Evidence for cardiomyopathy in familial diabetes mellitus

Heart rate/stroke volume relationship during upright exercise in long-term diabetics

The changes in stroke volume (SV) during upright exercise were studied in 20 insulin-dependent diabetics (IDDM) and 20 age- and sex-matched controls. None of the diabetics had any cardiovascular symptoms. In addition, tests of autonomic function were conducted in the diabetics, assessing changes in heart rate (HR) during deep breathing and the Valsalva maneuver. During exercise the SV in the controls gradually increased and then remained essentially unchanged until maximum HR was achieved. Seven of the diabetics failed to sustain an initial increase in SV (fall > 15%), eight showed a "delayed" increase in SV, and the remaining five demonstrated an increasing SV over the range from rest to peak exercise. Abnormal autonomic function results were found during deep breathing (four diabetics) and the Valsalva maneuver (four diabetics). Findings indicate that cardiac function could be abnormal in IDDM without evidence of autonomic dysfunction. This abnormality could be due to a specific cardiomyopathy.

Increased capillary permeability to albumin in diabetic rat myocardium

To clarify the mechanism for the well-known increase in microvascular permeability that occurs with diabetes mellitus, we investigated capillary permeability to albumin in diabetic rat myocardium by electron microscopy using albumin-gold (Alb-Au) complexes as a tracer. Diabetes was induced by an intravenous injection of streptozotocin. After 24-32 weeks, hearts from diabetic rats and age-matched control rats were perfused with Krebs-Henseleit bicarbonate buffer containing Alb-Au for 5 or 20 minutes and then fixed and processed for electron microscopy. The binding and transport of Alb-Au by capillary endothelium was quantitatively evaluated. In control rats, Alb-Au particles were found preferentially bound to the luminal plasmalemmal vesicles. In diabetic rats, the labeling of luminal vesicles was more extensive and more pronounced after 5 minutes of perfusion when compared with control vesicles. The plasma membrane proper was also heavily labeled in diabetic rats. After 20 minutes, Alb-Au particles were transported across the capillary endothelium via plasmalemmal vesicles, but they did not penetrate the intercellular junctions in either control or diabetic rats. The vesicular transport of Alb-Au across the capillary endothelium was significantly increased in the diabetic myocardium when compared with control myocardium (percentage of abluminal labeled vesicles, 25.9 +/- 5.5% versus 1.3 +/- 0.5%; p < 0.01). The study on food-restricted rats with body weights close to those of diabetic rats suggested that caloric deficiency alone did not have much effect on capillary permeability. The data indicate that capillary permeability to albumin is markedly increased in diabetic myocardium because of enhanced vesicular transport. This may play an important role in the pathogenesis of diabetic cardiomyopathy.

Mitochondrial DNA deletion in human myocardium

Mutation of myocardial mitochondrial DNA was investigated in human left ventricles obtained at autopsy using the polymerase chain reaction (PCR). Seventeen autopsy cases were examined, including patients with diabetes mellitus, myocardial infarction, cardiomyopathy, cancer, and other diseases. Two cases of diabetes mellitus, 2 of myocardial infarction, and 1 of pulmonary fibrosis showed a 7.4 kb deletion of myocardial mitochondrial DNA. Primer shift PCR confirmed that an amplified DNA fragment had not been obtained by misannealing of the primers. It is unclear how much these findings are related to the severity or prognosis of the various diseases, but they indicate that mutation of myocardial mitochondrial DNA can occur in other diseases besides cardiomyopathy, although the influence of aging could not be excluded.

Increased rat myocardial type VI collagen in diabetes mellitus and hypertension

Diabetic cardiomyopathy, a condition characterized by the accumulation of carbohydrate-containing material surrounding the myocardial small blood vessels, has been studied in alloxan-diabetic normotensive and hypertensive rats. Immunochemical techniques were used to monitor several extracellular matrix constituents present in extracts of cardiac tissue, namely types I, IV and VI collagen, laminin and fibronectin, as well as myosin. These studies have indicated that after induction of diabetes, type VI collagen but none of the other matrix components studied, was significantly increased (from 2.29 +/- 0.04 mg/g in normal to 2.85 +/- 0.18 mg/g in diabetic ventricles, p < 0.01). Hypertension, whether induced by the clipping of one renal artery or genetically determined (spontaneously hypertensive rats), resulted in a similar elevation in type VI collagen (2.71 +/- 0.12 mg/g, p < 0.005 compared to normal rats). In the presence of diabetes plus hypertension the effect was not additive, the type VI collagen level being 2.93 +/- 0.15 (p < 0.001 compared to normal rats). Basement membrane collagen (type IV) in the myocardium appeared to be unaffected by diabetes or hypertension and the myosin contents of the hearts of the four experimental groups were similar. Quantitative determinations indicate that compared to type IV collagen, laminin or fibronectin, type VI collagen represents the major periodic acid-Schiff-reactive extracellular constituent of the rat ventricle. Its preferential increase in the heart in diabetes may provide insight into the molecular mechanisms of the diabetic microvascular disease.

Collagen remodelling in myocardia of patients with diabetes

AIMS

To investigate collagen remodelling in the interstitium of the heart in patients with diabetes.

METHODS

Immunohistochemical study of the biopsied myocardium using type specific anticollagen antibodies (I, III, IV, V, VI) was performed in 12 patients with non-insulin dependent diabetes mellitus and six non-diabetic patients. There was no history of hypertension or coronary artery stenosis in any of the patients.

RESULTS

Noticeable accumulations of collagen types I, III, and VI in the myocardial interstitium were recognised in both groups, but little accumulation of types IV or V was found. Types I and III mainly stained in the perimysium and perivascular region, while type VI predominantly stained in the endomysium. There was no disease specific accumulation of collagen in diabetes mellitus. The percentage of total interstitial fibrosis in the myocardium was significantly higher in the diabetic group than in the control group (p < 0.05). Although the percentages of collagen types I and VI did not differ between the two groups, the percentage type of III was significantly higher in the diabetic group than in the controls (p < 0.01).

CONCLUSIONS

Collagen remodelling mainly as a result of an increase in collagen type III in the perimysium and perivascular region, occurs in the hearts of patients with diabetes.

Myocardial inositol and sodium in diabetes

Although inhibition of Na(+)-K+ ATPase has been described in the diabetic heart, K+ loss from myocardium has not been observed in a canine model of mild diabetes. The finding of tissue Na+ accumulation and a potential relation to alteration of left ventricular inositol as observed in other tissues in diabetes form the basis of this investigation. Diabetes was induced with alloxan in three groups of male mongrel dogs who were studied after 1 yr. In the initial experiment the tissue compartment volumes, determined with intravenous 51Cr EDTA as a marker, were found to be normal. Calculated cell sodium was increased to 32.8 +/- 2.6 mEq/kg cell H2O vs 18.7 +/- 1.1 in controls (p < 0.01). Cell potassium in diabetes was normal. In the second group, myocardial polyols were analyzed by gas-liquid chromatography. Inositol was diminished in diabetes to 0.61 +/- 23 microM/g of left ventricle, vs the respective control levels of 1.9 +/- 0.57 microM/g (p < 0.02). Sorbitol concentration was unaltered. Left ventricular sodium increments were not associated with altered tissue calcium. In group III the hypothesis that inhibition of Na(+)-K+ ATPase in diabetes might not elicit the expected alteration of K+ transport was assessed during intracoronary infusion of acetyl strophanthidin. No difference in cation responses from control was observed. It is postulated that a change in the conformation of Na(+)-K+ ATPase, with high affinity sodium binding sites facing the intracellular compartment, may render sodium less releasable from cell membrane.

Acute myocardial infarction in the diabetic patient: pathophysiology, clinical course and prognosis

Although there have been significant advances in the care of many of the extrapancreatic manifestations of diabetes, acute myocardial infarction continues to be a major cause of morbidity and mortality in diabetic patients. Factors unique to diabetes increase atherosclerotic plaque formation and thrombosis, thereby contributing to myocardial infarction. Autonomic neuropathy may predispose to infarction and result in atypical presenting symptoms in the diabetic patient, making diagnosis difficult and delaying treatment. The clinical course of myocardial infarction is frequently complicated and carries a higher mortality rate in the diabetic than in the nondiabetic patient. Although the course and pathophysiology of myocardial infarction differ to some degree in diabetic patients from those in patients without diabetes, much more remains to be known to formulate more effective treatment strategies in this high risk subgroup.

Partial correction of impaired creatine kinase activity in diabetic rat heart by physical training

The effect of physical training on total creatine kinase (CK), CK-MM, and CK-MB isoenzyme activity was studied in hearts of diabetic and control rats. Diabetes was induced with streptozotocin (50 mg/kg), and only rats with blood glucose levels between 14 and 22 mmol/L 1 week later were kept in the protocol. Exercise training was performed on a treadmill in a progressive 10-week program. Physical training did not induce any significant changes in plasma glucose or insulin levels in diabetic rats. Total CK, CK-MM, and CK-MB activity was decreased in diabetic rat heart by 27%, 22%, and 56%, respectively. Physical training did not induce any important changes in CK activity in heart of nondiabetic rats. However, in diabetic rat heart, training increased total CK activity by 13%, CK-MM activity by 12%, and CK-MB activity by 31%. We conclude that the decrease in cardiac CK activity observed in chronic experimental diabetes mellitus can be partly alleviated by a program of physical training. This may be one of the mechanisms whereby physical conditioning improves cardiac function in experimental diabetes.

Remodeling and reparation of the cardiovascular system

Growth or altered metabolism of nonmyocyte cells (cardiac fibroblasts, vascular smooth muscle and endothelial cells) alters myocardial and vascular structure (remodeling) and function. However, the precise roles of circulating and locally generated factors such as angiotensin II, aldosterone and endothelin that regulate growth and metabolism of nonmyocyte cells have yet to be fully elucidated. Trials of pharmacologic therapy aimed at preventing structural remodeling and repairing altered myocardial structure to or toward normal in the setting of hypertension, heart failure and diabetes are reviewed. It is proposed that these are therapeutic goals that may reduce cardiovascular morbidity and mortality. Although this hypothesis remains unproved the primary goal of therapy should be to preserve or restore tissue structure and function.

Preoperative evaluation for diabetic renal transplantation: impact of clinical, laboratory, and echocardiographic parameters on patient and allograft survival

OBJECTIVE

To assess the impact on renal transplant patients and graft survival of clinical, laboratory, and echocardiographic parameters commonly measured prior to surgery.

PATIENTS

Forty-seven consecutive diabetics with preoperative echocardiograms at the time of transplantation.

METHODS

Clinical history, standard chest roentgenogram, electrocardiogram, blood tests, echocardiograms, and HLA testing at baseline; follow-up from 2 to 7 years with periodic reassessment of graft function.

RESULTS

Patient survival did not appear to be influenced by age, sex, or type of allograft. A history of either myocardial infarction, congestive heart failure, or angina was present in 15 patients with 3-year survival of 50% (72% if not present, p less than 0.05). Histocompatibility testing did not impact on survival. Serum sodium, potassium, calcium, phosphate, and calcium-phosphate product did not discern different survival groups. A hematocrit greater than 30% was present in 15 patients with 3-year survival of 43% (73% if not present, p less than 0.05). Greater than 10% antibody sensitization of the recipient resulted in a 3-year survival of 38% in eight patients (68% if not present, p less than 0.05). Radiologic evidence of cardiomegaly or congestive heart failure and standard electrocardiographic evidence for left ventricular hypertrophy or strain did not impact on survival. Echocardiographic measurements of left ventricular end-diastolic diameter, posterior wall thickness, or ejection fraction were also not predictive. Increased end-systolic diameter (10 patients, 30% 3-year survival versus 69%, p less than 0.05) and decreased velocity of circumferential fiber shortening (11 patients, 45% 3-year survival versus 71%, p less than 0.05) both appeared to be related to survival. Increased accuracy of prediction could be obtained by adding risk factors so that a history of coronary artery disease and increased end-systolic diameter predicted 3-year survival of 42% versus 82% if neither was present. In terms of graft survival, no clinical, radiographic, or electrocardiographic result yielded predictive information. Among the laboratory tests, only highly antibody-sensitized patients (eight patients, 0% 3-year survival versus 66% 3-year survival, p less than 0.001) showed different survival patterns. Echocardiographic elevated end-systolic diameter predicted a significantly (p less than 0.001) decreased graft survival (3-year survival 33% versus 63%).

CONCLUSION

Preoperative prediction of patient and graft survival in diabetic renal transplantation may be enhanced by echocardiographic assessment of systolic load and function. For patients with normal systolic function, whose hematocrit is below 30%, with preformed antibodies less than 10%, renal transplantation has an excellent prognosis; invasive cardiac procedures are not likely required. Since these risk factors are likely additive, a high-risk group may be identified. These latter patients should undergo coronary angiography.

Abnormal myocardial acoustic properties in diabetic patients and their correlation with the severity of disease

Although patients with diabetes mellitus may be afflicted by cardiomyopathy, its prevalence and nature are controversial. Studies have shown that fibrosis alters the acoustic properties of the heart in animals and humans and that the changes are detectable by cardiac tissue characterization with ultrasound. The present study was performed to characterize myocardial acoustic properties in patients with insulin-dependent diabetes to determine whether ultrasound tissue characterization could detect changes potentially indicative of occult cardiomyopathy. The magnitude of cyclic variation of myocardial ultrasound integrated backscatter and its phase delay with respect to the onset of the cardiac cycle in the septum and posterior wall of the left ventricle were measured in 54 patients with diabetes who had no overt cardiac disease. Conventional echocardiography documented normal ventricular systolic function in 96%. As compared with results in age-matched patients without diabetes studied previously, cyclic variation of integrated backscatter was reduced (4.6 +/- 0.8 vs. 3.6 +/- 1.4 dB; p less than 0.001). In addition, delay was significantly increased (0.86 +/- 0.09 vs. 0.99 +/- 0.15). The primary analysis of the data focused on differences among the diabetic patients. Reduction of cyclic variation of backscatter was greatest in patients with diabetes who had neuropathy (3.2 +/- 1.0 dB; p less than 0.001) as was the increase in delay (1.04 +/- 0.16, p less than 0.001 vs. values in patients without neuropathy). Retinopathy and nephropathy were associated with abnormal myocardial acoustic properties as well. Thus, abnormalities that may reflect fibrosis or other occult cardiomyopathic changes in diabetic patients without overt heart disease are readily detectable by myocardial tissue characterization with ultrasound and parallel the severity of noncardiac diabetic complications.

Radionuclide assessment of left ventricular function in patients with myocardial infarction and diabetes mellitus

The aim of this study was to compare left ventricular function, assessed by radionuclide angiocardiography, in 54 diabetics and 194 non-diabetics with acute myocardial infarction (AMI). The most meaningful results concern the inferior AMI group, whose left ventricular ejection fraction (LVEF) and regional wall motion were significantly lower in diabetics than in non-diabetics (LVEF was 44.2 +/- 11 vs. 51.6 +/- 9%, P less than 0.005; the regional wall motion score was 0.46 +/- 1 vs. 1.56 +/- 1, P less than 0.01, respectively), while no significant difference was observed in the anterior AMI group. However, in the group as a whole, the LVEF was 41 +/- 13% in diabetics and 47 +/- 13% in non-diabetics (P less than 0.01), the number of abnormally contracting segments was 2.0 +/- 0.9 and 1.5 +/- 1, respectively, and the wall motion score was 0.2 +/- 1.1 and 1.0 +/- 1.4, respectively (P less than 0.01). These data could be explained by an underlying cardiac dysfunction in diabetes, in addition to AMI. The more marked difference between diabetics and non-diabetics in inferior AMI might be related to the smaller infarct size in this group.

Cardiovascular sequelae of endotoxin shock in diabetic dogs

Diabetic patients exhibit a higher incidence of post-surgical sepsis, as well as a higher rate of mortality from sepsis, than their non-diabetic counterparts. This may be a result of cardiovascular deterioration associated with diabetes mellitus. This study was designed to characterize the cardiovascular sequelae associated with endotoxin shock in a canine model of diabetes. Diabetes was induced with alloxan (50 mg/kg) and streptozotocin (30 mg/kg) in dogs weighing 19-25 kg. Thirty days later, anaesthetized dogs were instrumented to obtain blood pressures, blood samples, left ventricular chamber diameter, circumflex arterial blood flow, and aortic blood flow. Metabolic parameters were calculated according to the Fick principle, and myocardial inotropic state assessed with the end-systolic pressure-diameter relationship. After stable baseline measurements, Escherichia coli endotoxin (1 mg/kg) was infused over 1 h, and measurements were obtained every 30 min. After endotoxin administration diabetic dogs became more hypotensive than the non-diabetic dogs. Cardiac performance parameters were also depressed to a greater degree. These changes could be attributed to depressions in vascular resistance and myocardial inotropic state in diabetic dogs. Cardiac dysfunction occurred in association with a relative decrease in the supply to demand ratio for oxygen in the diabetic dogs, suggesting functional ischemia. Data indicating a decrease in pre-load and vascular resistance in the diabetic group suggest a greater degree of vascular collapse, vascular pooling, or extravasation of fluid than occurred in the non-diabetic group. These data support the hypothesis that the cardiovascular system of diabetic subjects cannot tolerate a septic insult as well as their non-diabetic counterparts.

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.

Diastolic ventricular function in type 1 diabetic patients: a study using Doppler echocardiography

The transmitral flow velocity pattern of 28 Type 1 diabetic patients and 39 age-matched healthy control subjects was studied for determination of left ventricular diastolic function. No patient had systemic hypertension, congestive heart failure, or ischaemic heart disease by clinical or electrocardiographic criteria. Echocardiographic measures of systolic ventricular function were within normal range in all subjects. The ratio of early to late transmitral peak flow velocity (ve/va) was significantly decreased in the diabetic patients (1.3 +/- 0.1 (+/- SE) vs 1.6 +/- 0.1, p less than 0.05), while other Doppler derived variables did not show any significant difference. No correlation of ve/va with duration of diabetes was found (r = -0.27), but it correlated with age in both groups (both r = -0.40, p less than 0.05). Furthermore, a significant correlation was found between ve/va and heart rate (r = -0.55 for diabetic patients, p less than 0.01; r = -0.58 for control subjects, p less than 0.01). After matching for heart rate (24 diabetic patients and 24 control subjects) no significant decrease of ve/va was observed in the diabetic group.

Reduced left ventricular afterload and increased contractility in children with insulin-dependent diabetes mellitus: an M-mode and Doppler-echocardiographic evaluation of left ventricular diastolic and systolic function

Twenty-three children with diabetes mellitus, their ages ranging from 0.2-9.8 years, but with no sign of diabetic microvascular disease were investigated by M-mode and Doppler echocardiography, along with a comparable group of control subjects. In the diabetics, the fractional shortening and the mean velocity of fractional shortening were 14 and 18% higher, respectively, whereas the left ventricular end-systolic wall stress, an indicator of left ventricular afterload, was markedly reduced (22%). Assuming an unchanged preload in the two groups, this indicates a reduced afterload in these children. Systolic and diastolic time intervals, heart rate, and blood pressure were similar in diabetics and controls. Doppler-derived transmitral left ventricular filling indices were also similar. Thus, in these diabetic children no signs of left ventricular diastolic abnormality were detected. The state of hypercontractility of the left ventricle is considered to be due to a reduced afterload in early insulin-dependent diabetes.

Echocardiographic study of left ventricular function in type 1 diabetes mellitus: hypersensitivity of beta-adrenergic stimulation

Systolic left ventricular function was investigated by echocardiography in 23 young, type 1 diabetics and 11 control subjects. A stimulation by isoproterenol was performed in order to study beta-adrenergic cardiac responsiveness. M-mode recordings were digitized and analyzed by computer. Systolic parameters such as left ventricular fractional shortening and mean velocity of circumferential shortening were not different, but maximal velocity of shortening was increased both at rest (P less than 0.01) and with isoproterenol (P less than 0.05) in the diabetics. An abnormal systolic anterior motion of the mitral valve was found during administration of isoproterenol in 65% of the diabetics and in only one control. These findings are suggestive of a hyperkinetic state, associated with a poor metabolic control (high value of HbA1), together with adrenergic hypersensitivity in type 1 diabetes mellitus.

Correlation between histopathological changes and mechanical dysfunction in diabetic rat hearts

Recent clinical and experimental studies have suggested that diabetic patients may develop myocardial dysfunction in the absence of coronary heart disease and hypertension. In this study, the correlation between histopathological changes and myocardial dysfunction was studied in experimental diabetic rat hearts. Male Wistar rats were made diabetic at 9 weeks of age with a single intravenous injection of streptozotocin 50 mg/kg. The diabetic rats were studied along with age-matched control and insulin-treated rats at 4, 8, 12 and 24 weeks after the induction of diabetes to investigate isolated papillary muscle contraction and the histopathological picture simultaneously. In the isometric contractions, resting and developed tensions were similar. Time to peak tension and time to 1/2 relaxation were prolonged and the peak rate of tension rise and tension fall was depressed. On histological examination of left ventricular walls, diameters of myocytes were similar at all disease durations. Interstitial fibrosis and disarrangement of myocytes after 12 weeks were slightly increased in the diabetic hearts. Mechanical parameters did not worsen in parallel with the duration of diabetes and histological changes, but correlated with the blood glucose level. These data suggest that short-term mechanical defects in the experimental diabetic rat heart result from the metabolic disorder itself, with histopathological changes occurring later.

Diabetes and arterial disease

Macroangiopathy (or atherosclerosis) is a common and chronic complication in diabetic patients. Unlike other diabetic complications, atherosclerosis is not unique to diabetes, confounding analysis of its relationship with the diabetic condition. Evidence of an independent role for diabetes in the development of atherosclerosis remains equivocal. The main determinant of macrovascular disease may be an interaction between diabetes and the aging process. Similarly the question of a relationship between macrovascular disease and good metabolic control remains unanswered. Macroangiopathy in diabetic populations seems to be related to similar predictors and pathological mechanisms operating in the general population. However, after analysis of these common risk factors for macroangiopathy, a diabetes-specific risk remains. Low-density lipoprotein metabolism is markedly disturbed in poorly controlled diabetic patients. This is manifest as a concert of actions which increase formation of foam cells and fatty streaks. The next step in the atherosclerotic process, the formation of fibrous plaques, may be associated with the platelet hyperactivity seen in diabetes. This may promote overshooting of repair mechanisms at the vessel wall. Release of a specific diabetic serum growth factor from the platelets may be responsible for the later stages of fibrous plaque development and the increased atherosclerotic risk in diabetes.

Myocardial metabolism in type 1 diabetic patients without coronary artery disease

Myocardial exchange of metabolic substrates was investigated in eight Type 1 diabetic patients with angiographically normal coronary arteries and seven normal control subjects, after an overnight fast. Simultaneous samples of arterial and coronary sinus blood were collected for analysis of the major metabolic substrates. Myocardial blood flow was measured by the thermodilution technique. Although the Type 1 patients were hyperglycaemic (10.0 +/- 2.0 (+/- SE) mmol I-1) myocardial glucose uptake was lower than in control subjects (27 +/- 6 vs 42 +/- 5 mumol min-1 1.73 m-2, p less than 0.05). The net balance of lactate and pyruvate across the myocardium showed a net release in Type 1 patients (13.4 +/- 2.7 mumol min-1 1.73 m-2 and 1.3 +/- 0.2 mumol min-1 1.73 m-2, respectively) and a net uptake in control subjects (2.2 +/- 0.7 mumol min-1 1.73 m-2 and 3.5 +/- 0.3 mumol min-1 1.73 m-2, both p less than 0.01). Myocardial uptake of ketone bodies was significantly higher in diabetic patients (37.0 +/- 6.3) mumol min-1 1.73 m-2) than in control subjects (10.1 +/- 3.4 mumol min-1 1.73 m-2, p less than 0.01). Non-esterified fatty acid (NEFA) uptake was significantly greater in the diabetic patients than in control subjects (44.1 +/- 7.0) vs 24.1 +/- 5.1 mumol min-1 1.73 m-2, p less than 0.01). Net balance of glucose, lactate, and pyruvate across the myocardium was inversely and significantly related to that of NEFAs and ketone bodies (p less than 0.01). Myocardial carbohydrate uptake is markedly impaired in Type 1 diabetic patients with angiographically intact coronary vessels. Ketones and NEFA represent the major fuel for the diabetic myocardium. Thus, in diabetes, myocardial lactate metabolism may be profoundly altered independently of coronary artery disease.

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.

Diabetic heart and kidney exhibit increased resistance to lipid peroxidation

Alloxan-diabetic rats and age-matched controls were killed after 6 weeks of diabetes; heart and kidneys were removed and assayed for thiobarbituric acid-reactive substances (TBARS), lipid hydroperoxides, lipid phosphorus, total fatty acid composition and glutathione. Tissue homogenates from a second group of diabetic and control rats were incubated in oxygen-saturated buffer with and without the free radical generating system Fe2+/ascorbate (0.1/1.0 mM) and were assayed for lipid peroxidation. Diabetic hearts contained markedly lower levels of TBARS and lipid hydroperoxides (40% and 18%, respectively) than control hearts, whereas differences in TBARS were less pronounced in kidneys (9%). Incubation of homogenates of both organs in the presence or absence of Fe2+/ascorbate for up to 2 h yielded significantly lower levels of TBARS and lipid hydroperoxides with diabetic tissue. Diabetic hearts and kidneys contained higher levels of glutathione (28% and 13% over controls) and both diabetic tissues showed much higher linoleate/arachidonate ratios than did the controls (9.86 vs. 2.56 for heart, 2.01 vs. 0.86 for kidney). We conclude that diabetic tissues develop enhanced defense systems against oxidative stress and we assume tha the lower levels of arachidonate contribute to their resistance to lipid peroxidation as well.

Increase in the activities of plasma pseudocholinesterase dependent on the blood glucose level and its relation to the hypersensitivity to acetylcholine in striated muscles of KK-CAy mice with diabetes

Acetylcholinesterase activity and pseudocholinesterase activity were examined in plasma and in striated muscles (whole heart and diaphragm muscles) of diabetic KK-CAy mice. Both activities of acetylcholinesterase in heart muscle and pseudocholinesterase in plasma were significantly increased in diabetic KK-CAy mice compared to pre-diabetic KK-CAy mice. Both acetylcholinesterase and pseudocholinesterase activities in skeletal muscle were not changed by the diabetic state. The increases in activity of plasma pseudocholinesterase was significantly correlated to the increase in blood glucose level in alloxan-, streptozotocin (STZ)-diabetic ddY mice and diabetic KK-CAy mice. The increase was not correlated to the body weight in non-diabetic female-KK-CAy mice. Furthermore, the activity of heart acetylcholinesterase was significantly correlated with the activity of plasma pseudocholinesterase (r = 0.79, P less than 0.01). The activities of acetylcholinesterases in heart muscles from STZ- and alloxan-diabetic ddY mice also tended to increase. The hypersensitivity of the pulse rate to a low dose (1 mg/kg) of acetylcholine was correlated to the activity of plasma pseudocholinesterase (r = -0.51, P less than 0.05). These results demonstrate that the activities of plasma pseudocholinesterase were increased by the diabetic state being associated with the increasing alteration of cardiac sensitivity to acetylcholine in the whole body.

Abnormal cardiac function in the streptozotocin-diabetic rat. Changes in active and passive properties of the left ventricle

To provide an integrated assessment of changes in systolic and diastolic function in diabetic rats, we measured conscious hemodynamics and performed ex vivo analysis of left ventricular passive-elastic properties. Rats given streptozotocin (STZ) 65 mg/kg i.v. (n = 14) were compared with untreated age-matched controls (n = 15) and rats treated with insulin after administration of STZ (n = 11). After 7 d, diabetic rats exhibited decreases in heart rate and peak developed left ventricular (LV) pressure during aortic occlusion. After 26 d of diabetes there were significant decreases in resting LV systolic pressure, developed pressure, and maximal +dP/dt, whereas LV end-diastolic pressure increased and the time constant of LV relaxation was prolonged. The passive LV pressure-volume relationship was progressively shifted away from the pressure axis, and the overall chamber stiffness constant was decreased. However, "operating chamber stiffness" calculated at end-diastolic pressure was increased at 7 d, and unchanged at 26 d. LV cavity/wall volume and end-diastolic volume were increased after 26 d of diabetes. Myocardial stiffness was unchanged at both time intervals. All of the above abnormalities were reversed by the administration of insulin. We conclude that the hemodynamic and passive-elastic changes that occur in diabetic rats represent an early dilated cardiomyopathy which is reversible with insulin.

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.

Elevated levels of nonesterified fatty acids in the myocardium of alloxan diabetic rats

Myocardial nonesterified fatty acids (NEFA) increase markedly within the first two days after the induction of insulin-dependent diabetes mellitus in rats by intravenous injection of alloxan. After initial variability, NEFA levels in diabetic hearts remain constant at approximately 450 nmol/g tissue (16 nmol/mumol lipid P), which is about three times higher than that in control hearts. Nonesterified linoleic acid is significantly increased in diabetic heart whereas both arachidonic and docosahexaenoic acids are decreased compared to controls.

Altered functional activity and anoxic tolerance in diabetic rat isolated atria

Functional activities of isolated atria from 4-week diabetic rats and their anoxic tolerance and recovery were compared to those of control rats. The present study showed a two-fold increase in maximum developed contraction force (CF), the rate of force development, and the rate of relaxation in isolated atria from diabetic rat heart over that of the control. The rate of the sinoatrial node was lower in the diabetic. However, this lower rate was not responsible for higher CF of the diabetic isolated atria since the twofold difference was still present when both diabetic and control atria were electrically paced at identical rates. Although the high energy phosphate content of the diabetic isolated atria was lower than that of control (50% lower phosphocreatine and 15% lower ATP), diabetic atria exhibited improved short term anoxic tolerance and recovery compared to that of the control. The recovery from long term anoxia, however, was better in control than in diabetic atria, considering the higher original CF in diabetic atria. The present observations are compatible with better ischemic tolerance and higher basal force development observed by some investigators on diabetic isolated heart preparations but not with impaired contractility reported by others. Possible mechanisms responsible for the observed changes are discussed.

Transient atrial fibrillation precipitated by hypoglycemia

Two noninsulin-dependent diabetic patients developed transient atrial fibrillation precipitated by hypoglycemia that reverted to sinus rhythm after administration of IV dextrose. Atrial fibrillation as a complication of hypoglycemia in diabetic patients has been reported in only two patients with insulin-dependent diabetes mellitus.

Myocardial metabolism in insulin-deficient diabetic humans without coronary artery disease

Eleven insulin-dependent diabetes mellitus (IDDM) patients with angiographically normal coronary arteries and a normal hemodynamic response to an echocardiographic-dipyridamole test and 12 normal controls were studied at rest and after atrial pacing simultaneously sampling arterial and coronary sinus blood. In IDDM patients, despite hyperglycemia [10.0 +/- 2.0 (SE) mmol/l], myocardial glucose uptake was slightly lower than in controls. This process was significantly activated in both groups during atrial pacing. The isotopically calculated net flux of lactate across myocardium, in agreement with the net balance value based on unlabeled lactate-pyruvate arteriovenous differences, showed a net uptake in controls (3.5 +/- 0.6 mumol.min-1.1.73 m-2) and a net release in IDDM (12.4 +/- 2.6; P less than 0.01). Atrial pacing stimulated lactate uptake in both groups. Myocardial uptake of ketone bodies was significantly higher in IDDM (37.0 +/- 6.3 mumol.min-1.1.73 m-2) than in controls (10.1 +/- 3.4 mumol.min-1.1.73 m-2; P less than 0.01). Free fatty acid uptake was also significantly greater in IDDM than in controls (44.1 +/- 7.0 vs. 24.1 +/- 5.1 mumol.min-1.1.73 m-2; P less than 0.01). Alanine and branched amino acids were released by diabetic but not by control hearts at rest. The normalization of blood glucose concentrations restored normal patterns of lactate and ketone body kinetics across diabetic myocardium. In conclusion, 1) at rest, myocardial lactate and amino acid uptake is markedly impaired in IDDM without coronary artery disease, and 2) the metabolic abnormalities of the diabetic myocardium are not a primary phenomenon but rather a consequence of hypoinsulinemia and hyperglycemia because insulin administration, resulting in euglycemia, restored normal patterns of cardiac metabolism.

Effects of chronic non-ketotic diabetes and aging on myocardial function and fatty acid oxidation

The effects of aging and chronic non-ketotic diabetes on contractile properties, oxygen consumption, palmitate oxidation and morphology were studied in isolated, perfused working hearts of 2, 9, 12 and 22 month old rats. The heart rate, coronary flow, and oxygen consumption were no different among the 9, 12 and 22 month control and diabetic hearts. Cardiac work was not depressed in control hearts until 22 months of age. Depression of cardiac output due to aging in the control hearts progressed in stages. The superimposition of chronic diabetes in the 9, 12 and 22 month rats did not further depress the cardiac work or cardiac output. [1-14C] palmitate oxidation in the 2 and 9 month control hearts was higher than that of the 12 and 22 month controls. Chronic diabetes did not affect fatty acid oxidation in the 9 and 12 month rats compared to their controls, but was diminished in the 22 month diabetic rat heart. These results suggest that impairments in the contractile properties of the isolated hearts of the chronically diabetic, senescent rats were primarily due to aging.

Endomyocardial biopsy diagnosis of small vessel disease: a clinicopathologic study

We reviewed the clinical history of 191 patients undergoing endomyocardial biopsy and correlated signs and symptoms of heart disease with the presence or absence of small vessel disease. Idiopathic congestive heart failure (78%), arrhythmia (35%), and chest pain (25%) were the most frequent indications for biopsy. Small vessel disease was noted in 61% of the biopsies (67% female, 56% male): 10% severe, 36% moderate, and 15% mild small vessel disease. Patients with hypertension were twice as likely to have small vessel disease than those without hypertension. Of the 27 females with hypertension, 85% had small vessel disease, 67% with either severe or moderate small vessel disease. Small vessel disease was almost twice as frequent in patients with chest pain compared to patients without chest pain. Chest pain was significantly more common in patients with severe small vessel disease than in those with normal small vessels. Of all patients with chest pain, 18% had severe small vessel disease; however, of 20 patients with severe small vessel disease, 45% had chest pain. This analysis suggests that small vessel disease seen in endomyocardial biopsy is more common in women and is related to hypertension. When severe, it is likely to be associated with atypical chest pain.

Myocardial disease in hypertensive-diabetic patients

Experimental and clinical evidence points to the existence of a cardiomyopathy associated with diabetes mellitus that is not due to coronary atherosclerosis. The condition is characterized by distinct clinical presentations and physiologic and biochemical abnormalities. Potential mechanisms for the development of diabetic cardiomyopathy are complex but are probably associated, in part, with hyperglycemia and hyperlipidemia. Primary hypertension is also associated with the development of myocardial abnormalities. Many of these changes are similar to those seen in diabetic cardiomyopathy. It is now clear that the co-existence of hypertension and diabetes mellitus produces a more severe cardiomyopathy than that produced by hypertension or diabetes alone. Potential mechanisms for interaction are numerous. Treatment of hypertension in diabetic patients must be targeted to more specific needs. Antihypertensive drugs should not worsen cardiac risk factors or glucose control and should have favorable effects on left ventricular function. The calcium antagonists and angiotensin-converting enzyme inhibitors have pharmacologic profiles that make them attractive as monotherapy for diabetic patients.

Prevalence and significance of left ventricular filling abnormalities determined by Doppler echocardiography in young type I (insulin-dependent) diabetic patients

In 16 insulin-dependent diabetic patients, 36 +/- 8 years old with no microangiopathy, hypertension or coronary artery disease, and 16 healthy control subjects matched for sex, age and body surface area, the following parameters were obtained by Doppler-echocardiography: (1) end-diastolic left ventricular thickness and radius; (2) aortic pulse wave velocity; (3) mitral flow with measurement of early and late (atrial) peak velocities (E and A), pressure half-time and the velocity time integrals of the entire mitral curve and of the atrial wave; and (4) isovolumic relaxation time (i.e., the time between aortic closure and the mitral opening signals recorded simultaneously by continuous-wave Doppler). Heart rate and systolic blood pressure were not different in the 2 groups. Aortic pulse wave velocity and the wall thickness to radius ratio were significantly increased in the diabetic patients compared to the controls. E was significantly reduced whereas A/E, pressure half-time, the atrial contribution to the left ventricular filling (i.e., the ratio of the atrial velocity time integral to the mitral velocity time integral) and the isovolumic relaxation time were significantly increased in the diabetic group versus the control subjects. Lastly, 11 of 16 diabetic patients (69%) had at least 2 of the following abnormalities: A/E greater than 0.71, an atrial contribution to the left ventricular filling greater than 0.25, a pressure half-time greater than 50 ms and an isovolumic relaxation time greater than 88 ms. No correlations were found between the wall thickness to radius ratio, aortic pulse wave velocity and the filling indexes.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Ventricular vulnerability in diabetes and myocardial norepinephrine release

Previously the authors have observed a reduction of the ventricular fibrillation threshold (VFT) in a mild diabetic model. This investigation examines the role of more severe hyperglycemia in altering the ventricular fibrillation threshold and how the sympathetic nervous system modulates the response. Alloxan diabetes was induced in eight male mongrel dogs 3-5 years of age (Group 2), for comparison with matched controls (Group 1). Hemoglobin A1c rose from 2.9 +/- .4-7.8 +/- .3% and body weight was maintained with daily insulin. After 1 year, anesthesia was induced with chloralose and an electrode catheter placed at the right ventricular apex. VFT was 41.7 +/- 1.8 ma in Group 1 and 27.8 +/- 2.1 ma in the diabetics of Group 2 (p less than .001). There was significantly greater decline of VFT in response to epinephrine infusion in Group 2. The threshold in diabetics rose to normal levels after infusion of the beta-blocking agent, esmolol. Subsequently, the response of the cardiac sympathetic system was assessed during ventricular pacing at 200 beats/minute. Serial paired blood samples were taken from catheters in the aorta and coronary sinus for catecholamine assay by HPLC. Both groups had similar coronary blood flow responses by the thermal method, as well as changes in arterial pressure. While no change occurred in Group 1, a progressive rise of norepinephrine (NE) concentration was observed in coronary venous effluent of Group 2 (p less than .01). The basal arterial-coronary sinus difference was-123 +/- 52 pg/ml, which rose during pacing in Group 2 to a peak of -376 +/- 9.3 pg/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

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?

Alterations in atrial reactivity in a strain of spontaneously diabetic rats

1. The present study examined the reactivity of atria from control and spontaneously diabetic rats to various adrenoceptor agonists and to adenosine. 2. Isoprenaline (1.5 nM-1500 nM) produced concentration-dependent increases in inotropy which were unchanged in diabetic atria. However, the sensitivity to isoprenaline-induced changes in chronotropy was reduced in diabetic preparations. 3. In the presence of propranolol (2 microM), phenylephrine (0.2 microM-100 microM) produced concentration-dependent increases in both inotropy and chronotropy; however, atria from diabetic rats exhibited a much greater maximal response. The diabetic state did not alter the sensitivity to phenylephrine. 4. Adenosine (0.15 microM-300 microM) produced concentration-dependent decreases in both inotropy and chronotropy which were unchanged in diabetic atria. 5. Radioligand binding studies revealed that both alpha 1- and beta-adrenoceptor populations were substantially reduced in atria from diabetic rats. However, there was no change in receptor affinity for either adrenoceptor. 6. These results show that diabetes leads to an alteration in atrial reactivity to adrenoceptor stimulation. Future studies examining steps following hormone-receptor coupling are required in order to characterize this defect.

Plasma membrane-specific deficiency in cardiac beta-adrenergic receptor in streptozocin-diabetic rats

Cell surface [3H]CGP 12177 binding sites in 10-wk streptozocin-diabetic rats decreased by 41% (P less than 0.01) compared with that in the control rats. In contrast, there was no difference in the total cell receptor concentration between the control and the diabetic rats, which was measured by hydrophobic antagonist [125I]-iodocyanopindolol binding. Forty-eight-hour in vivo insulin treatment significantly (P less than 0.05) increased cell surface beta-adrenergic receptor concentration by 37% above that in diabetic rats without any change in total receptor concentration in the cells. However in vitro treatment of 8 nM insulin, 33 mM glucose, or 10 mM 3-hydroxybutyrate for 2 h showed no effect on [3H]CGP 12177 binding. In contrast, 10 microM isoproterenol-dependent decrease and the recovery of cell surface receptors after the removal of the agonist were significantly (P less than 0.01) impaired in diabetic rats compared with those of control rats. These results indicate that only cell surface beta-adrenergic receptors decrease in diabetic rats, which may be associated with abnormalities in the receptor distribution. The decrease in cell surface receptor number closely associates with the diabetic state and is reversed by the short-term insulin treatment.

Noninvasive assessment of cardiomyopathy in normotensive diabetic patients between 20 and 50 years old

PURPOSE

To further the understanding of diabetic heart disease, we tested the hypothesis that an asymptomatic group of normotensive diabetic patients between 20 and 50 years old had a restrictive cardiomyopathy independent of clinically significant coronary artery disease.

PATIENTS AND METHODS

Quantitative two-dimensional echocardiography and stress myocardial perfusion scintigraphy were performed to detect and characterize the cardiac abnormalities in this study group comprising 88 patients with rigorously classified diabetes and 65 volunteer control subjects.

RESULTS

Diabetic patients were shown to have a mildly reduced left ventricular end-diastolic volume index: 50.1 +/- 8.2 and 52.1 +/- 14.7 mL/m2 for patients with type I and type II diabetes, respectively, versus 58.9 +/- 11.7 mL/m2 for control subjects. The left ventricular diastolic filling was also impaired in diabetic patients as reflected by a lower atrial emptying index: 0.73 +/- 0.24 and 0.76 +/- 0.3 for type I and type II diabetics, respectively, compared with 1.14 +/- 0.24 for control subjects. Exercise tolerance was normal in subjects with type I diabetes and slightly reduced in subjects with type II diabetes. Only one patient developed regional ischemia on thallium exercise testing.

CONCLUSION

Using a comprehensive, noninvasive approach, we have shown that asymptomatic normotensive patients with type I or type II diabetes who were between 20 and 50 years old had a restrictive cardiomyopathy characterized by mildly reduced left ventricular end-diastolic volume and altered left ventricular compliance independent of critical coronary artery disease.

Effect of age and methacholine on the rate and coronary flow of isolated hearts of diabetic rats

1. Isolated hearts perfused by the method of Langendorff from 6, 12 and 24 week streptozotocin (STZ) diabetic rats displayed a significant bradycardia following 60 min equilibration. The rate of hearts from 12-week diabetic rats (164 +/- 17) displayed the greatest bradycardia compared to age-matched controls (268 +/- 15; P less than 0.001), and diabetics treated with insulin (232 +/- 17; P less than 0.01), but by 52 weeks the heart rate of the 3 groups was similar. With advancing age the effect of STZ diabetes on the rate of rat isolated perfused hearts remained unchanged but the rate of the control and diabetic + insulin groups declined. 2. Hearts from 6-52 week STZ-treated rats were found to be more sensitive to the negative chronotropic effect of methacholine, the greatest difference occurring in hearts from the 12 week animals. Atropine (10(-7) M) did not affect the resting heart rate of age-matched controls or diabetics but blocked methacholine (2.6 x 10(-6) M)-induced bradycardia in both, suggesting that the site of action of diabetic bradycardia is not the muscarinic receptors. 3. At the end of equilibration there was a significant decrease in coronary flow in hearts from 12 week diabetic animals. In spontaneously beating diabetic rat hearts administration of methacholine (2.6 x 10(-6) M) produced a significantly greater decrease in coronary flow in the 12, 24 and 52 week diabetic hearts. When electrically paced (5 Hz) however, there was no difference in response to methacholine between the three groups except at 52 weeks between the age-matched control and diabetic groups. This suggests that the more pronounced reduction induced by methacholine on the coronary flow of diabetic hearts is secondary to its negative chronotropic effect. 4. In general, hearts from diabetic animals treated with insulin respond similarly to their agematched controls in the presence and absence of methacholine.

The effect of diabetes mellitus on prognosis and serial left ventricular function after acute myocardial infarction: contribution of both coronary disease and diastolic left ventricular dysfunction to the adverse prognosis. The MILIS Study Group

Patients with diabetes mellitus experience a more adverse outcome after acute myocardial infarction compared with nondiabetic patients, although the mechanisms responsible for these findings are not clear. From the Multicenter Investigation of the Limitation of Infarct Size (MILIS) study, the course of acute infarction in 85 diabetic patients was compared with that in 415 nondiabetic patients, all of whom had serial assessments of left ventricular function. The diabetic patients experienced a more complicated in-hospital and postdischarge course than did the nondiabetic patients, including a higher incidence of postinfarction angina, infarct extension, heart failure and death, despite the development of a smaller infarct size and similar levels of left ventricular ejection fraction. Although diabetic patients had a worse profile of cardiovascular risk factors at the time of the index infarction, the increased incidence of adverse outcomes among them persisted despite adjustment for these baseline imbalances. Diabetic women had a poor baseline risk profile compared with the other groups categorized by gender and diabetic status, and experienced an almost twofold increase in cardiac mortality despite development of the smallest infarct size during the index event. The duration of diabetes and the use of insulin at the time of the index infarction were associated with a better in-hospital mortality rate, but the duration of diabetes did not exert a major influence on the outcome of the diabetic patients. The factors responsible for the increased incidence of adverse outcomes among diabetic patients may be related to an acceleration of the atherosclerotic process, diastolic left ventricular dysfunction associated with diabetic cardiomyopathy or other unidentified unfavorable processes.

Endomyocardial biopsy pathology in insulin-dependent diabetic patients with abnormal ventricular function

We have previously shown impaired ventricular function in asymptomatic middle-aged type 1 (insulin-dependent) diabetic patients who had no evidence of coronary artery disease. The diabetic patients had normal coronary angiograms but reduced ventricular ejection fraction on exercise. To examine the possible contribution of small vessel disease to this functional abnormality, we compared endomyocardial biopsies from seven symptom-free type 1 diabetic patients with biopsies from seven age- and sex-matched non-diabetic subjects. Interstitial fibrosis was present in three diabetic patients, arteriolar hyalinization in three patients and arteriolar thickening was observed in five patients. Morphometry performed on electron micrographs showed no significant difference in the thickness of the capillary basal lamina between diabetics and controls. While the functional significance of the abnormalities on light microscopy is unclear, our findings indicate that the abnormality of cardiac function described in diabetes is not associated with thickening of the myocardial capillary basal lamina.

[Stress testing of long-term type I diabetic patients with radionuclide ventriculography]

Left ventricular function was assessed by means of radionuclide ventriculography in 42 patients with long-standing (13 +/- 5 yrs) insulin-dependent diabetes mellitus and in eleven healthy age matched control subjects. Only diabetics were included in the study without diabetes related cardiac risk factors such as hypertension and CAD in order to evaluate diabetes specific changes of cardiac function. No differences were seen between diabetics and controls concerning heart rate and functional parameters of left ventricle in systole and diastole. The rapid filling period was not prolonged. According to our radionuclide data there is no evidence of diabetes related impairment of ventricular function in young patients with long-standing type-1-diabetes mellitus.

Cardiac disease in diabetes

The current approach to cardiac disease recognizes that the cardiovascular problems of diabetic patients have both a coronary artery atherosclerotic component and an independent myocardial component. The presence of the myocardial component has become more apparent in recent years, and a full understanding of the balance between the two components is necessary for proper treatment of the cardiac problems of patients with diabetes.

Isoproterenol-induced ultrastructural alterations in hearts of alloxan-diabetic rabbits

1. The effects of isoproterenol (ISO) on the ultrastructure of hearts from 10-week alloxan diabetic rabbits were examined. 2. Following alloxan injection, all rabbits developed severe hyperglycemia, hyperlipidemia and hypoinsulinemia. 3. Injection of ISO induced marked alterations in both control and diabetic rabbit hearts including accumulation of lipid and swelling of sarcoplasmic reticulum. 4. Myofibrils in both groups of animals were dispersed and appeared as a homogeneous mass with poorly defined Z-bands. 5. The most marked effect of ISO treatment in both groups of animals was damage to mitochondria. Mitochondria were extensively damaged and showed partial or complete disruption of their cristae network. 6. Glycogen granules were few in number or not detectable in both groups of animals. 7. The diabetic animals treated with ISO showed greater clumping and margination of nuclear chromatin, fewer intact mitochondria and a greater number of amorphous dense bodies in and around the mitochondria. 8. The presence of greater sarcolemmal damage in diabetic animals was inferred from the significantly greater accumulation of calcium and decreased magnesium in the myocardium.