Exercise Intolerance in Patients With Heart Failure: JACC State-of-the-Art Review

Empagliflozin induces the transcriptional program for nutrient homeostasis in skeletal muscle in normal mice

Sodium-glucose cotransporter 2 inhibitors (SGLT2i) improve heart failure (HF) outcomes across a range of patient characteristics. A hypothesis that SGLT2i induce metabolic change similar to fasting has recently been proposed to explain their profound clinical benefits. However, it remains unclear whether SGLT2i primarily induce this change in physiological settings. Here, we demonstrate that empagliflozin administration under ad libitum feeding did not cause weight loss but did increase transcripts of the key nutrient sensors, AMP-activated protein kinase and nicotinamide phosphoribosyltransferase, and the master regulator of mitochondrial gene expression, PGC-1α, in quadriceps muscle in healthy mice. Expression of these genes correlated with that of PPARα and PPARδ target genes related to mitochondrial metabolism and oxidative stress response, and also correlated with serum ketone body β-hydroxybutyrate. These results were not observed in the heart. Collectively, this study revealed that empagliflozin activates transcriptional programs critical for sensing and adaptation to nutrient availability intrinsic to skeletal muscle rather than the heart even in normocaloric condition. As activation of PGC-1α is sufficient for metabolic switch from fatigable, glycolytic metabolism toward fatigue-resistant, oxidative mechanism in skeletal muscle myofibers, our findings may partly explain the improvement of exercise tolerance in patients with HF receiving empagliflozin.

Right Ventricular Function and Exercise Tolerance in Patients with ST-Elevation Myocardial Infarction

BACKGROUND

Following ST-segment elevation myocardial infarction (STEMI), patients with cardiac dysfunction have limitations in performing physical activity. Right ventricular (RV) function is a determinant in improving functional capacity, and cardiac rehabilitation (CR) is essential for this patient cohort.

OBJECTIVE

To evaluate the association of RV function with exercise tolerance after a CR program in patients with STEMI.

METHODS

Retrospective cohort study in patients with STEMI from January to December 2019. They underwent an echocardiographic assessment of RV function before a 16-session CR program. A cardiopulmonary exercise (CPX) testing was performed before and after the CR program. We analyzed whether RV function measured before CR was significantly associated with exercise tolerance before and after the CR program and the degree of improvement. Comorbidity, demographic and anatomic variables were documented. A p-value < 0.05 was considered statistically significant.

RESULTS

A total of 109 patients were included. Of all, 3.7% had global RV dysfunction, 10.1% had radial RV dysfunction, and 11% had longitudinal RV dysfunction. An association between radial or longitudinal RV dysfunction and the absence of improvement in cardiorespiratory fitness (> 1 peak VO2equivalents) was observed (p = 0.028, p = 0.008, respectively). A significant correlation was observed between longitudinal RV dysfunction with initial peak VO2equivalents (pVO2eq) (p = 0.046), final pVO2eq (p = 0.003), and difference in pVO2eq (p = 0.009). A correlation was also identified between global RV dysfunction and the initial pVO2eq (p = 0.045), final pVO2eq (p = 0.012), and difference in pVO2eq (p = 0.032).

CONCLUSIONS

RV dysfunction is associated with a lower capacity to exercise; CR programs can be extended or modified in these patients.

Contribution of hemoglobin concentration to cardiorespiratory fitness in black African American patients with recently decompensated heart failure and reduced ejection fraction

BACKGROUND

Previous studies have shown that patients with heart failure with reduced ejection fraction (HFrEF) and anemia have reduced peak oxygen consumption (VO2). Black or African American (B-AA) patients have a higher prevalence of anemia and are underrepresented in clinical studies of HFrEF. The aim of this study was to determine the contribution of hemoglobin to peak VO2 in B-AA patients recently hospitalized for acute decompensated HFrEF.

METHODS

We analyzed cardiopulmonary exercise testing (CPX) data measured within two weeks of discharge for acute decompensated HF in B-AA patients with HFrEF (left ventricular ejection fraction [LVEF] ≤40%) without severe anemia (Hb<8 g/dL). Blood samples were collected prior to CPX. Data are reported as median [interquartile range] and compared between groups with the Mann-Whitney, Chi-Square, and Spearman's rank tests.

RESULTS

We included 81 patients; 27 (33%) women, 57 [27-79] years of age, Body Mass Index of 33 [15-55] kg/m2 and LVEF of 30 [23-36] %. Hemoglobin ranged between 9.1 to 18.1 g/dL (median= 13.3 [11.9-14.5] g/dL); 26 (32%) were considered to have anemia based on a Hb concentration of males <13 g/dL and females <12 g/dL. Peak VO2 was lower in patients with anemia (11.8 [10.0-14.2] vs. 14.1 [10.6-17.0] mL·kg-1·min-1; P=0.010) with a significant correlation between peak VO2 and hemoglobin concentration (R=+0.455; P<0.001).

CONCLUSIONS

Anemia is prevalent among B-AA patients with recently decompensated HFrEF and appears to be a significant contributor to reductions in peak VO2.

Functional training improves peak oxygen consumption and quality of life of individuals with heart failure: a randomized clinical trial

BACKGROUND

Functional training may be an effective non-pharmacological therapy for heart failure (HF). This study aimed to compare the effects of functional training with strength training on peak VO₂ and quality of life in individuals with HF.

METHODS

A randomized, parallel-design and examiner-blinded controlled clinical trial with concealed allocation, intention-to-treat and per-protocol analyses. Twenty-seven participants with chronic HF were randomly allocated to functional or strength training group, to perform a 12-week physical training, three times per week, totalizing 36 sessions. Primary outcomes were the difference on peak VO₂ and quality of life assessed by cardiopulmonary exercise testing and Minnesota Living with Heart Failure Questionnaire, respectively. Secondary outcomes included functionality assessed by the Duke Activity Status Index and gait speed test, peripheral and inspiratory muscular strength, assessed by hand grip and manovacuometry testing, respectively, endothelial function by brachial artery flow-mediated dilation, and lean body mass by arm muscle circumference.

RESULTS

Participants were aged 60 ± 7 years, with left ventricular ejection fraction 29 ± 8.5%. The functional and strength training groups showed the following results, respectively: peak VO₂ increased by 1.4 ± 3.2 (16.9 ± 2.9 to 18.6 ± 4.8 mL.kg^-1.min^-1; p time = 0.011) and 1.5 ± 2.5 mL.kg^-1.min^-1 (16.8 ± 4.0 to 18.6 ± 5.5 mL.kg^-1.min^-1; p time = 0.011), and quality of life score decreased by 14 ± 15 (25.8 ± 14.8 to 10.3 ± 7.8 points; p time = 0.001) and 12 ± 28 points (33.8 ± 23.8 to 19.0 ± 15.1 points; p time = 0.001), but no difference was observed between groups (peak VO₂: p interaction = 0.921 and quality of life: p interaction = 0.921). The functional and strength training increased the activity status index by 6.5 ± 12 and 5.2 ± 13 points (p time = 0.001), respectively, and gait speed by 0.2 ± 0.3 m/s (p  time = 0.002) in both groups.

CONCLUSIONS

Functional and strength training are equally effective in improving peak VO₂, quality of life, and functionality in individuals with HF. These findings suggest that functional training may be a promising and innovative exercise-based strategy to treat HF.

TRIAL REGISTRATION

NCT03321682. Registered date: 26/10/2017.

Wildland fire, air pollution and cardiovascular health: is it time to focus on the microvasculature as a risk assessment tool?

Climate change favors weather conditions conducive to wildland fires. The intensity and frequency of forest fires are increasing, and fire seasons are lengthening. Exposure of human populations to smoke emitted by these fires increases, thereby contributing to airborne pollution through the emission of gas and particulate matter (PM). The adverse health outcomes associated with wildland fire exposure represent an important burden on the economies and health systems of societies. Even though cardiovascular diseases (CVDs) are the main of cause of the global burden of diseases attributable to PM exposure, it remains difficult to show reliable associations between exposure to wildland fire smoke and cardiovascular disease risk in population-based studies. Optimal health requires a resilient and adaptable network of small blood vessels, namely, the microvasculature. Often alterations of this microvasculature precede the occurrence of adverse health outcomes, including CVD. Biomarkers of microvascular health could then represent possible markers for the early detection of poor cardiovascular outcomes. This review aims to synthesize the current literature to gauge whether assessing the microvasculature can better estimate the cardiovascular impact of wildland fires.

Targeting gut microbiota-derived kynurenine to predict and protect the remodeling of the pressure-overloaded young heart

Pressure-overloaded left ventricular remodeling in young population is progressive and readily degenerate into heart failure. The aims of this study were to identify a plasma metabolite that predicts and is mechanistically linked to the disease. Untargeted metabolomics determined elevated plasma kynurenine (Kyn) in both the patient cohorts and the mice model, which was correlated with remodeling parameters. In vitro and in vivo evidence, combined with single-nucleus RNA sequencing (snRNA-seq), demonstrated that Kyn affected both cardiomyocytes and cardiac fibroblasts by activating aryl hydrocarbon receptors (AHR) to up-regulate hypertrophy- and fibrosis-related genes. Shotgun metagenomics and fecal microbiota transplantation revealed the existence of the altered gut microbiota-Kyn relationship. Supplementation of selected microbes reconstructed the gut microbiota, reduced plasma Kyn, and alleviated ventricular remodeling. Our data collectively discovered a gut microbiota-derived metabolite to activate AHR and its gene targets in remodeling young heart, a process that could be prevented by specific gut microbiota modulation.

Cardiopulmonary Exercise Testing, Rehabilitation, and Exercise Training in Postpulmonary Embolism

Long-term exercise intolerance and functional limitations are common after an episode of acute pulmonary embolism (PE), despite 3 to 6 months of anticoagulation. These persistent symptoms are reported in more than half of the patients with acute PE and are referred as "post-PE syndrome." Although these functional limitations can occur from persistent pulmonary vascular occlusion or pulmonary vascular remodeling, significant deconditioning can be a major contributing factor. Herein, the authors review the role of exercise testing to elucidate the mechanisms of exercise limitations to guide next steps in management and exercise training for musculoskeletal deconditioning.

Effects of aerobic exercise on cardiac function and gene expression of NADPH oxidases in diaphragm muscle of rats with aortic stenosis-induced heart failure

We evaluated the influence of aerobic physical exercise (EX) on gene-encoding proteins associated with oxidative stress in diaphragm muscle of rats with aortic stenosis-induced heart failure (HF). Wistar male rats were divided into four groups: Control sedentary (C); Control exercise (C-Ex); Sedentary aortic stenosis (AS); Aortic stenosis exercise (AS-Ex). Exercised rats trained 5 times a week for 10 weeks on a treadmill. Statistical analysis was performed by ANOVA or Kruskal-Wallis test. In the final echocardiogram, animals with aortic stenosis subjected to exercise demonstrated improvement in systolic function compared to the sedentary aortic stenosis group. In diaphragm muscle, the activity of antioxidant enzymes, malondialdehyde malondialdehyde concentration, protein carbonylation, and protein expression of p65 and its inhibitor IκB did not differ between groups. Alterations in gene expression of sources that generate reactive species of oxygen were observed in AS-Ex group, which showed decreased mRNA abundance of NOX2 and NOX4 compared to the aortic stenosis group (p < 0.05). We concluded that aerobic exercise has a positive impact during heart failure, ameliorating systolic dysfunction and biomarkers of oxidative stress in diaphragm muscle of rats with aortic stenosis-induced heart failure.

Application of non-invasive bioreactance to assess hemodynamic function in patients with hypertrophic cardiomyopathy

Non-invasive technologies have become popular for the clinical evaluation of cardiac function. The present study evaluated hemodynamic response to cardiopulmonary exercise stress testing using bioreactance technology in patients with hypertrophic cardiomyopathy. The study included 29 patients with HCM (age 55 ± 15 years; 28% female) and 12 age (55 ± 14 years), and gender matched (25% female) healthy controls. All participants underwent maximal graded cardiopulmonary exercise stress testing with simultaneous non-invasive hemodynamic bioreactance and gas exchange. At rest, patients with HCM demonstrated significantly lower cardiac output (4.1 ± 1.3 vs. 6.1 ± 1.2 L/min; p < 0.001), stroke volume (61.5 ± 20.8 vs. 89.5 ± 19.8 mL/beat; p < 0.001), and cardiac power output (0.97 ± 0.3 vs. 1.4 ± 0.3watt; p < 0.001), compared to controls. At peak exercise, the following hemodynamic and metabolic variables were lower in HCM patients that is, heart rate (118 ± 29 vs. 156 ± 20 beats/min; p < 0.001), cardiac output (15.5 ± 5.8 vs. 20.5 ± 4.7 L/min; p = 0.017), cardiac power output (4.3 ± 1.6 vs. 5.9 ± 1.8 watts; p = 0.017), mean arterial blood pressure (126 ± 11 vs. 134 ± 10 mmHg; p = 0.039), and oxygen consumption (18.3 ± 6.0 vs. 30.5 ± 8.3 mL/kg/min; p < 0.001), respectively. Peak arteriovenous oxygen difference and stroke volume were not significantly different between HCM patients and healthy controls (11.2 ± 6.4 vs. 11.9 ± 3.1 mL/100 mL, p = 0.37 and 131 ± 50.6 vs. 132 ± 41.9 mL/beat, p = 0.76). There was a moderate positive relationship between peak oxygen consumption and peak heart rate (r = 0.67, p < 0.001), and arteriovenous oxygen difference (r = 0.59, p = 0.001). Functional capacity is significantly reduced in patients with HCM primarily due to diminished central (cardiac) rather than peripheral factors. Application of non-invasive hemodynamic assessment may improve understanding of the pathophysiology and explain mechanisms of exercise intolerance in hypertrophic cardiomyopathy.

Impact of polyphenols on heart failure and cardiac hypertrophy: clinical effects and molecular mechanisms

Polyphenols are abundant in regular diets and possess antioxidant, anti-inflammatory, anti-cancer, neuroprotective, and cardioprotective effects. Regarding the inadequacy of the current treatments in preventing cardiac remodeling following cardiovascular diseases, attention has been focused on improving cardiac function with potential alternatives such as polyphenols. The following online databases were searched for relevant orginial published from 2000 to 2023: EMBASE, MEDLINE, and Web of Science databases. The search strategy aimed to assess the effects of polyphenols on heart failure and keywords were "heart failure" and "polyphenols" and "cardiac hypertrophy" and "molecular mechanisms". Our results indicated polyphenols are repeatedly indicated to regulate various heart failure-related vital molecules and signaling pathways, such as inactivating fibrotic and hypertrophic factors, preventing mitochondrial dysfunction and free radical production, the underlying causes of apoptosis, and also improving lipid profile and cellular metabolism. In the current study, we aimed to review the most recent literature and investigations on the underlying mechanism of actions of different polyphenols subclasses in cardiac hypertrophy and heart failure to provide deep insight into novel mechanistic treatments and direct future studies in this context. Moreover, due to polyphenols' low bioavailability from conventional oral and intravenous administration routes, in this study, we have also investigated the currently accessible nano-drug delivery methods to optimize the treatment outcomes by providing sufficient drug delivery, targeted therapy, and less off-target effects, as desired by precision medicine standards.

Effect of optimized new Shengmai powder on exercise tolerance in rats with heart failure by regulating the ubiquitin-proteasome signaling pathway

Introduction

Decreased exercise tolerance is a common symptom in patients with heart failure, which is closely related to protein degradation and apoptosis regulated by the ubiquitin-proteasome signaling (UPS) pathway. In this study, the effect of Chinese medicine, optimized new Shengmai powder, on exercise tolerance in rats with heart failure was investigated via the UPS pathway.

Methods

The heart failure model was prepared by ligating the left anterior descending branch of the coronary artery in rats, in which the sham-operated group was only threaded and not ligated. Rats (left ventricular ejection fraction ≤ 45%) were randomly divided into the following groups: model group, YHXSMS group, Benazepril group, and proteasome inhibitor Oprozomib group, and they were administered the corresponding drugs by gavage for 4 weeks. The cardiac function of rats was evaluated by performing an echocardiography examination and a hemodynamic test and the exercise tolerance was done by conducting an exhaustive swimming test. The mechanism was revealed by TUNEL detection, immunohistochemistry, immunofluorescence analysis, Western blot, and quantitative real-time PCR.

Results

The study showed that there was a decrease in cardiac function and exercise tolerance of rats in the model group and also destruction of cardiac and skeletal muscle fibers, a proliferation of collagen tissue, and an increment of apoptosis. Our study suggested that optimized new Shengmai powder could exert antiapoptotic effects on myocardial and skeletal muscle cells and improve myocardial contractility and exercise tolerance by inhibiting the overactivation of the UPS pathway, downregulating MAFbx, and Murf-1 overexpression, inhibiting the activation of the JNK signaling pathway, upregulating bcl-2 expression, and decreasing bax and caspase-3 levels.

Conclusions

The study showed that the optimized new Shengmai powder could improve cardiac function and exercise tolerance in rats with heart failure through the UPS pathway.

Sarcopenia and Cardiovascular Diseases

Sarcopenia is the loss of muscle strength, mass, and function, which is often exacerbated by chronic comorbidities including cardiovascular diseases, chronic kidney disease, and cancer. Sarcopenia is associated with faster progression of cardiovascular diseases and higher risk of mortality, falls, and reduced quality of life, particularly among older adults. Although the pathophysiologic mechanisms are complex, the broad underlying cause of sarcopenia includes an imbalance between anabolic and catabolic muscle homeostasis with or without neuronal degeneration. The intrinsic molecular mechanisms of aging, chronic illness, malnutrition, and immobility are associated with the development of sarcopenia. Screening and testing for sarcopenia may be particularly important among those with chronic disease states. Early recognition of sarcopenia is important because it can provide an opportunity for interventions to reverse or delay the progression of muscle disorder, which may ultimately impact cardiovascular outcomes. Relying on body mass index is not useful for screening because many patients will have sarcopenic obesity, a particularly important phenotype among older cardiac patients. In this review, we aimed to: (1) provide a definition of sarcopenia within the context of muscle wasting disorders; (2) summarize the associations between sarcopenia and different cardiovascular diseases; (3) highlight an approach for a diagnostic evaluation; (4) discuss management strategies for sarcopenia; and (5) outline key gaps in knowledge with implications for the future of the field.

Prognostic Value of Spot Urinary Creatinine Concentration and Its Relationship with Body Composition Parameters in HF Patients

BACKGROUND

Low 24-h urinary excretion of creatinine in patients with heart failure (HF) is believed to reflect muscle wasting and is associated with a poor prognosis. Recently, spot urinary creatinine concentration (SUCR) has been suggested as a useful prognostic factor in selected HF cohorts. This more practical and cheaper approach has never been tested in an unselected HF population. Moreover, neither the relation between SUCR and body composition markers nor the association of SUCR with the markers of volume overload, which are known to worsen clinical outcome, has been studied so far. The aim of the study was to check the prognostic value of SUCR in HF patients after adjusting for body composition and indirect markers of volume overload.

METHODS

In 911 HF patients, morning SUCR was determined and body composition scanning using dual X-ray absorptiometry (DEXA) was performed. Univariable and multivariable predictors of log SUCR were analyzed. All participants were divided into quartiles of SUCR.

RESULTS

In univariable analysis, SUCR weakly correlated with fat-free mass (R = 0.09, p = 0.01). Stronger correlations were shown between SUCR and loop diuretic dose (R = 0.16, p < 0.0001), NTproBNP (R = -0.15, p < 0.0001) and serum sodium (R = 0.16, p < 0.0001). During 3 years of follow-up, 353 (38.7%) patients died. Patients with lower SUCR were more frequently female, and their functional status was worse. The lowest mortality was observed in the top quartile of SUCR. In the unadjusted Cox regression analysis, the relative risk of death in all three lower quartiles of SUCR was higher by roughly 80% compared to the top SUCR quartile. Apart from lower SUCR, the significant predictors of death were age and malnutrition but not body composition. After adjustment for loop diuretic dose and percent of recommended dose of mineralocorticoid receptor antagonists, the difference in mortality vanished completely.

CONCLUSIONS

Lower SUCR levels in HF patients are associated with a worse outcome, but this effect is not correlated with fat-free mass. Fluid overload-driven effects may link lower SUCR with higher mortality in HF.

Combining cardiopulmonary exercise testing with echocardiography: a multiparametric approach to the cardiovascular and cardiopulmonary systems

Exercise intolerance is a prominent feature of several cardiovascular conditions. However, the physical effort requires the intertwined adaptation of several factors, namely the cardiovascular system, the lungs, and peripheral muscles. Several abnormalities in each domain may be present in a given patient. Cardiopulmonary exercise testing (CPET) has been used to investigate metabolic and ventilatory alterations responsible for exercise intolerance but does not allow for direct evaluation of cardiovascular function. However, this can readily be obtained by concomitant exercise-stress echocardiography (ESE). The combined CPET-ESE approach allows for precise and thorough phenotyping of the pathophysiologic mechanisms underpinning exercise intolerance. Thus, it can be used to refine the diagnostic workup of patients with dyspnoea of unknown origin, as well as improve risk stratification and potentially guide the therapeutic approach in specific conditions, including left and right heart failure or valvular heart disease. However, given its hitherto sporadic use, both the conceptual and technical aspects of CPET-ESE are often poorly known by the clinician. Improving knowledge in this field could significantly aid in anticipating individual disease trajectories and tailoring treatment strategies accordingly. Therefore, we designed this review to revise the pathophysiologic correlates of exercise intolerance, the practical principles of the combined CPET-ESE examination, and its main applications according to current literature.

Prognostic Value of Self-Reported Subjective Exercise Capacity in Patients With Acute Dyspnea

Background

Self-reported exercise capacity is a well-established prognostic measure in stable ambulatory patients with cardiac and pulmonary disease.

Objectives

The authors aimed to directly compare the prognostic accuracy of quantified self-reported exercise capacity using the Duke Activity Status Index (DASI) with the established objective disease-severity marker B-type natriuretic peptide (BNP) in patients presenting with acute dyspnea to the emergency department.

Methods

The DASI was obtained in a prospective multicenter diagnostic study recruiting unselected patients presenting with acute dyspnea to the emergency department. The prognostic accuracy of DASI and BNP for 90-day and 720-day all-cause mortality was evaluated using C-index.

Results

Among 1,019 patients eligible for this analysis, 75 (7%) and 297 (29%) patients died within 90 and 720 days after presentation, respectively. Unadjusted hazard ratios (HRs) and multivariable adjusted hazard ratios (aHRs) for 90- and 720-day mortality increased continuously from the fourth (best self-reported exercise capacity) to the first DASI quartile (worst self-reported exercise capacity). For 720-day mortality the HR of the first quartile vs the fourth was 9.1 (95% CI, 5.5-14.9) vs (aHR: 6.1, 95% CI: 3.7-10.1), of the second quartile 6.4 (95% CI: 3.9-10.6) vs (aHR: 4.4, 95% CI: 2.6-7.3), while of the third quartile the HR was 3.2 (95% CI: 1.9-5.5) vs (aHR: 2.4, 95% CI: 1.4-4.0). The prognostic accuracy of the DASI score was high, and higher than that of BNP concentrations (720-day mortality C-index: 0.67 vs 0.62; P = 0.024).

Conclusions

Quantification of self-reported subjective exercise capacity using the DASI provides high prognostic accuracy and may aid physicians in risk stratification. (Basics in Acute Shortness of Breath EvaLuation [BASEL V] Study [BASEL V]; NCT01831115).

Influence of Isolated Resistance Exercise on Cardiac Remodeling, Myocardial Oxidative Stress, and Metabolism in Infarcted Rats

INTRODUCTION

Exercise is an important therapeutic strategy for preventing and treating myocardial infarction (MI)-induced cardiac remodeling and heart failure. However, the myocardial effects of resistance exercise on infarcted hearts are not completely established. In this study, we investigated the effects of resistance exercise on structural, functional, and molecular cardiac alterations in infarcted rats.

METHODS

Three months after MI induction or simulated surgery, Wistar rats were assigned into three groups: Sham (n = 14); MI (n = 9); and exercised MI (MI-Ex, n = 13). Exercised rats performed, 3 times a week for 12 weeks, four climbs on a ladder with progressive loads. Cardiac structure and left ventricle (LV) function were analyzed by echocardiogram. Myocyte diameters were evaluated in hematoxylin- and eosin-stained histological sections as the smallest distance between borders drawn across the nucleus. Myocardial energy metabolism, lipid hydroperoxide, malondialdehyde, protein carbonylation, and antioxidant enzyme activities were evaluated by spectrophotometry. Gene expressions of NADPH oxidase subunits were evaluated by RT-PCR. Statistical analyses were performed using ANOVA and Tukey or Kruskal-Wallis and Dunn's test.

RESULTS

Mortality did not differ between the MI-Ex and MI groups. MI had dilated left atrium and LV, with LV systolic dysfunction. Exercise increased the maximum load-carrying capacity, with no changes in cardiac structure or LV function. Myocyte diameters were lower in MI than in Sham and MI-Ex. Lactate dehydrogenase and creatine kinase activity were lower in MI than in Sham. Citrate synthase and catalase activity were lower in MI and MI-Ex than in Sham. Lipid hydroperoxide concentration was lower in MI-Ex than in MI. Nox2 and p22phox gene expressions were higher in MI-Ex than in Sham. Gene expression of Nox4 was higher in MI and MI-Ex than in Sham, and p47phox was lower in MI than in Sham.

CONCLUSION

Late resistance exercise was safe in infarcted rats. Resistance exercise improved maximum load-carrying capacity, reduced myocardial oxidative stress, and preserved myocardial metabolism, with no changes in cardiac structure or left ventricle function in infarcted rats.

Cardiovascular disease, muscle function, and long-term falls risk: The Perth Longitudinal Study of Ageing Women

BACKGROUND

A few cross-sectional studies have highlighted inconsistent associations between cardiovascular disease (CVD) and musculoskeletal conditions. We sought to investigate the relationship between clinical CVD including subtypes, compromised muscle function, as well as incident self-reported and injurious falls in older women.

MATERIALS AND METHODS

1431 community-dwelling older women (mean age ± SD; 75.2 ± 2.7 years) were included in over 14.5 years of a prospective study, the Perth Longitudinal Study of Ageing in Women. CVD (up to 18-years prior to the baseline visit) and injurious fall hospitalizations over 14.5 years were obtained from linked health records. Self-reported falls for five years were obtained via a written adverse event diary posted every four months. Timed-Up-and-Go (TUG) test and hand grip strength were used to assess mobility and muscle strength, respectively. Mobility impairment was defined as TUG performance >10.2 sec and muscle weakness characterized as grip strength <22 kg.

RESULTS

Over 5-years, 411 (28.7%) women reported a falls, while 567 (39.6%) were hospitalized due to an injurious fall over 14.5 years. Prior CVD events were associated with 32% (HR 1.32 95%CI, 1.06-1.64) and 29% (HR 1.29 95%CI, 1.07-1.56) increased risk of self-reported and injurious falls, respectively, in multivariable-adjusted models. When considering subtypes of CVD, only cerebrovascular disease was related to self-reported (HR 1.77; 95%CI, 1.15-2.72) and injurious falls requiring hospitalization (HR 1.51; 95%CI, 1.00-2.27). CVD was also associated with cross-sectional and prospective mobility impairments. However, no evidence for such relationships was observed for muscle weakness.

CONCLUSIONS

Prevalent CVD events, particularly cerebrovascular disease, are related to an increased risk of long-term falls. These findings highlight the need to recognize increased falls risk in patients with CVD. Further, there is a need to understand whether incorporating prevalent CVD into falls screening tools improves risk stratification or affects model calibration.

From MIA to FIFA: The vicious matrix of frailty, inflammation, fluid overload and atherosclerosis in peritoneal dialysis

Cardiovascular disease (CVD) is a major cause of mortality and morbidity in peritoneal dialysis (PD) patients. Two decades ago, the common co-existence of malnutrition and systemic inflammation PD patients with atherosclerosis and CVD led to the proposed terminology of 'malnutrition-inflammation-atherosclerosis (MIA) syndrome'. Although the importance of malnutrition is well accepted, frailty represents a more comprehensive assessment of the physical and functional capability of the patient and encompasses the contributions of sarcopenia (a key component of malnutrition), obesity, cardiopulmonary as well as neuropsychiatric impairment. In recent years, it is also increasingly recognized that fluid overload is not only the consequence but also play an important role in the pathogenesis of CVD. Moreover, fluid overload is closely linked with the systemic inflammatory status, presumably by gut oedema, gastrointestinal epithelial barrier dysfunction and leakage of bacterial fragments to the systemic circulation. There are now a wealth of published evidence to show intricate relations between frailty, inflammation, fluid overload and atherosclerotic disease in patients with chronic kidney disease (CKD) and those on PD, a phenomenon that we propose the term 'FIFA complex'. In this system, frailty and atherosclerotic disease may be regarded as two patient-oriented outcomes, while inflammation and fluid overload are two inter-connected pathogenic processes. However, there remain limited data on how the treatment of one component affect the others. It is also important to define how treatment of fluid overload affect the systemic inflammatory status and to develop effective anti-inflammatory strategies that could alleviate atherosclerotic disease and frailty.

Deep phenotype characterization of hypertensive response to exercise: implications on functional capacity and prognosis across the heart failure spectrum

AIMS

Limited evidence is available regarding the role of hypertensive response to exercise (HRE) in heart failure (HF). We evaluated the systolic blood pressure (SBP) to workload slope during exercise across the HF spectrum, investigating haemodynamic and prognostic correlates of HRE.

METHODS AND RESULTS

We prospectively enrolled 369 patients with HF Stage C (143 had preserved [HFpEF], and 226 reduced [HFrEF] ejection fraction), 201 subjects at risk of developing HF (HF Stages A-B), and 58 healthy controls. We performed a combined cardiopulmonary exercise stress echocardiography testing. We defined HRE as the highest sex-specific SBP/workload slope tertile in each HF stage. Median SBP/workload slope was 0.53 mmHg/W (interquartile range 0.36-0.72); the slope was 39% steeper in women than men (p < 0.0001). After adjusting for age and sex, SBP/workload slope in HFrEF (0.47, 0.30-0.63) was similar to controls (0.43, 0.35-0.57) but significantly lower than Stages A-B (0.61, 0.47-0.75) and HFpEF (0.63, 0.42-0.86). Patients with HRE showed significantly lower peak oxygen consumption and peripheral oxygen extraction. After a median follow-up of 16 months, HRE was independently associated with adverse outcomes (all-cause mortality and hospitalization for cardiovascular reasons: hazard ratio 2.05, 95% confidence interval 1.81-5.18), while rest and peak SBP were not. Kaplan-Meier analysis confirmed a worse survival probability in Stages A-B (p = 0.005) and HFpEF (p < 0.001), but not HFrEF.

CONCLUSION

A steeper SBP/workload slope is associated with impaired functional capacity across the HF spectrum and could be a more sensitive predictor of adverse events than absolute SBP values, mainly in patients in Stages A-B and HFpEF.

WGCNA combined with machine learning algorithms for analyzing key genes and immune cell infiltration in heart failure due to ischemic cardiomyopathy

Background

Ischemic cardiomyopathy (ICM) induced heart failure (HF) is one of the most common causes of death worldwide. This study aimed to find candidate genes for ICM-HF and to identify relevant biomarkers by machine learning (ML).

Methods

The expression data of ICM-HF and normal samples were downloaded from Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) between ICM-HF and normal group were identified. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment and gene ontology (GO) annotation analysis, protein–protein interaction (PPI) network, gene pathway enrichment analysis (GSEA), and single-sample gene set enrichment analysis (ssGSEA) were performed. Weighted gene co-expression network analysis (WGCNA) was applied to screen for disease-associated modules, and relevant genes were derived using four ML algorithms. The diagnostic values of candidate genes were assessed using receiver operating characteristic (ROC) curves. The immune cell infiltration analysis was performed between the ICM-HF and normal group. Validation was performed using another gene set.

Results

A total of 313 DEGs were identified between ICM-HF and normal group of GSE57345, which were mainly enriched in biological processes and pathways related to cell cycle regulation, lipid metabolism pathways, immune response pathways, and intrinsic organelle damage regulation. GSEA results showed positive correlations with pathways such as cholesterol metabolism in the ICM-HF group compared to normal group and lipid metabolism in adipocytes. GSEA results also showed a positive correlation with pathways such as cholesterol metabolism and a negative correlation with pathways such as lipolytic presentation in adipocytes compared to normal group. Combining multiple ML and cytohubba algorithms yielded 11 relevant genes. After validation using the GSE42955 validation sets, the 7 genes obtained by the machine learning algorithm were well verified. The immune cell infiltration analysis showed significant differences in mast cells, plasma cells, naive B cells, and NK cells.

Conclusion

Combined analysis using WGCNA and ML identified coiled-coil-helix-coiled-coil-helix domain containing 4 (CHCHD4), transmembrane protein 53 (TMEM53), acid phosphatase 3 (ACPP), aminoadipate-semialdehyde dehydrogenase (AASDH), purinergic receptor P2Y1 (P2RY1), caspase 3 (CASP3) and aquaporin 7 (AQP7) as potential biomarkers of ICM-HF. ICM-HF may be closely related to pathways such as mitochondrial damage and disorders of lipid metabolism, while the infiltration of multiple immune cells was identified to play a critical role in the progression of the disease.

Prognostic Significance of Peak Workload-to-Weight Ratio by Cardiopulmonary Exercise Testing in Chronic Heart Failure

The prognostic impact of peak workload-to-weight ratio (PWR) during cardiopulmonary exercise testing (CPET) and its determinants in patients with chronic heart failure (CHF) are not well understood. Consecutive 514 patients with CHF referred for CPET at the Hokkaido University Hospital between 2013 and 2018 were identified. The primary outcome was a composite of hospitalization because of worsening heart failure and death. PWR was calculated as peak workload normalized to body weight (W/kg) by CPET. Patients with low PWR (cut-off median 1.38 [W/kg], n = 257) were older and more anemic than those with high PWR (n = 257). In CPET, patients with low PWR displayed reduced peak oxygen consumption and impaired ventilatory efficiency compared with those with high PWR, whereas the peak respiratory exchange ratio was not significantly different between the 2 groups. There were 89 patients with events over a median follow-up period of 3.3 (interquartile range 0.8 to 5.5) years. The incidence of composite events was significantly higher in patients with low PWR than in those with high PWR (log-rank p <0.0001). In the multivariable Cox regression, lower PWR was associated with adverse events (hazard ratio 0.31, 95% confidence interval 0.13 to 0.73, p = 0.008). Low hemoglobin concentration was strongly related to impaired PWR (β coefficient = 0.43, per 1 g/100 ml increased, p <0.0001). In conclusion, PWR was associated with worse clinical outcomes, where blood hemoglobin was strongly related to PWR. Further study is required to identify therapies targeting peak workload achievements in exercise stress tests to improve the outcome in patients with CHF.

Test Retest Reliability and Validity of 1-Minute Sit-to-Stand Test in Patients With Chronic Heart Failure

AIM

The psychometric properties of the 1-minute sit-to-stand (1STS) test have not been investigated in patients with chronic heart failure (CHF). The aim of this study was to evaluate test-retest reliability, construct validity, and minimal detectable change of the 1STS test and to investigate the physiological response to the 1STS test in patients with CHF.

METHOD

Forty-three (43) patients with CHF were included. Demographic and clinical features were recorded. To investigate test-retest reliability, participants performed two 1STS tests on the same day. The correlations between the 1STS test and the 6-minute walk test (6MWT), functional class, pulmonary function, quadriceps muscle strength, and physical activity were investigated for validity. The physiological responses and symptom perception were assessed before and after both the 1STS test and 6MWT.

RESULTS

Excellent test-retest reliability was found for the 1STS test, with an intraclass correlation of 0.932 (95% confidence interval 0.874-0.963). The minimal detectable change of the 1STST test was 3.7 repetitions. The 1STS test was correlated with 6MWT distance, age, functional class, pulmonary function, quadriceps muscle strength, and physical activity (p<0.05). The 1STS test showed similar changes to the 6MWT in physiological responses and symptom perception (p>0.05), except for leg fatigue (p=0.02).

CONCLUSIONS

The 1STS test is reliable and valid in evaluating functional exercise capacity in patients with CHF. The 1STS test reveals similar cardiac demand to the 6MWT. The 1STS test may be considered an option when traditional tests are impractical in terms of space and time.

Effects and Optimal Dose of Exercise on Endothelial Function in Patients with Heart Failure: A Systematic Review and Meta-Analysis

BACKGROUND

Exercise-based cardiac rehabilitation (CR) is considered an effective treatment for enhancing endothelial function in patients with heart failure (HF). However, recent studies have been published and the optimal "dose" of exercise required to increase the benefits of exercise-based CR programmes on endothelial function is still unknown.

OBJECTIVES

(a) To estimate the effect of exercise-based CR on endothelial function, assessed by flow-mediated dilation (FMD), in patients with HF; (b) to determine whether high-intensity interval training (HIIT) is better than moderate-intensity training (MIT) for improving FMD; and (c) to investigate the influence of exercise modality (i.e. resistance exercise vs. aerobic exercise and combined exercise vs. aerobic exercise) on the improvement of endothelial function.

METHODS

Electronic searches were carried out in PubMed, Embase, and Scopus up to February 2022. Random-effects models of between-group mean differences were estimated. Heterogeneity analyses were performed by means of the chi-square test and I² index. Subgroup analyses and meta-regressions were used to test the influence of potential moderator variables on the effect of exercise.

RESULTS

We found a FMD increase of 3.09% (95% confidence interval [CI] = 2.01, 4.17) in favour of aerobic-based CR programmes compared with control groups in patients with HF and reduced ejection fraction (HFrEF). However, the results of included studies were inconsistent (p < .001; I² = 95.2%). Higher FMD improvement was found in studies which were randomised, reported radial FMD, or performed higher number of training sessions a week. Moreover, HIIT enhanced FMD to a greater extent than MIT (2.35% [95% CI = 0.49, 4.22]) in patients with HFrEF. Insufficient data prevented pooled analyses for the effect of exercise in patients with HF and preserved ejection fraction and the influence of exercise modality on the improvement of endothelial function.

CONCLUSION

Aerobic-based CR is a non-pharmacological treatment for enhancing endothelial function in patients with HFrEF. However, higher training frequency and HIIT induce greater adaptation of endothelial function in these patients, which should betaken into consideration when designing exercise-based CR programmes. Trial registration The protocol was prospectively registered on the PROSPERO database (CRD42022304687).

Inflammatory pathways in heart failure with preserved left ventricular ejection fraction: implications for future interventions

Many patients with symptoms and signs of heart failure have a left ventricular ejection fraction ≥50%, termed heart failure with preserved ejection fraction (HFpEF). HFpEF is a heterogeneous syndrome mainly affecting older people who have many other cardiac and non-cardiac conditions that often cast doubt on the origin of symptoms, such as breathlessness, or signs, such as peripheral oedema, rendering them neither sensitive nor specific to the diagnosis of HFpEF. Currently, management of HFpEF is mainly directed at controlling symptoms and treating comorbid conditions such as hypertension, atrial fibrillation, anaemia, and coronary artery disease. HFpEF is also characterized by a persistent increase in inflammatory biomarkers. Inflammation may be a key driver of the development and progression of HFpEF and many of its associated comorbidities. Detailed characterization of specific inflammatory pathways may provide insights into the pathophysiology of HFpEF and guide its future management. There is growing interest in novel therapies specifically designed to target deregulated inflammation in many therapeutic areas, including cardiovascular disease. However, large-scale clinical trials investigating the effectiveness of anti-inflammatory treatments in HFpEF are still lacking. In this manuscript, we review the role of inflammation in HFpEF and the possible implications for future trials.

The effect of SGLT-2 inhibitors on cardiorespiratory fitness capacity: A systematic review and meta-analysis

Objective: The study aimed to evaluate the effect of sodium-glucose transporter 2 (SGLT-2) inhibitors on various parameters of exercise capacity and provide an evidence-based basis for type 2 diabetes mellitus (T2DM) combined with heart failure (HF) patients or HF patients without T2DM who use SGLT-2 inhibitors to improve cardiorespiratory fitness (CRF). Methods: According to the participant, intervention, comparison, and outcome (PICO) elements, the effects of SGLT-2 inhibitor administration on VO₂ or VO₂peak were researched in this study. Weighted mean difference (WMD) and 95% confidence intervals (CIs) were calculated (random-effects model). Heterogeneity was assessed by the I² test. Results: Six studies were included according to the eligibility criteria: four were RCTs, and two were non-RCTs. Compared with the control group, the merge results of RCTs showed that SGLT-2 inhibitors could significantly increase the VO₂peak (WMD, 2.02 ml kg^-1 min^-1, 95% CI: 0.68-3.37, and p = 0.03; I² = 0% and p = 0.40) and VAT (WMD, 1.57 ml kg^-1 min^-1, 95% CI: 0.06-3.07, and p = 0.04; I² = 0% and p = 0.52) of the obese population, patients with T2DM, and chronic HF patients with or without T2DM. Subgroup analysis showed that SGLT-2 inhibitors improved the VO₂peak in non-HF patients (WMD, 3.57 ml kg^-1 min^-1, 95% CI: 0.87-6.26, and p = 0.009; I² = 4% and p = 0.31) more than in HF patients (WMD, 1.46 ml kg^-1 min^-1, 95% CI: -0.13-3.04, and p = 0.07; I² = 0% and p = 0.81). Moreover, the merge of single-arm studies also indicated that empagliflozin could improve VO₂peak (MD, 1.11 ml kg^-1 min^-1, 95% CI: 0.93-1.30, and p = 0.827, Δ p = 0.000 and I² = 0%) of T2DM patients with chronic HF. Conclusion: Despite the limited number of studies and samples involved, the meta-analysis preliminarily demonstrated that SGLT-2 inhibitors could improve some parameters of exercise capacity (VO₂peak, VAT) in chronic HF patients with or without T2DM and obese individuals, which had a positive effect on promoting cardiopulmonary fitness to help these populations improve their prognosis. Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/#recordDetails], identifier [CRD42020202788].

Sympathetic and hemodynamic responses to exercise in heart failure with preserved ejection fraction

Excessive sympathetic activity during exercise causes heightened peripheral vasoconstriction, which can reduce oxygen delivery to active muscles, resulting in exercise intolerance. Although both patients suffering from heart failure with preserved and reduced ejection fraction (HFpEF and HFrEF, respectively) exhibit reduced exercise capacity, accumulating evidence suggests that the underlying pathophysiology may be different between these two conditions. Unlike HFrEF, which is characterized by cardiac dysfunction with lower peak oxygen uptake, exercise intolerance in HFpEF appears to be predominantly attributed to peripheral limitations involving inadequate vasoconstriction rather than cardiac limitations. However, the relationship between systemic hemodynamics and the sympathetic neural response during exercise in HFpEF is less clear. This mini review summarizes the current knowledge on the sympathetic (i.e., muscle sympathetic nerve activity, plasma norepinephrine concentration) and hemodynamic (i.e., blood pressure, limb blood flow) responses to dynamic and static exercise in HFpEF compared to HFrEF, as well as non-HF controls. We also discuss the potential of a relationship between sympathetic over-activation and vasoconstriction leading to exercise intolerance in HFpEF. The limited body of literature indicates that higher peripheral vascular resistance, perhaps secondary to excessive sympathetically mediated vasoconstrictor discharge compared to non-HF and HFrEF, drives exercise in HFpEF. Excessive vasoconstriction also may primarily account for over elevations in blood pressure and concomitant limitations in skeletal muscle blood flow during dynamic exercise, resulting in exercise intolerance. Conversely, during static exercise, HFpEF exhibit relatively normal sympathetic neural reactivity compared to non-HF, suggesting that other mechanisms beyond sympathetic vasoconstriction dictate exercise intolerance in HFpEF.

Prognostic value of cardiopulmonary exercise testing in a European cohort with cardiovascular risk factors absent of a cardiovascular disease diagnosis

INTRODUCTION

Cardiorespiratory fitness (CRF) is now considered a vital sign. Cardiopulmonary exercise testing (CPET) is the gold-standard assessment of CRF; peak oxygen consumption (VO₂) and the minute ventilation/carbon dioxide production (VE/VCO₂) slope are considered primary CPET measures of CRF. More work is needed to determine the role of this exercise assessment in the primary care setting.

METHODS

695 subjects (mean age: 62 ± 13 years, body mass index: 28.9 ± 5.3 kg/m², 375 female and 320 male) underwent CPET using a cycle ergometer. 95% of the cohort had one or more major cardiovascular risk factor (i.e., obesity, smoking, dyslipidemia, hypertension, diabetes); no subject was diagnosed with cardiovascular disease (CVD) at the time of CPET. Subjects were tracked for the composite endpoint of cardiovascular mortality or hospital admission.

RESULTS

Mean peak VO₂, VE/VCO₂ slope and peak respiratory exchange ratio were 17.8 ± 5.8 mlO₂•kg^-1•min^-1, 26.7 ± 4.1, and 1.18 ± 0.13, respectively. There were 42 composite events during the 64 ± 18 month tracking period. Both peak VO₂ (Chi-square 16.3, p < 0.001) and the VE/VCO₂ slope (Chi-square 14.9, p < 0.001) were significant univariate predictors of the composite endpoint. The VE/VCO₂ slope added significant predictive value to peak VO₂ and was retained in the multivariate regression (residual Chi-square 7.0, p = 0.008).

DISCUSSION

These results support the prognostic value of CPET prior to a CVD diagnosis. The prognostic value of the VE/VCO₂ slope, not commonly the focus of CPET trials in patients with one or more major cardiovascular risk factors but without a confirmed CVD diagnosis, is a particularly novel finding in the current study.

Assessing systolic and diastolic reserves in male and female mice

Cardiac reserve is a widely used health indicator and prognostic tool. Although it is well established how to assess cardiac reserve clinically, in preclinical models, it is more challenging lacking standardization. Furthermore, although cardiac reserve incorporates both systolic (i.e., contractile reserve) and diastolic (i.e., relaxation reserve) components of the cardiac cycle, less focus has been placed on diastolic reserve. The aim of our study was to determine which technique (i.e., echocardiography, invasive hemodynamic, and Langendorff) and corresponding parameters can be used to assess the systolic and diastolic reserves in preclinical models. Healthy adult male and female CD-1 mice were administered dobutamine and evaluated by echocardiography and invasive hemodynamic, or Langendorff to establish systolic and diastolic reserves. Here, we show that systolic reserve can be assessed using all techniques in vivo and in vitro. Yet, the current indices available are ineffective at capturing diastolic reserve of healthy mice in vivo. When assessing systolic reserve, sex affects the dose response of several commonly used echocardiography parameters [i.e., fractional shortening (FS), ejection fraction (EF)]. Taken together, this study improves our understanding of how sex impacts the interpretation assessment of cardiac reserve and establishes for the first time that in healthy adult mice, the diastolic reserve cannot be assessed by currently established methods in vivo.NEW & NOTEWORTHY Cardiac reserve is a globally used health indicator and prognostic tool that is used by clinicians and preclinical scientists. In physiology, we have a long-standing appreciation of how to assess systolic reserve but lack insight into sex differences and have no frame of reference for measuring diastolic reserve to certainty across cardiac techniques or the influence of sex. Here, we show that the primary means for assessing diastolic reserve is incorrect. Furthermore, we provided proof and clarity on how to correctly measure systolic and diastolic reserve capacities. We also highlight the imperative of sex differences to the measures of both systolic and diastolic reserves using several techniques (i.e., echocardiography, invasive hemodynamics, and Langendorff) in mice.

Prevalence of sarcopenia in heart failure: A systematic review

OBJECTIVE

Heart Failure (HF) is emerging as a crucial factor promoting muscle wasting and dysfunction contributing to sarcopenia. This modulates disease severity and reduces exercise capacity and leading to poorer outcomes. Therefore, we aimed to systematically investigate the overall prevalence of sarcopenia in HF.

METHODS

An electronic search was carried out in selected databases until 21st January, 2021. Data was pooled from the included articles and represented as pooled prevalence of sarcopenia. Subgroup analysis was undertaken between methods of diagnosis of sarcopenia, gender, ejection fraction, median time point and geographical region.

RESULTS

Amongst 32,643 citations imported from selected databases, 12 articles were included in final analysis. Analysis for prevalence of sarcopenia was 34%, with prevalence rates ranging from 10.1% to 68%. Subgroup analysis revealed strong associations between Dual-energy X-ray Absorptiometry (DXA) and Asian Working Group for Sarcopenia (AWGS) (chi square = 3.24; p < 0.001), with a good level of agreement (kappa = 0.76 [95% CI: 0.70-0.82]; p < 0.001). Gender wise analysis revealed higher prevalence of sarcopenia among males (66%) than females (34%).

CONCLUSION

Sarcopenia is highly prevalent among those with HF (irrespective of type of HF) and is more commonly seen in males compared to females.

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.

Rate adaptive pacing in people with chronic heart failure increases peak heart rate but not peak exercise capacity: a systematic review

Rate adaptive cardiac pacing (RAP) allows increased heart rate (HR) in response to metabolic demand in people with implantable electronic cardiac devices (IECD). The aim of this work was to conduct a systematic review to determine if RAP increases peak exercise capacity (peak VO₂) in line with peak HR in people with chronic heart failure. We conducted a systematic literature search from 1980, when IECD and RAP were first introduced, until 31 July 2021. Databases searched include PubMed, Medline, EMBASE, EBSCO, and the Clinical Trials Register. A comprehensive search of the literature produced a total of 246 possible studies; of these, 14 studies were included. Studies and subsequent analyses were segregated according to comparison, specifically standard RAP (RAPON) vs fixed rate pacing (RAPOFF), and tailored RAP (TLD RAPON) vs standard RAP (RAPON). Pooled analyses were conducted for peak VO₂ and peak HR for RAPON vs RAPOFF. Peak HR significantly increased by 15 bpm with RAPON compared to RAPOFF (95%CI, 7.98-21.97, P < 0.0001). There was no significant difference between pacing mode for peak VO₂ 0.45 ml kg^-1 min^-1 (95%CI, - 0.55-1.47, P = 0.38). This systematic review revealed RAP increased peak HR in people with CHF; however, there was no concomitant improvement in peak VO₂. Rather RAP may provide benefits at submaximal intensities by controlling the rise in HR to optimise cardiac output at lower workloads. HR may be an important outcome of CHF management, reflecting myocardial efficiency.

Revisiting skeletal myopathy and exercise training in heart failure: Emerging role of myokines

Exercise intolerance remains a major unmet medical need in patients with heart failure (HF). Skeletal myopathy is currently considered as the major limiting factor for exercise capacity in HF patients. On the other hand, emerging evidence suggest that physical exercise can decrease morbidity and mortality in HF patients. Therefore, mechanistic insights into skeletal myopathy may uncover critical aspects for therapeutic interventions to improve exercise performance in HF. Emerging data reviewed in this article suggest that the assessment of circulating myokines (molecules synthesized and secreted by skeletal muscle in response to contraction that display autocrine, paracrine and endocrine actions) may provide new insights into the pathophysiology, phenotyping and prognostic stratification of HF-related skeletal myopathy. Further studies are required to determine whether myokines may also serve as biomarkers to personalize the modality and dose of physical training prescribed for patients with HF and exercise intolerance. In addition, the production and secretion of myokines in patients with HF may interact with systemic alterations (e.g., inflammation and metabolic disturbances), frequently present in patients with HF. Furthermore, myokines may exert beneficial or detrimental effects on cardiac structure and function, which may influence adverse cardiac remodelling and clinical outcomes in HF patients. Collectively, these data suggest that a deeper knowledge on myokines regulation and actions may lead to the identification of novel physical exercise-based therapeutic approaches for HF patients.

Cardiovascular Disease and Exercise: From Molecular Mechanisms to Clinical Applications

Inactivity is a significant risk factor for cardiovascular disease. Exercise may greatly enhance the metabolism and function of the cardiovascular system, lower several risk factors, and prevent the development and treatment of cardiovascular disease while delivering easy, physical, and emotional enjoyment. Exercise regulates the cardiovascular system by reducing oxidative stress and chronic inflammation, regulating cardiovascular insulin sensitivity and the body's metabolism, promoting stem cell mobilization, strengthening autophagy and myocardial mitochondrial function, and enhancing cardiovascular damage resistance, among other effects. Appropriate exercise intervention has become an essential adjuvant therapy in clinical practice for treating and rehabilitating various cardiovascular diseases. However, the prescription of exercise for preventing and treating cardiovascular diseases, particularly the precise selection of individual exercise techniques and their volume, remains controversial. Using multiomics to explain further the molecular process underlying the positive effects of exercise on cardiovascular health will not only improve our understanding of the effects of exercise on health but also establish a scientific basis and supply new ideas for preventing and treating cardiovascular diseases by activating the endogenous protective mechanisms of the body and suggesting more specific exercise prescriptions for cardiovascular rehabilitation.

Care of Patients With Transthyretin Amyloidosis: the Roles of Nutrition, Supplements, Exercise, and Mental Health

Transthyretin (ATTR) amyloidosis is a debilitating disease that results in organ failure and eventual death. As the disease progresses, patients experience neurologic, gastrointestinal, and cardiovascular symptoms that increasingly compromise their nutritional status and exercise capacity. These symptoms cause considerable emotional stress and mental health challenges for patients and caregivers. This review summarizes common symptoms and mechanisms associated with malnutrition and exercise intolerance, and sources of emotional stress, and offers therapeutic strategies to address these issues. Although earlier diagnosis and disease-specific treatment are central to caring for patients with ATTR amyloidosis, additional attention to symptom-focused treatments to improve nutritional status, maintain exercise tolerance and capacity, and improve and maintain mental health are also important. In conclusion, a team-based approach involving multiple clinicians and providers can offer more comprehensive and coordinated care, support, and education for patients and caregivers.

Alveolar Dead Space Is Augmented During Exercise in Patients With Heart Failure With Preserved Ejection Fraction

BACKGROUND

Patients with heart failure with preserved ejection fraction (HFpEF) exhibit many cardiopulmonary abnormalities that could result in V˙/Q˙ mismatch, manifesting as an increase in alveolar dead space (VDalveolar) during exercise. Therefore, we tested the hypothesis that VDalveolar would increase during exercise to a greater extent in patients with HFpEF compared with control participants.

RESEARCH QUESTION

Do patients with HFpEF develop VDalveolar during exercise?

STUDY DESIGN AND METHODS

Twenty-three patients with HFpEF and 12 control participants were studied. Gas exchange (ventilation [V˙E], oxygen uptake [V˙o2], and CO2 elimination [V˙co2]) and arterial blood gases were analyzed at rest, twenty watts (20W), and peak exercise. Ventilatory efficiency (evaluated as the V˙E/V˙co2 slope) also was measured from rest to 20W in patients with HFpEF. The physiologic dead space (VDphysiologic) to tidal volume (VT) ratio (VD/VT) was calculated using the Enghoff modification of the Bohr equation. VDalveolar was calculated as: (VD / VT × VT) - anatomic dead space. Data were analyzed between groups (patients with HFpEF vs control participants) across conditions (rest, 20W, and peak exercise) using a two-way repeated measures analysis of variance and relationships were analyzed using Pearson correlation coefficient.

RESULTS

VDalveolar increased from rest (0.12 ± 0.07 L/breath) to 20W (0.22 ± 0.08 L/breath) in patients with HFpEF (P < .01), whereas VDalveolar did not change from rest (0.01 ± 0.06 L/breath) to 20W (0.06 ± 0.13 L/breath) in control participants (P = .19). Thereafter, VDalveolar increased from 20W to peak exercise in patients with HFpEF (0.37 ± 0.16 L/breath; P < .01 vs 20W) and control participants (0.19 ± 0.17 L/breath; P = .03 vs 20W). VDalveolar was greater in patients with HFpEF compared with control participants at rest, 20W, and peak exercise (main effect for group, P < .01). Moreover, the increase in VDalveolar correlated with the V˙E/V˙co2 slope (r = 0.69; P < .01), which was correlated with peak V˙o2peak (r = 0.46; P < .01) in patients with HFpEF.

INTERPRETATION

These data suggest that the increase in V˙/Q˙ mismatch may be explained by increases in VDalveolar and that increases in VDalveolar worsens ventilatory efficiency, which seems to be a key contributor to exercise intolerance in patients with HFpEF.

Correlation between respiratory muscle weakness and frailty status as risk markers for poor outcomes in patients with cardiovascular disease

AIMS

Although the developmental mechanism of respiratory muscle weakness (RMW) and frailty are partly similar in patients with cardiovascular disease (CVD), their relationship remains unclear. This study aimed to investigate the correlation between RMW and frailty and its impact on clinical outcomes in patients with CVD.

METHODS AND RESULTS

In this retrospective observational study, consecutive 1217 patients who were hospitalized for CVD treatment were enrolled. We assessed frailty status by using the Fried criteria and respiratory muscle strength by measuring the maximal inspiratory pressure (PImax) at hospital discharge, with RMW defined as PImax <70% of the predicted value. The endpoint was a composite of all-cause death and/or readmission for heart failure. We examined the prevalence of RMW and frailty and their correlation. The relationships of RMW with the endpoint for each presence or absence of frailty were also investigated. Respiratory muscle weakness and frailty were observed in 456 (37.5%) and 295 (24.2%) patients, respectively, and 149 (12.2%) patients had both statuses. Frailty was detected as a significant indicator of RMW [odds ratio: 1.84, 95% confidence interval (CI): 1.39-2.44]. Composite events occurred in 282 patients (23.2%). Respiratory muscle weakness was independently associated with an increased incidence of events in patients with both non-frailty [hazard ratio (HR): 1.40, 95% CI: 1.04-1.88] and frailty (HR: 1.68, 95% CI: 1.07-2.63).

CONCLUSIONS

This is the first to demonstrate a correlation between RMW and frailty in patients with CVD, with 12.2% of patients showing overlap. RMW was significantly associated with an increased risk of poor outcomes in patients with CVD and frailty.

Multifactorial Effects of Outpatient Cardiac Rehabilitation in Patients with Heart Failure: A Nationwide Retrospective Cohort Study

AIM

Although cardiac rehabilitation (CR) is a strongly recommended therapy, no large study has assessed the effects of outpatient CR in patients with heart failure (HF) in real-world settings. Therefore, this study aimed to investigate the multifactorial effects of outpatient CR in patients with HF using a nationwide database.

METHODS AND RESULTS

This nationwide retrospective cohort study was performed using the National Database of Health Insurance Claims and Specific Health Checkups of Japan. Patients with acute HF who underwent inpatient CR between April 2014 and March 2020 were included. The association between outpatient CR participation and all-cause mortality, rehospitalisation for HF, use of medical resources, and medical costs was analysed using propensity score matching analysis. Of 250,528 patients, 17,884 (7.1%) underwent outpatient CR. After propensity score matching, the CR (+) group was associated with a reduction in the risk of all-cause mortality (hazard ratio [HR]: 0.64, 95% confidence interval [CI]: 0.60-0.68, p < 0.001) and rehospitalisation for HF compared to the CR (-) group (HR: 0.87, 95% CI: 0.82-0.92, p < 0.001). The proportion of guideline-based medication use for HF at 1 year was higher in the CR (+) group than in the CR (-) group. The total medical costs from the index hospitalisation to 1.5 years after admission were similar between the groups.

CONCLUSION

Outpatient CR participation after discharge from HF was associated with reduced mortality and rehospitalisation for HF without increasing medical costs.

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.

Nonpharmacological Strategies in Heart Failure with Preserved Ejection Fraction

Patients with heart failure with preserved ejection fraction (HFpEF) suffer from a high rate of cardiometabolic comorbidities with limited pharmaceutical therapies proven to improve clinical outcomes and cardiorespiratory fitness (CRF). Nonpharmacologic therapies, such as exercise training and dietary interventions, are promising strategies for this population. The aim of this narrative review is to present a summary of the literature published to date and future directions related to the efficacy of nonpharmacologic, lifestyle-related therapies in HFpEF, with a focus on exercise training and dietary interventions.

Reliability and validity of specific quality of life assessment questionnaires related to chronic venous insufficiency: a systematic review

This systematic review aimed to discuss the main findings regarding the reliability and validity of health-related quality of life questionnaires for chronic venous insufficiency. Searches were performed on the MEDLINE, CINAHL, Web of Science, LILACS, and Scopus databases. The search terms used were related to "venous insufficiency", and "quality of life". The CIVIQ-20 and CIVIQ-14 instruments had adequate internal consistency and both were able to discriminate disease severity. The VEINES-QoL showed adequate internal consistency but was not able to discriminate disease severity. Most studies did not demonstrate a correlation between VEINES-QoL and the mental component of the SF-36. The AVVQ had inadequate reliability but its validity was also doubtful when compared to the SF-36. The VARIShort demonstrated good internal consistency, reproducibility, and validity, but only the original study was included. For venous leg ulcers, the CCVUQ showed adequate reliability and validity when compared to VLU-QoL.

[Heart failure and obesity]

Obesity is an independent predictor of cardiovascular diseases (CVD), including heart failure (HF). Nevertheless, numerous studies have shown that patients with CVD who are overweight and slightly obese have a better short-term and moderate prognosis than thinner patients with CVD. This phenomenon has been called the obesity paradox. Understanding the obesity paradox is important in patients with HF, given the high prevalence of obesity in patients with HF. The article presents an overview of clinical studies devoted to the study of obesity as a risk factor for HF, the pathogenesis of HF in obesity, and highlights the issues of the obesity paradox and the treatment of obesity in this category of patients.

Sarcopenic Obesity Is Associated With Reduced Cardiorespiratory Fitness Compared With Nonsarcopenic Obesity in Patients With Heart Failure With Reduced Ejection Fraction

BACKGROUND

Sarcopenia impairs cardiorespiratory fitness (CRF) in patients with heart failure with reduced ejection fraction (HFrEF). Obesity has also been shown to impair CRF; however, the effects of sarcopenia on CRF in patients with obesity and HFrEF are unknown. The aim of this analysis was to examine differences in CRF between patients with sarcopenic obesity (SO) and non-SO (NSO) with HFrEF. We also assessed associations between skeletal muscle mass index (SMMI) and CRF.

METHODS

Forty patients with HFrEF and obesity underwent cardiopulmonary exercise testing to collect measures of CRF including peak oxygen consumption (VO2), circulatory power, oxygen uptake efficiency slope, O2 pulse, and exercise time. Body composition was performed in all patients using bioelectrical impedance analysis to quantify fat mass index and divide patients into SO and NSO based on SMMI cutoffs. Results are presented as mean (SD) or median [interquartile range] as appropriate.

RESULTS

Nearly half (43% [n=17]) of patients had SO. Patients with SO had a lower SMMI than those with NSO, and no differences in fat mass index were observed between groups. Those with SO achieved a lower absolute peak VO2 (NSO, 1.62±0.53 L·min-1 versus SO, 1.27±0.44 L·min-1, P=0.035), oxygen uptake efficiency slope (NSO, 1.92±0.59 versus SO, 1.54±0.48, P=0.036), and exercise time (NSO, 549±198 seconds versus SO, 413±140 seconds, P=0.021) compared to those with NSO. On multivariate analysis, SMMI remained a significant predictor of absolute peak VO2 when adjusted for age, sex, adiposity, and HF severity.

CONCLUSIONS

In patients with HFrEF and obesity, sarcopenia, defined as low SMMI, is associated with a clinically significant reduction in CRF, independent of adiposity.

Right Ventricular Contractile Reserve: A Key Metric to Identifying when Cardiorespiratory Fitness will Improve with Pulmonary Vasodilators

Cardiorespiratory fitness (CRF) has been proposed as a vital sign for the past several years, supported by a wealth of evidence demonstrating its significance as a predictor of health trajectory, exercise/functional capacity, and quality of life. According to the Fick equation, oxygen consumption (VO₂) is the product of cardiac output (CO) and arterial-venous oxygen difference, with the former being a primary driver of one's aerobic capacity. In terms of the dependence of aerobic capacity on a robust augmentation of CO from rest to maximal exercise, left ventricular (LV) CO has been the historic focal point. Patients with pulmonary arterial hypertension (PAH) or secondary pulmonary hypertension (PH) present with a significantly compromised CRF; as pathophysiology worsens, so too does CRF. Interventions to improve pulmonary hemodynamics continue to emerge and are now a standard of clinical care in several patient populations with increased pulmonary pressures; new pharmacologic options continue to be explored. Improvement in CRF/aerobic capacity has been and continues to be a primary or leading secondary endpoint in clinical trials examining the effectiveness of pulmonary vasodilators. A central premise for including CRF/aerobic capacity as an endpoint is that pulmonary vasodilation will lead to a significant downstream increase in LV CO and therefore peak VO₂. However, the importance of right ventricular (RV) CO to the peak VO₂ response continues to be overlooked. The current review provides an overview of relevant principles of exercise physiology, approaches to assessing RV contractile reserve and proposals for clinical trial design and subject phenotyping.

The Pre-Discharge Oxygen Uptake Efficiency Slope Predicts One-Year Cardiovascular Events in Acute Decompensated Heart Failure Patients

(1) Background: Heart failure is a complex disease leading to functional disability. Cardiopulmonary exercise testing (CPET) is the gold standard in assessing aerobic capacity and formulating function-based prognostic stratification; however, patients with acute heart failure after medical treatment usually remain with markedly reduced exercise capacity, leading to early termination of CPET with submaximal testing results. The current study aimed to assess the cardiorespiratory fitness and characteristics of CPET variables of patients after acute heart failure treatment and determine potential CPET variables with prognostic value. (2) Methods: We recruited patients during hospitalization after management of acute heart failure, and pre-discharge CPET was performed. All enrolled patients were followed for one year for major adverse cardiovascular events (MACE). (3) Results: 85 patients were enrolled, with average left ventricular ejection fraction of 30.52%, and peak oxygen consumption of 10.85 mL/min/kg at baseline. The one-year MACE was 50%. Oxygen uptake efficiency slope (OUES) was a significant event predictor, with lower one-year MACE in those with OUES ≥ 1.25 (p < 0.001). Cox regression analysis showed a 5.421-fold increased risk of MACE in those with OUES < 1.25 (p = 0.004). (4) Conclusions: The current results suggested OUES is a significant prognostic indicator in patients with acute heart failure. This also emphasized the critical role of CPET in patients with heart failure for prognostic stratification.

Haemodynamic determinants of quality of life in chronic heart failure

Background

Heart failure patients demonstrate reduced functional capacity, hemodynamic function, and quality of life (QOL) which are associated with high mortality and morbidity rate. The aim of the present study was to assess the relationship between functional capacity, hemodynamic response to exercise and QOL in chronic heart failure.

Methods

A single-centre prospective study recruited 42 chronic heart failure patients (11 females, mean age 60 ± 10 years) with reduced left ventricular ejection fraction (LVEF = 23 ± 7%). All participants completed a maximal graded cardiopulmonary exercise test with non-invasive hemodynamic (bioreactance) monitoring. QOL was assessed using Minnesota Living with Heart Failure Questionnaire.

Results

The average value of QOL score was 40 ± 23. There was a significant negative relationship between the QOL and peak O₂ consumption (r = − 0.50, p ≤ 0.01). No significant relationship between the QOL and selected exercise hemodynamic measures was found, including peak exercise cardiac power output (r = 0.15, p = 0.34), cardiac output (r = 0.22, p = 0.15), and mean arterial blood pressure (r = − 0.08, p = 0.60).

Conclusion

Peak O₂ consumption, but not hemodynamic response to exercise, is a significant determinant of QOL in chronic heart failure patients.

SGLT-2 inhibitors on prognosis and health-related quality of life in patients with heart failure and preserved ejection fraction: A systematic review and meta-analysis

Background

Heart failure with preserved ejection fraction (HFpEF) is becoming the main subtype of heart failure, but lacks proven effective therapies. Sodium-glucose cotransporter-2 (SGLT-2) inhibitor, a new kind of oral glucose-lowering agent, shows a great effect on improving cardiovascular outcomes. Based on the results of current RCTs, we perform this meta-analysis to illustrate the therapeutic impact of SGLT2i in HFpEF patients.

Methods

We systematically searched the online database and 10 RCTs were involved. The primary outcome was the prognosis outcome of HFpEF patients, including a composite outcome of cardiovascular (CV) death and hospitalization for heart failure (HHF), CV mortality, HHF, and all-cause mortality. Main secondary outcomes included improvement of KCCQ-TSS (Kansas City Cardiomyopathy Questionnaire and total symptom score) and 6-Minute Walk Test (6MWT). All pooled results were calculated by the random-effects model. Statistical heterogeneity was assessed using the chi-squared test and was quantified using the I-squared statistic.

Results

Ten RCTs comprising 10,334 patients were involved in. Incidence of composite outcome was reduced in SGLT-2 inhibitor group compared with placebo (HR: 0.78, 95% CI: 0.69–0.88, p = 0.00). Improvement of KCCQ-TSS was also more pronounced in the SGLT-2 inhibitor group (MD: 2.74, 95% CI: 1.30–4.18, p = 0.00). No statistical difference was observed in 6MWT.

Conclusion

Treating HFpEF patients with SGLT-2 inhibitors is associated with reducing the composite outcome of CV death and HHF and improving health-related quality of life. Further studies with more evidence are in need to confirm this conclusion.

Heart failure in mice induces a dysfunction of the sinus node associated with reduced CaMKII signaling

Dysfunction of the sinoatrial node (SAN), the natural heart pacemaker, is common in heart failure (HF) patients. SAN spontaneous activity relies on various ion currents in the plasma membrane (voltage clock), but intracellular Ca2+ ([Ca2+]i) release via ryanodine receptor 2 (RYR2; Ca2+ clock) plays an important synergetic role. Whereas remodeling of voltage-clock components has been revealed in HF, less is known about possible alterations to the Ca2+ clock. Here, we analyzed [Ca2+]i handling in SAN from a mouse HF model after transverse aortic constriction (TAC) and compared it with sham-operated animals. ECG data from awake animals showed slower heart rate in HF mice upon autonomic nervous system blockade, indicating intrinsic sinus node dysfunction. Confocal microscopy analyses of SAN cells within whole tissue showed slower and less frequent [Ca2+]i transients in HF. This correlated with fewer and smaller spontaneous Ca2+ sparks in HF SAN cells, which associated with lower RYR2 protein expression level and reduced phosphorylation at the CaMKII site. Moreover, PLB phosphorylation at the CaMKII site was also decreased in HF, which could lead to reduced sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) function and lower sarcoplasmic reticulum Ca2+ content, further depressing the Ca2+ clock. The inhibition of CaMKII with KN93 slowed [Ca2+]i transient rate in both groups, but this effect was smaller in HF SAN, consistent with less CaMKII activation. In conclusion, our data uncover that the mechanism of intrinsic pacemaker dysfunction in HF involves reduced CaMKII activation.