Increase In Myocardial Stiffness Research Articles

Cardiac shear wave elastography can detect the presence of a septal scar in patients with LBBB

Abstract Background In patients with heart failure and a left bundle branch block (LBBB), cardiac resynchronization therapy (CRT) is an established treatment. However, the rate of non-response to this costly therapy remains high. So far, CRT has proven to be less effective in patients with a septal scar. Detection of a septal scar before CRT implantation could therefore help to improve response rate to CRT. The gold standard to detect septal scarring, LGE MRI, is quite costly and not suited or available for all patients. Cardiac shear wave elastography (SWE) may be an alternative. It allows for the non-invasive assessment of myocardial stiffness based on the detection of shear waves, after for example mitral valve closure (MVC). SWE has shown to be capable to detect myocardial scar, however this has never been demonstrated in the presence of LBBB. Purpose To determine whether SWE is able to detect the presence of a septal scar in patients with LBBB. Methods To investigate this, 39 CRT patients with a LBBB were included with ischemic (n=10; age: 73±6 y; 70% males) or non-ischemic (n=29; 68±14 y; 52% males) cardiomyopathy and 9 age-matched healthy volunteers (68±4 y; 55% males) served as controls. In order to obtain native ventricular conduction biventricular (BiV) pacing was turned off. All ischemic patients had septal scar only, proven by MRI or scintigraphy. For SWE, left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (frame rate: 932±32 fps). Shear waves were visualized in M-modes of the septum, colour coded for tissue acceleration. The slope of the shear waves in the M-mode represents their propagation speed (Figure 1A). Results Patients characteristics and echocardiographic parameters are shown in Table 1. Shear wave speed after MVC was significantly higher in LBBB patients with and without a septal scar compared to healthy controls (7.8±1.2 m/s vs 4.5±1.1 m/s; p<0.001; 5.6±1.1 m/s vs 4.5±1.1 m/s; p=0.041; Figure 1B), indicating that the presence of LBBB increases myocardial stiffness. However, more importantly, shear wave speed was significantly higher in LBBB patients with a septal scar compared to LBBB patients without a septal scar (7.8±1.2 m/s vs 5.6±1.1 m/s; p<0.001; Figure 1B). This implies that the presence of a septal scar increases shear wave speed even more than LBBB alone. A ROC-curve analysis further showed that SWE is capable of distinguishing scarred from non-scarred septum in LBBB patients (AUC: 0.92; p<0.001; Figure 1C). A cut-off of 7.1 m/s could identify LBBB patients with a septal scar with a sensitivity of 80% and specificity of 93%. Conclusion Septal scarring results in a significant increase in myocardial stiffness, so that it reaches a clear pathological range. SWE seems therefore capable of detecting the presence of a septal scar in LBBB patients and could potentially be used as a novel approach for the assessment of septal scarring in CRT candidates. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research foundation Flanders (FWO)

Abstracts from the NIH Office of Research on Women's Health 2022 Annual BIRCWH Meeting:Building Interdisciplinary Research Careers in Women's Health November 2, 2022

Abstracts from the NIH Office of Research on Women's Health 2022 Annual BIRCWH Meeting:Building Interdisciplinary Research Careers in Women's Health November 2, 2022

Abstract P2051: Incomplete Regression And Persistence Of Interstitial Fibrosis Following Removal Of Left Ventricular Pressure Overload

Background: Left ventricular pressure overload (LVPO) can develop from antecedent conditions, like aortic stenosis, and is associated with increased myocardial collagen content that can lead to increases in myocardial stiffness. Alleviation of LVPO in patients undergoing surgical aortic valve replacement (SAVR) resulted in reduced but persistent fibrosis evident in biopsies taken 5-yrs following SAVR. Little is known regarding cellular mechanisms that contribute to ECM turnover following hemodynamic unloading. Objective: Determine the time course of ECM remodeling after alleviation of LVPO. Methods: Transverse aortic constriction (TAC) was used to induce LVPO. Following 4wks of TAC, alleviation of LVPO was performed by removing the TAC band (unTAC). Five time points were assessed: Control no TAC, 4wk TAC, 4wk TAC+2wk unTAC, 4wk TAC+4wk unTAC, and 4wk TAC+6wk unTAC for cardiomyocyte cross-sectional area (CSA), collagen volume fraction (CVF), collagen degradation, and myocardial stiffness. Results: CSA increased by 47% at 4wk TAC vs control. Compared to 4wk TAC, CSA decreased by 20% at 2wk unTAC, but returned to control levels by 6wk unTAC. CVF increased by 204% at 4wk TAC vs control. Although CVF was similar between 4wk TAC and 2wk unTAC, 2wk unTAC demonstrated robust increases in markers of collagen degradation (cathepsin K, pro-matrix metalloproteinase 2 (pro-MMP2), MMP3, and MMP8). CVF significantly decreased at 4wk unTAC compared to 2wk unTAC. However, the markers of collagen degradation were reduced by 4wk- and 6wk unTAC likely contributing to persistent fibrosis. Furthermore, passive stiffness remained elevated at 6wk unTAC. Conclusion: In LVPO hearts, hypertrophy and fibrosis were present. Although cardiomyocyte hypertrophy fully regressed with normalization of hemodynamic load, increased myocardial stiffness and elevated interstitial fibrosis were persistent.

Phenotypic characterization of primary cardiac fibroblasts from patients with HFpEF.

Heart failure is a leading cause of hospitalizations and mortality worldwide. Heart failure with a preserved ejection fraction (HFpEF) represents a significant clinical challenge due to the lack of available treatment modalities for patients diagnosed with HFpEF. One symptom of HFpEF is impaired diastolic function that is associated with increases in left ventricular stiffness. Increases in myocardial fibrillar collagen content is one factor contributing to increases in myocardial stiffness. Cardiac fibroblasts are the primary cell type that produce fibrillar collagen in the heart. However, relatively little is known regarding phenotypic changes in cardiac fibroblasts in HFpEF myocardium. In the current study, cardiac fibroblasts were established from left ventricular epicardial biopsies obtained from patients undergoing cardiovascular interventions and divided into three categories: Referent control, hypertension without a heart failure designation (HTN (-) HFpEF), and hypertension with heart failure (HTN (+) HFpEF). Biopsies were evaluated for cardiac myocyte cross-sectional area (CSA) and collagen volume fraction. Primary fibroblast cultures were assessed for differences in proliferation and protein expression of collagen I, Membrane Type 1-Matrix Metalloproteinase (MT1-MMP), and α smooth muscle actin (αSMA). Biopsies from HTN (-) HFpEF and HTN (+) HFpEF exhibited increases in myocyte CSA over referent control although only HTN (+) HFpEF exhibited significant increases in fibrillar collagen content. No significant changes in proliferation or αSMA was detected in HTN (-) HFpEF or HTN (+) HFpEF cultures versus referent control. Significant increases in production of collagen I was detected in HF (-) HFpEF fibroblasts, whereas significant decreases in MT1-MMP levels were measured in HTN (+) HFpEF cells. We conclude that epicardial biopsies provide a viable source for primary fibroblast cultures and that phenotypic differences are demonstrated by HTN (-) HFpEF and HTN (+) HFpEF cells versus referent control.

Фактори формування різних типів діастолічного наповнення лівого шлуночка в підлітків із патологією міокарда

Мета: вивчення головних компонентів формування порушеного діастолічного наповнення лівого шлуночка в підлітків із патологією міокарда. Матеріали та методи. Обстежено 110 підлітків із патологією міокарда віком 13–18 років, серед яких 40 — із порушенням ритму серця, 40 — із диспластичною кардіоміопатією, 30 — із первинною артеріальною гіпертензією. Морфофункціональні параметри серця вивчалися за допомогою ультразвукового дослідження за стандартною методикою. Функцію діастоли лівого шлуночка вивчали в імпульсному допплерівському режимі з картируванням трансмітрального потоку з верхівкового доступу чотирикамерного серця. Для адекватної оцінки діастолічної функції лівого шлуночка і визначення найбільш ранніх її порушень підліткам проводилася проба з ізометричним навантаженням. На підставі отриманих результатів підлітки були розподілені за показником співвідношення Е/А. З метою виявлення прихованих загальних факторів, що пояснюють зв’язок між показниками, було застосовано факторний аналіз, а саме метод головних компонент. Усі статистичні процедури проводили з використанням пакетів прикладних програм Statgrafics Centurion. Результати. На початкових етапах становлення діастолічної дисфункції міокарда лівого шлуночка серця в підлітків значну роль відіграє низка факторів, що можна умовно позначити як геометричний, функціональний та нейрогуморальний фактори, які включаються послідовно в патологічний процес. Так, при формуванні 1-го типу діастолічної дисфункції лівого шлуночка на першому місці знаходиться нейрогуморальний фактор, а саме активація симпатоадреналової системи, далі в патологічний процес залучається периферичний судинний тонус та, як наслідок, геометричний фактор — зміна розмірів лівого передсердя. При формуванні 2-го типу діастолічної дисфункції лівого шлуночка в процес послідовно залучається ренін-ангіотензинова система, а саме ренін, функціональний фактор представлено показниками загального периферичного судинного опору та хвилинного об’єму, а геометричний складається з діаметра лівого передсердя та кінцево-діастолічного розміру лівого шлуночка. Формування 3-го типу діастолічної дисфункції лівого шлуночка відбувається під впливом таких складових нейрогуморальної системи, як ренін та ангіотензин II, потім послідовно в процес залучаються периферичний судинний тонус та геометричний фактор у вигляді показників діаметра лівого передсердя та кінцево-діастолічного розміру лівого шлуночка. Отже, на початкових етапах становлення діастолічної дисфункції лівого шлуночка в підлітків із патологією міокарда значну роль відіграють симпатоадреналова система, периферичний судинний тонус та функція лівого передсердя, а далі послідовно підключається ренін-ангіотензинова система, що викликає підвищення жорсткості міокарда та, як наслідок, включення в патологічний процес не тільки лівого передсердя, але й структури (кінцево-діастолічний об’єм) і функції лівого шлуночка серця (ударний об’єм).

Shear Wave Elastography Using High-Frame-Rate Imaging in the Follow-Up of Heart Transplantation Recipients

ObjectivesThe purpose of this study was to investigate whether propagation velocities of naturally occurring shear waves (SWs) at mitral valve closure (MVC) increase with the degree of diffuse myocardial injury (DMI) and with invasively determined LV filling pressures as a reflection of an increase in myocardial stiffness in heart transplantation (HTx) recipients. BackgroundAfter orthotopic HTx, allografts undergo DMI that contributes to functional impairment, especially to increased passive myocardial stiffness, which is an important pathophysiological determinant of left ventricular (LV) diastolic dysfunction. Echocardiographic SW elastography is an emerging approach for measuring myocardial stiffness in vivo. Natural SWs occur after mechanical excitation of the myocardium, for example, after MVC, and their propagation velocity is directly related to myocardial stiffness, thus providing an opportunity to assess myocardial stiffness at end-diastole. MethodsA total of 52 HTx recipients who underwent right heart catheterization (all) and cardiac magnetic resonance (CMR) (n = 23) during their annual check-up were prospectively enrolled. Echocardiographic SW elastography was performed in parasternal long axis views of the LV using an experimental scanner at 1,135 ± 270 frames per second. The degree of DMI was quantified with T1 mapping. ResultsSW velocity at MVC correlated best with native myocardial T1 values (r = 0.75; p < 0.0001) and was the best noninvasive parameter that correlated with pulmonary capillary wedge pressures (PCWP) (r = 0.54; p < 0.001). Standard echocardiographic parameters of LV diastolic function correlated poorly with both native T1 and PCWP values. ConclusionsEnd-diastolic SW propagation velocities, as measure of myocardial stiffness, showed a good correlation with CMR-defined diffuse myocardial injury and with invasively determined LV filling pressures in patients with HTx. Thus, these findings suggest that SW elastography has the potential to become a valuable noninvasive method for the assessment of diastolic myocardial properties in HTx recipients.

Pathogenetic features of morphodensitometric characteristics of cardiomyocytes and marker profile of the left ventricular remodeling in rats with experimental intermittent hypoxia of different duration

Myocardial remodeling is considered as a three-component complex process, including cardiomyocyte hypertrophy, their apoptosis, interstitial and perivascular fibrosis. At the same time, the nature of remodeling and the direction of restructuring in the myocardium depend on the prevalence of one of these processes, the degree of their severity and the impact duration. Therefore, to understand the effect of short- and long-term intermittent hypoxia on the direction of myocardial remodeling and its type, the aim of this study was to determine the pathogenetic features of the morphodensitometric characteristics of cardiomyocytes and the marker profile of left ventricular myocardial remodeling in the rats with experimental intermittent hypoxia durated 15 and 60 days.Material and methods. A total of 30 male Wistar rats aging 6-10 months were used for the experiment and assigned to 3 experimental groups of 10 animals each: control; rats exposed to 15-day hypoxia; rats exposed to 60-day hypoxia. The object of the study was the left ventricular myocardium. The number of nuclei in an image, their average linear size and density (the ratio of the total area of nuclei to the area of the cytoplasm), and the concentration of RNA in the nucleus and cytoplasm were measured in the sections stained by Einarson via morphodensitometric method. An immunofluorescence method was used to study the content of immunoreactive material to markers of remodeling (cardiotrophin-1, type I collagen, titin, annexin V). As a result of the study, it was found that intermittent hypoxia led to a decrease in the number of nuclei in cardiomyocytes in both experimental groups compared to the control. Such changes in the number of nuclei were accompanied by significantly larger nuclear size compared to the control (in rats with 15-day hypoxia by 52.9 %, in rats with 60-day hypoxia - by 153.4 %) and a decrease in the density of nuclei in relation to the cytoplasm by 19.5 % and 21.2 %, respectively. In both groups, a significantly lower control concentration of RNA in the nuclei of cardiomyocytes was found alongside with an increase in their area. Such changes were accompanied by a significantly higher concentration of RNA by 23.2 % in the cytoplasm in case of long-term intermittent hypoxia. The marker profile of remodeling parameters in rats exposed to 15-day hypoxia was characterized by a higher content of cardiotrophin-1 and titin by 11.5 % and 23.1 %, respectively, as compared to the control. The content of type I collagen was 19.9 % higher, while the content of annexin V did not change significantly. In rats with long-term 60-day hypoxia, the content of cardiotrophin-1 was higher by 73.6 %, titin - by 124.9 %, type I collagen - by 41.9 %, and annexin V - by 95.9 % in comparison to the control. When calculating the titin / collagen ratio in rats based on their content, a significant increase in myocardial stiffness was determined in the 60-day hypoxia group which was 1.44, while it was0.91 in the control, and in rats with 15-day short-term hypoxia – 0.93.Conclusions. Intermittent hypoxic effects, regardless of duration, result in morpho-structural rearrangements of the myocardium, are characterized by an increase in viscoelastic mechanical properties and the development of hypertrophy, but with an increase in the duration of exposure (60 days) – by an additional formation of interstitial fibrosis and apoptosis of cardiomyocytes. Short-term hypoxia forms a hypertrophic type of myocardial remodeling with a decrease in the number of nuclei alongside with an increase in their size and a moderate decrease in RNA concentration. The marker profile of remodeling changes in a physiological manner and is characterized by an increase in the content of cardiotrophin-1, type I collagen and titin, while maintaining the titin / collagen ratio and normal apoptotic rate. Long-term hypoxia causes a fibro-apoptotic type of pathological myocardial remodeling including an almost two-fold decrease in the number of nuclei with an increase in their size and a decrease in RNA concentration. The marker profile of remodeling is characterized by an increase in all 4 components, a significant increase in the titin / collagen ratio and high apoptotic rate of cardiomyocytes.

P1569 Left ventricle structure and function relations with renin-angiotensin-aldosteron system activity and plasma markers of fibrosis in patients with ACS underwent PCI

Abstract Renin-angiotensin-aldosterone system (RAAS) plays significant role in development of myocardial fibrosis and LV remodelling which may increase severity of stroke and myocardial infarction. The purpose of the study is to evaluate relations between activity of RAAS and left ventricle structure and function in patients with acute coronary syndrome (ACS) underwent PCI. We examined 204 patients (both men and women) with ACS which were undergoing PCI. The mean age of patients was 51.0 (11) years. In all patients was performed ECG in 12 leads; EchoCG; evaluation plasma levels of aldosterone, angiotensin 2 (AT2), angiotensin-converting enzyme (ACE), tissue inhibitor of metalloproteinases-1 (TIMP-1) and insulin-like growth factor 1 (IGF-1). Statistical significance was defined at the level of methods for p &amp;lt; 0,05. Results of correlative analysis revealed relations between ILV mass and aldosterone (R = 0.57; p &amp;lt; 0.001), ACE (R = 0.59; p &amp;lt; 0.001), AT2 (R = 0.58; p &amp;lt; 0.001) and TIMP-1 (R = 0.54; p &amp;lt; 0.001). There were relations between E/A and AT2 (R = 0.23; p = 0.049), TIMP-1 (R = 0.22; p = 0.038); between IGF-1 and DT (R = 0.21; p = 0.045). This could be due to the growth in fibroblasts and cardiaomyocytes and increase in myocardial stiffness. The results of the comparison of RAAS activity markers, structural and functional parameters of the LV in patients with different LV geometry can be seen in Table 1. Thus, the results of the study show that activation of RAAS leads to increase in myocardial stiffness; and that RAAS activity and plasma markers of fibrosis was significantly higher in patients with concentric and eccentric LV hypertrophy. RAAS activity &amp; LV geometry and function Parameters LV geometry models Normal Geometry n = 25 Concentric Remodelling n = 18 Concentric Hypertrophy n = 89 Eccentric Hypertrophy n = 72 Angiotensin 2 (pg/ml) 36.2 (11.6) 28.2 (5.5) 58.4 (46.; 64.5)*†‡ 45.8 (13.2)*† ACE (u/l) 44.4 (17.4) 30.3 (20.1; 33.0)* 67.6 (28.3)*† 57.1 (39.0; 68.0)† Aldosterone (pg/ml) 111.0 (76.8; 136.6) 101.2 (80.0; 120.5)* 152.4 (135.2; 177.3)*†‡ 136.0 (129.0; 152.0)*† TIMP-1 (ng/ml) 222.9 (80.9) 237.5 (140.0; 322.0)* 358.0 (259.0; 493.0)*†‡ 329.2 (102.5)*† IGF-1 (ng/ml) 174.2 (25.1) 174.5 (160.0; 179.0) 146.0 (129.0; 167.0)*† 148.9 (20.7)*† ILV mass (g/m&amp;sup2;) 85.0 (79.1; 92.4) 94.7 (92.4; 97.9)* 146.3 (127.0; 171.1)*†‡ 127.0 (115.7; 149.0)*† E/A 0.7 (0.1) 0.8 (0.7; 0.9) 0.9 (0.8; 1.2)* 0.9 (0.8; 1.1)*† DT (ms) 194.3 (22.2) 185.4 (19.5) 198.9 (44.3)† 179.1 (26.8) E/e" 8.0 (0.9) 6.1 (5.4; 8.6)* 6.9 (5.5; 9.2)* 8.8 (3.0)† * - p &amp;lt; 0.05 in comparison with patients with normal geometry; † - p &amp;lt; 0.05 in comparison with patients with concentric remodelling; ‡ - p &amp;lt; 0.05 in comparison with patients with eccentric hypertrophy.

Abstract 903: Rapamycin Treatment Reduces Myocardial Stiffness and Promotes Cardiomyocyte Relaxation to Restore Diastolic Function in Old Murine Hearts

Aging is associated with a decline in diastolic function and is a strong risk factor for heart failure with preserved ejection fraction (HFpEF), which has no effective treatment. We previously showed that late-life rapamycin treatment can reverse age-related cardiac dysfunction in mice. However, the mechanisms of the reversal of diastolic dysfunction have not been established. The objective of this study is to determine the mechanisms by which rapamycin reverses age-related diastolic dysfunction. To study the effects of rapamycin on myocardial stiffness, we assessed the passive length-tension relationship of demembranated trabecular muscle from young, old control and old rapamycin-treated mice. We observed a substantial increase in the slope of the length-tension curve with aging, indicating an age-related increase in myocardial stiffness. The age-related increase in myocardial stiffness was significantly reduced by rapamycin treatment, by a mechanism independent of titin isoform shift. We measured the force-calcium relationship of the demembranated trabeculae and revealed an age-related increase in Ca 2+ sensitivity, as indicated by a left-shift of the force-pCa curve, which was partially restored after rapamycin treatment (pCa50: 5.59±0.04 for young controls; 5.76±0.04 for old controls; and 5.65±0.04 for old rapamycin-treated group). To investigate the changes at myofibril level, we assessed kinetic properties of control and rapamycin-treated myofibrils following maximal (pCa 4.0) and submaximal (pCa 5.6) Ca 2+ activation. Myofibrils from rapamycin-treated mice displayed increased rate of the fast phase of relaxation (kREL, fast) compared to old control at both maximal and submaximal Ca 2+ levels, potentially due to reduced myofibril Ca 2+ sensitivity. Studies have detected age-related reductions in expression and activity of SERCA2, which is responsible for SR calcium reuptake during diastole. In this study, we showed that rapamycin increased SERCA2 expression, which may improve cardiomyocyte relaxation. In summary, our results suggest that rapamycin normalizes age-related increases in myocardial stiffness and Ca 2+ sensitivity and improves myofibril relaxation kinetics, therefore, improving diastolic function.

Features of left ventricular remodeling in hypertension patients with comorbid gout

Gout is the most common cause of inflammatory arthritis in men elder than 30 years. The association of gout with hypertension is up to 80 % of cases. Study of cardiovascular system remodeling is very relevant. Aim. To compare the left ventricle remodeling features in patients with hypertension combined with primary gout and patients with essential hypertension without disorders of purine metabolism. Materials and methods. 50 men with hypertension manifested on the gout background, 30 men with essential hypertension without disorders of purine metabolism and 20 healthy men were examined. The main parameters of left ventricle were determined using echocardioscopy. Results. The statistically significant increase in volumetric parameters of the left ventricle in patients with hypertension on the gout background in contrast to the comparison groups and significant decrease in ejection fraction as compared to healthy men were found. The significant increase in left ventricular mass, myocardial mass index and diastolic left ventricle dysfunction in patients with gout were revealed. Using the multivariate analysis of variance we determined an effect of hypertension degree, gout duration and abdominal obesity presence on the process of left ventricle remodeling. The increase in serum uric acid concentration correlated with an increase in left ventricular mass and myocardial mass index. The most of patients with hypertension and gout had the concentric left ventricular hypertrophy. Conclusions . Arterial hypertension on the gout background is characterized by a significant increase in left ventricular mass and myocardial mass index and the prevalence of concentric hypertrophy pattern of left ventricular geometric remodeling in comparison to patients with essential hypertension. Significant increase in myocardial stiffness and its diastolic dysfunction occurred in patients with hypertension on the gout background. Concentration of serum uric acid correlates with the increase in left ventricular mass and myocardial mass index.

Rapamycin Treatment Promotes Myofibril Relaxation Kinetics and Reduces Myocardial Stiffness to Improve Diastolic Function in Old Murine Hearts

At least half of heart failure patients have normal systolic function (heart failure with preserved ejection fraction, HFpEF) and there is no current approved therapy that improves mortality in this patient population. Aging is associated with a decline in diastolic function and is a very strong risk factor for HFpEF, which is especially prevalent in aged women. We previously showed that late‐life 10‐week rapamycin treatment can reverse established cardiac aging, including a reversal of diastolic dysfunction, in old mice. Rapamycin induces mitochondrial remodeling within first 2 weeks of treatment to rejuvenate energy metabolism in old hearts, but the time course of improved diastolic function is much slower. This indicates that additional undefined mechanisms are responsible for the reversal of diastolic dysfunction induced by rapamycin. The objective of this study is to determine the mechanisms of rapamycin‐induced reversal of diastolic dysfunction in old mice.Proteomic analysis revealed that 10‐week rapamycin treatment can partially rescue the age‐related changes in abundance of proteins in actin cytoskeleton and calcium handling pathways. The effects of rapamycin on protein expression of these key pathways regulating contraction and relaxation kinetics suggest that rapamycin may promote relaxation kinetics of the aged myocardium. To determine the effects of aging and rapamycin treatment on biomechanical properties of the myocardium, we measured contractile and relaxation properties of multicellular ventricular trabeculae preparations and isolated myofibrils. Analysis of the passive length‐tension relationship of demembranated trabeculae showed a substantial increase in the slope of the length‐tension curve with aging, indicating an age‐related increase in myocardial stiffness. This age‐related increase in myocardial stiffness is significantly reduced by rapamycin treatment. Trichrome staining revealed similar myocardial collagen contents in old control and rapamycin‐treated mice, suggesting the reduced stiffness is not due to reduced fibrosis. Old myocardial tissues also exhibit increased Ca2+ sensitivity, as denoted by a left‐shift of the isometric force‐pCa curve, which is partially restored by rapamycin treatment. In particular, the Ca2+ concentration required to elicit half maximum force (pCa50) decreased from pCa 5.59±0.08 for young controls to 5.75±0.14 for old controls, and rapamycin treatment restored it to 5.65±0.14. For myofibril relaxation kinetics, myofibrils from rapamycin treated mice displayed increased rate of the fast phase of relaxation (kREL, fast) compared to old control at both maximal (pCa 4.0) and submaximal (pCa 5.6) Ca2+ levels.In summary, these results suggest that rapamycin treatment alters the kinetics of myofibril relaxation and reverses the age‐related increase in myocardial stiffness and Ca2+ sensitivity. These biomechanical changes likely contribute to the reversal of diastolic dysfunction in old murine hearts.Support or Funding InformationNIH K99 AG051735 and Glenn/AFAR Postdoctoral Fellowship for Translational Research on Aging to Y.A.C., NIH K08HL128826 to F.M‐H., and NIH R01 AG038550 to P.S.R.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Ventricular-arterial coupling in centenarians without cardiovascular diseases.

Ventricular-arterial (VA) coupling is a central determinant of cardiovascular system performance and cardiac energetics. This index is expressed by the Ea/Ees ratio, where the effective arterial elastance (Ea) indicates the net arterial load exerted on the left ventricle and the left ventricular end-systolic elastance (Ees) is a load-independent measure of left ventricular chamber performance. Thirty-three centenarians (100.6 ± 1.2years, range 99-105years, 10M) without cardiovascular diseases underwent a complete echocardiographic evaluation and an instantaneous arterial blood pressure measurement, to characterize the Ea/Ees ratio and its two determinants indexed to body surface area. VA coupling was markedly reduced (Ea/Ees ratio 0.40 ± 0.1), reflecting a disproportionate increase in Ees index (8.5 ± 2.2mmHg/ml/m2) compared with Ea index (3.2 ± 0.8mmHg/ml/m2). Notably, the coupling ratio was significantly lower in women (0.37 ± 0.1) than in men (0.45 ± 0.1, p = 0.0003), due to an increase in Ees index significantly greater in women (9.4 ± 1.9mmHg/ml/m2) than in men (6.5 ± 1.5mmHg/ml/m2, p = 0.0002). Using multivariate regression analysis, only female gender (β coefficient -0.04, p = 0.01) and relative wall thickness (β coefficient -0.49, p < 0.0001) showed a significant inverse correlation to VA coupling. Our analysis in a population of centenarians without overt cardiovascular disease revealed very low values of VA coupling, especially in women. Both a LV structural remodeling as well as a high aortic elastance might have contributed to a secondary disproportionate increase in myocardial stiffness.

THE ROLE OF FACTORS AFFECTING THE FORMATION OF CHRONIC HEART FAILURE WITH PRESERVED EJECTION FRACTION

Aim. To study the combination and contribution of risk factors (age, hypertension (HT), obesity, diabetes mellitus, chronic kidney disease (CKD), length of illness) leading to the formation of chronic heart failure (CHF) with preserved ejection fraction (EF). Material and methods . The study included 100 hypertensive patients (aged 40 to 80 years) with concomitant obesity or diabetes or CKD. Patients were divided into 4 groups depending on the presence of one major and/or several concomitant diseases. Echocardiography, assessment of large arterial vessels stiffness indices (SI m/s, CAVI m/s), and determination of small muscle arteries tonus (RI%) were performed in all patients. Results. Remodeling of the left ventricle (LV) and left atrial (LA) was observed in all patients with comorbid status, as well as reduction in diastolic function. The LV myocardial mass index in the first group was 117.2±31.4 g/m 2 , in the second one – 125.9±27.4 g/m 2 , in the third group – 121.5±15.6 g/m 2 and in the fourth one – 126.1±11.5 g/m 2 . A significant increase in the LA volume index was founded in the first group – 33.4±3.9 ml/m 2 , in the second one – 39.6±9.1 ml/m 2 , in the third group – 38.1±5.2 ml/m 2 and in the fourth one – 39.8±6.6 ml/m 2 (р<0.05). The parameters reflecting the rigidity of large arterial vessels (SI m/s, CAVI m/s) also exceeded the threshold values in each group; significant differences SI were between the first and fourth, second and fourth groups (р<0.05), CAVI between the first and third groups (р<0.05). A significant correlation was found between CAVI and age (r=0.63), which indicated an increase in arterial stiffness with age. Conclusions. In the formation of CHF with preserved EF, additional factors enhance the changes associated with LV remodeling and LA overload. These changes occur with a progressive decrease in LV diastolic function and increase in myocardial stiffness. HT and obesity are the main contributors to the development of CHF with preserved EF. Remodeling of the LV, LA and vascular system in CHF with preserved EF develop simultaneously.

Assessment of diastolic function in the management of patients with cirrhosis.

For many years, it has been known that impaired liver function and portal hypertension are associated with a pronounced splanchnic vasodilatation. This leads to important circulatory changes with displacement of the circulating blood volume resulting in central hypovolemia [1]. The combination of effective hypovolemia, arterial hypotension, and baroreceptor-activation of potent vasoconstricting systems such as the sympathetic nervous system leads to a hyperdynamic circulation and a multi-organ failure including impaired function of the heart [2]. In a patient with a full-blown decompensated state of cirrhosis, the heart rate and cardiac output are typically increased [1]. Both experimental and clinical studies have shown that the dimensions of the cirrhotic heart are augmented and the contractility and electromechanical function are impaired [3, 4]. This condition has been termed cirrhotic cardiomyopathy, which designates a cardiac dysfunction that includes impaired cardiac contractility with systolic and diastolic dysfunction and electromechanical abnormalities in the absence of other known causes of cardiac disease [4]. Cirrhotic cardiomyopathy can be demasked by physical or pharmacological stress, which may reveal in particular a systolic dysfunction, which seems to contribute to several cirrhotic complications such as the formation of ascites [5, 6] and the development of hepatic nephropathy [7, 8]. Additionally, cirrhotic cardiomyopathy seems associated with the development of heart failure in relation to invasive procedures such as shunt insertion and liver transplantation [9, 10]. Abnormal left ventricular diastolic function, caused by decreased left ventricular compliance and relaxation, implies an abnormal filling pattern of the ventricles. The transmitral blood flow is changed, with an increased atrial contribution to the late ventricular filling [4]. The pathophysiological background of the diastolic dysfunction in cirrhosis is an increased stiffness of the myocardial wall, most likely because of a combination of mild myocardial hypertrophy, fibrosis, and subendothelial edema [2, 3]. The increase in myocardial stiffness is also reflected by other parameters of diastolic dysfunction, such as a prolonged time for the ventricles to relax after diastolic filling at a specific end-diastolic volume, which reflects an increased resistance to the ventricular inflow [4]. Natriuretic peptides are regarded as markers of volume overload and impaired contractility, and are released by stretch of the atrial fibers such as in patients with ascites where the right atrium has been reported increased partly because of volume overload with expanded blood volume [1, 4]. However, the interpretation of increased natriuretic peptides in patients who from a functional point of view suffer from effective hypovolemia is complex. Activation of the renin–angiotensin–aldosterone system (RAAS) is associated with cardiac disease such as hypertrophy and heart failure, and seems to be related to diastolic dysfunction in both cirrhotic and non-cirrhotic patients with portal hypertension [11]. Furthermore, RAAS may induce fibrosis, and there is evidence of relationships between plasma aldosterone and E/A ratio; thus, RAAS may be both directly and indirectly involved in diastolic dysfunction [4]. Echocardiography is the method more frequently utilised for the detection of left ventricular diastolic dysfunction. Diastolic dysfunction is expressed as a decreased S. Moller (&) Department of Clinical Physiology and Nuclear Medicine 239, Faculty of Health Sciences, Hvidovre Hospital, Centre of Functional Imaging and Research, University of Copenhagen, 2650 Hvidovre, Denmark e-mail: soeren.moeller@regionh.dk

Histomorphometric Analysis of Myocardial Fibrosis after Heart Transplantation

Purpose Major components of the myocardial extracellular matrix are collagen type I and type III. Furthermore, collagen type IV is located in the basement membranes. Continuous structural remodeling of the collagenous matrix results in an excessive accumulation of collagen fibrils and therefore in pathologic myocardial fibrosis. Functional consequences are related to an increase in myocardial stiffness. The phenomenon of collagen turnover in heart transplant recipients has not yet been studied. The aim of the study was to evaluate collagen type III and IV in endomyocardial biopsy specimens (EMB) after heart transplantation (HTx) and to analyze the prognostic value of immunohistochemistry staining compared to the Sirius-red staining of fibrosis used routinely. Methods and Materials In total, 274 EMB of 77 patients who underwent HTx between 2003 and 2006 (66 men, mean age at HTx 49 years) were evaluated on the date of HTx=FU0, and 4 weeks=FU1, 1 year=FU2, 3 years=FU3 and 5 years=FU4 post-HTX. Computer-based histomorphometrical analyses were compared. The rates of collagen III and IV and myocardial fibrosis were measured in an area of 1mm2 for each EMB. Results The rate of collagen III increased continuously, while fibrosis demonstrated a fluctuating course (FU0: 13.0 vs 8.59%, FU1: 11.94 vs 7.87%, FU2: 12.0 vs 8.47%, FU3: 12.19 vs 6.95%, FU4: 16.17 vs 7.9%, p 20%) was associated with more fibrosis (10-19.9%, FU2: p=0.02, FU4: p Conclusions The rate of collagen III and IV increases significantly more than the rate of fibrosis in the long term post-HTx. The consequences of the collagenous remodeling for the contractile functionality of the myocardium of HTx recipients remain unclear and need to be evaluated.

Substrate Stiffness Increases Twitch Power of Neonatal Cardiomyocytes in Correlation with Changes in Myofibril Structure and Intracellular Calcium

During neonatal development, there is an increase in myocardial stiffness that coincides with an increase in the contractility of the heart. In vitro assays have shown that substrate stiffness plays a role in regulating the twitch forces produced by immature cardiomyocytes. However, its effect on twitch power is unclear due to difficulties in measuring the twitch velocity of cardiomyocytes. Here, we introduce what we consider a novel approach to quantify twitch power by combining the temporal resolution of optical line scanning with the subcellular force resolution of micropost arrays. Using this approach, twitch power was found to be greater for cells cultured on stiffer posts, despite having lower twitch velocities. The increased power was attributed in part to improved myofibril structure (increased sarcomere length and Z-band width) and intracellular calcium levels. Immunofluorescent staining of α-actin revealed that cardiomyocytes had greater sarcomere length and Z-band width when cultured on stiffer arrays. Moreover, the concentration of intracellular calcium at rest and its rise with each twitch contraction was greater for cells on the stiffer posts. Altogether, these findings indicate that cardiomyocytes respond to substrate stiffness with biomechanical and biochemical changes that lead to an increase in cardiac contractility.

Diastolic function during hemorrhagic shock in rabbits

Hemorrhage (H) is associated with a left ventricular (LV) dysfunction. However, the diastolic function has not been studied in detail. The main goal was to assess the diastolic function both during and 120min after bleeding, in the absence and in the presence of L-NAME. Also, the changes in mRNA and protein expression of nitric oxide synthase (NOS) isoforms were determined. New Zealand rabbits were divided into three groups: Sham group, H group (hemorrhage 20% blood volume), and H L-NAME group (hemorrhage treated with L-NAME). We evaluated systolic and diastolic ventricular functions in vivo and in vitro (Langendorff technique). Hemodynamic parameters and LV function were measured before, during, and at 120min after bleeding. We analyzed the isovolumic relaxation using t ½ in vivo (closed chest). After that, hearts were excised and perfused in vitro to measure myocardial stiffness. Samples were frozen to measure NOS mRNA and protein expression. The t½ increased during bleeding and returned to basal values 120min after bleeding. L-NAME blunted this effect. Data from the H group revealed a shift to the left in the LV end diastolic pressure-volume curve at 120min after bleeding, which was blocked by L-NAME. iNOS and nNOS protein expression and mRNA levels increased at 120min after the hemorrhage. Acute hemorrhage induces early and transient isovolumic relaxation impairment and an increase in myocardial stiffness 120min after bleeding. L-NAME blunted the LV dysfunction, suggesting that NO modulates ventricular function through iNOS and nNOS isoforms.

Increased myocardial stiffness with maintenance of length-dependent calcium activation by female sex hormones in diabetic rats

A decrease in peak early diastolic filling velocity in postmenopausal women implies a sex hormone-related diastolic dysfunction. The regulatory effect of female sex hormones on cardiac distensibility therefore was evaluated in ovariectomized rats by determining the sarcomere length-passive tension relationship of ventricular skinned fiber preparations. Diabetes also was induced in the rat to assess the protective significance of female sex hormones on diastolic function. While ovariectomy had no effect on myocardial stiffness, collagen content, or titin ratio, a significant increase in myocardial stiffness was observed in diabetic rat only when female sex hormones were intact. The increased stiffness in diabetic-sham rats was accompanied by an elevated collagen content resulting from increases in the levels of procollagen and Smad2. Surprisingly, the increased myocardial stiffness in diabetic-sham rats was accompanied by a shift toward a more compliant N2BA of cardiac titin isoforms. The pCa-active tension relationship was analyzed at fixed sarcomere lengths of 2.0 and 2.3 μm to determine the magnitude of changes in myofilament Ca(2+) sensitivity between the two sarcomere lengths. Interestingly, high expression of N2BA titin was associated with a suppressed magnitude of changes in myofilament Ca(2+) sensitivity only in the diabetic-ovariectomized condition. Estrogen supplementation in diabetic-ovariectomized rats partially increased myocardial stiffness but completely reversed the change in myofilament Ca(2+) sensitivity. These results indicate a restrictive adaptation of myocardium governed by female sex hormones to maintain myofilament activity in compensation to the pathophysiological induction of cardiac dilatation by the diabetic condition.

Characterization of Titin Following Transverse Aortic Constriction in Mice

Heart Failure is characterized by an impaired ability of the left ventricle to fill or eject blood and is typically accompanied with cardiac hypertrophy. Furthermore, sustained cardiac hypertrophy transitions into maladaptive hypertrophy, with left ventricular dilation, decrease contractile properties, increased myocardial stiffness (through alterations in titin and collagen), and reduced cardiac output. The current aim was to investigate alterations in heart function, titin isoform shifts, and myocardial stiffness following transverse aortic constriction-induced heart failure in mouse. Echocardiology showed increased aortic velocity (0.5 vs 4.5m/s), diastolic (55 vs 90ul) and systolic (20 vs 53ul) ventricular volume, LV mass (133 vs 220mg) and decreased ejection fraction (65% vs 35%) and mitral valve deceleration time (23 vs 18ms) (indicating a significant increase in myocardial stiffness). Additionally, E/A ratios dramatically increased from 1.5 to 5, signifying extensive heart failure. In order to further characterize myocardial stiffness, skinned LV muscle bundle fibers were mechanically stretched and titin and collagen forces were measured. At sarcomere length 2.15, data showed an increase in total passive tension (35%), total collagen force (120%), and total titin force (15%). Protein gels were ran to help identify the source of increased titin tension. Gels showed an increase in the long N2BA as related to the short N2B titin isoform (0.20 vs 0.37) indicating that titin passive tension should actually decrease, not increase. However, western blots using phospho-specific antibodies for titin's S11878 and S12022 (phosphorylated by PKCα resulting in increased passive tension) indicate a 2.5 fold increase in phosphorylation in the end-stage heart failure mice. In conclusion, TAC-induced heart failure in mice resulted in an increased diastolic stiffness partially through PKCα phosphorylation-mediated increases in titin-based tension.

Cardiac remodeling in a rat model of diet-induced obesity

The mechanisms by which diet-induced obesity cause remodeling and cardiac dysfunction are still unknown. Interstitial collagen and myocardial ultrastructure are important in the development of left ventricular hypertrophy, and are essential to the adaptive and maladaptive changes associated with obesity. Thus, the accumulation of collagen and ultrastructural damage may contribute to cardiac dysfunction in obesity. The purpose of the present study was to investigate cardiac function in a rat model of diet-induced obesity and to test the hypothesis that cardiac dysfunction induced by obesity is related to myocardial collagen deposition and ultrastructural damage. Thirty-day-old male Wistar rats were fed standard (control [C]) and hypercaloric diets (obese [Ob]) for 15 weeks. Cardiac function was evaluated by echocardiogram and isolated left ventricle papillary muscle. Cardiac morphology was assessed by histology and electron microscopy. Compared with C rats, Ob rats had increased body fat, systolic blood pressure and area under the curve for glucose, leptin and insulin plasma concentrations. Echocardiographic indexes indicated that Ob rats had increased left ventricular mass, increased systolic stress and depressed systolic function. Analysis of the isolated papillary muscle was consistent with higher myocardial stiffness in Ob compared with C rats. The Ob rats had an increase in myocardial collagen and marked ultrastructural changes compared with C rats. Obesity promotes pathological cardiac remodeling with systolic dysfunction and an increase in myocardial stiffness, which, in turn, is probably related to afterload elevation and cardiac fibrosis. Obesity also causes damage to myocardial ultrastructure, but its effect on myocardial function needs to be further clarified.