Layer-specific systolic and diastolic strain in hypertensive patients with and without mild diastolic dysfunction

Cardiac response to hypertension treatment: an advanced echocardiographic evaluation

BACKGROUND

Hypertension is the most common reversible cause of cardiovascular disease worldwide and more than one billion individuals suffer from the disease. Constant heart exposure to increased afterload progresses to maladaptive remodeling, leading to cardiac dysfunction. In this study, we aimed to evaluate cardiac function in response to hypertension treatment.

METHODS

One hundred patients diagnosed with hypertension were evaluated two times, with 3 to 6 months intervals, before and after antihypertensive therapy. Patients underwent clinical and echocardiographic evaluation in both visits and the interest effect of antihypertensive therapy on cardiac function was studied.

RESULTS

58 men and 42 women with a mean age of 60.81 ± 11.8 years were studied. Mean systolic and diastolic pressure in the first visit was 163.05 ± 20.6 and 95.40 ± 10.4, respectively. On the second visit, mean systolic and diastolic pressure was 129.95 ± 10.4 and 82.35 ± 7.2 respectively (P value for both < 0.001). The mean value of Global Longitudinal Strain as the main parameter for evaluating left ventricular systolic function was -15.54% on the first visit and changed to -16.95% on the second visit (P value 0.025).

CONCLUSIONS

According to the results of this study, changes in parameters, indicator of systolic and diastolic function, after 3-6 months of antihypertensive therapy are significant. The most important point is that maladaptive remodeling of the heart is reversible if hypertension is diagnosed timely. To follow-up patients under antihypertensive therapy, GLS and parameters indicator of diastolic dysfunction, have the best diagnostic value in terms of detecting early stages of cardiac injury.

Materials and Design Approaches for a Fully Bioresorbable, Electrically Conductive and Mechanically Compliant Cardiac Patch Technology

Myocardial infarction (MI) is one of the leading causes of death and disability. Recently developed cardiac patches provide mechanical support and additional conductive paths to promote electrical signal propagation in the MI area to synchronize cardiac excitation and contraction. Cardiac patches based on conductive polymers offer attractive features; however, the modest levels of elasticity and high impedance interfaces limit their mechanical and electrical performance. These structures also operate as permanent implants, even in cases where their utility is limited to the healing period of tissue damaged by the MI. The work presented here introduces a highly conductive cardiac patch that combines bioresorbable metals and polymers together in a hybrid material structure configured in a thin serpentine geometry that yields elastic mechanical properties. Finite element analysis guides optimized choices of layouts in these systems. Regular and synchronous contraction of human induced pluripotent stem cell-derived cardiomyocytes on the cardiac patch and ex vivo studies offer insights into the essential properties and the bio-interface. These results provide additional options in the design of cardiac patches to treat MI and other cardiac disorders.

DeepStrain Evidence of Asymptomatic Left Ventricular Diastolic and Systolic Dysfunction in Young Adults With Cardiac Risk Factors

Purpose

To evaluate if a fully-automatic deep learning method for myocardial strain analysis based on magnetic resonance imaging (MRI) cine images can detect asymptomatic dysfunction in young adults with cardiac risk factors.

Methods

An automated workflow termed DeepStrain was implemented using two U-Net models for segmentation and motion tracking. DeepStrain was trained and tested using short-axis cine-MRI images from healthy subjects and patients with cardiac disease. Subsequently, subjects aged 18–45 years were prospectively recruited and classified among age- and gender-matched groups: risk factor group (RFG) 1 including overweight without hypertension or type 2 diabetes; RFG2 including hypertension without type 2 diabetes, regardless of overweight; RFG3 including type 2 diabetes, regardless of overweight or hypertension. Subjects underwent cardiac short-axis cine-MRI image acquisition. Differences in DeepStrain-based left ventricular global circumferential and radial strain and strain rate among groups were evaluated.

Results

The cohort consisted of 119 participants: 30 controls, 39 in RFG1, 30 in RFG2, and 20 in RFG3. Despite comparable (>0.05) left-ventricular mass, volumes, and ejection fraction, all groups (RFG1, RFG2, RFG3) showed signs of asymptomatic left ventricular diastolic and systolic dysfunction, evidenced by lower circumferential early-diastolic strain rate (<0.05, <0.001, <0.01), and lower septal circumferential end-systolic strain (<0.001, <0.05, <0.001) compared with controls. Multivariate linear regression showed that body surface area correlated negatively with all strain measures (<0.01), and mean arterial pressure correlated negatively with early-diastolic strain rate (<0.01).

Conclusion

DeepStrain fully-automatically provided evidence of asymptomatic left ventricular diastolic and systolic dysfunction in asymptomatic young adults with overweight, hypertension, and type 2 diabetes risk factors.

Long-term athletic training does not alter age-associated reductions of left-ventricular mid-diastolic lengthening or expansion at rest

Purpose

The interaction of ageing and exercise training status on left-ventricular (LV) peak strain is unclear. Additionally, strain analysis across the entire cardiac cycle facilitates a more detailed assessment of deformation, yet this has not been implemented to characterize the ageing LV and in association with training status. This study investigated healthy ageing and training status on LV systolic and diastolic strain utilizing novel echocardiographic applications.

Methods

Forty healthy males were included and allocated into four groups; young recreationally active (Y_RA,n = 9; 28 ± 5 years), old recreationally active (O_RA, n = 10; 68 ± 6), young trained (Y_T,n = 10; 27 ± 6 years), and old trained (O_T, n = 11, 64 ± 4 years) groups. Two-dimensional speckle-tracking echocardiography was performed to ascertain peak LV longitudinal and circumferential strain (base and apex) strain within each myocardial layer and at 5% increments across the cardiac cycle.

Results

Older groups had lower diastolic longitudinal lengthening and circumferential expansion between 40–85% mid-diastole, regardless of training status (P < 0.05). Whereas, strain throughout systole was similar between groups (P > 0.05). Longitudinal and circumferential (base and apex) peak and layer-specific strain did not differ between groups (P > 0.05).

Conclusion

Novel applications of diastolic strain revealed lower age-associated LV longitudinal lengthening and circumferential expansion in older age. Yet, diastolic strain profiles did not differ based on chronic habits of exercise training and, thus, older trained men did not demonstrate an attenuation of age-associated differences in mid-diastolic LV strain.

Electronic supplementary material

The online version of this article (10.1007/s00421-020-04418-1) contains supplementary material, which is available to authorized users.

Microtubules Increase Diastolic Stiffness in Failing Human Cardiomyocytes and Myocardium

BACKGROUND

Diastolic dysfunction is a prevalent and therapeutically intractable feature of heart failure (HF). Increasing ventricular compliance can improve diastolic performance, but the viscoelastic forces that resist diastolic filling and become elevated in human HF are poorly defined. Having recently identified posttranslationally detyrosinated microtubules as a source of viscoelasticity in cardiomyocytes, we sought to test whether microtubules contribute meaningful viscoelastic resistance to diastolic stretch in human myocardium.

METHODS

Experiments were conducted in isolated human cardiomyocytes and trabeculae. First, slow and rapid (diastolic) stretch was applied to intact cardiomyocytes from nonfailing and HF hearts and viscoelasticity was characterized after interventions targeting microtubules. Next, intact left ventricular trabeculae from HF patient hearts were incubated with colchicine or vehicle and subject to pre- and posttreatment mechanical testing, which consisted of a staircase protocol and rapid stretches from slack length to increasing strains.

RESULTS

Viscoelasticity was increased during diastolic stretch of HF cardiomyocytes compared with nonfailing counterparts. Reducing either microtubule density or detyrosination reduced myocyte stiffness, particularly at diastolic strain rates, indicating reduced viscous forces. In myocardial tissue, we found microtubule depolymerization reduced myocardial viscoelasticity, with an effect that decreased with increasing strain. Colchicine reduced viscoelasticity at strains below, but not above, 15%, with a 2-fold reduction in energy dissipation upon microtubule depolymerization. Post hoc subgroup analysis revealed that myocardium from patients with HF with reduced ejection fraction were more fibrotic and elastic than myocardium from patients with HF with preserved ejection fraction, which were relatively more viscous. Colchicine reduced viscoelasticity in both HF with preserved ejection fraction and HF with reduced ejection fraction myocardium.

CONCLUSIONS

Failing cardiomyocytes exhibit elevated viscosity and reducing microtubule density or detyrosination lowers viscoelastic resistance to diastolic stretch in human myocytes and myocardium. In failing myocardium, microtubules elevate stiffness over the typical working range of strains and strain rates, but exhibited diminishing effects with increasing length, consistent with an increasing contribution of the extracellular matrix or myofilament proteins at larger excursions. These studies indicate that a stabilized microtubule network provides a viscous impediment to diastolic stretch, particularly in HF.