Physiological determinants of decreased peak leg oxygen uptake in chronic disease: a systematic review and meta-analysis

This systematic review and meta-analysis examined the physiological mechanisms responsible for lower peak exercise leg oxygen uptake (V̇o2) in patients with chronic disease. Studies measuring peak leg V̇o2 (primary outcome) and its physiological determinants during large (cycle) or small muscle mass exercise (single-leg knee extension, SLKE) in patients with chronic disease were included in this meta-analysis. Pooled estimates for each outcome were reported as a weighted mean difference (WMD) between chronic disease and controls. We included 10 studies that measured peak leg V̇o2 in patients with chronic disease (n = 109, mean age: 45 yr; encompassing chronic obstructive pulmonary disease, COPD, heart failure with reduced ejection fraction, HFrEF, or chronic renal failure, RF) and age-matched controls (n = 88). In pooled analysis, peak leg V̇o2 (WMD; -0.23 L/min, 95% CI: -0.32 to -0.13), leg oxygen (O2) delivery (WMD: -0.27 L/min, 95% CI: -0.37 to -0.17), and muscle O2 diffusive conductance (WMD: -5.2 mL/min/mmHg, 95% CI: -7.1 to -3.2) were all significantly lower during cycle and SLKE exercise in chronic disease versus controls. These results highlight that during large and small muscle mass exercise in patients with COPD, HFrEF, or RF, there is no single factor causing peak V̇o2 limitations. Specifically, the lower peak V̇o2 in these pathologies is due to not only the expected impairments in convective O2 delivery but also impairments in muscle oxygen diffusive transport from capillary to mitochondria. Whether impaired muscle O2 transport is caused solely by inactivity or additional muscle pathology remains in question.NEW & NOTEWORTHY Peripheral (skeletal muscle and vasculature) factors contribute significantly to reduced exercise capacity during both large and small muscle mass exercise in chronic diseases such as COPD, HFrEF, or RF and should be important targets of therapy in addition to the primary organs (lungs, heart, and kidneys) affected by disease.

Determinants of Impaired Peak Oxygen Uptake in Breast Cancer Survivors: JACC: CardioOncology Primer

•Exercise intolerance is common among breast cancer survivors.•Exercise intolerance in breast cancer survivors is related to cardiac, vascular, and skeletal muscle impairments.•Holistic rehabilitation or pharmacological therapies are needed to address these impairments.

A Review on the Role of Exercise Training to Prevent a Decline in Cardiorespiratory Fitness and Cardiac Function in Breast Cancer Survivors

PURPOSE

Improvements in diagnosis and treatment mean that the long-term health of breast cancer survivors (BCS) is increasingly dictated by cardiovascular comorbidities. This is partly a consequence of exposure to cardiotoxic therapies, which result in cardiac dysfunction and decreased cardiorespiratory fitness (CRF). Exercise training (ExT) is a key therapeutic strategy for secondary prevention and increasing CRF in adults with established cardiovascular disease. Exercise-based cardio-oncology rehabilitation (CORE) has been proposed as an emerging strategy to address CRF and cardiac impairment in BCS. This review aims to (1) provide an overview of the impact of breast cancer therapy on CRF; (2) provide an up-to-date summary of the effects of ExT on CRF and cardiac function in BCS undergoing cardiotoxic therapy; and (3) discuss how traditional ExT approaches can be adapted for BCS undergoing therapy.

REVIEW METHODS

A literature review was performed based on an intensive literature search for systematic reviews and meta-analyses, randomized and non-randomized controlled trials and single-arm trials investigating the impact of exercise training or cardiac rehabilitation on CRF and/or cardiac function in BCS who are undergoing or have completed cardiotoxic cancer therapy.

SUMMARY

Overall, current evidence suggests that ExT induces clinically meaningful benefits for CRF in BCS during and after therapy. There is also emerging evidence that ExT can improve peak exercise measures of cardiac function; however, there is a need for further research to understand how to adapt these effective ExT approaches into clinical CORE-based settings.

Effect of Exercise Training on Peak Aerobic Power After Heart Transplantation: A Brief Review

Heart transplantation (HTP) is a life-saving therapy for selected individuals with end-stage refractory heart failure. Despite improvements in quality of life and survival, HTP recipients' peak aerobic power (peak VO2) remains up to 50% lower than age-matched healthy control subjects owing to abnormal cardiovascular and skeletal muscle function. Currently, little is known regarding the effect of exercise training (ET) to improve peak VO2 after HTP. This brief review aims to summarise existing evidence regarding the role of ET on peak VO2 and its determinants, highlights the upper limits of endurance performance in highly trained HTP athletes, and identifies areas for future HTP exercise rehabilitation research.

Understanding Exercise Capacity: From Elite Athlete to HFpEF

Exercise capacity is a spectrum that reflects an individual's functional capacity and the dynamic nature of cardiac remodelling along with respiratory and skeletal muscle systems. The relationship of increasing physical activity, increased cardiac mass and volumes, and improved cardiorespiratory fitness (CRF) is well established in the endurance athlete. However, less emphasis has been placed on the other end of the spectrum, which includes individuals with a more sedentary lifestyle and small hearts who are at increased risk of functional disability and poor clinical outcomes. Reduced CRF is an independent predictor of all-cause mortality and cardiovascular events determined by multiple inter-related exogenous and endogenous factors. In this review, we explore the relationship of physical activity, cardiac remodelling, and CRF across the exercise spectrum, emphasising the critical role of cardiac size in determining exercise capacity. In contrast to the large compliant left ventricle of the endurance athlete, an individual with a lifetime of physical inactivity is likely to have a small, stiff heart with reduced cardiac reserve. We propose that this might contribute to the development of heart failure with preserved ejection fraction in certain individuals, and is key to understanding the link between low CRF and increased risk of heart failure.

Cardio-oncology and Cancer Rehabilitation: Is an Integrated Approach Possible?

With significant improvements in the understanding of cancer biology, improved detection, and the use of novel adjuvant therapies, each year more Canadians are surviving a cancer diagnosis. Despite their effectiveness these therapies often result in short- and long-term deleterious effects to major organ systems, particularly cardiovascular. Cardio-oncology is an emerging field of study with the aim to improve cardiovascular health across the oncology disease spectrum. International guidelines distinguish "cardio-oncology" rehabilitation from "cancer" rehabilitation, but how this is navigated is currently unknown. How such care should be assessed and integrated acutely or in the longer term remains unknown. Accordingly, the aim of this article is to consider the cancer patient's needs beyond the scope of cardio-oncology rehabilitation to holistically integrate cancer rehabilitation across the disease trajectory.

Rationale and design of IMPACT-women: a randomised controlled trial of the effect of time-restricted eating, healthy eating and reduced sedentary behaviour on metabolic health during chemotherapy for early-stage breast cancer

Metabolic dysfunction and excess accumulation of adipose tissue are detrimental side effects from breast cancer treatment. Diet and physical activity are important treatments for metabolic abnormalities, yet patient compliance can be challenging during chemotherapy treatment. Time-restricted eating (TRE) is a feasible dietary pattern where eating is restricted to 8 h/d with water-only fasting for the remaining 16 h. The purpose of this study is to evaluate the effect of a multimodal intervention consisting of TRE, healthy eating, and reduced sedentary time during chemotherapy treatment for early-stage (I-III) breast cancer on accumulation of visceral fat (primary outcome), other fat deposition locations, metabolic syndrome and cardiovascular disease risk (secondary outcomes) compared with usual care. The study will be a two-site, two-arm, parallel-group superiority randomised control trial enrolling 130 women scheduled for chemotherapy for early-stage breast cancer. The intervention will be delivered by telephone, including 30-60-minute calls with a registered dietitian who will provide instructions on TRE, education and counselling on healthy eating, and goal setting for reducing sedentary time. The comparison group will receive usual cancer and supportive care including a single group-based nutrition class and healthy eating and physical activity guidelines. MRI, blood draws and assessment of blood pressure will be performed at baseline, after chemotherapy (primary end point), and 2-year follow-up. If our intervention is successful in attenuating the effect of chemotherapy on visceral fat accumulation and cardiometabolic dysfunction, it has the potential to reduce risk of cardiometabolic disease and related mortality among breast cancer survivors.

Exercise during Hemodialysis in Patients with Chronic Kidney Failure

Exercise during Hemodialysis in Patients with Chronic Kidney FailureThe authors report on a trial of an exercise intervention provided during dialysis sessions for patients with chronic renal failure. They found that the intervention is safe and improves physical function.

Cardiovascular responses to static handgrip exercise and postexercise ischemia in heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) is characterized by reduced ability to sustain physical activity that may be due partly to disease-related changes in autonomic function that contribute to dysregulated cardiovascular control during muscular contraction. Thus, we used a combination of static handgrip exercise (HG) and postexercise ischemia (PEI) to examine the pressor response to exercise and isolate the skeletal muscle metaboreflex, respectively. Mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), and total peripheral resistance (TPR) were assessed during 2-min of static HG at 30 and 40% of maximum voluntary contraction (MVC) and subsequent PEI in 16 patients with HFpEF and 17 healthy, similarly aged controls. Changes in MAP were lower in patients with HFpEF compared with controls during both 30%MVC (Δ11 ± 7 vs. Δ15 ± 8 mmHg) and 40%MVC (Δ19 ± 14 vs. Δ30 ± 8 mmHg), and a similar pattern of response was evident during PEI (30%MVC: Δ8 ± 5 vs. Δ12 ± 8 mmHg; 40%MVC: Δ13 ± 10 vs. Δ18 ± 9 mmHg) (group effect: P = 0.078 and P = 0.017 at 30% and 40% MVC, respectively). Changes in HR, CO, and TPR did not differ between groups during HG or PEI (P > 0.05). Taken together, these data suggest a reduced pressor response to static muscle contractions in patients with HFpEF compared with similarly aged controls that may be mediated partly by a blunted muscle metaboreflex. These findings support a disease-related dysregulation in neural cardiovascular control that may reduce an ability to sustain physical activity in HFpEF.NEW & NOTEWORTHY The current investigation has identified a diminution in the exercise-induced rise in arterial blood pressure (BP) that persisted during postexercise ischemia (PEI) in an intensity-dependent manner in patients with heart failure with preserved ejection fraction (HFpEF) compared with older, healthy controls. These findings suggest that the pressor response to exercise is reduced in patients with HFpEF, and this deficit may be mediated, in part, by a blunted muscle metaboreflex, highlighting the consequences of impaired neural cardiovascular control during exercise in this patient group.

Too Little of a Good Thing: Strong Associations Between Cardiac Size and Fitness Among Women

BACKGROUND

Cardiorespiratory fitness (CRF) is associated with functional impairment and cardiac events, particularly heart failure (HF). However, the factors predisposing women to low CRF and HF remain unclear.

OBJECTIVES

This study sought to evaluate the association between CRF and measures of ventricular size and function and to examine the potential mechanism linking these factors.

METHODS

A total of 185 healthy women aged >30 years (51 ± 9 years) underwent assessment of CRF (peak volume of oxygen uptake [Vo2peak]) and biventricular volumes at rest and during exercise by using cardiac magnetic resonance (CMR). The relationships among Vo2peak, cardiac volumes, and echocardiographic measures of systolic and diastolic function were assessed using linear regression. The effect of cardiac size on cardiac reserve (change in cardiac function during exercise) was assessed by comparing quartiles of resting left ventricular end-diastolic volume (LVEDV).

RESULTS

Vo2peak was strongly associated with resting measures of LVEDV and right ventricular end-diastolic volume (R2 = 0.58-0.63; P < 0.0001), but weakly associated with measures of resting left ventricular (LV) systolic and diastolic function (R2 = 0.01-0.06; P < 0.05). Increasing LVEDV quartiles were positively associated with cardiac reserve, with the smallest quartile showing the smallest reduction in LV end-systolic volume (quartile [Q]1: -4 mL vs Q4: -12 mL), smallest augmentation in LV stroke volume (Q1: +11 mL vs Q4: +20 mL) and cardiac output (Q1: +6.6 L/min vs Q4: +10.3 L/min) during exercise (interaction P < 0.001 for all).

CONCLUSIONS

A small ventricle is strongly associated with low CRF because of the combined effect of a smaller resting stroke volume and an attenuated capacity to increase with exercise. The prognostic implications of low CRF in midlife highlight the need for further longitudinal studies to determine whether women with small ventricles are predisposed to functional impairment, exertional intolerance, and HF later in life.

Time-Restricted Eating in Breast Cancer Survivors: Effects on Body Composition and Nutritional Status

In this secondary analysis of an 8-wk single-arm feasibility study of weekday time-restricted eating (TRE), we explored the effects of TRE on body composition. Women (n = 22; ≥60 yr) who had completed chemotherapy for early-stage breast cancer and had a body mass index ≥25 kg/m² were enrolled. Bioelectrical impedance analysis was performed before and after 8 wk of TRE, and nutritional status was evaluated by bioelectrical impedance vector analysis (BIVA). Body weight (p = 0.01) and total fat mass (p = 0.04) decreased with TRE. Phase angle was low (defined as ≤5.6°) in 86% of participants at baseline and did not change. Four participants who initially presented with obesity (>95% ellipse, BIVA) had favorable body composition modifications after TRE. Our study highlighted a less favorable body composition profile, poorer cell integrity and overhydration in these patients. BIVA was a useful method to assess body composition and hydration. A short TRE intervention was associated with decreased estimated fat mass and a favorable change in nutritional status in those with obesity.

Myocardial steatosis impairs left ventricular diastolic-systolic coupling in healthy humans

Mounting evidence suggests that myocardial steatosis contributes to left ventricular diastolic dysfunction, but definitive evidence in humans is lacking due to confounding comorbidities. As such, we utilized a 48-h food restriction model to acutely increase myocardial triglyceride (mTG) content - measured by ¹ H magnetic resonance spectroscopy - in 27 young healthy volunteers (13 men/14 women). Forty-eight hours of fasting caused a more than 3-fold increase in mTG content (P < 0.001). Diastolic function - defined as early diastolic circumferential strain rate (CSRd) - was unchanged following the 48-h fasting intervention, but systolic circumferential strain rate was elevated (P < 0.001), indicative of systolic-diastolic uncoupling. Indeed, in a separate control experiment in 10 individuals, administration of low-dose dobutamine (2 μg/kg/min) caused a similar change in systolic circumferential strain rate as was found during 48 h of food restriction, along with a proportionate increase in CSRd, such that the two metrics remained coupled. Taken together, these data indicate that myocardial steatosis contributes to diastolic dysfunction by impairing diastolic-systolic coupling in healthy adults, and suggest that steatosis may contribute to the progression of heart disease. KEY POINTS: Preclinical evidence strongly suggests that myocardial lipid accumulation (termed steatosis) is an important mechanism driving heart disease. Definitive evidence in humans is limited due to the confounding influence of multiple underlying comorbidities. Using a 48-h food restriction model to acutely increase myocardial triglyceride content in young healthy volunteers, we demonstrate an association between myocardial steatosis and left ventricular diastolic dysfunction. These data advance the hypothesis that myocardial steatosis may contribute to diastolic dysfunction and suggest myocardial steatosis as a putative therapeutic target.

Effect of Training on Vascular Function and Repair in Heart Failure With Preserved Ejection Fraction

BACKGROUND

Exercise training improves peak oxygen uptake (V̇O₂peak) in heart failure with preserved ejection fraction (HFpEF). Multiple adaptations have been addressed, but the role of circulating endothelium-repairing cells and vascular function have not been well defined.

OBJECTIVES

The authors investigated effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) on vascular function and repair in HFpEF.

METHODS

This study is a subanalysis of the OptimEx-Clin Study randomizing patients with HFpEF (n = 180) to HIIT, MICT, or guideline control. At baseline, 3, and 12 months, the authors measured peripheral arterial tonometry (valid baseline measurement in n = 109), flow-mediated dilation (n = 59), augmentation index (n = 94), and flow cytometry (n = 136) for endothelial progenitor cells and angiogenic T cells. Abnormal values were defined as outside 90% of published sex-specific reference values.

RESULTS

At baseline, abnormal values (%) were observed for augmentation index in 66%, peripheral arterial tonometry in 17%, flow-mediated dilation in 25%, endothelial progenitor cells in 42%, and angiogenic T cells in 18%. These parameters did not change significantly after 3 or 12 months of HIIT or MICT. Results remained unchanged when confining analysis to patients with high adherence to training.

CONCLUSIONS

In patients with HFpEF, high augmentation index was common, but endothelial function and levels of endothelium-repairing cells were normal in most patients. Aerobic exercise training did not change vascular function or cellular endothelial repair. Improved vascular function did not significantly contribute to the V̇O₂peak improvement after different training intensities in HFpEF, contrary to previous studies in heart failure with reduced ejection fraction and coronary artery disease. (Optimizing Exercise Training in Prevention and Treatment of Diastolic Heart Failure [OptimEx-Clin]; NCT02078947).

Exercise for the Prevention of Anthracycline-Induced Functional Disability and Cardiac Dysfunction: The BREXIT Study

BACKGROUND

Breast cancer survivors treated with anthracycline-based chemotherapy (AC) have increased risk of functional limitation and cardiac dysfunction. We conducted a 12-month randomized controlled trial in 104 patients with early-stage breast cancer scheduled for AC to determine whether 12 months of exercise training (ExT) could attenuate functional disability (primary end point), improve cardiorespiratory fitness (VO₂peak), and prevent cardiac dysfunction.

METHODS

Women 40 to 75 years of age with stage I to III breast cancer scheduled for AC were randomized to 3 to 4 days per week aerobic and resistance ExT for 12 months (n=52) or usual care (UC; n=52). Functional measures were performed at baseline, at 4 weeks after AC (4 months), and at 12 months, comprising: (1) cardiopulmonary exercise testing to quantify VO₂peak and functional disability (VO₂peak ≤18.0 mL·kg^-1·min^-1); (2) cardiac reserve (response from rest to peak exercise), quantified with exercise cardiac magnetic resonance measures to determine changes in left and right ventricular ejection fraction, cardiac output, and stroke volume; (3) standard-of-care echocardiography-derived resting left ventricular ejection fraction and global longitudinal strain; and (4) biochemistry (troponin and BNP [B-type natriuretic peptide]).

RESULTS

Among 104 participants randomized, greater study attrition was observed among UC participants (P=0.031), with 93 women assessed at 4 months (ExT, n=49; UC, n=44) and 87 women assessed at 12 months (ExT, n=49; UC, n=38). ExT attenuated functional disability at 4 months (odds ratio, 0.32 [95% CI, 0.11-0.94]; P=0.03) but not at 12 months (odds ratio, 0.27 [95% CI, 0.06-1.12]; P=0.07). In a per-protocol analysis, functional disability was prevented entirely at 12 months among participants adherent to ExT (ExT, 0% versus UC, 20%; P=0.005). Compared with UC at 12 months, ExT was associated with a net 3.5-mL·kg^-1·min^-1 improvement in VO₂peak that coincided with greater cardiac output, stroke volume, and left and right ventricular ejection fraction reserve (P<0.001 for all). There was no effect of ExT on resting measures of left ventricular function. Postchemotherapy troponin increased less in ExT than in UC (8-fold versus 16-fold increase; P=0.002). There were no changes in BNP in either group.

CONCLUSIONS

In women with early-stage breast cancer undergoing AC, 12 months of ExT did not attenuate functional disability, but provided large, clinically meaningful benefits on VO₂peak and cardiac reserve.

REGISTRATION

URL: https://www.anzctr.org.au/; Unique identifier: ACTRN12617001408370.

High-intensity interval training in cardiac rehabilitation (HIIT or MISS UK): A multi-centre randomised controlled trial

BACKGROUND

There is a lack of international consensus regarding the prescription of high-intensity interval exercise training (HIIT) for people with coronary artery disease (CAD) attending cardiac rehabilitation (CR).

AIM

To assess the clinical effectiveness and safety of low-volume HIIT compared with moderate intensity steady-state (MISS) exercise training for people with CAD.

METHODS

We conducted a multi-centre RCT, recruiting 382 patients from 6 outpatient CR centres. Participants were randomised to twice-weekly HIIT (n = 187) or MISS (n = 195) for 8 weeks. HIIT consisted of 10 × 1-minute intervals of vigorous exercise (>85% maximum capacity) interspersed with 1-minute periods of recovery. MISS was 20-40 minutes of moderate intensity continuous exercise (60-80% maximum capacity). The primary outcome was the change in cardiorespiratory fitness (peak oxygen uptake, VO2 peak) at 8-week follow-up. Secondary outcomes included cardiovascular disease risk markers, cardiac structure and function, adverse events, and health-related quality of life.

RESULTS

At 8 weeks, VO2  peak improved more with HIIT (2.37 mL.kg-1.min-1; SD, 3.11) compared with MISS (1.32 mL.kg-1.min-1; SD, 2.66). After adjusting for age, sex and study site, the difference between arms was 1.04 mL.kg-1.min-1 (95% CI, 0.38 to 1.69; p = 0.002). Only 1 serious adverse event was possibly related to HIIT.

CONCLUSIONS

In stable CAD, low-volume HIIT improved cardiorespiratory fitness more than MISS by a clinically meaningful margin. Low-volume HIIT is a safe, well tolerated, and clinically effective intervention that produces short-term improvement in cardiorespiratory fitness. It should be considered by all CR programmes as an adjunct or alternative to MISS.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02784873. https://clinicaltrials.gov/ct2/show/NCT02784873.

Implementation of weekday time-restricted eating to improve metabolic health in breast cancer survivors with overweight/obesity

OBJECTIVE

This study aimed to evaluate the implementation of telephone-based delivery of weekday-only time-restricted eating (TRE), its preliminary efficacy for metabolic outcomes, and concurrent lifestyle changes.

METHODS

Twenty-two breast cancer survivors aged 60+ years with overweight/obesity completed an 8-week feasibility study of 12 to 8 p.m. weekday-only ad libitum TRE. The intervention was delivered by one registered dietitian call, twice-daily automated text messages asking about eating start and stop times, and three support phone calls. Magnetic resonance imaging, venipuncture, and 3 days of diet records and accelerometry were performed at baseline and after intervention.

RESULTS

Participants had a mean age of 66 (SD 5) years with BMI of 31.8 (4.8) kg/m² . Intervention implementation was successful, including excellent adherence (98%), participant acceptability, and a low symptom profile and cost ($63/participant). There were no significant changes in individual components of metabolic syndrome, lipid profile, or hemoglobin A_1c , despite clinically relevant changes occurring within individual participants. Magnetic resonance imaging-derived hepatic steatosis and thigh myosteatosis did not change. Dietary intake changes included reduced energy (-22%) and protein (-0.2 g/kg). Physical activity and sleep did not change.

CONCLUSIONS

Eight weeks of telephone-delivered weekday TRE is a feasible, acceptable, low-symptom, and low-cost intervention. Future studies may consider a longer intervention length for more consistent metabolic improvements and counseling to enhance protein intake.

Cardiac mechanisms for low aerobic power in anthracycline treated, older, long-term breast cancer survivors

Breast cancer survivors have reduced peak aerobic capacity (VO_2peak) which may be related to latent or lingering chemotherapy induced cardiac damage. Nine, older (67 ± 3 years), long-term survivors (9.8 years) of anthracycline based chemotherapy and age- and sex-matched healthy controls were recruited and tested to determine whether: i) VO_2peak remains reduced in long-term survivorship; and ii) reductions in VO_2peak are due to cardiac dysfunction. VO_2peak was significantly reduced in breast cancer survivors relative to healthy controls (15.9 ± 2.0 vs 19.9 ± 3.1 ml/kg/min, p = 0.006), however the heart rate and stroke volume responses to exercise were normal (heart rate reserve; 88 ± 9 vs 85 ± 10 bpm, p = 0.62: stroke volume reserve; 13 ± 6 vs 13 ± 9 ml,p = 0.94). These findings indicate low-normal ventricular size in long-term breast cancer survivors, but normal reserve function.

Associations between training characteristics and change in peak oxygen consumption following exercise training in patients with heart failure with preserved ejection fraction

Introduction

In heart failure with preserved ejection fraction (HFpEF), moderate continuous training (MCT) and high-intensity interval training (HIIT) are both effective in increasing peak oxygen uptake (peak V̇O2).

Purpose

The aim of this study was to investigate the association of training characteristics (i.e. average sessions/week, average duration/week, mean intensity) and change in peak V̇O2 following 3 months of MCT and HIIT in patients with HFpEF.

Methods

Among 120 patients who were randomized to MCT (5x40 min/week at 35–50% heart rate reserve [HRR]) or HIIT (3x38 min/week at 80–90% HRR), those who completed 3-month follow-up (N=107) were considered for this analysis. Training duration and heart rates [HR] were recorded with a smartphone application, evaluated with a customized software and manually checked for plausibility. If HR measurements were classified as invalid/unreliable (e.g. very strong fluctuations), patients were excluded from analysis. Intensities were calculated as average % HRR of total sessions in MCT and the average of the highest % HRR values of all intervals in HIIT. Associations between training characteristics and change in peak V̇O2 were evaluated using univariate and multivariate regression analyses. Individual HR-V̇O2 relationships were used to calculate and compare energy expenditure (MET-minutes) in MCT and HIIT.

Results

After excluding 16 patients due to invalid/unreliable HR data, 91 patients (67% female, 69±7 years) were included in this analysis. On average, MCT patients (N=45) performed 4.0±1.2 sessions/week (162±52 min/week) at 47.4±6.7% HRR, while HIIT patients (N=46) performed 2.4±0.8 sessions/week (96±40 min/week) at 81.8±11.8% HRR. Peak V̇O2 was improved by 1.70±2.35 ml/kg/min in MCT and 1.46±2.98 ml/kg/min in HIIT (difference: 0.24 [95% CI, −0.87 to 1.34], p=0.67). The associations between training characteristics and change in peak V̇O2 are shown in Fig.1. Mean % HRR was not significantly associated with the change in peak V̇O2 in the HIIT group, whereas in MCT, mean duration/week and mean intensity were of similar relative importance (standardized coefficients) and explained up to 26% of the variation in change in peak V̇O2 (Table 1). Average weekly MET-minutes above rest were 451±260 for MCT and 389±375 for HIIT (difference: 62 [95% CI, −71 to 195], p=0.36). After adjustment for MET-minutes, the difference in change in peak V̇O2 between groups diminished to 0.09 ml/kg/min (95% CI, −0.97 to 1.16; p=0.98).

Conclusions

Weekly duration and mean % HRR had a similar predictive ability for the change in peak V̇O2 following MCT with, interestingly, lower change in peak V̇O2 with increasing intensity. In HIIT, mean % HRR was not significantly associated with the change in peak V̇O2. After adjusting for energy expenditure, the difference in change in peak V̇O2 between training modes diminished, suggesting that MCT and HIIT were similarly effective.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Commission, Framework Program 7

Pericardial fat is adversely related to cardio-mechanical interaction in heart failure with preserved ejection fraction: implications for exercise intolerance

Background

Exercise intolerance is the primary manifestation in heart failure with preserved ejection fraction (HFpEF); however, the pathophysiologic mechanism(s) remains incompletely understood. Excess cardiac adiposity may physically constrain the myocardium, resulting in adverse Cardio-Mechanical Interaction (i.e., greater left ventricular eccentricity); a phenomenon only expected to worsen during exercise, with increased respiratory excursion and hemodynamic load. Evidence for this hypothesis, however, remains limited to a small number of observations, from a single group, made only under resting conditions using transthoracic echocardiography.

Purpose

To evaluate the relationship between pericardial fat and cardio-mechanical interaction in HFpEF at rest and during exercise using high resolution cardiac magnetic resonance imaging (cMRI).

Methods

We performed real-time (ungated), free-breathing cinematic imaging of the left ventricular (LV) short axis in 11 individuals with HFpEF (4M/7F, BMI: 36±6, age: 69±4 years). Imaging was performed at rest and during dynamic leg exercise (30 Watts) using an MRI-compatible ergometer (Ergospect, Austria). Epicardial and paracardial fat area were measured using high resolution cine images in the horizontal long axis imaging plane, with epicardial fat defined as the adipose tissue within the pericardium and paracardial fat defined as the adipose tissue outside of the pericardium (Figure 1A); the sum of which defined pericardial fat area. The LV eccentricity index was calculated as the ratio of LV short axis diameter parallel to the septum (anteroposterior dimension, AP) to the LV short axis diameter perpendicular to the septum (septolateral dimension, SL, Figure 1A) at mid-ventricular level, during inspiration at end-diastole.

Results

At rest, adverse cardio-mechanical interaction (i.e., AP/SL &gt;1.0) was observed in 5 of the 11 cases. In those with adverse cardio-mechanical interaction both epicardial and paracardial fat area were significantly higher, resulting in greater pericardial fat area (Figure 1B). While epicardial fat area was not related to LV eccentricity index (R2=0.19, P=0.18), we observed a strong correlation between paracardial fat area and LV eccentricity index (R2=0.93, P&lt;0.01), and pericardial fat area and LV eccentricity index (R2=0.86, P&lt;0.01, Figure 1C). In contrast to our hypothesis, however, supine exercise did not exacerbate cardio-mechanical interaction, with LV eccentricity index remaining elevated in 4 of the 5 original cases, improving the fifth case (1.1 to 0.9, rest to exercise).

Conclusions

Taken together, these data extend prior reports of adverse cardio-mechanical interaction in HFpEF, showing greater contribution from paracardial fat versus epicardial fat. Future studies are needed to examine cardio-mechanical interaction during upright exercise in HFpEF patients.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): National Institutes of Health

Prescribing Exercise in Early-Stage Breast Cancer During Chemotherapy: A Simple Periodized Approach to Align With the Cyclic Phases of Chemotherapy

ABSTRACT

Bigaran, A, Howden, EJ, Foulkes, S, Janssens, K, Beaudry, R, Haykowsky, MJ, La Gerche, A, Fraser, SF, and Selig, SE. Prescribing exercise in early-stage breast cancer during chemotherapy: a simple periodized approach to align with the cyclic phases of chemotherapy. J Strength Cond Res 36(10): 2934-2941, 2022-To evaluate whether a periodized aerobic and resistance training plan aligned to the anthracycline chemotherapy (AC) cycles would be well tolerated, feasible, and attenuate the decline in peak oxygen uptake (V̇o2peak) in breast cancer (BC) patients. Twenty-eight women with early-stage BC treated with AC self-selected to undertake exercise training (EX 47 ± 9 years, n = 14) or usual care (53 ± 9 years, n = 14) for 12 weeks as part of a nonrandomized controlled trial. The periodized EX was aligned to the cyclic phases of AC, including AC taper and nontaper weeks. Outcome measures included cardiopulmonary exercise testing. Attendance and adherence variables (relative dose intensity [RDI] and volume load) were calculated to quantify the dose of EX completed relative to the amount of EX prescribed. The mean session attendance was 76% (range 46-88%). The mean ± SD prescribed and completed dose of aerobic training was 332.3 ± 48.7 MET h·wk-1 and 380.6 ± 53.2 MET h·wk-1 (p = 0.02), equating to a mean RDI of 89 ± 17%. For resistance training, the prescribed and completed cumulative dose was 128,264 ± 54,578 and 77,487 ± 26,108 kg (p < 0.001), equating to an RDI of 60 ± 11%. Adherence to the AC taper week RDI (52 ± 14%) for resistance training was significantly lower than the non-AC taper week (72 ± 8%, p = 0.02). The most frequent cause for EX interruption was hospitalization (35%), whereas AC-related illness was the most common cause for missed (57%) or modified EX sessions (64%). This periodized approach was mostly well tolerated for patients with BC. We speculate that a periodized approach may be both more palatable and useful, although this requires further investigation in a randomized controlled trial.

Heart Failure With Preserved Ejection Fraction as an Exercise Deficiency Syndrome: JACC Focus Seminar 2/4

Across differing spectrums of cardiac function and cardiac pathologies, there are strong associations between measures of cardiorespiratory fitness and burden of symptoms, quality of life, and prognosis. In this part 2 of a 4-part series, we contend that there is a strong association among physical activity, cardiorespiratory fitness, and cardiac function. We argue that a chronic lack of exercise is a major risk factor for heart failure with preserved ejection fraction in some patients. In support of this hypothesis, increasing physical activity is associated with greater cardiac mass, greater stroke volumes, greater cardiac output and peak oxygen consumption, and fewer clinical events. Conversely, physical inactivity results in cardiac atrophy, reduced output, reduced chamber size, and decreased ability to augment cardiac performance with exercise. Moreover, physical inactivity is a strong predictor of heart failure risk and death. In sum, exercise deficiency should be considered part of the broad heart failure with preserved ejection fraction phenotype.

Exercise for Primary and Secondary Prevention of Cardiovascular Disease: JACC Focus Seminar 1/4

Regular exercise that meets or exceeds the current physical activity guidelines is associated with a reduced risk of cardiovascular disease (CVD) and mortality. Therefore, exercise training plays an important role in primary and secondary prevention of CVD. In this part 1 of a 4-part focus seminar series, we highlight the mechanisms and physiological adaptations responsible for the cardioprotective effects of exercise. This includes an increase in cardiorespiratory fitness secondary to cardiac, vascular, and skeletal muscle adaptations and an improvement in traditional and nontraditional CVD risk factors by exercise training. This extends to the role of exercise and its prescription in patients with CVDs (eg, coronary artery disease, chronic heart failure, peripheral artery disease, or atrial fibrillation) with special focus on the optimal mode, dosage, duration, and intensity of exercise to reduce CVD risk and improve clinical outcomes in these patients.

Peak O2 -pulse predicts exercise training-induced changes in peak V̇O2 in heart failure with preserved ejection fraction

AIMS

Exercise training (ET) has been consistently shown to increase peak oxygen consumption (V̇O₂ ) in patients with heart failure with preserved ejection fraction (HFpEF); however, inter-individual responses vary significantly. Because it is unlikely that ET-induced improvements in peak V̇O₂ are significantly mediated by an increase in peak heart rate (HR), we aimed to investigate whether baseline peak O₂ -pulse (V̇O₂  × HR^-1 , reflecting the product of stroke volume and arteriovenous oxygen difference), not baseline peak V̇O₂ , is inversely associated with the change in peak V̇O₂ (adjusted by body weight) following ET versus guideline control (CON) in patients with HFpEF.

METHODS AND RESULTS

This was a secondary analysis of the OptimEx-Clin (Optimizing Exercise Training in Prevention and Treatment of Diastolic Heart Failure, NCT02078947) trial, including all 158 patients with complete baseline and 3 month cardiopulmonary exercise testing measurements (106 ET, 52 CON). Change in peak V̇O₂ (%) was analysed as a function of baseline peak V̇O₂ and its determinants (absolute peak V̇O₂ , peak O₂ -pulse, peak HR, weight, haemoglobin) using robust linear regression analyses. Mediating effects on change in peak V̇O₂ through changes in peak O₂ -pulse, peak HR and weight were analysed by a causal mediation analysis with multiple correlated mediators. Change in submaximal exercise tolerance (V̇O₂ at the ventilatory threshold, VT1) was analysed as a secondary endpoint. Among 158 patients with HFpEF (66% female; mean age, 70 ± 8 years), changes in peak O₂ -pulse explained approximately 72% of the difference in changes in peak V̇O₂ between ET and CON [10.0% (95% CI, 4.1 to 15.9), P = 0.001]. There was a significant interaction between the groups for the influence of baseline peak O₂ -pulse on change in peak V̇O₂ (interaction P = 0.04). In the ET group, every 1 mL/beat higher baseline peak O₂ -pulse was associated with a decreased mean change in peak V̇O₂ of -1.45% (95% CI, -2.30 to -0.60, P = 0.001) compared with a mean change of -0.08% (95% CI, -1.11 to 0.96, P = 0.88) following CON. None of the other factors showed significant interactions with study groups for the change in peak V̇O₂ (P > 0.05). Change in V̇O₂ at VT1 was not associated with any of the investigated factors (P > 0.05).

CONCLUSIONS

In patients with HFpEF, the easily measurable peak O₂ -pulse seems to be a good indicator of the potential for improving peak V̇O₂ through exercise training. While changes in submaximal exercise tolerance were independent of baseline peak O₂ -pulse, patients with high O₂ -pulse may need to use additional therapies to significantly increase peak V̇O₂ .

A Contemporary Review of the Effects of Exercise Training on Cardiac Structure and Function and Cardiovascular Risk Profile: Insights From Imaging

Exercise is a commonly prescribed therapy for patients with established cardiovascular disease or those at high risk for de novo disease. Exercise-based, multidisciplinary programs have been associated with improved clinical outcomes post myocardial infarction and is now recommended for patients with cancer at elevated risk for cardiovascular complications. Imaging studies have documented numerous beneficial effects of exercise on cardiac structure and function, vascular function and more recently on the cardiovascular risk profile. In this contemporary review, we will discuss the effects of exercise training on imaging-derived cardiovascular outcomes. For cardiac imaging via echocardiography or magnetic resonance, we will review the effects of exercise on left ventricular function and remodeling in patients with established or at risk for cardiac disease (myocardial infarction, heart failure, cancer survivors), and the potential utility of exercise stress to assess cardiac reserve. Exercise training also has salient effects on vascular function and health including the attenuation of age-associated arterial stiffness and thickening as assessed by Doppler ultrasound. Finally, we will review recent data on the relationship between exercise training and regional adipose tissue deposition, an emerging marker of cardiovascular risk. Imaging provides comprehensive and accurate quantification of cardiac, vascular and cardiometabolic health, and may allow refinement of risk stratification in select patient populations. Future studies are needed to evaluate the clinical utility of novel imaging metrics following exercise training.

Left Atrial Stiffness Index Independently Predicts Exercise Intolerance and Quality of Life in Older, Obese Patients With Heart Failure With Preserved Ejection Fraction

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is the fastest growing form of HF and is associated with high morbidity and mortality. The primary chronic symptom in HFpEF is exercise intolerance, associated with reduced quality of life. Emerging evidence implicates left atrial (LA) dysfunction as an important pathophysiologic mechanism. Here we extend prior observations by relating LA dysfunction to peak oxygen uptake (peak VO₂), physical function (distance walked in 6 minutes [6MWD]) and quality of life (Kansas City Cardiomyopathy Questionnaire).

METHODS AND RESULTS

We compared 75 older, obese, patients with HFpEF with 53 healthy age-matched controls. LA strain was assessed by magnetic resonance cine imaging using feature tracking. LA function was defined according to its 3 distinct phases, with the LA serving as a reservoir during systole, as a conduit during early diastole, and as a booster pump at the end of diastole. The LA stiffness index was calculated as the ratio of early mitral inflow velocity-to-early annular tissue velocity (E/e', by Doppler ultrasound examination) and LA reservoir strain. HFpEF had a decreased reservoir strain (16.4 ± 4.4% vs 18.2 ± 3.5%, P = .018), lower conduit strain (7.7 ± 3.3% vs 9.1 ± 3.4%, P = .028), and increased stiffness index (0.86 ± 0.39 vs 0.53 ± 0.18, P < .001), as well as decreased peak VO₂, 6MWD, and lower quality of life. Increased LA stiffness was independently associated with impaired peak VO₂ (β = 9.0 ± 1.6, P < .001), 6MWD (β = 117 ± 22, P = .003), and Kansas City Cardiomyopathy Questionnaire score (β = -23 ± 5, P = .001), even after adjusting for clinical covariates.

CONCLUSIONS

LA stiffness is independently associated with impaired exercise tolerance and quality of life and may be an important therapeutic target in obese HFpEF.

REGISTRATION

NCT00959660.

Rethinking Rehabilitation: A REVIEW OF PATIENT POPULATIONS WHO CAN BENEFIT FROM CARDIAC REHABILITATION

Although cardiac rehabilitation (CR) is safe and highly effective for individuals with various cardiovascular health conditions, to date there are only seven diagnoses or procedures identified by the Centers for Medicare & Medicaid Services that qualify for referral. When considering the growing number of individuals with cardiovascular disease (CVD), or other health conditions that increase the risk for CVD, it is important to determine the extent for which CR could benefit these populations. Furthermore, there are some patients who may currently be eligible for CR (spontaneous coronary artery dissection, left ventricular assistant device) but make up a relatively small proportion of the populations that are regularly attending and participating. Thus, these patient populations and special considerations for exercise might be less familiar to professionals who are supervising their programs. The purpose of this review is to summarize the current literature surrounding exercise testing and programming among four specific patient populations that either do not currently qualify for (chronic and end-stage renal disease, breast cancer survivor) or who are eligible but less commonly seen in CR (sudden coronary artery dissection, left ventricular assist device). While current evidence suggests that individuals with these health conditions can safely participate in and may benefit from supervised exercise programming, there is an immediate need for high-quality, multisite clinical trials to develop more specific exercise recommendations and support the inclusion of these populations in future CR programs.

Cardiac remodelling predicts outcome in patients with chronic heart failure

Aims

Surveillance imaging is often used to detect remodelling, a change in cardiac geometry, and/or function; however, there are limited data in patients with chronic heart failure (HF). We sought to characterize cardiac remodelling in patients with chronic HF and evaluate its association with outcome.

Methods and results

A prospective cohort of patients at risk for HF or with chronic HF underwent cardiac magnetic resonance (CMR) at baseline and 1 year. Ventricular function, volumes, mass, left atrial volume, global longitudinal strain, and myocardial scar were measured. The primary outcome was a composite of death or cardiovascular hospitalization up to 5 years from the 1 year scan. Cox regression was used to identify 1 year CMR predictors of outcome after adjusting for baseline risk. A total of 262 patients (median age 68 years, 57% males) including 96 at risk for HF, 97 with HF and preserved ejection fraction, and 69 with HF and reduced ejection fraction were included. In the patients with HF, 55 events were identified during follow‐up. After adjustment for baseline clinical risk, Cox proportion hazard regressions only identified 1 year change in left ventricular (LV) mass index as a CMR predictor of outcome, adjusted hazard ratio 1.21 (1.02, 1.44) per 10% increase, P = 0.031. Cardiac remodelling defined as a 1 year change in LV mass index ≥15% was observed in 35% of patients with HF. Patients with adverse remodelling of LV mass index had more events on Kaplan–Meier analyses compared to those with no remodelling, log‐rank P = 0.004 for overall cohort, P = 0.035 for heart failure with preserved ejection fraction and P = 0.035 for heart failure and reduced ejection fraction.

Conclusions

Cardiac remodelling is common during serial CMR assessment of patients with chronic HF. Change in LV mass predicted long‐term outcomes whereas change in left ventricular ejection fraction did not.

Exercise Intolerance in Older Adults With Heart Failure With Preserved Ejection Fraction: JACC State-of-the-Art Review

Exercise intolerance (EI) is the primary manifestation of chronic heart failure with preserved ejection fraction (HFpEF), the most common form of heart failure among older individuals. The recent recognition that HFpEF is likely a systemic, multiorgan disorder that shares characteristics with other common, difficult-to-treat, aging-related disorders suggests that novel insights may be gained from combining knowledge and concepts from aging and cardiovascular disease disciplines. This state-of-the-art review is based on the outcomes of a National Institute of Aging-sponsored working group meeting on aging and EI in HFpEF. We discuss aging-related and extracardiac contributors to EI in HFpEF and provide the rationale for a transdisciplinary, "gero-centric" approach to advance our understanding of EI in HFpEF and identify promising new therapeutic targets. We also provide a framework for prioritizing future research, including developing a uniform, comprehensive approach to phenotypic characterization of HFpEF, elucidating key geroscience targets for treatment, and conducting proof-of-concept trials to modify these targets.

Pathophysiology of Exercise Intolerance and Its Treatment With Exercise-Based Cardiac Rehabilitation in Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is the fastest growing form of heart failure in the United States. The cardinal feature of HFpEF is reduced exercise tolerance (peak oxygen uptake, (Equation is included in full-text article.)O2peak) secondary to impaired cardiac, vascular, and skeletal muscle function. There are currently no evidence-based drug therapies to improve clinical outcomes in patients with HFpEF. In contrast, exercise training is a proven effective intervention for improving (Equation is included in full-text article.)O2peak, aerobic endurance, and quality of life in HFpEF patients. This brief review discusses the pathophysiology of exercise intolerance and the role of exercise training to improve (Equation is included in full-text article.)O2peak in clinically stable HFpEF patients. It also discusses the mechanisms responsible for the exercise training-mediated improvements in (Equation is included in full-text article.)O2peak in HFpEF. Finally, it provides evidence-based exercise prescription guidelines for cardiac rehabilitation specialists to assist them with safely implementing exercise-based cardiac rehabilitation programs for HFpEF patients.

Cardiac and Cardiometabolic Phenotyping of Trastuzumab-Mediated Cardiotoxicity: a Secondary Analysis of the MANTICORE trial

AIMS

An improved understanding of the pathophysiology of trastuzumab-mediated cardiotoxicity is required to improve outcomes of patients with HER2-positive breast cancer. We aimed to characterize the cardiac and cardiometabolic phenotype of trastuzumab-mediated toxicity and potential interactions with cardiac pharmacotherapy.

METHODS AND RESULTS

This study was an analysis of serial magnetic resonance imaging (MRI) and circulating biomarker data acquired from patients with HER2-positive early stage breast cancer participating in a randomized-controlled clinical trial for the pharmaco-prevention of trastuzumab-associated cardiotoxicity. Circulating biomarkers (B-type natriuretic peptide, troponin I, MMP-2 and -9, GDF-15, neuregulin-1 and IGF-1) and MRI of cardiac structure and function and abdominal fat distribution were acquired prior to trastuzumab, post-cycle 4 and post-cycle 17. Ninety-four participants (51±8 years) completed the study with 30 on placebo, 33 on perindopril, and 31 on bisoprolol. Post-cycle 4, global longitudinal strain (GLS) deteriorated from baseline in both placebo (+2.0±2.7%, p = 0.002) and perindopril (+0.9±2.5%, p = 0.04), but not with bisoprolol (-0.2±2.1%, p = 0.55). In all groups combined, extracellular volume fraction and GDF-15 increased post-cycle 4 (+1.3±4.4%, p = 0.004; +130±150%, p ≤ 0.001, respectively). However, no significant change in troponin I was detected throughout trastuzumab. In all groups combined, visceral and intermuscular fat volume increased post-cycle 4 (+7±17%, p = 0.02, +8±23%, p = 0.02, respectively), while muscle volume and IGF-1 decreased from post-cycle 4 to 17 (-2±10%, p = 0.008, -18±28%, p < 0.001, respectively).

CONCLUSION

Trastuzumab results in impaired cardiac function and early myocardial inflammation. Trastuzumab is also associated with deleterious changes to the cardiometabolic phenotype which may contribute to the increased cardiovascular risk in this population.

Left ventricular diastolic dysfunction and exercise intolerance in obese heart failure with preserved ejection fraction

This study tested the hypothesis that early left ventricular (LV) relaxation is impaired in older obese patients with heart failure with preserved ejection fraction (HFpEF), and related to decreased peak exercise oxygen uptake (peak V̇o₂). LV strain and strain rate were measured by feature tracking of magnetic resonance cine images in 79 older obese patients with HFpEF (mean age: 66 yr; mean body mass index: 38 kg/m²) and 54 healthy control participants. LV diastolic strain rates were indexed to cardiac preload as estimated by echocardiography derived diastolic filling pressures (E/e'), and correlated to peak V̇o₂. LV circumferential early diastolic strain rate was impaired in HFpEF compared with controls (0.93 ± 0.05/s vs. 1.20 ± 0.07/s, P = 0.014); however, we observed no group differences in early LV radial or longitudinal diastolic strain rates. Isolating myocardial relaxation by indexing all three early LV diastolic strain rates (i.e. circumferential, radial, and longitudinal) to E/e' amplified the group difference in early LV diastolic circumferential strain rate (0.08 ± 0.03 vs. 0.13 ± 0.05, P < 0.0001), and unmasked differences in early radial and longitudinal diastolic strain rate. Moreover, when indexing to E/e', early LV diastolic strain rates from all three principal strains, were modestly related with peak V̇o₂ (R = 0.36, -0.27, and 0.35, respectively, all P < 0.01); this response, however, was almost entirely driven by E/e' itself, (R = -0.52, P < 0.001). Taken together, we found that although LV relaxation is impaired in older obese patients with HFpEF, and modestly correlates with their severely reduced peak exercise V̇o₂, LV filling pressures appear to play a much more important role in determining exercise intolerance.NEW & NOTEWORTHY Using a multimodal imaging approach to uncouple tissue deformation from atrial pressure, we found that left ventricular (LV) relaxation is impaired in older obese patients with HFpEF, but only modestly correlates with their severely reduced peak V̇o₂. In contrast, the data show a much stronger relationship between elevated LV filling pressures and exercise intolerance, refocusing future therapeutic priorities.

Effect of High-Intensity Interval Training, Moderate Continuous Training, or Guideline-Based Physical Activity Advice on Peak Oxygen Consumption in Patients With Heart Failure With Preserved Ejection Fraction: A Randomized Clinical Trial

IMPORTANCE

Endurance exercise is effective in improving peak oxygen consumption (peak V̇o2) in patients with heart failure with preserved ejection fraction (HFpEF). However, it remains unknown whether differing modes of exercise have different effects.

OBJECTIVE

To determine whether high-intensity interval training, moderate continuous training, and guideline-based advice on physical activity have different effects on change in peak V̇o2 in patients with HFpEF.

DESIGN, SETTING, AND PARTICIPANTS

Randomized clinical trial at 5 sites (Berlin, Leipzig, and Munich, Germany; Antwerp, Belgium; and Trondheim, Norway) from July 2014 to September 2018. From 532 screened patients, 180 sedentary patients with chronic, stable HFpEF were enrolled. Outcomes were analyzed by core laboratories blinded to treatment groups; however, the patients and staff conducting the evaluations were not blinded.

INTERVENTIONS

Patients were randomly assigned (1:1:1; n = 60 per group) to high-intensity interval training (3 × 38 minutes/week), moderate continuous training (5 × 40 minutes/week), or guideline control (1-time advice on physical activity according to guidelines) for 12 months (3 months in clinic followed by 9 months telemedically supervised home-based exercise).

MAIN OUTCOMES AND MEASURES

Primary end point was change in peak V̇o2 after 3 months, with the minimal clinically important difference set at 2.5 mL/kg/min. Secondary end points included changes in metrics of cardiorespiratory fitness, diastolic function, and natriuretic peptides after 3 and 12 months.

RESULTS

Among 180 patients who were randomized (mean age, 70 years; 120 women [67%]), 166 (92%) and 154 (86%) completed evaluation at 3 and 12 months, respectively. Change in peak V̇o2 over 3 months for high-intensity interval training vs guideline control was 1.1 vs -0.6 mL/kg/min (difference, 1.5 [95% CI, 0.4 to 2.7]); for moderate continuous training vs guideline control, 1.6 vs -0.6 mL/kg/min (difference, 2.0 [95% CI, 0.9 to 3.1]); and for high-intensity interval training vs moderate continuous training, 1.1 vs 1.6 mL/kg/min (difference, -0.4 [95% CI, -1.4 to 0.6]). No comparisons were statistically significant after 12 months. There were no significant changes in diastolic function or natriuretic peptides. Acute coronary syndrome was recorded in 4 high-intensity interval training patients (7%), 3 moderate continuous training patients (5%), and 5 guideline control patients (8%).

CONCLUSIONS AND RELEVANCE

Among patients with HFpEF, there was no statistically significant difference in change in peak V̇o2 at 3 months between those assigned to high-intensity interval vs moderate continuous training, and neither group met the prespecified minimal clinically important difference compared with the guideline control. These findings do not support either high-intensity interval training or moderate continuous training compared with guideline-based physical activity for patients with HFpEF.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02078947.

Reliability and reproducibility of cardiac MRI quantification of peak exercise function with long-axis views

The conventional approach to cardiac magnetic resonance (CMR) involving breath holds, electrocardiography-gating, and acquisition of a short-axis (SAX) image stack, introduces technical and logistical challenges for assessing exercise left ventricular (LV) function. Real-time, free-breathing CMR acquisition of long-axis (LAX) images overcomes these issues and also enables assessment of global longitudinal strain (GLS). We evaluated the reliability of a free-breathing LAX approach compared to the standard SAX approach and the reproducibility of free-breathing LAX. LV SAX (contiguous stack) and LAX (two-chamber and four-chamber) 3T CMR cine images were acquired four times within one scan in 32 women with cardiovascular risk factors (56±10 years, 28±4 kg/m2) as follows: 1) resting, gated-segmented, end-expiration breath-hold; 2) resting, real-time, free-breathing; 3) test-retest set of resting, real-time, free-breathing; 4) peak exercise (incremental-to-maximum, in-magnet, stepper test), real-time, free-breathing. A second scan was performed within one week in a subset (n = 5) to determine reproducibility of peak exercise measures. Reliability and agreement of the free-breathing LAX approach with the conventional SAX approach were assessed by intraclass correlation coefficient (ICC) and Bland-Altman plots, respectively. Normal control GLS reserve was also acquired in a separate set of 12 young, healthy control women (25±4 years, 22±2 kg/m2) for comparison. Comparisons of LV volumes and function among all techniques at rest had good-to-excellent reliability (ICC = 0.80-0.96), and excellent reliability between peak exercise free-breathing LAX and SAX evaluations (ICC = 0.92-0.96). Higher resting heart rates with free-breathing acquisitions compared to breath-hold (mean difference, limits of agreement: 5, 1-12 beats per minute) reduced reliability for cardiac output (ICC = 0.67-0.79). Reproducibility of the free-breathing LAX approach was good-to-excellent at rest and peak exercise (ICC = 0.74-0.99). GLS exercise reserve was impaired in older women at cardiovascular risk compared to young healthy women (-4.7±2.3% vs -7.4±2.1%, p = 0.001). Real-time, free-breathing CMR with LAX evaluation provides a reliable and reproducible method to assess rest and peak exercise cardiac function, including GLS.

Aerobic Fitness Is Related to Myocardial Fibrosis Post-Anthracycline Therapy

PURPOSE

We evaluated the impact of anthracyclines on left ventricular function and myocardial tissue characteristics using cardiovascular magnetic resonance (CMR) imaging to determine their relationship with V˙O2peak.

METHODS

Women with breast cancer who had not yet received treatment (No-AT, n = 16) and had received anthracycline treatment ~1 yr earlier (Post-AT, n = 16) and controls without cancer (CON, n = 16) performed a maximal exercise test and a comprehensive 3T CMR examination, including native myocardial T1 mapping, where elevated T1 times are indicative of myocardial fibrosis. ANOVA and linear regression were used to compare CMR variables between groups and to determine associations with V˙O2peak. Subgroup analysis was performed by categorizing participants as "fit" or "unfit" based on whether their V˙O2peak value was greater or less than 100% of reference value for age, respectively.

RESULTS

Left ventricular end-diastolic volume, ejection fraction, and mass were similar between groups. Post-AT, T1 times were elevated (1534 ± 32 vs 1503 ± 28 ms, P < 0.01), and V˙O2peak was reduced (23.1 ± 7.5 vs 29.5 ± 7.7 mL·kg-1⋅min-1, P = 0.02) compared with CON. In No-AT, T1 times and V˙O2peak were similar to CON. In the Post-AT group, T1 time was associated with V˙O2peak (R2 = 64%), whereas in the absence of anthracyclines (i.e., No-AT and CON groups), T1 time was not associated with V˙O2peak. Regardless of group, all fit women had similar T1 times, whereas unfit women Post-AT had higher T1 than unfit CON (1546 ± 22 vs 1500 ± 33 ms, P < 0.01).

CONCLUSIONS

After anthracycline chemotherapy, an elevated T1 time suggesting greater extent of myocardial fibrosis, was associated with lower V˙O2peak. However, those who were fit did not have evidence of myocardial fibrosis after anthracycline treatment.

Impact of severe obesity on exercise performance in heart failure with preserved ejection fraction

BACKGROUND

Obesity plays an important role in functional impairment in HFpEF. The mechanisms underlying decreased functional capacity in obese HFpEF are not clear. We assessed the cardiac and peripheral determinants of exercise performance in HFpEF patients with class 2 obesity in the upright position, representative of posture when performing functional activities.

METHODS AND RESULTS

Thirty-two HFpEF patients were divided into two groups by presence of class 2 obesity (C2, BMI ≥ 35 kg/m2 , n = 14) and non-C2 (BMI < 35 kg/m2 , n = 18). Participants performed a bout of submaximal exercise followed by incremental stages of treadmill exercise to determine peak aerobic power (peak VO2 ). Peak VO2 and Ve/VCO2 were measured using Douglas bags while cardiac output (Qc) and stroke volume (SV) were measured by acetylene rebreathing. The C2 group were younger than the non-C2 group (67 ± 6 versus 73 ± 6 years; p = .009). Comorbid condition burden was similar between groups. Peak VO2 indexed to body mass was not significantly different between groups. Absolute peak VO2 was higher in the C2 group secondary to a larger peak Qc (14.3 versus 11.0 L/min; p = .012). SV reserve was also higher in the C2 group (72 versus 49%; p = .038).

CONCLUSION

HFpEF patients with severe obesity had similar cardiorespiratory fitness compared to patients with lower BMI with similar comorbidity burden. Absolute VO2 was actually higher in the severely obese driven by larger Qc and SV reserve arguing against significant effects from obesity per se on aerobic performance. The presence of a larger "cardiac engine" may offer potential for fat-loss strategies to improve impairments in functional capacity in obese patients with HFpEF.

Determinants of Cardiorespiratory Fitness After Bariatric Surgery: Insights From a Randomised Controlled Trial of a Supervised Training Program

BACKGROUND

Severely obese patients have decreased cardiorespiratory fitness (CRF) and poor functional capacity. Bariatric surgery-induced weight loss improves CRF, but the determinants of this improvement are not well known. We aimed to assess the determinants of CRF before and after bariatric surgery and the impact of an exercise training program on CRF after bariatric surgery.

METHODS

Fifty-eight severely obese patients (46.1 ± 6.1 kg/m², 78% women) were randomly assigned to either an exercise group (n = 39) or usual care (n = 19). Exercise training was conducted from the 3rd to the 6th months after surgery. Anthropometric measurements, abdominal and mid-thigh computed tomographic scans, resting echocardiography, and maximal cardiopulmonary exercise testing was performed before bariatric surgery and 3 and 6 months after surgery.

RESULTS

Weight, fat mass, and fat-free mass were reduced significantly at 3 and 6 months, without any additive impact of exercise training in the exercise group. From 3 to 6 months, peak aerobic power (V̇O_2peak) increased significantly (P < 0.0001) in both groups but more importantly in the exercise group (exercise group: from 18.6 ± 4.2 to 23.2 ± 5.7 mL/kg/min; control group: from 17.4 ± 2.3 to 19.7 ± 2.4 mL/kg/min; P value, group × time = 0.01). In the exercise group, determinants of absolute V̇O_2peak (L/min) were peak exercise ventilation, oxygen pulse, and heart rate reserve (r² = 0.92; P < 0.0001), whereas determinants of V̇O_2peak indexed to body mass (mL/kg/min) were peak exercise ventilation and early-to-late filling velocity ratio (r² = 0.70; P < 0.0001).

CONCLUSIONS

A 12-week supervised training program has an additive benefit on cardiorespiratory fitness for patients who undergo bariatric surgery.

Exercise as a diagnostic and therapeutic tool for preventing cardiovascular morbidity in breast cancer patients- the BReast cancer EXercise InTervention (BREXIT) trial protocol

BACKGROUND

Anthracycline chemotherapy (AC) is an efficacious (neo) adjuvant treatment for early-stage breast cancer (BCa), but is associated with an increased risk of cardiac dysfunction and functional disability. Observations suggest that regular exercise may be a useful therapy for the prevention of cardiovascular morbidity but it is yet to be interrogated in a large randomised trial. The primary aims of this study are to: 1) determine if 12-months of ET commenced at the onset of AC can reduce the proportion of BCa patients with functional disability (peak VO2, < 18 ml/kg/min), and 2) compare current standard-of-care for detecting cardiac dysfunction (resting left-ventricular ejection fraction assessed from 3-dimensional echocardiography) to measures of cardiac reserve (peak exercise cardiac output assessed from exercise cardiac magnetic resonance imaging) for predicting the development of functional disability 12-months following AC. Secondary aims are to assess the effects of ET on VO2peak, left ventricular morphology, vascular stiffness, cardiac biomarkers, body composition, bone mineral density, muscle strength, physical function, habitual physical activity, cognitive function, and multidimensional quality of life.

METHODS

One hundred women with early-stage BCa (40-75 years) scheduled for AC will be randomized to 12-months of structured exercise training (n = 50) or a usual care control group (n = 50). Participants will be assessed at baseline, 4-weeks following completion of AC (4-months) and at 12-months for all measures.

DISCUSSION

Women diagnosed with early-stage BCa have increased cardiac mortality. More sensitive strategies for diagnosing and preventing AC-induced cardiovascular impairment are critical for reducing cardiovascular morbidity and improving long-term health outcomes in BCa survivors.

TRIAL REGISTRATION

Australia & New Zealand Clinical Trials Registry (ANZCTR), ID: 12617001408370 . Registered on 5th of October 2017.

Circulating troponin and further left ventricular ejection fraction improvement in patients with previously recovered left ventricular ejection fraction

AIMS

The aim of this study is to determine factors associated with long-term recovery of left ventricular ejection fraction (LVEF) in patients with heart failure with reduced EF (HFrEF) and if further recovery also occurs in this group.

METHODS AND RESULTS

Among 621 participants enrolled in the Alberta Heart Failure Etiology and Analysis Team (HEART) Study, 316 with Stage C HF underwent comprehensive imaging and biomarker testing at enrolment and at 1-year follow up. Using pre-enrolment data, HF with recovered EF (HFrecEF) was defined as an absolute improvement ≥5% in LVEF from the prior lowest LVEF value, with a final LVEF value > 35% at or prior to study baseline. Participants with all LVEF > 40% were included for comparison. Hospitalization-free survival to 5 years was performed. The median cohort age was 66 years, and time from diagnosis was 4 years; 82% were male patients. Of the 316 patients, 95 (30%) patients had HFrecEF and 56 (18%) patients pHFrEF. On multivariate analysis, only shorter duration of HF was predictive of HFrecEF status. Over 1 year, LVEF increased in the HFrecEF group 4.0% (0.15-7.90, P = 0.042) as compared with persistent HFrEF, who in turn demonstrated higher baseline serum high sensitivity Troponin-T with further increase at follow up 0.55(0.33-0.86, P = 0.011). No change in any parameter in the HFpEF/HFmrEF group at follow up was observed.

CONCLUSIONS

Patients with HFrecEF demonstrate evidence of additional late improvement in LVEF and unchanged troponin levels, in contrast to those with persistent HFrEF, where LVEF does not improve and serum troponin rises over time. These data help to inform mechanisms relating to late LV remodelling.

Association of Exercise and Swimming Goggles With Modulation of Cerebro-ocular Hemodynamics and Pressures in a Model of Spaceflight-Associated Neuro-ocular Syndrome

Importance

Astronauts on International Space Station missions demonstrate adverse neuro-ocular changes. Reversing a negative translaminar pressure gradient (TLPG) by modulating cerebral blood flow, decreasing intracranial pressure, or increasing intraocular pressure (IOP) has been proposed as potential intervention for spaceflight-associated neuro-ocular syndrome (SANS).

Objective

To examine whether exercise (resistance, moderate-intensity aerobic, and high-intensity aerobic) or artificially increasing IOP is associated with modulated cerebro-ocular hemodynamic and pressure changes during head-down tilt (HDT), an analogue of spaceflight, in healthy adults.

Design, Setting, and Participants

A single-center investigation was conducted at Johnson Space Center, Houston, Texas, from January 1, 2014, to December 31, 2016, in 20 healthy men.

Exposure

On 3 separate days, participants rested supine, were tilted to -15° HDT, and then completed 1 of 3 experimental exercise conditions (moderate-intensity aerobic, resistance, or high-intensity interval aerobic). A subset of 10 participants wore swimming goggles on all days.

Main Outcomes and Measures

Applanation rebound tonometry was used to noninvasively assess IOP, and compression sonography was used to assess internal jugular venous pressure (IJVP). Estimated TLPG was calculated as the difference between IOP and IJVP. Cerebral inflow and outflow were measured in extracranial arteries using color-coded duplex ultrasonography.

Results

Twenty men participated in the study (mean [SD] age, 36 [9] years). Compared with supine IOP (mean [SD], 19.3 [3.7] mm Hg), IJVP (mean [SD], 21.4 [6.0] mm Hg), and estimated TLPG (mean [SD], -2.1 [7.0] mm Hg), -15° HDT was associated with increased IOP (mean difference, 2.3 mm Hg; 95% CI, 1.4-3.3 mm Hg; P < .001) and IJVP (mean difference, 10.5 mm Hg; 95% CI, 8.9-12.2 mm Hg; P < .001) and with decreased TLPG (mean difference, -8.2 mm Hg; 95% CI, -10.1 to -6.3 mm Hg; P < .001). Exercise (regardless of modality) at -15° HDT was associated with decreased IOP (mean difference, -1.6 mm Hg; 95% CI, -2.6 to -0.6 mm Hg; P = .002) and TLPG (mean difference, -3.5 mm Hg; 95% CI, -6.2 to -0.7 mm Hg; P = .01) compared with rest. Both IOP (mean difference, 2.9 mm Hg; 95% CI, 0.7-5.1 mm Hg; P = .01) and TLPG (mean difference, 5.1 mm Hg; 95% CI, 0.8-9.4 mm Hg; P = .02) were higher in participants who wore swimming goggles compared with those not wearing goggles.

Conclusions and Relevance

In this study, exercise was associated with decreased IOP and estimated translaminar pressure gradient in a spaceflight analogue of HDT. The addition of swimming goggles was associated with increased IOP and TLPG in HDT. Further evaluation in spaceflight may be warranted to determine whether modestly increasing IOP is an effective SANS countermeasure.

Exercise Intolerance in Anthracycline-Treated Breast Cancer Survivors: The Role of Skeletal Muscle Bioenergetics, Oxygenation, and Composition

BACKGROUND

Peak oxygen consumption (VO₂ ) is reduced in women with a history of breast cancer (BC). We measured leg blood flow, oxygenation, bioenergetics, and muscle composition in women with BC treated with anthracycline chemotherapy (n = 16, mean age: 56 years) and age- and body mass index-matched controls (n = 16).

MATERIALS AND METHODS

Whole-body peak VO₂ was measured during cycle exercise. ³¹ Phosphorus magnetic resonance (MR) spectroscopy was used to measure muscle bioenergetics during and after incremental to maximal plantar flexion exercise (PFE). MR imaging was used to measure lower leg blood flow, venous oxygen saturation (S_v O₂ ), and VO₂ during submaximal PFE, and abdominal, thigh, and lower leg intermuscular fat (IMF) and skeletal muscle (SM).

RESULTS

Whole-body peak VO₂ was significantly lower in BC survivors versus controls (23.1 ± 7.5 vs. 29.5 ± 7.7 mL/kg/minute). Muscle bioenergetics and mitochondrial oxidative capacity were not different between groups. No group differences were found during submaximal PFE for lower leg blood flow, S_v O₂ , or VO₂ . The IMF-to-SM ratio was higher in the thigh and lower leg in BC survivors (0.36 ± 0.19 vs. 0.22 ± 0.07, p = .01; 0.10 ± 0.06 vs. 0.06 ± 0.02, p = .03, respectively) and were inversely related to whole-body peak VO₂ (r = -0.71, p = .002; r = -0.68, p = .003, respectively)_. In the lower leg, IMF-to-SM ratio was inversely related to VO₂ and O₂ extraction during PFE.

CONCLUSION

SM bioenergetics and oxidative capacity in response to PFE are not impaired following anthracycline treatment. Abnormal SM composition (increased thigh and lower leg IMF-to-SM ratio) may be an important contributor to reduced peak VO₂ during whole-body exercise among anthracycline-treated BC survivors.

IMPLICATIONS FOR PRACTICE

Peak oxygen consumption (peak VO₂ ) is reduced in breast cancer (BC) survivors and is prognostic of increased risk of cardiovascular disease-related and all-cause mortality. Results of this study demonstrated that in the presence of deficits in peak VO₂ 1 year after anthracycline therapy, skeletal muscle bioenergetics and oxygenation are not impaired. Rather, body composition deterioration (e.g., increased ratio of intermuscular fat to skeletal muscle) may contribute to reduced exercise tolerance in anthracycline BC survivors. This finding points to the importance of lifestyle interventions including caloric restriction and exercise training to restore body composition and cardiovascular health in the BC survivorship setting.