated more gradual developments of tension during systole and relaxation during diastole. Estimates of the derived left ventricular performance parameters of cardiac output, cardiac power output and stroke work in control animals were comparable with human values when normalized to both body (or cardiac) weight and heart rate. All deteriorated with diabetes. Comparisons of experimental groups diabetic from 7 weeks demonstrated that captopril treatment relieved the alterations in critical volumes, dependence of SV upon EDV, kinetics of systolic contraction and diastolic relaxation and in the derived indicators of ventricular performance. This study represents the first demonstration using non-invasive MRI of early, chronic changes in diastolic filling and systolic ejection in both the left and the right ventricles and of their amelioration by ACE inhibition following STZ-induction of diabetes in intact experimental animals.

Progression of functional and structural cardiac alterations in young normotensive uncomplicated patients with type 1 diabetes mellitus

OBJECTIVE

We have recently observed that in young, normotensive patients with a type I diabetes mellitus and no macro or microvascular complications, large artery structure and function are already altered. This study has been done to assess whether this condition is also characterized by early alterations in cardiac structure and function, and whether these alterations progress with time.

DESIGN AND METHODS

In 56 insulin-treated, normotensive uncomplicated type I diabetic patients (age 35.0 +/- 2 years, means +/- SE) in good metabolic control, left ventricular wall thickness and diameter were measured by echocardiography together with left ventricular ejection fraction and diastolic function E/A (ratio between early and late ventricular filling), before and after 23 +/- 1 months. The same measurements were made in 20 age and sex-matched subjects who served as controls (C).

RESULTS

Compared to C, diabetic patients had a significant increase in left ventricular wall (septal plus posterior wall) thickness (+ 8.4%), left ventricular mass index (+ 11%) and h/r ratio (left ventricular wall thickness/ventricular end diastolic diameter, + 16.0%) whereas they showed a reduction of E/A (-6%). In C, all echocardiographic values were unchanged after 2 years. This was the case also for diabetic patients, except for left ventricular ejection fraction and diastolic diameter which showed a significant reduction (-7.2%) and increase (+ 3.8%), respectively, with a reduction of ratio between LV wall thickness and diameter, h/r (-6.8%).

CONCLUSIONS

Uncomplicated type I diabetes mellitus is characterized by early structural and functional cardiac alterations. Some of these alterations show a measurable progression within a relatively short time span.

Is abnormal iodine-123-MIBG kinetics associated with left ventricular dysfunction in patients with diabetes mellitus?

BACKGROUND

Although autonomic neuropathy is frequently recognized in patients with diabetes mellitus, it is uncertain whether cardiac sympathetic neuropathy may play a role in the development of diabetic cardiomyopathy.

METHODS AND RESULTS

In 10 control subjects and 61 patients with diabetes mellitus who did not have coronary artery disease, cardiac sympathetic function and left ventricular ejection fraction (LVEF) were evaluated by using iodine-123-metaiodobenzylguanidine (MIBG) imaging and echocardiography, respectively. Dynamic acquisitions and planar images obtained 15 and 150 minutes after injection were used as a means of measuring early and late myocardial uptake and clearance rates of MIBG from the heart. Eight patients with an LVEF less than 50% demonstrated a lower late myocardial MIBG uptake (0.0043% +/- 0.0017% vs. 0.0024% +/- 0.0009%/pixel, P = .002) and a higher clearance rate (22.9% +/- 17.7% vs. 49.3% +/- 12.2%, P<.0001) than the 53 patients with an LVEF of 50% or greater, although the age, sex, type of diabetes mellitus, and frequency of neuropathy, retinopathy, and nephropathy were not significantly different between the 2 subgroups. The LVEF correlated weakly but significantly with early and late myocardial uptake and clearance rate (r = 0.277, P = .03; r = 0.421, P = .001; r = 0.382, P = .002; respectively) in patients with diabetes mellitus.

CONCLUSION

Marked MIBG abnormalities are associated with left ventricular dysfunction in patients with diabetes mellitus. However, long-term follow-up of patients with diabetes mellitus who have marked MIBG abnormalities and normal LVEF will be required to determine whether these patients would demonstrate systolic dysfunction earlier than patients without an MIBG abnormality.

Comparison of diabetic and non-diabetic patients referred for coronary angiography

AIM

To evaluate whether diabetic patients differ from non-diabetic patients when referred for coronary angiography regarding previous history, indication for and findings at coronary angiography, use of medication, exercise test results and mortality.

METHODS

Data were prospectively collected on patients referred for consideration of coronary revascularization to seven of the eight public Swedish heart centers that performed approximately 92% of all bypass operations in Sweden in 1994.

RESULTS

2762 patients were included of whom 406 (15%) had a history of diabetes mellitus. There was no difference in age or sex in the two groups. Chronic stable angina was the most common indication (73% in both groups) and only 3% were admitted due to silent ischemia. Diabetic patients had more severe symptoms (Canadian Cardiovascular Society III-IV) than non-diabetic patients (66% vs. 58%, p<0.01). They more frequently used ACE-inhibitors (33% vs. 19%, p<0.0001) and calcium channel blockers (47% vs. 40%, p<0.01) and more often had a diagnosis of arterial hypertension than non-diabetic patients (50% vs. 33%, p<0.0001). Diabetic patients more often had depressed myocardial function (EF<35%); 12% and 8%, respectively (p<0.01), and more extensive coronary artery disease (left main/3-VD; 48% vs. 37%, p<0.001). The mortality during the subsequent 21 months was 7.9% among diabetic patients and 3.6% among non-diabetic patients (p<0.001).

CONCLUSION

Among patients being referred for coronary angiography in Sweden, 15% were patients with a history of diabetes. They differed from patients without such a history by more often having severe symptoms and a higher prevalence of left main/triple vessel disease. Coronary angiography may thus be underused in diabetic patients with chest pain.

Diabetic cardiomyopathy

Prior to 1972, the increased cardiovascular morbidity and mortality that diabetics endure had been attributed to vascular disease. In 1972, Rubler et al. proposed the existence of a diabetic cardiomyopathy based on their expereince with four adult diabetic patients who suffered from congestive heart failure (CHF) in the absence of discernable coronary artery disease, valvular or congenital heart disease, hypertension, or alcoholism. Alternative explanations for CHF, such as anemia and vascular and renal disease in these four patients, gave rise to criticisms, but a wave of subsequent studies in the 1970s and 1980s provided credence to this new disease entity. This review of the studies done since 1972 appears to support the concept of a diabetic cardiomyopathy independent of atherosclerotic cardiovascular disease. The exact mechanism is still questionable, and several mechanisms have been proposed including small and microvascular disease, autonomic dysfunction, metabolic derangements, and interstitial fibrosis. However, the weight of evidence leans toward the development of fibrosis, possibly caused by the accumulation of a peroxidase acid schiff (PAS)-positive glycoprotein, leading to myocardial hypertrophy and diastolic dysfunction.

Effects of adenosine and isoprenaline in left atria from both neonatal and middle-aged noninsulin-dependent diabetic rat models

1. This study examined the ability of atria from neonatal and middle-aged noninsulin-dependent diabetic rat models to respond to both adenosine and isoprenaline. 2. Cumulative additions of adenosine (1-1000 microM) produced concentration-dependent decreases in the force of contraction of rat atria that were unchanged in neonatal diabetic animals. Although direct inotropic responses to adenosine were unchanged, atria from neonatal diabetic animals exhibited an increase in maximum response to adenosine-induced antiadrenergic effect. 3. Atria from middle-aged noninsulin-dependent diabetic rats exhibited a supersensitivity to the direct inotropic effect of adenosine compared with atria from age-matched control rats. The middle-aged, noninsulin-dependent diabetic state did not alter the maximum response of atria to adenosine-induced antiadrenergic effect. 4. A comparison was made between middle-aged (10-month-old) controls and young (4-month-old) controls. Atria from middle-aged control animals exhibited a lower sensitivity and responsiveness to the direct inotropic effect of adenosine compared with those from young controls. 5. Cumulative additions of isoprenaline (10(-9)-10(-6) M) produced concentration-dependent increases in inotropy that were unchanged in atria from either neonatal or middle-aged noninsulin-dependent diabetic rats. 6. These results show that neonatal and middle-aged noninsulin-dependent diabetes and age-related factors lead to significant changes in atrial reactivity to the adenosine-induced stimulation in the absence and presence of isoprenaline. However; isoprenaline-induced positive inotropic response cannot change in each diabetic heart to an apparent extent.

Changes in microsomal membrane phospholipids and fatty acids and in activities of membrane-bound enzyme in diabetic rat heart

Diabetes mellitus is associated with alterations in lipid metabolism and cardiac dysfunction despite an absence of coronary arteriosclerotic changes. To investigate mechanisms of cardiac dysfunction in diabetic cardiomyopathy, we studied the relation between activities of membrane-bound enzymes and surrounding phospholipids in rats with diabetes induced with a single intravenous injection of streptozotocin (65 mg/kg). We found that total phospholipid content of sarcoplasmic reticulum membrane increased significantly 8 weeks after treatment with streptozotocin owing to increases in phosphatidylcholine and phosphatidylethanolamine, a decrease in arachidonic acid, and an increase in docosahexaenoic acid in the early stage of diabetes. Sarcolemmal Na+/K(+)-ATPase activity and the number of receptors decreased in isolated cardiomyocytes of diabetic rats 8 weeks after streptozotocin administration. The Ca2+ uptake of both sarcoplasmic reticulum and mitochondria decreased simultaneously in permeabilized, isolated cardiomyocytes from diabetic rats. The depression of membrane-bound enzyme activities was correlated with alterations in phospholipids, which are closely related to the microenvironment of membrane-bound enzymes and influence intracellular Ca2+ metabolism. Because these changes in phospholipids and fatty acids were reversible with insulin therapy, they are diabetes-specific and might be a cause of cardiac dysfunction in diabetes.

Increased prevalence of large bites in 12-lead vectorcardiograms of diabetic patients

The vectorcardiographic (VCG) bites in diabetic patients were compared with those in nondiabetic control subjects using automated analysis of the conventional electrocardiogram (ECG). A 12-lead ECG was recorded from each of the 154 patients with non-insulin-dependent diabetes mellitus and 128 control subjects. The orthogonal leads X, Y, and Z were derived from the 12-lead ECG, from which a so-called 12-lead VCG was calculated for each of the 282 participants. A computer-based method for the detection and quantification of bites was applied to the 12-lead VCGs. Bite amplitudes in the horizontal loop had an average of 0.062 +/- 0.089 mV in the diabetic group, and 0.039 +/- 0.045 mV in the control group (P < .01). In the sagittal plane, the mean bite amplitude was also greater in the diabetic group than in the control group: 0.095 +/- 0.084 versus 0.069 +/- 0.058 mV, respectively (P < .01). A bite greater than 0.1 mV in the horizontal or sagittal planes was found in 56 diabetic patients (36%) and 27 control subjects (21%) with (P < .05) considered significant. In conclusion, the results of this study suggest that automated analysis of the 12-lead VCG can be valuable in diagnosing diabetic cardiomyopathy.

Myocardial alterations in diabetes and hypertension

Diabetes mellitus is a complex group of diseases that has hyperglycemia as a common metabolic abnormality. Although it is well-known that diabetic patients are susceptible to the effects of large vessel atherosclerosis with specific cardiac and cerebral complications, the association of diabetes mellitus with cardiac dysfunction caused by cardiomyopathy in the absence of significant coronary artery disease has been recognized for many years. However, the pathogenesis of diabetic cardiomyopathy remains unknown and has been somewhat controversial. Specifically, whether diabetes mellitus with its metabolic effects is sufficient to account for cardiomyopathy remains to be proven. This paper reviews the evidence for and against a metabolic etiology. In addition, we review the clinical and experimental evidence that supports the view that diabetes mellitus acts together with hypertension to produce structural damage in the heart that manifests as ventricular dysfunction and ultimately congestive heart failure. The concomitant effects of the metabolic derangements of diabetes and the vascular abnormalities associated with hypertension may lead to microvascular-induced tissue injury. Findings supporting this hypothesis are presented, along with observations suggesting that treatment with vasodilating calcium channel blockers or angiotensin converting enzyme inhibitors may be beneficial in regard to tissue pathology and mortality in experimental models. Recent clinical studies also support a role for the microcirculation in diabetics. Finally, it is suggested that if the microcirculation is pathogenetically involved in diabetic cardiomyopathy, then agents that improve microcirculatory flow along with tight control of hypertension may be as beneficial in the treatment or prevention of diabetic cardiomyopathy as strict metabolic control of hyperglycemia.

Ventricular repolarization is correlated with metabolic control in newly diagnosed type 2 diabetes

Good metabolic control may improve cardiac function in diabetic patients. It is not known, however, whether this functional improvement is associated with concomitant electrocardiographic changes. The aim of the present prospective study was to evaluate the quantitative electrocardiographic and vectorcardiographic correlates of metabolic control, left ventricular function and dimensions, and autonomic nervous function in patients with newly diagnosed Type 2 diabetes. We studied 35 patients (20 men, 15 women; age 52 +/- 6 years (mean +/- SD) with normal electrocardiograms at 1.5 and 15 months after the diagnosis of Type 2 (non-insulin-dependent) diabetes. During the follow-up, body weight decreased, and significant improvement was observed in metabolic control, cardiac function and autonomic nervous function. Concomitantly, maximal spatial vector of T wave increased from 238 +/- 122 to 284 +/- 141 microV (P < 0.01), and this increase was correlated with a decrease in glycosylated haemoglobin A1C (r = -0.45, P < 0.01) and plasma insulin (r = -0.46, P < 0.01). In addition, duration of QRS complex shortened from 94 +/- 9 to 92 +/- 8 ms (P < 0.05), and this shortening was correlated with an increase in heart rate variability (r = -0.34; P < 0.05) and a decrease in peak early to late left ventricular filling flow velocity (r = 0.35, P < 0.05). These changes were most prominent in patients with co-existing hypertension and coronary artery disease. In conclusion, improving metabolic control of diabetes is associated with changes in ventricular repolarization and shortening of QRS complex duration.

Diabetic cardiomyopathy

Diabetic cardiomyopathy as a distinct entity was first recognized by Rubler et al. in diabetics with congestive heart failure (CHF), who had no evidence of coronary atherosclerosis. The Framingham study showed a 2.4-fold increased incidence of CHF in diabetic men and a 5.1-fold increase in diabetic women over 18 years. Pathological studies show left ventricular hypertrophy and fibrosis with varying degrees of small vessel disease, the functional significance of which is uncertain. Hypertension was recognized as an important cofactor in the development of fatal congestive heart failure in diabetics. On cardiac catheterization, in patients symptomatic of heart failure, either congestive or restrictive patterns have been observed. In contrast, asymptomatic diabetics had decreased left ventricular compliance but normal systolic function on hemodynamic study. Noninvasive studies show alterations in systolic and especially diastolic function, particularly in diabetics with microvascular complications and/or coexistent hypertension. Using load-independent measures of contractility, however, systolic function was generally found to be normal in asymptomatic normotensive diabetics. Experimental studies have focused on the mildly diabetic dog and the severely diabetic rat. Decreased left ventricular compliance and increased interstitial connective tissue were observed in chronically diabetic dogs. In contrast, ventricular myocardium from diabetic rats exhibits a reversible decrease in the speed of contraction, prolongation of contraction, and a delay in relaxation. These mechanical changes are associated with a decreased myosin ATPase, a shift in myosin isoenzyme distribution, alterations in a variety of Ca2+ fluxes, and changes in responses to alpha- and beta-adrenergic and cholinergic stimulation. These biochemical changes may be secondary to alterations in carbohydrate, lipid, and adenine nucleotide metabolism in the diabetic heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Evolution of cardiac changes in young insulin-dependent (type 1) diabetic patients--one more piece of the puzzle of diabetic cardiopathy

Based on our recent reports that increased myocardial contractility has been found in newly diagnosed diabetic patients, and that diastolic (D) dysfunction precedes systolic (S) dysfunction, we suggested that the development of diabetic cardiopathy passes through the following stages: (I) increased myocardial contractility, (II) intact S and D function, (III) intact S function and D dysfunction, and (IV) S and D dysfunction. The aim of this pilot study was to test this hypothesis. One hundred fifty-seven young (26.2 +/- 7.4 years) cardiac-asymptomatic patients with type I diabetes and 54 healthy subjects were studied using M-mode echocardiography. The presence of at least one of the variables for systolic function (ejection fraction, mean velocity of circumference, fiber shortening, and stroke index) or diastolic function [left atrium emptying index (LAEI), EFo slope of anterior mitral leaflet, and isovolumetric relaxation time (IRT)] outside the control mean +/- 2 SD was interpreted as an increased or depressed myocardial contractility, and diastolic dysfunction, respectively. The severity of diabetic complications (retinopathy, nephropathy, and cardiac autonomic neuropathy) was evaluated by the diabetic complication index (DCI = 0 divided by 6 scores). Our hypothesis was confirmed significantly (p < 0.001) in 148 (94%) patients with diabetes. Duration of diabetes and DCI progressed significantly (ANOVA: F = 36.6, p < 0.001; F = 70.8, p < 0.001) with hypothetical stages. Diastolic dysfunction was more pronounced in stage IV than in stage III: IRT (80.5 +/- 18.6 ms vs. 62.5 +/- 16.4, p < 0.001), EFo (63 +/- 15 mm/s vs. 72 +/- 21, p < 0.05), LAEI (0.58 +/- 0.13 vs. 0.8 +/- 0.15, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between hyperglycaemia and aerobic power in men with newly diagnosed type 2 (non insulin-dependent) diabetes

The aim of the study described here was to evaluate aerobic function during exercise and its determinants in middle-aged men with newly diagnosed Type 2 (non insulin-dependent) diabetes. Using breath-by-breath technique, we measured O2 uptake at anaerobic (ventilatory) threshold and at peak exercise in a group of diabetic men (n = 19; fasting blood glucose 8.6 +/- 0.7 mmol l-1, mean +/- SEM) without any disease or medication that could have had an influence on exercise performance, and compared the results to those observed in non-diabetic healthy control men (n = 18). There were no differences in physical activity or smoking habits between the groups. Oxygen uptake was lower in the diabetic men than in the control men both at anaerobic threshold (15.0 +/- 0.8 vs. 18.8 +/- 1.0 ml min-1 kg-1, P < 0.01) and at peak exercise (25.3 +/- 1.5 vs. 31.1 +/- 1.4 ml min-1 kg-1, P < 0.01). In the diabetic men peak O2 uptake showed an inverse linear correlation with age (r = -0.71, P < or = 0.001), fasting blood glucose (r = -0.49, P < 0.05) and glucose response in an oral glucose tolerance test (r = -0.43, P < 0.05). In addition, long-term smoking was associated with impaired peak O2 uptake. In a stepwise multiple regression procedure 75% of the total variance of peak O2 uptake in the diabetic men was explained by age, post-load blood glucose response and smoking history. Thus, in addition to ageing and smoking, hyperglycaemia is correlated with impaired aerobic power in men with newly diagnosed Type 2 diabetes.

Anatomical and functional cardiac abnormalities in type I diabetes

To analyse the anatomy and systolic and diastolic cardiac function in a group of type I diabetics with no other abnormality and to correlate it with the duration of the disease, the presence of complications, the control of the diabetes and the abnormalities in the autonomous nervous system, 125 type I diabetics and 50 age- and sex-matched healthy controls were studied. In 112 diabetics, an echocardiographic image which enabled us to calculate the thickness, cavity dimensions and systolic function rates was obtained. A Doppler echocardiograph was done in all patients to measure 9 parameters of diastolic function. The autonomic nervous system was evaluated by the response to 4 cardiovascular reflexes. Two control groups and 4 study groups were established, based on duration and on the presence and number of microangiopathic complications. The results showed a significant increase in the septal and posterior wall thickness, although without differences between the study groups. There were no differences in the analysis of systolic function. The abnormalities in diastolic function were significant in all the groups, but greater in the groups with microangiopathy. Overall, for groups 1-4, respectively, the incidence of anatomical abnormalities was 9.6%, 17%, 28% and 57% (average 22%); systolic 0%, 0%, 4% and 4.7% (average 2.2%); and diastolic 15%, 21%, 60% and 80% (average 44%). Only 13 diabetics from group 4 presented with cardiac autonomic neuropathy. No correlation between these alterations and the glycaemic control or the duration of the disease was found, although there was a correlation between the presence or absence of complications and the anatomic and diastolic abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiomyopathy associated with noninsulin-dependent diabetes

Cardiovascular disease represents the major cause of morbidity and mortality in noninsulin-dependent diabetic patients. While it was once thought that atherosclerotic vascular disease was responsible for all of these adverse effects, recent studies support the notion that one of the major adverse complications of diabetes is the development of a diabetic cardiomyopathy characterized by defects in both diastolic and systolic function. Contributing to the development of the cardiomyopathy is a shift in myosin isozyme content in favor of the least active V3 form. Also defective in the noninsulin-dependent diabetic heart is regulation of calcium homeostasis. While transport of calcium by the sarcolemmal and sarcoplasmic reticular calcium pumps are minimally affected by noninsulin-dependent diabetes, significant impairment occurs in sarcolemmal Na(+)-Ca2+ exchanger activity. This defect limits the ability of of the diabetic heart to extrude calcium, contributing to an elevation in [Ca2+]i. Also promoting the accumulation of calcium by the diabetic cell is a decrease in Na+, K+ ATPase activity, which is known to increase [Ca2+]i secondary to a rise in [Na+]i. In addition, calcium influx via the calcium channel is stimulated. Although the molecular mechanisms underlying these defects are presently unknown, the possibility that they may be related to aberrations in glucose or lipid metabolism are considered. The evidence suggests that classical theories of glucose toxicity, such as excessive polyol production or glycosylation, appear to be insignificant factors in heart. Also insignificant are defects in lipid metabolism leading to accumulation of toxic lipid amphiphiles or triacylglycerol. Rather, the major defects involve membrane changes, such as phosphatidylethanolamine N-methylation and protein phosphorylation, which can be attributed to the state of insulin resistance.

Non-insulin-dependent diabetes-induced defects in cardiac cellular calcium regulation

Non-insulin-dependent diabetic (NIDD) male Wistar rats develop a cardiomyopathy approximately 9 mo after the onset of the diabetic condition. This cardiomyopathy is characterized by reduced contractility, relaxation, cardiac work, and diastolic compliance. Although the basis for these defects is not completely understood, altered cellular Ca2+ regulation appears to play a major role in their development. In both isolated sarcolemmal membrane and cardiomyocytes, significant diabetes-linked defects in Ca2+ metabolism were observed. A small, but significant, decrease in the rate of sarcolemmal ATP-dependent Ca2+ transport of the diabetic heart was observed. Also evident was a major defect in sarcolemmal Na(+)-Ca2+ exchange as determined by reduced Na(+)-dependent Ca2+ transport into vesicles and Na(+)-dependent Ca2+ efflux from 45Ca(2+)-loaded cardiomyocytes from diabetic rats. In isolated cardiomyocytes, it was observed that the relative fluorescence of fura-2 at 502 nm was higher in cells from NIDD hearts, suggestive of a higher cytosolic free Ca2+. Consistent with diabetes-linked defects in Ca(2+)-transporter activities, the accumulation of Ca2+ after depolarization with KCl was greater in the diabetic. This study demonstrates that diabetes-induced defects in Ca2+ movement by the various Ca2+ transporters lead to abnormal cytosolic Ca2+ regulation by the diabetic cardiomyocytes. This observation supports the notion that abnormal Ca2+ regulation contributes to the development of the NIDD cardiomyopathy.

Effect of diet therapy on maximum aerobic power in obese, hyperglycaemic men with recently diagnosed type 2 diabetes

To find out the effect of correction of hyperglycaemia on maximum aerobic power and anaerobic threshold, we studied 40 middle-aged obese men with recently diagnosed type 2 diabetes before and after 3 months diet therapy. Respiratory gas exchange was measured during maximal incremental bicycle exercise test with breath-by-breath technique at rest, at anaerobic threshold and at peak exercise. As a whole group, the diabetic men reached higher work load after therapy (+9 +/- 3 W (mean +/- SEM), p less than 0.01). A weak inverse linear correlation was found between the changes in fasting blood glucose and in maximum oxygen uptake (r = -0.29, p less than 0.05). When the patients were divided into two groups according to the median values in the change in fasting blood glucose, only those men with more than 1 mmol l-1 decrease in fasting blood glucose improved maximum oxygen uptake (+124 +/- 55 ml min-1 or +6%, p less than 0.05). Oxygen uptake at anaerobic threshold did not change significantly. These results suggest that the correction of hyperglycaemia by diet therapy may improve maximal aerobic power in obese men with recently diagnosed type 2 diabetes.

Diabetic heart muscle disease

Diabetic patients may have various abnormalities in left ventricular systolic and diastolic function not attributable to coronary heart disease, hypertension or other known cardiac disease. Although the exact causes of this diabetic heart muscle disease or "diabetic cardiomyopathy" are still incompletely understood, several mechanisms may contribute to it including disturbed myocardial energy metabolism, microvascular changes, structural changes in collagen, increased myocardial fibrosis, and cardiac autonomic neuropathy. Perhaps the most typical feature of diabetic heart muscle disease is an abnormal filling pattern of the left ventricle, suggesting reduced compliance or prolonged relaxation. Left ventricular systolic function is commonly normal at rest in asymptomatic diabetic patients, but it frequently becomes abnormal during exercise. The abnormalities in left ventricular systolic function may be partly reversible along with an improvement of metabolic control of diabetes. It is not known how frequently subclinical abnormalities in left ventricular function in diabetic patients result in clinically manifest heart failure.

Myocardial mechanics in young adult patients with diabetes mellitus: effects of altered load, inotropic state and dynamic exercise

The disease entity "diabetic cardiomyopathy" has been extensively described in young patients with diabetes in the absence of ischemic, hypertensive or valvular heart disease. The most convincing data have been a 30% to 40% incidence of decreased radionuclide angiographic left ventricular ejection fraction response to dynamic exercise. In the current study, the hypothesis was tested that this abnormal ejection fraction response was due to alterations in ventricular loading conditions or cardiac autonomic innervation (extrinsic factors), or both, rather than to abnormalities in intrinsic ventricular systolic fiber function (contractility). Twenty normotensive patients with diabetes (mean age 30 +/- 5 years, mean duration 15 +/- 6 years) and 20 age-matched normal subjects were studied. All patients with diabetes had a normal treadmill exercise tolerance test without evidence of myocardial ischemia. By radionuclide angiography, all normal subjects increased ejection fraction with exercise (62 +/- 4% to 69 +/- 6%; p less than 0.001). In contrast, 11 (55%) of 20 patients with diabetes maintained or increased ejection fraction with exercise (group 1; 62 +/- 4% to 69 +/- 6%; p less than 0.001) and 9 (45%) of 20 showed an exercise-induced decrease (group 2; 73 +/- 4% to 66 +/- 6%; p less than 0.001). No difference in the incidence of microangiopathy, as noted by funduscopic examination, was present between the diabetic groups. Despite the abnormal ejection fraction response to exercise in the group 2 patients with diabetes, all patients with diabetes had a normal response to afterload manipulation, normal baseline ventricular contractility as assessed by load- and heart rate-independent end-systolic indexes and normal contractile reserve as assessed with dobutamine challenge. Autonomic dysfunction did not explain the disparate results between the group 2 patients' radionuclide angiographic data and their load-independent tests of ventricular contractility and reserve. In addition, the high ejection fraction at rest in group 2 patients (73 +/- 4% versus 62 +/- 4% for normal subjects; p less than 0.001) was not related to the abnormal tests of autonomic function. Thus, when left ventricular systolic performance was assessed by load- and rate-independent indexes, there was no evidence for cardiomyopathy in young adult patients with diabetes who have normal blood pressure and no ischemic heart disease.

Diabetic cardiomyopathy

Diabetes mellitus is associated with an excessive cardiovascular morbidity and mortality. Although one frequently associates cardiac dysfunction with enhanced coronary atherosclerosis in diabetic patients, evidence has accumulated for the existence of a specific "diabetic" cardiomyopathy. Abundant literature evidence supports the concept of myocardial dysfunction separate from epicardial coronary disease in diabetic individuals. The relationship of myocardial dysfunction to the type, duration, and treatment of diabetes awaits further delineation. The relative pathogenic significance of the multiple factors that may alter myocardial performance in diabetic patients similarly awaits further elucidation.

Non-invasive evaluation of cardiac function in young patients with type 1 diabetes

Cardiac function was evaluated in 40 Type 1 diabetic patients aged less than 30 years and compared with 20 age- and sex-matched control subjects using resting and exercise electrocardiography, and echocardiography. The duration of diabetes was from 0.25 to 25 years (mean 10 years), and few patients had microvascular complications. Left ventricular end-diastolic and end-systolic diameters were similar in both groups, with no significant differences between the groups in mean thickness of the intraventricular septum and the posterior wall of the left ventricle. Fractional shortening and mean velocity of circumferential fibre shortening as indices of ventricular function were similar in both groups. Left ventricular hypertrophy (Minnesota Code 3,1) was observed in the resting electrocardiogram of 22 patients and 12 control subjects (NS), but no other significant abnormalities were observed. One diabetic patient developed asymptomatic ST segment depression during exercise electrocardiography. In conclusion, the chamber size, wall thickness, and systolic function of the left ventricle are normal in most young Type 1 diabetic patients who have few microvascular complications.

Diabetic heart disease: the clinical and pathological spectrum--Part I

Diabetes mellitus is a significant condition affecting major segments of all population groups studied. With the introduction of insulin and oral hypoglycemic therapy, and with better understanding of diet and weight control over the past half century, the primary causes of diabetic morbidity and mortality have shifted in varying proportions from metabolic derangements, infection, and renal insufficiency to different types of cardiovascular disease. Despite extensive clinical and laboratory research on the etiology, pathogenesis, and even the existence of cardiovascular disease associated with diabetes mellitus, however, considerable debate is still apparent in this field. Our purpose is to present an overview of the subject of diabetic heart disease, with a critical analysis of epidemiologic, clinical, and pathological data. Some of this material will be addressed from the perspective of research in this area over the past decade by one of us (SMF), particularly in experimental hypertensive and diabetic cardiomyopathy. However, overall, an attempt will be made to provide an objective and balanced analysis, in order to answer the question: does diabetic heart disease exist?

Left ventricular relaxation and filling pattern in diabetic heart muscle disease: an echocardiographic study

In order to study left ventricular function digitized M-mode-echocardiograms were analyzed. 34 patients with insulin-dependent diabetes mellitus (mean age 37.8 years, mean diabetes history 21.5 years) were compared with 35 healthy individuals (mean age 40.9 years). Only patients with negative exercise-ECG, normal 2-D-echocardiogram and normal systemic arterial blood pressure were enclosed. In diabetics the time-constant Te of free wall endocardial retraction was significantly prolonged (76.8 +/- 21.2 ms versus 64.0 +/- 7.9 ms in normals, p less than 0.005), the dimension change during early diastole (dD DS-ERF) was significantly reduced (54.5 +/- 13.1% versus 69.8 +/- 9% in normals, p less than 0.001) and the dimension change during atrial contraction phase (dD ACP) was significantly enlarged (23.4 +/- 14.4% versus 14.3 +/- 6.4% in normals, p less than 0.001). These data suggest that impaired left ventricular diastolic function can be found in patients with long standing insulin-dependent diabetes mellitus.

Glycosylation and cross-linkage of cardiac myosin in diabetic subjects: a post-mortem study

We have investigated the possibility that post-translational modification of myosin by protein glycosylation and cross-linking occurs in cardiac myosin. Left ventricular muscle was obtained at post-mortem from 6 diabetic and 7 non-diabetic subjects. Myosin was extracted from muscle and purified using Sephadex chromatography followed by protein concentration. Glycosylation was estimated using boronate affinity chromatography with the myosin dissolved in a pyrophosphate buffer, the glycosylated myosin being displaced with sorbitol. Cross-linkage was assessed by fluorescence at 440 nm upon excitation at 370 nm. Diabetic subjects had significantly higher levels (p less than 0.02) of glycosylated myosin (median 6.0% (range 3.8-6.6%] than non-diabetic subjects (median 2.4% (range 0.3-4.2%] but there was no difference in the degree of cross-linkage as assessed by fluorescence (diabetic median 9.8 (range 6.5-17.0) arbitrary units; non-diabetic median 9.7 (range 6.0-11.4) arbitrary units). Glycosylation of left ventricular myosin may be of relevance to the excess risk of congestive cardiac failure in diabetic patients.

Asymptomatic diabetic cardiomyopathy: a noninvasive study

Forty-nine diabetic patients (26 type I and 23 type II), free of cardiovascular disease symptoms, were compared with 32 controls in a noninvasive study of left ventricular (LV) function. Absence of ischemic cardiopathy was confirmed by routine investigations and an exercise electrocardiogram using 12 leads with a thallium-201 myocardial scintigraphy. Diabetic patients had (1) a significantly prolonged mean isovolumetric relaxation time (IVRT) assessed by M-mode echocardiography and phonomechanography; (2) a significantly reduced E-F slope; (3) an increased mean Weissler index (pre-ejection period/LV ejection time). The IVRT and E-F slope abnormalities reflect increased myocardial stiffness and impaired LV compliance. The increased Weissler index reflects impaired myocardial contractility. These abnormalities were not related to sex, age, duration of diabetes or to the presence or extent of complications. No significant difference was found between diabetic patients and controls for mean diastolic and systolic LV diameters, thickness of the posterior wall or of the interventricular septum, assessed by echocardiography, or for the ejection fraction, determined by radionuclide angiocardiography. Finally, more than half of the patients with a frankly abnormal IVRT, Weissler index and E-F slope had had diabetes for less than 5 years, some even less than 2 years, without complications. These data show: (1) evidence of LV dysfunction specific to diabetes and unrelated to ischemic cardiopathy and hypertension; (2) the possible involvement of a metabolic factor in this early asymptomatic LV abnormality rather than microangiopathy.

Effects of dynamic exercise and metabolic control on left ventricular performance in insulin-dependent diabetes mellitus

In subclinical diabetic cardiomyopathy, previous reports did not positively correlate the altered cardiac performance with metabolic parameters. Fifteen insulin-dependent diabetic subjects, without any clinical or instrumental evidence of heart diseases, were studied. Signs of diabetic microangiopathy were absent. Systolic time intervals, metabolic and hormonal parameters (blood glucose, free fatty acids, blood lactate and plasma norepinephrine) were evaluated at rest and after dynamic exercise during poor (MAGE 6.36 +/- 0.72 mmol/l) and good (MAGE 3.46 +/- 0.66 mmol/l) metabolic control, obtained by means of insulin therapy. Rest values of systolic time intervals were normal during poor and good metabolic control. After exercise, pre-ejection period/left ventricular ejection time ratio increased mainly during poor control as a result of an increased pre-ejection period: conversely, a smaller increase in pre-ejection period/left ventricular ejection time ratio occurred during good metabolic control. The exercise induced free fatty acids utilization did not occur during poor control as it occurred during good control. The percentage of increments in blood lactate was virtually identical in ketotic and non-ketotic patients and in normal subjects. High norepinephrine plasma levels were observed both at rest and during dynamic exercise in poorly controlled diabetic patients. Conclusively, testing of systolic time intervals after exercise might be useful in the detection of preclinical diabetic cardiomyopathy. The decreased cardiac functional reserve observed during poor control might be related to an altered energetic fuel utilization.

Relation of hemoglobin A1 and blood glucose to cardiac function in diabetes mellitus

To examine the relation of short- and long-term changes in glucose metabolism to cardiac function, radionuclide cineangiography and echocardiography were performed in 10 young insulin-dependent diabetic patients without clinical evidence of heart disease. Cardiac assessments were performed before and after both acute variations in blood glucose, and induction of chronic "tight glucose control" involving normalization of hemoglobin A1 concentrations. In diabetic patients, left ventricular (LV) ejection fraction (EF) at normal blood glucose concentration was indistinguishable from values in 11 normal subjects. However, during hyperglycemia (about 300 mg/dl), the average EF at rest was 61%, significantly higher than that during normoglycemia (56%, p less than 0.001). No significant change in LV diastolic dimension was noted in association with shifts between high and normal blood glucose concentrations. Normalization of hemoglobin A1 was achieved within 6 to 25 weeks. This alteration had no significant effect on LVEF, mitral valve E-F slope, or the response of systolic function to blood glucose levels. In addition, no correlation was found between LVEF and hemoglobin A1 concentrations in 4 of 5 evaluation periods. Thus, in young insulin-dependent diabetic patients without overt heart disease, variation in blood glucose concentration is associated with small but significant variation in EF at rest; normalization of hemoglobin A1 has no significant effect on LVEF or the response of systolic function to blood glucose levels.

Longitudinal changes in left ventricular diastolic function in hypertrophic cardiomyopathy

Digitised M-mode echocardiography was used to study the changes in left ventricular diastolic function over a 3-year period in 11 patients with hypertrophic cardiomyopathy an 14 normals. Compared to normal, in hypertrophic cardiomyopathy, isovolumic relaxation was prolonged (P less than 0.001) and mitral valve opening delayed relative to minimum dimension (P less than 0.001). There was a wide range of values for the peak rates of dimension increase and wall thinning, and although the means were normal, 6 and 8 patients respectively were outside the normal range. There were no significant mean changes in function during the 3.4 +/- 0.3 years of follow-up, but, in 3 patients, marked alterations in relaxation were observed. They showed a gross reduction in the delay in mitral valve opening (125 to 55 125 to 35 and 110 to 75 msec). There was little overall change in isovolumic relaxation in two, but in one patient it reduced from 95 to 50 msec. In most patients with hypertrophic cardiomyopathy, relaxation and diastolic function appear to remain stable over a period of 3 years, and none had an apparent deterioration. Some patients may have an apparently spontaneous "improvement" in function similar in extent to that described due to the therapeutic action of calcium antagonists.

[Existence of asymptomatic changes in left ventricular function in the diabetic. Noninvasive study]

49 diabetics (D) (26 IDD and 23 NIDD) were compared to 32 controls (C). Absence of ischemic cardiopathy (IC) was confirmed by routine investigations and noninvasive cardiovascular techniques, including an exercise ECG using 12 leads and a thallium 201 scintigraphy. Our results show: a) a prolonged mean isovolumetric relaxation time (IVRT) as studied by the M mode echocardiography and phonomechanography: D = 0,10 sec +/- 0,04; C = 0,05 sec +/- 0,02; p less than 0,0001; b) a reduced mean EF slope: D = 97,48 +/- 37,08 mm / sec; C = 125,68 +/- 34,35; p less than 0,005; c) a high mean Weissler index (ratio of PEP to LVET): D = 40 +/- 0,08; C = 33 +/- 0,05; p less than 0,01. IVRT and EF slope abnormalities are related to increased myocardial stiffness and impaired LV compliance. In the absence of changes in preload and afterload, the high Weissler index reflects impaired contractility of the myocardium. These abnormalities are related neither to the duration of diabetes nor to the presence or severity of the complications. With the M mode echocardiography, mean diastolic and systolic thickness of the septum is greater in D with retinopathy than in C (p less than 0,005 and p less than 0,03 respectively); mean diastolic and systolic thickness of the posterior wall is greater in NIDD than in C (p less than 0,001 and p less than 0,025). We conclude that there is evidence of left ventricular functional abnormalities specific to diabetes and unrelated to IC and hypertension. Our findings support the hypothesis that they may be due to metabolic disorders and/or myocardial microangiopathy.

Prevalence of coronary heart disease, left ventricular failure and hypertension in middle-aged, newly diagnosed type 2 (non-insulin-dependent) diabetic subjects

The prevalence of coronary heart disease, left ventricular failure and hypertension was examined in a representative group of 133 newly diagnosed Type 2 (non-insulin-dependent) diabetic subjects (70 men, 63 women), aged 45 to 64 years, and in a group of 144 randomly selected non-diabetic control subjects (62 men, 82 women) of the same age group. The prevalence of previous myocardial infarction (major Q-QS abnormalities in resting ECG and/or myocardial infarction verified at hospital) was increased 1.7-fold in male (NS) and 4.4-fold in female (p = 0.007) diabetic patients compared with that found in non-diabetic subjects. Chest pain symptoms and ischaemic ECG abnormalities were about twice as common among diabetic than among non-diabetic subjects. The frequency of coronary heart disease defined by chest pain symptoms and ECG abnormalities was 3.5 times higher in male (p = 0.001) and 3.1 times higher in female (p = 0.001) diabetic patients than in the respective non-diabetic subjects. The frequency of current digitalis therapy was increased 3.3-fold in male (p = 0.006) and 3.9-fold in female (p = 0.001) diabetic patients suggesting an increased frequency of left ventricular failure among diabetic subjects. The prevalence of hypertension, based on the elevated blood pressure levels and/or current use of antihypertensive drugs, was increased 1.6-1.7-fold among the diabetic patients.

Diabetic cardiomyopathy

Diabetes mellitus is associated with a specific cardiomyopathy. This is evident from the clinical-pathological work and the epidemiologic data from the Framingham study. Noninvasive studies of diabetics have shown alterations in systolic and diastolic function that may ultimately lead to clinical heart failure. The relationship of these cardiac changes to the type of diabetes, its duration, and its severity is not settled. However, a correlation between changes in heart function and other complications of diabetes has been demonstrated. Insufficient prospective data is available from noninvasive studies to establish the frequency of progression from subclinical cardiac dysfunction to overt congestive failure. The pathogenesis of this disorder is still uncertain. Pathological studies have shown changes in the intramural arteries, arterioles, and capillaries but their functional significance is uncertain. Experimental studies have shown interstitial changes leading to an apparently less compliant left ventricle in the diabetic dog and monkey. In the diabetic rat reversible changes were found in myocardial function, related to changes in contractile proteins and intracellular calcium metabolism. In both species, the response to anoxia or ischemia was altered in the presence of diabetes. However, irreversible depression of the contractile element was not found in most animal studies of isolated diabetes. In contrast, the combination of hypertension and diabetes leads to substantial cardiac damage and circulatory congestion, both in clinical and experimental investigations. Clearly much more work must be carried out to understand the pathogenesis, treatment, and ultimately the prevention of diabetic cardiomyopathy.

Combined renovascular hypertension and diabetes in rats: a new preparation of congestive cardiomyopathy

Myocardial function, electrophysiologic characteristics, and structure were studied in rats with both renovascular hypertension and streptozotocin-induced diabetes (HD). Ventricular papillary muscles from untreated rats with HD showed a marked slowing of isometric and isotonic contractions. Peak developed tension and peak shortening were preserved, except in one animal with findings of congestive heart failure. Transmembrane action potentials increased fivefold in duration. Myocardial interstitial fibrosis was frequently observed. Physiologic parameters of rats with HD treated by left nephrectomy, captopril, and insulin were very similar to those of age-matched controls. The mortality rate of rats with HD was 43% over 5 to 6 months in the first study. In a second study, spontaneously dying rats with HD were compared with those deliberately killed. A 55% mortality was observed over 7 months. Myocardial structural damage and histologic evidence of congestive heart failure were more frequent in spontaneously dying rats with HD. Combined renovascular hypertension and diabetes in rats appears to be a new preparation of congestive cardiomyopathy.

The heart in diabetes

Since the introduction of insulin, heart disease has become a major impediment to survival in persons with diabetes mellitus. Coronary disease has increased severity and accelerated development in diabetic persons compared with an age- and sex-matched nondiabetic population. A peculiar vulnerability of women to the influence of diabetes with loss of premenopausal coronary disease protection has been found. The symptomatology of coronary events may differ and coronary care data show a higher incidence of sudden death in diabetic patients who have a myocardial infarction than in their non-diabetic counterparts. Insulin may play a role in the myocardial adjustment to an ischemic insult by enhancing glucose intake and suppressing lipolysis and ketogenesis. Carbohydrate intolerance in dogs, rhesus monkeys and humans appears associated with similar histologic and compositional changes in the myocardium. Abnormalities in diastolic ventricular function not attributable to large- or small-vessel coronary disease have been found in the diabetic subjects of each species. Studies in humans who have diabetes have assessed single pressure-volume relationships and more exacting measures of ventricular compliance are needed. Abnormalities of myocardial function in patients with diabetes have been found using echo and radionuclide techniques. Many of these findings need to be correlated with invasive data or confirmed in larger populations. Autonomic dysfunction is common in diabetic persons and may imply an associated poor prognosis. Reflex abnormalities in parasympathetic function are most prevalent and occur before sympathetic dysfunction.

Preclinical abnormality of left ventricular performance in patients with insulin-dependent diabetes mellitus

The left ventricular systolic function of 32 patients with insulin-dependent diabetes mellitus was investigated by measurement of systolic time intervals. Patients with clinical signs of sclerosis in the coronary arteries were excluded. Twenty-nine sex- and age-matched healthy people served as controls. Resting values of PEP/LVET ratio and of the corrected pre-ejection period were significantly higher in diabetics than in controls. The alterations of systolic time intervals during volume-loading induced by passive leg-raising as well as by isometric handgrip test indicated an increase in left ventricular performance in healthy people. The unchanged systolic time intervals observed in diabetics during the same loadings indicated a decrease in the functional reserve of the diabetic left ventricle. The systolic time intervals observed in patients with type-1 diabetes could be evaluated as a preclinical abnormality of left ventricular performance and as early signs of diabetic cardiomyopathy.

Systolic time intervals in diabetes

The systolic time intervals at rest of 16 Type 1 (insulin-dependent) and 30 Type 2 (non-insulin-dependent) otherwise healthy adult diabetic patients selected from primary health care clinics were compared with those of age- and sex-matched normal subjects by paired analysis. There was no significant difference in prevalence of smoking, body mass index, fasting serum cholesterol or mean blood pressure between the diabetic and control groups. Mean rate-corrected pre-ejection period (diabetic patients: 132.7 +/- 2.1 ms, normal subjects: 134.6 +/- 3.5 ms (+/- SEM), left ventricular ejection time (diabetic patients: 413.9 +/- 3.0 ms, normal subjects: 421.5 +/- 4.7 ms) electromechanical systole (diabetic patients: 544.9 +/- 2.5 ms, normal subjects: 548.0 +/- 3.5 ms) and pre-ejection period/left ventricular ejection time ratio (diabetic patients: 0.36 +/- 0.01, normal subjects: 0.34 +/- 0.01) were not significantly different between the two groups (p greater than 0.05) and systolic time intervals did not correlate with duration of diabetes or type of treatment. Thus, we did not detect subclinical cardiomyopathy in healthy diabetic patients by this technique. However, a statistically significant skew in the distribution of systolic time intervals in the diabetic group (p less than 0.025) suggests the possibility of an 'at risk' population in which a more sensitive technique might demonstrate impaired ventricular performance.

Clinical trials of an antiplatelet agent, ticlopidine, in diabetes mellitus

At present there is no simple, reliable and non-invasive method for monitoring progression and improvement in diabetic microangiopathy. However, some diabetic patients with severe microvascular complications show a fairly specific pattern of impaired left ventricular function (abnormal relaxation, cavity filling and wall thinning) and abnormalities of haemorheology (increased viscosity, erythrocyte rigidity and beta-thromboglobulin and decreased threshold for platelet ADP aggregation). A single-blind, 6-months' crossover study of an antiplatelet agent, ticlopidine, was conducted in 20 diabetics with clinical evidence of microvascular disease. Response to therapy was monitored by digitised M-mode echocardiographic analysis of left ventricular diastolic function and haemorheology. All patients had abnormal basal values with no significant change during the 3-month placebo run-in period but, although significant alterations in viscosity, erythrocyte deformability, beta-thromboglobulins and ADP threshold were observed, no change in left ventricular function was detected. It is concluded that, while it may be possible to alter abnormal haemorheology in diabetes, there was no change in one parameter of microvascular end-organ damage.