Left ventricular systolic function in middle-aged patients with diabetes mellitus

Clinical Update: Cardiovascular Disease in Diabetes Mellitus: Atherosclerotic Cardiovascular Disease and Heart Failure in Type 2 Diabetes Mellitus - Mechanisms, Management, and Clinical Considerations

Cardiovascular disease remains the principal cause of death and disability among patients with diabetes mellitus. Diabetes mellitus exacerbates mechanisms underlying atherosclerosis and heart failure. Unfortunately, these mechanisms are not adequately modulated by therapeutic strategies focusing solely on optimal glycemic control with currently available drugs or approaches. In the setting of multifactorial risk reduction with statins and other lipid-lowering agents, antihypertensive therapies, and antihyperglycemic treatment strategies, cardiovascular complication rates are falling, yet remain higher for patients with diabetes mellitus than for those without. This review considers the mechanisms, history, controversies, new pharmacological agents, and recent evidence for current guidelines for cardiovascular management in the patient with diabetes mellitus to support evidence-based care in the patient with diabetes mellitus and heart disease outside of the acute care setting.

Sudden cardiac death and diabetes mellitus

Sudden cardiac death (SCD) affects a significant percentage of diabetic patients. SCD in these patients can be due to several factors, such as diastolic dysfunction, heart failure, altered platelet function, inflammation, sympathetic nervous stimulation and other factors. In the present review, we discuss the association between diabetes mellitus and SCD.

Hyperglycemia has a greater impact on left ventricle function in South Asians than in Europeans

OBJECTIVE Diabetes is associated with left ventricular (LV) diastolic and systolic dysfunction. South Asians may be at particular risk of developing LV dysfunction owing to a high prevalence of diabetes. We investigated the role of diabetes and hyperglycemia in LV dysfunction in a community-based cohort of older South Asians and white Europeans. RESEARCH DESIGN AND METHODS Conventional and Doppler echocardiography was performed in 999 participants (542 Europeans and 457 South Asians aged 58-86 years) in a population-based study. Anthropometry, fasting bloods, coronary artery calcification scoring, blood pressure, and renal function were measured. RESULTS Diabetes and hyperglycemia across the spectrum of HbA1c had a greater adverse effect on LV function in South Asians than Europeans (N-terminal-probrain natriuretic peptide β ± SE 0.09 ± 0.04, P = 0.01, vs. -0.04 ± 0.05, P = 0.4, P for HbA1c/ethnicity interaction 0.02), diastolic function (E/e' 0.69 ± 0.12, P < 0.0001, vs. 0.09 ± 0.2, P = 0.6, P for interaction 0.005), and systolic function (s' -0.11 ± 0.06, P = 0.04, vs. 0.14 ± 0.09, P = 0.1, P for interaction 0.2). Multivariable adjustment for hypertension, microvascular disease, LV mass, coronary disease, and dyslipidemia only partially accounted for the ethnic differences. Adverse LV function in diabetic South Asians could not be accounted for by poorer glycemic control or longer diabetes duration. CONCLUSIONS Diabetes and hyperglycemia have a greater adverse effect on LV function in South Asians than Europeans, incompletely explained by adverse risk factors. South Asians may require earlier and more aggressive treatment of their cardiometabolic risk factors to reduce risks of LV dysfunction.

Diabetic cardiomyopathy: understanding the molecular and cellular basis to progress in diagnosis and treatment

Diabetes mellitus is an important and prevalent risk factor for congestive heart failure. Diabetic cardiomyopathy has been defined as ventricular dysfunction that occurs in diabetic patients independent of a recognized cause such as coronary artery disease or hypertension. The disease course consists of a hidden subclinical period, during which cellular structural insults and abnormalities lead initially to diastolic dysfunction, later to systolic dysfunction, and eventually to heart failure. Left ventricular hypertrophy, metabolic abnormalities, extracellular matrix changes, small vessel disease, cardiac autonomic neuropathy, insulin resistance, oxidative stress, and apoptosis are the most important contributors to diabetic cardiomyopathy onset and progression. Hyperglycemia is a major etiological factor in the development of diabetic cardiomyopathy. It increases the levels of free fatty acids and growth factors and causes abnormalities in substrate supply and utilization, calcium homeostasis, and lipid metabolism. Furthermore, it promotes excessive production and release of reactive oxygen species, which induces oxidative stress leading to abnormal gene expression, faulty signal transduction, and cardiomyocytes apoptosis. Stimulation of connective tissue growth factor, fibrosis, and the formation of advanced glycation end-products increase the stiffness of the diabetic hearts. Despite all the current information on diabetic cardiomyopathy, translational research is still scarce due to limited human myocardial tissue and most of our knowledge is extrapolated from animals. This paper aims to elucidate some of the molecular and cellular pathophysiologic mechanisms, structural changes, and therapeutic strategies that may help struggle against diabetic cardiomyopathy.

Transient ischemic dilation in SPECT myocardial perfusion imaging for prediction of severe coronary artery disease in diabetic patients

BACKGROUND

Transient ischemic dilation (TID) of the left ventricle during stress myocardial perfusion SPECT (MPS) has been shown to be a useful marker of severe coronary artery disease (CAD). However, investigations in diabetic patients with available coronary angiographic data are still limited. We evaluated the incremental diagnostic value of TID in identifying the presence of angiographically severe CAD in diabetic patients.

METHODS AND RESULTS

TID ratio values were automatically derived from rest-stress MPS in 242 diabetic patients with available coronary angiography data. A cutoff of ≥1.19 was considered to represent TID. Severe CAD (≥70% stenosis in the proximal left anterior descending artery or the left main artery, or ≥90% stenosis in two or three vessels) was identified in 69 (29%) patients. At multivariate analysis, the best independent predictors of severe CAD were summed stress score and TID (both P < .001). At incremental analysis, the addition of TID improved the power of a model including clinical data and summed stress score, increasing the global χ(2) value from 14.3 to 28.2 (P < .01). The best cutoff of summed stress score for identifying patients with severe CAD was ≥8. When the TID ratio was considered in patients with summed stress score between 3 and 7, the sensitivity for diagnosing severe CAD significantly improved from 71% to 77% (P < .05). In the overall study population, the net reclassification improvement by adding TID to a model including clinical data and summed stress score in the prediction of severe CAD was 0.40 (P < .005).

CONCLUSIONS

TID ratios obtained from rest-stress MPS provide incremental diagnostic information to standard perfusion analysis for the identification of severe and extensive CAD in diabetic patients.

Diabetic cardiovascular disease: getting to the heart of the matter

Diabetes is a major risk factor for heart disease, and heart disease is responsible for substantial morbidity and mortality among people living with diabetes. The diabetic metabolic milieu predisposes to aggressive obstructive coronary artery disease that causes heart attacks, heart failure, and death. Furthermore, diabetes can be associated with heart failure, independent of underlying coronary artery disease, hypertension, or valve abnormalities. The pathogenesis of the vascular and myocardial complications of diabetes is, as yet, incompletely understood. Although a number of medical and surgical approaches can improve outcomes in diabetic patients with cardiovascular disease, much remains to be learned in order to optimize approaches to these critical complications.

Diabetes reduces left ventricular ejection fraction--irrespective of presence and extent of coronary artery disease

BACKGROUND

It is not clear whether diabetes reduces systolic left ventricular function (left ventricular ejection fraction, LVEF) irrespective of coronary artery disease (CAD). The aim of this study was to compare the LVEF between diabetic and non-diabetic patients with respect to the extent of CAD.

METHODS AND RESULTS

Consecutive patients undergoing stress myocardial perfusion SPECT (MPS) were evaluated. MPS was interpreted using a 20-segment model with a five-point scale to define summed stress score (SSS), summed rest score, and summed difference score. LVEF was measured by gated SPECT and then compared with respect to diabetic status and SSS categories. Of 2635 patients, data of 2400 was available. Of these, 24% were diabetic, mean age was 64±11y, and 31% were female. Diabetics had a significantly lower LVEF compared with non-diabetics regardless of the extent of CAD: 53±13 and 55±13% respectively (P=0.001). Diabetics and non-diabetics did not differ significantly in the distribution of SSS categories. Diabetes was an independent predictor of decreased LVEF (odds ratio 1.6, 95% confidence interval 1.2-2.0; P<0.001).

CONCLUSION

Diabetics had a lower LVEF than non-diabetics. This difference could be demonstrated regardless of CAD extent and might in part explain their generally worse cardiac survival compared with non-diabetics on an epidemiological level. In addition, this finding points to discussed mechanisms other than CAD lowering LVEF in diabetics.

Relationship between insulin resistance and left ventricular diastolic dysfunction in patients with impaired glucose tolerance and type 2 diabetes

AIM

The aim of this study was to explore the relationship between insulin resistance (IR) and the left ventricular diastolic function in patients with type 2 diabetes and subjects with impaired glucose tolerance (IGT).

METHODS

The study included 119 subjects who underwent oral glucose tolerance test (OGTT). IR was assessed using Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) and Quantitative Insulin Sensitivity Check Index (QUICKI). Left ventricular diastolic function was assessed using trans-thoracic Doppler echocardiography.

RESULTS

Based on the OGTT results, 29 subjects had normal glucose tolerance (NGT), 20 subjects had impaired glucose tolerance (IGT), and 70 patients had type 2 diabetes. There were significant differences among the patients in groups with NGT, IGT and diabetes regarding HOMA-IR (4.20 +/- 1.20 vs. 6.45 +/- 3.83 vs. 8.70 +/- 6.26; P < 0.001) and QUICKI (0.54 +/- 0.11 vs. 0.49 +/- 0.08 vs. 0.47 +/- 0.08; P < 0.001). In subjects with NGT, IGT and patients with diabetes, the pulsed Doppler transmitral variables were: E-wave (0.72 +/- 0.16 cm/s vs. 0.62 +/- 0.13 cm/s vs. 0.58 +/- 0.17 cm/s; P < 0.001), A-wave (0.61 +/- 0.13 cm/s vs. 0.62 +/- 0.11 cm/s vs. 0.71+/- 0.14 cm/s; P = 0.006) and E/A ratio (1.22 +/- 0.33 vs. 1.02 +/- 0.24 vs. 0.85 +/- 0.26; p < 0.001). The proportion of subjects with an E/A ratio <1 was 27.6% in the group with NGT, 55% in the group with IGT and 75.7% in the group with diabetes (P < 0.001). The E/A ratio correlated with HOMA-IR (r = -0.30, p = 0.001) and QUICKI (r = 0.37, p < 0.0001). Multiple linear regression model showed that IR (assessed by QUICKI) was an independent correlate of diastolic dysfunction (P = 0.034).

CONCLUSIONS

In subjects with impaired glucose tolerance and patients with type 2 diabetes, insulin resistance is associated with impaired diastolic function of the left ventricle.

The emerging role of echocardiography in the screening of patients at risk of heart failure

A large number of patients without symptoms of heart failure (HF) have asymptomatic left ventricular (LV) dysfunction owing to the compensatory mechanisms acting through the autonomic nervous system and neurohormones. In the setting of screening for prevention, one must identify the subgroup of these patients at high risk for symptomatic HF to establish appropriate therapy. As a first step to identify the subgroup of patients at high risk, clinical screening scores and natriuretic peptide measurements are used. Second, the definite diagnosis of asymptomatic LV dysfunction must be confirmed with echocardiography, occasionally with the help of new technologic developments to establish prompt, appropriate treatment to prevent disease progression. Therefore, the screening role of echocardiography is the early identification of patients with structural cardiopathy who are at risk of developing symptomatic HF and detection of those without LV dysfunction (diabetic and hypertensive) whose condition is prone to advance rapidly to structural cardiopathy or to symptomatic HF.

Activation of PPARgamma enhances myocardial glucose oxidation and improves contractile function in isolated working hearts of ZDF rats

It is suggested that insulin resistance and metabolic maladaptation of the heart are causes of contractile dysfunction. We tested the hypothesis whether systemic PPARgamma activation, by changing the metabolic profile in a model of insulin resistance and type 2 diabetes (the ZDF rat) in vivo, improves contractile function of the heart in vitro. Male Zucker diabetic fatty (ZDF) and Zucker lean (ZL) rats, at 53-56 days of age, were treated with either GI-262570 (a nonthiazolidinedione PPARgamma agonist; A) or vehicle (V) for 1 wk. Agonist treatment resulted in correction of hyperglycemia and dyslipidemia, as well as in reduced hyperinsulinemia. The accumulation of triacylglycerols in the myocardium, characteristic of the ZDF rat, disappeared with treatment. Cardiac power and rates of glucose oxidation in the isolated working heart were significantly reduced in ZDF-V rats, but both parameters increased to nondiabetic levels with agonist treatment. In ZDF-V hearts, transcript levels of PPARalpha-regulated genes and of myosin heavy chain-beta were upregulated, whereas GLUT4 was downregulated compared with ZL. Agonist treatment of ZDF rats reduced PPARalpha-regulated genes and increased transcripts of GLUT4 and GLUT1. In conclusion, by changing the metabolic profile, reducing myocardial lipid accumulation, and promoting the downregulation of PPARalpha-regulated genes, PPARgamma activation leads to an increased capacity of the myocardium to oxidize glucose and to a tighter coupling of oxidative metabolism and contraction in the setting of insulin resistance and type 2 diabetes.

Left ventricular function in patients with type 2 diabetes mellitus

This study showed that the mean left ventricular ejection fraction, end-diastolic volume, end-systolic volume, and muscle mass are comparable in patients with type 2 diabetes mellitus to gender-matched patients who do not have diabetes mellitus, but abnormal ejection fraction is more common in men, although not in women, with diabetes mellitus than without. The ejection fraction was higher and the volumes and muscle mass were lower in women than men in the presence or absence of diabetes mellitus.

Cross-linking of glycated collagen in the pathogenesis of arterial and myocardial stiffening of aging and diabetes

The normal aging process is often accompanied by arterial wall stiffening and by a decrease in myocardial compliance. These processes contribute to isolated systolic hypertension and diastolic heart failure, which lead to substantial morbidity and mortality among older individuals. Patients with diabetes manifest arterial stiffening and diastolic dysfunction at a younger age. This leads to the concept that the mechanism that underlies changes in vascular mechanical properties during aging is accelerated in diabetes. The Maillard reaction or advanced glycation of proteins occurs slowly in vivo with normal aging and at an accelerated rate in diabetes. Advanced glycation end-products (AGEs) that form during the Maillard reaction are implicated in the complications of aging and diabetes. The formation of AGEs on vascular wall and myocardial collagen causes cross-linking of collagen molecules to each other. This leads to the loss of collagen elasticity, and subsequently a reduction in arterial and myocardial compliance. Aminoguanidine, an inhibitor of AGE formation, is effective in slowing or preventing arterial stiffening and myocardial diastolic dysfunction in aging and diabetic animals. In aged and diabetic animals, agents that can chemically break pre-existing cross-linking of collagen molecules are capable of reverting indices of vascular and myocardial compliance to levels seen in younger or non-diabetic animals. These studies suggest that collagen cross-linking is a major mechanism that governs aging and diabetes-associated loss of vascular and cardiac compliance. The development of AGEs cross-link breakers may have important role for future therapy of isolated systolic hypertension and diastolic heart failure in these conditions.

Cardiomyopathy and heart failure in diabetes

Patients with insulin resistance or type 2 diabetes have a particularly high risk for heart failure and a poor prognosis once they develop heart failure. The choice of drugs for the management of heart failure in these patients should be directed at changing the natural history of the disease. The various drugs available for the treatment of heart failure, including ACE inhibitors and beta-adrenergic blockers, are known to be beneficial and should be given as first-line agents. Aggressive risk-factor modification and tight blood pressure and glycemic control are crucial. Much work is needed to establish the safety and efficacy of various oral antidiabetic agents, especially the TZDs, for which the theoretic benefits are substantial and overall morbidity and mortality impact remain ill-defined.

Diabetes mellitus and coronary heart disease

Diabetes mellitus, especially type 2 diabetes, is a growing concern in America. Longitudinal trends show that obesity is more prevalent than in the past, and the incidence of type 2 diabetes is also increasing. Type 2 diabetes typically doubles the CHD risk in men and triples the risk in women. Intervening to control lipid levels and blood pressure has been shown to be especially helpful in preventing CHD, but the impact of better glycemic control on CHD risk is less convincing, especially in clinical trials. Revascularization studies in diabetics show that coronary bypass surgery is related to better outcomes than angioplasty procedures.

Serum HbA1c levels and exercise capacity in diabetic patients

It is well known that cardiovascular morbidity and mortality are high in diabetic patients. Cardiac involvement is silent and early and these diabetic patients generally complain of chronic fatigue. This study was designed to evaluate the relation between glycemic control and exercise capacity in 330 diabetic patients who have no cardiac symptoms by sustaining dynamic exercise. After a cardiac examination, patients with coronary heart disease, ECG abnormalities, cardiac failure, valvular disease, cerebrovascular disease, peripheral artery disease, anaemia and peripheral neuropathy were excluded. Plasma HbA1c and lipid levels were obtained and a symptom limited exercise test based on "Bruce Protocol" was performed on all patients. Plasma HbA1c levels were significantly increased in smokers and in hypercholesterolemic patients (p<0.001, p=0.006). A moderate correlation between exercise capacity and HbA1c levels, and a weak correlation between duration of diabetes, age, sex, hypertension and plasma lipids were obtained. Multivariant regression analys is revealed that only HbA1c and hypercholesterolemia affected exercise capacity independently (r=-0.54 r=-0.30). In conclusion, poor glycemic control in diabetic patients causes earlier cellular involvement. Because of the high affinity of HbA1c to oxygen, the energy metabolism of the cell is affected, with a clinical correlation between chronic fatigue and worsening exercise capacity.

Left ventricular systolic and diastolic functional abnormalities in asymptomatic patients with non-insulin-dependent diabetes mellitus

The aim of this study was to evaluate the relations between left ventricular (LV) functional abnormalities, microangiopathy, and autonomic dysfunction in patients with non-insulin-dependent diabetes mellitus (NIDDM). We studied 66 normotensive patients with NIDDM of > or =4 years' duration (age, 51 +/- 4.5 years; 35 men) and no clinical evidence of cardiac disease. Twenty-one healthy subjects matched for age and sex served as a control group. Echocardiography and Doppler studies were performed to assess LV systolic and diastolic function. Microangiopathy was assessed by fundus examination. Autonomic function was assessed by standing blood pressure and heart rate response to Valsalva maneuver. Patients with NIDDM had a lower ejection fraction (58% +/- 11% versus 66% +/- 4%, P <.0001), E-F deceleration slope (382 +/- 75 versus 427 +/- 31 cm/s(2), P <.05), and E velocity (55 +/- 11 vs. 58 +/- 6 cm/s, P =.02) of the mitral diastolic flow, compared with control subjects, respectively. Patients with ejection fraction <50% had a higher prevalence of retinopathy (65% versus 29%, P <.005), abnormal blood pressure response to standing (53% versus 8%, P <.0005), and proteinuria (65% versus 27%, P =.006). An inverse correlation was found between the duration of diabetes and both the ejection fraction (r = -0.53, P <.05) and E/A ratio (r = -0.4, P <.005). E/A ratio <1 was associated with a higher prevalence of retinopathy (49% versus 20%, P =.01) and abnormal blood pressure response to standing (29% versus 4%, P <.005). Patients with NIDDM and no symptoms of cardiovascular disease have a reduced LV systolic and diastolic function as compared with healthy subjects. LV systolic and diastolic abnormalities are correlated with the duration of diabetes and with other diabetic microangiopathies such as diabetic retinopathy and neuropathy.

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.

Impact of 1 wk of diabetes on the regulation of myocardial carbohydrate and fatty acid oxidation

The aim of this study was to investigate the effect of increasing exogenous palmitate concentration on carbohydrate and palmitate oxidation in hearts from control and 1-wk diabetic rats. Hearts were perfused with glucose, [3-(13)C]lactate, and [U-(13)C]palmitate. Substrate oxidation rates were determined by combining (13)C-NMR glutamate isotopomer analysis of tissue extracts with measurements of oxygen consumption. Carbohydrate oxidation was markedly depressed after diabetes in the presence of low (0.1 mM) but not high (1.0 mM) palmitate concentration. Increasing exogenous palmitate concentration 10-fold resulted in a 7-fold increase in the contribution of palmitate to energy production in controls but only a 30% increase in the diabetic group. Consequently, at 0.1 mM palmitate, the rate of fatty acid oxidation was higher in the diabetic group than in controls; however, at 1.0 mM fatty acid oxidation, it was significantly depressed. Therefore, after 1 wk of diabetes, the major differences in carbohydrate and fatty acid metabolism occur primarily at low rather than high exogenous palmitate concentration.

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.