Effects of type 1 diabetes mellitus on cardiac function: a study of monozygotic twins

Atrial remodeling and atrial fibrillation in acquired forms of cardiovascular disease

Atrial fibrillation (AF) is prevalent in common conditions and acquired forms of heart disease, including diabetes mellitus (DM), hypertension, cardiac hypertrophy, and heart failure. AF is also prevalent in aging. Although acquired heart disease is common in aging individuals, age is also an independent risk factor for AF. Importantly, not all individuals age at the same rate. Rather, individuals of the same chronological age can vary in health status from fit to frail. Frailty can be quantified using a frailty index, which can be used to assess heterogeneity in individuals of the same chronological age. AF is thought to occur in association with electrical remodeling due to changes in ion channel expression or function as well as structural remodeling due to fibrosis, myocyte hypertrophy, or adiposity. These forms of remodeling can lead to triggered activity and electrical re-entry, which are fundamental mechanisms of AF initiation and maintenance. Nevertheless, the underlying determinants of electrical and structural remodeling are distinct in different conditions and disease states. In this focused review, we consider the factors leading to atrial electrical and structural remodeling in human patients and animal models of acquired cardiovascular disease or associated risk factors. Our goal is to identify similarities and differences in the cellular and molecular bases for atrial electrical and structural remodeling in conditions including DM, hypertension, hypertrophy, heart failure, aging, and frailty.

Echocardiography improves prediction of major adverse cardiovascular events in a population with type 1 diabetes and without known heart disease: the Thousand & 1 Study

AIMS/HYPOTHESIS

Cardiovascular disease is the most common comorbidity in type 1 diabetes. However, current guidelines do not include routine assessment of myocardial function. We investigated whether echocardiography provides incremental prognostic information in individuals with type 1 diabetes without known heart disease.

METHODS

A prospective cohort of individuals with type 1 diabetes without known heart disease was recruited from the outpatient clinic. Follow-up was performed through Danish national registers. The association of echocardiography with major adverse cardiovascular events (MACE) and the incremental prognostic value when added to the clinical Steno T1D Risk Engine were examined.

RESULTS

A total of 1093 individuals were included: median (interquartile range) age 50.2 (39.2-60.3) years and HbA_1c 65 (56-74) mmol/mol; 53% men; and mean (SD) BMI 25.5 (3.9) kg/m² and diabetes duration 25.8 (14.6) years. During 7.5 years of follow-up, 145 (13.3%) experienced MACE. Echocardiography significantly and independently predicted MACE: left ventricular ejection fraction (LVEF) <45% (n = 18) vs ≥45% (n = 1075), HR (95% CI) 3.93 (1.91, 8.08), p < 0.001; impaired global longitudinal strain (GLS), 1.65 (1.17, 2.34) (n = 263), p = 0.005; diastolic mitral early velocity (E)/early diastolic tissue Doppler velocity (e') <8 (n = 723) vs E/e' 8-12 (n = 285), 1.59 (1.04, 2.42), p = 0.031; and E/e' <8 vs E/e' ≥12 (n = 85), 2.30 (1.33, 3.97), p = 0.003. In individuals with preserved LVEF (n = 1075), estimates for impaired GLS were 1.49 (1.04, 2.15), p = 0.032; E/e' <8 vs E/e' 8-12, 1.61 (1.04, 2.49), p = 0.033; and E/e' <8 vs E/e' ≥12, 2.49 (1.41, 4.37), p = 0.001. Adding echocardiographic variables to the Steno T1D Risk Engine significantly improved risk prediction: Harrell's C statistic, 0.791 (0.757, 0.824) vs 0.780 (0.746, 0.815), p = 0.027; and net reclassification index, 52%, p < 0.001.

CONCLUSIONS/INTERPRETATION

In individuals with type 1 diabetes without known heart disease, echocardiography significantly improves risk prediction over and above guideline-recommended clinical risk factors alone and could have a role in clinical care.

Resting heart rate and relation to disease and longevity: past, present and future

Assessment of heart rate has been used for millennia as a marker of health. Several studies have indicated that low resting heart rate (RHR) is associated with health and longevity, and conversely, a high resting heart to be associated with disease and adverse events. Longitudinal studies have shown a clear association between increase in heart rate over time and adverse events. RHR is a fundamental clinical characteristic and several trials have assessed the effectiveness of heart rate lowering medication, for instance beta-blockers and selective sinus node inhibition. Advances in technology have provided new insights into genetic factors related to RHR as well as insights into whether elevated RHR is a risk factor or risk marker. Recent animal research has suggested that heart rate lowering with sinus node inhibition is associated with increased lifespan. Furthermore, genome-wide association studies in the general population using Mendelian randomization have demonstrated a causal link between heart rate at rest and longevity. Furthermore, the development in personal digital devices such as mobile phones, fitness trackers and eHealth applications has made heart rate information and knowledge in this field as important as ever for the public as well as the clinicians. It should therefore be expected that clinicians and health care providers will be met by relevant questions and need of advice regarding heart rate information from patients and the public. The present review provides an overview of the current knowledge in the field of heart rate and health.

Cardiac dysfunction in type II diabetes: a bittersweet, weighty problem, or both?

AIMS

Weight loss in obese patients leads to improved left ventricular (LV) function. It is unclear whether improving glycaemic control has additional benefits to weight loss alone in patients with type 2 diabetes, or if benefits of weight loss are mediated through improving glycaemic control. This case-control study examined the incremental impact of these approaches on LV function.

METHODS

Three groups of age, gender, and baseline HbA1c-matched patients with type 2 diabetes and suboptimal glycaemic control were followed-up for 12 months. Group 1 patients did not improve HbA1c ≥ 1 % (10.9 mmol/mol) or lose weight. Group 2 improved HbA1c ≥ 1 % but did not lose weight. Group 3 improved HbA1c ≥ 1 % (10.9 mmol/mol) and lost weight. All patients underwent transthoracic echocardiogram at baseline and at follow-up.

RESULTS

At baseline, three groups were comparable in all clinical and metabolic parameters except Group 3 had highest body mass index. The three groups had similar echocardiographic parameters except Group 3 had the worst LV systolic function [global longitudinal strain (GLS)]. At follow-up, LV ejection fraction and diastolic function improved with a reduction in filling pressures in Group 2 and more so in Group 3. LV filling pressures in Group 1 increased. There was a significant improvement in GLS in Group 2 and more so in Group 3. Despite GLS being the worst in Group 3 at baseline, this was comparable between Groups 2 and 3 at follow-up.

CONCLUSIONS

In overweight patients with type 2 diabetes, weight loss and improved glycaemic control had additive beneficial effects on improving LV systolic and diastolic function.

Impact of Improved Glycemic Control on Cardiac Function in Type 2 Diabetes Mellitus

BACKGROUND

Patients with type 2 diabetes mellitus are at risk of heart failure. Specific therapeutic interventions for diabetic heart disease are still elusive. We aimed to examine the impact of improved glycemic control on left ventricular (LV) function in these patients.

METHODS AND RESULTS

A total of 105 subjects with type 2 diabetes mellitus (aged 54±10 years) and poor glycemic control received optimization of treatment for blood glucose, blood pressure, and cholesterol to recommended targets for 12 months. LV systolic and diastolic function, measured by LV global longitudinal strain (GLS) and septal e' velocities, were compared before and after optimization. At baseline, patients had impaired LV systolic (GLS -14.9±3.2%) and diastolic function (e' 6.2±1.7 cm/s). After 12 months, glycated hemoglobin (HbA1c) decreased from 10.3±2.4% to 8.3±2.0%, which was associated with significant relative improvement in GLS of 21% and septal e' of 24%. There was a progressively greater improvement in GLS as patients achieved a lower final HbA1c. Patients achieving an HbA1c of <7.0% had the largest improvement. The 15 patients whose HbA1c worsened experienced a decline in GLS. Patients who improved their HbA1c by ≥1.0% had a significantly higher relative improvement in e' than those who did not (32% versus 8%; P=0.003). Baseline GLS, decrease in body mass index, and treatment with metformin were additional independent predictors of GLS improvement.

CONCLUSIONS

Improvements in glycemic control over a 12-month period led to improvements in LV systolic and diastolic function. This may have long-term prognostic implications.

[Assessment of diastolic function in children and adolescents with type 1 diabetes mellitus - are there early signs of diabetic cardiomyopathy?]

OBJECTIVES

To evaluate diastolic function (DF) of children and adolescents with type 1 diabetes mellitus (DM1).

SUBJECTS AND METHODS

Cross-sectional study of 67 otherwise healthy diabetic patients, and a control group (n = 84) in regard to age, sex, body mass index (BMI), Dopplere-chocardiography, and ECG for both groups; and disease duration, HbA1C, microalbuminuria, and serum lipids for DM 1 patients.

RESULTS

Diastolic alterations [(A and E mitral waves, E/A ratio, isovolumic relaxation time (IVRT) and E wave deceleration time (EWDT)] were found in diabetic patients, with higher prevalence among pubertal girls (13-17 years old). IVRT and EWDT correlated positively with BMI (p = 0.028). Chronological age and disease duration were predictive factors for mitral A wave (p = 0.004 and 0.033, respectively).

CONCLUSIONS

DF alterations were detected in the group of diabetic patients, with greater prevalence among pubertal girls; disease duration and age influenced parameters of DF.

Diabetic cardiomyopathy in Manipur

Objective:

To assess the prevalence of diabetic cardiomyopathy in patients with diabetes mellitus in Manipur and its correlation with different parameters like obesity, blood pressure, lipids, duration of diabetes, and glycemic control.

Materials and Methods:

A total of 100 type 2 diabetic patients were selected randomly. Anthropometric parameters were recorded, blood glucose levels and lipid profiles were determined, and the echocardiographic examinations were performed in all patients according to standard techniques. Ejection fraction (EF) was calculated by the formula LVEF% = (LVID)2 - (LVIDS)2. Left ventricular EF was considered normal when EF was 55 to 75%. Diastolic dysfunction was calculated by measuring E and A transmitral inflow velocity. Left ventricular mass in grams is calculated by the formula LVM (gm) = 1.04 × 0.8 [(LVID + PWT + IVST)3 - LVID3] + 0.6.

Results and Conclusions:

Diabetic cardiomyopathy was found in 40 patients (40%) of the total study, 29 males (44.6%) and 11 females (31.4%).

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.

Correlates of echocardiographic indices of cardiac remodeling over the adult life course: longitudinal observations from the Framingham Heart Study

BACKGROUND

The heart progressively remodels over the life course, yet longitudinal data characterizing such remodeling in the community are limited.

METHODS AND RESULTS

Using multilevel modeling, we analyzed up to 4 serial echocardiographic observations obtained over a 16-year period in 4062 Framingham Heart Study participants (mean age 45 years, 54% women; 11 485 person-observations). We related left ventricular (LV) wall thickness, LV systolic and diastolic dimensions, and fractional shortening to age, sex, body mass index, blood pressure (including antihypertensive medication use), smoking, and diabetes mellitus (separate analyses for each echocardiographic measure). With advancing age, LV dimensions decreased, whereas fractional shortening and LV wall thickness increased concomitantly. Male sex, body mass index, and blood pressure indices/hypertension treatment were significantly related to both greater LV dimensions and LV wall thickness. The effect of age on cardiac remodeling was influenced by key covariates (P<0.05 for all interactions): Women and individuals with diabetes mellitus experienced greater age-associated increases in LV wall thickness; presence of diabetes or a higher blood pressure was associated with a lesser decrease in LV diastolic dimensions with increasing age; and antihypertensive medication use was a marker of an attenuated increase in fractional shortening with aging.

CONCLUSIONS

Cardiac remodeling over the adult life course is characterized by a distinct pattern of increasing LV wall thickness, decreasing LV dimensions, and increasing fractional shortening with advancing age. Overall, female sex, greater blood pressure load, and presence of diabetes mellitus serve to attenuate this remodeling pattern. These observations suggest a mechanism for the preponderance of women with hypertension and individuals with diabetes among patients with diastolic heart failure.

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.

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

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

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.

Diabetes and diastolic function: stiffness and relaxation from transmitral flow

To characterize the mechanism by which diabetes affects the heart in diabetic (n = 15) and age-matched control subjects (n = 15), we quantified and compared diastolic function (DF) in terms of chamber stiffness and viscosity/relaxation by analyzing Doppler E- and E'-waves and simultaneous (high-fidelity) hemodynamic data. We compared tau, standard Doppler indexes and indexes of stiffness and viscosity/relaxation computed via the parameterized diastolic filling (PDF) formalism. Three PDF parameters uniquely characterize each E-wave in terms of load (x(o)), viscoelasticity or viscosity/relaxation (c) and stiffness (k). Significant differences for c (p = 0.00004), the peak atrioventricular pressure gradient (kx(o)) (p = 0.02) and the stored elastic energy available for early filling (1/2kx(o)2) (p = 0.04) were found. The only conventional index attaining significance was E-wave acceleration time (p = 0.007). Neither time constant of isovolumic relaxation (tau) nor E-wave deceleration time, E', k or x(o) differentiated between groups. We conclude that PDF based DF assessment differentiates between diabetic and nondiabetic controls better than conventional echo- or cath-based indexes. Our results in humans agree with published results from animal studies. We conclude that diabetes affects the heart via a quantifiable increase in chamber viscoelasticity (c) rather than an increase in chamber stiffness (k) and that phenotypic characterization of diabetic cardiomyopathy is facilitated by DF assessment via the PDF formalism.

Cardiovascular effects of type 1 diabetes mellitus in children

Previous studies have shown that type 1 diabetes mellitus (DM) is associated with cardiovascular abnormalities. Early detection and treatment of these abnormalities may help to prevent the natural progression of the disease. The present study was undertaken to define early cardiovascular abnormalities in children with type 1 DM. Simultaneous evaluation of multiple cardiovascular parameters was performed in 14 children with type 1 DM and 14 age-and gender-matched normal subjects. Measurements of carotid artery intima-media thickness (cIMT, echocardiography), carotid and aortic (ascending and abdominal) distensibility (echocardiography, brachial artery blood pressure), aortic pulse wave velocity (carotid to femoral artery, Doppler), and left ventricular dimensions, mass, and function (echocardiography) were performed. Diabetic children demonstrated a greater cIMT (0.36 +/- 0.04 mm vs 0.31 +/- 0.03 mm, p = 0.002) and decreased carotid artery distensibility (4.4 +/- 1.6 cm(2) . dynes(-1) . 10(-6) vs 6.0 +/- 1.9 cm(2) . dynes(-1) .10(-6), p < 0.01) compared to control. Aortic pulse wave velocity was increased in DM (6.70 +/- 0.39 vs 6.30 +/- 0.31, p = 0.02) compared to control. Left ventricular diameters, mass, and systolic and diastolic function did not differ between the 2 groups. Simultaneous assessment of multiple cardiovascular parameters in children with type 1 DM revealed impaired carotid artery structure and function, and decreased elastic properties of the aorta, before demonstrable changes in left ventricular structure and function could be detected.

Left ventricular diastolic dysfunction: an early sign of diabetic cardiomyopathy?

The existence of a diabetic cardiomyopathy has been proposed as evidence has accumulated for the presence of myocardial dysfunction in diabetic patients in the absence of ischemic, valvular or hypertensive heart disease. Diastolic dysfunction has been described as an early sign of this diabetic heart muscle disease preceding the systolic damage. Abnormalities in diastolic performance have been first demonstrated by cardiac catheterisation and subsequently by mainly using echocardiography. The pathogenesis of this left ventricular dysfunction is not clearly understood. Microangiopathy, increased extracellular collagen deposition, or abnormalities in calcium transport alone or in combination are considered to be associated with this dysfunction. The relationship between diastolic dysfunction and glycemic control is still a matter of debate. Some epidemiological and clinical arguments suggest that diastolic abnormalities may contribute to the high morbidity and mortality among diabetic patients. However, the prognostic importance of subclinical diastolic dysfunction and the possibilities for intervention are not fully known. Eventually, despite numerous studies, evidence of an intrinsic diastolic dysfunction in diabetes mellitus remains questionable. Indeed, quite contradictory results have been reported. They have been obtained in small, inhomogeneous populations, with sometimes confounding factors, using various echocardiographic indices with known limitations. Also, further studies using more refined techniques for the evaluation of diastolic function are needed, as a prerequisite, to unequivocally relate diabetes mellitus to a specific cardiomyopathy.

The association of fasting glucose levels with congestive heart failure in diabetic adults ≥65 years

OBJECTIVES

The purpose of this study was to determine if fasting glucose levels are an independent risk factor for congestive heart failure (CHF) in elderly individuals with diabetes mellitus (DM) with or without coronary heart disease (CHD).

BACKGROUND

Diabetes mellitus and CHF frequently coexist in the elderly. It is not clear whether fasting glucose levels in the setting of DM are a risk factor for incident CHF in the elderly.

METHODS

A cohort of 829 diabetic participants, age > or =65 years, without prevalent CHF, was followed for five to eight years. The Cox proportional hazards modeling was used to determine the risk of CHF by fasting glucose levels. The cohort was categorized by the presence or absence of prevalent CHD.

RESULTS

For a 1 standard deviation (60.6 mg/dl) increase in fasting glucose, the adjusted hazard ratios for incident CHF among participants without CHD at baseline, with or without an incident myocardial infarction (MI) or CHD event on follow-up, was 1.41 (95% confidence interval 1.24 to 1.61; p < 0.0001). Among those with prevalent CHD at baseline, with or without another incident MI or CHD event on follow-up, the corresponding adjusted hazard ratio was 1.27 (95% confidence interval 1.02 to 1.58; p < 0.05).

CONCLUSIONS

Among older adults with DM, elevated fasting glucose levels are a risk factor for incident CHF. The relationship of fasting glucose to CHF differs somewhat by the presence or absence of prevalent CHD.

Echocardiographic characterization of fundamental mechanisms of abnormal diastolic filling in diabetic rats with a parameterized diastolic filling formalism

Abnormalities of diastolic function (DF) precede systolic dysfunction in diabetic cardiomyopathy. Transmitral Doppler flow analysis is the primary method for noninvasively assessing DF. We used model-based Doppler E-wave analysis to evaluate diastolic function differences between normal and diabetic rat hearts. Control rats and those with diabetes underwent echocardiography with analysis by traditional Doppler indexes and by the parameterized diastolic filling (PDF) formalism, generating 3 parameters, x0, c, and k, that uniquely characterize each E-wave. Significant intergroup differences in the E/A ratios (P <.01), isovolumic relaxation times (P <.01), and the modeling parameter c (P <.05) were found. There were no significant differences in shortening fraction, deceleration time, myocardial collagen content, or the parameters x0 and k between diabetic and control rats. These results indicate that differences in diastolic function may be noninvasively quantified and that diabetic hearts may exhibit defects in uncoupling of the contractile apparatus without concomitant increases in chamber stiffness.

Diastolic dysfunction in normotensive men with well-controlled type 2 diabetes: importance of maneuvers in echocardiographic screening for preclinical diabetic cardiomyopathy

OBJECTIVE

Because a pseudonormal pattern of ventricular filling has never been considered in studies that reported a prevalence of left ventricular diastolic dysfunction (LVDD) between 20 and 40%, our aim was to more completely evaluate the prevalence of LVDD in subjects with diabetes.

RESEARCH DESIGN AND METHODS

We studied 46 men with type 2 diabetes who were aged 38-67 years; without evidence of diabetic complications, hypertension, coronary artery disease, congestive heart failure, or thyroid or overt renal disease; and with a maximal treadmill exercise test showing no ischemia. LVDD was evaluated by Doppler echocardiography, which included the use of the Valsalva maneuver and pulmonary venous recordings to unmask a pseudonormal pattern of left ventricular filling.

RESULTS

LVDD was found in 28 subjects (60%), of whom 13 (28%) had a pseudonormal pattern of ventricular filling and 15 (32%) had impaired relaxation. Systolic function was normal in all subjects, and there was no correlation between LVDD and indexes of metabolic control.

CONCLUSIONS

LVDD is much more common than previously reported in subjects with well-controlled type 2 diabetes who are free of clinically detectable heart disease. The high prevalence of this phenomenon in this high-risk population suggests that screening for LVDD in type 2 diabetes should include procedures such as the Valsalva maneuver and pulmonary venous recordings to unmask a pseudonormal pattern of ventricular filling.

Effects of acute hyperglycaemia on cardiac function: an echocardiographic study of monozygotic twins

BACKGROUND

A major cause of morbidity in type I diabetes is congestive heart failure due predominantly to left ventricular diastolic dysfunction. The mechanism of diastolic dysfunction remains unknown and does not relate to blood pressure, microvascular complications and glycated haemoglobin. Hyperglycaemia is the hallmark of diabetes and is a potential determinant of left ventricular diastolic dysfunction.

OBJECTIVE

To determine whether acute hyperglycaemia can induce changes in left ventricular diastolic function in normal subjects similar to those observed in insulin-dependent diabetes mellitus (IDDM).

DESIGN

Cross-sectional study.

SETTING

London teaching hospital.

SUBJECTS

Sixteen twins from eight identical twin pairs discordant for IDDM (age 18-38 years, five male) were studied; none had a history or evidence of myocardial ischaemia, valvular or primary heart muscle disease, systemic hypertension or nephropathy.

INTERVENTIONS

Non-diabetic twins underwent a hyperglycaemic clamp at 10 mmol/l.

MAIN OUTCOME MEASURES

Doppler echocardiography was performed in basal condition in identical twin pairs discordant for IDDM and repeated in the non-diabetic twins during hyperglycaemia. Blood glucose, insulin and catecholamines were measured at baseline and during hyperglycaemia.

RESULTS

Transmitral Doppler E/A velocity ratio was significantly lower in diabetic than non-diabetic twins at baseline (1.44 (0.38) vs. 1.51 (0.19), P<0.05). Glucose infusion in the non-diabetic twins resulted in an increase in their E/A ratio (1.51 (0.19) vs. 1.82 (0. 47), P<0.05) due to an increase in E velocity (68 (12) to 64.7 (10. 7), P<0.05) and a decrease in the peak A velocity (42.7 (3.85) to 38. 0 (4.1), P<0.05). No significant changes were observed in peak E velocity or isovolumic relaxation time in the non-diabetic twins between baseline and hyperglycaemia.

CONCLUSIONS

The alterations in left ventricular diastolic function induced by acute hyperglycaemia and consequent increase in plasma catecholamines do not mimic those demonstrated in IDDM patients.

High-pass-filtered magnetocardiogram and cardiomyopathy in patients with type 1 diabetes mellitus

Prolonged and/or fractionated depolarization due to tissue degeneration of the ventricular myocardium is a feature of cardiomyopathy. Signal averaged electrocardiography uses high-pass filters of the Butterworth type to quantify, noninvasively, fractionated high-frequency components at the end of the QRS complex. In this study a finite impulse response high-pass filter of the 90th order (cutoff at 37 Hz) was applied to magnetocardiograms (MCGs) and high-resolution electrocardiograms (ECGs) order to quantify high-frequency components throughout the myocardial depolarization. Additionally, late-potential analysis on the signal-averaged ECG was performed. A prospective investigation was made of 23 cardiologically asymptomatic patients, 11 females and 12 males, with type I diabetes mellitus. Their mean age was 21.7 years (range, 13-34 years). The mean duration of diabetes was 14 years (range, 1-27 years). Data were compared with those of 22 control subjects (12 females, 10 males) of mean age, 23.2 years (range, 11-35 years). The ECGs and MCGs were simultaneously recorded and signal-averaged, digitally filtered, and quantified by a score obtained by multiplying the amplitude variation of the signal by the number of maximal/minimal in the QRS complex. Echocardiograms were used to calculate the left ventricular mass and to document the presence of cardiomyopathy. Scores were higher in the MCGs of with type I diabetes mellitus than in the control subjects (P < .001). High scores correlated with an increased left ventricular muscular mass index (P < .05) and duration of the diabetes (P < .05). The high-resolution ECG, processed analogously, showed similar results in relation to left ventricular mass (P = .06) and duration of diabetes (P = .07), respectively (nonsignificant). No late potentials were found. These findings suggest that using a linear-phase high-pass finite impulse response filter may be useful for the noninvasive identification of patients with cardiomyopathy who exhibit possible disturbances of intraventricular depolarization. Our findings also suggest that analysis using the total QRS complex, rather than the final part of the QRS complex only, may improve identification of patients at risk.