Prolonged mean VO2 response time in systolic heart failure: an indicator of impaired right ventricular-pulmonary vascular function

Cardiopulmonary exercise test to detect cardiac dysfunction from pulmonary vascular disease

BACKGROUND

Cardiac dysfunction from pulmonary vascular disease causes characteristic findings on cardiopulmonary exercise testing (CPET). We tested the accuracy of CPET for detecting inadequate stroke volume (SV) augmentation during exercise, a pivotal manifestation of cardiac limitation in patients with pulmonary vascular disease.

METHODS

We reviewed patients with suspected pulmonary vascular disease in whom CPET and right heart catheterization (RHC) measurements were taken at rest and at anaerobic threshold (AT). We correlated CPET-determined O2·pulseAT/O2·pulserest with RHC-determined SVAT/SVrest. We evaluated the sensitivity and specificity of O2·pulseAT/O2·pulserest to detect SVAT/SVrest below the lower limit of normal (LLN). For comparison, we performed similar analyses comparing echocardiographically-measured peak tricuspid regurgitant velocity (TRVpeak) with SVAT/SVrest.

RESULTS

From July 2018 through February 2023, 83 simultaneous RHC and CPET were performed. Thirty-six studies measured O2·pulse and SV at rest and at AT. O2·pulseAT/O2·pulserest correlated highly with SVAT/SVrest (r = 0.72, 95% CI 0.52, 0.85; p < 0.0001), whereas TRVpeak did not (r = -0.09, 95% CI -0.47, 0.33; p = 0.69). The AUROC to detect SVAT/SVrest below the LLN was significantly higher for O2·pulseAT/O2·pulserest (0.92, SE 0.04; p = 0.0002) than for TRVpeak (0.69, SE 0.10; p = 0.12). O2·pulseAT/O2·pulserest of less than 2.6 was 92.6% sensitive (95% CI 76.6%, 98.7%) and 66.7% specific (95% CI 35.2%, 87.9%) for deficient SVAT/SVrest.

CONCLUSIONS

CPET detected deficient SV augmentation more accurately than echocardiography. CPET-determined O2·pulseAT/O2·pulserest may have a prominent role for noninvasive screening of patients at risk for pulmonary vascular disease, such as patients with persistent dyspnea after pulmonary embolism.

Rosiglitazone improves insulin resistance but does not improve exercise capacity in individuals with impaired glucose tolerance: A randomized clinical study

Dysmetabolic states, such as type 2 diabetes (T2D), characterized by insulin resistance (IR), are associated with fatty liver, increased cardiovascular disease (CVD) risk, and decreased functional exercise capacity (FEC). Rosiglitazone (RO) improves exercise capacity and IR in T2D. However, the effects of RO on FEC and other markers of CVD risk in prediabetes are unknown. We hypothesized that insulin sensitization with RO would improve exercise capacity and markers of CVD risk in participants with impaired glucose tolerance (IGT). Exercise performance (peak oxygen consumption and oxygen uptake kinetics), IR (homeostasis model assessment of IR and quantitative insulin sensitivity check index), and surrogate cardiovascular endpoints (coronary artery calcium (CAC) volume and density and C-reactive protein (CRP)) were measured in participants with IGT after 12 and 18 months of RO or placebo (PL). RO did not significantly improve exercise capacity. Glycemic measures and IR were significantly lower in people on RO compared to PL at 18 months. CAC volume progression was not different between PL and RO groups. RO did not improve exercise capacity during an 18-month intervention despite improved IR and glycemia in people with IGT. Future studies should explore why effects on FEC with RO occur in T2D but not IGT. Understanding these questions may help in targeting therapeutic approaches in T2D and IGT.

Outcomes of right heart dysfunction in the acutely and severely unwell: protocol for a prospective, longitudinal observational study using multimodal assessment

INTRODUCTION

The relationship of acute right heart dysfunction (RHD) with long-term cardiopulmonary dysfunction and its' associated morbidity has not been clearly elucidated. We propose a prospective, observational study to assess the natural history of acute RHD using a combination of imaging, functional and qualitative assessment methods, including the recently described combination of simultaneous maximal effort cardiopulmonary exercise testing and stress echocardiography.

METHODS AND ANALYSIS

We propose a single-centre study of patients ≥18 years admitted to either the intensive care or respiratory close observation units with RHD on transthoracic echocardiography (TTE). Participants will undergo a repeat TTE ~72 hours after the initial study, with a final TTE performed prior to discharge in patients who have a prolonged (>1 week) stay. Inpatient clinical, biochemical and therapeutic indices will be collected contemporaneously. At ~6 months postdischarge, participants will undergo evaluation with validated symptom assessment tools (Dyspnoea-12 and PAH-SYMPACT Questionnaires) and a combined maximal effort cardiopulmonary exercise test and stress echocardiogram. This study is an observational, hypothesis-generating study with a recruitment target of 100 patients established based on typical admission rates of the relevant hospital departments. Measures of central tendency and dispersion will be used to describe the cohort. Inferential statistics will be used to compare the two a priori defined groups of those whose RHD had resolved prior to hospital discharge and those whose dysfunction persisted at time of discharge.

ETHICS AND DISSEMINATION

This study has received ethics approval from the local ethics committee (Nepean and Blue Mountains Local Health District approval, project 2021/ETH12111). Written informed consent will be sought from all patients prior to recruitment. The results will be submitted for publication in a relevant peer-reviewed journal and presented at an appropriate national/international conference.

STUDY REGISTRATION

Australian New Zealand Clinical Trials Registry, ANZCTR12623000309684.

Association of an Increased Abnormal Mitochondria Ratio in Cardiomyocytes with a Prolonged Oxygen Uptake Time Constant during Cardiopulmonary Exercise Testing of Patients with Non-ischemic Cardiomyopathy

Objective The cardiac function, blood distribution, and oxygen extraction in the muscles as well as the pulmonary function determine the oxygen uptake (VO2) kinetics at the onset of exercise. This factor is called the VO2 time constant, and its prolongation is associated with an unfavorable prognosis for heart failure (HF). The mitochondrial function of skeletal muscle is known to reflect exercise tolerance. Morphological changes and dysfunction in cardiac mitochondria are closely related to HF severity and its prognosis. Although mitochondria play an important role in generating energy in cardiomyocytes, the relationship between cardiac mitochondria and the VO2 time constant has not been elucidated. Methods We calculated the ratio of abnormal cardiac mitochondria in human myocardial biopsy samples using an electron microscope and measured the VO2 time constant during cardiopulmonary exercise testing. The VO2 time constant was normalized by the fat-free mass index (FFMI). Patients Fifteen patients with non-ischemic cardiomyopathy (NICM) were included. Patients were divided into two groups according to their median VO2 time constant/FFMI value. Results Patients with a low VO2 time constant/FFMI value had a lower abnormal mitochondria ratio than those with a high VO2 time constant/FFMI value. A multiple linear regression analysis revealed that the ratio of abnormal cardiac mitochondria was independently associated with a high VO2 time constant/FFMI. Conclusion An increased abnormal cardiac mitochondria ratio might be associated with a high VO2 time constant/FFMI value in patients with NICM.

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.

Impact of training on combined cardiopulmonary exercise test with stress echocardiography parameters in HFrEF patients

BACKGROUND

Exercise-based cardiac rehabilitation is recognized to improve quality of life in heart failure patients. However, the effects on the cardiac function are understudied. The main objective was to assess the impact of a 4-week cardiac rehabilitation program on cardiopulmonary exercise testing (CPET) combined with simultaneous echocardiography parameters in chronic heart failure (CHF) patients. The secondary aim was to investigate patients' responses to training.

METHODS

Forty-one CHF patients with reduced ejection fraction (29.3 ± 0.1%) underwent CPET and stress echocardiography before and after a 4-week of exercise-training program. Blood parameters, echocardiography and cardiopulmonary parameters were assessed before and after training. Potential echocardiography derived predictive parameters like left and right contractile reserves, left ventricle elastance, end systolic volume and right ventricle S wave response to exercise were also assessed.

RESULTS

The training program increased the peak oxygen consumption (VO₂) (P < 0.001), the peak systolic blood pressure, the left ventricular outflow tract velocity time integral (P < 0.05) and the circulatory (P < 0.001) and ventilatory (P < 0.01) powers. It also decreased the VE/VCO₂ slope (P < 0.001). As the median value of peak VO₂ gain was 17%, patients above this value were considered as responders and patients below as non-responders to training. The responders presented a higher left ventricle contractile reserve compared to non-responder patients. The peak left ventricle elastance and peak right ventricle S wave response tended to be higher in responders.

CONCLUSION

Combination of CPET and stress echocardiography may contribute to establish the disease severity stratification and to predict response to training in CHF patients with reduced ejection fraction.

Determinants of ventilatory inefficiency in transthyretin cardiac amyloidosis: The role of excessive ventilatory drive

Background and objective: Along with impaired aerobic capacity, increased slope of the relationship between ventilation (VE) and pulmonary CO2 output (VCO2), i.e., VE-VCO2 slope is a common finding in patients with cardiac amyloidosis (CA), which suggests ventilatory inefficiency. Little is known about mechanisms leading to ventilatory inefficiency in CA patients. The purpose of this investigation was to examine the factors that underlie the abnormal ventilatory efficiency in transthyretin hereditary CA patients, such as excessive ventilatory drive, inability of pulmonary blood flow to increase adequately during exercise and excessive sympathetic stimulation, which are known mechanisms of VE-VCO2 slope increase.

Methods: In this single-center retrospective observational study, consecutive patients (n = 41) with known familial transthyretin amyloidosis p.Val142Ile mutation carriers with confirmed cardiac phenotype were included.

Results: Compared with CA patients without ventilatory inefficiency (VE-VCO2 slope &lt; 36), patients with ventilatory inefficiency (VE-VCO2 slope ≥ 36) had increased inter-ventricular septum thickness, lower VO2 peak along with hyperventilation, and prolonged post-exercise heart rate recovery. By multivariate analysis, only excess of minute-ventilation at anaerobic threshold (β = 0.127; p = 0.011) remained an independent predictor of ventilatory inefficiency.

Conclusion: Our data suggest that high ventilatory stimulation during exercise leading to hyperventilation is the main determinant of ventilatory inefficiency in hereditary transthyretin cardiac amyloidosis patients. This novel finding helps to better understand the mechanism of exercise intolerance in these patients where physiological limitation may be related to both heart dysfunction and abnormal pulmonary response.

Oral iron supplementation in patients with heart failure: a systematic review and meta-analysis

AIMS

This review aimed to assess whether oral iron supplementation in a chronic heart failure (HF) population with iron deficiency (ID) or mild anaemia is safe and effective according to evidence-based medicine.

METHODS

We retrieved 1803 records from the PubMed, Embase, and the Cochrane Library databases from 1 January 1991 to 15 September 2021. The clinical outcome of oral iron supplementation for ID anaemia in patients with HF was the primary endpoint. The primary safety measures included adverse events and all-cause mortality, and efficacy measures included transferrin saturation (Tsat), ferritin levels, and the 6-min walk test (6MWT). The rate ratio (RR) was used to pool the efficacy measures.

RESULTS

Five randomized controlled trials that compared oral iron treatment for patients with the placebo group and included a combined total of 590 participants were analysed. No significant difference was found in all-cause death between oral iron treatment and placebo groups (RR = 0.77; 95% confidence intervals (CI), 0.46-1.29, Z = 0.98; P = 0.33). However, adverse events were not significantly higher in the iron treatment group (RR = 0.83; 95% CI, 0.60-1.16, Z = 1.07; P = 0.28). In addition, ferritin levels and Tsat were slightly increased after iron complex administration in patients with HF but were not statistically significant (ferritin: mean difference [MD] = 2.70, 95% CI, -2.41 to 7.81, Z = 1.04; P = 0.30; Tsat: MD = 27.42, 95% CI, -4.93 to 59.78, Z = 1.66; P = 0.10). No significant difference was found in exercise capacity, as indicated by the 6MWT results (MD = 59.60, 95% CI, -17.89 to 137.08, Z = 1.51; P = 0.13). We also analysed two non-randomized controlled trials with follow-up results showing that oral iron supplementation increased serum iron levels (MD = 28.87, 95% CI, 1.62-56.12, Z = 2.08; P = 0.04).

CONCLUSIONS

Based on the current findings, oral iron supplementation can increase serum iron levels in patients with HF and ID or mild anaemia but does not improve Tsat and 6MWT. In addition, oral iron supplementation is relatively safe.

Prolonged mean response time in older adults with cardiovascular risk compared to healthy older adults

BACKGROUND

During incremental exercise (Inc-Ex), the mean response time (MRT) of oxygen uptake (V̇O2) represents the time delay before changes in muscle V̇O2 reflect at the mouth level. MRT calculation by linear regression or monoexponential (τ') fitting of V̇O2 data are known to be highly variable, and a combination of incremental and constant load exercise (CL-Ex) is more reproducible.

METHODS

We evaluated MRT in older adults using linear regression and combination methods. We recruited 20 healthy adults (male: 9, 69.4 ± 6.8 years) and 10 cardiovascular risk subjects (male: 8, 73.0 ± 8.8 years). On day 1, they performed Inc-Ex using a 10W/min ramp protocol, for determination of the ventilatory anaerobic threshold (VAT) using the V-slope method. On day 2, they performed Inc-Ex to VAT exercise intensity and CL-Ex for 25min total. The MRT was calculated from the CL-Ex V̇O2 average and the time at equivalent V̇O2 in the Inc-Ex. We also assessed the amount of physical activity using the International Physical Activity Questionnaire short form (IPAQ-SF).

RESULTS

The MRT of healthy participants and those at cardiovascular risk were 49.2 ± 36.3 vs. 83.6 ± 45.4s (p = 0.033). Total physical activity in the IPAQ-SF was inversely correlated with MRT.

CONCLUSION

The MRT was significantly prolonged in cardiovascular risk participants compared to healthy participants, possibly related to the amount of daily physical activity. Individual MRT may be useful for adjustment of exercise intensity, but this should also be based on daily physical activity and individual condition during exercise.

Oxygen uptake kinetics and chronotropic responses to exercise are impaired in survivors of severe COVID-19

The post-acute phase of coronavirus disease 2019 (COVID-19) is often marked by several persistent symptoms and exertional intolerance, which compromise survivors’ exercise capacity. This was a cross-sectional study aiming to investigate the impact of COVID-19 on oxygen uptake (V̇o₂) kinetics and cardiopulmonary function in survivors of severe COVID-19 about 3–6 mo after intensive care unit (ICU) hospitalization. Thirty-five COVID-19 survivors previously admitted to ICU (5 ± 1 mo after hospital discharge) and 18 controls matched for sex, age, comorbidities, and physical activity level with no prior history of SARS-CoV-2 infection were recruited. Subjects were submitted to a maximum-graded cardiopulmonary exercise test (CPX) with an initial 3-min period of a constant, moderate-intensity walk (i.e., below ventilatory threshold, VT). V̇o₂ kinetics was remarkably impaired in COVID-19 survivors as evidenced at the on-transient by an 85% (P = 0.008) and 28% (P = 0.001) greater oxygen deficit and mean response time (MRT), respectively. Furthermore, COVID-19 survivors showed an 11% longer (P = 0.046) half-time of recovery of V̇o₂ (T_1/2V̇o₂) at the off-transient. CPX also revealed cardiopulmonary impairments following COVID-19. Peak oxygen uptake (V̇o_2peak), percent-predicted V̇o_2peak, and V̇o₂ at the ventilatory threshold (V̇o_2VT) were reduced by 17%, 17%, and 12% in COVID-19 survivors, respectively (all P < 0.05). None of the ventilatory parameters differed between groups (all P > 0.05). In addition, COVID-19 survivors also presented with blunted chronotropic responses (i.e., chronotropic index, maximum heart rate, and heart rate recovery; all P < 0.05). These findings suggest that COVID-19 negatively affects central (chronotropic) and peripheral (metabolic) factors that impair the rate at which V̇o₂ is adjusted to changes in energy demands.

NEW & NOTEWORTHY Our findings provide novel data regarding the impact of COVID-19 on submaximal and maximal cardiopulmonary responses to exercise. We showed that V̇o₂ kinetics is significantly impaired at both the onset (on-transient) and the recovery phase (off-transient) of exercise in these patients. Furthermore, our results suggest that survivors of severe COVID-19 may have a higher metabolic demand at a walking pace. These findings may partly explain the exertional intolerance frequently observed following COVID-19.

Exercise Testing in HFpEF: an Appraisal Through Diagnosis, Pathophysiology and Therapy A Clinical Consensus Statement of the Heart Failure Association (HFA) and European Association of Preventive Cardiology (EAPC) of the European Society of Cardiology (ESC)

Patients with heart failure with preserved ejection fraction (HFpEF) universally complain of exercise intolerance and dyspnoea as key clinical correlates. Cardiac as well as extracardiac components play a role for the limited exercise capacity, including an impaired cardiac and peripheral vascular reserve, a limitation in mechanical ventilation and/or gas exchange with reduced pulmonary vascular reserve, skeletal muscle dysfunction and iron deficiency/anaemia. Although most of these components can be differentiated and quantified through gas exchange analysis by cardiopulmonary exercise testing (CPET), the information provided by objective measures of exercise performance have not been systematically considered in the recent algorithms/scores for HFpEF diagnosis, neither by European nor US groups. The current Clinical Consensus Statement by the HFA and EAPC Association of the ESC aims at outlining the role of exercise testing and its pathophysiological, clinical and prognostic insights, addressing the implication of a thorough functional evaluation from the diagnostic algorithm to the pathophysiology and treatment perspectives of HFpEF. Along with these goals, we provide a specific analysis on the evidence that CPET is the standard for assessing, quantifying, and differentiating the origin of dyspnoea and exercise impairment and even more so when combined with echo and/or invasive hemodynamic evaluation is here provided. This will lead to improved quality of diagnosis when applying the proposed scores and may also help useful to implement the progressive characterization of the specific HFpEF phenotypes, a critical step toward the delivery of phenotype-specific treatments.

Priming Cardiac Function with Voluntary Respiratory Maneuvers and Effect on Early Exercise Oxygen Uptake

Oxygen uptake (V'O₂) at exercise onset is determined in part by acceleration of pulmonary blood flow (Q'p). Impairments in the Q'p response can decrease exercise tolerance. Prior research has shown that voluntary respiratory maneuvers can augment venous return, but the corollary impacts on cardiac function, Q'p and early-exercise V'O₂ remain uncertain. We examined a) the cardiovascular effects of 3 distinct respiratory maneuvers (abdominal, AB; rib cage, RC and deep breathing, DB) under resting conditions in healthy subjects (Protocol 1, n=13) and b) the impact of pre-exercise DB on pulmonary O₂ transfer during initiation of moderate intensity exercise (Protocol 2, n=8). In Protocol 1, echocardiographic analysis showed increased RV and LV cardiac output (RVCO and LVCO, respectively) following AB (by +23±13 and +18±15%, respectively, P<0.05), RC (+23±16; +14±15%, P<0.05) and DB (+27±21; +23±14%, P<0.05). In Protocol 2, DB performed for 12 breaths produced a pre-exercise increase in V'O₂ (+801±254 ml·min^-1 over ~ 6 s), presumably from increased Q'p followed by a reduction in pulmonary O₂ transfer during early phase exercise (first 20 s) compared to the control condition (149±51 vs 233±65 ml, P<0.05). We conclude that (1) respiratory maneuvers enhance RVCO and LVCO in healthy subjects under resting conditions, (2) AB, RC and DB have similar effects on RVCO and LVCO, and (3) DB can increase Q'p prior to exercise onset. These findings suggest that pre-exercise respiratory maneuvers may represent a promising strategy to prime V'O₂ kinetics and thereby to potentially improve exercise tolerance in patients with impaired cardiac function.

Functional improvement following direct interventional leaflet repair of severe tricuspid regurgitation

Aims

Several new percutaneous tricuspid repair systems have recently been introduced as new treatment options for severe tricuspid regurgitation (TR). Clinical improvement following percutaneous tricuspid valve leaflet repair has been demonstrated by recent studies. A possible impact on exercise capacity has not yet been reported.

Methods and results

Eleven patients with at least severe TR and successful tricuspid leaflet repair using the PASCAL Ace implant at our cardiology department were included in this analysis. All patients suffered from symptomatic right‐sided heart failure with compromised exercise capacity. Cardiopulmonary exercise testing (CPET), clinical, laboratory, and echocardiographic parameters were assessed at baseline and 3 months follow‐up. The primary endpoint was the change in maximal oxygen consumption [VO₂ max (mL/(min*kg))] at 3 months follow‐up. Secondary endpoints included improvement in TR, cardiac biomarkers, and other clinical outcomes. TR severity at 3 months follow‐up post‐PASCAL Ace implantation was significantly lower than at baseline (P = 0.004). Cardiac biomarkers including high‐sensitivity troponin T and N‐terminal pro‐brain natriuretic peptide as well as right ventricular diameter improved slightly without reaching statistical significance (P = 0.89, P = 0.32, and P = 0.06, respectively). PASCAL Ace implantation resulted in a significant improvement in cardiopulmonary exercise capacity at 3 months follow‐up compared with baseline. Mean VO₂ max improved from 9.5 ± 2.8 to 11.4 ± 3.4 mL/(min*kg) (P = 0.006), VO₂ max per cent predicted from 42 ± 12% to 50 ± 15% (P = 0.004), peak oxygen uptake from 703 ± 175 to 826 ± 198 mL/min (P = 0.004), and O₂ pulse per cent predicted from 67 ± 21% to 81 ± 25% (P = 0.011). Other CPET‐related outcomes did not show any significant change over time.

Conclusions

In this single‐centre retrospective analysis, direct tricuspid valve leaflet repair using the transcatheter PASCAL Ace implant system was associated with a reduced TR severity and improved cardiopulmonary exercise capacity.

Comparison of V̇O2-Kinetic Parameters for the Management of Heart Failure

Objective: The aim of this study was to analyze whether V̇O₂-kinetics during cardiopulmonary exercise testing (CPET) is a useful marker for the diagnosis of heart failure (HF) and to determine which V̇O₂-kinetic parameter distinguishes healthy participants and patients with HF.

Methods: A total of 526 healthy participants and 79 patients with HF between 20 and 90 years of age performed a CPET. The CPET was preceded by a 3-min low-intensity warm-up and followed by a 3-min recovery bout. V̇O₂-kinetics was calculated from the rest to exercise transition of the warm-up bout (on-kinetics), from the exercise to recovery transition following ramp test termination (off-kinetics) and from the initial delay of V̇O₂ during the warm-up to ramp test transition (ramp-kinetics).

Results: V̇O₂ off-kinetics showed the highest z-score differences between healthy participants and patients with HF. Furthermore, off-kinetics was strongly associated with V̇O_2peak. In contrast, ramp-kinetics and on-kinetics showed only minimal z-score differences between healthy participants and patients with HF. The best on- and off-kinetic parameters significantly improved a model to predict the disease severity. However, there was no relevant additional value of V̇O₂-kinetics when V̇O_2peak was part of the model.

Conclusion: V̇O₂ off-kinetics appears to be superior for distinguishing patients with HF and healthy participants compared with V̇O₂ on-kinetics and ramp-kinetics. If V̇O_2peak cannot be determined, V̇O₂ off-kinetics provides an acceptable substitute. However, the additional value beyond that of V̇O_2peak cannot be provided by V̇O₂-kinetics.

Physical activity and fitness in the community: the Framingham Heart Study

AIMS

While greater physical activity (PA) is associated with improved health outcomes, the direct links between distinct components of PA, their changes over time, and cardiorespiratory fitness are incompletely understood.

METHODS AND RESULTS

Maximum effort cardiopulmonary exercise testing (CPET) and objective PA measures [sedentary time (SED), steps/day, and moderate-vigorous PA (MVPA)] via accelerometers worn for 1 week concurrent with CPET and 7.8 years prior were obtained in 2070 Framingham Heart Study participants [age 54 ± 9 years, 51% women, SED 810 ± 83 min/day, steps/day 7737 ± 3520, MVPA 22.3 ± 20.3 min/day, peak oxygen uptake (VO2) 23.6 ± 6.9 mL/kg/min]. Adjusted for clinical risk factors, increases in steps/day and MVPA and reduced SED between the two assessments were associated with distinct aspects of cardiorespiratory fitness (measured by VO2) during initiation, early-moderate level, peak exercise, and recovery, with the highest effect estimates for MVPA (false discovery rate <5% for all). Findings were largely consistent across categories of age, sex, obesity, and cardiovascular risk. Increases of 17 min of MVPA/day [95% confidence interval (CI) 14-21] or 4312 steps/day (95% CI 3439-5781; ≈54 min at 80 steps/min), or reductions of 249 min of SED per day (95% CI 149-777) between the two exam cycles corresponded to a 5% (1.2 mL/kg/min) higher peak VO2. Individuals with high (above-mean) steps or MVPA demonstrated above average peak VO2 values regardless of whether they had high or low SED.

CONCLUSIONS

Our findings provide a detailed assessment of relations of different types of PA with multidimensional cardiorespiratory fitness measures and suggest favourable longitudinal changes in PA (and MVPA in particular) are associated with greater objective fitness.

Optimizing Outcomes in Cardiac Rehabilitation: The Importance of Exercise Intensity

Exercise based cardiac rehabilitation (CR) is recognized internationally as a class 1 clinical practice recommendation for patients with select cardiovascular diseases and heart failure with reduced ejection fraction. Over the past decade, several meta-analyses have generated debate regarding the effectiveness of exercise-based CR for reducing all-cause and cardiovascular mortality. A common theme highlighted in these meta-analyses is the heterogeneity and/or lack of detail regarding exercise prescription methodology within CR programs. Currently there is no international consensus on exercise prescription for CR, and exercise intensity recommendations vary considerably between countries from light-moderate intensity to moderate intensity to moderate-vigorous intensity. As cardiorespiratory fitness [peak oxygen uptake (VO₂peak)] is a strong predictor of mortality in patients with coronary heart disease and heart failure, exercise prescription that optimizes improvement in cardiorespiratory fitness and exercise capacity is a critical consideration for the efficacy of CR programming. This review will examine the evidence for prescribing higher-intensity aerobic exercise in CR, including the role of high-intensity interval training. This discussion will highlight the beneficial physiological adaptations to pulmonary, cardiac, vascular, and skeletal muscle systems associated with moderate-vigorous exercise training in patients with coronary heart disease and heart failure. Moreover, this review will propose how varying interval exercise protocols (such as short-duration or long-duration interval training) and exercise progression models may influence central and peripheral physiological adaptations. Importantly, a key focus of this review is to provide clinically-relevant recommendations and strategies to optimize prescription of exercise intensity while maximizing safety in patients attending CR programs.

Association between pulmonary oxygen uptake on-kinetics and acute cardiovascular responses to resistance exercise in patients with coronary artery disease: a preliminary study

[Purpose] This study aimed to examine whether pulmonary oxygen uptake on-kinetics at the onset of moderate-intensity exercise can predict acute cardiovascular responses to resistance exercise. [Participants and Methods] The association between pulmonary oxygen uptake on-kinetics and acute cardiovascular responses to a single resistance exercise session was investigated in seven patients with low-risk coronary artery disease who underwent revascularization through percutaneous coronary intervention. The participants performed a cardiopulmonary exercise test on a cycle ergometer and a single resistance exercise session at 30% of maximum voluntary contraction on a bilateral leg-extension machine 1 week after surgery. We measured the ventilatory anaerobic threshold and pulmonary oxygen uptake on-kinetics during the cardiopulmonary exercise test; left ventricular ejection fraction at rest; and heart rate, systolic blood pressure, and rate pressure product during the single resistance exercise session. [Results] Pulmonary oxygen uptake on-kinetics showed a positive association with the amount of increase in systolic blood pressure and rate pressure product during the single resistance exercise session, but had no association with the amount of increase in heart rate. Ventilatory anaerobic threshold and left ventricular ejection fraction were not associated with these parameters. [Conclusion] These data suggested that pulmonary oxygen uptake on-kinetics can be a useful evaluation index for predicting acute systolic blood pressure and rate pressure product responses to low-intensity resistance exercise 1 week after percutaneous coronary intervention in patients with low-risk coronary artery disease.

Poor right ventricular function is associated with impaired exercise capacity and ventilatory efficiency in transthyretin cardiac amyloid patients

CardioPulmonary Exercise Test (CPET) is the gold standard to evaluate functional capacity in patients at high risk of heart failure (HF). Few studies with a limited number of subjects and conflicting results, analyzed the role of CPET in patients with systemic amyloidosis. Aims of our study were the assessment of the response to exercise in patients with Transthyretin amyloid (ATTR) cardiomyopathy (CA), and the correlation of clinical, biohumoral and echocardiographic parameters with CPET parameters, such as VO₂ peak and VE/VCO₂ slope. From February 2018 to March 2019, 72 cardiac ATTR patients were prospectively enrolled and underwent a complete clinical, biohumoral, echocardiographic and CPET assessment. All patients completed the exercise stress test protocol, without any adverse event. At CPET, they achieved a mean VO₂ peak of 14 mL/Kg/min and a mean VE/VCO₂ slope of 31. The blood pressure response to exercise was inadequate in 26 (36%) patients (flat in 25 and hypotensive in 1), while 49/72 patients (69%) showed an inadequate heart rate recovery. In multivariate analysis, s' tricuspidalic was the only independent predictor of VO₂ peak, while in the two test models performed to avoid collinearity, both TAPSE and s' tricuspidalic were the strongest independent predictors of VE/VCO₂ slope. Our data demonstrate the role of right ventricular function as an independent predictor of exercise capacity and ventilatory efficiency in ATTR. In CPET evaluation, a significant proportion of patients presented an abnormal arterial pressure response and heart rate variation to exercise.

Peripheral and pulmonary effects of inorganic nitrite during exercise in heart failure with preserved ejection fraction

AIMS

To determine whether inorganic nitrite improves peripheral and pulmonary oxygen (O₂ ) transport during exercise in heart failure with preserved ejection fraction (HFpEF).

METHODS AND RESULTS

Data from two invasive, randomized, double-blind, placebo-controlled trials with matched workload exercise of inhaled and intravenous sodium nitrite were pooled for this analysis (n = 51). Directly measured O₂ consumption (VO₂ ) and blood gas data were used to evaluate the effect of nitrite on skeletal muscle O₂ conductance (Dm), VO₂ kinetics, alveolar capillary membrane O₂ conductance (D_L ), and O₂ utilization during submaximal exercise. As compared to placebo, treatment with nitrite resulted in an improvement in Dm (+4.9 ± 6.5 vs. -0.9 ± 4.3 mL/mmHg*min, P = 0.0008) as well as VO₂ kinetics measured by mean response time (-5.0 ± 6.9 vs. -0.6 ± 6.0 s, P = 0.03), with preserved O₂ utilization despite increased convective O₂ delivery through cardiac output (+0.4 ± 0.7 vs. -0.3 ± 0.9 L/min, P = 0.02). Nitrite improved D_L (+2.5 ± 6.3 vs. -2.0 ± 9.0 mL/mmHg*min, P = 0.05) with exercise, which was associated with lower pulmonary capillary pressures (r = -0.34, P = 0.02), and reduced pulmonary dead space ventilation fraction (-0.01 ± 0.05 vs. +0.02 ± 0.05, P = 0.02).

CONCLUSION

Sodium nitrite enhances skeletal muscle Dm during exercise as well as pulmonary O₂ diffusion, optimizing O₂ kinetics in tandem with increased convective O₂ delivery through cardiac output augmentation. The favourable combined pulmonary, cardiac and peripheral effects of nitrite may improve exercise tolerance in people with HFpEF and requires further investigation.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov ID NCT01932606 and NCT02262078.

The value of cardiopulmonary exercise testing in the diagnosis of pulmonary hypertension

Background

Cardiopulmonary exercise testing (CPET) continuously analyzes the gas exchange of patients during rest, exercise, recovery, and simultaneously records the response of the cardiopulmonary system. This study aimed to observe the characteristics of CPET in patients with pulmonary hypertension (PH) and to explore the cutoff value of CPET variables in detecting PH. The diagnostic value of CPET was also investigated in a subgroup of patients who had an incorrect or missed diagnosis of PH by echocardiography.

Methods

Treatment-naïve patients with suspected PH who were admitted to Fuwai Hospital from January 2017 to August 2018 were consecutively enrolled. The gold standard criterion for PH was defined as mean pulmonary artery pressure (mPAP) ≥25 mmHg at rest, measured by right heart catheterization. General clinical materials, echocardiography, hemodynamics, and CPET data of the patients were collected and compared between groups. Logistic regression analyses were performed to explore the CPET variables that were independently associated with PH. To further validate the value of CPET for diagnosing PH, the CPET cutoff values obtained from receiver operating characteristic (ROC) curve analysis were used in patients who had an incorrect or missed diagnosis by echocardiography.

Results

Five hundred and fifty-nine patients were included in the study. Among them, patients with PH had significantly poorer CPET variables. Multivariate logistic regression analysis showed that peak work rate (WR), peak oxygen uptake (VO₂), and end-tidal carbon dioxide partial pressure (PetCO₂) at the anaerobic threshold (AT) were independently associated with PH after adjustment for age, sex, and body mass index. The above three CPET variables were all negatively correlated with mPAP. The combined CPET variable including peak WR, peak VO₂ and PetCO₂ at AT had the largest area under the ROC curve for the diagnosis of PH (0.890, 95% CI: 0.852–0.927, P<0.001). The cutoff value was 0.86, and the sensitivity and specificity were 81.8% and 86.5%, respectively. Using this cutoff value, 83.7% of patients who were misdiagnosed and 67.9% of patients who had a missed diagnosis by echocardiography were identified.

Conclusions

PH patients have decreased cardiopulmonary reserve, lower exercise tolerance, and increased ineffective ventilation. The combination of peak WR, peakVO₂, and PetCO₂ at AT had increased sensitivity and specificity for the diagnosis of PH, and increased the specificity for identifying patients who had been misdiagnosed as PH by echocardiography.

N-Terminal-pro-Brain natriuretic peptide dynamics during effort phenotypes ischemic heart failure and determines prognosis regardless of ejection fraction

Ischemic heart disease leading to heart failure (HF) portends a high overall morbidity and mortality. A higher N-terminal-pro-B-type natriuretic peptide (NT-pro-BNP) at rest reflects HF severity and impaired cardiac output, most often secondary to reduced ejection fraction (EF). As an insufficient increase in cardiac output during exertion is common in all HF phenotypes, we examined the value of NT-pro-BNP during exercise testing as a risk stratification index for ischemic HF secondary to either reduced (HFrEF) or mid-ranged/preserved EF (HFmrEF/HFpEF). 213 patients (123 HFrEF; 90 HFmrEF/HFpEF) underwent cardiopulmonary exercise testing (CPET). NT-pro-BNP was determined at rest and peak exercise. The distribution of HFrEF and HFmrEF/HFpEF etiology in subjects with and without oxygen consumption trajectory flattening during CPET was similar (p > 0.05). Patients with HFrEF had higher plasma levels of NT-pro-BNP at rest and peak exercise than those with HFmrEF/HFpEF (984 vs. 780; 1012 vs. 845 pg/mL, p < 0.01, respectively), whereas ΔNT-pro-BNPpeak/rest was similar (60 vs. 50 pg/mL, p > 0.05). During the tracking period (22.4 ± 20.3 months) 34 patients died, and there were 2 cardiac transplantations and 3 LVAD implantations. In a multivariate regression model only the NT-pro-BNPpeak and ΔNT-pro-BNPpeak/rest were retained in the regression for the prediction of adverse events (Chi-square:8.97, p = 0.003). ROC analysis demonstrated that NT-pro-BNPpeak ≥1506 pg/mL and ΔNT-pro-BNPpeak/rest ≥108 pg/mL were optimal for identifying patients with a risk (Sn = 76.9, 74.4 %; Sp = 84.7, 80.9 %, respectively). NT-pro-BNP changes during effort and absolute peak values reached provide novel insights emerging as new and strong predictors of adverse events in HF of any EF.

Dyspnea Postpulmonary Embolism From Physiological Dead Space Proportion and Stroke Volume Defects During Exercise

BACKGROUND

Many patients with pulmonary embolism (PE) report dyspnea on exertion following long-term treatment. Increased physiological dead space proportion (V_D/V_T) and decreased cardiac stroke volume reserve may distinguish persistent effects of PE itself from symptoms reflecting comorbid conditions or deconditioning.

METHODS

This retrospective study analyzed a consecutive series of incremental symptom-limited cardiopulmonary exercise tests that had been ordered to evaluate persistent dyspnea on exertion following long-term treatment for acute PE. Physiological V_D/V_T was determined at anaerobic threshold from exhaled CO₂ and transcutaneous Pco₂ (validated against Paco₂ measurements). Cardiac stroke volume reserve was estimated at rest and at anaerobic threshold by using oxygen consumption/pulse and previously validated estimates of the arteriovenous oxygen content difference.

RESULTS

Cardiopulmonary exercise tests were performed on 40 patients with post-PE dyspnea. In 65.0% (95% CI, 50.2-79.8), V_D/V_T at anaerobic threshold was abnormally elevated, stroke volume reserve was decreased, or both defects occurred. V_D/V_T at anaerobic threshold was abnormally elevated (≥ 0.27) in 35.0% (95% CI, 20.2-49.8). V_D/V_T at anaerobic threshold significantly correlated with the extent of unmatched perfusion defects on subsequent ventilation-perfusion scans (P = .0085). In 55.0% (95% CI, 39.6-70.4), stroke volume reserve at anaerobic threshold was abnormally decreased (≤ 128% of the resting value). Both defects were present in 25.0% (95% CI, 11.6-38.4).

CONCLUSIONS

Increased V_D/V_T at anaerobic threshold and decreased stroke volume reserve during exercise are common among patients with dyspnea on exertion after long-term treatment of PE. The defects can be disclosed noninvasively by using cardiopulmonary exercise testing.

Impaired oxygen uptake kinetics in heart failure with preserved ejection fraction

Objective

The time needed to increase oxygen utilisation to meet metabolic demand (V̇O2 kinetics) is impaired in heart failure (HF) with reduced ejection fraction and is an independent risk factor for HF mortality. It is not known if V̇O2 kinetics are slowed in HF with preserved ejection fraction (HFpEF). We tested the hypothesis that V̇O2 kinetics are slowed during submaximal exercise in HFpEF and that slower V̇O2 kinetics are related to impaired peripheral oxygen extraction.

Methods

Eighteen HFpEF patients (68±7 years, 10 women) and 18 healthy controls (69±6 years, 10 women) completed submaximal and peak exercise testing. Cardiac output (acetylene rebreathing, Q̇c), ventilatory oxygen uptake (V̇O2, Douglas bags) and arterial-venous O2 difference (a-vO2 difference) derived from Q̇c and V̇O2 were assessed during exercise. Breath-by-breath O2 uptake was measured continuously throughout submaximal exercise, and V̇O2 kinetics was quantified as mean response time (MRT).

Results

HFpEF patients had markedly slowed V̇O2 kinetics during submaximal exercise (MRT: control: 40.1±14.2, HFpEF: 65.4±27.7 s; p<0.002), despite no relative impairment in submaximal cardiac output (Q̇c: control: 8.6±1.7, HFpEF: 9.7±2.2 L/min; p=0.79). When stratified by MRT, HFpEF with an MRT ≥60 s demonstrated elevated Q̇c, and impaired peripheral oxygen extraction that was apparent during submaximal exercise compared with HFpEF with a MRT <60 s (submaximal a-vO2 difference: MRT <60 s: 9.7±2.1, MRT ≥60 s: 7.9±1.1 mL/100 mL; p=0.03).

Conclusion

HFpEF patients have slowed V̇O2 kinetics that are related to impaired peripheral oxygen utilisation. MRT can identify HFpEF patients with peripheral limitations to submaximal exercise capacity and may be a target for therapeutic intervention.

Prognostic Role of Cardiopulmonary Exercise Testing in Clinical Practice

Risk stratification is a mainstay in the care of cardiac and pulmonary disorders, as the identification of adverse outcomes helps provide measures to improve survival and quality of life. The cardiopulmonary exercise test is a useful prognostic tool in the clinical evaluation of several pathological conditions, such as heart diseases, respiratory disorders, and pulmonary hypertension. If not contraindicated, a cardiopulmonary exercise test should always be performed and integrated with clinical, laboratory, and hemodynamic parameters to better stratify patient risk. In heart failure, the cardiopulmonary exercise test is important in all the stages of patient management, from diagnosis to risk assessment. Different exercise variables have been advocated as prognostic indicators in this condition, including peak oxygen uptake, ventilatory efficiency, respiratory patterns, and identification of the anaerobic threshold. The prognostic role of the cardiopulmonary exercise test in heart failure is amplified when included in multiparametric risk stratification methodology, currently considered the best method to assess patient outcome. In respiratory disorders and in pulmonary hypertension, cardiopulmonary exercise test parameters, focusing on ventilatory performance during exercise, may help evaluate the risk of adverse events. Finally, the cardiopulmonary exercise test may help define the presence of coexisting cardiac and respiratory disorders, a combination that leads to increased rates of disability and mortality.

A flattening oxygen consumption trajectory phenotypes disease severity and poor prognosis in patients with heart failure with reduced, mid-range, and preserved ejection fraction

BACKGROUND

In heart failure (HF), a flattening oxygen consumption (VO₂ ) trajectory during cardiopulmonary exercise test (CPET) reflects an acutely compromised cardiac output. We hypothesized that a flattening VO₂ trajectory is helpful in phenotyping disease severity and prognosis in HF with either reduced (HFrEF), mid-range (HFmrEF), or preserved (HFpEF) ejection fraction.

METHODS AND RESULTS

Overall, 319 HF patients (198 HFrEF, 80 HFmrEF, and 41 HFpEF) underwent CPET. A flattening VO₂ trajectory was tracked and defined as an inflection of VO₂ linearity as a function of work rate with a second slope downward inflection >35% extent of the first one. Peak VO₂ , the minute ventilation/carbon dioxide production (VE/VCO₂ ) slope, and the presence of exercise oscillatory ventilation (EOV) were also determined. Pulmonary artery systolic pressure (PASP) and tricuspid annular plane systolic excursion (TAPSE) were measured by echocardiography. A flattening VO₂ occurred in 92 patients (28.8%). PASP and TAPSE at rest were significantly higher and lower (P < 0.001), respectively. The primary outcome was the combination of all-cause death, heart transplantation and left ventricular assist device implantation. The secondary outcome was the primary outcome plus hospitalization for cardiac reasons. In the multivariate model including peak VO₂ , VE/VCO₂ slope, EOV and VO₂ trajectory, a flattening VO₂ trajectory and EOV were retained in the regression for primary (X² = 35.78, and 36.36, respectively; P < 0.001) and secondary (X² = 12.45 and 47.91, respectively; P < 0.001) outcomes.

CONCLUSIONS

Results point to a flattening VO₂ trajectory as a likely new and strong predictor of events in HF with any ejection fraction. Given the relation of right-sided cardiac dysfunction to pulmonary hypertension, this oxygen pattern might suggest a real-time decrease in pulmonary blood flow to the left heart.

Cardiopulmonary Exercise Testing: What Is its Value?

Compared with traditional exercise tests, cardiopulmonary exercise testing (CPET) provides a thorough assessment of exercise integrative physiology involving the pulmonary, cardiovascular, muscular, and cellular oxidative systems. Due to the prognostic ability of key variables, CPET applications in cardiology have grown impressively to include all forms of exercise intolerance, with a predominant focus on heart failure with reduced or with preserved ejection fraction. As impaired cardiac output and peripheral oxygen diffusion are the main determinants of the abnormal functional response in cardiac patients, invasive CPET has gained new popularity, especially for diagnosing early heart failure with preserved ejection fraction and exercise-induced pulmonary hypertension. The most impactful advance has recently come from the introduction of CPET combined with echocardiography or CPET imaging, which provides basic information regarding cardiac and valve morphology and function. This review highlights modern CPET use as a single or combined test that allows the pathophysiological bases of exercise limitation to be translated, quite easily, into clinical practice.

Oral Iron Therapy for Heart Failure With Reduced Ejection Fraction: Design and Rationale for Oral Iron Repletion Effects on Oxygen Uptake in Heart Failure

: Iron deficiency is present in ≈50% of patients with heart failure and is an independent predictor of mortality. Despite growing recognition of the functional and prognostic significance of iron deficiency, randomized multicenter trials exploring the use of oral iron supplementation in heart failure, a therapy that is inexpensive, readily available, and safe, have not been performed. Moreover, patient characteristics that influence responsiveness to oral iron in patients with heart failure have not been defined. Although results of intravenous iron repletion trials have been promising, regularly treating patients with intravenous iron products is both expensive and poses logistical challenges for outpatients. Herein, we describe the rationale for the Oral Iron Repletion effects on Oxygen Uptake in Heart Failure (IRONOUT HF) trial. This National Institute of Health-sponsored trial will investigate oral iron polysaccharide compared with matching placebo with the primary end point of change in exercise capacity as measured by peak oxygen consumption at baseline and at 16 weeks.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02188784.

Is Moderate Intensity Cycling Sufficient to Induce Cardiorespiratory and Biomechanical Modifications of Subsequent Running?

Walsh, JA, Dawber, JP, Lepers, R, Brown, M, and Stapley, PJ. Is moderate intensity cycling sufficient to induce cardiorespiratory and biomechanical modifications of subsequent running? J Strength Cond Res 31(4): 1078-1086, 2017-This study sought to determine whether prior moderate intensity cycling is sufficient to influence the cardiorespiratory and biomechanical responses during subsequent running. Cardiorespiratory and biomechanical variables measured after moderate intensity cycling were compared with control running at the same intensity. Eight highly trained, competitive triathletes completed 2 separate exercise tests; (a) a 10-minute control run (no prior cycling) and, (b) a 30-minute transition run (TR) (preceded by 20-minute of variable cadence cycling, i.e., run versus cycle-run). Respiratory, breathing frequency (fb), heart rate (HR), cost of running (Cr), rate constant, stride length, and stride frequency variables were recorded, normalized, and quantified at the mean response time (MRT), third minute, 10th minute (steady state), and overall for the control run (CR) and TR. Cost of running increased (p ≤ 0.05) at all respective times during the TR. The V[Combining Dot Above]E/V[Combining Dot Above]CO2 and respiratory exchange ratio (RER) were significantly (p < 0.01) elevated at the MRT and 10th minute of the TR. Furthermore, overall mean increases were recorded for Cr, V[Combining Dot Above]E, V[Combining Dot Above]E/V[Combining Dot Above]CO2, RER, fb (p < 0.01), and HR (p ≤ 0.05) during the TR. Rate constant values for oxygen uptake were significantly different between CR and TR (0.48 ± 0.04 vs. 0.89 ± 0.15; p < 0.01). Stride length decreased across all recorded points during the TR (p ≤ 0.05) and stride frequency increased at the MRT and 3 minutes (p < 0.01). The findings suggest that at moderate intensity, prior cycling influences the cardiorespiratory response during subsequent running. Furthermore, prior cycling seems to have a sustained effect on the Cr during subsequent running.

Effect of Oral Iron Repletion on Exercise Capacity in Patients With Heart Failure With Reduced Ejection Fraction and Iron Deficiency: The IRONOUT HF Randomized Clinical Trial

IMPORTANCE

Iron deficiency is present in approximately 50% of patients with heart failure with reduced left ventricular ejection fraction (HFrEF) and is an independent predictor of reduced functional capacity and mortality. However, the efficacy of inexpensive readily available oral iron supplementation in heart failure is unknown.

OBJECTIVE

To test whether therapy with oral iron improves peak exercise capacity in patients with HFrEF and iron deficiency.

DESIGN, SETTING, AND PARTICIPANTS

Phase 2, double-blind, placebo-controlled randomized clinical trial of patients with HFrEF (<40%) and iron deficiency, defined as a serum ferritin level of 15 to 100 ng/mL or a serum ferritin level of 101 to 299 ng/mL with transferrin saturation of less than 20%. Participants were enrolled between September 2014 and November 2015 at 23 US sites.

INTERVENTIONS

Oral iron polysaccharide (n = 111) or placebo (n = 114), 150 mg twice daily for 16 weeks.

MAIN OUTCOMES AND MEASURES

The primary end point was a change in peak oxygen uptake (V̇o2) from baseline to 16 weeks. Secondary end points were change in 6-minute walk distance, plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels, and health status as assessed by Kansas City Cardiomyopathy Questionnaire (KCCQ, range 0-100, higher scores reflect better quality of life).

RESULTS

Among 225 randomized participants (median age, 63 years; 36% women) 203 completed the study. The median baseline peak V̇o2 was 1196 mL/min (interquartile range [IQR], 887-1448 mL/min) in the oral iron group and 1167 mL/min (IQR, 887-1449 mL/min) in the placebo group. The primary end point, change in peak V̇o2 at 16 weeks, did not significantly differ between the oral iron and placebo groups (+23 mL/min vs -2 mL/min; difference, 21 mL/min [95% CI, -34 to +76 mL/min]; P = .46). Similarly, at 16 weeks, there were no significant differences between treatment groups in changes in 6-minute walk distance (-13 m; 95% CI, -32 to 6 m), NT-proBNP levels (159; 95% CI, -280 to 599 pg/mL), or KCCQ score (1; 95% CI, -2.4 to 4.4), all P > .05.

CONCLUSIONS AND RELEVANCE

Among participants with HFrEF with iron deficiency, high-dose oral iron did not improve exercise capacity over 16 weeks. These results do not support use of oral iron supplementation in patients with HFrEF.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT02188784.

Cardiopulmonary Exercise Testing in Heart Failure

Exercise intolerance, indicated by dyspnea and fatigue during exertion, is a cardinal manifestation of heart failure (HF). Cardiopulmonary exercise testing (CPET) precisely defines maximum exercise capacity through measurement of peak oxygen uptake (VO2). Peak VO2 values have a critical role in informing patient selection for advanced HF interventions such as heart transplantation and ventricular assist devices. Oxygen uptake and ventilatory patterns obtained during the submaximal portion of CPET are also valuable to recognize because of their ease of ascertainment during low-level exercise, relevance to ability to perform activities of daily living, independence from volitional effort, and strong relationship to prognosis in HF. The ability of peak VO2 and other CPET variables to be measured reproducibly and to accurately reflect HF severity is increasingly recognized and endorsed by scientific statements. Integration of CPET with invasive hemodynamic monitoring and cardiac imaging during exercise provides comprehensive characterization of multisystem reserve capacity that can inform prognosis and the need for cardiac interventions. Here, we review both practical aspects of conducting CPETs in patients with HF for clinical and research purposes as well as interpretation of gas exchange patterns across the spectrum of preclinical HF to advanced HF.

Neuromuscular and physiological variables evolve independently when running immediately after cycling

During the early period of running after cycling, EMG patterns of the leg are modified in only some highly trained triathletes. The majority of studies have analysed muscle EMG patterns at arbitrary, predetermined time points. The purpose of this study was to examine changes to EMG patterns of the lower limb at physiologically determined times during the cycle-run transition period to better investigate neuromuscular adaptations. Six highly trained triathletes completed a 10 m in isolated run (IR), 30 min of rest, then a 20 min cycling procedure, before a 10 min transition run (C-R). Surface EMG activity of eight lower limb muscles was recorded, normalised and quantified at four time points. Oxygen uptake and heart rate values were also collected. Across all muscles, mean (± SD) EMG patterns, demonstrated significant levels of reproducibility for each participant at all four time points (α < 0.05; r = 0.52-0.97). Mean EMG patterns during C-R correlated highly with the IR patterns (α < 0.05). These results show that EMG patterns during subsequent running are not significantly affected by prior cycling. However, variability of muscle recruitment activity does appear to increase during C-R transition when compared to IR.

Soothing the sleeping giant: improving skeletal muscle oxygen kinetics and exercise intolerance in HFpEF

Patients with heart failure with preserved ejection fraction (HFpEF) have similar degrees of exercise intolerance and dyspnea as patients with heart failure with reduced EF (HFrEF). The underlying pathophysiology leading to impaired exertional ability in the HFpEF syndrome is not completely understood, and a growing body of evidence suggests "peripheral," i.e., noncardiac, factors may play an important role. Changes in skeletal muscle function (decreased muscle mass, capillary density, mitochondrial volume, and phosphorylative capacity) are common findings in HFrEF. While cardiac failure and decreased cardiac reserve account for a large proportion of the decline in oxygen consumption in HFrEF, impaired oxygen diffusion and decreased skeletal muscle oxidative capacity can also hinder aerobic performance, functional capacity and oxygen consumption (V̇o2) kinetics. The impact of skeletal muscle dysfunction and abnormal oxidative capacity may be even more pronounced in HFpEF, a disease predominantly affecting the elderly and women, two demographic groups with a high prevalence of sarcopenia. In this review, we 1) describe the basic concepts of skeletal muscle oxygen kinetics and 2) evaluate evidence suggesting limitations in aerobic performance and functional capacity in HFpEF subjects may, in part, be due to alterations in skeletal muscle oxygen delivery and utilization. Improving oxygen kinetics with specific training regimens may improve exercise efficiency and reduce the tremendous burden imposed by skeletal muscle upon the cardiovascular system.

Is exercise good for the right ventricle? Concepts for health and disease

There is substantial evidence supporting the prescription of exercise training in patients with left-sided heart disease, but data on the effects of exercise are far more limited for conditions that primarily affect the right ventricle. There is evolving evidence that right ventricular (RV) function is of critical importance to circulatory function during exercise. Even in healthy individuals with normal pulmonary vascular function, the hemodynamic load on the right ventricle increases relatively more during exercise than that of the left ventricle, and this disproportionate load is far greater in patients with pulmonary hypertension. Exercise-induced increases in pulmonary artery pressures can exceed RV contractile reserve (so-called arterioventricular uncoupling), resulting in attenuated cardiac output and exercise intolerance. In this review, we explore the spectrum of RV reserve-from transient RV dysfunction observed in athletes after extreme bouts of intense endurance exercise to RV failure with minimal exertion in patients with advanced pulmonary hypertension. Recent advances and novel approaches to echocardiographic and cardiac magnetic resonance imaging have provided more accurate means of assessing the right ventricle and pulmonary circulation during exercise such that quantification of exercise reserve may provide a valuable means of assessing prognosis and response to therapies. We discuss the potential benefits and risks of exercise training in both health and disease while recognizing the need for prospective studies that assess the long-term efficacy and safety of exercise interventions in patients with pulmonary vascular and RV pathologic conditions.

Role of Right Ventricle and Dynamic Pulmonary Hypertension on Determining ΔVO 2 /ΔWork Rate Flattening

Background—

Several cardiovascular diseases are characterized by an impaired O 2 kinetic during exercise. The lack of a linear increase of Δoxygen consumption (V O 2 )/ΔWork Rate (WR) relationship, as assessed by expired gas analysis, is considered an indicator of abnormal cardiovascular efficiency. We aimed at describing the frequency of ΔVO 2 /ΔWR flattening in a symptomatic population of cardiac patients, characterizing its functional profile, and testing the hypothesis that dynamic pulmonary hypertension and right ventricular contractile reserve play a major role as cardiac determinants.

Methods and Results—

We studied 136 patients, with different cardiovascular diseases, referred for exertional dyspnoea. Cardiopulmonary exercise test combined with simultaneous exercise echocardiography was performed using a symptom-limited protocol. ΔVO 2 /ΔWR flattening was observed in 36 patients (group A, 26.5% of population) and was associated with a globally worse functional profile (reduced peak V O 2 , anaerobic threshold, O 2 pulse, impaired VE/VCO 2 ). At univariate analysis, exercise ejection fraction, exercise mitral regurgitation, rest and exercise tricuspid annular plane systolic excursion, exercise systolic pulmonary artery pressure, and exercise cardiac output were all significantly ( P <0.05) impaired in group A. The multivariate analysis identified exercise systolic pulmonary artery pressure (odds ratio, 1.06; confidence interval, 1.01–1.11; P =0.01) and exercise tricuspid annular plane systolic excursion (odds ratio, 0.88; confidence interval, 0.80–0.97; P =0.01) as main cardiac determinants of ΔVO 2 /ΔWR flattening; female sex was strongly associated (odds ratio, 6.10; confidence interval, 2.11–17.7; P <0.01).

Conclusions—

In patients symptomatic for dyspnea, the occurrence of ΔVO 2 /ΔWR flattening reflects a significantly impaired functional phenotype whose main cardiac determinants are the excessive systolic pulmonary artery pressure increase and the reduced peak right ventricular longitudinal systolic function.

Effect of exercise training on pulmonary oxygen uptake kinetics in heart transplant recipients

Pulmonary oxygen uptake (V˙O2p) at exercise onset is severely delayed in heart transplant recipients (HTRs). The role of exercise training to improve V˙O2p kinetics in HTRs has not been studied. We examined V˙O2p kinetics before and after 12 weeks of aerobic and strength training (HTR-T; n = 19, mean ± SD age: 57 ± 10 years) or usual care (HTR-UC; n = 16, mean age: 58 ± 12 years). Phase II V˙O2p kinetics, reflecting the rate of muscle metabolic adaptation, improved 37% after training compared with usual care (HTR-UC, 15 ± 19 vs 2 ± 13 seconds improvement, p = 0.02). The change in rest to steady-state heart rate reserve before and after 12 weeks was not different in HTR-T (-2 ± 9 beats/min) and HTR-UC (-1 ± 7 beats/min; p = 0.78). No significant relation was found between the change in V˙O2p kinetics and rest to steady-state heart rate reserve. Changes in leg lean tissue mass and V˙O2p kinetics were significantly related (r = -0.46, p = 0.008). In conclusion, a favorable adaptation in skeletal muscle oxidative function may underpin our finding of faster V˙O2p kinetics in HTRs after exercise training.