Relaxation and the Role of Calcium in Isolated Contracting Myocardium From Patients With Hypertensive Heart Disease and Heart Failure With Preserved Ejection Fraction

Clinical, Echocardiographic, and Longitudinal Characteristics Associated With Heart Failure With Improved Ejection Fraction

Heart failure with improved ejection fraction (HFimpEF) has better outcomes than HF with reduced EF (HFrEF). However, factors contributing to HFimpEF remain unclear. This study aimed to evaluate clinical and longitudinal characteristics associated with subsequent HFimpEF. This was a single-center retrospective HFrEF cohort study. Data were collected from 2014 to 2022. Patients with HFrEF were identified using International Classification of Diseases codes, echocardiographic data, and natriuretic peptide levels. The main end points were HFimpEF (defined as EF >40% at ≥3 months with ≥10% increase) and mortality. Cox proportional hazards and mixed effects models were used for analyses. The study included 1,307 patients with HFrEF with a median follow-up of 16.3 months (interquartile range 8.0 to 30.6). The median age was 65 years; 68% were male whereas 57% were White. On follow-up, 38.7% (n = 506) developed HFimpEF, whereas 61.3% (n = 801) had persistent HFrEF. A multivariate Cox regression model identified gender, race, co-morbidities, echocardiographic, and natriuretic peptide as significant covariates of HFimpEF (p <0.05). The HFimpEF group had better survival compared with the persistent HFrEF group (p <0.001). Echocardiographic and laboratory trajectories differed between groups. In this HFrEF cohort, 38.7% transitioned to HFimpEF and approximately 50% met the definition within the first 12 months. In a HFimpEF model, gender, co-morbidities, echocardiographic parameters, and natriuretic peptide were associated with subsequent HFimpEF. The model has the potential to identify patients at risk of subsequent persistent or improved HFrEF, thus informing the design and implementation of targeted quality-of-care improvement interventions.

Effects of Continuous Accelerated Pacing on Cardiac Structure and Function in Patients With Heart Failure With Preserved Ejection Fraction: Insights From the myPACE Randomized Clinical Trial

BACKGROUND

Heart failure with preserved ejection fraction ≥50% is prevalent with few evidence-based therapies. In a trial of patients with heart failure with preserved ejection fraction with specialized pacemakers, treatment with accelerated personalized pacing averaging 75 bpm (myPACE) markedly improved quality of life, NT-proBNP (N-terminal pro-brain natriuretic peptide), physical activity, and atrial fibrillation burden compared with the standard lower rate setting of 60 bpm (usual care).

METHODS AND RESULTS

In this exploratory study, provider-initiated echocardiographic studies obtained before and after the trial were assessed for changes in left ventricular (LV) structure and function among participants who continued their pacing assignment. The analytic approach aimed to detect differences in standard and advanced echocardiographic parameters within and between study arms. Of the 100 participants, 16 myPACE and 20 usual care arm had a qualifying set of echocardiograms performed a mean (SD) 3 (2.0) years apart. Despite similar baseline echocardiogram measures, sustained exposure to moderately accelerated pacing resulted in reduced septal wall thickness (in cm: myPACE 1.1 [0.2] versus usual care 1.2 [0.2], P=0.008) and lower LV mass to systolic volume ratio (in g/mL: myPACE 4.8 [1.9] versus usual care 6.8 [3.1], P=0.038) accompanied by a minor reduction in LV ejection fraction (in %: myPACE 55 [5] versus usual care 60 [5], P=0.015). These changes were paralleled by improvements in heart failure-related quality of life (myPACE Minnesota Living with Heart Failure Questionnaire improved by 16.1 [13.9] points, whereas usual care worsened by 6.9 [11.6] points, P<0.001). Markers of diastolic function and LV performance were not affected.

CONCLUSIONS

Exposure to continuous accelerated pacing in heart failure with preserved ejection fraction is associated with a reduced LV wall thickness and a small amount of LV dilation with small reduction in ejection fraction.

Rationale and design of the PACE HFpEF trial: Physiologic accelerated pacing as a holistic treatment of heart failure with preserved ejection fraction

Background

In heart failure with preserved ejection fraction (HFpEF), it has been assumed that pharmacologic heart rate suppression should provide clinical benefits through an increase in diastolic filling time. Contrary to this assumption, heart rate lowering in patients with preserved left ventricular ejection fraction and hypertension or coronary artery disease results in adverse outcomes and suggests that the opposite may be beneficial. Namely, shortening the diastolic filling time with a higher heart rate might normalize the elevated filling pressures that are the sine qua non of HFpEF. Initial clinical studies that assessed the effects of accelerated heart rates in pacemaker patients with preclinical and overt HFpEF provide support for this latter hypothesis, having shown improvements in quality of life, natriuretic peptide and activity levels, and atrial fibrillation burden.

Objective

The study sought to determine the effects of continued resting heart rate elevation with and without superimposed nocturnal pacing in HFpEF patients without standard pacing indication.

Methods

The physiologic accelerated pacing as treatment for heart failure with preserved ejection fraction (PACE HFpEF) trial is an investigator-initiated, prospective, patient-blinded multiple crossover pilot study that assesses the impact of accelerated pacing on quality of life, physical activity, N-terminal pro-B-type natriuretic peptide, and echocardiographic measures of cardiac structure and function.

Results

Twenty patients were enrolled and underwent dual-chamber pacemaker implantation under U.S. Food and Drug Administration investigational device exemption with both atrial and ventricular physiologic lead placement targeting the Bachmann bundle and the His bundle.

Conclusion

This manuscript describes the rationale and design of the PACE HFpEF trial, which tests the safety and feasibility of continuous accelerated physiological pacing as a treatment strategy in HFpEF.

The Role of Ranolazine in Heart Failure-Current Concepts

Heart failure is a complex clinical syndrome with a detrimental impact on mortality and morbidity. Energy substrate utilization and myocardial ion channel regulation have gained research interest especially after the introduction of sodium-glucose co-transporter 2 inhibitors in the treatment of heart failure. Ranolazine or N-(2,6-dimethylphenyl)-2-(4-[2-hydroxy-3-(2-methoxyphenoxy) propyl] piperazin-1-yl) acetamide hydrochloride is an active piperazine derivative which inhibits late sodium current thus minimizing calcium overload in the ischemic cardiomyocytes. Ranolazine also prevents fatty acid oxidation and favors glycose utilization ameliorating the "energy starvation" of the failing heart. Heart failure with preserved ejection fraction is characterized by diastolic impairment; according to the literature ranolazine could be beneficial in the management of increased left ventricular end-diastolic pressure, right ventricular systolic dysfunction and wall shear stress which is reflected by the high natriuretic peptides. Fewer data is evident regarding the effects of ranolazine in heart failure with reduced ejection fraction and mainly support the control of the sodium-calcium exchanger and function of sarcoendoplasmic reticulum calcium adenosine triphosphatase. Ranolazine's therapeutic mechanisms in myocardial ion channels and energy utilization are documented in patients with chronic coronary syndromes. Nevertheless, ranolazine might have a broader effect in the therapy of heart failure and further mechanistic research is required.

Personalized accelerated physiologic pacing

Heart failure with preserved ejection fraction (HFpEF) is increasingly prevalent with a high socioeconomic burden. Pharmacological heart rate lowering was recommended to improve ventricular filling in HFpEF. This article discusses the misperceptions that have resulted in an overprescription of beta-blockers, which in all likelihood have untoward effects on patients with HFpEF, even if they have atrial fibrillation or coronary artery disease as a comorbidity. Directly contradicting the lower heart rate paradigm, faster heart rates provide haemodynamic and structural benefits, amongst which lower cardiac filling pressures and improved ventricular capacitance may be most important. Safe delivery of this therapeutic approach is feasible with atrial and ventricular conduction system pacing that aims to emulate or enhance cardiac excitation to maximize the haemodynamic benefits of accelerated pacing. This conceptual framework was first tested in the myPACE randomized controlled trial of patients with pre-existing pacemakers and preclinical or overt HFpEF. This article provides the background and path towards this treatment approach.

Literature Review: Pathophysiology of Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction is a growing public health concern, a disease with poor health outcomes, and is showing increased prevalence globally. This review paper explores the literature with a focus on the pathophysiology and microbiology of preserved ejection fraction heart failure while drawing connections between preserved and reduced ejection fraction states. The discussion teases out the cellular level changes that affect the overall dysfunction of the cardiac tissue, including the clinical manifestations, microbiological changes (endothelial cells, fibroblasts, cardiomyocytes, and excitation-contraction coupling), and the burden of structural diastolic dysfunction. The goal of this review is to summarize the pathophysiological disease state of heart failure with preserved ejection fraction to enhance understanding, knowledge, current treatment models of this pathology.

Clinical, Echocardiographic, and Longitudinal Characteristics Associated with Heart Failure with Improved Ejection Fraction

Background

Heart failure (HF) with improved ejection fraction (HFimpEF) has better outcomes than HF with reduced ejection fraction (HFrEF). However, factors contributing to HFimpEF remain unclear. This study aimed to evaluate clinical and longitudinal characteristics associated with subsequent HFimpEF.

Methods

This was a single-center retrospective HFrEF cohort study. Data were collected from 2014 to 2022. Patients with HFrEF were identified using ICD codes, echocardiographic data, and natriuretic peptide levels. The main endpoints were HFimpEF (defined as ejection fraction >40% at ≥3 months with ≥10% increase) and mortality. Cox proportional hazards and mixed effects models were used for analyses.

Results

The study included 1307 HFrEF patients with a median follow-up of 16.3 months (IQR 8.0-30.6). The median age was 65 years; 68% were male while 57% were white. On follow-up, 39% (n=506) developed HFimpEF, while 61% (n=801) had persistent HFrEF. A multivariate Cox regression model identified sex, race comorbidities, echocardiographic, and natriuretic peptide as significant covariates of HFimpEF ( p <0.05). The HFimpEF group had better survival compared to the persistent HFrEF group ( p <0.001). Echocardiographic and laboratory trajectories differed between groups.

Conclusion

In this HFrEF cohort, 39% transitioned to HFimpEF and approximately 50% met the definition within the first 12 months. In a HFimpEF model, sex, comorbidities, echocardiographic parameters, and natriuretic peptide were associated with subsequent HFimpEF. The model has the potential to identify patients at risk of subsequent persistent or improved HFrEF, thus informing the design and implementation of targeted quality-of-care improvement interventions.

Cardiomyocyte Damage: Ferroptosis Relation to Ischemia-Reperfusion Injury and Future Treatment Options

About half a century ago, Eugene Braunwald, a father of modern cardiology, shared a revolutionary belief that "time is muscle", which predetermined never-ending effort to preserve the unaffected myocardium. In connection to that, researchers are constantly trying to better comprehend the ongoing changes of the ischemic myocardium. As the latest studies show, metabolic changes after acute myocardial infarction (AMI) are inconsistent and depend on many constituents, which leads to many limitations and lack of unification. Nevertheless, one of the promising novel mechanistic approaches related to iron metabolism now plays an invaluable role in the ischemic heart research field. The heart, because of its high levels of oxygen consumption, is one of the most susceptible organs to iron-induced damage. In the past few years, a relatively new form of programmed cell death, called ferroptosis, has been gaining much attention in the context of myocardial infarction. This review will try to summarize the main novel metabolic pathways and show the pivotal limitations of the affected myocardium metabolomics.

Left Ventricular Gene Expression in Heart Failure With Preserved Ejection Fraction-Profibrotic and Proinflammatory Pathways and Genes

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is increasingly prevalent and has few treatments. The molecular mechanisms and resultant signaling pathways that underlie the development of HFpEF are poorly defined. It has been proposed that activation of proinflammatory pathways plays a role in the development of cardiac fibrosis. The signature of gene expression (transcriptome) of previously validated left ventricular biopsies obtained from patients with HFpEF and matched referent controls allows for an unbiased assessment of proinflammatory and profibrotic signaling pathways and genes.

METHODS

Epicardial left ventricular biopsies from stringently selected HFpEF patients (HFpEF, n=16) and referent control patients (CTR, n=14) were obtained during aortocoronary bypass surgery. The subepicardial myocardium was flash-frozen to build a repository that was parallel-processed for RNA sequencing to allow for an unsupervised in-depth comparison of the left ventricular transcriptome.

RESULTS

The average patient age was 67±10 years. When compared with controls, patients with HFpEF were hypertensive with a higher body mass index (kg/m2: 30±5 versus 37±6; P<0.01) and elevated NT-proBNP levels (pg/mL: 155 [89-328] versus 1554 [888-2178]; P<0.001). The transcriptome analysis revealed differential expression of 477 genes many of which were involved in profibrotic pathways including extracellular matrix production and posttranslational modification but no proinflammatory signature.

CONCLUSIONS

The transcriptome analysis of left ventricular myocardial samples from patients with HFpEF confirms an overabundant extracellular matrix gene expression, the basis of myocardial fibrosis, without a signature of activated proinflammatory pathways or genes.

Lower heart rates and beta-blockers are associated with new-onset atrial fibrillation

Background

Lower heart rates (HRs) prolong diastole, which increases filling pressures and wall stress. As a result, lower HRs may be associated with higher brain natriuretic peptide (BNP) levels and incident atrial fibrillation (AF). Beta-blockers may increase the risk for AF due to suppression of resting HRs.

Objective

Examine the relationships of HR, BNP, beta-blockers and new-onset AF in the REVEAL-AF and SPRINT cohort of subjects at risk for developing AF.

Methods

In REVEAL-AF, 383 subjects without a history of AF and a mean CHA₂DS₂VASC score of 4.4 ± 1.3 received an insertable cardiac monitor and were followed up to 30 months. In SPRINT, 7595 patients without prior history of AF and a mean CHA₂DS₂VASC score of 2.3 ± 1.2 were followed up to 60 months.

Results

The median daytime HR in the REVEAL-AF cohort was 75bpm [IQR 68-83]. Subjects with below-median HRs had 2.4-fold higher BNP levels compared to subjects with above-median HRs (median BNP [IQR]: 62 pg/dl [37-112] vs. 26 pg/dl [13-53], p < 0.001). HRs <75bpm were associated with a higher incidence of AF: 37% vs. 27%, p < 0.05. This was validated in the SPRINT cohort after adjusting for AF risk factors. Both a HR < 75bpm and beta-blocker use were associated with a higher rate of AF: 1.9 vs 0.7% (p < 0.001) and 2.5% vs. 0.6% (p < 0.001), respectively. The hazard ratio for patients on beta-blockers to develop AF was 3.72 [CI 2.32, 5.96], p < 0.001.

Conclusions

Lower HRs are associated with higher BNP levels and incident AF, mimicking the hemodynamic effects of diastolic dysfunction. Suppression of resting HR by beta-blockers could explain their association with incident AF.

Cardiac contractility modulation: an effective treatment strategy for heart failure beyond reduced left ventricular ejection fraction?

Heart failure (HF) with preserved ejection fraction (HFpEF) causes a progressive limitation of functional capacity, poor quality of life (QoL) and increased mortality, yet unlike HF with reduced ejection fraction (HFrEF) there are no effective device-based therapies. Both HFrEF and HFpEF are associated with dysregulations in myocardial cellular calcium homeostasis and modifications in calcium-handling proteins, leading to abnormal myocardial contractility and pathological remodelling. Cardiac contractility modulation (CCM) therapy, based on a pacemaker-like implanted device, applies extracellular electrical stimulation to myocytes during the absolute refractory period of the action potential, which leads to an increase in cytosolic peak calcium concentrations and thereby the force of isometric contraction promoting positive inotropism. Subgroup analysis of CCM trials in HFrEF has demonstrated particular benefits in patients with LVEF between 35% and 45%, suggesting its potential effectiveness also in patients with higher LVEF values. Available evidence on CCM in HFpEF is still preliminary, but improvements in terms of symptoms and QoL have been observed. Future large, dedicated, prospective studies are needed to evaluate the safety and efficacy of this therapy in patients with HFpEF.

Myocardial Metabolomics of Human Heart Failure With Preserved Ejection Fraction

BACKGROUND

The human heart primarily metabolizes fatty acids, and this decreases as alternative fuel use rises in heart failure with reduced ejection fraction (HFrEF). Patients with severe obesity and diabetes are thought to have increased myocardial fatty acid metabolism, but whether this is found in those who also have heart failure with preserved ejection fraction (HFpEF) is unknown.

METHODS

Plasma and endomyocardial biopsies were obtained from HFpEF (n=38), HFrEF (n=30), and nonfailing donor controls (n=20). Quantitative targeted metabolomics measured organic acids, amino acids, and acylcarnitines in myocardium (72 metabolites) and plasma (69 metabolites). The results were integrated with reported RNA sequencing data. Metabolomics were analyzed using agnostic clustering tools, Kruskal-Wallis test with Dunn test, and machine learning.

RESULTS

Agnostic clustering of myocardial but not plasma metabolites separated disease groups. Despite more obesity and diabetes in HFpEF versus HFrEF (body mass index, 39.8 kg/m2 versus 26.1 kg/m2; diabetes, 70% versus 30%; both P<0.0001), medium- and long-chain acylcarnitines (mostly metabolites of fatty acid oxidation) were markedly lower in myocardium from both heart failure groups versus control. In contrast, plasma levels were no different or higher than control. Gene expression linked to fatty acid metabolism was generally lower in HFpEF versus control. Myocardial pyruvate was higher in HFpEF whereas the tricarboxylic acid cycle intermediates succinate and fumarate were lower, as were several genes controlling glucose metabolism. Non-branched-chain and branched-chain amino acids (BCAA) were highest in HFpEF myocardium, yet downstream BCAA metabolites and genes controlling BCAA metabolism were lower. Ketone levels were higher in myocardium and plasma of patients with HFrEF but not HFpEF. HFpEF metabolomic-derived subgroups were differentiated by only a few differences in BCAA metabolites.

CONCLUSIONS

Despite marked obesity and diabetes, HFpEF myocardium exhibited lower fatty acid metabolites compared with HFrEF. Ketones and metabolites of the tricarboxylic acid cycle and BCAA were also lower in HFpEF, suggesting insufficient use of alternative fuels. These differences were not detectable in plasma and challenge conventional views of myocardial fuel use in HFpEF with marked diabetes and obesity and suggest substantial fuel inflexibility in this syndrome.

Thyroid Hormone and Heart Failure: Charting Known Pathways for Cardiac Repair/Regeneration

Heart failure affects more than 64 million people worldwide, having a serious impact on their survival and quality of life. Exploring its pathophysiology and molecular bases is an urgent need in order to develop new therapeutic approaches. Thyroid hormone signaling, evolutionarily conserved, controls fundamental biological processes and has a crucial role in development and metabolism. Its active form is L-triiodothyronine, which not only regulates important gene expression by binding to its nuclear receptors, but also has nongenomic actions, controlling crucial intracellular signalings. Stressful stimuli, such as acute myocardial infarction, lead to changes in thyroid hormone signaling, and especially in the relation of the thyroid hormone and its nuclear receptor, which are associated with the reactivation of fetal development programmes, with structural remodeling and phenotypical changes in the cardiomyocytes. The recapitulation of fetal-like features of the signaling may be partially an incomplete effort of the myocardium to recapitulate its developmental program and enable cardiomyocytes to proliferate and finally to regenerate. In this review, we will discuss the experimental and clinical evidence about the role of the thyroid hormone in the recovery of the myocardium in the setting of heart failure with reduced and preserved ejection fraction and its future therapeutic implications.

[Mechano-energetic defects in heart failure]

Heart failure is characterized by defects in excitation-contraction coupling, energetic deficit and oxidative stress. The energy for cardiac contraction and relaxation is provided in mitochondria, whose function is tightly regulated by excitation-contraction coupling in cardiac myocytes. In heart failure with reduced ejection fraction (HFrEF), alterations in the ion balance in cardiac myocytes impair mitochondrial Ca²⁺ uptake, which is required for activation of the Krebs cycle, causing an energetic deficit and oxidative stress in mitochondria. Recent clinical studies suggest that in heart failure with preserved ejection fraction (HFpEF), in stark contrast to HFrEF, hypercontractility often occurs as an attempt to compensate for a pathological increase in systemic and pulmonary vascular resistance. This hypercontractility increases cardiac energy and oxygen demands at rest and reduces the contractile, diastolic and coronary reserves, preventing an adequate increase in cardiac output during exercise. Moreover, increased contractility causes long-term maladaptive remodeling processes due to oxidative stress and redox-sensitive prohypertrophic signaling pathways. As overweight and diabetes, particularly in the interplay with hemodynamic stress, are important risk factors for the development of HFpEF, interventions targeting metabolism in particular could ameliorate the development and progression of HFpEF.

Challenging the Hemodynamic Hypothesis in Heart Failure With Preserved Ejection Fraction: Is Exercise Capacity Limited by Elevated Pulmonary Capillary Wedge Pressure?

BACKGROUND

Exercise intolerance is a defining characteristic of heart failure with preserved ejection fraction (HFpEF). A marked rise in pulmonary capillary wedge pressure (PCWP) during exertion is pathognomonic for HFpEF and is thought to be a key cause of exercise intolerance. If true, acutely lowering PCWP should improve exercise capacity. To test this hypothesis, we evaluated peak exercise capacity with and without nitroglycerin to acutely lower PCWP during exercise in patients with HFpEF.

METHODS

Thirty patients with HFpEF (70±6 years of age; 63% female) underwent 2 bouts of upright, seated cycle exercise dosed with sublingual nitroglycerin or placebo control every 15 minutes in a single-blind, randomized, crossover design. PCWP (right heart catheterization), oxygen uptake (breath × breath gas exchange), and cardiac output (direct Fick) were assessed at rest, 20 Watts (W), and peak exercise during both placebo and nitroglycerin conditions.

RESULTS

PCWP increased from 8±4 to 35±9 mm Hg from rest to peak exercise with placebo. With nitroglycerin, there was a graded decrease in PCWP compared with placebo at rest (-1±2 mm Hg), 20W (-5±5 mm Hg), and peak exercise (-7±6 mm Hg; drug × exercise stage P=0.004). Nitroglycerin did not affect oxygen uptake at rest, 20W, or peak (placebo, 1.34±0.48 versus nitroglycerin, 1.32±0.46 L/min; drug × exercise P=0.984). Compared with placebo, nitroglycerin lowered stroke volume at rest (-8±13 mL) and 20W (-7±11 mL), but not peak exercise (0±10 mL).

CONCLUSIONS

Sublingual nitroglycerin lowered PCWP during submaximal and maximal exercise. Despite reduction in PCWP, peak oxygen uptake was not changed. These results suggest that acute reductions in PCWP are insufficient to improve exercise capacity, and further argue that high PCWP during exercise is not by itself a limiting factor for exercise performance in patients with HFpEF.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT04068844.

Correlation between serum levels of microRNA-21 and inflammatory factors in patients with chronic heart failure

As the leading cause of hospitalization and mortality worldwide, heart failure (HF) has caused significant burden on both individuals and the whole society. Thus, increasing knowledge about the phytopathology of HF is in demand for both diagnosis and treatment. Previous studies have shown that both microRNA 21 (miRNA-21) and inflammatory factors are closely related to the development of cardiac fibrosis, hypertrophy, and HF. However, whether there is any crosstalk between the 2 has not been examined. The current study evaluated the correlation between serum levels of miRNA-21 and critical inflammatory factors during the progress of chronic heart failure (CHF), providing new insights in understanding the physiopathology of CHF and identifying CHF biomarkers. In the presented study, serum level of miR-21, cardiac neurohormone, and critical inflammatory factors were measured and compared on 120 (67 male/53 female) CHF patients and 100 (58 male/42 female) health people with non-failing hearts. Echocardiography was also conducted to assess the severity of CHF. Correlations between different factors were calculated and tested for statistical significance. From our results, CHF patients showed significantly decreased serum levels of miR-21 while increased levels of inflammatory factors and cardiac neurohormone (P < .05). Levels of miR-21 negatively correlate with cardiac function while positively correlates with myocardial remodeling (P < .05). Levels of miR-21 negatively correlate with inflammation in CHF (P < .05). These findings indicate the potential crosstalk between serum miR-21 and inflammation during CHF progression, suggesting the potential of miR-21 in CHF diagnosis, severity indication, and treatment.

Ferroptosis: The Potential Target in Heart Failure with Preserved Ejection Fraction

Ferroptosis is a recently identified cell death characterized by an excessive accumulation of iron-dependent reactive oxygen species (ROS) and lipid peroxides. Intracellular iron overload can not only cause damage to macrophages, endothelial cells, and cardiomyocytes through responses such as lipid peroxidation, oxidative stress, and inflammation, but can also affect cardiomyocyte Ca²⁺ handling, impair excitation–contraction coupling, and play an important role in the pathological process of heart failure with preserved ejection fraction (HFpEF). However, the mechanisms through which ferroptosis initiates the development and progression of HFpEF have not been established. This review explains the possible correlations between HFpEF and ferroptosis and provides a reliable theoretical basis for future studies on its mechanism.

Inorganic phosphate accelerates cardiac myofilament relaxation in response to lengthening

Myocardial relaxation in late systole is enhanced by increasing velocities of lengthening. Given that inorganic phosphate (Pi) can rebind to the force-producing myosin enzyme prior to MgADP release and hasten crossbridge detachment, we hypothesized that myocardial relaxation in late systole would be further enhanced by lengthening in the presence of Pi. Wistar rat left ventricular papillary muscles were attached to platinum clips, placed between a force transducer and a length motor at room temperature, and bathed in Krebs solution with 1.8 mM Ca²⁺ and varying Pi of 0, 1, 2, and 5 mM. Tension transients were elicited by electrical stimulation at 1 Hz. Peak tension was significantly enhanced by Pi: 0.593 ± 0.088 mN mm⁻² at 0 mM Pi and 0.817 ± 0.159 mN mm⁻² at 5 mM Pi (mean ± SEM, p < 0.01 by ANCOVA). All temporal characteristics of the force transient were significantly shortened with increasing Pi, e.g., time-to-50% recovery was shortened from 305 ± 14 ms at 0 mM Pi to 256 ± 10 ms at 5 mM Pi (p < 0.01). A 1% lengthening stretch with varying duration of 10–200 ms was applied at time-to-50% recovery during the descending phase of the force transient. Matching lengthening stretches were also applied when the muscle was not stimulated, thus providing a control for the passive viscoelastic response. After subtracting the passive from the active force response, the resulting myofilament response demonstrated features of faster myofilament relaxation in response to the stretch. For example, time-to-70% relaxation with 100 ms lengthening duration was shortened by 8.8 ± 6.8 ms at 0 Pi, 19.6 ± 4.8* ms at 1 mM Pi, 31.0 ± 5.6* ms at 2 Pi, and 25.6 ± 5.3* ms at 5 mM Pi (*p < 0.01 compared to no change). Using skinned myocardium, half maximally calcium-activated myofilaments underwent a 1% quick stretch, and the tension response was subjected to analysis for sensitivity of myosin detachment rate to stretch, g₁, at various Pi concentrations. The parameter g₁ was enhanced from 15.39 ± 0.35 at 0 Pi to 22.74 ± 1.31 s⁻¹/nm at 8 Pi (p < 0.01). Our findings suggest that increasing Pi at the myofilaments enhances lengthening-induced relaxation by elevating the sensitivity of myosin crossbridge detachment due to lengthening and thus speed the transition from late-systole to early-diastole.

Heart rate changes and myocardial sodium

Historic studies with sodium ion (Na+ ) micropipettes and first-generation fluorescent probes suggested that an increase in heart rate results in higher intracellular Na+ -levels. Using a dual fluorescence indicator approach, we simultaneously assessed the dynamic changes in intracellular Na+ and calcium (Ca2+ ) with measures of force development in isolated excitable myocardial strip preparations from rat and human left ventricular myocardium at different stimulation rates and modeled the Na+ -effects on the sodium-calcium exchanger (NCX). To gain further insight into the effects of heart rate on intracellular Na+ -regulation and sodium/potassium ATPase (NKA) function, Na+ , and potassium ion (K+ ) levels were assessed in the coronary effluent (CE) of paced human subjects. Increasing the stimulation rate from 60/min to 180/min led to a transient Na+ -peak followed by a lower Na+ -level, whereas the return to 60/min had the opposite effect leading to a transient Na+ -trough followed by a higher Na+ -level. The presence of the Na+ -peak and trough suggests a delayed regulation of NKA activity in response to changes in heart rate. This was clinically confirmed in the pacing study where CE-K+ levels were raised above steady-state levels with rapid pacing and reduced after pacing cessation. Despite an initial Na+ peak that is due to a delayed increase in NKA activity, an increase in heart rate was associated with lower, and not higher, Na+ -levels in the myocardium. The dynamic changes in Na+ unveil the adaptive role of NKA to maintain Na+ and K+ -gradients that preserve membrane potential and cellular Ca2+ -hemostasis.

Diastolic Filling Time, Chronotropic Response, and Exercise Capacity in Heart Failure and Preserved Ejection Fraction With Sinus Rhythm

Background

Exercise‐induced high heart rate may impair exercise tolerance by reducing diastolic filling time and ventricular filling in heart failure with preserved ejection fraction (HFpEF). Given the importance of chronotropic response, we hypothesized that reduction in diastolic filling time because of exercise‐induced increased heart rate would not impair cardiac output reserve and exercise capacity. We sought to determine the association between heart rate, diastolic filling time, hemodynamics, and exercise capacity in HFpEF.

Methods and Results

Patients with HFpEF (n=66) and controls without HF (n=107) underwent bicycle exercise echocardiography with simultaneous expired gas analysis to measure oxygen consumption. Diastolic filling time was assessed by the overlap time between mitral E‐ and A‐waves (longer overlap time indicates shorter diastolic filling duration). Overlap time increased (ie, diastolic filling time shortened) in HFpEF and controls as heart rate increased with exercise, and the relationship was similar between the groups. Greater heart rate response correlated with higher cardiac output (r=0.51, P<0.0001) and oxygen consumption (r=0.50, P<0.0001) during peak exercise. Shorter diastolic filling time, as assessed by longer overlap time, was correlated with higher cardiac output (r=0.47, P<0.0001) and peak oxygen consumption (r=0.38, P=0.007), not with E/e′ or right ventricular‐pulmonary artery uncoupling. Longer overlap time was associated with mitral A velocity (r=0.53, P<0.0001) and left atrial booster pump strain (r=0.42, P<0.0001).

Conclusions

Shortening of diastolic filling interval in tandem with increased heart rate during exercise does not limit cardiac output reserve or exercise capacity in HFpEF.

Beyond hypertension: Diastolic dysfunction associated with cancer treatment in the era of cardio-oncology

Cancer patients are at an increased risk of cardiovascular events. Both old-generation cytostatics/cytotoxics and new-generation "targeted" drugs can in fact damage cardiomyocytes, endothelial cells of veins and arteries, specialized cells of the conduction system, pericardium, and valves. A new discipline, cardio-oncology, has therefore developed with the aim of protecting cancer patients from cardiovascular events, while also providing them with the best possible oncologic treatment. Anthracyclines have long been known to elicit cardiotoxicity that, depending on treatment- or patient-related factors, may progress with a variable velocity toward cardiomyopathy and systolic heart failure. However, early compromise of diastolic function may precede systolic dysfunction, and a progression of early diastolic dysfunction to diastolic rather than systolic heart failure has been documented in long-term cancer survivors. This chapter first describes general notions about hypertension in the cancer patient and then moves on reviewing the pathophysiology and clinical trajectories of diastolic dysfunction, and the molecular mechanisms of anthracycline-induced diastolic dysfunction. Diastolic dysfunction can in fact be caused and/or aggravated by hypertension. Pharmacologic foundations and therapeutic opportunities to prevent or treat diastolic dysfunction before it progresses toward heart failure are also reviewed, with a special emphasis on the mechanisms of action of drugs that raised hopes to treat diastolic dysfunction in the general population (sacubitril/valsartan, guanylyl cyclase activators, phosphodiesterase inhibitors, ranolazine, inhibitors of type-2 sodium-glucose-inked transporter). Cardio-oncologists will be confronted with the risk:benefit ratio of using these drugs in the cancer patient.

Defects in the Proteome and Metabolome in Human Hypertrophic Cardiomyopathy

BACKGROUND

Defects in energetics are thought to be central to the pathophysiology of hypertrophic cardiomyopathy (HCM); yet, the determinants of ATP availability are not known. The purpose of this study is to ascertain the nature and extent of metabolic reprogramming in human HCM, and its potential impact on contractile function.

METHODS

We conducted proteomic and targeted, quantitative metabolomic analyses on heart tissue from patients with HCM and from nonfailing control human hearts.

RESULTS

In the proteomic analysis, the greatest differences observed in HCM samples compared with controls were increased abundances of extracellular matrix and intermediate filament proteins and decreased abundances of muscle creatine kinase and mitochondrial proteins involved in fatty acid oxidation. These differences in protein abundance were coupled with marked reductions in acyl carnitines, byproducts of fatty acid oxidation, in HCM samples. Conversely, the ketone body 3-hydroxybutyrate, branched chain amino acids, and their breakdown products, were all significantly increased in HCM hearts. ATP content, phosphocreatine, nicotinamide adenine dinucleotide and its phosphate derivatives, NADP and NADPH, and acetyl CoA were also severely reduced in HCM compared with control hearts. Functional assays performed on human skinned myocardial fibers demonstrated that the magnitude of observed reduction in ATP content in the HCM samples would be expected to decrease the rate of cross-bridge detachment. Moreover, left atrial size, an indicator of diastolic compliance, was inversely correlated with ATP content in hearts from patients with HCM.

CONCLUSIONS

HCM hearts display profound deficits in nucleotide availability with markedly reduced capacity for fatty acid oxidation and increases in ketone bodies and branched chain amino acids. These results have important therapeutic implications for the future design of metabolic modulators to treat HCM.

Mimicking Metabolic Disturbance in Establishing Animal Models of Heart Failure With Preserved Ejection Fraction

Heart failure (HF), the terminal state of different heart diseases, imposed a significant health care burden worldwide. It is the last battlefield in dealing with cardiovascular diseases. HF with preserved ejection fraction (HFpEF) is a type of HF in which the symptoms and signs of HF are mainly ascribed to diastolic dysfunction of left ventricle, whereas systolic function is normal or near-normal. Compared to HF with reduced ejection fraction (HFrEF), the diagnosis and treatment of HFpEF have made limited progress, partly due to the lack of suitable animal models for translational studies in the past. Given metabolic disturbance and inflammatory burden contribute to HFpEF pathogenesis, recent years have witnessed emerging studies focusing on construction of animal models with HFpEF phenotype by mimicking metabolic disorders. These models prefer to recapitulate the metabolic disorders and endothelial dysfunction, leading to the more detailed understanding of the entity. In this review, we summarize the currently available animal models of HFpEF with metabolic disorders, as well as their advantages and disadvantages as tools for translational studies.

Early cardiac-chamber-specific fingerprints in heart failure with preserved ejection fraction detected by FTIR and Raman spectroscopic techniques

The pathophysiology of heart failure with preserved ejection fraction (HFpEF) is a matter of investigation and its diagnosis remains challenging. Although the mechanisms that are responsible for the development of HFpEF are not fully understood, it is well known that nearly 80% of patients with HFpEF have concomitant hypertension. We investigated whether early biochemical alterations were detectable during HFpEF progression in salt-induced hypertensive rats, using Fourier-transformed infrared (FTIR) and Raman spectroscopic techniques as a new diagnostic approach. Greater protein content and, specifically, greater collagen deposition were observed in the left atrium and right ventricle of hypertensive rats, together with altered metabolism of myocytes. Additionally, Raman spectra indicated a conformational change, or different degree of phosphorylation/methylation, in tyrosine-rich proteins. A correlation was found between tyrosine content and cardiac fibrosis of both right and left ventricles. Microcalcifications were detected in the left and right atria of control animals, with a progressive augmentation from six to 22 weeks. A further increase occurred in the left ventricle and right atrium of 22-week salt-fed animals, and a positive correlation was shown between the mineral deposits and the cardiac size of the left ventricle. Overall, FTIR and Raman techniques proved to be sensitive to early biochemical changes in HFpEF and preceded clinical humoral and imaging markers.

Evaluation of the left ventricular systolic strain in hypocalcemic infants with two-dimensional speckle tracking echocardiography

INTRODUCTION

Speckle tracking echocardiography (STE) is a new emerging method for evaluation of the cardiac systolic performance. We characterized left ventricular (LV) systolic functions of hypocalcemic infants, and assessed the effects of calcium and vitamin D supplementations on LV systolic functions using two-dimensional STE.

PATIENTS AND METHODS

A prospective controlled study was conducted in Mansoura University Children's Hospital, Egypt from 2015 to 2018 including 88 hypocalcemic infants (patient group) and 30 healthy controls. We subdivided the patient group into vitamin D deficiency group (n = 32) and normal vitamin D group (n = 56). All infants were investigated for serum phosphorus, alkaline phosphatase and 25-hydroxy vitamin D levels. Both patients and controls were initially evaluated for LV systolic functions using two-dimensional STE. After correction of hypocalcemia and vitamin D deficiency, reevaluation of LV systolic functions was done for the patient group.

RESULTS

LV systolic strains were lower in the patient group than controls (p < .001). After recovery of hypocalcemia of the patients, we reported significant improvement of strains and significant reductions of the end-diastolic and end-systolic volumes of the left ventricle (p < .001). Global longitudinal and circumferential strains were lower in patients with vitamin D deficiency than patients with normal vitamin D levels (p < .001). The LV systolic strain improved after correction of vitamin D deficiency and hypocalcemia (p < .001).

CONCLUSION

Two-dimensional STE could detect and follow up early LV systolic dysfunction in infants with hypocalcemia and vitamin D deficiency.

Role of ranolazine in heart failure: From cellular to clinic perspective

Ranolazine was approved by the US Food and Drug Administration as an antianginal drug in 2006, and has been used since in certain groups of patients with stable angina. The therapeutic action of ranolazine was initially attributed to inhibitory effects on fatty acids metabolism. As investigations went on, however, it developed that the main beneficial effects of ranolazine arise from its action on the late sodium current in the heart. Since late sodium currents were discovered to be involved in various heart pathologies such as ischemia, arrhythmias, systolic and diastolic dysfunctions, and all these conditions are associated with heart failure, ranolazine has in some way been tested either directly or indirectly on heart failure in numerous experimental and clinical studies. As the heart continuously remodels following any sort of severe injury, the inhibition by ranolazine of the underlying mechanisms of cardiac remodeling including ion disturbances, oxidative stress, inflammation, apoptosis, fibrosis, metabolic dysregulation, and neurohormonal impairment are discussed, along with unresolved issues. A projection of pathologies targeted by ranolazine from cellular level to clinical is provided in this review.

Personalized pacing for diastolic dysfunction and heart failure with preserved ejection fraction: Design and rationale for the myPACE randomized controlled trial

Background

Patients with pacemakers and heart failure with preserved ejection fraction (HFpEF) or isolated diastolic dysfunction (DD) may benefit from a higher backup heart rate (HR) setting compared with the standard setting of 60 bpm.

Objective

The purpose of this study was to assess the effects of a personalized backup HR setting (myPACE group) compared with 60 bpm (control group).

Methods

In this prospective, blinded, randomized controlled study, pacemaker patients with DD or HFpEF and atrial pacing with intrinsic ventricular conduction or conduction system or biventricular pacing are randomized to the myPACE group or control group for 1 year. The primary outcome is the change in Minnesota Living with Heart Failure Questionnaire (MLHFQ) scores. Secondary endpoints include changes in N-terminal pro–brain natriuretic peptide levels, physical and emotional MLHFQ subscores, and pacemaker-detected atrial arrhythmia burden, patient activity levels, and thoracic impedance; hospitalization for heart failure, atrial fibrillation, cerebrovascular accident, or myocardial infarction; and loop diuretic or antiarrhythmic medication initiation or up-titration. A sample size of 118 subjects is expected to allow detection of a 5-point change in MLHFQ score in an intention-to-treat analysis and allow initial assessment of clinical outcomes and subgroup analyses.

Results

Enrollment began in July 2019. As of November 2020, 107 subjects have been enrolled. It is projected that the 1-year follow-up will be completed by December 2021.

Conclusion

Atrial pacing with intrinsic ventricular conduction or advanced ventricular pacing at a higher, personalized backup HR may be a therapeutic target for patients with isolated DD or HFpEF. The myPACE trial is designed to test this hypothesis.

Potential Mechanisms of SGLT2 Inhibitors for the Treatment of Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is an unsolved and growing concern in cardiovascular medicine. While no treatment options that improve prognosis in HFpEF patients has been established so far, SGLT2 inhibitors (SGLT2i) are currently being investigated for the treatment of HFpEF patients. SGLT2i have already been shown to mitigate comorbidities associated with HFpEF such as type 2 diabetes and chronic renal disease, however, more recently there has been evidence that they may also directly improve diastolic function. In this article, we discuss some potential beneficial mechanisms of SGLT2i in the pathophysiology of HFpEF with focus on contractile function.

Similarities and Differences Between HFmrEF and HFpEF

The new guidelines classify heart failure (HF) into three subgroups based on the ejection fraction (EF): HF with reduced EF (HFrEF), HF with mid-range EF (HFmrEF), and HF with preserved EF (HFpEF). The new guidelines regarding the declaration of HFmrEF as a unique phenotype have achieved the goal of stimulating research on the basic characteristics, pathophysiology, and treatment of HF patients with a left ventricular EF of 40-49%. Patients with HFmrEF have more often been described as an intermediate population between HFrEF and HFpEF patients; however, with regard to etiology and clinical indicators, they are more similar to the HFrEF population. Concerning clinical prognosis, they are closer to HFpEF because both populations have a good prognosis and quality of life. Meanwhile, growing evidence indicates that HFmrEF and HFpEF show heterogeneity in presentation and pathophysiology, and the emergence of this heterogeneity often plays a crucial role in the prognosis and treatment of the disease. To date, the exact mechanisms and effective treatment strategies of HFmrEF and HFpEF are still poorly understood, but some of the current evidence, from observational studies and post-hoc analyses of randomized controlled trials, have shown that patients with HFmrEF may benefit more from HFrEF treatment strategies, such as beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, mineralocorticoid receptor antagonists, and sacubitril/valsartan. This review summarizes available data from current clinical practice and mechanistic studies in terms of epidemiology, etiology, clinical indicators, mechanisms, and treatments to discuss the potential association between HFmrEF and HFpEF patients.

Enhancing diastolic function by strain-dependent detachment of cardiac myosin crossbridges

The force response of cardiac muscle undergoing a quick stretch is conventionally interpreted to represent stretching of attached myosin crossbridges (phase 1) and detachment of these stretched crossbridges at an exponential rate (phase 2), followed by crossbridges reattaching in increased numbers due to an enhanced activation of the thin filament (phases 3 and 4). We propose that, at least in mammalian cardiac muscle, phase 2 instead represents an enhanced detachment rate of myosin crossbridges due to stretch, phase 3 represents the reattachment of those same crossbridges, and phase 4 is a passive-like viscoelastic response with power-law relaxation. To test this idea, we developed a two-state model of crossbridge attachment and detachment. Unitary force was assigned when a crossbridge was attached, and an elastic force was generated when an attached crossbridge was displaced. Attachment rate, f(x), was spatially distributed with a total magnitude f₀. Detachment rate was modeled as g(x) = g₀+ g₁x, where g₀ is a constant and g₁ indicates sensitivity to displacement. The analytical solution suggested that the exponential decay rate of phase 2 represents (f₀ + g₀) and the exponential rise rate of phase 3 represents g₀. The depth of the nadir between phases 2 and 3 is proportional to g₁. We prepared skinned mouse myocardium and applied a 1% stretch under varying concentrations of inorganic phosphate (Pi). The resulting force responses fitted the analytical solution well. The interpretations of phases 2 and 3 were consistent with lower f₀ and higher g₀ with increasing Pi. This novel scheme of interpreting the force response to a quick stretch does not require enhanced thin-filament activation and suggests that the myosin detachment rate is sensitive to stretch. Furthermore, the enhanced detachment rate is likely not due to the typical detachment mechanism following MgATP binding, but rather before MgADP release, and may involve reversal of the myosin power stroke.

Effects of different exercise modalities on cardiac dysfunction in heart failure with preserved ejection fraction

AIMS

Heart failure with preserved ejection fraction (HFpEF) is an increasingly prevalent disease. Physical exercise has been shown to alter disease progression in HFpEF. We examined cardiomyocyte Ca²⁺ homeostasis and left ventricular function in a metabolic HFpEF model in sedentary and trained rats following 8 weeks of moderate-intensity continuous training (MICT) or high-intensity interval training (HIIT).

METHODS AND RESULTS

Left ventricular in vivo function (echocardiography) and cardiomyocyte Ca²⁺ transients (CaTs) (Fluo-4, confocal) were compared in ZSF-1 obese (metabolic syndrome, HFpEF) and ZSF-1 lean (control) 21- and 28-week-old rats. At 21 weeks, cardiomyocytes from HFpEF rats showed prolonged Ca²⁺ reuptake in cytosolic and nuclear CaTs and impaired Ca²⁺ release kinetics in nuclear CaTs. At 28 weeks, HFpEF cardiomyocytes had depressed CaT amplitudes, decreased sarcoplasmic reticulum (SR) Ca²⁺ content, increased SR Ca²⁺ leak, and elevated diastolic [Ca²⁺ ] following increased pacing rate (5 Hz). In trained HFpEF rats (HIIT or MICT), cardiomyocyte SR Ca²⁺ leak was significantly reduced. While HIIT had no effects on the CaTs (1-5 Hz), MICT accelerated early Ca²⁺ release, reduced the amplitude, and prolonged the CaT without increasing diastolic [Ca²⁺ ] or cytosolic Ca²⁺ load at basal or increased pacing rate (1-5 Hz). MICT lowered pro-arrhythmogenic Ca²⁺ sparks and attenuated Ca²⁺ -wave propagation in cardiomyocytes. MICT was associated with increased stroke volume in HFpEF.

CONCLUSIONS

In this metabolic rat model of HFpEF at an advanced stage, Ca²⁺ release was impaired under baseline conditions. HIIT and MICT differentially affected Ca²⁺ homeostasis with positive effects of MICT on stroke volume, end-diastolic volume, and cellular arrhythmogenicity.

BET inhibition blocks inflammation-induced cardiac dysfunction and SARS-CoV-2 infection

Cardiac injury and dysfunction occur in COVID-19 patients and increase the risk of mortality. Causes are ill defined but could be through direct cardiac infection and/or inflammation-induced dysfunction. To identify mechanisms and cardio-protective drugs, we use a state-of-the-art pipeline combining human cardiac organoids with phosphoproteomics and single nuclei RNA sequencing. We identify an inflammatory “cytokine-storm”, a cocktail of interferon gamma, interleukin 1β, and poly(I:C), induced diastolic dysfunction. Bromodomain-containing protein 4 is activated along with a viral response that is consistent in both human cardiac organoids (hCOs) and hearts of SARS-CoV-2-infected K18-hACE2 mice. Bromodomain and extraterminal family inhibitors (BETi) recover dysfunction in hCOs and completely prevent cardiac dysfunction and death in a mouse cytokine-storm model. Additionally, BETi decreases transcription of genes in the viral response, decreases ACE2 expression, and reduces SARS-CoV-2 infection of cardiomyocytes. Together, BETi, including the Food and Drug Administration (FDA) breakthrough designated drug, apabetalone, are promising candidates to prevent COVID-19 mediated cardiac damage.

Human iPSC-engineered cardiac tissue platform faithfully models important cardiac physiology

Cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CM) may provide an important bridge between animal models and the intact human myocardium. Fulfilling this potential is hampered by their relative immaturity, leading to poor physiological responsiveness. hiPSC-CMs grown in traditional two-dimensional (2D) culture lack a t-tubular system, have only rudimentary intracellular calcium-handling systems, express predominantly embryonic sarcomeric protein isoforms, and preferentially use glucose as an energy substrate. Culturing hiPSC-CM in a variety of three-dimensional (3D) environments and the addition of nutritional, pharmacological, and electromechanical stimuli have proven, to various degrees, to be beneficial for maturation. We present a detailed assessment of a novel model in which hiPSC-CMs and hiPSC-derived cardiac fibroblasts are cocultured in a 3D fibrin matrix to form engineered cardiac tissue constructs (hiPSC-ECTs). The hiPSC-ECTs are responsive to physiological stimuli, including stretch, frequency, and β-adrenergic stimulation, develop a t-tubular system, and demonstrate calcium-handling and contractile kinetics that compare favorably with ventricular human myocardium. Furthermore, transcript levels of various genes involved in calcium-handling and contraction are increased. These markers of maturation become more robust over a relatively short period of time in culture (6 wk vs. 2 wk in hiPSC-ECTs). A comparison of the hiPSC-ECT molecular and performance variables with those of human cardiac tissue and other available engineered tissue platforms is provided to aid selection of the most appropriate platform for the research question at hand. Important and noteworthy aspects of this human cardiac model system are its reliance on "off-the-shelf" equipment, ability to provide detailed physiological performance data, and the ability to achieve a relatively mature cardiac physiology without additional nutritional, pharmacological, and electromechanical stimuli that may elicit unintended effects on function.NEW & NOTEWORTHY This study seeks to provide an in-depth assessment of contractile performance of human iPSC-derived cardiomyocytes cultured together with fibroblasts in a 3-dimensional-engineered tissue and compares performance both over time as cells mature, and with corresponding measures found in the literature using alternative 3D culture configurations. The suitability of 3D-engineered human cardiac tissues to model cardiac function is emphasized, and data provided to assist in the selection of the most appropriate configuration based on the target application.

[Circulating Neuregulin-1 and Chronic Heart Failure with Preserved Ejection]

Chronic heart failure (CHF) with preserved ejection fraction (CHFpEF) is an unsolved, socially relevant challenge since it is associated with a high level of morbidity and mortality. Early markers for this pathology are unavailable, and therapeutic approaches are undeveloped. This necessitates extensive studying the mechanisms of CHFpEF to identify therapeutic targets. According to current notions, systemic inflammation and endothelial dysfunction play an important role in the pathogenesis of CHFpEF. These processes induce the development of myocardial fibrosis and impairment of cardiomyocyte relaxation, thereby resulting in diastolic dysfunction and increased left ventricular (LV) filling pressure. Neuregulin-1 (NRG-1) is a paracrine growth factor and a natural agonist of ErbB receptor family synthesized in the endothelium of coronary microvessels. The NRG-1 / ErbB4 system of the heart is activated at early stages of CHFpEF to enhance the cardiomyocyte resistance to oxidative stress. Preclinical and clinical (phases II and III) studies have shown that the recombinant NRG-1 therapy results in improvement of myocardial contractility and in LV reverse remodeling. Results of recent studies suggest possible anti-inflammatory and antifibrotic effects of NRG-1, which warrants studying the activity of this system in patients with CHFpEF.

Myocardial Gene Expression Signatures in Human Heart Failure With Preserved Ejection Fraction

BACKGROUND

Heart failure (HF) with preserved ejection fraction (HFpEF) constitutes half of all HF but lacks effective therapy. Understanding of its myocardial biology remains limited because of a paucity of heart tissue molecular analysis.

METHODS

We performed RNA sequencing on right ventricular septal endomyocardial biopsies prospectively obtained from patients meeting consensus criteria for HFpEF (n=41) contrasted with right ventricular septal tissue from patients with HF with reduced ejection fraction (HFrEF, n=30) and donor controls (n=24). Principal component analysis and hierarchical clustering tested for transcriptomic distinctiveness between groups, effect of comorbidities, and differential gene expression with pathway enrichment contrasted HF groups and donor controls. Within HFpEF, non-negative matrix factorization and weighted gene coexpression analysis identified molecular subgroups, and the resulting clusters were correlated with hemodynamic and clinical data.

RESULTS

Patients with HFpEF were more often women (59%), African American (68%), obese (median body mass index 41), and hypertensive (98%), with clinical HF characterized by 65% New York Heart Association Class III or IV, nearly all on a loop diuretic, and 70% with a HF hospitalization in the previous year. Principal component analysis separated HFpEF from HFrEF and donor controls with minimal overlap, and this persisted after adjusting for primary comorbidities: body mass index, sex, age, diabetes, and renal function. Hierarchical clustering confirmed group separation. Nearly half the significantly altered genes in HFpEF versus donor controls (1882 up, 2593 down) changed in the same direction in HFrEF; however, 5745 genes were uniquely altered between HF groups. Compared with controls, uniquely upregulated genes in HFpEF were enriched in mitochondrial adenosine triphosphate synthesis/electron transport, pathways downregulated in HFrEF. HFpEF-specific downregulated genes engaged endoplasmic reticulum stress, autophagy, and angiogenesis. Body mass index differences largely accounted for HFpEF upregulated genes, whereas neither this nor broader comorbidity adjustment altered pathways enriched in downregulated genes. Non-negative matrix factorization identified 3 HFpEF transcriptomic subgroups with distinctive pathways and clinical correlates, including a group closest to HFrEF with higher mortality, and a mostly female group with smaller hearts and proinflammatory signaling. These groupings remained after sex adjustment. Weighted gene coexpression analysis yielded analogous gene clusters and clinical groupings.

CONCLUSIONS

HFpEF exhibits distinctive broad transcriptomic signatures and molecular subgroupings with particular clinical features and outcomes. The data reveal new signaling targets to consider for precision therapeutics.

Cardiac Mechanoenergetics in Patients with Acute Myocardial Infarction: From Pressure-Volume Loop Diagram Related to Cardiac Oxygen Consumption

Acute myocardial infarction (AMI) results in significant changes in cardiac structure and functions, leading to left ventricular remodeling and subsequent systolic and diastolic dysfunction. To improve current approaches in diagnoses, treatments, and prevention of cardiovascular diseases, a better understanding of cardiac mechanoenergetics, including systolic performance and energy demand, becomes paramount. In this review, we summarize cardiac mechanics, cardiac energetics, and their relationship in complications related to AMI using 2 important physiologic frameworks, pressure-volume loops and the Vo₂-pressure-volume area relationship diagram, as they are powerful tools for understanding physiologic behavior and mechanoenergetics of the left ventricle.

Left ventricular dysfunction in heart failure with preserved ejection fraction-molecular mechanisms and impact on right ventricular function

The current classification of heart failure (HF) based on left ventricular (LV) ejection fraction (EF) identifies a large group of patients with preserved ejection fraction (HFpEF) with significant morbidity and mortality but without prognostic benefit from current HF therapy. Co-morbidities and conditions such as arterial hypertension, diabetes mellitus, chronic kidney disease, adiposity and aging shape the clinical phenotype and contribute to mortality. LV diastolic dysfunction and LV structural remodeling are hallmarks of HFpEF, and are linked to remodeling of the cardiomyocyte and extracellular matrix. Pulmonary hypertension (PH) and right ventricular dysfunction (RVD) are particularly common in HFpEF, and mortality is up to 10-fold higher in HFpEF patients with vs. without RV dysfunction. Here, we review alterations in cardiomyocyte function (i.e., ion homeostasis, sarcomere function and cellular metabolism) associated with diastolic dysfunction and summarize the main underlying cellular pathways. The contribution and interaction of systemic and regional upstream signaling such as chronic inflammation, neurohumoral activation, and NO-cGMP-related pathways are outlined in detail, and their diagnostic and therapeutic potential is discussed in the context of preclinical and clinical studies. In addition, we summarize prevalence and pathomechanisms of RV dysfunction in the context of HFpEF and discuss mechanisms connecting LV and RV dysfunction in HFpEF. Dissecting the molecular mechanisms of LV and RV dysfunction in HFpEF may provide a basis for an improved classification of HFpEF and for therapeutic approaches tailored to the molecular phenotype.

Matrix Metalloproteinases and Tissue Inhibitors of Metalloproteinases in Extracellular Matrix Remodeling during Left Ventricular Diastolic Dysfunction and Heart Failure with Preserved Ejection Fraction: A Systematic Review and Meta-Analysis

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are pivotal regulators of extracellular matrix (ECM) composition and could, due to their dynamic activity, function as prognostic tools for fibrosis and cardiac function in left ventricular diastolic dysfunction (LVDD) and heart failure with preserved ejection fraction (HFpEF). We conducted a systematic review on experimental animal models of LVDD and HFpEF published in MEDLINE or Embase. Twenty-three studies were included with a total of 36 comparisons that reported established LVDD, quantification of cardiac fibrosis and cardiac MMP or TIMP expression or activity. LVDD/HFpEF models were divided based on underlying pathology: hemodynamic overload (17 comparisons), metabolic alteration (16 comparisons) or ageing (3 comparisons). Meta-analysis showed that echocardiographic parameters were not consistently altered in LVDD/HFpEF with invasive hemodynamic measurements better representing LVDD. Increased myocardial fibrotic area indicated comparable characteristics between hemodynamic and metabolic models. Regarding MMPs and TIMPs; MMP2 and MMP9 activity and protein and TIMP1 protein levels were mainly enhanced in hemodynamic models. In most cases only mRNA was assessed and there were no correlations between cardiac tissue and plasma levels. Female gender, a known risk factor for LVDD and HFpEF, was underrepresented. Novel studies should detail relevant model characteristics and focus on MMP and TIMP protein expression and activity to identify predictive circulating markers in cardiac ECM remodeling.

Heart Rate-Induced Myocardial Ca2+ Retention and Left Ventricular Volume Loss in Patients With Heart Failure With Preserved Ejection Fraction

Background

Increases in heart rate are thought to result in incomplete left ventricular (LV) relaxation and elevated filling pressures in patients with heart failure with preserved ejection fraction (HFpEF). Experimental studies in isolated human myocardium have suggested that incomplete relaxation is a result of cellular Ca²⁺ overload caused by increased myocardial Na⁺ levels. We tested these heart rate paradigms in patients with HFpEF and referent controls without hypertension.

Methods and Results

In 22 fully sedated and instrumented patients (12 controls and 10 patients with HFpEF) in sinus rhythm with a preserved ejection fraction (≥50%) we assessed left‐sided filling pressures and volumes in sinus rhythm and with atrial pacing (95 beats per minute and 125 beats per minute) before atrial fibrillation ablation. Coronary sinus blood samples and flow measurements were also obtained. Seven women and 15 men were studied (aged 59±10 years, ejection fraction 61%±4%). Patients with HFpEF had a history of hypertension, dyspnea on exertion, concentric LV remodeling and a dilated left atrium, whereas controls did not. Pacing at 125 beats per minute lowered the mean LV end‐diastolic pressure in both groups (controls −4.3±4.1 mm Hg versus patients with HFpEF −8.5±6.0 mm Hg, P=0.08). Pacing also reduced LV end‐diastolic volumes. The volume loss was about twice as much in the HFpEF group (controls −15%±14% versus patients with HFpEF −32%±11%, P=0.009). Coronary venous [Ca²⁺] increased after pacing at 125 beats per minute in patients with HFpEF but not in controls. [Na⁺] did not change.

Conclusions

Higher resting heart rates are associated with lower filling pressures in patients with and without HFpEF. Incomplete relaxation and LV filling at high heart rates lead to a reduction in LV volumes that is more pronounced in patients with HFpEF and may be associated with myocardial Ca²⁺ retention.

Evaluation of the Effects of Schisandra chinensis on the Myocardium of Rats with Hyperthyroid Heart Disease by Using Velocity Vector Imaging Combined with the Estimation of p53 Expression and Calmodulin Activity

Schisandra chinensis (SC) is reported to improve myocardial ischemia. Velocity vector imaging (VVI) is a noninvasive technique for evaluating myocardial function in humans, while few reported on the application in animals. In this study, we aimed to evaluate the improved effects of SC on the myocardium of Sprague Dawley rats having hyperthyroid heart disease (HHD) using VVI technique. HHD models were established by injecting daily with subcutaneous levothyroxine (0.5 mg/kg). Then, the SC group was administered the aqueous extract of SC (2 g/kg) once daily, while the HHD and control (CON) groups were administered the same amount of distilled water daily. All the rats were provided the same amount of food and water daily, and the intervention was stopped after 28 days. The efficacy of SC in HHD rats was evaluated by ultrasound VVI. The serum total triiodothyronine level, total thyroxine level, N-terminal pro-brain natriuretic peptide expression, p53 expression, and calmodulin (CaM) activity were assessed by western blotting, Hematoxylin-Eosin and Masson staining, and electron microscopy. The results indicated that SC significantly improved the systolic velocity, diastolic velocity, strain, systolic strain rate, and diastolic strain rate of the heart by significantly reducing p53 expression and CaM activity (P < 0.05), improving myocardial fibrosis in HHD rats. Also, VVI can be a valuable tool for the evaluation of myocardial function in HHD rats.

Heart failure with preserved ejection fraction: insights into diagnosis and pathophysiology

Heart failure with preserved ejection fraction (HFpEF) accounts for at least half the cases of heart failure, currently diagnosed. There are several cardiac and non-cardiac manifestations of the syndrome. Structure and function abnormalities can include all four cardiac chambers. The left ventricle has abnormal systolic and diastolic functions which can be examined by invasive and non-invasive measurements. In addition, the left atrium enlarges with abnormal left atrial function, pulmonary hypertension occurs, and the right ventricle can develop hypertrophy, enlargement, and systolic dysfunction. There are a paucity of data on calcium handling in HFpEF patients. Growing literature supports the presence of abnormalities in titin and its phosphorylation, and increased interstitial fibrosis contributing to increased chamber stiffness. A systemic inflammatory state causing reduced myocardial cyclic guanosine monophosphate along with defects in the unfolded protein response have been recently reported. Diagnosis relies on signs and symptoms of heart failure, preserved ejection fraction, and detection of diastolic function abnormalities based on echocardiographic findings and abnormally elevated natriuretic peptide levels or invasive measurements of wedge pressure at rest or with exercise. There are currently two diagnostic algorithms: H2FPEF, and HFA-PEFF with limited data comparing their performance head to head in the same patient population. Despite the growing understanding of the syndrome's pathophysiology, there have been little success in developing specific treatment for patients with HFpEF.

Hypocalcaemia predicts 12-month re-hospitalization in heart failure

BACKGROUND

Potential pathophysiology of heart failure with preserved ejection fraction (HFpEF) has not been fully explored. The aim of the study was to reveal the association of serum calcium concentration at baseline with 12-month clinical outcome in the disease.

MATERIALS AND METHODS

A total of 350 patients with newly diagnosed HFpEF were included in this prospective observational study. There were no malignant tumour, kidney disease, thyroid disease, calcium and vitamin D supplements in the patients. All of them received 12-month follow-up, and endpoints were cardiac re-hospitalization and death. Baseline serum calcium concentration was measured using AIA2000ST enzyme immunoassay analyser. Cardiopulmonary exercise, six-minute walk distance test, EQ5D questionnaire and cardiac ultrasound were performed to evaluate exercise capacity, quality of life and left ventricle function.

RESULTS

Multivariate COX regression analysis revealed that baseline hypocalcaemia was associated with the increased risk of cardiac re-hospitalization and death during the follow-up period (HR: 2.10, 95% CI: 1.69-2.61; HR: 8.26, 95% CI: 2.88-23.70). Furthermore, baseline hypocalcaemia was related to the deterioration of 6-minute walk distance, quality of life score (EQ-5D), right quadriceps strength, left atrium volume index and left ventricular ejection fraction during the follow-up period (HR: 1.65, 95% CI: 1.21-2.26; HR: 1.55, 95% CI: 1.12-2.11; HR: 2.56, 95% CI: 1.68-3.89; HR: 1.44, 95% CI: 1.03-1.98; HR: 1.36, 95% CI: 1.02-1.80).

CONCLUSION

Baseline hypocalcaemia predicted 12-month cardiac re-hospitalization and death in HFpEF patients without calcium and vitamin D supplements partly through left ventricle and skeletal muscle function pathways.

Disturbed cardiac mitochondrial and cytosolic calcium handling in a metabolic risk-related rat model of heart failure with preserved ejection fraction

AIM

Calcium ions play a pivotal role in matching energy supply and demand in cardiac muscle. Mitochondrial calcium concentration is lower in animal models of heart failure with reduced ejection fraction (HFrEF), but limited information is available about mitochondrial calcium handling in heart failure with preserved ejection fraction (HFpEF).

METHODS

We assessed mitochondrial Ca²⁺ handling in intact cardiomyocytes from Zucker/fatty Spontaneously hypertensive F1 hybrid (ZSF1)-lean (control) and ZSF1-obese rats, a metabolic risk-related model of HFpEF. A mitochondrially targeted Ca²⁺ indicator (MitoCam) was expressed in cultured adult rat cardiomyocytes. Cytosolic and mitochondrial Ca²⁺ transients were measured at different stimulation frequencies. Mitochondrial respiration and swelling, and expression of key proteins were determined ex vivo.

RESULTS

At rest, mitochondrial Ca²⁺ concentration in ZSF1-obese was larger than in ZSF1-lean. The diastolic and systolic mitochondrial Ca²⁺ concentrations increased with stimulation frequency, but the steady-state levels were larger in ZSF1-obese. The half-widths of the contractile responses, the resting cytosolic Ca²⁺ concentration and the decay half-times of the cytosolic Ca²⁺ transients were higher in ZSF1-obese, likely because of a lower SERCA2a/phospholamban ratio. Mitochondrial respiration was lower, particularly with nicotinamide adenine dinucleotide (NADH) (complex I) substrates, and mitochondrial swelling was larger in ZSF1-obese.

CONCLUSION

The free mitochondrial calcium concentration is higher in HFpEF owing to alterations in mitochondrial and cytosolic Ca²⁺ handling. This coupling between cytosolic and mitochondrial Ca²⁺ levels may compensate for myocardial ATP supply in vivo under conditions of mild mitochondrial dysfunction. However, if mitochondrial Ca²⁺ concentration is sustainedly increased, it might trigger mitochondrial permeability transition pore opening.

The association between microRNA-21 and hypertension-induced cardiac remodeling

Hypertension is a major public health problem among the aging population worldwide. It causes cardiac remodeling, including hypertrophy and interstitial fibrosis, which leads to development of hypertensive heart disease (HHD). Although microRNA-21 (miR-21) is associated with fibrogenesis in multiple organs, its contribution to cardiac remodeling in hypertension is poorly understood. Circulating miR-21 level was higher in patients with HHD than that in the control subjects. It also positively correlated with serum myocardial fibrotic markers. MiR-21 expression levels were significantly upregulated in the mice hearts after angiotensin II (Ang II) infusion or transverse aortic constriction (TAC) compared with control mice. Expression level of programmed cell death 4 (PDCD4), a main target of miR-21, was significantly decreased in Ang II infused mice and TAC mice compared with control mice. Expression levels of transcriptional activator protein 1 (AP-1) and transforming growth factor-β1 (TGF-β1), which were downstream targets of PDCD4, were increased in Ang II infused mice and TAC mice compared with control mice. In vitro, mirVana-miR-21-specific inhibitor attenuated Ang II-induced PDCD4 downregulation and contributed to subsequent deactivation of AP-1/TGF-β1 signaling pathway in neonatal rat cardiomyocytes. Thus, suppression of miR-21 prevents hypertrophic stimulation-induced cardiac remodeling by regulating PDCD4, AP-1, and TGF-β1 signaling pathway.