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

Determinants of cardiac output in health and heart failure

Sustained physical exercise depends on delivery of oxygenated blood to exercising muscle. At least among healthy individuals, bulk transport of blood is tightly matched to metabolic demand, such that cardiac output increases by ∼6 L/min for every 1 L/min increase in oxygen uptake. Multiple factors contribute to the regulation of cardiac output, including central command, the exercise pressor reflex (EPR) and arterial baroreceptors. Pulmonary arterial and left ventricular pressures increase in proportion to the rise in cardiac output and exercise intensity. The right ventricle augments contractility to maintain ventricular-arterial (VA) coupling and lusitropy to facilitate venous return. Among patients with heart failure (HF), however, the ability to deliver blood to exercising muscle is compromised as a result of multiple abnormalities impacting EPR, ventricular contractility, haemodynamics and VA coupling. The purpose of this review is to provide an overview of the factors limiting exercise capacity and cardiac output among patients with HF compared to what is known about normal physiology among healthy individuals.

Relationship of red blood cell mass profiles and anemia type to outcomes and cardiopulmonary exercise performance in chronic heart failure

BACKGROUND

Blood volume analysis (BVA) allows direct measurement of red blood cell mass (RBCM) and differentiation of true and dilutional anemia in heart failure (HF). This study aimed to characterize the relationships of RBCM profiles and anemia types to HF outcomes and cardiopulmonary exercise test (CPET) parameters.

METHODS

Chronic stable HF patients were prospectively enrolled. All patients underwent BVA; a subset underwent supine invasive CPET within 24 hours of BVA. RBCM profiles were defined using RBCM %deviation (deficit: <-10%, normal: -10 to 10%, excess: >10%). Anemia defined by World Health Organization criteria alone was categorized using RBCM %deviation (<-10% true anemia, ≥-10% dilutional pseudo-anemia). HF hospitalization at 6 months and CPET parameters were compared among RBCM profiles and anemia types.

RESULTS

One-hundred twenty patients (58 years, 40% female, 41% Black, 63% HFrEF) were enrolled. Forty percent had RBCM deficit, 37.5% had normal RBCM, and 22.5% had excess RBCM. Fifty-eight patients (48%) were anemic: 60% true anemia and 40% dilutional pseudo-anemia. Patients with dilutional pseudo-anemia had a higher incidence of HF hospitalization (44.8%) compared to no anemia (22.7%) and true anemia (20.6%) (P = .040). There was no difference in HF hospitalization among RBCM profiles (P = .99). There was a nonsignificant trend toward worse peak VO2 in RBCM deficit and true anemia, with no differences in other CPET parameters.

CONCLUSIONS

Dilutional pseudo-anemia demonstrated higher HF hospitalizations compared to true anemia, while true anemia had a trend towards worse peak VO2. The implications of BVA-identified RBCM profiles and anemia types for clinical management warrant further investigation.

Crossover Trial of Exogenous Ketones on Cardiometabolic Endpoints in Heart Failure With Preserved Ejection Fraction

BACKGROUND

The etiology of exercise intolerance in heart failure with preserved ejection fraction (HFpEF) is multifactorial. Several contributing pathways may be improved by ketone ester (KE).

OBJECTIVES

This study aims to determine whether KE improves exercise tolerance in HFpEF.

METHODS

KETO-HFpEF (Ketogenic Exogenous Therapies in HFpEF) is a randomized, crossover, placebo-controlled trial of acute KE dosing in 20 symptomatic HFpEF participants. Coprimary endpoints include peak oxygen consumption (VO2) during incremental cardiopulmonary exercise testing and time to exhaustion during an additional constant-intensity exercise (75% peak workload) bout.

RESULTS

The average age was 71 ± 8 years, 60% were women, and 65% were White. KE did not improve peak VO2 (KE: 10.4 ± 3.6 vs placebo: 10.5 ± 4.0 mL/kg/min; P = 0.75). At rest, heart rate, biventricular systolic function, and cardiac output (0.6 L/min [95% CI: 0.3-1.0 L/min]) were greater with KE vs placebo, whereas total peripheral resistance (-3.2 WU [95% CI: -5.2 to -1.2 WU]) and the arteriovenous oxygen content difference (-0.7 mL of O2/dL blood [95% CI: -1.2 to -0.2 mL]) were lower. These differences mostly disappeared during incremental exercise. KE did not improve exercise endurance during the constant-intensity protocol (9.7 ± 7.3 minutes vs 8.7 ± 4.4 minutes; P = 0.51). In 6 participants receiving 6,6-2H2-glucose infusions during constant-intensity exercise, plasma glucose appearance rate before and during exercise was lower with KE (-0.24 mg/kg/min; P < 0.001). During both exercise protocols, KE lowered: 1) respiratory exchange ratios, demonstrating decreased systemic carbohydrate use; 2) nonesterified fatty acids and glucose; and 3) estimated left ventricular filling pressures (E/e').

CONCLUSIONS

Despite robust ketosis, shifting substrate use away from carbohydrates, and decreasing estimated left ventricular filling pressures, acute KE supplementation did not improve peak VO2 or constant-intensity exercise in HFpEF. (Ketogenic Exogenous Therapies in HFpEF [KETO-HFpEF]; NCT04633460).

Cardiac Involvement and Heart Failure Staging in Patients with Systemic Sclerosis Without Pulmonary Arterial Hypertension

Background/Objectives: Systemic sclerosis (SSc) is an autoimmune connective tissue disease characterized by fibrosis and vascular damage, significantly increasing the risk of heart failure (HF). Methods: This cross-sectional study included 61 SSc patients (92% female, mean age 63 ± 13 years), excluding those with pulmonary arterial hypertension, referred to a tertiary pulmonary hypertension center. HF stages were classified according to updated guidelines. Clinical, echocardiographic, hemodynamic, and functional capacity data were analyzed in relation to HF stages. Results: A total of 48% of patients had pre-symptomatic HF (5% stage A, 43% stage B), while 38% had symptomatic HF (stage C). Advanced HF stages were significantly associated with older age (p = 0.02) and multiorgan involvement (p = 0.045) but not with SSc subtype or autoantibodies. Structural and functional echocardiographic abnormalities were prevalent (77% and 10%, respectively). Markers of elevated ventricular filling pressure such as left atrial volume (p = 0.011) and E/e' ratio (p = 0.03) correlated with HF severity. Functional impairment was observed with lower 6 min walk test (6MWT) distance (p = 0.017), reduced VO2 peak (p = 0.015), and increased VE/VCO2 slope (p = 0.002). Resting pulmonary artery wedge pressure did not correlate with HF stage (p = 0.93). VE/VCO2 slope and 6MWT were independently associated with HF severity. Conclusions: Preclinical and symptomatic HF are highly prevalent in SSc patients. HF staging was linked to disease severity, age, and cardiovascular risk factors. Functional capacity tests (6MWT and CPET) serve as valuable tools for HF risk stratification. These findings highlight the critical need for comprehensive cardiovascular assessment and targeted management strategies to mitigate HF progression in SSc patients.

Mechanisms of exercise intolerance in heart failure with preserved ejection fraction (HFpEF)

Exercise intolerance is a well-established symptom of heart failure with preserved ejection fraction (HFpEF) and is associated with impaired quality of life and worse clinical outcomes. Historically attributed to diastolic dysfunction of the left ventricle, exercise intolerance in HFpEF is now known to result not only from diastolic dysfunction, but also from impairments in left ventricular systolic function, left atrial pathology, right ventricular dysfunction, and valvular disease. Disorders of heart rate and rhythm such as chronotropic incompetence and atrial fibrillation have also been implicated in exercise intolerance in this population. Pathologic changes to extra-cardiac organ systems including the respiratory, vascular, hormonal, and skeletal muscle systems are also thought to play a role in exercise impairment. Finally, comorbidities such as obesity, inflammation, and anemia are common and likely contributory in many cases. The role of each of these factors is discussed in this review of exercise intolerance in patients with HFpEF.

Maintained sympathetic reactivity but blunted pressor response to static handgrip exercise in heart failure with preserved ejection fraction

PURPOSE

Recent studies have reported blunted increases in blood pressure (BP) during static handgrip (SHG) in patients with heart failure with preserved ejection fraction (HFpEF), which may be attributed to abnormal sympathetic reactivity during exercise and/or impaired muscle metaboreflex function. However, it is unknown whether the sympathetic neural response to SHG and isolated muscle metaboreflex activation via post-exercise circulatory occlusion (PECO) are attenuated in HFpEF.

METHODS

Thirty-nine patients with HFpEF and 24 age-matched non-HFpEF controls were studied in the supine position. BP, heart rate (HR), and muscle sympathetic nerve activity (MSNA) were measured during SHG at 40% of maximal voluntary contraction until fatigue followed by 2-min PECO.

RESULTS

Resting mean arterial pressure (MAP) was lower and peak increase (Δ) in MAP was smaller in patients with HFpEF than in controls during SHG (Δ23 ± 15 [standard deviation] vs. Δ34 ± 15 mmHg; P = 0.007) and PECO (Δ15 ± 11 vs. Δ19 ± 9 mmHg; P = 0.047). HR was greater in patients at rest but did not differ between the two groups at peak SHG. Patients had higher resting MSNA burst frequency than controls (37 ± 14 vs. 27 ± 13 bursts/min; P = 0.031); however, burst incidence was not different between the groups (P = 0.226). There were no differences in MSNA responses to SHG (Δ19 ± 15 vs. Δ18 ± 10 bursts/min at peak; P = 0.841) or PECO (Δ3 ± 12 vs. Δ5 ± 7 bursts/min; P = 0.495) between groups.

CONCLUSION

The patients with HFpEF maintained sympathetic reactivity but had an attenuated pressor response during fatiguing SHG. Additionally, muscle metaboreflex activation of vasomotor sympathetic outflow appeared to be minimal in both groups, with no significant difference between patients and controls.

Cardiopulmonary Exercise Testing

AbstractBecause symptoms of cardiopulmonary disease often occur with exertion, cardiopulmonary exercise testing (CPET) has a unique role in the assessment of patient symptoms, disease severity, prognosis, and response to therapy. In addition to the evaluation of cardiovascular and pulmonary physiology, CPET provides an assessment of the interaction of the cardiovascular and pulmonary systems with the musculoskeletal, nervous, and hematological systems. In this article, we review key CPET variables, protocols, and clinical indications.

Pulmonary gas exchange in relation to exercise pulmonary hypertension in patients with heart failure with preserved ejection fraction

BACKGROUND

Exercise pulmonary hypertension, defined as a mean pulmonary arterial pressure (mPAP)/cardiac output (Q̇c) slope >3 WU during exercise, is common in patients with heart failure with preserved ejection fraction (HFpEF). However, the pulmonary gas exchange-related effects of an exaggerated exercise pulmonary hypertension (EePH) response are not well defined, especially in relation to dyspnoea on exertion and exercise intolerance.

METHODS

48 HFpEF patients underwent invasive (pulmonary and radial artery catheters) constant-load (20 W) and maximal incremental cycle testing. Haemodynamic measurements (mPAP and Q̇c), arterial blood and expired gases, and ratings of perceived breathlessness (Borg 0-10 scale) were obtained. The mPAP/Q̇c slope was calculated from rest to 20 W. Those with a mPAP/Q̇c slope ≥4.2 (median) were classified as HFpEF+EePH (n=24) and those with a mPAP/Q̇c slope <4.2 were classified as HFpEF (without EePH) (n=24). The alveolar-arterial oxygen tension difference, dead space to tidal volume ratio (Bohr equation) and the minute ventilation to carbon dioxide production slope (from rest to 20 W) were calculated.

RESULTS

Arterial oxygen tension was lower (p=0.03) and dead space to tidal volume ratio was higher (p=0.03) at peak exercise in HFpEF+EePH than in HFpEF. The alveolar-arterial oxygen tension difference was similar at peak exercise between groups (p=0.14); however, patients with HFpEF+EePH achieved the peak alveolar-arterial oxygen tension difference at a lower peak work rate (p<0.01). The minute ventilation to carbon dioxide production slope was higher in HFpEF+EePH than in HFpEF (p=0.01). Perceived breathlessness was ≥1 unit higher at 20 W and peak oxygen uptake was lower (p<0.01) in HFpEF+EePH than in HFpEF.

CONCLUSIONS

These data suggest that EePH contributes to pulmonary gas exchange impairments during exercise by causing a ventilation/perfusion mismatch that provokes both ventilatory inefficiency and hypoxaemia, both of which seem to contribute to dyspnoea on exertion and exercise intolerance in patients with HFpEF.

Two-hit mouse model of heart failure with preserved ejection fraction combining diet-induced obesity and renin-mediated hypertension

Heart failure with preserved ejection fraction (HFpEF) is increasingly common but its pathogenesis is poorly understood. The ability to assess genetic and pharmacologic interventions is hampered by the lack of robust preclinical mouse models of HFpEF. We developed a novel "two-hit" model, which combines obesity and insulin resistance with chronic pressure overload to recapitulate clinical features of HFpEF. C57Bl6/NJ mice fed a high-fat diet (HFD) for > 10 weeks were administered an AAV8-driven vector resulting in constitutive overexpression of mouse Renin1d. HFD-Renin (aka "HFpEF") mice demonstrated obesity and insulin resistance, moderate left ventricular hypertrophy, preserved systolic function, and diastolic dysfunction indicated by echocardiographic measurements; increased left atrial mass; elevated natriuretic peptides; and exercise intolerance. Transcriptomic and metabolomic profiling of HFD-Renin myocardium demonstrated upregulation of pro-fibrotic pathways and downregulation of metabolic pathways, in particular branched chain amino acid catabolism, similar to human HFpEF. Treatment with empagliflozin, an effective but incompletely understood HFpEF therapy, improved multiple endpoints. The HFD-Renin mouse model recapitulates key features of human HFpEF and will enable studies dissecting the contribution of individual pathogenic drivers to this complex syndrome. Additional preclinical HFpEF models allow for orthogonal studies to increase validity in assessment of interventions.

Exercise Hemodynamics in Heart Failure with Preserved Ejection Fraction

Exercise intolerance is common in patients with heart failure with preserved ejection fraction. This review will discuss the utility of exercise hemodynamics under both diagnostic and prognostic circumstances and highlight challenges associated with making and interpreting measures taken during exercise.

Discrepancy in the Diagnosis of Heart Failure With Preserved Ejection Fraction Between Supine Versus Upright Exercise Hemodynamic Testing

BACKGROUND

Invasive exercise right heart catheterization is a gold standard in diagnosing heart failure with preserved ejection fraction (HFpEF). Body positions during the test influence hemodynamics. However, the discrepancy in HFpEF diagnosis between exercise testing in supine versus upright position is unknown.

METHODS

We conducted a 2-center prospective study enrolling patients referred for exercise right heart catheterization for HFpEF. We performed a Supright protocol integrating submaximal supine bicycle ergometry (20 W) followed by maximal upright bicycle ergometry with a breath-by-breath oxygen analyzer. HFpEF hemodynamic criteria specific to testing positions were applied. Patients were considered to have concordant HFpEF if they met criteria in both positions or discordant HFpEF if they met criteria only in the supine position.

RESULTS

Of 36 patients who met HFpEF criteria in supine position, 18 (50%) did not meet criteria in upright position (discordant HFpEF). Discordant HFpEF had less atrial fibrillation (0% versus 55%; P<0.001), lower left atrial volume (60±14 versus 77±21 mL; P=0.010), and lower H2FPEF score (2.1±1.3 versus 5.1±2.3; P<0.001). In supine position, pulmonary arterial wedge pressure was lower in discordant HFpEF at rest (15±4 versus 19±7 mm Hg; P=0.040). In upright position, pulmonary arterial wedge pressure was lower in discordant HFpEF both at rest (8±4 versus 14±6 mm Hg; P=0.002) and at peak exercise (14±4 versus 27±7 mm Hg; P<0.001). Pulmonary arterial wedge pressure/cardiac output slope was lower in discordant HFpEF (1.6±1.7 versus 3.6±2.9; P<0.001). Maximal workload (46±18 versus 49±24 W; P=0.59) or peak oxygen consumption (11.4±2.8 versus 12.9±3.4 mL/[kg·min]; P=0.15) was similar between groups.

CONCLUSIONS

Half of patients who met HFpEF criteria in the supine position did not meet the criteria in the upright position. Patients with a discordant HFpEF phenotype had less structural and hemodynamic abnormalities compared with those with concordant HFpEF. A Supright exercise right heart catheterization approach is feasible and merits further investigation to determine the clinical implications of discordant exercise hemodynamic findings in supine and upright positions.

The aging heart in focus: The advanced understanding of heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) accounts for 50 % of heart failure (HF) cases, making it the most common type of HF, and its prevalence continues to increase in the aging society. HFpEF is a systemic syndrome resulting from many risk factors, such as aging, metabolic syndrome, and hypertension, and its clinical features are highly heterogeneous in different populations. HFpEF syndrome involves the dysfunction of multiple organs, including the heart, lung, muscle, and vascular system. The heart shows dysfunction of various cells, including cardiomyocytes, endothelial cells, fibroblasts, adipocytes, and immune cells. The complex etiology and pathobiology limit experimental research on HFpEF in animal models, delaying a comprehensive understanding of the mechanisms and making treatment difficult. Recently, many scientists and cardiologists have attempted to improve the clinical outcomes of HFpEF. Recent advances in clinically related animal models and systemic pathology studies have improved our understanding of HFpEF, and clinical trials involving sodium-glucose cotransporter 2 inhibitors have significantly enhanced our confidence in treating HFpEF. This review provides an updated comprehensive discussion of the etiology and pathobiology, molecular and cellular mechanisms, preclinical animal models, and therapeutic trials in animals and patients to enhance our understanding of HFpEF and improve clinical outcomes.

Dapagliflozin Enhances Arterial and Venous Compliance During Exercise in Heart Failure With Preserved Ejection Fraction: Insights From the CAMEO-DAPA Trial

BACKGROUND

Systemic arterial compliance and venous capacitance are typically impaired in patients with heart failure with preserved ejection fraction (HFpEF), contributing to hemodynamic congestion with stress. Sodium-glucose cotransporter-2 inhibitors reduce hemodynamic congestion and improve clinical outcomes in patients with HFpEF, but the mechanisms remain unclear. This study tested the hypothesis that Dapagliflozin would improve systemic arterial compliance and venous capacitance during exercise in patients with HFpEF.

METHODS

In this secondary analysis from the CAMEO-DAPA trial (Cardiac and Metabolic Effects of Dapagliflozin in Heart Failure With Preserved Ejection Fraction Trial), 37 patients with HFpEF (mean age 68 ± 9 years, women 65%) underwent invasive hemodynamic exercise testing with simultaneous echocardiography at baseline and following treatment for 24 weeks with Dapagliflozin or placebo. Radial artery pressure (BP) was measured continuously using a fluid-filled catheter with transformation to aortic pressure, central hemodynamics were measured using high-fidelity micromanometers, and stressed blood volume was estimated from hemodynamic indices fit to a comprehensive cardiovascular model.

RESULTS

There was no statistically significant effect of Dapagliflozin on resting BP, but Dapagliflozin reduced systolic BP during peak exercise (estimated treatment difference [ETD], -18.8 mm Hg [95% CI, -33.9 to -3.7] P=0.016). Reduction in BP was related to improved exertional total arterial compliance (ETD, 0.06 mL/mm Hg/m2 [95% CI, 0.003-0.11] P=0.039) and aortic root characteristic impedance (ETD, -2.6 mm Hg/mL*sec [95% CI: -5.1 to -0.03] P=0.048), with no significant effect on systemic vascular resistance. Dapagliflozin reduced estimated stressed blood volume at rest and during peak exercise (ETD, -292 mm Hg [95% CI, -530 to -53] P=0.018), and improved venous capacitance evidenced by a decline in ratio of estimated stressed blood volume to total blood volume (ETD, -7.3% [95% CI, -13.3 to -1.3] P=0.020). Each of these effects of Dapagliflozin at peak exercise were also observed during matched 20W exercise intensity. Improvements in total arterial compliance and estimated stressed blood volume were correlated with decreases in body weight, and reduction in systolic BP with treatment was correlated with the change in estimated stressed blood volume during exercise (r=0.40, P=0.019). Decreases in BP were correlated with reduction in pulmonary capillary wedge pressure during exercise (r=0.56, P<0.001).

CONCLUSIONS

In patients with HFpEF, treatment with Dapagliflozin improved systemic arterial compliance and venous capacitance during exercise, while reducing aortic characteristic impedance, suggesting a reduction in arterial wall stiffness. These vascular effects may partially explain the clinical benefits with sodium-glucose cotransporter-2 inhibitors in HFpEF.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT04730947.

Clinical Significance of Exercise Pulmonary Hypertension With a Negative Diastolic Stress Test for Suspected Heart Failure With Preserved Ejection Fraction

BACKGROUND

Half of patients with heart failure with preserved ejection fraction (HFpEF) remain undiagnosed by resting evaluation alone. Therefore, exercise testing is proposed. The diastolic stress test (DST), however, has limited sensitivity. We aimed to determine the clinical significance of adding the mean pulmonary artery pressure over cardiac output (mPAP/CO) slope to the DST in suspected HFpEF.

METHODS AND RESULTS

In this prospective cohort study, consecutive patients (n=1936) with suspected HFpEF underwent exercise echocardiography with simultaneous respiratory gas analysis. These patients were stratified by exercise E over e' (exE/e') and mPAP/CO slope, and peak oxygen uptake, natriuretic peptides (NT-proBNP [N-terminal pro-B-type natriuretic peptide]), and score-based HFpEF likelihood were compared. Twenty-two percent of patients (n=428) had exE/e'<15 despite a mPAP/CO slope>3 mm Hg/L per min, 24% (n=464) had a positive DST (exE/e'≥15), and 54% (n=1044) had a normal DST and slope. Percentage of predicted oxygen uptake was similar in the group with exE/e'<15 but high mPAP/CO slope and the positive DST group (-2% [-5% to +1%]), yet worse than in those with normal DST and slope (-12% [-14% to -9%]). Patients with exE/e'<15 but a high slope had NT-proBNP levels and H2FPEF (heavy, hypertensive, atrial fibrillation, pulmonary hypertension, elder; filling pressure) scores intermediate to the positive DST group and the group with both a normal DST and slope.

CONCLUSIONS

Twenty-two percent of patients with suspected HFpEF presented with a mPAP/CO slope>3 mm Hg/L per min despite a negative DST. These patients had HFpEF characteristics and a peak oxygen uptake as low as patients with a positive DST. Therefore, an elevated mPAP/CO slope might indicate HFpEF irrespective of the DST result.

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.

Two-hit mouse model of heart failure with preserved ejection fraction combining diet-induced obesity and renin-mediated hypertension

Heart failure with preserved ejection fraction (HFpEF) is increasingly common but its pathogenesis is poorly understood. The ability to assess genetic and pharmacologic interventions is hampered by the lack of robust preclinical mouse models of HFpEF. We have developed a novel "2-hit" model, which combines obesity and insulin resistance with chronic pressure overload to recapitulate clinical features of HFpEF. C57BL6/NJ mice fed a high fat diet for >10 weeks were administered an AAV8-driven vector resulting in constitutive overexpression of mouse Renin1d . Control mice, HFD only, Renin only and HFD-Renin (aka "HFpEF") littermates underwent a battery of cardiac and extracardiac phenotyping. HFD-Renin mice demonstrated obesity and insulin resistance, a 2-3-fold increase in circulating renin levels that resulted in 30-40% increase in left ventricular hypertrophy, preserved systolic function, and diastolic dysfunction indicated by altered E/e', IVRT, and strain measurements; increased left atrial mass; elevated natriuretic peptides; and exercise intolerance. Transcriptomic and metabolomic profiling of HFD-Renin myocardium demonstrated upregulation of pro-fibrotic pathways and downregulation of metabolic pathways, in particular branched chain amino acid catabolism, similar to findings in human HFpEF. Treatment of these mice with the sodium-glucose cotransporter 2 inhibitor empagliflozin, an effective but incompletely understood HFpEF therapy, improved exercise tolerance, left heart enlargement, and insulin homeostasis. The HFD-Renin mouse model recapitulates key features of human HFpEF and will enable studies dissecting the contribution of individual pathogenic drivers to this complex syndrome. Addition of HFD-Renin mice to the preclinical HFpEF model platform allows for orthogonal studies to increase validity in assessment of interventions.

NEW & NOTEWORTHY

Heart failure with preserved ejection fraction (HFpEF) is a complex disease to study due to limited preclinical models. We rigorously characterize a new two-hit HFpEF mouse model, which allows for dissecting individual contributions and synergy of major pathogenic drivers, hypertension and diet-induced obesity. The results are consistent and reproducible in two independent laboratories. This high-fidelity pre-clinical model increases the available, orthogonal models needed to improve our understanding of the causes and assessment treatments for HFpEF.

Impaired longitudinal systolic-diastolic coupling and cardiac response to exercise in patients with hypertrophic cardiomyopathy

BACKGROUND

In patients with hypertrophic cardiomyopathy (HCM), impaired augmentation of stroke volume and diastolic dysfunction contribute to exercise intolerance. Systolic-diastolic (S-D) coupling characterizes how systolic contraction of the left ventricle (LV) primes efficient elastic recoil during early diastole. Impaired S-D coupling may contribute to the impaired cardiac response to exercise in patients with HCM.

METHODS

Patients with HCM (n = 25, age = 47 ± 9 years) and healthy adults (n = 115, age = 49 ± 10 years) underwent a cardiopulmonary exercise testing (CPET) and echocardiogram. S-D coupling was defined as the ratio of LV longitudinal excursion of the mitral annulus during early diastole (EDexc) and systole (Sexc) and compared between groups. Peak oxygen uptake (peak V̇O2) (Douglas bags), cardiac index (C2H2 rebreathe), and stroke volume index (SVi) were assessed during CPET. Linear regression was performed between S-D coupling and peak V̇O2, peak cardiac index, and peak SVi.

RESULTS

S-D coupling was lower in HCM (Controls: 0.63 ± 0.08, HCM: 0.56 ± 0.10, p < 0.001). Peak V̇O2 and stroke volume reserve were lower in patients with HCM (Peak VO2 Controls: 28.5 ± 5.5, HCM: 23.7 ± 7.2 mL/kg/min, p < 0.001, SV reserve: Controls 39 ± 16, HCM 30 ± 18 mL, p = 0.008). In patients with HCM, S-D coupling was associated with peak V̇O2 (r = 0.47, p = 0.018), peak cardiac index (r = 0.60, p = 0.002), and peak SVi (r = 0.63, p < 0.001).

CONCLUSION

Systolic-diastolic coupling was impaired in patients with HCM and was associated with fitness and the cardiac response to exercise. Inefficient S-D coupling may link insufficient stroke volume generation, diastolic dysfunction, and exercise intolerance in HCM.

Mitral regurgitation in heart failure with preserved ejection fraction: The interplay of valve, ventricle, and atrium

Mitral regurgitation (MR) is highly prevalent among patients with heart failure and preserved ejection fraction (HFpEF). Despite this combination being closely associated with unfavourable outcomes, it remains relatively understudied. This is partly due to the inherent heterogeneity of patients with HFpEF. To address this gap, dissecting HFpEF into mechanism-based phenotypes may offer a promising avenue for advancing our comprehension of these complex intertwined conditions. This review employs the validated CircAdapt model to explore the haemodynamic implications of moderate to severe MR across a well-defined spectrum of myocardial disease, characterized by impaired relaxation and reduced myocardial compliance. Both heart failure and mitral valve disease share overlapping symptomatology, primarily attributed to elevated pulmonary pressures. The intricate mechanisms contributing to these elevated pressures are multifaceted, potentially influenced by diastolic dysfunction, left atrial myopathy, and MR. Accurate evaluation of the haemodynamic and clinical impact of MR necessitates a comprehensive approach, taking into account the characteristics of both the left atrium and left ventricle, as well as their intricate interactions, which may currently be underemphasized in diagnostic practice. This holistic assessment is imperative for enhancing our understanding and refining therapeutic strategies within this patient cohort.

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.

Systemic Arterial Oxygen Levels Differentiate Pre- and Post-capillary Predominant Hemodynamic Abnormalities During Exercise in Undifferentiated Dyspnea on Exertion

BACKGROUND

Whether systemic oxygen levels (SaO2) during exercise can provide a window into invasively derived exercise hemodynamic profiles in patients with undifferentiated dyspnea on exertion is unknown.

METHODS

We performed cardiopulmonary exercise testing with invasive hemodynamic monitoring and arterial blood gas sampling in individuals referred for dyspnea on exertion. Receiver operator analysis was performed to distinguish heart failure with preserved ejection fraction from pulmonary arterial hypertension.

RESULTS

Among 253 patients (mean ± SD, age 63 ± 14 years, 55% female, arterial O2 [PaO2] 87 ± 14 mmHg, SaO2 96% ± 4%, resting pulmonary capillary wedge pressure [PCWP] 18 ± 4mmHg, and pulmonary vascular resistance [PVR] 2.7 ± 1.2 Wood units), there was no exercise PCWP threshold, measured up to 49 mmHg, above which hypoxemia was consistently observed. Exercise PaO2 was not correlated with exercise PCWP (rho = 0.04; P = 0.51) but did relate to exercise PVR (rho = -0.46; P < 0.001). Exercise PaO2 and SaO2 levels distinguished left-heart-predominant dysfunction from pulmonary-vascular-predominant dysfunction with an area under the curve of 0.89 and 0.89, respectively.

CONCLUSION

Systemic O2 levels during exercise distinguish relative pre- and post-capillary pulmonary hemodynamic abnormalities in patients with undifferentiated dyspnea. Hypoxemia during upright exercise should not be attributed to isolated elevation in left heart filling pressures and should prompt consideration of pulmonary vascular dysfunction.

Ventilatory limitations in patients with HFpEF and obesity

Heart failure with preserved ejection fraction (HFpEF) patients have an increased ventilatory demand. Whether their ventilatory capacity can meet this increased demand is unknown, especially in those with obesity. Body composition (DXA) and pulmonary function were measured in 20 patients with HFpEF (69 ± 6 yr;9 M/11 W). Cardiorespiratory responses, breathing mechanics, and ratings of perceived breathlessness (RPB, 0-10) were measured at rest, 20 W, and peak exercise. FVC correlated with %body fat (R2 =0.51,P = 0.0006), V̇O2peak (%predicted,R2 =0.32,P = 0.001), and RPB (R2 =0.58,P = 0.0004). %Body fat correlated with end-expiratory lung volume at rest (R2 =0.76,P < 0.001), 20 W (R2 =0.72,P < 0.001), and peak exercise (R2 =0.74,P < 0.001). Patients were then divided into two groups: those with lower ventilatory reserve (FVC<3 L,2 M/10 W) and those with higher ventilatory reserve (FVC>3.8 L,7 M/1 W). V̇O2peak was ∼22% less (p < 0.05) and RPB was twice as high at 20 W (p < 0.01) in patients with lower ventilatory reserve. Ventilatory reserves are limited in patients with HFpEF and obesity; indeed, the margin between ventilatory demand and capacity is so narrow that exercise capacity could be ventilatory limited in many patients.

Neural control of the circulation during exercise in heart failure with reduced and preserved ejection fraction

Patients with heart failure with reduced (HFrEF) and preserved ejection fraction (HFpEF) exhibit severe exercise intolerance that may be due, in part, to inappropriate cardiovascular and hemodynamic adjustments to exercise. Several neural mechanisms and locally released vasoactive substances work in concert through complex interactions to ensure proper adjustments to meet the metabolic demands of the contracting skeletal muscle. Specifically, accumulating evidence suggests that disease-related alterations in neural mechanisms (e.g., central command, exercise pressor reflex, arterial baroreflex, and cardiopulmonary baroreflex) contribute to heightened sympathetic activation and impaired ability to attenuate sympathetic vasoconstrictor responsiveness that may contribute to reduced skeletal muscle blood flow and severe exercise intolerance in patients with HFrEF. In contrast, little is known regarding these important aspects of physiology in patients with HFpEF, though emerging data reveal heightened sympathetic activation and attenuated skeletal muscle blood flow during exercise in this patient population that may be attributable to dysregulated neural control of the circulation. The overall goal of this review is to provide a brief overview of the current understanding of disease-related alterations in the integrative neural cardiovascular responses to exercise in both HFrEF and HFpEF phenotypes, with a focus on sympathetic nervous system regulation during exercise.

Diastolic exercise stress testing in heart failure with preserved ejection fraction: The DEST-HF study

AIMS

Pulmonary capillary wedge pressure (PAWP) ≥25 mmHg during bicycle ergometry is recommended to uncover occult heart failure with preserved ejection fraction. We hypothesized that PAWP increase would differ in available diastolic stress tests and that the margin of PAWP ≥25 mmHg would only be reliably achieved through ergometry.

METHODS AND RESULTS

We conducted a prospective, single-arm study in patients with an intermediate risk for heart failure with preserved ejection fraction according to the ESC HFA-PEFF score. A total of 19 patients underwent four stress test modalities in randomized order: leg raise, fluid challenge, handgrip, and bicycle ergometry. The primary outcome was the difference (Δ) between resting and exercise PAWP in each modality. Secondary outcomes were differences (Δ) in mean pulmonary artery pressure (mPAP), cardiac output (CO), as well as the ratios between mPAP and PAWP to CO. Compared to resting values, passive leg raise (Δ7.7 ± 8.0 mmHg, p = 0.030), fluid challenge (Δ9.2 ± 6.4 mmHg, p = 0.003), dynamic handgrip (Δ9.6 ± 7.5 mmHg, p = 0.002), and bicycle ergometry (Δ22.3 ± 5.0 mmHg, p < 0.001) uncovered increased PAWP during exercise. Amongst these, bicycle ergometry also demonstrated the highest ΔmPAP (27.2 ± 7.1 mmHg, p < 0.001), ΔCO (3.3 ± 2.6 L/min, p < 0.001), ΔmPAP/CO ratio (2.3 ± 2.0 mmHg/L/min, p < 0.001), and ΔPAWP/CO ratio (2.2 ± 1.4 mmHg/L/min, p < 0.001) compared to other modalities. PAWP ≥25 mmHg was only reliably achieved in bicycle ergometry (31.1 ± 3.9 mmHg). In all other modalities only 10.5% of patients achieved PAWP ≥25 mmHg (handgrip 18.4 ± 6.6 mmHg, fluid 18.1 ± 5.6 mmHg, leg raise 16.5 ± 7.0 mmHg).

CONCLUSIONS

We demonstrate that bicycle ergometry exhibits a distinct haemodynamic response with higher increase of PAWP compared to other modalities. This finding needs to be considered for valid detection of exercise PAWP ≥25 mmHg when non-bicycle tests remain inconclusive.

Reducing Pulmonary Capillary Wedge Pressure During Exercise Exacerbates Exertional Dyspnea in Patients With Heart Failure With Preserved Ejection Fraction: Implications for V˙/Q˙ Mismatch

BACKGROUND

The primary cause of dyspnea on exertion in heart failure with preserved ejection fraction (HFpEF) is presumed to be the marked rise in pulmonary capillary wedge pressure during exercise; however, this hypothesis has never been tested directly. Therefore, we evaluated invasive exercise hemodynamics and dyspnea on exertion in patients with HFpEF before and after acute nitroglycerin (NTG) treatment to lower pulmonary capillary wedge pressure.

RESEARCH QUESTION

Does reducing pulmonary capillary wedge pressure during exercise with NTG improve dyspnea on exertion in HFpEF?

STUDY DESIGN AND METHODS

Thirty patients with HFpEF performed two invasive 6-min constant-load cycling tests (20 W): one with placebo (PLC) and one with NTG. Ratings of perceived breathlessness (0-10 scale), pulmonary capillary wedge pressure (right side of heart catheter), and arterial blood gases (radial artery catheter) were measured. Measurements of V˙/Q˙ matching, including alveolar dead space (Vdalv; Enghoff modification of the Bohr equation) and the alveolar-arterial Po2 difference (A-aDO2; alveolar gas equation), were also derived. The ventilation (V˙e)/CO2 elimination (V˙co2) slope was also calculated as the slope of the V˙e and V˙co2 relationship, which reflects ventilatory efficiency.

RESULTS

Ratings of perceived breathlessness increased (PLC: 3.43 ± 1.94 vs NTG: 4.03 ± 2.18; P = .009) despite a clear decrease in pulmonary capillary wedge pressure at 20 W (PLC: 19.7 ± 8.2 vs NTG: 15.9 ± 7.4 mm Hg; P < .001). Moreover, Vdalv (PLC: 0.28 ± 0.07 vs NTG: 0.31 ± 0.08 L/breath; P = .01), A-aDO2 (PLC: 19.6 ± 6.7 vs NTG: 21.1 ± 6.7; P = .04), and V˙e/V˙co2 slope (PLC: 37.6 ± 5.7 vs NTG: 40.2 ± 6.5; P < .001) all increased at 20 W after a decrease in pulmonary capillary wedge pressure.

INTERPRETATION

These findings have important clinical implications and indicate that lowering pulmonary capillary wedge pressure does not decrease dyspnea on exertion in patients with HFpEF; rather, lowering pulmonary capillary wedge pressure exacerbates dyspnea on exertion, increases V˙/Q˙ mismatch, and worsens ventilatory efficiency during exercise in these patients. This study provides compelling evidence that high pulmonary capillary wedge pressure is likely a secondary phenomenon rather than a primary cause of dyspnea on exertion in patients with HFpEF, and a new therapeutic paradigm is needed to improve symptoms of dyspnea on exertion in these patients.