Exercise intolerance

Acute Effects of Skeletal Muscle Electrical Stimulation on Central and Lower Extremity Hemodynamics

INTRODUCTION

Belt electrode-skeletal muscle electrical stimulation (B-SES) is a treatment prescribed for individuals with difficulty performing exercise therapy that improves muscle strength, exercise tolerance, and glucose metabolism. However, the effects of B-SES on the hemodynamics of the central and lower extremity conduit arteries have not been studied. Therefore, this study compared the acute effects of B-SES on the central and lower extremity conduit arteries in healthy young males.

METHODS

This randomized crossover study included nine healthy young males (mean age: 21.0±1.1 years). Participants were assigned to the following experimental conditions, with a washout period of one week: condition 1 included 20 min of electrical stimulation of the lower extremity at the participant's sensation threshold intensity (Sham, n=9) and condition 2 included 20 min of electrical stimulation of the lower extremity at the maximum intensity the participant can tolerate (B-SES, n=9). The heart rate (HR), stroke volume (SV), cardiac output (CO), mean arterial pressure (MAP), and total peripheral vascular resistance (TPR) were measured as central hemodynamics. The hemodynamics of the lower extremity conduit arteries were measured and calculated for the shallow femoral artery (SFA), including vessel diameter, mean blood flow velocity (MBFV), shear rate (SR), and mean blood flow (MBF) rate. These indices were measured before stimulation (Pre), 10 min after the start of stimulation (Stimulating), and immediately after the end of stimulation (Post). These indices were compared using a repeated two-way analysis of variance.

RESULTS

In B-SES, HR (Pre: 63.2±8.6; Stimulating: 73.7±6.9; Post: 70.0±4.2 bpm, p<0.01), CO (Pre: 5.1±1.0; Stimulating: 6.5±1.5, p<0.01; Post: 6.3±1.2 L/min, p=0.02), and MAP (Pre: 104.0±11.5; Stimulating: 116.4±10.8, p<0.01; Post: 109.6±9.7 mmHg, p=0.02) increased significantly. In addition, B-SES significantly increased MBFV (Pre: 19.2±4.0; Stimulating: 50.5±14.9; Post: 30.1±4.0 cm/s, p<0.01), SR (Pre: 118.9±28.8; Stimulating: 302.7±91. 2, p<0.01; Post: 182.1±70.1/s, p=0.02), and MBF (Pre: 382.0±61.5; Stimulating: 1009.6±321.4; Post: 626.8±176.6 mL/min, p<0.01). However, there were no significant changes in SV and TPR.

CONCLUSIONS

The findings of this study indicate that B-SES in healthy young males increases CO without increasing SV or TPR and improves the MBFV and SR in the SFA.

An Index for Evaluating Exercise Capacity Improvement After Cardiac Rehabilitation in Patients After Myocardial Infarction

OBJECTIVE

We investigated relationships among predictors of improvement in exercise capacity after cardiac rehabilitation programs in patients after acute myocardial infarction.

METHODS

We carried out a secondary analysis of data from 41 patients with a left ventricular ejection fraction ≥ 40% who underwent cardiac rehabilitation after the first myocardial infarction. Participants were assessed using a cardiopulmonary exercise test and stress echocardiography. A cluster analysis was performed, and the principal components were analyzed.

RESULTS

Two distinct clusters with significantly different ( P = .005) proportions of response to treatment (peak VO 2 ≥ 1 mL/kg/min) were identified among patients. The first principal component explained 28.6% of the variance. We proposed an index composed of the top 5 variables from the first component to represent the improvement in exercise capacity. The index was the average of scaled O 2 uptake and CO 2 output at peak exercise, minute ventilation at peak, load achieved at peak exercise, and exercise time. The optimal cutoff for the improvement index was 0.12, which outperformed the peak VO 2 ≥ 1 mL/kg/min criterion in recognizing the clusters, with a C-statistic of 91.7% and 72.3%, respectively.

CONCLUSION

The assessment of change in exercise capacity after cardiac rehabilitation could be improved using the composite index.

Relationships among norepinephrine levels, exercise capacity, and chronotropic responses in heart failure patients

In heart failure (HF) patients, the pathophysiological mechanisms of severe exercise intolerance and impaired exercise capacity are related to both central and peripheral abnormalities. The central abnormalities in HF patients include impaired cardiac function and chronotropic incompetence (CI). Indeed, CI, the inability to adequately increase heart rate (HR) from rest to exercise often exhibited by HF patients, is related to activation of the sympathetic nervous system (SNS) yielding a rise in circulating norepinephrine (NE). CI may result from downregulation of β-adrenergic receptors, β-blocker usage, high baseline HR, or due to a combination of factors. This paper discusses the role of elevated NE in altering chronotropic responses in HF patients and consequently resulting in impaired exercise capacity. We suggest that future research should focus on the potential treatment of CI with rate-adaptive pacing, using a sensor to measure physical activity, without inducing deleterious hormonal activation of the sympathetic system.

Leptin administration during lactation leads to different nutritional, biometric, hemodynamic, and cardiac outcomes in prepubertal and adult female Wistar rats

Literature reports that insults, such as hormonal disturbances, during critical periods of development may modulate organism physiology and metabolism favoring cardiovascular diseases (CVDs) later in life. Studies show that leptin administration during lactation leads to cardiovascular dysfunction in young and adult male Wistar rats. However, there are sex differences regarding CVD. Thus, the present work aimed to investigate neonatal leptin administration's consequences on different outcomes in female rats at prepubertal and adult age. Newborn Wistar female rats were divided into two groups, Leptin and Control, receiving daily subcutaneous injections of this adipokine (8 μg/100 g) or saline for the first 10 of 21 d of lactation. Nutritional, biometric, hemodynamic, and echocardiographic parameters, as well as maximal effort ergometer performance, were determined at postnatal days (PND) 30 and 150. Leptin group presented lower food intake (p = 0.0003) and higher feed efficiency (p = 0.0058) between PND 21 and 30. Differences concerning echocardiographic parameters revealed higher left ventricle internal diameter (LVID) in systole (p = 0.0051), as well as lower left ventricle ejection fraction (LVEF) (p = 0.0111) and fractional shortening (FS) (p = 0.0405) for this group at PND 30. Older rats treated with leptin during lactation presented only higher LVID in systole (p = 0.0270). Systolic blood pressure and maximum effort ergometer test performance was similar between groups at both ages. These data suggest that nutritional, biometric, and cardiac outcomes due to neonatal leptin administration in female rats are age-dependent.

Overweight during lactation and its implications for biometric, nutritional and cardiovascular parameters of young and adult male and female rats

Litter size reduction can induce early overnourishment, being an attractive experimental model to study short- and long-term consequences of childhood obesity. Epidemiological data indicate sex differences regarding cardiometabolic disorders and hypertrophic cardiomyopathy. The present study aimed to describe biometric, nutritional and cardiovascular changes related to neonatal overweight promoted by litter size reduction in young and adult Wistar rats of both sexes. Litter adjustment to eight or four pups/mother (1:1 male-to-female ratio) gave, respectively, control and overweight groups. Body mass, food intake, haemodynamic and echocardiographic parameters and cardiorespiratory capacity were evaluated at postnatal days 30 and 150. Diminished litters were correlated with higher body mass and weight gain (12 %) during lactation, validating the experimental model of neonatal overweight. Soon after weaning male (16 %) and female (25 %) offspring of these litters presented a lower food intake than their respective control, without differences in body mass. Adult males from reduced litters presented higher abdominal circumference (7 %), systolic blood pressure (10 %), interventricular septum thickness (15 %) and relative wall thickness (15 %) compared with their respective control. Rats' performance on the maximal effort ergometer test was not affected by neonatal overweight. Data suggest the occurrence of catch-down growth and hypophagia in male and female rats submitted to neonatal overweight. However, only male rats presented haemodynamic and cardiac structural changes. These findings are crucial to personalised/gender medicine.

Reduced exercise capacity and clinical outcomes following acute myocardial infarction

Reduced exercise capacity is known to be an important predictor of poor prognosis and disability in patients with cardiovascular diseases and chronic heart failure, and even members of the general population. However, data about exercise capacity assessed by cardiopulmonary exercise testing (CPX) in acute myocardial infarction (AMI) patients who underwent primary percutaneous coronary intervention (PCI) is scarce. Among 594 consecutive AMI patients who underwent primary PCI, we examined 136 patients (85.3% men, 64.9 ± 11.9 years) who underwent CPX during hospitalization for AMI. CPX was usually performed 5 days after the onset of AMI. Reduced exercise capacity was defined as peak VO₂ ≤ 12. Clinical outcomes including all-cause death, myocardial infarction, and hospitalization due to heart failure were followed. Among 136 patients, reduced exercise capacity (peak VO₂ ≤ 12) was seen in 38 patients (28%). Patients with reduced exercise capacity were older, more likely to have hypertension, and had lower renal function. In echocardiography, patients with reduced exercise capacity had higher E/e' and larger left atrial dimension. Multivariate logistic analysis showed that E/e' (OR 1.19, 95% CI 1.09-1.31, p < 0.001) was an independent predictor of reduced exercise capacity (peak VO₂ ≤ 12). Median follow-up term was 12 months (IQR 9-22). The occurrence of composite endpoints of all-cause death, myocardial infarction, and hospitalization due to heart failure was significantly higher in patients with peak VO₂ ≤ 12 than those with peak VO₂ > 12 (p < 0.001). Reduced exercise capacity following primary PCI in AMI patients is associated with diastolic dysfunction and may lead to poorer clinical outcomes.

CHA2DS2-VASc score predicts exercise intolerance in young and middle-aged male patients with asymptomatic atrial fibrillation

Exercise intolerance among the clinical symptoms in patients with atrial fibrillation (AF) has usually been masked by their adjusted life style. We sought to assess the role of CHA₂DS₂-VASc score to predict exercise intolerance in asymptomatic AF patients, and further examine whether the relationship differs by age and gender. Among the 6,275 participants of the prospective Korean registry of the Comparison study of Drugs for symptom control and complication prevention of Atrial Fibrillation (CODE-AF), 1,080 AF patients who underwent exercise treadmill testing were studied. Exercise intolerance was defined as a peak exercise capacity of 7 metabolic equivalents (METs) or less, and the patients were divided into two groups for the analysis: ≤7 METs (n = 131) and >7 METs (n = 949). Patients with exercise intolerance had a significantly higher CHA₂DS₂-VASc score than those without (3.1 ± 1.3 vs. 2.0 ± 1.5, p < 0.0001). In the multivariate analysis, a higher CHA₂DS₂-VASc score (OR 1.54, 95% CI 1.31–1.81, p < 0.0001), corrected QT interval (OR 1.01, 95% CI 1.00–1.02, p = 0.026), and increased left atrial volume index (OR 1.02, 95% CI 1.01–1.03, p = 0.001) were found to be independent predictors of exercise intolerance. The impact of the CHA₂DS₂-VASc score on exercise intolerance was significant only in male patients aged <65 years (OR 3.30, 95% CI 1.76–6.19, p < 0.0001). The CHA₂DS₂-VASc score may be a feasible risk assessment tool to predict exercise intolerance, especially in young and middle-aged male patients with asymptomatic AF.

Left atrial deformation analysis by speckle tracking echocardiography to predict exercise capacity after myocardial infarction

INTRODUCTION

Left atrial (LA) size and function are associated with outcome after myocardial infarction (MI). In this study we aimed to assess the impact of LA function as a predictor of exercise capacity through speckle tracking echocardiography.

METHODS

A total of 94 patients (mean age 54.8±11.0 years; 82% male) were enrolled one month after MI. Echocardiography was used to assess LA volumes and various indices of LA conduit, contraction and reservoir function. LA deformation was assessed by two-dimensional speckle tracking to calculate strain and strain rate at different phases of the cardiac cycle. Exercise capacity was assessed by oxygen uptake (VO₂) on cardiopulmonary exercise testing.

RESULTS

Increased LA volumes, especially LA volume before atrial contraction, were correlated with reduced peak VO₂ and reduced VO₂ at anaerobic threshold. Decreased peak VO₂ was associated with reduced LA conduit function (ρ=0.24; p=0.02), but not with LA booster function (ρ=-0.07; p=0.53). Lower peak atrial longitudinal strain was associated with worse exercise capacity (ρ=0.24; p=0.02).

CONCLUSIONS

After MI, increased LA volumes were markers of decreased functional capacity that was associated with decreased LA conduit function, but not with LA contractile function. In these patients, LA longitudinal strain analysis may be useful to predict reduced exercise capacity.

Periodic Breathing during Incremental Exercise

Periodic breathing during incremental cardiopulmonary exercise testing is a regularly recurring waxing and waning of tidal volume due to oscillations in central respiratory drive. Periodic breathing is a sign of respiratory control system instability, which may occur at rest or during exercise. The possible mechanisms responsible for exertional periodic breathing might be related to any instability of the ventilatory regulation caused by: (1) increased circulatory delay (i.e., circulation time from the lung to the brain and chemoreceptors due to reduced cardiac index leading to delay in information transfer), (2) increase in controller gain (i.e., increased central and peripheral chemoreceptor sensitivity to arterial partial pressure of oxygen and of carbon dioxide), or (3) reduction in system damping (i.e., baroreflex impairment). Periodic breathing during exercise is observed in several cardiovascular disease populations, but it is a particularly frequent phenomenon in heart failure due to systolic dysfunction. The detection of exertional periodic breathing is linked to outcome and heralds worse prognosis in heart failure, independently of the criteria adopted for its definition. In small heart failure cohorts, exertional periodic breathing has been abolished with several dedicated interventions, but results have not yet been confirmed. Accordingly, further studies are needed to define the role of visceral feedbacks in determining periodic breathing during exercise as well as to look for specific tools for preventing/treating its occurrence in heart failure.

Dietary nitrate supplementation in cardiovascular health: an ergogenic aid or exercise therapeutic?

Oral consumption of inorganic nitrate, which is abundant in green leafy vegetables and roots, has been shown to increase circulating plasma nitrite concentration, which can be converted to nitric oxide in low oxygen conditions. The associated beneficial physiological effects include a reduction in blood pressure, modification of platelet aggregation, and increases in limb blood flow. There have been numerous studies of nitrate supplementation in healthy recreational and competitive athletes; however, the ergogenic benefits are currently unclear due to a variety of factors including small sample sizes, different dosing regimens, variable nitrate conversion rates, the heterogeneity of participants’ initial fitness levels, and the types of exercise tests used. In clinical populations, the study results seem more promising, particularly in patients with cardiovascular diseases who typically present with disruptions in the ability to transport oxygen from the atmosphere to working tissues and reduced exercise tolerance. Many of these disease-related, physiological maladaptations, including endothelial dysfunction, increased reactive oxygen species, reduced tissue perfusion, and muscle mitochondrial dysfunction, have been previously identified as potential targets for nitric oxide restorative effects. This review is the first of its kind to outline the current evidence for inorganic nitrate supplementation as a therapeutic intervention to restore exercise tolerance and improve quality of life in patients with cardiovascular diseases. We summarize the factors that appear to limit or maximize its effectiveness and present a case for why it may be more effective in patients with cardiovascular disease than as ergogenic aid in healthy populations.

Myocardial strain may predict exercise tolerance in patients with reduced and mid-range ejection fraction

BACKGROUND

Conventional echocardiographic parameters, such as rest ejection fraction, perform poorly in the prediction of exercise tolerance in heart failure. The aim of the present study was to evaluate the contribution of hemodynamic instability in the observed lower functional capacity and investigate the role of left ventricular strain for the prediction of stress test duration in obese hypertensive patients with reduced ejection fraction.

METHODS

Sixty-one patients with reduced ejection fraction underwent treadmill exercise echocardiography. Systolic and diastolic echocardiographic parameters were recorded. Moreover, the presence of hemodynamic instability was assessed through N-terminal pro B-type natriuretic peptide (NT-proBNP) measurements at baseline and peak exercise.

RESULTS

Rest and peak NT-proBNP levels, and their difference, were significantly correlated with mean global strain at peak, which was the only parameter associated with changes in NT-proBNP levels. Rest and peak mean global strain were found to be predictive for the duration of treadmill stress test. In particular, mean global strain, but not left ventricular ejection fraction, was independently correlated with exercise ability.

CONCLUSIONS

Stress echocardiography may provide important information regarding exercise tolerance in obese hypertensive patients with reduced ejection fraction, mainly through the evaluation of left ventricular strain. The obtained evidence may also have prognostic value, particularly in the early stages of the syndrome.

Role of cardiopulmonary exercise testing in clinical stratification in heart failure. A position paper from the Committee on Exercise Physiology and Training of the Heart Failure Association of the European Society of Cardiology

Traditionally, the main indication for cardiopulmonary exercise testing (CPET) in heart failure (HF) was for the selection of candidates to heart transplantation: CPET was mainly performed in middle-aged male patients with HF and reduced left ventricular ejection fraction. Today, CPET is used in broader patients' populations, including women, elderly, patients with co-morbidities, those with preserved ejection fraction, or left ventricular assistance device recipients, i.e. individuals with different responses to incremental exercise and markedly different prognosis. Moreover, the diagnostic and prognostic utility of symptom-limited CPET parameters derived from submaximal tests is more and more considered, since many patients are unable to achieve maximal aerobic power. Repeated tests are also being used for risk stratification and evaluation of intervention, so that these data are now available. Finally, patients, physicians and healthcare decision makers are increasingly considering how treatments might impact morbidity and quality of life rather than focusing more exclusively on hard endpoints (such as mortality) as was often the case in the past. Innovative prognostic flowcharts, with CPET at their core, that help optimize risk stratification and the selection of management options in HF patients, have been developed.

Skeletal Muscle Alterations Are Exacerbated in Heart Failure With Reduced Compared With Preserved Ejection Fraction: Mediated by Circulating Cytokines?

BACKGROUND

A greater understanding of the different underlying mechanisms between patients with heart failure with reduced (HFrEF) and with preserved (HFpEF) ejection fraction is urgently needed to better direct future treatment. However, although skeletal muscle impairments, potentially mediated by inflammatory cytokines, are common in both HFrEF and HFpEF, the underlying cellular and molecular alterations that exist between groups are yet to be systematically evaluated. The present study, therefore, used established animal models to compare whether alterations in skeletal muscle (limb and respiratory) were different between HFrEF and HFpEF, while further characterizing inflammatory cytokines.

METHODS AND RESULTS

Rats were assigned to (1) HFrEF (ligation of the left coronary artery; n=8); (2) HFpEF (high-salt diet; n=10); (3) control (con: no intervention; n=7). Heart failure was confirmed by echocardiography and invasive measures. Soleus tissue in HFrEF, but not in HFpEF, showed a significant increase in markers of (1) muscle atrophy (ie, MuRF1, calpain, and ubiquitin proteasome); (2) oxidative stress (ie, higher nicotinamide adenine dinucleotide phosphate oxidase but lower antioxidative enzyme activities); (3) mitochondrial impairments (ie, a lower succinate dehydrogenase/lactate dehydrogenase ratio and peroxisome proliferator-activated receptor-γ coactivator-1α expression). The diaphragm remained largely unaffected between groups. Plasma concentrations of circulating cytokines were significantly increased in HFrEF for tumor necrosis factor-α, whereas interleukin-1β and interleukin-12 were higher in HFpEF.

CONCLUSIONS

Our findings suggest, for the first time, that skeletal muscle alterations are exacerbated in HFrEF compared with HFpEF, which predominantly reside in limb, rather than in respiratory, muscle. This disparity may be mediated, in part, by the different circulating inflammatory cytokines that were elevated between HFpEF and HFrEF.

Supplementation with a Polyphenol-Rich Extract, PerfLoad®, Improves Physical Performance during High-Intensity Exercise: A Randomized, Double Blind, Crossover Trial

Workout capacity is energy-production driven. To produce peak metabolic power outputs, the organism predominantly relies more on anaerobic metabolism, but this undoubtedly has a negative and limiting impact on muscle function and performance. The aim of the study was to evaluate if an innovative polyphenol-based food supplement, PerfLoad^®, was able to improve metabolic homeostasis and physical performance during high-intensity exercises under anaerobic conditions. The effect of a supplementation has been investigated on fifteen recreationally-active male athletes during a randomized, double-blind and crossover clinical investigation. The Wingate test, an inducer of an unbalanced metabolism associated to oxidative stress, was used to assess maximum anaerobic power during a high-intensity exercise on a cycle ergometer. Supplementation with PerfLoad^® correlated with a significant increase in total power output (5%), maximal peak power output (3.7%), and average power developed (5%), without inducing more fatigue or greater heart rate. Instead, oxidative homeostasis was stabilized in supplemented subjects. Such results demonstrated that PerfLoad^® is a natural and efficient solution capable of, similarly to training benefits, helping athletes to improve their physical performance, while balancing their metabolism and reducing exercise-induced oxidative stress.

Menopause and Exercise Intolerance

Central adiposity and weight gain are common among postmenopausal women. Because of the metabolic changes that many postmenopausal women experience, there can be a decrease in exercise tolerance related to the loss of potent estrogens. This can lead to the development of insulin resistance and endothelial dysfunction. Despite the challenges that exercise intolerance may pose for some postmenopausal women, evidence suggests that regular exercise and caloric restriction are crucial for weight management after menopause.

Adenosine A2A receptor agonist prevents cardiac remodeling and dysfunction in spontaneously hypertensive male rats after myocardial infarction

Background

This work evaluated the hypothesis that 3,4-methylenedioxybenzoyl-2-thienylhydrazone (LASSBio-294), an agonist of adenosine A_2A receptor, could be beneficial for preventing cardiac dysfunction due to hypertension associated with myocardial infarction (MI).

Methods

Male spontaneously hypertensive rats (SHR) were randomly divided into four groups (six animals per group): sham-operation (SHR-Sham), and myocardial infarction rats (SHR-MI) were treated orally either with vehicle or LASSBio-294 (10 and 20 mg.kg⁻¹.d⁻¹) for 4 weeks. Echocardiography and in vivo hemodynamic parameters measured left ventricle (LV) structure and function. Exercise tolerance was evaluated using a treadmill test. Cardiac remodeling was accessed by LV collagen deposition and tumor necrosis factor α expression.

Results

Early mitral inflow velocity was significantly reduced in the SHR-MI group, and there was significant recovery in a dose-dependent manner after treatment with LASSBio-294. Exercise intolerance observed in the SHR-MI group was prevented by 10 mg.kg⁻¹.d⁻¹ of LASS-Bio-294, and exercise tolerance exceeded that of the SHR-Sham group at 20 mg.kg⁻¹.d⁻¹. LV end-diastolic pressure increased after MI, and this was prevented by 10 and 20 mg.kg⁻¹.d⁻¹ of LASSBio-294. Sarcoplasmic reticulum Ca²⁺ ATPase levels were restored in a dose-dependent manner after treatment with LASSBio-294. Fibrosis and inflammatory processes were also counteracted by LASSBio-294, with reductions in LV collagen deposition and tumor necrosis factor α expression.

Conclusion

In summary, oral administration of LASSBio-294 after MI in a dose-dependent manner prevented the development of cardiac dysfunction, demonstrating this compound’s potential as an alternative treatment for heart failure in the setting of ischemic heart disease with superimposed chronic hypertension.

Noninvasive assessment of exercise tolerance using mitral annular velocities

PURPOSE

To investigate the feasibility of evaluating exercise tolerance using lateral and septal mitral annular velocities in patients with preserved left ventricular ejection fraction (LVEF) and those with reduced LVEF.

METHOD

We studied 36 patients with LVEF ≥50% and 36 with LVEF <50%. We measured peak early diastolic velocity of transmitral flow (E) and peak early diastolic velocities of the lateral (LEa) and septal (SEa) mitral annulus. The ratios of E to LEa (E/LEa) and E to SEa (E/SEa) were calculated. We measured peak oxygen consumption [Formula: see text] and anaerobic threshold (AT) by cardiopulmonary exercise testing.

RESULTS

In patients with LVEF ≥50%, E/LEa correlated well with [Formula: see text] and AT (r = -0.69 and r = -0.74, respectively; p < 0.001); E/SEa correlated modestly (r = -0.59 and r = -0.60, respectively; p < 0.001). In patients with LVEF <50%, E/LEa correlated well with [Formula: see text] and AT (r = -0.72 and r = -0.76; respectively, p < 0.001); E/SEa correlated modestly (r = -0.63 and r = -0.63, respectively; p < 0.001).

CONCLUSION

E/LEa may be more useful than E/SEa for the noninvasive estimation of exercise tolerance, throughout a wide range of LVEF.

Improving functional capacity in heart failure: the need for a multifaceted approach

PURPOSE OF REVIEW

Functional capacity is a broad term that describes a person's ability to perform the daily activities that require physical exertion. Patients diagnosed with heart failure, regardless of cause, demonstrate a compromised functional capacity. The ability to perform aerobic activities is a central, but not complete, determinant of functional capacity. Muscular strength and endurance are other important elements of functional capacity. It is well established that patients with heart failure demonstrate attenuated muscular strength and endurance as a consequence of their disease process. Typically, a heart failure patient's ability to perform daily activities that are either aerobic or resistive in nature is compromised and contributes to the decline in functional capacity.

RECENT FINDINGS

There is an abundance of literature demonstrating that exercise training improves aerobic capacity and muscular strength and endurance in those with heart failure. These training benefits translate to an improvement in functional capacity and an enhanced ability to perform activities of daily living. There are several approaches to exercise training in the heart failure population, each of which has implications for the degree to which functional capacity can be improved.

SUMMARY

This review summarizes the current body of literature related to exercise training as a means of optimizing functional capacity in patients with heart failure.

The role of a structured exercise training program on cardiac structure and function after acute myocardial infarction: study protocol for a randomized controlled trial

BACKGROUND

Exercise training is effective in improving functional capacity and quality of life in patients with coronary artery disease, but its effects on left ventricular systolic and diastolic function are controversial. Diastolic dysfunction is a major determinant of adverse outcome after myocardial infarction and, contrary to systolic function, no therapy or intervention has proved to significantly improve diastolic function. Data from animal studies and from patients with diastolic heart failure has suggested that exercise training can have a positive effect on diastolic function parameters. This trial aims to evaluate if a structured exercise training program can improve resting left ventricular diastolic and systolic function in patients who have had an acute myocardial infarction.

METHODS/DESIGN

This is a phase II, prospective, randomized, open-label, blinded-endpoint trial that will include at least 96 consecutive patients who have had an acute myocardial infarction one month previously. Patients will be randomized (1:1) to an exercise training program or a control group, receiving standard of care. At enrolment, and at the end of the follow-up period, patients will be submitted to an echocardiography (with detailed assessment of diastolic and systolic function using recent consensus guidelines), cardiopulmonary exercise testing, an anthropometric assessment, blood testing, and clinical evaluation. Patients randomized to the intervention group will be submitted to an eight-week outpatient exercise program, combining endurance and resistance training, for three sessions per week. The primary endpoint will be the change in lateral E' velocity immediately after the eight-week exercise training program. Secondary endpoints will include other echocardiographic parameters of left ventricular diastolic and systolic function, cardiac structure, metabolic and inflammation biomarkers (high-sensitivity C-reactive protein and pro-BNP), functional capacity (peak oxygen consumption and anaerobic threshold) and anthropometric measurements.

DISCUSSION

New strategies that can improve left ventricular diastolic function are clinically needed. This will be the first trial to evaluate, in patients who have had an acute myocardial infarction, the effects of a structured program of exercise training on diastolic and systolic function, assessed by novel echocardiographic parameters.

TRIAL REGISTRATION

Registered with ClinicalTrials.gov (reference: NCT02224495 ) on 21 August 2014.

Left ventricular diastolic dysfunction and E/E' ratio as the strongest echocardiographic predictors of reduced exercise capacity after acute myocardial infarction

BACKGROUND

The mechanisms that determine reduced exercise capacity after acute myocardial infarction (AMI) are not fully understood, especially the relative role of left ventricular diastolic and systolic function.

HYPOTHESIS

To evaluate the role of different diastolic and systolic function echocardiographic parameters as predictors of reduced functional capacity in patients after AMI.

METHODS

One month after AMI, 225 patients (84% male; mean age, 55.1 ± 10.9 years) were enrolled and underwent detailed echocardiography and cardiopulmonary exercise test on the same day. Systolic and diastolic function was evaluated by echocardiography according to the latest consensus recommendations, including tissue Doppler evaluation. Exercise capacity was evaluated with peak oxygen consumption (VO(2)).

RESULTS

Peak VO(2) was significantly correlated with early diastolic tissue Doppler velocity (E') septal (r = 0.42, P < 0.001), E' lateral (r = 0.35, P < 0.001), septal E/E' ratio (r = -0.35, P = 0.001), and lateral E/E' (r = -0.27, P < 0.001). These diastolic function parameters predicted impaired exercise capacity (VO(2) <19 mL/kg/min), with an area under the receiver operating characteristic curve of 0.77 (95% confidence interval [CI]: 0.68-0.86, P < 0.001) for septal E/E'. On multivariate analysis, for each unit increase in septal E/E' ratio there was a -0.35 (95% CI: -0.54 to -0.15) mL/kg/min decrease in peak VO(2) independently of age, sex, body mass index, hypertension, and diabetes. There was a mild correlation between peak VO(2) and systolic function parameters (r = 0.17, P = 0.01 with ejection fraction; and r = 0.23, P = 0.02 with lateral systolic tissue Doppler velocity) that persisted after multivariate adjustment.

CONCLUSIONS

After AMI, resting diastolic function parameters were the strongest correlates of exercise tolerance. Septal E/E' ratio was the best echocardiographic predictor of reduced functional capacity.

Effects of an interatrial shunt on rest and exercise hemodynamics: results of a computer simulation in heart failure

BACKGROUND

A treatment based on an interatrial shunt device has been proposed for counteracting elevated pulmonary capillary wedge pressure (PCWP) in patients with heart failure and mildly reduced or preserved ejection fraction (HFpEF). We tested the theoretical hemodynamic effects of this approach with the use of a previously validated cardiovascular simulation.

METHODS AND RESULTS

Rest and exercise hemodynamics data from 2 previous independent studies of patients with HFpEF were simulated. The theoretical effects of a shunt between the right and left atria (diameter up to 12 mm) were determined. The interatrial shunt lowered PCWP by ~3 mm Hg under simulated resting conditions (from 10 to 7 mm Hg) and by ~11 mm Hg under simulated peak exercise conditions (from 28 to 17 mm Hg). Left ventricular cardiac output decreased ~0.5 L/min at rest and ~1.3 L/min at peak exercise, with corresponding increases in right ventricular cardiac output. However, because of the reductions in PCWP, right atrial and pulmonary artery pressures did not increase. A majority of these effects were achieved with a shunt diameter of 8-9 mm. The direction of flow though the shunt was left to right in all of the conditions tested.

CONCLUSIONS

The interatrial shunt reduced left-sided cardiac output with a marked reduction in PCWP. This approach may reduce the propensity for heart failure exacerbations and allow patients to exercise longer, thus attaining higher heart rates and cardiac outputs with the shunt compared with no shunt. These results support clinical investigation of this approach and point out key factors necessary to evaluate its safety and hemodynamic effectiveness.

Aging reduces left atrial performance during adrenergic stress in middle aged and older patients

BACKGROUND

During adrenergic stress, the influence of age on left atrial (LA) function is unknown. We hypothesized that aging decreases LA total emptying fraction (LAEF) during maximal adrenergic stress. The aim of the study was to determine the influence of aging on LA function during adrenergic stress in middle aged and older patients.

METHODS

We enrolled 167 middle aged and elderly participants, and measured LA and left ventricular (LV) volumes using a multi-slice three-dimensional cine white blood cardiovascular magnetic resonance (CMR) technique before and during intravenous dobutamine infused to achieve 80% of the maximum heart rate response for age. Paired sample t-test was used to detect differences in LA and LV volumes between baseline and peak dose stage of dobutamine stress CMR, and multivariable linear regression was used to identify predictors of LA function.

RESULTS

Participants averaged 68 ± 8 years in age, 53% were men, 25% exhibited coronary artery disease, 35% had diabetes, 9% had a remote history of atrial fibrillation, 90% had hypertension, and 11% had inducible LV wall motion abnormalities indicative of ischemia during dobutamine CMR. Increasing age correlated with LA volumes (maximal and minimal) and inversely correlated with LAEF at rest and after peak adrenergic stress. Age was an independent predictor of LAEF during adrenergic stress, even after accounting for gender, LV volumes, and other co-morbidities including inducible ischemia.

CONCLUSIONS

Age is associated with a decrease in LA function during adrenergic stress even after adjusting for co-morbidities associated with cardiovascular disease and LV function.

Early-onset growth hormone deficiency results in diastolic dysfunction in adult-life and is prevented by growth hormone supplementation

OBJECTIVE

The primary goal of growth hormone (GH) replacement is to promote linear growth in children with growth hormone deficiency (GHD). GH and insulin-like growth factor-1 (IGF-1) are also known to have roles in cardiac development and as modulators of myocardial structure and function in the adult heart. However, little is known about cardiac diastolic function in young adults with childhood onset GH deficiency in which GH treatment was discontinued following puberty. The aim of the study was to evaluate the effects of long standing GHD and peri-pubertal or continuous GH replacement therapy on diastolic function in the adult dwarf rat.

DESIGN

The dwarf rat, which possesses a mutation in a transcription factor necessary for development of the somatotroph, does not exhibit the normal peri-pubertal rise in GH around day 28 and was used to model childhood or early-onset GHD (EOGHD). In another group of male dwarfs, GH replacement therapy was initiated at 4 weeks of age when GH pulsatility normally begins. Ten weeks after initiation of injections, GH-treated dwarf rats were divided into 2 groups; continued treatment with GH for 12 weeks (GH-replete) or treatment with saline for 12 weeks. This latter group models GH supplementation during adolescence with GHD beginning in adulthood (adult-onset GHD; AOGHD). Saline-treated heterozygous (HZ) rats were used as age-matched controls. At 26 weeks of age, cardiac function was assessed using invasive or noninvasive (conventional and tissue Doppler) indices of myocardial contractility and lusitropy.

RESULTS

Systolic function, as determined by echocardiography, was similar among groups. Compared with HZ rats and GH-replete dwarfs, the EOGHD group exhibited significant reductions in myocardial relaxation and increases in left ventricular filling pressure, indicative of moderate diastolic dysfunction. This was further associated with a decrease in the cardiac content of sarcoplasmic reticulum Ca(2+) ATPase (SERCA2), one of the important cardiac calcium regulatory proteins. Dwarfs supplemented with GH during the peri-adolescence stage, but not beyond (AOGHD), exhibited a subtle prolongation in the deceleration time to early filling. In contrast, continual GH replacement preserved diastolic function such that the cardiac phenotype of the GH-replete dwarfs resembled that of their age-matched HZ counterpart.

DISCUSSION

Our data indicate that GHD during adolescence leads to overt diastolic dysfunction in early adulthood and this is prevented by continual GH replacement therapy. Since discontinuation of GH replacement following adolescence only mitigated the lusitropic deficits that were observed in untreated dwarfs, GH treatment into adulthood could be beneficial.

Contribution of comorbidities to functional impairment is higher in heart failure with preserved than with reduced ejection fraction

BACKGROUND

Comorbidities negatively affect prognosis more strongly in heart failure with preserved (HFpEF) than with reduced (HFrEF) ejection fraction. Their comparative impact on physical impairment in HFpEF and HFrEF has not been evaluated so far.

METHODS AND RESULTS

The frequency of 12 comorbidities and their impact on NYHA class and SF-36 physical functioning score (SF-36 PF) were evaluated in 1,294 patients with HFpEF and 2,785 with HFrEF. HFpEF patients had lower NYHA class (2.0 ± 0.6 vs. 2.4 ± 0.6, p < 0.001) and higher SF-36 PF score (54.4 ± 28.3 vs. 54.4 ± 27.7, p < 0.001). All comorbidities were significantly (p < 0.05) more frequent in HFrEF, except hypertension and obesity, which were more frequent in HFpEF (p < 0.001). Adjusting for age and gender, COPD, anemia, hyperuricemia, atrial fibrillation, renal dysfunction, cerebrovascular disease and diabetes had a similar (p for interaction > 0.05) negative effect in both groups. Obesity, coronary artery disease and peripheral arterial occlusive disease exerted a significantly (p < 0.05) more adverse effect in HFpEF, while hypertension and hyperlipidemia were associated with fewer (p < 0.05) symptoms in HFrEF only. The total impact of comorbidities on NYHA (AUC for prediction of NYHA III/IV vs. I/II) and SF-36 PF (r(2)) in multivariate analyses was approximately 1.5-fold higher in HFpEF, and also much stronger than the impact of a 10% decrease in ejection fraction in HFrEF or a 5 mm decrease in left ventricular end-diastolic diameter in HFpEF.

CONCLUSION

The impact of comorbidities on physical impairment is higher in HFpEF than in HFrEF. This should be considered in the differential diagnosis and in the treatment of patients with HFpEF.

Neuromuscular electrical stimulation improves GLUT-4 and morphological characteristics of skeletal muscle in rats with heart failure

AIM

Changes in skeletal muscle morphology and metabolism are associated with limited functional capacity in heart failure, which can be attenuated by neuromuscular electrical stimulation (ES). The purpose of the present study was to analyse the effects of ES upon GLUT-4 protein content, fibre structure and vessel density of the skeletal muscle in a rat model of HF subsequent to myocardial infarction.

METHODS

Forty-four male Wistar rats were assigned to one of four groups: sham (S), sham submitted to ES (S+ES), heart failure (HF) and heart failure submitted to ES (HF+ES). The rats in the ES groups were submitted to ES of the left leg during 20 days (2.5 kHz, once a day, 30 min, duty cycle 50%- 15 s contraction/15 s rest). After this period, the left tibialis anterior muscle was collected from all the rats for analysis.

RESULTS

HF+ES rats showed lower values of lung congestion when compared with HF rats (P = 0.0001). Although muscle weight was lower in HF rats than in the S group, thus indicating hypotrophy, 20 days of ES led to their recovery (P < 0.0001). In both groups submitted to ES, there was an increase in muscle vessel density (P < 0.04). Additionally, heart failure determined a 49% reduction in GLUT-4 protein content (P < 0.03), which was recovered by ES (P < 0.01).

CONCLUSION

In heart failure, ES improves morphological changes and raises GLUT-4 content in skeletal muscle.

Decreased cardiac functional reserve in heart failure with preserved systolic function

BACKGROUND

Heart failure in patients with preserved left ventricular systolic function (HFpEF) is a prevalent disease characterized by exercise intolerance with poorly understood pathophysiology. We hypothesized that recruitable contractility is impaired in HFpEF, accounting for the appearance of symptoms with exertion.

METHODS AND RESULTS

Echocardiographic analysis of myocardial performance was performed at baseline and after a modified dobutamine protocol (max dose 16 μg/kg/min) in participants with known HFpEF and age- and gender-matched controls. The primary outcome variable was change in contractile reserve, measured as a change in ejection fraction (EF). Recruitable contractility was decreased in HFpEF participants compared with control subjects (HFpEF 0.4 ± 1.9% vs control 19.0 ± 1.4%; P < .001). During dobutamine infusion, velocities increased in control participants but remained unchanged in the HFpEF group, yielding a significant difference between groups (P < .05) for both longitudinal displacement and velocity.

CONCLUSIONS

Patients with HFpEF have an impaired contractile response to adrenergic stimulation. The blunted response to adrenergic stimulation in the HFpEF group suggests that these patients may be unable to respond to periods of increased cardiac demand. This inability to increase contractility appropriately suggests abnormalities of systolic function in this disease and may contribute to exertional intolerance in HFpEF.

Global cardiovascular reserve dysfunction in heart failure with preserved ejection fraction

OBJECTIVES

The purpose of this study was to comprehensively examine cardiovascular reserve function with exercise in patients with heart failure and preserved ejection fraction (HFpEF).

BACKGROUND

Optimal exercise performance requires an integrated physiologic response, with coordinated increases in heart rate, contractility, lusitropy, arterial vasodilation, endothelial function, and venous return. Cardiac and vascular responses are coupled, and abnormalities in several components may interact to promote exertional intolerance in HFpEF.

METHODS

Subjects with HFpEF (n = 21), hypertension without heart failure (n = 19), and no cardiovascular disease (control, n = 10) were studied before and during exercise with characterization of cardiovascular reserve function by Doppler echocardiography, peripheral arterial tonometry, and gas exchange.

RESULTS

Exercise capacity and tolerance were reduced in HFpEF compared with hypertensive subjects and controls, with lower VO(2) and cardiac index at peak, and more severe dyspnea and fatigue at matched low-level workloads. Endothelial function was impaired in HFpEF and in hypertensive subjects as compared with controls. However, blunted exercise-induced increases in chronotropy, contractility, and vasodilation were unique to HFpEF and resulted in impaired dynamic ventricular-arterial coupling responses during exercise. Exercise capacity and symptoms of exertional intolerance were correlated with abnormalities in each component of cardiovascular reserve function, and HFpEF subjects were more likely to display multiple abnormalities in reserve.

CONCLUSIONS

HFpEF is characterized by depressed reserve capacity involving multiple domains of cardiovascular function, which contribute in an integrated fashion to produce exercise limitation. Appreciation of the global nature of reserve dysfunction in HFpEF will better inform optimal design for future diagnostic and therapeutic strategies.

Heart rate autonomic responses during deep breathing and walking in hospitalised patients with chronic heart failure

OBJECTIVE

To evaluate the acute effect of physiotherapy (deep breathing exercises and walking) on heart rate variability in patients hospitalised with chronic heart failure (CHF).

DESIGN

Ten males with CHF (57 ± 7 years) and 10 healthy controls (59 ± 9 years) were included. Heart rate and RR intervals were recorded in the following conditions: supine, seated, during deep breathing exercises and during and after walking. Heart rate variability was analysed by linear and non-linear methods (α2, Mean HR, rMSSD, SDNN and ApEn).

RESULTS

Patients presented significantly lower SDNN (12.4 ± 4 versus 26 ± 8 ms), rMSSD (18.2 ± 16.2 versus 25 ± 19.5 ms) and ApEn (9.9 ± 10 versus 16.68 ± 22.6) during the walking compared to controls (p < 0.05). In addition, mean HR was significantly higher during and after walking for patients with CHF compared to controls (103 ± 8 versus 80 ± 2 bpm and 90 ± 9 versus 68 ± 2 bpm, respectively). Patients with CHF demonstrated a significant reduction of α2 during deep breathing (0.78 ± 0.1) when compared to the seated position (1.08 ± 0.1) and walking (1.15 ± 0.2, p < 0.05). Additionally, rMSSD index increased during deep breathing when compared to walking in both groups.

CONCLUSION

Deep breathing exercises and walking are safe and promote beneficial effects on heart rate variability in patients hospitalised for CHF.

Chronic alternate-day fasting results in reduced diastolic compliance and diminished systolic reserve in rats

BACKGROUND

Based on animal experiments and limited data from the few human trials, alternate-day fasting (ADF) resulted in weight loss, prolonged life, reduced metabolic risk factors for diabetes and cardiovascular diseases, and reduced prevalence of age-related diseases. The present study is the first comprehensive examination of the long-term effects of ADF on general cardiovascular fitness in rats.

METHODS AND RESULTS

Four-month-old male Sprague-Dawley rats were started on ADF or continued on ad libitum diets and followed for 6 months with serial echocardiography. A comprehensive hemodynamic evaluation including a combined dobutamine-volume stress test was performed at the end of the study, and hearts were harvested for histological assessment. The 6-month-long ADF diet resulted in a 9% reduction (P < .01) of cardiomyocyte diameter and 3-fold increase in interstitial myocardial fibrosis. Left ventricular chamber size was not affected by ADF and ejection fraction was not reduced, but left atrial diameter was increased 16%, and the ratio of early (E) and late atrial (A) waves, in Doppler-measured mitral flow was reduced (P < .01). Pressure-volume loop analyses revealed a "stiff" heart during diastole in ADF rats, whereas combined dobutamine and volume loading showed a significant reduction in left ventricular diastolic compliance and a lack of increase in systolic pump function, indicating a diminished cardiac reserve.

CONCLUSION

Chronic ADF in rats results in development of diastolic dysfunction with diminished cardiac reserve. ADF is a novel and unique experimental model of diet-induced diastolic dysfunction. The deleterious effect of ADF in rats suggests that additional studies of ADF effects on cardiovascular functions in humans are warranted.

Effect of Beta-blocker therapy on rehospitalization rates in women versus men with heart failure and preserved ejection fraction

Beta blockers are empirically used in many patients with heart failure (HF) and preserved ejection fraction (HFpEF) because they allow more time for diastolic filling and because they improve outcomes in patients with systolic HF. However, recent data suggest that impaired chronotropic and vasodilator responses to exercise, which can worsen with beta blockade, may play a key role in the pathophysiology of HFpEF. We prospectively examined the association between beta-blocker therapy after hospitalization for decompensated HF and HF rehospitalization at 6 months in 66 consecutive patients with HFpEF (71 +/- 13 years old, 68% women, 42% Black). Subjects were stratified based on receiving (BB+; 15 men, 28 women) or not receiving (BB-) beta-blockers at hospital discharge. In men, HF rehospitalization occurred less frequently in the BB+ than in the BB- group, albeit nonsignificantly (20% vs 50%, p = 0.29). In women, HF rehospitalization occurred more frequently in the BB+ than in the BB- group (75% vs 18%, p <0.001). In univariate analyses, discharge beta-blocker was associated with HF rehospitalization in women (odds ratio [OR] 14.00, 95% confidence interval [CI] 3.09 to 63.51, p = 0.001), but not in men (OR 0.25, 95% CI 0.03 to 1.92, p = 0.18). In a forward logistic regression model that offered all univariate predictors of HF rehospitalization, discharge beta blocker remained an independent predictor of HF rehospitalization in women (OR 11.06, 95% CI 1.98 to 61.67, p = 0.006). In conclusion, this small observational study suggests that beta-blocker therapy may be associated with a higher risk of HF rehospitalization in women with HFpEF. The risks and benefits of beta-blocker therapy in patients with HFpEF should be evaluated in randomized, controlled trials.

Diastolic dysfunction, cardiovascular aging, and the anesthesiologist

As the number of persons aged 65 years and older continues to increase, the anesthesiologist will more frequently encounter this demographic. Cardiovascular changes that occur in this patient population present difficult anesthetic challenges and place these patients at high risk of perioperative morbidity and mortality. The anesthesiologist should be knowledgeable about these age-related cardiovascular changes, the pathophysiology underlying them, and the appropriate perioperative management. Whether presenting for cardiac or general surgery, the anesthesiologist must identify patients with altered physiology as a result of aging or diastolic dysfunction and be prepared to modify the care plan accordingly. With a directed preoperative assessment that focuses on certain aspects of the cardiovascular system, and the assistance of powerful echocardiographic tools such as tissue Doppler, this can be achieved.

Relationship of Doppler-Echocardiographic left ventricular diastolic function to exercise performance in systolic heart failure: the HF-ACTION study

INTRODUCTION

Patients with systolic heart failure often have concomitant left ventricular (LV) diastolic dysfunction. Although in animal models diastolic dysfunction is associated with worsening exercise capacity and prognosis, information regarding these relationships in patients with established systolic heart failure (HF) is sparse.

METHODS

HF-ACTION was a large, multicenter National Institutes of Health-funded trial of exercise training in systolic HF (LV ejection fraction [LVEF] < or = 35%) and included detailed Doppler-echocardiographic (echo) and cardiopulmonary exercise testing at baseline. We tested the hypothesis that echo measures of LV diastolic function predict key cardiopulmonary exercise outcomes, including aerobic exercise capacity (peak exercise oxygen consumption, VO(2)), distance in the 6-minute walk test (6MWD), and ventilatory efficiency (VE/VCO(2) slope) in patients with systolic HF.

RESULTS

Overall, 2,331 patients (28% women, median age 59 years, median LVEF 25%) were enrolled. There were significant bivariate correlations between echo diastolic function variables and peak VO(2) (inverse) and VE/VCO(2) slope (direct) that were strongest for ratio of early diastolic peak transmitral (MV) to myocardial tissue velocity (E/E'), peak MV early-to-late diastolic velocity ratio (E/A), and left atrial dimension (range of absolute r = 0.16-0.28). Both MV E/A and E/E' were more strongly related to all 3 exercise variables than was LVEF. The relationships of E/A and E/E' with 6MWD were weaker than with peak VO(2) or VE/VCO(2) slope. A multivariable model with peak VO(2) as the dependent variable, which included MV E/A and 9 demographic predictors including age, sex, race, body mass index, and New York Heart Association class, explained 40% of the variation in peak VO(2), with MV E/A explaining 6% of the variation. Including LVEF in the model explained less than an additional 1% of the variance in peak VO(2). In a multivariable model for VE/VCO(2) slope, MV E/A was the strongest independent echo predictor, explaining 10% of the variance. The relationship of LV diastolic function variables with 6MWD was weaker than with peak VO(2) or VE/VCO(2) slope.

CONCLUSION

In patients with systolic HF, LV early diastolic function is a modest independent predictor of aerobic exercise capacity and appears to be a better predictor than LVEF.

Relationship of age and exercise performance in patients with heart failure: the HF-ACTION study

BACKGROUND

More than three fourths of patients with heart failure (HF) are 65 years and older, and older age is associated with worse symptoms and prognoses than is younger age. Reduced exercise capacity is a chief HF complaint and indicates poorer prognosis, especially among elderly persons, but the mechanisms underlying functional decline in older patients with HF are largely unknown.

METHODS

Baseline cardiopulmonary exercise testing data from the HF-ACTION trial were assessed to clarify age effects on peak oxygen consumption (VO(2)) and ventilation-carbon dioxide production (VE/VCO(2)) slope.

RESULTS

Among 2,331 New York Heart Association class II-IV patients with HF, increased age corresponded to decreased peak VO(2) (-0.14 mL kg(-1) min(-1) per year >40 years; P < .0001) and increased VE/VCO(2) slope (0.30 U/y >70 years; P < .0001). In a multivariable model with 34 other potential determinants, age was the strongest independent predictor of peak VO(2) (partial R(2) 0.130, total R(2) 0.392; P < .001) and a significant but relatively weaker predictor of VE/VCO(2) slope (partial R(2) 0.037, total R(2) 0.199; P < .001). Blunted peak heart rate was also a strong predictor of peak VO(2). Although peak heart rate and age were strongly correlated, both were significant independent predictors of peak VO(2) when analyzed simultaneously in a model. Aggregate comorbidity increased significantly with age but did not account for age effects on peak VO(2).

CONCLUSIONS

Age is the strongest predictor of peak VO(2) and a significant predictor of VE/VCO(2) slope in the HF-ACTION population. Age-dependent comorbidities do not explain changes in peak VO(2). Age-related changes in cardiovascular physiology, potentially magnified by the HF disease state, should be considered a contributor to the pathophysiology and a target for more effective therapy in older patients with HF.