The diabetic myocardium

Extracellular volume fraction and native T1 mapping in diabetic cardiomyopathy: a comprehensive meta-analysis

BACKGROUND

Type 2 diabetes mellitus (T2DM) is associated with myocardial fibrosis (MF), a major contributor to adverse cardiovascular outcomes. Cardiovascular magnetic resonance (CMR), specifically extracellular volume fraction (ECV) and native T1 mapping, offers a non-invasive approach to quantify MF. This study aims to evaluate the utility of ECV and native T1 mapping as biomarkers for cardiac fibrosis and to assess their relationship with diabetes severity, measured by hemoglobin A1C (HbA1C), in patients with T2DM.

METHODS

A systematic review and meta-analysis were conducted following PRISMA guidelines. Comprehensive searches identified 19 eligible studies comprising 4,117 participants. Weighted mean differences (WMDs) were calculated for ECV and native T1 values between diabetic and non-diabetic groups. Meta-regression assessed the correlation between ECV and HbA1C. Sensitivity and subgroup analyses were performed to explore heterogeneity.

RESULTS

Diabetic patients exhibited significantly higher ECV values than controls (WMD: 2.17; 95% CI: 1.32-3.02), consistent across subgroups excluding cardiac comorbidities (WMD: 2.02; 95% CI: 0.74-3.31). HbA1C levels were also significantly elevated in diabetics (WMD: 1.78; 95% CI: 1.37-2.19). However, no significant difference in native T1 values was observed (WMD: 13.40; 95% CI: -13.98-40.79). Meta-regression revealed no significant correlation between ECV and HbA1C, potentially due to limited data and high heterogeneity (I²: 93.37%).

CONCLUSIONS

ECV is a promising marker for quantifying MF in T2DM, demonstrating significant differences between diabetics and controls. The lack of correlation between ECV and HbA1C underscores the complexity of MF in diabetes and highlights the need for further research. Future studies with standardized protocols are essential to validate these findings and refine the use of CMR in diabetic cardiomyopathy.

Impact of Diabetes and Increasing Body Mass Index Category on Left Ventricular Systolic and Diastolic Function

BACKGROUND

Diabetes and obesity are both worldwide growing epidemics, and both are independently associated with increased risk for heart failure and death. The aim of this study was to examine the additive detrimental effect of both diabetes and increasing body mass index (BMI) category on left ventricular (LV) myocardial systolic and diastolic function.

METHODS

The present retrospective multicenter study included 653 patients (337 with type 2 diabetes and 316 without diabetes) of increasing BMI category. All patients had normal LV ejection fractions. LV myocardial systolic (peak systolic global longitudinal strain and peak systolic global longitudinal strain rate) and diastolic (average mitral annular e' velocity and early diastolic global longitudinal strain rate) function was quantified using echocardiography.

RESULTS

Increasing BMI category was associated with progressively more impaired LV myocardial function in patients with diabetes (P < .001). Patients with diabetes had significantly more impaired LV myocardial function for all BMI categories compared with those without diabetes (P < .001). On multivariate analysis, both diabetes and obesity were independently associated with an additive detrimental effect on LV myocardial systolic and diastolic function. However, obesity was associated with greater LV myocardial dysfunction than diabetes.

CONCLUSION

Both diabetes and increasing BMI category had an additive detrimental effect on LV myocardial systolic and diastolic function. Furthermore, increasing BMI category was associated with greater LV myocardial dysfunction than diabetes. As they frequently coexist together, future studies on patients with diabetes should also focus on obesity.

Better Indigenous Risk stratification for Cardiac Health study (BIRCH) protocol: rationale and design of a cross-sectional and prospective cohort study to identify novel cardiovascular risk indicators in Aboriginal Australian and Torres Strait Islander adults

BACKGROUND

Of the estimated 10-11 year life expectancy gap between Indigenous (Aboriginal and Torres Strait Islander people) and non-Indigenous Australians, approximately one quarter is attributable to cardiovascular disease (CVD). Risk prediction of CVD is imperfect, but particularly limited for Indigenous Australians. The BIRCH (Better Indigenous Risk stratification for Cardiac Health) project aims to identify and assess existing and novel markers of early disease and risk in Indigenous Australians to optimise health outcomes in this disadvantaged population. It further aims to determine whether these markers are relevant in non-Indigenous Australians.

METHODS/DESIGN

BIRCH is a cross-sectional and prospective cohort study of Indigenous and non-Indigenous Australian adults (≥ 18 years) living in remote, regional and urban locations. Participants will be assessed for CVD risk factors, left ventricular mass and strain via echocardiography, sleep disordered breathing and quality via home-based polysomnography or actigraphy respectively, and plasma lipidomic profiles via mass spectrometry. Outcome data will comprise CVD events and death over a period of five years.

DISCUSSION

Results of BIRCH may increase understanding regarding the factors underlying the increased burden of CVD in Indigenous Australians in this setting. Further, it may identify novel markers of early disease and risk to inform the development of more accurate prediction equations. Better identification of at-risk individuals will promote more effective primary and secondary preventive initiatives to reduce Indigenous Australian health disadvantage.

Protective effect and mechanism of Ginkgo biloba extract-EGb 761 on STZ-induced diabetic cardiomyopathy in rats

Diabetes mellitus (DM) is a complex metabolic disorder which leads to development of various long-term complications including cardiomyopathy. Oxidative stress due to hyperglycemia plays a key role in the development and progression of diabetic cardiomyopathy (DC). Oxidative stress causes the opening of mitochondrial permeability transition pore (mPTP) eventually leading to myocardium dysfunction. The Ginkgo biloba extract (EGb 761) has antioxidant and mitochondrial membrane potential stabilizing property. Therefore, this study was designed to evaluate the effect of EGb 761 and its possible mechanism of action in DC.

Multimodality imaging in diabetic heart disease

Diabetic heart disease is currently defined as left ventricular dysfunction that occurs independently of coronary artery disease and hypertension. Its underlying etiology is likely to be multifactorial, acting synergistically together to cause myocardial dysfunction. Multimodality cardiac imaging, such as echocardiography, nuclear, computed tomography, and magnetic resonance imaging, can provide invaluable insight into different aspects of the disease process, from imaging at the cellular level for altered myocardial metabolism to microvascular and endothelial dysfunction, autonomic neuropathy, coronary atherosclerosis, and finally, interstitial fibrosis with scar formation. Furthermore, cardiac imaging is pivotal in diagnosing diabetic heart disease. Thus, the aim of the present review is to illustrate the role of multimodality cardiac imaging in elucidating the underlying pathophysiologic mechanisms of diabetic heart disease.

Myocardial steatosis and biventricular strain and strain rate imaging in patients with type 2 diabetes mellitus

BACKGROUND

Magnetic resonance spectroscopy can quantify myocardial triglyceride content in type 2 diabetic patients. Its relation to alterations in left (LV) and right (RV) ventricular myocardial functions is unknown.

METHODS AND RESULTS

A total of 42 men with type 2 diabetes mellitus were recruited. Exclusion criteria included hemoglobin A(1c) >8.5, known cardiovascular disease, diabetes-related complications, or blood pressure >150/85 mm Hg. Myocardial ischemia was excluded by a negative dobutamine stress test. LV and RV volumes and ejection fraction were quantified by magnetic resonance imaging. LV global longitudinal and RV free wall longitudinal strain, systolic strain rate, and diastolic strain rate were quantified by echocardiographic speckle tracking analyses. Myocardial triglyceride content was quantified by magnetic resonance spectroscopy and dichotomized on the basis of the median value of 0.76. The median age was 59 years (25th and 75th percentiles, 54 and 62 years). Median diabetes diagnosis duration was 4 years, and median glycohemoglobin level was 6.2 (25th and 75th percentiles, 5.9 and 6.8). There were no differences in LV and RV end-diastolic and end-systolic volume indexes and ejection fraction between patients with high (≥0.76) and those with low (<0.76) myocardial triglyceride content. However, patients with high myocardial triglyceride content had greater impairment of LV and RV myocardial strain and strain rate. The myocardial triglyceride content was an independent correlate of LV and RV longitudinal strain, systolic strain rate, and diastolic strain rate.

CONCLUSIONS

High myocardial triglyceride content is associated with more pronounced impairment of LV and RV functions in men with uncomplicated type 2 diabetes mellitus.

Increased O2 cost of basal metabolism and excitation-contraction coupling in hearts from type 2 diabetic mice

We have reported previously that hearts from type 2 diabetic ( db/ db) mice show decreased cardiac efficiency due to increased work-independent myocardial O2 consumption (unloaded MV̇o2), indicating higher O2 use for nonmechanical processes such as basal metabolism (MV̇o2BM) and excitation-contraction coupling (MV̇o2ECC). Although alterations in cardiac metabolism and/or Ca2+ handling may contribute to increased energy expenditure in diabetic hearts, direct measurements of the O2 cost for these individual processes have not been determined. In this study, we 1) validate a procedure for measuring unloaded MV̇o2 directly (MV̇o2unloaded) and for determining MV̇o2BM and MV̇o2ECC separately in isolated perfused mouse hearts and 2) determine O2 cost for these processes in hearts from db/ db mice. Unloaded MV̇o2, extrapolated from the relationship between cardiac work (measured as pressure-volume area, PVA) and MV̇o2, was found to correspond with MV̇o2 measured directly in unloaded retrograde perfused hearts (MV̇o2unloaded). MV̇o2 in K+-arrested hearts was defined as MV̇o2BM; the difference between MV̇o2unloaded and MV̇o2BM represented MV̇o2ECC. This procedure was validated by demonstrating that elevations in perfusate fatty acid (FA) and/or Ca2+ concentrations resulted in changes in either MV̇o2BM and/or MV̇o2ECC. The higher MV̇o2unloaded in db/ db mice was due to both a higher MV̇o2BM and MV̇o2ECC. Elevation of glucose and insulin decreased FA oxidation and reduced both MV̇o2unloaded and MV̇o2BM. In conclusion, this study provides direct evidence that MV̇o2BM and MV̇o2ECC are elevated in diabetes and that acute metabolic interventions can have a therapeutic benefit in diabetic hearts due to a MV̇o2-lowering effect.