Cardiovascular status in young patients with insulin-dependent diabetes mellitus

Cardiovascular Risk Reduction in High-Risk Pediatric Patients: A Scientific Statement From the American Heart Association

This scientific statement presents considerations for clinical management regarding the assessment and risk reduction of select pediatric populations at high risk for premature cardiovascular disease, including acquired arteriosclerosis or atherosclerosis. For each topic, the evidence for accelerated acquired coronary artery disease and stroke in childhood and adolescence and the evidence for benefit of interventions in youth will be reviewed. Children and adolescents may be at higher risk for cardiovascular disease because of significant atherosclerotic or arteriosclerotic risk factors, high-risk conditions that promote atherosclerosis, or coronary artery or other cardiac or vascular abnormalities that make the individual more vulnerable to the adverse effects of traditional cardiovascular risk factors. Existing scientific statements and guidelines will be referenced when applicable, and suggestions for risk identification and reduction specific to each setting will be described. This statement is directed toward pediatric cardiologists, primary care providers, and subspecialists who provide clinical care for these young patients. The focus will be on management and justification for management, minimizing information on pathophysiology and epidemiology.

Of mice and men: models and mechanisms of diabetic cardiomyopathy

Diabetes mellitus increases the risk of heart failure independent of co-existing hypertension and coronary artery disease. Although several molecular mechanisms for the development of diabetic cardiomyopathy have been identified, they are incompletely understood. The pathomechanisms are multifactorial and as a consequence, no causative treatment exists at this time to modulate or reverse the molecular changes contributing to accelerated cardiac dysfunction in diabetic patients. Numerous animal models have been generated, which serve as powerful tools to study the impact of type 1 and type 2 diabetes on the heart. Despite specific limitations of the models generated, they mimic various perturbations observed in the diabetic myocardium and continue to provide important mechanistic insight into the pathogenesis underlying diabetic cardiomyopathy. This article reviews recent studies in both diabetic patients and in these animal models, and discusses novel hypotheses to delineate the increased incidence of heart failure in diabetic patients.

Early changes in cardiovascular structure and function in adolescents with type 1 diabetes

Background

Children with type 1 diabetes (T1D) are at higher risk of early adult-onset cardiovascular disease. We assessed cardiovascular structure and function in adolescents with T1D compared with healthy controls and the relationships between peripheral vascular function and myocardial parameters.

Methods and results

199 T1D [14.4 ± 1.6 years, diabetes duration 6.2 (2.0–12.8) years] and 178 controls (14.4 ± 2.1 years) completed endothelial function by flow mediated vasodilatation (FMD), arterial stiffness using pulse wave velocity (PWV) along with M-mode, pulse wave and tissue Doppler, and myocardial deformation echocardiographic imaging. Systolic (113 ± 10 vs. 110 ± 9 mmHg; p = 0.0005) and diastolic (62 ± 7 vs. 58 ± 7 mmHg; p < 0.0001) blood pressures, carotid femoral PWV and endothelial dysfunction measurements were increased in T1D compared with controls. Systolic and diastolic left ventricular dimensions and function by M-mode and pulse wave Doppler assessment were not significantly different. Mitral valve lateral e’ (17.6 ± 2.6 vs. 18.6 ± 2.6 cm/s; p < 0.001) and a’ (5.4 ± 1.1 vs. 5.9 ± 1.1 cm/s; p < 0.001) myocardial velocities were decreased and E/e’ (7.3 ± 1.2 vs. 6.7 ± 1.3; p = 0.0003) increased in T1D. Left ventricular mid circumferential strain (−20.4 ± 2.3 vs. −19.5 ± 1.7 %; p < 0.001) was higher, whereas global longitudinal strain was lower (−19.0 ± 1.9 vs. −19.8 ± 1.5 % p < 0.001) in T1D.

Conclusions

Adolescents with T1D exhibit early changes in blood pressure, peripheral vascular function and left ventricular myocardial deformation indices with a shift from longitudinal to circumferential shortening. Longitudinal follow-up of these changes in ongoing prospective trials may allow detection of those most at risk for cardiovascular abnormalities including hypertension that could preferentially benefit from early therapeutic interventions.

[Echocardiography in diabetic cardiomyopathy]

The term diabetic cardiomyopathy was initially introduced in the 1980s when evidence was found that diabetes leads to a distinct cardiomyopathy, independent of coronary artery disease or hypertension. The detection of diabetic cardiomyopathy using echocardiography is challenging because no pathognomonic signs exist; however, it is the merit especially of the newer echocardiographic techniques, such as deformation imaging, that it is now possible to describe the morphology and function of diabetic hearts. Unfortunately, no long-term echocardiography studies are available describing disease progression in detail. Therefore, staging and differential diagnosis of diabetic cardiomyopathy remains challenging. This review tries to fill this gap by presenting a possible echocardiographic staging algorithm. Early stages of diabetic cardiomyopathy are marked by a deterioration of longitudinal systolic function and a compensative elevated radial function. Diastolic dysfunction is another early sign. When the disease progresses the functional deterioration is accompanied by morphological changes, such as left ventricular concentric hypertrophy and fibrosis. End stage disease is characterized by reduced ejection fraction and ventricular dilatation. Very late stage can mimic dilative cardiomyopathy.

A new insight of mechanisms, diagnosis and treatment of diabetic cardiomyopathy

Diabetes mellitus is one of the most common chronic diseases across the world. Cardiovascular complication is the major morbidity and mortality among the diabetic patients. Diabetic cardiomyopathy, a new entity independent of coronary artery disease or hypertension, has been increasingly recognized by clinicians and epidemiologists. Cardiac dysfunction is the major characteristic of diabetic cardiomyopathy. For a better understanding of diabetic cardiomyopathy and necessary treatment strategy, several pathological mechanisms such as impaired calcium handling and increased oxidative stress, have been proposed through clinical and experimental observations. In this review, we will discuss the development of cardiac dysfunction, the mechanisms underlying diabetic cardiomyopathy, diagnostic methods, and treatment options.

Cardiovascular disease risk in young people with type 1 diabetes

Cardiovascular disease (CVD) is the most frequent cause of death in people with type 1 diabetes (T1D), despite modern advances in glycemic control and CVD risk factor modification. CVD risk identification is essential in this high-risk population, yet remains poorly understood. This review discusses the risk factors for CVD in young people with T1D, including hyperglycemia, traditional CVD risk factors (dyslipidemia, smoking, physical activity, hypertension), as well as novel risk factors such as insulin resistance, inflammation, and hypoglycemia. We present evidence that adverse changes in cardiovascular function, arterial compliance, and atherosclerosis are present even during adolescence in people with T1D, highlighting the need for earlier intervention. The methods for investigating cardiovascular risk are discussed and reviewed. Finally, we discuss the observational studies and clinical trials which have thus far attempted to elucidate the best targets for early intervention in order to reduce the burden of CVD in people with T1D.

Cardiovascular function/dysfunction in adolescents with type 1 diabetes

Type 1 diabetes mellitus (T1D) is associated with an increased risk of cardiovascular disease (CVD) that begins in childhood. Youth with T1D develop concerning functional cardiac and vascular defects and evidence of early atherosclerosis, despite modern advancements in risk reduction and glycemic management. Such early defects predict poor long-term outcomes. Women with T1D also have higher CVD risk than expected for unexplained reasons. Insulin resistance (IR) is recently recognized as a prominent factor in T1D youth and adults, but with an atypical clinical phenotype. This IR may contribute to early cardiac and vascular dysfunction and long-term CVD in T1D. A better understanding of potential contributors to cardiovascular dysfunction in T1D youth such as IR and its unique phenotype in T1D, subtle lipid abnormalities, and gender differences is now required to address the current knowledge gaps and to prevent cardiovascular morbidity and mortality in T1D.

The effects of obesity and type 2 diabetes mellitus on cardiac structure and function in adolescents and young adults

AIMS/HYPOTHESIS

We sought to evaluate the effects of obesity and obesity-related type 2 diabetes mellitus on cardiac geometry (remodelling) and systolic and diastolic function in adolescents and young adults.

METHODS

Cardiac structure and function were compared by echocardiography in participants who were lean, obese or obese with type 2 diabetes (obese diabetic), in a cross sectional study. Group differences were assessed using ANOVA. Independent determinants of cardiac outcome measures were evaluated with general linear models.

RESULTS

Adolescents with obesity and obesity-related type 2 diabetes were found to have abnormal cardiac geometry compared with lean controls (16% and 20% vs <1%, p < 0.05). These two groups also had increased systolic function. Diastolic function decreased from the lean to obese to obese diabetic groups with the lowest diastolic function observed in the obese diabetic group (p < 0.05). Regression analysis showed that group, BMI z score (BMIz), group × BMIz interaction and systolic BP z score (BPz) were significant determinants of cardiac structure, while group, BMIz, systolic BPz, age and fasting glucose were significant determinants of the diastolic function (all p < 0.05).

CONCLUSIONS/INTERPRETATION

Adolescents with obesity and obesity-related type 2 diabetes demonstrate changes in cardiac geometry consistent with cardiac remodelling. These two groups also demonstrate decreased diastolic function compared with lean controls, with the greatest decrease observed in those with type 2 diabetes. Adults with diastolic dysfunction are known to be at increased risk of progressing to heart failure. Therefore, our findings suggest that adolescents with obesity-related type 2 diabetes may be at increased risk of progressing to early heart failure compared with their obese and lean counterparts.

Diabetic cardiomyopathy: from the pathophysiology of the cardiac myocytes to current diagnosis and management strategies

Diabetic cardiomyopathy (DCM), although a distinct clinical entity, is also a part of the diabetic atherosclerosis process. It may be independent of the coexistence of ischemic heart disease, hypertension, or other macrovascular complications. Its pathological substrate is characterized by the presence of myocardial damage, reactive hypertrophy, and intermediary fibrosis, structural and functional changes of the small coronary vessels, disturbance of the management of the metabolic cardiovascular load, and cardiac autonomic neuropathy. These alterations make the diabetic heart susceptible to ischemia and less able to recover from an ischemic attack. Arterial hypertension frequently coexists with and exacerbates cardiac functioning, leading to the premature appearance of heart failure. Classical and newer echocardiographic methods are available for early diagnosis. Currently, there is no specific treatment for DCM; targeting its pathophysiological substrate by effective risk management protects the myocardium from further damage and has a recognized primary role in its prevention. Its pathophysiological substrate is also the objective for the new therapies and alternative remedies.

Left ventricular diastolic dysfunction in adolescents with type 1 diabetes reflects the long- but not short-term metabolic control

OBJECTIVE

The aim of this study was to compare the LV morphology and function in adolescents with DM1 and their healthy peers.

SUBJECTS AND METHODS

In 59 DM1 patients (30 girls, 29 boys,aged 14-17 years), and in control group (15 girls, 15 boys) LV was assessed by M-mode, 2D and Doppler echocardiography. The metabolic control was assessed in the long- (mean HbAlc value for the entire treatment period-HbA1c1), medium- (mean HbA1c for the past two pre-study years-HbA1c2), and short-term (HbA1c on the day of the study-HbA1c3).

RESULTS

Diabetic patients presented an increase of IRT (0.062 vs. 0.056 s, p < 0.05 in boys, and 0.062 vs. 0.056 s, p < 0.05 in girls), A wave (56.1 vs. 53.95 cm/s in boys, and 60.3 vs. 58 cm/s in girls), and deceleration time values (0.16 vs. 0.15 s in boys, and 0.17 vs. 0.15 s in girls), decrease of E wave (97.35 vs. 104.9 cm/s in boys, and 99.67 vs. 101.8 cm/s in girls), as well as the E/A ratio (1.79 vs. 2.0 in boys, and 1.7 vs. 1.78 in girls). The systolic function was normal. In girls there was a correlation between IRT and HbA1c1 and HbA1c2 (r = 0.42, r = 0.46, p < 0.05); between the A wave and HbA1c2 (r = 0.46, p < 0.05); between LV posterior wall systolic dimension and HbA1c1, HbA1c2 (r = 0.45, r = 0.41, p < 0.05), and in boys between the A wave and HbA1c1 and HbA1c2 (r = 0.48, p < 0.01; r = 0.37, p < 0.05).

CONCLUSIONS

Pubertal patients with DM1 demonstrate discrete impairment of the diastolic function beside normal systolic function of the LV. Further investigations are needed to assess the value of this observation. It seems that LV diastolic dysfunction in girls depends on the degree of insulin resistance and DM1 duration, and similarly as in boys, on the long-term metabolic control.

Insulin resistance in adolescents with type 1 diabetes and its relationship to cardiovascular function

CONTEXT

Cardiovascular disease is the major cause of death in adults with diabetes, yet little is specifically known about the effects of type 1 diabetes (T1D) on cardiovascular outcomes in youth. Although insulin resistance (IR) likely contributes to exercise and cardiovascular dysfunction in T2D, IR is not typically considered a contributor in T1D.

OBJECTIVE

We hypothesized that cardiopulmonary fitness would be reduced in T1D youth in association with IR and cardiovascular dysfunction.

DESIGN AND PARTICIPANTS

This cross-sectional study at an academic hospital included 12 T1D adolescents compared with 12 nondiabetic controls, similar in age, pubertal stage, activity level, and body mass index.

OUTCOME MEASURES

Cardiopulmonary fitness was measured by peak oxygen consumption (VO(2)peak) and oxygen uptake kinetics (VO(2)kinetics), IR by hyperinsulinemic clamp, cardiac function by echocardiography, vascular function by venous occlusion plethysmography, intramyocellular lipid by magnetic resonance spectroscopy, and body composition by dual-energy x-ray absorptiometry.

RESULTS

T1D adolescents had significantly decreased VO(2)peak, peak work rate, and insulin sensitivity compared with nondiabetic adolescents. T1D youth also had reduced vascular reactivity and evidence of diastolic dysfunction and left ventricular hypertrophy. Despite their IR and reduced cardiovascular fitness, T1D youth had paradoxically normal intramyocellular lipid, waist to hip ratio, and serum lipids and high adiponectin levels. In multivariate analysis, IR primarily, and forearm blood flow secondarily, independently predicted VO(2)peak.

CONCLUSIONS

T1D youth demonstrated IR, impaired functional exercise capacity and cardiovascular dysfunction. The phenotype of IR in T1D youth was unique, suggesting a pathophysiology that is different from T2D, yet may adversely affect long-term cardiovascular outcomes.

Cardiovascular impairment in children, adolescents, and young adults with type 1 diabetes mellitus (T1DM)

Left ventricular (LV) function was assessed in 42 patients (mean age +/- SD, 18.45 +/- 3.76 years; 17 males) with type I diabetes mellitus (T1DM; mean duration 9.89 years) and in 43 healthy controls (mean age +/- SD, 18.27 +/- 3.36 years; 18 males). Systolic, diastolic cardiac function and LV dimensions were assessed using M-mode and Doppler echocardiography. Neural autonomic function was assessed by measuring RR variation during deep breathing, Valsava maneuver, 30/15 ratio, and blood pressure response to standing. Fractional shortening, peak velocity of early ventricular filling (E wave), peak velocity of LV filling (A wave), E/A ratio, deceleration time, isovolumic relaxation time, LV dimensions (interventricular septum, posterior wall thickness, end diastolic diameter [EDD] and systolic diameter [ESD]) were all comparable between patients with T1DM and controls. However, in 11 T1DM patients with microalbuminuria and/or retinopathy, EDD, ESD, E/A ratio, and E wave were all lower (p = 0.0011, p = 0.019, p = 0.0011, and p = 0.030, respectively) while, A wave, heart rate, and diastolic blood pressure were all higher (p = 0.008, p = 0.0024 and p = 0.004, respectively) compared to matched for age and sex controls. Furthermore, in six of the 11 T1DM patients with microangiopathy who had E/A <1.12 (<2 SD of the control mean), significant and marginally significant correlations were found between E/A ratio and the duration of the disease as well as the mean HbA1c of the last year (r = -0.38, p = 0.011 and r = -0.287, p = 0.064, respectively). In conclusion, it has been found that impairment of diastolic, but not systolic, LV function can be detected early in young patients with T1DM and microangiopathy.

Asymptomatic cardiomyopathy in children and adolescents with type 1 diabetes mellitus: association of echocardiographic indicators with duration of diabetes mellitus and metabolic parameters

This study was designed to determine the relationship of dimensions, wall thickness and function of the left ventricle with diabetes duration, fasting blood glucose, lipid profile, beta-OH-butyrate, free fatty acids (FFA) and carnitine levels in children and adolescents with type 1 diabetes mellitus (DM1) who had no cardiovascular complications. Thirty-five patients with DM1 (18 F/17 M, mean age: 12.0 years) and age matched control children (n = 24) were enrolled in the study. Patients with DM1 were subdivided into Group I (mean DM1 duration 3.5 years, n = 14), and Group II (mean DM1 duration 8.2 years, n = 21). Dimensions, wall thickness and systolic functions of the left ventricle were normal in all patients with DM1. Diastolic functions were normal in Group I. In Group II, peak A wave velocity (AVEL) (p = 0.004), velocity-time integral of A wave (AVTI) (p = 0.007) and isovolumetric relaxation time corrected by heart rate (cIVRT) (p = 0.048) were high, and peak E wave velocity (EVEL) and velocity-time integral of E wave (EVTI) were normal. E/A (p < 0.0001) and EVTI/AVTI (p = 0.001) were low in this group. In Group I, systolic and diastolic blood pressure, HDL-cholesterol and FFA values were normal; total cholesterol (p = 0.047), LDL-cholesterol (p = 0.017), beta-OH-butyrate (p = 0.003), and acetyl carnitine (p = 0.006) levels were high. In Group II, diastolic blood pressure (p = 0.008), total cholesterol (p < 0.0001) and LDL-cholesterol (p < 0.0001) were increased; and total carnitine (p = 0.019), free carnitine (p = 0.002) and HDL-cholesterol (p = 0.039) were decreased. Correlations were detected between total carnitine and AVEL and HR; free carnitine and AVEL, E/A and HR; HbA1c and EVTI/AVTI and cIVRT; LDL-cholesterol and E/A, EVTI/AVTI ratios and cIVRT; HDL-cholesterol and AVEL; FFA and LVDD, IVSD, LVPWD, LVmass and CO; metabolic parameters and DM1 duration and echocardiographic findings such as AVEL, EVEL, EVTI, VmaxAV and CO. In conclusion, left ventricular dimensions, wall thickness and systolic functions were normal in children and adolescents with DM1 who had no obvious cardiovascular complications. Left ventricular diastolic functions were abnormal in patients of Group II. Left ventricular diastolic function abnormalities were associated with glycemic control, free and total carnitine, and LDL- and HDL-cholesterol levels.

Nephropathy, but not retinopathy, is associated with the development of heart disease in Type 1 diabetes: a 12-year observation study of 462 patients

AIMS

To study the occurrence of heart disease and death in Type 1 diabetic patients and evaluate whether presence of microangiopathy, i.e. nephropathy and retinopathy, was associated with the outcome.

METHODS

A 12-year observation study of 462 Type 1 diabetic patients without a previous history of heart disease at baseline who were treated under routine care in a hospital out-patient clinic.

RESULTS

A total of 85 patients developed signs of heart disease, i.e. myocardial infarction (n = 41), angina (n = 23), and heart failure (n = 17) and 56 patients died. The mortality for patients without signs of heart disease during the observation period was 7.6% compared with 51% in patients with myocardial infarction (P < 0.001), 26% in patients with angina (P < 0.01) and 65% in patients with heart failure (P < 0.001). The relative risk for death was 9.0 (P < 0.001) and 2.5 (P < 0.05) times higher in patients with macroalbuminuria and microalbuminuria, respectively. The risk for cardiovascular death was 18.3 times (P < 0.001) higher in patients with macroalbuminuria compared with patients with normoalbuminuria. In patients with sight-threatening retinopathy, the relative risk for death was 7.0 times higher (P < 0.01) and the risk for coronary heart disease events 4.4 times higher (P < 0.05) compared with patients with no retinopathy. However, when retinopathy was adjusted for presence of macroalbuminuria, this association disappeared.

CONCLUSION

This study shows a high incidence of heart disease in patients with Type 1 diabetes. The worse prognosis was seen in patients with sight-threatening retinopathy and macroalbuminuria and microalbuminuria at baseline. Macroalbuminuria and microalbuminuria were independently associated with a high risk for heart disease and death while the association with sight-threatening retinopathy only occurred in the presence of nephropathy.

Early Diabetes-Related Complications in Adolescents

Micro- and macrovascular complications account for the major part of the morbidity and mortality associated with diabetes developing in childhood. Although advanced complications are exceptionally rare in the adolescent age group, it is during this phase that the progression of risk may accelerate. A number of potentially important factors have been identified which might contribute to risk of complication development: some provide insights into the genetics of these complications, while others are potentially modifiable, such as metabolic control, hypertension, smoking, obesity and hyperlipidemia. Recently, both consensus and evidence-based guidelines have been developed to guide those involved in the care of adolescents with diabetes in the prevention, screening and management of early diabetes-related complications in this vulnerable population. This article reviews the literature that underpins the available guidelines and stresses the pivotal role of excellent metabolic control in complication prevention.

Cardiovascular effects of endomorphins in alloxan-induced diabetic rats

Endomorphins, the endogenous, potent and selective mu-opioid receptor agonists, have been shown to decrease systemic arterial pressure (SAP) in rats. In the present study, responses to endomorphins were investigated in systemic vascular bed of alloxan-induced diabetic rats and in non-diabetic rats. Diabetes was induced by alloxan (220 mg/kg, i.p.) in male Wistar rats. At 4-5 weeks after the onset of diabetes, intravenous injections of endomorphins (1-30 nmol/kg) led to an increase of SAP and heart rate (HR) consistently and dosed-dependently. SAP increased 7.68+/-3.73, 11.19+/-4.55, 21.19+/-2.94 and 27.48+/-6.21% from the baseline at the 1, 3, 10 and 30 nmol/kg dose, respectively, of endomorphin 1 (n=4; p<0.05), and similar changes were observed in response to endomorphin 2. The hypertension could be antagonized markedly by i.p. 2 mg/kg of naloxone. On the other hand, bilateral vagotomy would attenuate the effects of hypertension and diminished the changes of HR in response to endomorphins. With diabetic rats, 6-10 weeks after the induction of diabetes, intravenous injections of endomorphins produced non-dose-related various changes in SAP, such as a single decrease, or a single increase, or biphasic changes characterized by an initial decrease followed by a secondary increase, or no change at all. These results suggest that diabetes may lead to the dysfunction of the cardiovascular system in response to endomorphins. Furthermore, the diabetic rats of 4-5 weeks after alloxan-treatment, the increase in SAP and HR caused by i.v. endomorphins might be explained by a changed effect of vagus and by a naloxone-sensitive mechanism.

Diabetes mellitus and heart failure: basic mechanisms, clinical features, and therapeutic considerations

Diabetic cardiomyopathy encompasses the spectrum from subclinical disease to the full-blown syndrome of congestive heart failure. The prevalence of type 2 diabetes mellitus is increasing at an alarming rate in the western world. and with it, the frequency of diabetes-related heart failure. There is at least early suggestion that target-driven, long-term, intensified intervention that is aimed at multiple risk factors in patients who have type 2 diabetes and microalbuminuria may reduce the risk of macrovascular (cardiovascular) and micro-vascular complications by approximately 50%. Thus, it is imperative that patients, particularly those who are at risk for the cardiovascular dysmetabolic syndrome, be screened aggressively for the presence of glucose intolerance and diabetes. When detected, all metabolic and cardio-vascular parameters should be evaluated and treated aggressively to reach currently recommended clinical targets. Such action will result in great benefit for patients by reducing morbidity and mortality and improving quality of life and will reduce the financial burden that is associated with this epidemic disease.

Diabetic cardiomyopathy: mechanisms, diagnosis and treatment

Independent of the severity of coronary artery disease, diabetic patients have an increased risk of developing heart failure. This clinical entity has been considered to be a distinct disease process referred to as 'diabetic cardiomyopathy'. Experimental studies suggest that extensive metabolic perturbations may underlie both functional and structural alterations of the diabetic myocardium. Translational studies are, however, limited and only partly explain why diabetic patients are at increased risk of cardiomyopathy and heart failure. Although a range of diagnostic methods may help to characterize alterations in cardiac function in general, none are specific for the alterations in diabetes. Treatment paradigms are very much limited to interpretation and translation from the results of interventions in non-diabetic patients with heart failure. This suggests that there is an urgent need to conduct pathogenetic, diagnostic and therapeutic studies specifically in diabetic patients with cardiomyopathy to better understand the factors which initiate and progress diabetic cardiomyopathy and to develop more effective treatments.

Cardiac and vascular function in adolescents and young adults with type 1 diabetes

The objective was to prospectively define cardiac and vascular function in adolescents and young adults with type 1 diabetes over a 3-year period. Thirty-three subjects with type 1 diabetes were studied in 1998, and 28 returned for follow-up in 2001. There were 28 controls without diabetes. All subjects underwent ultrasonography of the carotid artery to determine distensibility, compliance, and intimal-medial thickness, as well as echocardiographic studies, lipid profile, and measurement of hemoglobin A1c (HbA1c) levels and urinary albumin excretion rate. The diabetes group showed no significant change over the 3-year follow-up in lipid profile, HbA1c level, or albumin excretion rate, but a significant increase in body mass index. The diabetes and control groups were similar in age, lipid profile, and albumin excretion rate. Carotid artery distensibility and compliance in the diabetes group increased significantly from baseline to follow-up but did not differ significantly from controls. The intimal-medial thickness of the diabetes group remained unchanged over time but tended to be higher than controls. Echocardiographic studies showed no difference between the diabetes and control groups, but there was a small change in left ventricular posterior diastolic wall diameter in the subjects with diabetes over the 3-year period. There was an overall improvement in carotid function and no change in cardiac measures in subjects with diabetes over the 3 years, such that cardiac and vascular function were similar to those of controls. The reason for the improvement is uncertain, but may relate to the improvement of insulin sensitivity at the end of the pubertal growth period, rather than to changes in metabolic control or lipid profiles.

Diabetes Mellitus and Heart Failure

The metabolic abnormalities associated with diabetes mellitus result in macrovascular and microvascular complications in multiple organ systems; it is the cardiovascular impact that accounts for the greatest morbidity and mortality associated with this disease. Heart failure, both with reduced and preserved systolic function, is a major complication, arising from the frequent associations with coronary atherosclerosis, hypertension, and a specific heart muscle dysfunction (cardiomyopathy) that occurs independently of coronary artery disease. Hyperglycemia, insulin resistance, and hypertension, together with activation of both the circulating and the tissue renin-angiotensin-aldosterone systems, contribute to structural fibrosis and autonomic neuropathy. Thus, it becomes imperative to identify cardiac abnormalities early in the course of both type 1 and type 2 diabetes to allow early and aggressive intervention to control glucose and blood pressure and to normalize blood lipid profiles. Patients with diabetes should be treated to secondary prevention targets, including blood pressure less than 130/80 mm Hg and low-density lipoprotein cholesterol level less than 100 mg/dL. Angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers,beta blockers, calcium channel-blockers, statins, and aspirin have all been demonstrated to significantly reduce cardiovascular morbidity and mortality in patients with diabetes.

Vascular rarefaction in peripheral skeletal muscle after experimental heart failure

A decrease in vascular density in peripheral skeletal muscle has been associated with exercise intolerance in humans with congestive heart failure (CHF). The purpose of this study was to determine whether CHF results in a reduction in vascular density in peripheral skeletal muscle. In this established model, CHF was induced by coronary artery ligation in New Zealand White rabbits and sham rabbits that underwent an identical surgical procedure without ligation of the coronary artery. At study termination, rabbits underwent hemodynamic testing and skeletal muscle analysis. The first series of rabbits was divided into sham (n = 6) and CHF (n = 6) 21 days postoperatively. Ten CHF rabbits were then examined 3 (n = 3), 7 (n = 3), and 14 days (n = 4) postoperatively. Vascular density in sham tibialis anterior muscle was 347 +/- 41 capillaries/mm2 or 1.20 +/- 0.11 capillaries/muscle fiber. In 21-day CHF rabbits, the capillary density was significantly lower, 236 +/- 14 capillaries/mm2 or 0.84 +/- 0.04 capillaries/muscle fiber (both P < 0.00001 vs. sham); PECAM protein was 2-fold lower (P < 0.0001) in muscle protein lysates; the fraction of apoptotic cells was greater, 3.8 +/- 2.2 vs. 0.69 +/- 0.56 (P < 0.02 vs. sham) with many TdT-mediated dUTP-biotin nick-end labeling-positive endothelial cells; and Bax protein was 2.8-fold greater (P < 0.0001). By regression analysis, vascular density tended to decrease over time (r2 = 0.572, P < 0.0001). Vascular rarefaction and endothelial apoptosis develop after experimental CHF and may contribute to the skeletal muscle abnormalities in this disease. Modulating vascular density may provide new approaches to treat exercise intolerance in CHF.

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.

Carotid artery distensibility and cardiac function in adolescents with type 1 diabetes

OBJECTIVE

To determine the presence and correlates of early heart and blood vessel dysfunction in adolescents with type 1 diabetes mellitus (DM) of relatively short duration.

STUDY DESIGN

A total of 33 patients with DM (20 male, mean age 15.8 +/- 1.3 years, mean DM duration 9.3 +/- 3.9 years) and 16 healthy subjects in a nondiabetic control group (7 male, mean age 17.4 +/- 1.7 years) underwent (1) ultrasonography of the right carotid artery to assess distensibility, compliance, and intimal-medial thickness (IMT), (2) echocardiographic assessment of systolic and diastolic ventricular function, (3) lipid profile and hemoglobin A(1c), and (4) overnight timed urine collections for albumin excretion rate.

RESULTS

Ultrasonography showed significantly lower carotid artery distensibility in the DM group (38.5 +/- 8.2 x 10(-3) vs 46.5 +/- 11.7 x 10(-3)/kPa, P =.01) but no difference in compliance (14.0 +/- 3.4 x 10(-7) vs 15.8 +/- 2.9 x 10(-7)m(2)/kPa, P =.08) or IMT (0.061 +/- 0.013 vs 0.060 +/- 0.014 cm, P =.77). Left ventricular (LV) end-diastolic diameter, LV posterior wall thickness, end-systolic wall stress, shortening fraction, ejection fraction, LV mass, and diastolic function were similar in both groups. Total cholesterol, low density lipoprotein, high density lipoprotein, triglycerides, and blood pressure were also similar. The median albumin excretion rate was 4.8 microg/min in the DM group (range 1.1 to 19.2) and 3.0 microg/min in the control group (range 1.4 to 5.8) (P =.03). Hemoglobin A(1c) correlated inversely with both distensibility (r = -.43, P =.02) and compliance (r = -.39, P =.032).

CONCLUSIONS

This study indicates that early changes in macrovascular function, namely lower carotid artery distensibility, may precede abnormalities in cardiac function or in arterial IMT in adolescents with short duration type 1 DM. It also supports a relationship between hyperglycemia and carotid artery dysfunction.

[Left ventricular diastolic dysfunction in young people with type 1 diabetes mellitus. Associated factors]

AIM

The aim of our study was to evaluate left ventricular function of diastolic in young (< 40 years) asymptomatic patients with type 1 diabetes mellitus free of cardiovascular disease symptoms and to analyze the associated factors to the left ventricular diastolic dysfunction (LVDD) in these patients.

PATIENTS AND METHODS

Thirty-five type-1 diabetic patients (mean age 27.8+/-7.5 years) old and 54 healthy controls (mean age 26.1+/-4.1 years) were studied. Anamnesis, physical exploration, general analytical studies, microalbuminuric and Doppler-echocardiographic studies were performed.

RESULTS

The LVDD was present in 13 (37.1%) of the diabetic patients and none of the control patients. The ratio of peak early to peak late (atrial) filling velocity was significantly decreased in diabetic compared with control subjects (1.1+/-0.3 versus 1.5+/-0.2; p<0.01). The isovolumetric relaxation time was increased in diabetic patients compared with control subjects (104+/-11 versus 79+/-11; p<0.01). Diabetics with LVDD were older aged, predominantly males, had worse glucemic control, more alteration of lipidic metabolism and higher levels of microalbuminuria, than diabetics without LVDD.

CONCLUSIONS

The LVDD is frequent in young diabetics free of cardiovascular disease symptoms. These studies suggest that because this patients were of older age, of the masculine sex with, poor glucemic control, altered lipidic metabolism, and microalbuminuria they might be a group that is associated with LVDD which, in the absence of cardiovascular disease, might be an early preclinical alteration, potentially related to subsequent development of diabetic cardiomyopathy.

Early diabetes-related complications in children and adolescents with type 1 diabetes. Implications for screening and intervention

Although children and adolescents with type 1 diabetes are faced with the threat of the acute complications of hypoglycemia and ketoacidosis on a day-to-day basis, in the long-term, the microvascular and macrovascular complications of the disease place them at greatest risk for serious morbidity and earlier than expected mortality. The families of children with diabetes should be provided with information about the complications of diabetes beginning at the time of diagnosis, and this information needs to be reinforced throughout the follow-up period. Appropriate surveillance for the earliest evidence of microvascular disease should begin at the onset of puberty and after 3 to 5 years of diabetes. Therapeutic interventions, particularly excellent metabolic control, may be exceedingly effective in preventing complication onset or significantly retarding the rate of progression.

Prevention of coronary heart disease. Part I. Primary prevention

The first concern in primary prevention is the physician's belief that primary prevention is important for all adults and that intervention can significantly affect risk. Given the coronary plaque burden over many years and the importance of the development of healthy lifestyles early in adulthood to decrease coronary plaque burden, there are excellent reasons to begin prevention even with young adults. At the very least, a patient seen for any reason should provide a smoking history, have knowledge of the presence of early CHD in first-degree relatives and measurements of blood pressure, height, and weight, provide evidence for a cholesterol level within 5 years (after age 20 according to NCEP guidelines or in middle age according to ACP guidelines), and be given an assessment of glucose tolerance or diabetes. Information about alcohol intake and physical activity status are also of some importance. Other than height, weight, and blood pressure, during the physical examination, the physician should initially assess the strength of pulses in the lower extremities, evidence for carotid or femoral bruits, and eyegrounds for retinal arterial changes, and the skin and subcutaneous tissue should be examined for xanthomas and the eyes should be examined for corneal arcus and xanthelesma. These elements should be part of any initial examination by a primary care physician and are not extraordinary. In addition to lipid and blood sugar analyses, other evaluations may include blood urea nitrogen and creatinine and electrolytes in patients with hypertension or diabetes or in patients who are on antihypertensive agents. It may be prudent to obtain an ECG for patients who are older than 40 years. The elements mentioned above are the elements of the history, physical examination, and laboratory examination in subjects without a past history of CHD and with no clinical evidence for CHD. Primary prevention management begins with a discussion of risk factors with the patient. The key interventions aim at the lowering of blood pressure to at least less than 140/90 mm Hg, the complete cessation of smoking, the lowering of lipid levels to less than 130 mg/dL, the lowering of triglycerides to less than 200 mg/dL (or, some would argue, < 150 mg/dL), and the attempt to keep HDL cholesterol above 35 mg/dL (more than 40 to 45 mg/dL is a better goal) with the use of lifestyle modification. For patients with diabetes, strict control of glucose levels is essential to minimize disease of the microvasculature and possibly to minimize progressive renal disease. There are several lifestyle modifications for lipids. For patients with elevated LDL cholesterol, modifications include a less than 30% fat calorie diet and less than 300 mg of cholesterol intake daily, with fat calories approximately equally distributed among saturated fats, polyunsaturated fats, and monounsaturated fats (1/3, 1/3, 1/3; rule of 3s). The assistance of a dietician is extremely helpful in this regard. For patients with a low HDL cholesterol, weight reduction (for overweight patients) by calorie control and increased physical activity and smoking cessation will have some modest effect. For patients with elevated triglycerides, a diet similar to that for lowering of LDL cholesterol with the addition of stricter calorie limitation, avoidance of refined sugars, increase in complex carbohydrates, and avoidance of alcohol will be helpful. A decrease in the percent of fat calories to 20% to 25% will be of assistance to those patients with particularly high triglycerides. The treatment of underlying conditions such as diabetes mellitus, hypothyroidism, liver disease, and some renal conditions may also significantly modify high triglycerides. For patients with hypertension, limitation of sodium to 2 gm/d (6 gm sodium chloride), limitation of alcohol to 1 to 2 drinks a day, increased physical activity, and weight reduction are the key lifestyle modifications. (ABSTRACT TRUNCATED)

Angiogenesis

Angiogenesis, the growth and proliferation of blood vessels from existing vascular structures, is tightly regulated in adult tissues, and abnormalities in angiogenesis are associated with a number of pathologic states. Strategies designed to promote angiogenesis to treat disorders of inadequate tissue perfusion, such as occurs in coronary artery and peripheral vascular disease, have led to the area of therapeutic angiogenesis. Approaches to block angiogenesis are actively being explored to treat diseases that range from arthritis to cancer. This article will review some of the basic concepts of vascular development and the mechanisms involved in angiogenesis. Particular attention will be paid to the growth factors and receptors that are known to mediate angiogenesis, and a description of some of the cell signaling mechanisms that are involved in the regulation of angiogenesis will be described. Finally, potential targets that may provide opportunities to enhance or block angiogenesis will be discussed.

Nocturnal blood pressure in young patients with insulin-dependent diabetes mellitus: correlation with cardiac function

Lack of a decline in nocturnal blood pressure is associated with an adverse effect on end organs in adults with insulin-dependent diabetes mellitus (IDDM). The role of the decline in nocturnal blood pressure in young patients with IDDM is not known. We studied 25 white subjects with IDDM (age = 20.8 +/- 3.7 years, mean +/- SD), 8 of whom were female. The duration of IDDM in these subjects was 12.9 +/- 5.4 years (mean +/- SD). We determined the values for glycosylated hemoglobin (HgbA1), 24-hour ambulatory blood pressure, diastolic cardiac function (the ratio of peak E wave to peak A wave velocity (E/A) and indexed peak filling rate ¿PFR/SV¿ by Doppler echocardiography), and albumin excretion rate. The HgbA1 level was 10.9% +/- 1.9% (mean +/- SD; normal range = 4.5%-8.5%). The HgbA1 concentration was inversely correlated (p < 0.005) with the decline in systolic (r = 0.57) and diastolic (r = -0.55) nocturnal blood pressure. Diastolic cardiac dysfunction ¿E/A ratio [r = 0.42, p < 0.03) and PFR/SV (r = 0.52, p < 0.01)¿ correlated with a smaller decrease in nocturnal diastolic blood pressure. An inverse correlation between decline in nocturnal systolic blood pressure and log albumin excretion rate (r = -0.37, p = 0.07) approached statistical significance. We conclude that poor glycemic control adversely affects nocturnal blood pressure and that the latter may play an important role in cardiac and possibly renal dysfunction in early IDDM.

The acute effect of hyperglycaemia on vessel wall properties

Arterial distensibility is a marker of functional and structural vessel wall properties. A decreased distensibility is an important risk factor for cardiovascular disease. In insulin-dependent diabetes mellitus of short duration, arterial stiffness has been reported to be increased, decreased or the same as in healthy control subjects. The influence of acute hyperglycaemia on arterial stiffness is unclear and might be one of the factors responsible for the divergent results which have been observed. We investigated arterial distensibility locally in the carotid artery during hyper- and normoglycaemia using a glucose clamp technique. Eleven healthy normotensive men underwent both a hyperglycaemic and a euglycaemic clamp on separate days. Before and after 2 h of clamping, arterial diameter (D) and change in arterial diameter during the heart cycle (dD) were measured with a non-invasive vessel wall movement detector system. Blood pressure (BP), pulse pressure (dP) and heart rate (HR) were recorded with a semi-automated device. Distensibility coefficients (DC), reflecting the intrinsic vascular wall elasticity, and compliance coefficients (CC), reflecting the buffering capacity of the vessel, were calculated from D, dD and dP. (DC = 2*dD/ D*dP, CC = pi*dD*D/2*dP). There were no significant differences between the hyperglycaemic and the euglycaemic clamp for D, DC and CC. These results suggest that an acute systemic hyperglycaemia is not responsible for changes in diameter, distensibility and compliance of the carotid artery.

Inappropriate use of bivariable analysis to screen risk factors for use in multivariable analysis

The use of bivariable selection (BVS) for selecting variables to be used in multivariable analysis is inappropriate despite its common usage in medical sciences. In BVS, if the statistical p value of a risk factor in bivariable analysis is greater than an arbitrary value (often p = 0.05), then this factor will not be allowed to compete for inclusion in multivariable analysis. This type of variable selection is inappropriate because the BVS method wrongly rejects potentially important variables when the relationship between an outcome and a risk factor is confounded by any confounder and when this confounder is not properly controlled. This article uses both hypothetical and actual data to show how a nonsignificant risk factor in bivariable analysis may actually be a significant risk factor in multivariable analysis if confounding is properly controlled. Furthermore, problems resulting from the automated forward and stepwise modeling with or without the presence of confounding are also addressed. To avoid these improper procedures and deficiencies, alternatives in performing multivariable analysis, including advantages and disadvantages of the BVS method and automated stepwise modeling, are reviewed and discussed.