Impaired Exercise Tolerance in Heart Failure With Preserved Ejection Fraction: Quantification of Multiorgan System Reserve Capacity

Faecal metaproteomics analysis reveals a high cardiovascular risk profile across healthy individuals and heart failure patients

The gut microbiota is a crucial link between diet and cardiovascular disease (CVD). Using fecal metaproteomics, a method that concurrently captures human gut and microbiome proteins, we determined the crosstalk between gut microbiome, diet, gut health, and CVD. Traditional CVD risk factors (age, BMI, sex, blood pressure) explained < 10% of the proteome variance. However, unsupervised human protein-based clustering analysis revealed two distinct CVD risk clusters (low-risk and high-risk) with different blood pressure (by 9 mmHg) and sex-dependent dietary potassium and fiber intake. In the human proteome, the low-risk group had lower angiotensin-converting enzymes, inflammatory proteins associated with neutrophil extracellular trap formation and auto-immune diseases. In the microbial proteome, the low-risk group had higher expression of phosphate acetyltransferase that produces SCFAs, particularly in fiber-fermenting bacteria. This model identified severity across phenotypes in heart failure patients and long-term risk of cardiovascular events in a large population-based cohort. These findings underscore multifactorial gut-to-host mechanisms that may underlie risk factors for CVD.

Upregulated FoxO1 promotes arrhythmogenesis in mice with heart failure and preserved ejection fraction

Myocardial fibrosis leads to cardiac dysfunction and arrhythmias in heart failure with preserved ejection fraction (HFpEF), but the underlying mechanisms remain poorly understood. Here, RNA sequencing identifies Forkhead Box1 (FoxO1) signaling as abnormal in male HFpEF hearts. Genetic suppression of FoxO1 alters the intercellular communication between cardiomyocytes and fibroblasts, alleviates abnormal diastolic relaxation, and reduces arrhythmias. Targeted downregulation of FoxO1 in activated fibroblasts reduces cardiac fibrosis, blunts arrhythmogenesis and improves diastolic function in HFpEF. These results not only implicate FoxO1 in arrhythmogenesis and lusitropy but also demonstrate that pro-fibrotic remodeling and cardiomyocyte-fibroblast communication can be corrected, constituting an alternative therapeutic strategy for HFpEF.

The Protocol for the Multi-Ethnic, multi-centre raNdomised controlled trial of a low-energy Diet for improving functional status in heart failure with Preserved ejection fraction (AMEND Preserved)

INTRODUCTION

Heart failure with preserved ejection fraction (HFpEF) is characterised by severe exercise intolerance, particularly in those living with obesity. Low-energy meal-replacement plans (MRPs) have shown significant weight loss and potential cardiac remodelling benefits. This pragmatic randomised trial aims to evaluate the efficacy of MRP-directed weight loss on exercise intolerance, symptoms, quality of life and cardiovascular remodelling in a multiethnic cohort with obesity and HFpEF.

METHODS AND ANALYSIS

Prospective multicentre, open-label, blinded endpoint randomised controlled trial comparing low-energy MRP with guideline-driven care plus health coaching. Participants (n=110, age ≥18 years) with HFpEF and clinical stability for at least 3 months will be randomised to receive either MRP (810 kcal/day) or guideline-driven care for 12 weeks. Randomisation is stratified by sex, ethnicity, and baseline Sodium Glucose Cotransporter-2 inhibitor (SGLT2-i) use, using the electronic database RedCap with allocation concealment. Key exclusion criteria include severe valvular, lung or renal disease, infiltrative cardiomyopathies, symptomatic biliary disease or history of an eating disorder. Participants will undergo glycometabolic profiling, echocardiography, MRI for cardiovascular structure and function, body composition analysis (including visceral and subcutaneous adiposity quantification), Kansas City Cardiomyopathy Questionnaire (KCCQ) and Six-Minute Walk Test (6MWT), at baseline and 12 weeks. An optional 24-week assessment will include non-contrast CMR, 6MWT, KCCQ score. Optional substudies include a qualitative study assessing participants' experiences and barriers to adopting MRP, and skeletal muscle imaging and cardiac energetics using 31Phosphorus MR spectroscopy.

STATISTICAL ANALYSIS

Complete case analysis will be conducted with adjustment for baseline randomisation factors including sex, ethnicity and baseline SGLT2-i use. The primary outcome is the change in distance walked during the 6MWT. The primary imaging endpoint is the change in left atrial volume indexed to height on cardiac MRI. Key secondary endpoints include symptoms and quality of life measured by the KCCQ score.

ETHICS AND DISSEMINATION

The Health Research Authority Ethics Committee (REC reference 22/EM/0215) has approved the study. The findings of this study will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05887271.

Heart failure with preserved ejection fraction and atrial fibrillation: epidemiology, pathophysiology, and diagnosis interplay

Heart failure with preserved ejection fraction (HFpEF) and atrial fibrillation (AF) are increasingly prevalent cardiovascular conditions, particularly among the elderly population. These two conditions share common risk factors and often coexist, leading to a complex interplay that alters the clinical course of each other. The pathophysiology of HFpEF is multifaceted and intricately linked, with atrial disease serving as a common pathophysiological pathway. Diagnosis of HFpEF in the setting of AF, and vice versa, can be challenging; thus, effective screening and diagnostic strategies are needed. Understanding the complex relationship between HFpEF and AF is crucial for optimal patient management by timely disease recognition and identification of therapeutic interventions or treatment strategies.

Hydrogen Sulfide Deficiency and Therapeutic Targeting in Cardiometabolic HFpEF: Evidence for Synergistic Benefit with GLP-1/Glucagon Agonism

Background

Heart failure with preserved ejection fraction (HFpEF) is a significant public health concern with limited treatment options. Dysregulated nitric oxide-mediated signaling has been implicated in HFpEF pathophysiology, however, little is known about the role of endogenous hydrogen sulfide (H 2 S) in HFpEF.

Objectives

This study evaluated H 2 S bioavailability in patients and two animal models of cardiometabolic HFpEF and assessed the impact of H 2 S on HFpEF severity through alterations in endogenous H 2 S production and pharmacological supplementation. We also evaluated the effects of the H 2 S donor, diallyl trisulfide (DATS) in combination with the GLP-1/glucagon receptor agonist, survodutide, in HFpEF.

Methods

HFpEF patients and two rodent models of HFpEF ("two-hit" L-NAME + HFD mouse and ZSF1 obese rat) were evaluated for H 2 S bioavailability. Two cohorts of two-hit mice were investigated for changes in HFpEF pathophysiology: (1) endothelial cell cystathionine-γ-lyase (EC-CSE) knockout; (2) H 2 S donor, JK-1, supplementation. DATS and survodutide combination therapy was tested in ZSF1 obese rats.

Results

H 2 S levels were significantly reduced (i.e., 81%) in human HFpEF patients and in both preclinical HFpEF models. This depletion was associated with reduced CSE expression and activity, and increased SQR expression. Genetic knockout of H 2 S -generating enzyme, CSE, worsened HFpEF characteristics, including elevated E/e' ratio and LVEDP, impaired aortic vasorelaxation and increased mortality. Pharmacologic H 2 S supplementation restored H 2 S bioavailability, improved diastolic function and attenuated cardiac fibrosis corroborating an improved HFpEF phenotype. DATS synergized with survodutide to attenuate obesity, improve diastolic function, exercise capacity, and reduce oxidative stress and cardiac fibrosis.

Conclusions

H 2 S deficiency is evident in HFpEF patients and conserved across multiple preclinical HFpEF models. Increasing H 2 S bioavailability improved cardiovascular function, while knockout of endogenous H 2 S production exacerbated HFpEF pathology and mortality. These results suggest H 2 S dysregulation contributes to HFpEF and increasing H 2 S bioavailability may represent a novel therapeutic strategy for HFpEF. Furthermore, our data demonstrate that combining H 2 S supplementation with GLP-1/glucagon receptor agonist may provide synergistic benefits in improving HFpEF outcomes.

Highlights

H 2 S deficiency is evident in both human HFpEF patients and two clinically relevant models. Reduced H 2 S production by CSE and increased metabolism by SQR impair H 2 S bioavailability in HFpEF. Pharmacological H 2 S supplementation improves diastolic function and reduces cardiac fibrosis in HFpEF models. Targeting H 2 S dysregulation presents a novel therapeutic strategy for managing HFpEF. H 2 S synergizes with GLP-1/glucagon agonist and ameliorates HFpEF.

Hepatic Steatosis and Fibrosis, Cardiorespiratory Fitness, and Metabolic Mediators in the Community

BACKGROUND AND AIMS

Individuals with steatotic liver disease (SLD) are at high cardiovascular disease (CVD) risk, but approaches to characterise and mitigate this risk are limited. By investigating relations, and shared metabolic pathways, of hepatic steatosis/fibrosis and cardiorespiratory fitness (CRF), we sought to identify new avenues for CVD risk reduction in SLD.

METHODS

In Framingham Heart Study (FHS) participants (N = 2722, age 54 ± 9 years, 53% women), vibration-controlled transient elastography (VCTE) was performed between 2016-2019 to assess hepatic steatosis (continuous attenuation parameter [CAP]) and fibrosis (liver fibrosis measure [LSM]). Concurrently, participants underwent maximum effort cardiopulmonary exercise testing (CPET), and metabolomic profiling (201 circulating metabolites) was performed in a subsample (N = 1268).

RESULTS

Mean BMI was 28.0 ± 5.3, 27% had hepatic steatosis, 7.6% had fibrosis, and peak oxygen uptake (VO2) was 26.2 ± 6.8 mL/kg/min in men and 20.7 ± 6.0 mL/kg/min in women (95% predicted overall). In linear models adjusted for cardiometabolic risk factors, greater CAP and LSM were associated with lower peak VO2 (p ≤ 0.002 for all), and the CAP association remained significant after BMI adjustment (p < 0.0001). We observed shared metabolic architecture of CAP, LSM, and peak VO2, with metabolites mediating up to 35% (for CAP) and 74% (for LSM) of the association with peak VO2. Metabolite mediators included amino acids and derivatives implicated in cardiometabolic risk and both protective and deleterious lipid species.

CONCLUSIONS

Hepatic steatosis and fibrosis are associated with CRF impairment in the community, and these relations are partly mediated by pathways of altered lipid metabolism and general cardiometabolic risk.

Sympathetic Response to 1-Leg Cycling Exercise Predicts Exercise Capacity in Patients With Heart Failure With Preserved Ejection Fraction

BACKGROUND

In heart failure, sympathetic excess and exercise intolerance impair quality of life. In heart failure with reduced ejection fraction, exercise stimulates a reflex increase in muscle sympathetic nerve activity (MSNA) that relates inversely to peak oxygen uptake (V̇O2peak). Whether similar sympathoexcitatory responses are present in heart failure with preserved EF (HFpEF) and relate to V̇O2peak are unknown.

METHODS

In 13 patients with HFpEF (70±6 years), 17 comorbidity-matched controls (CMC; 67±8 years), and 18 healthy controls (65±8 years), we measured heart rate, blood pressure, and MSNA (microneurography) during (1) 7-minute baseline; (2) 2-minute isometric handgrip (40% maximal voluntary contraction) or rhythmic handgrip (50% and 30% maximal voluntary contraction) exercise, followed by 2-minute postexercise circulatory occlusion; and (3) 4-minute 1-leg cycling (2 minutes each at mild and moderate intensity). V̇O2peak was obtained by open-circuit spirometry.

RESULTS

Resting MSNA was higher and V̇O2peak was lower in HFpEF versus CMCs and healthy controls (all P<0.05). During handgrip, MSNA increased in all groups (all P<0.05); in HFpEF, MSNA was greater than CMCs and healthy controls during HG and postexercise circulatory occlusion at 40% isometric handgrip (all P<0.05) and HG only at 50% and 30% rhythmic handgrip (all P<0.05). During cycling, MSNA (bursts·min-1) decreased during mild (-4±4; P=0.01) and moderate (-8±6; P<0.001) cycling in healthy controls, was unchanged during mild (+1±7; P=0.42) and moderate (+2±8; P=0.28) cycling in CMCs, yet increased in HFpEF during mild (+8±8; P<0.001) and moderate (+9±10; P<0.001) cycling. In HFpEF, the change in MSNA during moderate cycling related inversely to relative (r=-0.72; R 2=0.51; P<0.01) and percent-predicted (r=-0.63; R 2=0.39; P=0.03) V̇O2peak. No statistically significant relationships were detected in controls (P>0.05).

CONCLUSIONS

In contrast to CMCs, patients with HFpEF exhibit augmented MSNA at rest and during exercise. The magnitude of such paradoxical sympathoexcitation during dynamic cycling relates inversely to V̇O2peak, consistent with a neurogenic, vasoconstrictor limit on exercise capacity in HFpEF.

Cardiopulmonary Exercise Testing in Advanced Heart Failure Management

Cardiopulmonary exercise testing (CPET) permits the assessment of gas exchange, electrocardiogram, and hemodynamic patterns throughout exercise, providing a window into multi-organ physiologic reserve during exercise. CPET provides risk stratification and informs management of advanced heart failure (HF). Increasingly, CPET is combined with echocardiography, or invasive right heart catheterization, which enables high-resolution assessment of cardiac and extracardiac limitations to exercise. CPET also represents a cornerstone in the evaluation process for advanced HF interventions. This review underscores the importance and utility of CPET in managing patients with advanced HF.

The sympathetic nervous system in heart failure with preserved ejection fraction

The sympathetic nervous system (SNS) is a major mediator of cardiovascular physiology during exercise in healthy people. However, its role in heart failure with preserved ejection fraction (HFpEF), where exercise intolerance is a cardinal symptom, has remained relatively unexplored. The present review summarizes and critically explores the currently limited data on SNS changes in HFpEF patients with a particular emphasis on caveats of the data and the implications for its subsequent interpretation. While direct measurements of SNS activity in HFpEF patients is scarce, modest increases in resting levels of muscle sympathetic nerve activity are apparent, although this may be due to the co-morbidities associated with the syndrome rather than HFpEF per se. In addition, despite some evidence for dysfunctional sympathetic signaling in the heart, there is no clear evidence for elevated cardiac sympathetic nerve activity. The lack of a compelling prognostic benefit with use of β-blockers in HFpEF patients also suggests a lack of sympathetic hyperactivity to the heart. Similarly, while renal and splanchnic denervation studies have been performed in HFpEF patients, there is no concrete evidence that the sympathetic nerves innervating these organs exhibit heightened activity. Taken together, the totality of data suggests limited evidence for elevated sympathetic nerve activity in HFpEF and that any SNS perturbations that do occur are not universal to all HFpEF patients. Finally, how the SNS responds during exertion in HFpEF patients remains unknown and requires urgent investigation.

Effect of exercise training in patients with chronotropic incompetence and heart failure with preserved ejection fraction: Training-HR study protocol

BACKGROUND

Chronotropic incompetence (ChI) is linked with diminished exercise capacity in heart failure with preserved ejection fraction (HFpEF). Although exercise training has shown potential for improving functional capacity, the exercise modality associated with greater functional and chronotropic response (ChR) is not well-known. Additionally, how the ChR from different exercise modalities mediates functional improvement remains to be determined. This study aimed to evaluate the effect of three different exercise programs over current guideline recommendations on peak oxygen consumption (peakVO2) in patients with ChI HFpEF phenotype.

METHODS AND RESULTS

In this randomized clinical trial, 80 stable symptomatic patients with HFpEF and ChI (NYHA class II-III/IV) are randomized (1:1:1:1) to receive: a) a 12-week program of supervised aerobic training (AT), b) AT and low to moderate-intensity strength training, c)AT and moderate to high-intensity strength training, or d) guideline-based physical activity and exercise recommendations. The primary endpoint is 12-week changes in peakVO2. The secondary endpoints are 12-week changes in ChR, 12-week changes in quality of life, and how ChR changes mediate changes in peakVO2. A mixed-effects model for repeated measures will be used to compare endpoint changes. The mean age is 75.1 ± 7.2 years, and most patients are women (57.5 %) in New York Heart Association functional class II (68.7 %). The mean peakVO2, percent of predicted peakVO2, and ChR are 11.8 ± 2.6 mL/kg/min, 67.2 ± 14.7 %, and 0.39 ± 0.16, respectively. No significant baseline clinical differences between arms are found.

CONCLUSIONS

Training-HR will evaluate the effects of different exercise-based therapies on peakVO2, ChR, and quality of life in patients with ChI HFpEF phenotype.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov (NCT05649787).

Characterization of a novel ovine model of hypertensive heart failure with preserved ejection fraction

The lack of animal models that accurately represent heart failure with preserved ejection fraction (HFpEF) has been a major barrier to the mechanistic understanding and development of effective therapies for this prevalent and debilitating syndrome characterized by multisystem impairments. Herein, we describe the development and characterization of a novel large animal model of HFpEF in older, female sheep with chronic 2-kidney, 1-clip hypertension. At 6-wk post unilateral renal artery clipping, hypertensive HFpEF sheep had higher mean arterial pressure compared with similarly aged ewes without unilateral renal artery clipping (mean arterial pressure = 112.7 ± 15.9 vs. 76.0 ± 10.1 mmHg, P < 0.0001). The hypertensive HFpEF sheep were characterized by 1) echocardiographic evidence of diastolic dysfunction (lateral e' = 0.11 ± 0.02 vs. 0.14 ± 0.04 m/s, P = 0.011; lateral E/e' = 4.25 ± 0.77 vs. 3.63 ± 0.54, P = 0.028) and concentric left ventricular hypertrophy without overt systolic impairment, 2) elevated directly measured left ventricular end-diastolic pressure (13 ± 5 vs. 0.5 ± 1 mmHg, P = 2.1 × 10-6), and 3) normal directly measured cardiac output. Crucially, these hypertensive HFpEF sheep had impaired exercise capacity as demonstrated by their 1) attenuated cardiac output (P = 0.001), 2) augmented pulmonary capillary wedge pressure (P = 0.026), and 3) attenuated hindlimb blood flow (P = 3.4 × 10-4) responses, during graded treadmill exercise testing. In addition, exercise renal blood flow responses were also altered. Collectively, our data indicates that this novel ovine model of HFpEF may be a useful translational research tool because it exhibits similar and clinically relevant impairments as that of patients with HFpEF.NEW & NOTEWORTHY We show that older, female sheep with chronic 2-kidney, 1-clip hypertension have similar cardiac and noncardiac exercise hemodynamic abnormalities as patients with HFpEF. This clinically relevant, translatable, and novel large animal model of HFpEF may be useful for elucidating mechanisms and developing treatments for this increasingly common syndrome with few clinically impactful therapies.

Exercise Therapy Rescues Skeletal Muscle Dysfunction and Exercise Intolerance in Cardiometabolic HFpEF

Exercise intolerance, a hallmark of heart failure with preserved ejection fraction (HFpEF) exacerbated by obesity, involves unclear mechanisms related to skeletal muscle metabolism. In a "2-hit" model of HFpEF, we investigated the ability of exercise therapy (voluntary wheel running) to reverse skeletal muscle dysfunction and exercise intolerance. Using state-of-the-art metabolic cages and a multiomic approach, we demonstrate exercise can rescue dysfunctional skeletal muscle lipid and branched-chain amino acid oxidation and restore exercise capacity in mice with cardiometabolic HFpEF. These results underscore the importance of skeletal muscle metabolism to improve exercise intolerance in HFpEF.

Functional limitation predicts mortality in heart failure with preserved ejection fraction

BACKGROUND

While the prognostic value of six-minute walking test (6MWT) in patients with heart failure (HF) and reduced ejection fraction has been firmly established, there are few or no data correlating the distance walked during 6MWT (6MWD) with mortality in patients with HF with preserved ejection fraction (HFpEF) METHODS: We studied 482 patients with HFpEF who had been admitted to inpatients cardiac rehabilitation. The primary outcome was 3-year all-cause mortality. The association between 6MWD and the primary outcome was assessed using multivariable models. Established risk markers were incorporated into the models.

RESULTS

174 patients died during the 3-year follow-up. Taking the highest tertile of 6MWD (≥360 m) as reference, the adjusted hazard ratio (HR) of the primary outcome was 2.23 (95 % CI 1.31-3.78; p = .003) for the patients in the intermediate tertile (241-359 m) and 4.94 (95 % CI 2.90-8.39; p < .001) for those in the lowest tertile (≤240 m). The annual mortality rate was 25.0 % in the lowest tertile, 10.9 % in the intermediate tertile, and 5.3 % in the highest tertile. When the distance walked was normalized for age, sex, and body mass index and expressed as percent-of-predicted walking distance, the adjusted HR was 1.30 (95 % CI 0.76-2.22; p = .331) for the patients in the intermediate tertile (58.2 % to 77.6 %) and 3.52 (95 % CI 2.12-5.85; p < .001) for those in the lowest tertile (≤58.1 %).

CONCLUSIONS

Our findings suggest that measuring functional capacity by evaluating the distance that a patient can walk over a period of 6 min provides important prognostic information in HFpEF.

Advancing Cardiac Amyloidosis Care Through Insights from Cardiopulmonary Exercise Testing

Cardiac amyloidosis, encompassing both transthyretin (ATTR) and light-chain (AL) types, poses considerable challenges in patient management due to its intricate pathophysiology and progressive course. This narrative review elucidates the pivotal role of cardiopulmonary exercise testing (CPET) in the assessment of these patients. CPET is essential for evaluating disease progression by measuring cardio-respiratory performance and providing prognostic insights. This functional test is crucial not only for tracking the disease trajectory, but also for assessing the effectiveness of disease-modifying therapies. Moreover, CPET facilitates the customization of therapeutic strategies based on individual patient performance, enhancing personalized care. By objectively measuring parameters such as peak oxygen uptake (VO2 peak), ventilatory efficiency, and exercise capacity, clinicians can gain a deeper understanding of the degree of functional impairment and make informed decisions regarding treatment initiation, adjustment, and anticipated outcomes. This review emphasizes the importance of CPET in advancing personalized medicine approaches, ultimately striving to improve the quality of life and clinical outcomes for patients with cardiac amyloidosis.

Adjunctive therapy with an oral H2S donor provides additional therapeutic benefit beyond SGLT2 inhibition in cardiometabolic heart failure with preserved ejection fraction

BACKGROUND AND PURPOSE

Sodium glucose cotransporter 2 inhibitors (SGLT2i) have emerged as a potent therapy for heart failure with preserved ejection fraction (HFpEF). Hydrogen sulphide (H2S), a well-studied cardioprotective agent, could be beneficial in HFpEF. SGLT2i monotherapy and combination therapy involving an SGLT2i and H2S donor in two preclinical models of cardiometabolic HFpEF was investigated.

EXPERIMENTAL APPROACH

Nine-week-old C57BL/6N mice received L-NAME and a 60% high fat diet for five weeks. Mice were then randomized to either control, SGLT2i monotherapy or SGLT2i and H2S donor, SG1002, for five additional weeks. Ten-week-old ZSF1 obese rats were randomized to control, SGLT2i or SGLT2i and SG1002 for 8 weeks. SG1002 monotherapy was investigated in additional animals. Cardiac function (echocardiography and haemodynamics), exercise capacity, glucose handling and multiorgan pathology were monitored during experimental protocols.

KEY RESULTS

SGLT2i treatment improved E/e' ratio and treadmill exercise in both models. Combination therapy afforded increases in cardiovascular sulphur bioavailability that coincided with improved left end-diastolic function (E/e' ratio), exercise capacity, metabolic state, cardiorenal fibrosis, and hepatic steatosis. Follow-up studies with SG1002 monotherapy revealed improvements in diastolic function, exercise capacity and multiorgan histopathology.

CONCLUSIONS AND IMPLICATIONS

SGLT2i monotherapy remediated pathological complications exhibited by two well-established HFpEF models. Adjunctive H2S therapy resulted in further improvements of cardiometabolic perturbations beyond SGLT2i monotherapy. Follow-up SG1002 monotherapy studies inferred an improved phenotype with combination therapy beyond either monotherapy. These data demonstrate the differing effects of SGLT2i and H2S therapy while also revealing the superior efficacy of the combination therapy in cardiometabolic HFpEF.

Identifying the Mechanisms of a Peripherally Limited Exercise Phenotype in Patients With Heart Failure With Preserved Ejection Fraction

BACKGROUND

We identified peripherally limited patients using cardiopulmonary exercise testing and measured skeletal muscle oxygen transport and utilization during invasive single leg exercise testing to identify the mechanisms of the peripheral limitation.

METHODS

Forty-five patients with heart failure with preserved ejection fraction (70±7 years, 27 females) completed seated upright cardiopulmonary exercise testing and were defined as having a (1) peripheral limitation to exercise if cardiac output/oxygen consumption (VO2) was elevated (≥6) or 5 to 6 with a stroke volume reserve >50% (n=31) or (2) a central limitation to exercise if cardiac output/VO2 slope was ≤5 or 5 to 6 with stroke volume reserve <50% (n=14). Single leg knee extension exercise was used to quantify peak leg blood flow (Doppler ultrasound), arterial-to-venous oxygen content difference (femoral venous catheter), leg VO2, and muscle oxygen diffusive conductance. In a subset of participants (n=36), phosphocreatine recovery time was measured by magnetic resonance spectroscopy to determine skeletal muscle oxidative capacity.

RESULTS

Peak VO2 during cardiopulmonary exercise testing was not different between groups (central: 13.9±5.7 versus peripheral: 12.0±3.1 mL/min per kg; P=0.135); however, the peripheral group had a lower peak arterial-to-venous oxygen content difference (central: 13.5±2.0 versus peripheral: 11.1±1.6 mLO2/dL blood; P<0.001). During single leg knee extension, there was no difference in peak leg VO2 (P=0.306), but the peripherally limited group had greater blood flow/VO2 ratio (P=0.024), lower arterial-to-venous oxygen content difference (central: 12.3±2.5 versus peripheral: 10.3±2.2 mLO2/dL blood; P=0.013), and lower muscle oxygen diffusive conductance (P=0.021). A difference in magnetic resonance spectroscopy-derived phosphocreatine recovery time was not detected (P=0.199).

CONCLUSIONS

Peripherally limited patients with heart failure with preserved ejection fraction identified by cardiopulmonary exercise testing have impairments in oxygen transport and utilization at the level of the skeletal muscle quantified by invasive knee extension exercise testing, which includes an increased blood flow/V̇O2 ratio and poor muscle diffusive capacity.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT04068844.

Exercise training for patients with heart failure and preserved ejection fraction. A narrative review

Heart failure with preserved ejection fraction (HFpEF) remains a significant global health challenge, accounting for up to 50% of all heart failure cases and predominantly affecting the elderly and women. Despite advancements in therapeutic strategies, HFpEF's complexity poses substantial challenges in management, particularly due to its high comorbidity burden, including renal failure, atrial fibrillation, and obesity, among others. These comorbidities not only complicate the pathophysiology of HFpEF but also exacerbate its symptoms, necessitating a personalized approach to treatment focused on comorbidity management and symptom alleviation. In heart failure with reduced ejection fraction, exercise training (ET) was effective in improving exercise tolerance, quality of life, and reducing hospitalizations. However, the efficacy of ET in HFpEF patients remains less understood, with limited studies showing mixed results. Exercise intolerance is a key symptom in HFpEF patients, and it has a multifactorial origin since both central and peripheral oxygen mechanisms of transport and utilization are often compromised. Recent evidence underscores the potential of supervised ET in enhancing exercise tolerance and quality of life among HFpEF patients; however, the literature remains sparse and predominantly consists of small-scale studies. This review highlights the critical role of exercise intolerance in HFpEF and synthesizes current knowledge on the benefits of ET. It also calls for a deeper understanding and further research into exercise-based interventions and their underlying mechanisms, emphasizing the need for larger, well-designed studies to evaluate the effectiveness of ET in improving outcomes for HFpEF patients.

Effects of dapagliflozin and empagliflozin on 6-min walk distance in heart failure with preserved and reduced ejection fraction: A systematic review and meta-analysis of randomized controlled trials involving 2624 patients

BACKGROUND

Dapagliflozin and empagliflozin are antidiabetic medications. They are the first two sodium-glucose cotransporter-2 inhibitors (SGLT2i) to receive the US Food and Drug Administration approval to manage heart failure. Emerging new trials have examined changes in the 6-min walk distance as a clinically significant response to dapagliflozin and empagliflozin in patients with heart failure with reduced ejection fraction (HFpEF) and heart failure with preserved ejection fraction (HFrEF). This meta-analysis aims to evaluate the effects of dapagliflozin and empagliflozin on the 6-min walk distance in patients with HFpEF and HFrEF. To our knowledge, no such meta-analysis has been published.

METHODS

Following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we searched four electronic databases (PubMed, EMBASE, Cochrane Library, and Web of Science) to identify eligible studies reported up to December 16, 2023. Using Review Manager software, we reported outcomes as risk ratios (RRs) or mean difference (MD) and confidence intervals (CIs). A p-value ≤ 0.05 is considered as statistically significant.

RESULTS

The meta-analysis included a total of 8 studies with 2624 patients. Overall, the results showed insignificant differences in the 6-min walk between the SGLT2i and placebo (MD 24, 95% CI -0.30 to 18.78, p = 0.06). Results became significant after resolving the heterogeneity (MD 6.72, 95% CI 0.13 to 13.31, p = 0.05). Notably, the results of each drug separately were insignificant. More robust observations occurred in the HFpEF group (MD 10.73, 95% CI 1.08 to 20.39, p = 0.03). Compared to placebo, patients on dapagliflozin reported significant improvement in the Kansas City Cardiomyopathy Questionnaire Clinical Summary (KCCQ-CS) and Overall Summary (KCCQ-OS) with values of MD 5.18 (95% CI 2.80 to 7.57, p < 0.0001) and MD 4.06 (95% CI 1.66 to 6.46, p = 0.0009), respectively. The dapagliflozin group and patients with HFpEF had reported a significant reduction in their weight compared with the control group (MD -0.59 CI -1.09 to -0.08, p = 0.02) and (MD -0.80 CI -1.47 to -0.13, p = 0.02), respectively. No significant side effects were observed for dapagliflozin or empagliflozin.

CONCLUSION

Patients with HFpEF experienced benefits from SGLT2i administration, as evidenced by improved 6-min walk distances and weight reduction. Dapagliflozin demonstrated clinical and overall improvements in KCCQ scores and was more effective in reducing weight than the placebo. Both Dapagliflozin and Empagliflozin were well-tolerated and exhibited favorable safety profiles. Future studies could benefit from a larger patient population, a longer follow-up period, and a broader range of SGLT2i.

Effect of Left Ventricular Diastolic Dysfunction on the Cardiopulmonary Exercise Test in Patients With Cardiovascular Disease

Left ventricular diastolic dysfunction exists in patients with heart failure with reduced ejection fraction and causes activity restriction and a poor prognosis, but there have been few reports about exercise tolerance in patients with diastolic dysfunction, regardless of left ventricular ejection fraction (LVEF). In this study, 294 cardiovascular disease patients who performed a cardiopulmonary exercise test (CPX) with an adequate examination by echocardiography at Fukuoka University Hospital from 2011 to 2020 were investigated. Patients were divided into groups with grade I and grade II or III diastolic dysfunction according to diagnostic criteria, regardless of LVEF, by echocardiography. After adjusting for age, gender, body mass index, smoking, and LVEF by propensity score matching, we compared the results of CPX between the grade I and grade II/III groups. There were no significant differences in hemodynamic parameters, or in the respiratory exchange ratio, oxygen uptake per body weight, oxygen uptake per heart rate, or parameters of ventilatory volume. Ventilatory equivalents per oxygen uptake and per carbon dioxide output were significantly worse in the grade II/III group from the rest to peak periods during CPX. In conclusion, left ventricular diastolic dysfunction worsens ventilatory efficacy during CPX. This effect potentially contributes to a poor prognosis in left ventricular diastolic dysfunction.

Wagner diagram for modeling O2pathway-calculation and graphical display by the Helsinki O2Pathway Tool

Objective.Maximal O2uptake (V˙O2max) reflects the individual's maximal rate of O2transport and utilization through the integrated whole-body pathway composed of the lungs, heart, blood, circulation, and metabolically active tissues. As such,V˙O2maxis strongly associated with physical capacity as well as overall health and thus acts as one predictor of physical performance and as a vital sign in determination of status and progress of numerous clinical conditions. Quantifying the contribution of single parts of the multistep O2pathway toV˙O2maxprovides mechanistic insights into exercise (in)tolerance and into therapy-, training-, or disuse-induced adaptations at individual or group levels. We developed a desktop application (Helsinki O2Pathway Tool-HO2PT) to model numerical and graphical display of the O2pathway based on the 'Wagner diagram' originally formulated by Peter D. Wagner and his colleagues.Approach.The HO2PT was developed and programmed in Python to integrate the Fick principle and Fick's law of diffusion into a computational system to import, calculate, graphically display, and export variables of the Wagner diagram.Main results.The HO2PT models O2pathway both numerically and graphically according to the Wagner diagram and pertains to conditions under which the mitochondrial oxidative capacity of metabolically active tissues exceeds the capacity of the O2transport system to deliver O2to the mitochondria. The tool is based on the Python open source code and libraries and freely and publicly available online for Windows, macOS, and Linux operating systems.Significance.The HO2PT offers a novel functional and demonstrative platform for those interested in examiningV˙O2maxand its determinants by using the Wagner diagram. It will improve access to and usability of Wagner's and his colleagues' integrated physiological model and thereby benefit users across the wide spectrum of contexts such as scientific research, education, exercise testing, sports coaching, and clinical medicine.

Life's Essential 8 Cardiovascular Health Score and Cardiorespiratory Fitness in the Community

BACKGROUND

The relation of cardiorespiratory fitness (CRF) to lifestyle behaviors and factors linked with cardiovascular health remains unclear. We aimed to understand how the American Heart Association's Life's Essential 8 (LE8) score (and its changes over time) relate to CRF and complementary exercise measures in community-dwelling adults.

METHODS AND RESULTS

Framingham Heart Study (FHS) participants underwent maximum effort cardiopulmonary exercise testing for direct quantification of peak oxygen uptake (V̇O2). A 100-point LE8 score was constructed as the average across 8 factors: diet, physical activity, nicotine exposure, sleep, body mass index, lipids, blood glucose, and blood pressure. We related total LE8 score, score components, and change in LE8 score over 8 years with peak V̇O2 (log-transformed) and complementary CRF measures. In age- and sex-adjusted linear models (N=1838, age 54±9 years, 54% women, LE8 score 76±12), a higher LE8 score was associated favorably with peak V̇O2, ventilatory efficiency, resting heart rate, and blood pressure response to exercise (all P<0.0001). A clinically meaningful 5-point higher LE8 score was associated with a 6.0% greater peak V̇O2 (≈1.4 mL/kg per minute at sample mean). All LE8 components were significantly associated with peak V̇O2 in models adjusted for age and sex, but blood lipids, diet, and sleep health were no longer statistically significant after adjustment for all LE8 components. Over an ≈8-year interval, a 5-unit increase in LE8 score was associated with a 3.7% higher peak V̇O2 (P<0.0001).

CONCLUSIONS

Higher LE8 score and improvement in LE8 over time was associated with greater CRF, highlighting the importance of the LE8 factors in maintaining CRF.

Exercise intolerance in heart failure with preserved ejection fraction: Causes, consequences and the journey towards a cure

Heart failure with preserved ejection fraction (HFpEF) accounts for over 50% of all heart failure cases nationwide and continues to rise in its prevalence. The complex, multi-organ involvement of the HFpEF clinical syndrome requires clinicians and investigators to adopt an integrative approach that considers the contribution of both cardiac and non-cardiac function to HFpEF pathophysiology. Thus, this symposium review outlines the key points from presentations covering the contributions of disease-related changes in cardiac function, arterial stiffness, peripheral vascular function, and oxygen delivery and utilization to exercise tolerance in patients with HFpEF. While many aspects of HFpEF pathophysiology remain poorly understood, there is accumulating evidence for a decline in vascular health in this patient group that may be remediable through pharmacological and lifestyle interventions and could improve outcomes and clinical status in this ever-growing patient population.

Novel Strategies in Diagnosing Heart Failure with Preserved Ejection Fraction: A Comprehensive Literature Review

Heart failure (HF) with preserved ejection fraction (HFpEF) is a prevalent global condition affecting approximately 50% of the HF population. With the aging of the worldwide population, its incidence and prevalence are expected to rise even further. Unfortunately, until recently, no effective medications were available to reduce the high mortality and hospitalization rates associated with HFpEF, making it a significant unmet need in cardiovascular medicine. Although HFpEF is commonly defined as HF with normal ejection fraction and elevated left ventricular filling pressure, performing invasive hemodynamic assessments on every individual suspected of having HFpEF is neither feasible nor practical. Consequently, several clinical criteria and diagnostic tools have been proposed to aid in diagnosing HFpEF. Overall, these criteria and tools are designed to assist healthcare professionals in identifying and evaluating patients who may have HFpEF based on a combination of signs, symptoms, biomarkers, and non-invasive imaging findings. By employing these non-invasive diagnostic approaches, clinicians can make informed decisions regarding the best pharmacological and rehabilitation strategies for individuals with suspected HFpEF. This literature review aims to provide an overview of all currently available methods for diagnosing and monitoring this disabling condition.

Early Renal Denervation Attenuates Cardiac Dysfunction in Heart Failure With Preserved Ejection Fraction

BACKGROUND

The renal sympathetic nervous system modulates systemic blood pressure, cardiac performance, and renal function. Pathological increases in renal sympathetic nerve activity contribute to the pathogenesis of heart failure with preserved ejection fraction (HFpEF). We investigated the effects of renal sympathetic denervation performed at early or late stages of HFpEF progression.

METHODS AND RESULTS

Male ZSF1 obese rats were subjected to radiofrequency renal denervation (RF-RDN) or sham procedure at either 8 weeks or 20 weeks of age and assessed for cardiovascular function, exercise capacity, and cardiorenal fibrosis. Renal norepinephrine and renal nerve tyrosine hydroxylase staining were performed to quantify denervation following RF-RDN. In addition, renal injury, oxidative stress, inflammation, and profibrotic biomarkers were evaluated to determine pathways associated with RDN. RF-RDN significantly reduced renal norepinephrine and tyrosine hydroxylase content in both study cohorts. RF-RDN therapy performed at 8 weeks of age attenuated cardiac dysfunction, reduced cardiorenal fibrosis, and improved endothelial-dependent vascular reactivity. These improvements were associated with reductions in renal injury markers, expression of renal NLR family pyrin domain containing 3/interleukin 1β, and expression of profibrotic mediators. RF-RDN failed to exert beneficial effects when administered in the 20-week-old HFpEF cohort.

CONCLUSIONS

Our data demonstrate that early RF-RDN therapy protects against HFpEF disease progression in part due to the attenuation of renal fibrosis and inflammation. In contrast, the renoprotective and left ventricular functional improvements were lost when RF-RDN was performed in later HFpEF progression. These results suggest that RDN may be a viable treatment option for HFpEF during the early stages of this systemic inflammatory disease.

Exercise catheterization in adults post-Fontan with normal and abnormal haemodynamic criteria: Insights into normal Fontan physiology

AIM

The normal (i.e. expected) haemodynamics in adults post-Fontan remain poorly delineated. Moreover, the definitions of elevated exercise pulmonary artery (PA) and PA wedge pressure (PAWP) for this population have not been described.

METHODS AND RESULTS

Seventy-two adults post-Fontan undergoing exercise catheterization were categorized into abnormal (Group I, n = 59; defined as resting mean PA ≥14 mmHg and/or PAWP ≥12 mmHg, ΔPAWP/Δsystemic flow [Qs] >2 mmHg/L/min, and/or ΔPA/Δpulmonary flow >3 mmHg/L/min) and normal (Group II, n = 13) haemodynamics. Thirty-nine patients with non-cardiac dyspnoea (NCD) were included as controls. There was no difference in exercise arterial oxygen saturation (87% [81-92] vs. 89% [85-93], p = 0.29), while exercise PA pressure (27 [23-31] vs. 16 [14.5-19.5] mmHg, p < 0.001) and PAWP were higher (21 [18-28] vs. 12 [8-14] mmHg, p < 0.001) in Group I. At peak exercise, Group I had lower heart rate (97 [81-120] vs. 133 [112.5-147.5] bpm, p < 0.001) and Qs response (67.3 [43.8-93.1] vs. 105.9 (82-118.5) % predicted, p < 0.001) than Group II. Exercise superior vena cava pressures were higher (16 [14-22.5] vs. 5.5 [3-7.3] mmHg, p < 0.001) and arterial oxygen saturation lower (89% [85-93] vs. 97% [96-98], p < 0.001) in Group II compared to NCD, while no differences in PAWP, stroke volume index, heart rate, or Qs response were seen. If defined as two standard deviations above mean values for Group II, elevated PAWP and mean PA pressure post-Fontan would correspond to 20.6 mmHg and 25.8 mmHg, respectively.

CONCLUSION

PAWP >20 mmHg and mean PA pressure >25 mmHg could be used to define elevated values during exercise in adults post-Fontan. The major discrepancy in exercise haemodynamics among Group II compared to controls appears to be the degree of systemic venous hypertension and arterial desaturation.

Right ventricular outflow tract diameter change with exercise: a prospective exercise echocardiography and invasive CPET study

While cardiac output reserve with exercise predicts outcomes in cardiac and pulmonary vascular disease, precise quantification of exercise cardiac output requires invasive cardiopulmonary testing (iCPET). To improve the accuracy of cardiac output reserve estimation with transthoracic echocardiography (TTE), this prospective study aims to define changes in right ventricular outflow tract diameter (RVOTd) with exercise and its relationship with invasively measured haemodynamics. Twenty subjects underwent simultaneous TTE and iCPET, with data collected at rest, leg-raise, 25 W, 50 W (n = 16), 75 W (n = 14), and 100 W (n = 6). This was followed by a second exercise study with real-time RV pressure-volume loops at similar stages (except leg-raise). The overall cohort included heart failure with preserved ejection fraction (n = 12), pulmonary arterial hypertension (n = 5), and non-cardiac dyspnoea (n = 3). RVOTd was reverse engineered from the TTE-derived RVOT velocity time integral (VTI) and iCPET-derived stroke volume, using the formula: Fick stroke volume = RVOT VTI × RVOT area (wherein RVOT area = π × [RVOTd/2]2). RVOTd increased by nearly 3-4% at every 25 W increment. Using linear regression models, where each subject is treated as a categorical variable and adjusting for subject intercept, RVOTd was correlated with haemodynamic variables (cardiac output, heart rate, pulmonary artery and RV pressures). Of all the predictor haemodynamic variables, cardiac output had the highest r2 model fit (adjusted r2 = 0.68), with a unit increase in cardiac output associated with a 0.0678 increase in RVOTd (P < 0.001). Our findings indicate that RVOTd increases by 3-4% with every 25 W increment, predominantly correlated with cardiac output augmentation. These results can improve the accuracy of cardiac output reserve estimation by adjusting for RVOTd with graded exercise during non-invasive CPET and echocardiogram. However, future studies are needed to define these relationships for left ventricular outflow tract diameter.

Eicosanoid and eicosanoid-related inflammatory mediators and exercise intolerance in heart failure with preserved ejection fraction

Systemic inflammation has been implicated in the pathobiology of heart failure with preserved ejection fraction (HFpEF). Here, we examine the association of upstream mediators of inflammation as ascertained by fatty-acid derived eicosanoid and eicosanoid-related metabolites with HFpEF status and exercise manifestations of HFpEF. Among 510 participants with chronic dyspnea and preserved LVEF who underwent invasive cardiopulmonary exercise testing, we find that 70 of 890 eicosanoid and related metabolites are associated with HFpEF status, including 17 named and 53 putative eicosanoids (FDR q-value < 0.1). Prostaglandin (15R-PGF2α, 11ß-dhk-PGF2α) and linoleic acid derivatives (12,13 EpOME) are associated with greater odds of HFpEF, while epoxides (8(9)-EpETE), docosanoids (13,14-DiHDPA), and oxylipins (12-OPDA) are associated with lower odds of HFpEF. Among 70 metabolites, 18 are associated with future development of heart failure in the community. Pro- and anti-inflammatory eicosanoid and related metabolites may contribute to the pathogenesis of HFpEF and serve as potential targets for intervention.

Proteomics and Precise Exercise Phenotypes in Heart Failure With Preserved Ejection Fraction: A Pilot Study

BACKGROUND

While exercise impairments are central to symptoms and diagnosis of heart failure with preserved ejection fraction (HFpEF), prior studies of HFpEF biomarkers have mostly focused on resting phenotypes. We combined precise exercise phenotypes with cardiovascular proteomics to identify protein signatures of HFpEF exercise responses and new potential therapeutic targets.

METHODS AND RESULTS

We analyzed 277 proteins (Olink) in 151 individuals (N=103 HFpEF, 48 controls; 62±11 years; 56% women) with cardiopulmonary exercise testing with invasive monitoring. Using ridge regression adjusted for age/sex, we defined proteomic signatures of 5 physiological variables involved in HFpEF: peak oxygen uptake, peak cardiac output, pulmonary capillary wedge pressure/cardiac output slope, peak pulmonary vascular resistance, and peak peripheral O2 extraction. Multiprotein signatures of each of the exercise phenotypes captured a significant proportion of variance in respective exercise phenotypes. Interrogating the importance (ridge coefficient magnitude) of specific proteins in each signature highlighted proteins with putative links to HFpEF pathophysiology (eg, inflammatory, profibrotic proteins), and novel proteins linked to distinct physiologies (eg, proteins involved in multiorgan [kidney, liver, muscle, adipose] health) were implicated in impaired O2 extraction. In a separate sample (N=522, 261 HF events), proteomic signatures of peak oxygen uptake and pulmonary capillary wedge pressure/cardiac output slope were associated with incident HFpEF (odds ratios, 0.67 [95% CI, 0.50-0.90] and 1.43 [95% CI, 1.11-1.85], respectively) with adjustment for clinical factors and B-type natriuretic peptides.

CONCLUSIONS

The cardiovascular proteome is associated with precision exercise phenotypes in HFpEF, suggesting novel mechanistic targets and potential methods for risk stratification to prevent HFpEF early in its pathogenesis.

Arterial Stiffness and Cardiorespiratory Fitness Impairment in the Community

Background During exercise, a healthy arterial system facilitates increased blood flow and distributes it effectively to essential organs. Accordingly, we sought to understand how arterial stiffening might impair cardiorespiratory fitness in community-dwelling individuals. Methods and Results Arterial tonometry and maximum effort cardiopulmonary exercise testing were performed on Framingham Heart Study participants (N=2898, age 54±9 years, 53% women, body mass index 28.1±5.3 kg/m2). We related 5 arterial stiffness measures (carotid-femoral pulse wave velocity [CFPWV]: a measure of aortic wall stiffness; central pulse pressure, forward wave amplitude, characteristic impedance: measures of pressure pulsatility; and augmentation index: a measure of relative wave reflection) to multidimensional exercise responses using linear models adjusted for age, sex, resting heart rate, habitual physical activity, and clinical risk factors. Greater CFPWV, augmentation index, and characteristic impedance were associated with lower peak oxygen uptake (VO2; all P<0.0001). We observed consistency of associations of CFPWV with peak oxygen uptake across age, sex, and cardiovascular risk profile (interaction P>0.05). However, the CFPWV-peak oxygen uptake relation was attenuated in individuals with obesity (P=0.002 for obesity*CFPWV interaction). Higher CPFWV, augmentation index, and characteristic impedance were also related to cardiopulmonary exercise testing measures reflecting adverse O2 kinetics and lower stroke volume and peripheral O2 extraction but not to ventilatory efficiency, a prognostic measure of right ventricular-pulmonary vascular performance. Conclusions Our findings delineate relations of arterial stiffness and cardiorespiratory fitness in community-dwelling individuals. Future studies are warranted to evaluate whether the physiological measures implicated here may represent potential targets for improving cardiorespiratory fitness in the general population.

Effect of Dapagliflozin on 6-Minute Walk Distance in Heart Failure With Preserved Ejection Fraction: PRESERVED-HF

BACKGROUND

Heart failure with preserved ejection fraction is associated with significant functional limitations, yet treatments for improving exercise performance have been elusive. We sought to explore the association between prespecified patient characteristics and changes in 6-minute walk distance that constitute a clinically significant response to dapagliflozin.

METHODS

We performed a responder analysis to understand patient characteristics associated with clinically meaningful improvement in 6-minute walk test (6MWT) distance ≥15 m among patients randomized to 12 weeks of dapagliflozin versus placebo in the double-blind PRESERVED-HF trial (Effects of Dapagliflozin on Biomarkers, Symptoms and Functional Status in Patients With Preserved Ejection Fraction Heart Failure).

RESULTS

A total of 289 randomized patients had 6MWT distance completed at baseline and 12 weeks. Patients randomized to dapagliflozin improved walking distance by ≥15 m more frequently than those on placebo (n=64, 44% versus n=48, 34%). After adjusting for baseline covariates, patients randomized to dapagliflozin were more likely to experience a clinically meaningful improvement in 6MWT distance compared with those that received placebo (adjusted odds ratio, 1.66 [95% CI, 1.00-2.75]; P=0.05). Dapagliflozin-treated patients were also less likely to have a ≥15 m reduction in 6MWT distance compared with placebo-treated patients (adjusted odds ratio, 0.56 [95% CI, 0.33-0.94]; P=0.03). These results were consistent across all prespecified subgroups (all P values for interaction were not significant).

CONCLUSIONS

Compared with those on placebo, patients with heart failure with preserved ejection fraction randomized to dapagliflozin were more likely to experience a clinically meaningful improvement and less likely to experience a deterioration in physical function over 12 weeks as measured by 6MWT distance. Beneficial response to dapagliflozin was consistent across prespecified subgroups.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT03030235.

Obesity-Related Biomarkers Are Associated With Exercise Intolerance and HFpEF

BACKGROUND

Obesity and adiposity are associated with an increased risk of heart failure with preserved ejection fraction (HFpEF); yet, specific underlying mechanisms remain unclear. We sought to examine the association of obesity-related biomarkers including adipokines (leptin, resistin, adiponectin), inflammatory markers (CRP [C-reactive protein], IL-6 [interleukin-6]), and insulin resistance (HOMA-IR) with HFpEF status, exercise capacity, and cardiovascular outcomes.

METHODS

We studied 509 consecutive patients with left ventricular ejection fraction ≥50% and chronic dyspnea, who underwent clinically indicated cardiopulmonary exercise test with invasive hemodynamic monitoring between 2006 and 2017. We defined HFpEF based on the presence of elevated left ventricular filling pressures at rest or during exercise. Fasting blood samples collected at the time of the cardiopulmonary exercise test were used to assay obesity-related biomarkers. We examined the association of log-transformed biomarkers with HFpEF status and exercise traits using multivariable-adjusted logistic regression models.

RESULTS

We observed associations of obesity-related biomarkers with measures of impaired exercise capacity including peak VO2 (P≤0.002 for all biomarkers). The largest effect size was seen with leptin, where a 1-SD higher leptin was associated with a 2.35 mL/kg per min lower peak VO2 (β, -2.35±0.19; P<0.001). In addition, specific biomarkers were associated with distinct measures of exercise reserve including blood pressure (homeostatic model assessment of insulin resistance, leptin, adiponectin; P≤0.002 for all), and chronotropic response (CRP, IL-6, homeostatic model assessment of insulin resistance, leptin, and resistin; P<0.05 for all). Our findings suggest that among the obesity-related biomarkers studied, higher levels of leptin and CRP are independently associated with increased odds of HFpEF, with odds ratios of 1.36 (95% CI, 1.09-1.70) and 1.25 (95% CI, 1.03-1.52), respectively.

CONCLUSIONS

Specific obesity-related pathways including inflammation, adipokine signaling, and insulin resistance may underlie the association of obesity with HFpEF and exercise intolerance.

Beyond VO2: the complex cardiopulmonary exercise test

Cardiopulmonary exercise test (CPET) is a valuable diagnostic tool with a specific application in heart failure (HF) thanks to the strong prognostic value of its parameters. The most important value provided by CPET is the peak oxygen uptake (peak VO2), the maximum rate of oxygen consumption attainable during physical exertion. According to the Fick principle, VO2 equals cardiac output (Qc) times the arteriovenous content difference [C(a-v)O2], where Ca is the arterial oxygen and Cv is the mixed venous oxygen content, respectively; therefore, VO2 can be reduced both by impaired O2 delivery (reduced Qc) or extraction (reduced arteriovenous O2 content). However, standard CPET is not capable of discriminating between these different impairments, leading to the need for 'complex' CPET technologies. Among non-invasive methods for Qc measurement during CPET, inert gas rebreathing and thoracic impedance cardiography are the most used techniques, both validated in healthy subjects and patients with HF, at rest and during exercise. On the other hand, the non-invasive assessment of peripheral muscle perfusion is possible with the application of near-infrared spectroscopy, capable of measuring tissue oxygenation. Measuring Qc allows, by having haemoglobin values available, to discriminate how much any VO2 deficit depends on the muscle, anaemia or heart.

Systemic Effects of Homoarginine Supplementation on Arginine Metabolizing Enzymes in Rats with Heart Failure with Preserved Ejection Fraction

A restoration of low homoarginine (hArg) levels in obese ZSF1 rats (O-ZSF1) before (S1-ZSF1) and after (S2-ZSF1) the manifestation of heart failure with preserved ejection fraction (HFpEF) did not affect the worsening of cardiac HFpEF characteristics. Here, potential regulation of key enzymes of arginine metabolism in other organs was analyzed. Arginase 2 (ARG2) was reduced >35% in the kidney and small intestine of hArg-supplemented rats compared to O-ZSF1. Glycine amidinotransferase (GATM) was 29% upregulated in the kidneys of S1-ZSF1. Dimethylarginine dimethylaminohydrolase 1 (DDAH1) levels were reduced >50% in the livers of O-ZSF1 but restored in S2-ZSF1 compared to healthy rats (L-ZSF1). In the skeletal muscle, iNOS was lower in O-ZSF1 and further decreased in S1-ZSF1 and S2-ZSF1 compared to L-ZSF1. iNOS levels were lower in the liver of the S2-ZSF1 group but higher in the kidneys of S1-ZSF1 compared to L-ZSF1. Supplementation with hArg in an in vivo HFpEF model resulted in the inhibition of renal ARG2 and an increase in GATM expression. This supplementation might contribute to the stabilization of intestinal iNOS and ARG2 imbalances, thereby enhancing barrier function. Additionally, it may offer protective effects in skeletal muscle by downregulating iNOS. In the conceptualization of hArg supplementation studies, the current disease progression stage as well as organ-specific enzyme regulation should be considered.

Acute Antipsychotic Use and Presence of Dysphagia Among Older Veterans with Heart Failure

OBJECTIVE

Examine whether new antipsychotic (AP) exposure is associated with dysphagia in hospitalized patients with heart failure (HF).

DESIGN

Retrospective cohort.

SETTINGS AND PARTICIPANTS

AP-naïve Veterans hospitalized with HF and subsequently discharged to a skilled nursing facility (SNF) between October 1, 2010, and November 30, 2019.

METHODS

We linked Veterans Health Administration (VHA) electronic medical records with Centers for Medicare & Medicaid (CMS) Minimum Data Set (MDS) version 3.0 assessments and CMS claims. The exposure variable was administration of ≥1 dose of a typical or atypical AP during hospitalization. Our main outcome measure was dysphagia presence defined by (1) inpatient dysphagia diagnosis codes and (2) the SNF admission MDS 3.0 swallowing-related items to examine post-acute care dysphagia status. Inverse probability of treatment weighting was used for risk adjustment.

RESULTS

The analytic cohort consisted of 29,591 Veterans (mean age 78.5 ± 10.0 years; female 2.9%; n = 865). Acute APs were administered to 9.9% (n = 2941). Those receiving APs had differences in prior dementia [37.1%, n = 1091, vs 22.3%, n = 5942; standardized mean difference (SMD) = 0.33] and hospital delirium diagnoses (7.7%, n = 227 vs 2.8%, n = 754; SMD = 0.22). Acute AP exposure was associated with nearly double the risk for hospital dysphagia diagnosis codes [adjusted (adj.) relative risk (RR) 1.9, 95% CI 1.8, 2.1]. At the SNF admission MDS assessment, acute AP administration during hospitalization was associated with an increased dysphagia risk (adj. RR 1.2, 95% CI 1.0, 1.5) both in the oral (adj. RR 1.7, 95% CI 1.2, 2.0) and pharyngeal phases (adj. RR 1.3, 95% CI 1.0, 1.7).

CONCLUSIONS AND IMPLICATIONS

In this retrospective study, AP medication exposure was associated with increased dysphagia coding and MDS assessment. Considering other adverse effects, acute AP should be cautiously administered during hospitalization, particularly in those with dementia. Swallowing function is critical to hydration, nutrition, and medical management of HF; therefore, when acute APs are initiated, a swallow evaluation should be considered.

Simultaneous exercise stress cardiac magnetic resonance and cardiopulmonary exercise testing to elucidate the Fick components of aerobic exercise capacity: a feasibility and reproducibility study and pilot study in hematologic cancer survivors

BACKGROUND

Patients treated for hematologic malignancy often experience reduced exercise capacity and increased fatigue; however whether this reduction is related to cardiac dysfunction or impairment of skeletal muscle oxygen extraction during activity is unknown. Cardiopulmonary exercise testing (CPET) coupled with stress cardiac magnetic resonance (ExeCMR), may provide a noninvasive method to identify the abnormalities of cardiac function or skeletal muscle oxygen extraction. This study was performed to determine the feasibility and reproducibility of a ExeCMR + CPET technique to measure the Fick components of peak oxygen consumption (VO2) and pilot its discriminatory potential in hematologic cancer patients experiencing fatigue.

METHODS

We studied 16 individuals undergoing ExeCMR to determine exercise cardiac reserve with simultaneous measures of VO2. The arteriovenous oxygen content difference (a-vO2diff) was calculated as the quotient of VO2/cardiac index (CI). Repeatability in measurements of peak VO2, CI, and a-vO2diff was assessed in seven healthy controls. Finally, we measured the Fick determinants of peak VO2 in hematologic cancer survivors with fatigue (n = 6) and compared them to age/gender-matched healthy controls (n = 6).

RESULTS

Study procedures were successfully completed without any adverse events in all subjects (N = 16, 100%). The protocol demonstrated good-excellent test-retest reproducibility for peak VO2 (intraclass correlation coefficient [ICC] = 0.992 [95%CI:0.955-0.999]; P < 0.001), peak CI (ICC = 0.970 [95%CI:0.838-0.995]; P < 0.001), and a-vO2diff (ICC = 0.953 [95%CI:0.744-0.992]; P < 0.001). Hematologic cancer survivors with fatigue demonstrated a significantly lower peak VO2 (17.1 [13.5-23.5] vs. 26.0 [19.7-29.5] mL·kg-1·min-1, P = 0.026) and lower peak CI (5.0 [4.7-6.3] vs. 7.4 [7.0-8.8] L·min-1/m2, P = 0.004) without a significant difference in a-vO2diff (14.4 [11.8-16.9] vs. 13.6 [10.9-15.4] mLO2/dL, P = 0.589).

CONCLUSIONS

Noninvasive measurement of peak VO2 Fick determinants is feasible and reliable with an ExeCMR + CPET protocol in those treated for a hematologic malignancy and may offer insight into the mechanisms of exercise intolerance in those experiencing fatigue.

Inflammation as a therapeutic target in heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) accounts for around half of all cases of heart failure and may become the dominant type of heart failure in the near future. Unlike HF with reduced ejection fraction there are few evidence-based treatment strategies available. There is a significant unmet need for new strategies to improve clinical outcomes in HFpEF patients. Inflammation is widely thought to play a key role in HFpEF pathophysiology and may represent a viable treatment target. In this review focusing predominantly on clinical studies, we will summarise the role of inflammation in HFpEF and discuss potential therapeutic strategies targeting inflammation.

Higher Work of Breathing During Exercise in Heart Failure With Preserved Ejection Fraction

BACKGROUND

It is unknown if pulmonary alterations in heart failure with preserved ejection fraction (HFpEF) impact respiratory mechanics during exercise.

RESEARCH QUESTION

Are the operating lung volumes, work of breathing (Wb), and power of breathing (Pb) abnormal in patients with HFpEF during exercise?

STUDY DESIGN AND METHODS

Patients with HFpEF (n = 8; median age, 71 years [interquartile range (IQR), 66-80 years]) and control participants (n = 9; median age, 68 years [IQR, 64-74 years]) performed incremental cycling to volitional exhaustion. Esophageal pressure, end-expiratory lung volume (EELV), inspiratory lung volume (EILV), and ventilatory variables were compared at similar absolute (30 and 50 L/min) and relative (45% of peak, 70% of peak, and 100% of peak) minute ventilation (V.E) during exercise.

RESULTS

During exercise, EELVs were not different between patients with HFpEF and control participants (P > .13 for all). EILVs were lower in patients with HFpEF than control participants at 45% and 70% V.E peak (P < .03 for all). Dynamic lung compliance was lower in patients with HFpEF than control participants at 30 L/min, 50 L/min, 45% V.E peak, and 100% V.E peak (P < .04 for all). Compared with control participants, patients with HFpEF showed higher total Wb and Pb at 30 L/min (Wb: median, 1.08 J/L [IQR, 0.93-1.82 J/L] vs 0.52 J/L [IQR, 0.43-0.71 J/L]; Pb: median, 36 J/min [IQR, 30-59 J/min] vs 17 J/min [IQR, 11-23 J/min] and 50 L/min; Wb: median, 1.40 J/L [IQR, 1.27-1.68 J/L] vs 0.90 J/L [IQR, 0.74-1.05 J/L]; Pb: median, 73 J/min [IQR, 60-83 J/min] vs 45 J/min [IQR, 33-63 J/min]; P < .01 for all). At 30 and 50 L/min, inspiratory and expiratory resistive Wb and Pb were higher in patients with HFpEF than control participants (P < .04 for all). Total Wb was higher for patients with HFpEF than control participants at 45% of V.E peak (P = .02). Total Pb was higher for control participants than patients with HFpEF at 100% V.E peak because of higher inspiratory resistive Pb (P < .04 for both).

INTERPRETATION

These data demonstrate the HFpEF syndrome is associated with pulmonary alterations eliciting a greater Pb during exercise resulting from greater inspiratory and expiratory resistive Pb.

Supervised Exercise Training for Chronic Heart Failure With Preserved Ejection Fraction: A Scientific Statement From the American Heart Association and American College of Cardiology

Heart failure with preserved ejection fraction (HFpEF) is one of the most common forms of heart failure; its prevalence is increasing, and outcomes are worsening. Affected patients often experience severe exertional dyspnea and debilitating fatigue, as well as poor quality of life, frequent hospitalizations, and a high mortality rate. Until recently, most pharmacological intervention trials for HFpEF yielded neutral primary outcomes. In contrast, trials of exercise-based interventions have consistently demonstrated large, significant, clinically meaningful improvements in symptoms, objectively determined exercise capacity, and usually quality of life. This success may be attributed, at least in part, to the pleiotropic effects of exercise, which may favorably affect the full range of abnormalities-peripheral vascular, skeletal muscle, and cardiovascular-that contribute to exercise intolerance in HFpEF. Accordingly, this scientific statement critically examines the currently available literature on the effects of exercise-based therapies for chronic stable HFpEF, potential mechanisms for improvement of exercise capacity and symptoms, and how these data compare with exercise therapy for other cardiovascular conditions. Specifically, data reviewed herein demonstrate a comparable or larger magnitude of improvement in exercise capacity from supervised exercise training in patients with chronic HFpEF compared with those with heart failure with reduced ejection fraction, although Medicare reimbursement is available only for the latter group. Finally, critical gaps in implementation of exercise-based therapies for patients with HFpEF, including exercise setting, training modalities, combinations with other strategies such as diet and medications, long-term adherence, incorporation of innovative and more accessible delivery methods, and management of recently hospitalized patients are highlighted to provide guidance for future research.

Cardiopulmonary exercise testing for heart failure: pathophysiology and predictive markers

Despite the numerous recent advancements in therapy, heart failure (HF) remains a principle cause of both morbidity and mortality. HF with preserved ejection fraction (HFpEF), a condition that shares the prevalence and adverse outcomes of HF with reduced ejection fraction, remains poorly recognised in its initial manifestations. Cardiopulmonary exercise testing (CPET), defined as a progressive work exercise test that includes non-invasive continuous measurement of cardiovascular and respiratory parameters, provides a reliable mode to evaluate for early features and for the assessment of prognostic features of both forms of HF. While CPET measurements are standard of care for advanced HF and transplant programmes, they merit a broader clinical application in the early diagnosis and assessment of patients with HFpEF. In this review, we provide an overview of the pathophysiology of exercise intolerance in HF and discuss key findings in CPETs used to evaluate both severity of impairment and the prognostic implications.

Determinants of exercise capacity in patients with heart failure without left ventricular hypertrophy

BACKGROUND

Determinants of exercise intolerance in a phenotype of heart failure with preserved ejection fraction (HFpEF) with normal left ventricular (LV) structure have not been fully elucidated.

METHODS

Cardiopulmonary exercise testing and exercise-stress echocardiography were performed in 44 HFpEF patients without LV hypertrophy. Exercise capacity was determined by peak oxygen consumption (peak VO₂). Doppler-derived cardiac output (CO), transmitral E velocity, systolic (LV-s') and early diastolic mitral annular velocities (e'), systolic pulmonary artery (PA) pressure (SPAP), tricuspid annular plane systolic excursion (TAPSE), and peak systolic right ventricular (RV) free wall velocity (RV-s') were measured at rest and exercise. E/e' and TAPSE/SPAP were used as an LV filling pressure parameter and RV-PA coupling, respectively.

RESULTS

During exercise, CO, LV-s', RV-s', e', and SPAP were significantly increased (p < 0.05 for all), whereas E/e' remained unchanged and TAPSE/SPAP was significantly reduced (p < 0.001). SPAP was higher and TAPSE/SPAP was lower at peak exercise in patients showing lower-half peak VO₂. In univariable analyses, LV-s' (R = 0.35, p = 0.022), SPAP (R = -0.40, p = 0.008), RV-s' (R = 0.47, p = 0.002), and TAPSE/SPAP (R = 0.42, p = 0.005) were significantly correlated with peak VO₂. In multivariable analyses, not only SPAP, but also TAPSE/SPAP independently determined peak VO₂ even after the adjustment for clinically relevant parameters.

CONCLUSIONS

In HFpEF patients without LV hypertrophy, altered RV-PA coupling by exercise could be associated with exercise intolerance, which might not be caused by elevated LV filling pressure.

The Need for Breathing Training Techniques: The Elephant in the Heart Failure Cardiac Rehabilitation Room: A Randomized Controlled Trial

BACKGROUND

Although solid evidence has indicated that respiratory symptoms are common amongst patients with chronic heart failure (CHF), state-of-the-art cardiac rehabilitation (CR) programs do not typically include management strategies to address respiratory symptoms. This study investigated the effect of the addition of breathing exercises (BE) to the CR programs in CHF.

METHODS

In a two parallel-arm randomized controlled study (RCT), 40 middle-aged patients with CHF and respiratory symptoms were recruited and randomized into two equal groups (n = 20); group (A): standard CR with BE and group (B): standard CR alone. Primary outcomes were respiratory parameters and secondary outcomes included cardiovascular and cardiopulmonary outcomes. All the participants attended a program of aerobic exercise (three sessions/week, 60-75% MHR, 45-55 min) for 12 weeks, plus educational, nutritional, and psychological counseling. Group (A) patients attended the same program together with BE using inspiratory muscle training (IMT) and breathing calisthenics (BC) (six sessions/week, 15-25 min) for the same duration.

RESULTS

There was a significant improvement in the respiratory outcomes, and most of the cardiovascular and cardiopulmonary outcomes in both groups with a greater change percentage in group A (p < 0.05).

CONCLUSIONS

These results indicate that the addition of BE to the CR programs in CHF is effective and is a "patient-centered" approach.

Inspiratory and leg muscle blood flows during inspiratory muscle metaboreflex activation in heart failure with preserved ejection fraction

The purpose of this study was to determine the cardiovascular consequences elicited by activation of the inspiratory muscle metaboreflex in patients with heart failure with preserved ejection fraction (HFpEF) and controls. Patients with HFpEF (n = 15; 69 ± 10 yr; 33 ± 4 kg/m2) and controls (n = 14; 70 ± 8 yr; 28 ± 4 kg/m2) performed an inspiratory loading trial at 60% maximal inspiratory pressure (PIMAX) until task failure. Mean arterial pressure (MAP) was measured continuously. Near-infrared spectroscopy and bolus injections of indocyanine green dye were used to determine the percent change in blood flow index (%ΔBFI) from baseline to the final minute of inspiratory loading in the vastus lateralis and sternocleidomastoid muscles. Vascular resistance index (VRI) was calculated. Time to task failure was shorter in HFpEF than in controls (339 ± 197 s vs. 626 ± 403 s; P = 0.02). Compared with controls, patients with HFpEF had a greater increase from baseline in MAP (16 ± 7 vs. 10 ± 6 mmHg) and vastus lateralis VRI (76 ± 45 vs. 32 ± 19%) as well as a greater decrease in vastus lateralis %ΔBFI (-32 ± 14 vs. -17 ± 9%) (all, P < 0.05). Sternocleidomastoid %ΔBFI normalized to absolute inspiratory pressure was higher in HFpEF compared with controls (8.0 ± 5.0 vs. 4.0 ± 1.9% per cmH2O·s; P = 0.03). These data indicate that patients with HFpEF exhibit exaggerated cardiovascular responses with inspiratory muscle metaboreflex activation compared with controls.NEW & NOTEWORTHY Respiratory muscle dysfunction is thought to contribute to exercise intolerance in heart failure with preserved ejection fraction (HFpEF); however, the underlying mechanisms are unknown. In the present study, patients with HFpEF had greater increases in leg muscle vascular resistance index and greater decreases in leg muscle blood flow index compared with controls during inspiratory resistive breathing (to activate the metaboreflex). Furthermore, respiratory muscle blood flow index responses normalized to pressure generation during inspiratory resistive breathing were exaggerated in HFpEF compared with controls.

Blood-Based Fingerprint of Cardiorespiratory Fitness and Long-Term Health Outcomes in Young Adulthood

Background Cardiorespiratory fitness is a powerful predictor of health outcomes that is currently underused in primary prevention, especially in young adults. We sought to develop a blood-based biomarker of cardiorespiratory fitness that is easily translatable across populations. Methods and Results Maximal effort cardiopulmonary exercise testing for quantification of cardiorespiratory fitness (by peak oxygen uptake) and profiling of >200 metabolites at rest were performed in the FHS (Framingham Heart Study; 2016-2019). A metabolomic fitness score was derived/validated in the FHS and was associated with long-term outcomes in the younger CARDIA (Coronary Artery Risk Development in Young Adults) study. In the FHS (derivation, N=451; validation, N=914; age 54±8 years, 53% women, body mass index 27.7±5.3 kg/m2), we used LASSO (least absolute shrinkage and selection operator) regression to develop a multimetabolite score to predict peak oxygen uptake (correlation with peak oxygen uptake r=0.77 in derivation, 0.61 in validation; both P<0.0001). In a linear model including clinical risk factors, a ≈1-SD higher metabolomic fitness score had equivalent magnitude of association with peak oxygen uptake as a 9.2-year age increment. In the CARDIA study (N=2300, median follow-up 26.9 years, age 32±4 years, 44% women, 44% Black individuals), a 1-SD higher metabolomic fitness score was associated with a 44% lower risk for mortality (hazard ratio [HR], 0.56 [95% CI, 0.47-0.68]; P<0.0001) and 32% lower risk for cardiovascular disease (HR, 0.68 [95% CI, 0.55-0.84]; P=0.0003) in models adjusted for age, sex, and race, which remained robust with adjustment for clinical risk factors. Conclusions A blood-based biomarker of cardiorespiratory fitness largely independent of traditional risk factors is associated with long-term risk of cardiovascular disease and mortality in young adults.