Obesity dominates early effects on cardiac structure and arterial stiffness in people with type 2 diabetes.

OBJECTIVE: Type 2 diabetes (T2D) and obesity are global epidemics leading to excess cardiovascular disease (CVD). This study investigates standard and novel cardiac MRI parameters to detect subclinical cardiac and central vascular dysfunction in inactive people with and without T2D. METHODS: Physically inactive age and BMI-similar premenopausal women and men with ( n  = 22) and without [ n  = 34, controls with overweight/obesity (CWO)] uncomplicated T2D were compared to an age-similar and sex-similar reference control cohort ( n  = 20). Left ventricular (LV) structure, function, and aortic stiffness were assessed by MRI. Global arterial pulse wave velocity (PWV) was assessed using carotid-to-femoral applanation tonometry. Regional PWV was measured via 2D phase-contrast MRI and 4D flow MRI. RESULTS: Global arterial PWV did not differ between CWO and T2D. 2D PC-MRI PWV in the ascending aorta was higher in people with T2D compared with CWOs ( P  < 0.01). 4D flow PWV in the thoracic aorta was higher in CWO ( P  < 0.01), and T2D ( P  < 0.001) compared with RC. End-diastolic volume, end-systolic volume, stroke volume, and cardiac output were lower in CWO and T2D groups compared with reference control. CONCLUSION: Subclinical changes in arterial stiffening and cardiac remodeling in inactive CWO and T2D compared with reference control support obesity and/or physical inactivity as determinants of incipient CVD complications in uncomplicated T2D. Future studies should determine the mechanistic causes of the CVD complications in greater detail in order to create therapeutic targets. CLINICAL TRIAL REGISTRATION: Cardiovascular Mechanisms of Exercise Intolerance in Diabetes and the Role of Sex (NCT03419195).

Frequency of Reduced Left Ventricular Contractile Efficiency and Discoordinated Myocardial Relaxation in Patients Aged 16 to 21 Years With Type 1 Diabetes Mellitus (from the Emerald Study).

Early-onset cardiomyopathy is a major concern for people with type 1 diabetes mellitus (DM). Studies examining myocardial deformation indices early in the disease process in people with have provided conflicting results. Accordingly, the objective was to examine left ventricular (LV) function in adolescents with type 1 DM using novel measures of cardiomyopathy, termed ventricular discoordination indices, including systolic stretch fraction (SSF), and our newly developed diastolic relaxation fraction (DRF). Adolescents with DM (n = 16) and healthy controls (n = 20) underwent cardiac MRI (CMR) tissue tracking analysis for standard volumetric and functional analysis. Segment-specific circumferential strain and strain rate indices were evaluated to calculate standard mechanical dyssynchrony and discoordination. SSF and DRF were calculated from strain rate data. There were no global or regional group differences between participants with DM and controls in standard LV strain mechanics. However, youth with DM had lower diastolic strain rate around the inferior septal and free wall region (all p <0.05) as well as higher SSF (p = 0.03) and DRF (p <0.001) compared with controls. None of the CMR indices correlated with HbA1c or diabetes duration. In conclusion, our results suggest that adolescents with DM have LV systolic and diastolic discoordination, providing early evidence of cardiomyopathy despite their young age. The presence of discoordination in the setting of normal LV size and function suggests that the proposed novel discoordination indices could serve as a more sensitive marker of cardiomyopathy than previously employed mechanical deformation indices.

Biomechanical properties and microstructure of neonatal porcine ventricles.

Neonatal heart disorders represent a major clinical challenge, with congenital heart disease alone affecting 36,000 new-borns annually within the European Union. Surgical intervention to restore normal function includes the implantation of synthetic and biological materials; however, a lack of experimental data describing the mechanical behaviour of neonatal cardiac tissue is likely to contribute to the relatively poor short- and long-term outcome of these implants. This study focused on characterising the mechanical behaviour of neonatal cardiac tissue using a porcine model, to enhance the understanding of how this differs to the equivalent mature tissue. The biomechanical properties of neonatal porcine cardiac tissue were characterised by uniaxial tensile, biaxial tensile, and simple shear loading modes, using samples collected from the anterior and posterior walls of the right and left ventricles. Histological images were prepared using Masson's trichrome staining, to enable assessment of the microstructure and correlation with tissue behaviour. The mechanical tests demonstrated that the neonatal cardiac tissue is non-linear, anisotropic, viscoelastic and heterogeneous. Our data provide a baseline describing the biomechanical behaviour of immature porcine cardiac tissue. Comparison with published data also indicated that the neonatal porcine cardiac tissue exhibits one-half the stiffness of mature porcine tissue in uniaxial extension testing, one-third in biaxial extension testing, and one-fourth stiffness in simple shear testing; hence, it provides an indication as to the relative change in characteristics associated with tissue maturation. These data may prove valuable to researchers investigating neonatal cardiac mechanics.