Skeletal muscle function and its relation to exercise tolerance in chronic heart failure

Isolated quadriceps training increases maximal exercise capacity in chronic heart failure: the role of skeletal muscle convective and diffusive oxygen transport

OBJECTIVES

This study sought to elucidate the mechanisms responsible for the benefits of small muscle mass exercise training in patients with chronic heart failure (CHF).

BACKGROUND

How central cardiorespiratory and/or peripheral skeletal muscle factors are altered with small muscle mass training in CHF is unknown.

METHODS

We studied muscle structure, and oxygen (O(2)) transport and metabolism at maximal cycle (whole-body) and knee-extensor exercise (KE) (small muscle mass) in 6 healthy controls and 6 patients with CHF who then performed 8 weeks of KE training (both legs, separately) and repeated these assessments.

RESULTS

Pre-training cycling and KE peak leg O(2) uptake (Vo(2peak)) were ~17% and ~15% lower, respectively, in the patients compared with controls. Structurally, KE training increased quadriceps muscle capillarity and mitochondrial density by ~21% and ~25%, respectively. Functionally, despite not altering maximal cardiac output, KE training increased maximal O(2) delivery (~54%), arterial-venous O(2) difference (~10%), and muscle O(2) diffusive conductance (D(M)O(2)) (~39%) (assessed during KE), thereby increasing single-leg Vo(2peak) by ~53%, to a level exceeding that of the untrained controls. Post-training, during maximal cycling, O(2) delivery (~40%), arterial-venous O(2) difference (~15%), and D(M)O(2) (~52%) all increased, yielding an increase in Vo(2peak) of ~40%, matching the controls.

CONCLUSIONS

In the face of continued central limitations, clear improvements in muscle structure, peripheral convective and diffusive O(2) transport, and subsequently, O(2) utilization support the efficacy of local skeletal muscle training as a powerful approach to combat exercise intolerance in CHF.

Age-associated disruption of molecular clock expression in skeletal muscle of the spontaneously hypertensive rat

It is well known that spontaneously hypertensive rats (SHR) develop muscle pathologies with hypertension and heart failure, though the mechanism remains poorly understood. Woon et al. (2007) linked the circadian clock gene Bmal1 to hypertension and metabolic dysfunction in the SHR. Building on these findings, we compared the expression pattern of several core-clock genes in the gastrocnemius muscle of aged SHR (80 weeks; overt heart failure) compared to aged-matched control WKY strain. Heart failure was associated with marked effects on the expression of Bmal1, Clock and Rora in addition to several non-circadian genes important in regulating skeletal muscle phenotype including Mck, Ttn and Mef2c. We next performed circadian time-course collections at a young age (8 weeks; pre-hypertensive) and adult age (22 weeks; hypertensive) to determine if clock gene expression was disrupted in gastrocnemius, heart and liver tissues prior to or after the rats became hypertensive. We found that hypertensive/hypertrophic SHR showed a dampening of peak Bmal1 and Rev-erb expression in the liver, and the clock-controlled gene Pgc1α in the gastrocnemius. In addition, the core-clock gene Clock and the muscle-specific, clock-controlled gene Myod1, no longer maintained a circadian pattern of expression in gastrocnemius from the hypertensive SHR. These findings provide a framework to suggest a mechanism whereby chronic heart failure leads to skeletal muscle pathologies; prolonged dysregulation of the molecular clock in skeletal muscle results in altered Clock, Pgc1α and Myod1 expression which in turn leads to the mis-regulation of target genes important for mechanical and metabolic function of skeletal muscle.

Arterial stiffening, wave reflection, and inflammation in habitually exercising systemic lupus erythematosus patients

BACKGROUND

Chronic systemic inflammation has been implicated in the pathogenesis of hypertension and cardiovascular disease. Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by chronic inflammation and an increased risk for cardiovascular disease. Currently few studies have evaluated the potential cardiovascular benefits of exercise in SLE. It is unknown whether the favorable effect of habitual exercise on arterial stiffness observed in healthy adults can be extended to SLE. Therefore, as an initial step, we determined the association between habitual exercise, inflammatory markers, central arterial compliance, and aortic wave reflection in healthy adults and SLE patients.

METHODS

We studied 41 adults, aged 33 ± 11 years (15 healthy controls, 12 sedentary SLE, and 14 physically active SLE patients).

RESULTS

Age, body mass index, and metabolic risk factors were not different between the three groups. Carotid arterial compliance was lower whereas augmentation index (AI) and inflammatory markers (C-reactive protein (CRP), interleukin (IL)-12, tumor necrosis factor-α (TNF-α)) were higher in sedentary SLE patients compared with healthy controls, but were not different between physically active SLE patients and healthy controls. Cardiac ejection fraction was lower in sedentary SLE than physically active SLE or healthy controls. In the pooled population, carotid arterial compliance was inversely associated with TNF-α (r = -0.38; P < 0.01), and AI was positively associated with both CRP (r = 0.33; P < 0.05) and intercellular adhesion molecule-1 (r = 0.28; P < 0.05).

CONCLUSIONS

SLE-associated stiffening of the central artery and wave reflection were not observed in habitually exercising adults with SLE. Furthermore, greater arterial stiffness was associated with higher inflammatory markers, suggesting that need for studies on inflammation and SLE-associated arterial stiffening.

The role of exercise training in heart failure

Exercise training in patients with systolic heart failure (HF) is an accepted adjunct to an evidence-based management program. This review describes the pathophysiologic features that are thought to be responsible for the exercise intolerance experienced in the HF patient. Significant research has expanded our appreciation of the interplay of hemodynamic, ventilatory, and skeletal myopathic processes in this common, chronic condition. Randomized, controlled exercise trials designed to measure endothelial function, inflammatory markers, sympathetic neural activation, and skeletal muscle metabolism and structure have further defined the pathophysiology, documented the impact of exercise training on these processes, and confirmed the benefit of this therapy. Consistent with prior clinical research and patient experience are the recently published results of the HF-ACTION (Heart Failure-A Controlled Trial Investigating Outcomes of exercise TraiNing), which demonstrated a modest improvement in exercise capacity, reduction of symptoms, and improved self-reported measures of quality of life without adverse events. Consideration is given in this review to the benefits of variable intensity programs and the addition of resistance exercise to a standard aerobic prescription. Despite increasing validation of the role exercise training plays in the modification of exercise intolerance, challenges remain in its routine therapeutic application, including acceptance and use as an adjunctive intervention in the management of the patient with HF, limited insurance coverage for HF patients in cardiac rehabilitation, tailoring of exercise programs to best address the needs of subgroups of patients, and improved short- and long-term adherence to exercise training and a physically active lifestyle.

Cardio-renal cachexia syndromes (CRCS): pathophysiological foundations of a vicious pathological circle

Cardio-renal syndromes (CRS) are defined as disorders of the heart and kidney whereby acute or chronic dysfunction in one organ may induce acute or chronic dysfunction of the other. CRS have been classified into five categories, where types 2 and 4 represent respectively chronic cardio-renal and chronic reno-cardiac syndromes. In these conditions, the chronic disorder of either the heart or kidney has been shown to induce some degree of cachexia. At the same time, cachexia has been proposed as a possible mechanism contributing to the worsening of such pathological organ cross talk. Common pathogenetic mechanisms underlie body wasting in cachectic states of different chronic heart and kidney diseases. In these circumstances, a vicious circle could arise, in which cachexia associated with either heart failure or chronic kidney disease may contribute to further damage of the other organ. In chronic CRS, activation of the immune and neuroendocrine systems contributes to the genesis of cachexia, which in turn can negatively affect the heart and kidney function. In patients with cardiac sustained activation of the immune and neuroendocrine systems and oxidative stress, renal vascular resistance can increase and therefore impair renal perfusion, leading to worsening kidney function. Similarly, in renal cachexia, increased levels of pro-inflammatory cytokines can cause progressive left ventricular systolic dysfunction, myocardial cell death, endothelial dysfunction and increased myocardial fibrosis, with consequent impairment of the chronic reno-cardiac syndrome type 4. Thus, we speculate that the occurrence of different types of chronic CRS could represent a fundamental step in the genesis of cachexia, being renal and cardiac dysfunction closely related to the occurrence of systemic disorders leading to a final common pathway. Therefore, the heart and kidney and cachexia represent a triad causing a vicious circle that increases mortality and morbidity: In such circumstances, we may plausibly talk about cardio-renal cachexia syndrome. Complex interrelations may explain the transition from CRS to cachexia and from cachexia to CRS. Identification of the exact mechanisms occurring in these conditions could potentially help in preventing and treating this deadly combination.

The effects of depression on the course of functional limitations in patients with chronic heart failure

BACKGROUND

This study examined whether depressive symptoms are associated with persistent functional limitations and severity classified according to the course of functional limitations in chronic heart failure (CHF) patients after discharge.

METHODS AND RESULTS

The Performance Measure for Activities of Daily Living 8 (PMADL-8) was used to measure the course of functional limitations at 1, 3, and 5 months after discharge in a cohort of 148 patients. Depressive symptoms were assessed using the Hospital Anxiety and Depression Scale at 1 month after discharge. Repeated-measures logistic regression adjusting for potential confounders demonstrated that the depression groups had different persistent functional limitations (PMADL-8 scores ≥20 at 1, 3, and 5 months after discharge [χ(2) = 5.3; P < .05]). Using cluster analysis, we identified 4 distinctive courses of functional limitations, and there was a graded relationship between the severity of the course and depressive symptoms (χ(2) = 26.1; P < .001).

CONCLUSIONS

In this prospective study, depression was associated with poorer functional limitations in CHF patients after discharge. The findings of this study suggest that depression may be a treatment target for improving functional limitations in CHF patients during the recovery phase.

Beyond atrophy: redox mechanisms of muscle dysfunction in chronic inflammatory disease

Chronic inflammatory diseases such as heart failure, cancer and arthritis have secondary effects on skeletal muscle that cause weakness and exercise intolerance. These symptoms exacerbate illness and make death more likely. Weakness is not simply a matter of muscle atrophy. Functional studies show that contractile dysfunction, i.e. a reduction in specific force, makes an equally important contribution to overall weakness. The most clearly defined mediator of contractile dysfunction is tumour necrosis factor (TNF). TNF serum levels are elevated in chronic disease, correlate with muscle weakness, and are a predictor of morbidity and mortality. Research is beginning to unravel the mechanism by which TNF depresses specific force. TNF acts via the TNFR1 receptor subtype to depress force by increasing cytosolic oxidant activity. Oxidants depress myofibrillar function, decreasing specific force without altering calcium regulation or other aspects of myofibrillar mechanics. Beyond these concepts, the intracellular mechanisms that depress specific force remain undefined. We do not know the pathway by which receptor-ligand interaction stimulates oxidant production. Nor do we know the type(s) of oxidants stimulated by TNF, their intracellular source(s), or their molecular targets. Investigators in the field are pursuing these issues with the long-term goal of preserving muscle function in individuals afflicted by chronic disease.

Chronic heart failure decreases cross-bridge kinetics in single skeletal muscle fibres from humans

Skeletal muscle function is impaired in heart failure patients due, in part, to loss of myofibrillar protein content, in particular myosin. In the present study, we utilized small-amplitude sinusoidal analysis for the first time in single human skeletal muscle fibres to measure muscle mechanics, including cross-bridge kinetics, to determine if heart failure further impairs contractile performance by altering myofibrillar protein function. Patients with chronic heart failure (n = 9) and controls (n = 6) were recruited of similar age and physical activity to diminish the potentially confounding effects of ageing and muscle disuse. Patients showed decreased cross-bridge kinetics in myosin heavy chain (MHC) I and IIA fibres, partially due to increased myosin attachment time (t(on)). The increased t(on) compensated for myosin protein loss previously found in heart failure patients by increasing the fraction of the total cycle time myosin is bound to actin, resulting in a similar number of strongly bound cross-bridges in patients and controls. Accordingly, isometric tension did not differ between patients and controls in MHC I or IIA fibres. Patients also had decreased calcium sensitivity in MHC IIA fibres and alterations in the viscoelastic properties of the lattice structure of MHC I and IIA fibres. Collectively, these results show that heart failure alters skeletal muscle contraction at the level of the myosin-actin cross-bridge, leading to changes in muscle mechanics which could contribute to impaired muscle function. Additionally, we uncovered a unique kinetic property of MHC I fibres, a potential indication of two distinct populations of cross-bridges, which may have important physiological consequences.

Impaired muscle protein anabolic response to insulin and amino acids in heart failure patients: relationship with markers of immune activation

Patients with chronic HF (heart failure) experience muscle atrophy during the course of the disease. The mechanisms underlying muscle atrophy in HF, however, are not understood. Thus we evaluated leg phenylalanine balance and kinetics in HF patients and controls following a brief fast (24 h) and under euglycaemic-hyperinsulinaemic-hyperaminoacidaemic conditions to determine whether HF increases muscle protein catabolism in response to nutritional deprivation and/or diminishes the anabolic response to meal-related stimuli (insulin and amino acids) and whether alterations in protein metabolism correlate to circulating cytokine levels. No differences in phenylalanine balance, rate of appearance or rate of disappearance were found between patients and controls under fasting conditions. However, the anabolic response to hyperinsulinaemia-hyperaminoacidaemia was reduced by more than 50% in patients compared with controls. The diminished anabolic response was due to reduced suppression of the leg phenylalanine appearance rate, an index of protein breakdown, in HF patients; whereas no group difference was found in the increase in the leg phenylalanine disappearance rate, an index of protein synthesis. The diminished responses of both phenylalanine balance and appearance rate to hyperinsulinaemia-hyperaminoacidaemia were related to greater circulating IL-6 (interleukin-6) levels. Our results suggest that, following a brief period of nutritional deprivation, HF patients demonstrate an impaired muscle protein anabolic response to meal-related stimuli, due to an inability to suppress muscle proteolysis, and that this diminished protein anabolic response correlates with markers of immune activation. The inability to stimulate muscle protein anabolism following periods of nutritional deficiency may contribute to muscle wasting in HF patients.

Myocyte vascular endothelial growth factor is required for exercise-induced skeletal muscle angiogenesis

We have previously shown, using a Cre-LoxP strategy, that vascular endothelial growth factor (VEGF) is required for the development and maintenance of skeletal muscle capillarity in sedentary adult mice. To determine whether VEGF expression is required for skeletal muscle capillary adaptation to exercise training, gastrocnemius muscle capillarity was measured in myocyte-specific VEGF gene-deleted (mVEGF(-/-)) and wild-type (WT) littermate mice following 6 wk of treadmill running (1 h/day, 5 days/wk) at the same running speed. The effect of training on metabolic enzyme activity levels and whole body running performance was also evaluated in mVEGF(-/-) and WT mice. Posttraining capillary density was significantly increased by 59% (P < 0.05) in the deep muscle region of the gastrocnemius in WT mice but did not change in mVEGF(-/-) mice. Maximal running speed and time to exhaustion during submaximal running increased by 20 and 13% (P < 0.05), respectively, in WT mice after training but were unchanged in mVEGF(-/-) mice. Training led to increases in skeletal muscle citrate synthase (CS) and phosphofructokinase (PFK) activities in both WT and mVEGF(-/-) mice (P < 0.05), whereas β-hydroxyacyl-CoA dehydrogenase (β-HAD) activity was increased only in WT mice. These data demonstrate that skeletal muscle capillary adaptation to physical training does not occur in the absence of myocyte-expressed VEGF. However, skeletal muscle metabolic adaptation to exercise training takes place independent of myocyte VEGF expression.

Generic, symptom based, exercise rehabilitation; integrating patients with COPD and heart failure

BACKGROUND

Patients with Chronic Heart Failure (CHF) develop similar symptoms of exertional breathlessness and fatigue as patients with COPD. Although pulmonary (exercise based) rehabilitation (PR) is an integral part of the management of COPD, the potential for exercise rehabilitation (ER) to assist patients with CHF may not be as readily appreciated. We investigated whether combined ER for patients with CHF and COPD was feasible and effective using the model of PR.

METHODS

57 patients with CHF were randomized 2:1 to 7 weeks ER (CHF-ER) or 7 weeks of usual care (CHF-UC). As a comparator 55 patients with COPD were simultaneously recruited to the same ER program (COPD-ER). The primary outcome measure was the Incremental Shuttle Walk Test (ISWT) and the secondary outcome measures were the Endurance Shuttle Walk Test (ESWT), isometric quadriceps strength and health status.

RESULTS

27 CHF and 44 COPD patients completed ER and 17 patients with CHF completed UC. The CHF-ER group made significant improvements, compared to CHF-UC, in the mean (95%CI) ISWT distance; 62(35-89)m vs -6(-11 to 33)m p < 0.001. The CHF-ER group also made statistically significant improvements in health status. The improvements in exercise performance and health status were similar between patients with CHF and COPD, treated with ER.

CONCLUSION

Patients with CHF who undergo ER improve similarly in their exercise performance and health status to COPD. Combined training programs for COPD and CHF are effective and feasible, such that service provision could be targeted around common disability rather than the primary organ disease.

Fixing ryanodine receptor Ca leak - a novel therapeutic strategy for contractile failure in heart and skeletal muscle

A critical component in regulating cardiac and skeletal muscle contractility is the release of Ca(2+) via ryanodine receptor (RyR) Ca(2+) release channels in the sarcoplasmic reticulum (SR). In heart failure and myopathy, the RyR has been found to be excessively phosphorylated or nitrosylated and depleted of the RyR-stabilizing protein calstabin (FK506 binding protein 12/12.6). This remodeling of the RyR channel complex results in an intracellular SR Ca(2+) leak and impaired contractility. Despite recent advances in heart failure treatment, there are still devastatingly high mortality rates with this disease. Moreover, pharmacological treatment for muscle weakness and myopathy is nearly nonexistent. A novel class of RyR-stabilizing drugs, rycals, which reduce Ca(2+) leak by stabilizing the RyR channels due to preservation of the RyR-calstabin interaction, have recently been shown to improve contractile function in both heart and skeletal muscle. This opens up a novel therapeutic strategy for the treatment of contractile failure in the cardiac and skeletal muscle.

Limited maximal exercise capacity in patients with chronic heart failure: partitioning the contributors

OBJECTIVES

This study aimed to assess the factors limiting maximal exercise capacity in patients with chronic heart failure (CHF).

BACKGROUND

Maximal exercise capacity, an important index of health in CHF, might be limited by central and/or peripheral factors; however, their contributions remain poorly understood.

METHODS

We studied oxygen (O2) transport and metabolism at maximal cycle (centrally taxing) and knee-extensor (KE) (peripherally taxing) exercise in 12 patients with CHF and 8 healthy control subjects in normoxia and hyperoxia (100% O2).

RESULTS

Peak oxygen uptake (VO2) while cycling was 33% lower in CHF patients than in control subjects. By experimental design, peak cardiac output was reduced during KE exercise when compared with cycling (approximately 35%); although muscle mass specific peak leg VO2 was increased equally in both groups (approximately 70%), VO2 in the CHF patients was still 28% lower. Hyperoxia increased O2 carriage in all cases but only facilitated a 7% increase in peak leg VO2 in the CHF patients during cycling, the most likely scenario to benefit from increased O2 delivery. Several relationships, peak leg VO2 (KE + cycle) to capillary-fiber-ratio and capillaries around a fiber to mitochondrial volume, were similar in both groups (r = 0.6-0.7).

CONCLUSIONS

Multiple independent observations, including a significant skeletal muscle metabolic reserve, suggest skeletal muscle per se contributes minimally to limiting maximal cycle exercise in CHF or healthy control subjects. However, the consistent attenuation of the convective and diffusive components of O2 transport (25% to 30%) in patients with CHF during both cycle and even KE exercise compared with control subjects reveals an underlying peripheral O2 transport limitation from blood to skeletal muscle in this pathology.

The skeletal muscle VEGF mRNA response to acute exercise in patients with chronic heart failure

In seven patients with chronic heart failure (CHF) and six controls, we examined (a) resting and post-exercise muscle vascular endothelial growth factor (VEGF) mRNA levels and (b) their relationship with muscle structure and function. Muscle biopsies were taken after 30 min of single-leg knee-extensor exercise at 50% of maximum work rate (50% WR(max)) from both the exercised and rested legs. Muscle blood flow (.Q) and O(2) uptake .VO(2) were measured during exercise. Resting VEGF mRNA levels were not different between patients and controls and both groups upregulated VEGF mRNA equally in response to acute exercise. Patients had lower .Q, .VO(2), and mitochondrial density but similar capillarity and fiber area. These findings reveal a normal basal level of muscle VEGF mRNA, its appropriate upregulation in response to acute exercise and, despite increased vascular resistance during exercise, a normal skeletal muscle vascular structure in patients with CHF.

Rationale and design of Ferinject assessment in patients with IRon deficiency and chronic Heart Failure (FAIR-HF) study: a randomized, placebo-controlled study of intravenous iron supplementation in patients with and without anaemia

Aims

Iron deficiency (ID) and anaemia are common in patients with chronic heart failure (CHF). The presence of anaemia is associated with increased morbidity and mortality in CHF, and ID is a major reason for the development of anaemia. Preliminary studies using intravenous (i.v.) iron supplementation alone in patients with CHF and ID have shown improvements in symptom status. FAIR-HF (Clinical Trials.gov NCT00520780) was designed to determine the effect of i.v. iron repletion therapy using ferric carboxymaltose on self-reported patient global assessment (PGA) and New York Heart Association (NYHA) in patients with CHF and ID.

Methods and results

This is a multi-centre, randomized, double-blind, placebo-controlled study recruiting ambulatory patients with symptomatic CHF with LVEF ≤ 40% (NYHA II) or ≤45% (NYHA III), ID [ferritin <100 ng/mL or ferritin 100–300 ng/mL when transferrin saturation (TSAT) < 20%], and haemoglobin 9.5–13.5 g/dL. Patients were randomized in a 2:1 ratio to receive ferric carboxymaltose (Ferinject^®) 200 mg iron i.v. or saline i.v. weekly until iron repletion (correction phase), then monthly until Week 24 (maintenance phase). Primary endpoints are (i) self-reported PGA at Week 24 and (ii) NYHA class at Week 24, adjusted for baseline NYHA class.

Conclusion

This study will provide evidence on the efficacy and safety of iron repletion with ferric carboxymaltose in CHF patients with ID with and without anaemia.

Quantitative assessment of cardiorespiratory fitness, skeletal muscle function, and body composition in adults with primary malignant glioma

BACKGROUND

The study was undertaken to evaluate cardiorespiratory fitness, skeletal muscle function, and body composition of patients with newly diagnosed and untreated, postsurgical primary malignant glioma.

METHODS

By using a cross-sectional design, patients with clinically stable (10 +/- 7 days postsurgery) high-grade glioma (HGG; n = 25) or low-grade glioma (LGG; n = 10) were studied. Participants performed a cardiopulmonary exercise test (CPET) with expired gas analysis to assess cardiorespiratory fitness (peak oxygen consumption, VO2peak). Other physiological outcomes included skeletal muscle cross-sectional area (CSA; magnetic resonance imaging), isokinetic muscle strength (isokinetic dynamometer), and body composition (air displacement plethysmography). Quality of life was assessed with the Functional Assessment of Cancer Therapy-Brain scale.

RESULTS

CPET was a feasible and safe procedure to assess VO2peak, with no serious adverse events. VO2peak indexed to total body weight and lean body mass (LBM) for both groups was 13.0 mL x weight x min(-1) and 19 mL x LBM x min(-1), the equivalent to 59% and 38% below age- and sex-predicted normative values, respectively. Skeletal muscle strength and mid-thigh CSA were lower in HGG relative to LGG patients (83 vs 125 Nm, P = .025; 94 vs 119 cm2, P = .171, respectively). Skeletal muscle isokinetic strength, CSA, and body composition outcomes predicted VO2peak (r = -0.59 to 0.68, P < .05).

CONCLUSIONS

Postsurgical glioma patients have markedly reduced cardiorespiratory fitness, isokinetic strength, and CSA. Prospective studies are now required to determine whether such abnormalities influence treatment toxicity and clinical outcome as well as to test the effect of appropriately selected interventions to prevent and/or mitigate dysfunction.

Functional adiponectin resistance at the level of the skeletal muscle in mild to moderate chronic heart failure

BACKGROUND

Adiponectin is an antiinflammatory, insulin-sensitizing, and antiatherogenic adipocytokine that plays a fundamental role in energy homeostasis. In patients with chronic heart failure (CHF), high circulating adiponectin levels are associated with inverse outcome. Recently, adiponectin expression has been identified in human skeletal muscle fibers. We investigated the expression of adiponectin, the adiponectin receptors, and genes involved in the downstream lipid and glucose metabolism in the skeletal muscle of patients with CHF.

METHODS AND RESULTS

Muscle biopsies (vastus lateralis muscle) were obtained from 13 patients with CHF and 10 healthy subjects. mRNA transcript levels of adiponectin, adiponectin receptors (AdipoR1 and AdipoR2), and downstream adiponectin-related enzymes were quantified by real-time reverse transcriptase polymerase chain reaction. Adiponectin expression in the skeletal muscle of patients with CHF was 5-fold higher than in healthy subjects (P<0.001), whereas AdipoR1 was downregulated (P=0.005). In addition, the expression of the main genes involved in downstream pathway (peroxisome proliferator-activated receptor-alpha [PPAR-alpha] and both AMP-activated protein kinase-alpha1 and -alpha2 subunits) as well as their target genes in lipid (acyl-coenzyme A dehydrogenase C-14 to C-12 straight chain) and glucose metabolism (hexokinase-2) were significantly reduced in CHF. The strong positive correlation found between AdipoR1 and PPAR-alpha/AMP-activated protein kinase gene expression was confirmed in PPAR-alpha null mice, suggesting a cause-and-effect relationship. Immunohistochemical staining confirmed the presence of adiponectin in the skeletal muscle.

CONCLUSIONS

Despite increased adiponectin expression in the skeletal muscle, patients with CHF are characterized by downregulation of AdipoR1 that is most probably linked to deactivation of the PPAR-alpha/AMP-activated protein kinase pathway. These facts suggest functional adiponectin resistance at the level of the skeletal muscle in CHF.

Glutamine preserves skeletal muscle force during an inflammatory insult

The purpose of this study was to test the hypothesis that acute glutamine (GLN) supplementation can counteract skeletal muscle contractile dysfunction occurring in response to inflammation by elevating muscle heat shock protein (Hsp) expression and reducing inflammatory cytokines. Mice received 5 mg/kg lipopolysaccharide (LPS) concurrently with 1 g/kg GLN or vehicle treatments. Plantarflexor isometric force production was measured at 2 hours post-injection. Blood and gastrocnemius muscles were collected, and serum and muscle tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) and muscle Hsp70 and Hsp25 were quantified. Saline/LPS treatment was associated with a 33% reduction in maximal force and elevated serum TNF-alpha and IL-6. GLN completely prevented this force decrement with LPS. GLN was found to reduce muscle Hsp70 and IL-6, but only in the presence of LPS. GLN supplementation provides an effective, novel, clinically applicable means of preserving muscle force during acute inflammation. These data indicate that force preservation is not dependent on reductions in serum cytokines or muscle TNF-alpha, or elevated Hsp levels.

Determinants of ventilatory efficiency in heart failure: the role of right ventricular performance and pulmonary vascular tone

BACKGROUND

Ventilatory efficiency, right ventricular (RV) function, and secondary pulmonary hypertension are each prognostic indicators in patients with heart failure due to left ventricular systolic dysfunction, but the relationships among these variables have not been comprehensively investigated. In this study, we hypothesized that inefficient ventilation during exercise, as defined by an abnormally steep relationship between ventilation and carbon dioxide output (Ve/Vco(2) slope), may be a marker of secondary pulmonary hypertension and RV dysfunction in heart failure.

METHODS AND RESULTS

A cohort of patients with systolic heart failure (mean+/-SD age, 58+/-13 years; left ventricular ejection fraction, 0.27+/-0.05; peak oxygen uptake, 11.2+/-3.2 mL kg(-1) min(-1)) underwent incremental cardiopulmonary exercise testing with simultaneous hemodynamic monitoring and first-pass radionuclide ventriculography before and after 12 weeks of treatment with sildenafil, a selective pulmonary vasodilator, or placebo. Ve/Vco(2) slope was positively related to rest and exercise pulmonary vascular resistance (R=0.39 and R=0.60, respectively) and rest pulmonary capillary wedge pressure (R=0.49, P<0.005 for all) and weakly indirectly related to peak exercise RV ejection fraction (R=-0.29, P=0.03). Over the 12-week study period, Ve/Vco(2) slope fell 8+/-3% (P=0.02) with sildenafil and was unchanged with placebo. Changes in Ve/Vco(2) slope correlated with changes in exercise pulmonary vascular resistance (R=0.69, P<0.001) and rest and exercise RV ejection fraction (R=-0.58 and -0.40, respectively, both P<0.05).

CONCLUSIONS

In patients with systolic heart failure and secondary pulmonary hypertension, ventilatory efficiency is closely related to RV function and pulmonary vascular tone during exercise.

Mechanisms underlying skeletal muscle weakness in human heart failure: alterations in single fiber myosin protein content and function

BACKGROUND

Patients with chronic heart failure (HF) frequently experience skeletal muscle weakness that limits physical function. The mechanisms underlying muscle weakness, however, have not been clearly defined.

METHODS AND RESULTS

This study examined the hypothesis that HF promotes a loss of myosin protein from single skeletal muscle fibers, which in turn reduces contractile performance. Ten patients with chronic HF and 10 controls were studied. Muscle atrophy was not evident in patients, and groups displayed similar physical activity levels, suggesting that observed differences reflect the effects of HF and not muscle atrophy or disuse. In single muscle fibers, patients with HF showed reduced myosin heavy chain protein content (P<0.05) that manifested as a reduction in functional myosin-actin cross-bridges (P<0.05). No evidence was found for a generalized loss of myofilament protein, suggesting a selective loss of myosin. Accordingly, single muscle fiber maximal Ca(2+)-activated tension was reduced in myosin heavy chain I fibers in patients (P<0.05). However, tension was maintained in myosin heavy chain IIA fibers in patients because a greater proportion of available myosin heads were bound to actin during Ca(2+) activation (P<0.01).

CONCLUSIONS

Collectively, our results show that HF alters the quantity and functionality of the myosin molecule in skeletal muscle, leading to reduced tension in myosin heavy chain I fibers. Loss of single fiber myosin protein content represents a potential molecular mechanism underlying muscle weakness and exercise limitation in patients with HF.

[Chronic obstructive pulmonary disease and heart failure]

Chronic obstructive pulmonary disease (COPD) is commonly associated with heart failure. Individuals with COPD have a 4.5-fold greater risk of developing heart failure than those without. The sensitivity and specificity of clinical judgment in the diagnosis of heart failure in patients with COPD can be enhanced by biological markers such as B-type natriuretic peptide and N-terminal pro-B-type natriuretic peptide. Correct interpretation of imaging results (mainly echocardiographic findings) and lung function tests can also help establish the co-occurrence of both conditions. There is little evidence on the management of patients with COPD and heart failure, although treatment of COPD undeniably affects the clinical course of patients with heart failure and viceversa.

[Chronic obstructive pulmonary disease and heart failure]

Chronic obstructive pulmonary disease (COPD) is commonly associated with heart failure. Individuals with COPD have a 4.5-fold greater risk of developing heart failure than those without. The sensitivity and specificity of clinical judgment in the diagnosis of heart failure in patients with COPD can be enhanced by biological markers such as B-type natriuretic peptide and N-terminal pro-B-type natriuretic peptide. Correct interpretation of imaging results (mainly echocardiographic findings) and lung function tests can also help establish the co-occurrence of both conditions. There is little evidence on the management of patients with COPD and heart failure, although treatment of COPD undeniably affects the clinical course of patients with heart failure and viceversa.

Comparison of skeletal muscle strength between cardiac patients and age-matched healthy controls

The purpose of the present study was to compare muscular strength of knee extensors and arm flexor muscles of cardiac patients (n = 638) and healthy controls (n = 961) in different age groups. Isometric torques were measured in a sitting position with the elbow, hip, and knee flexed to 90(0). For statistical analysis, age groups were pooled in decades from the age of 30 to 90 years. Additionally, the influence of physical lifestyle prior to disease on muscular strength was obtained in the patients. For statistical analysis three-way ANOVA (factors age, gender, and physical activity level) was used.Both in patients and in controls a significant age-dependent decline in maximal torque could be observed for arm flexors and knee extensors. Maximal leg extensor muscle showed statistically significant differences between healthy controls and cardiac patients as well as between subgroups of patients: Physically inactive patients showed lowest torques (male: 148 +/- 18 Nm; female: 82 +/- 25 Nm) while highest values were measured in control subjects (male: 167 +/- 16 Nm; female: 93 +/- 17 Nm). In contrast, arm flexor muscles did not show any significant influence of health status or sports history.This qualitative difference between weight-bearing leg muscles and the muscle group of the upper extremity suggest that lower skeletal muscle strength in heart patients is mainly a consequence of selective disuse of leg muscles rather than any pathological skeletal muscle metabolism. Since a certain level of skeletal muscle strength is a prerequisite to cope with everyday activities, strength training is recommended as an important part of cardiac rehabilitation.

The effect of short-term isometric muscle contraction and the Valsalva maneuver on systemic and pulmonary hemodynamics in patients with severe heart failure

BACKGROUND

Chronic heart failure is characterized by high mortality, frequent hospitalization, and reduced quality of life. Patients with severe heart failure are often in very poor physical condition, they are unable to take part in the usual exercise programs, and therefore need an individual approach.

HYPOTHESIS

To assess the systemic and pulmonary hemodynamic responses to maximum voluntary contraction of the lower extremity muscles (MVC-LEM) with persistent physiologic breathing, the Valsalva maneuver, and the combination of Valsalva with MVC-LEM.

METHODS

Seventeen patients with severe heart failure (ejection fraction 20%) were exposed to 3 types of load for a period of 10 seconds: 1) MVC-LEM with persistent physiologic breathing, 2) the Valsalva maneuver, and 3) a combination of MVC-LEM with the Valsalva maneuver. During each measurement, a continuous, time-synchronized record was taken of the electrocardiogram, and the pulmonary and systemic blood pressures.

RESULTS

There were slight changes in the heart rate and systemic blood pressure when comparing resting versus MVC-LEM values. There were much greater and significant changes (P < .01) in the systemic and pulmonary blood pressures when comparing resting versus the Valsalva maneuver or the combination of the MVC-LEM plus the Valsalva maneuver values.

CONCLUSIONS

A short maximum voluntary contraction of the muscles of the lower extremities with persistent physiologic breathing did not have an abnormal effect on the systemic and pulmonary hemodynamics in patients with severe chronic heart failure. The Valsalva maneuver caused significantly higher hemodynamic changes in the systemic and pulmonary system with possible negative effects.

Reduced knee extensor function in heart failure is not explained by inactivity

BACKGROUND

The goal of this study was to determine if heart failure alters knee extensor muscle torque, power production or contractile velocity.

METHODS

Heart failure patients (n=11; 70.4±4.3 yrs) and controls (n=11; 70.3±3.4 yrs) matched for age and sex were evaluated for knee extensor contractile performance under isometric and isokinetic conditions and body composition by dual energy X-ray absorptiometry. Additionally, we recruited sedentary to minimally active elderly controls to match heart failure patients for habitual physical activity and assessed activity levels using accelerometry.

RESULTS

Groups did not differ for total or regional body composition or average daily physical activity level. Despite similar muscle size and use, heart failure patients exhibited 21-29% lower (P<0.05 to P<0.01) isometric knee extensor torque throughout a range of knee angles, 15-33% lower (P=0.05 to P<0.01) peak concentric torque measured at various isokinetic speeds and corresponding reductions (P=0.05 to P<0.01) in peak power output. Expression of peak isokinetic torque data relative to isometric torque eliminated group differences, suggesting that impaired contractile function under dynamic conditions is explained by deficits in the force generating capacity of muscle. No group differences were found in the time required to reach target velocity during isokinetic contractions, an index of contractile velocity.

CONCLUSION

Because group differences in muscle torque were independent of age, sex, physical activity level and muscle size, our results suggest that muscle contractile dysfunction in these patients is likely attributable to the heart failure syndrome.

Eccentric exercise in patients with chronic health conditions: a systematic review

PURPOSE

The capacity of eccentric actions to produce muscle hypertrophy, strength gains, and neural adaptations without stressing the cardiopulmonary system has led to the prescription of eccentric training programmes in patients with low tolerance to exercise, such as elders or those with chronic health conditions. The purpose of this systematic review was to analyze the evidence regarding the effectiveness and suitability of eccentric training to restore musculoskeletal function in patients with chronic diseases.

SUMMARY OF KEY POINTS

Relevant articles were identified from nine databases and from the reference lists of key articles. Articles were assessed to determine level of evidence and scientific rigour. Nine studies met the inclusion criteria. According to Sackett's levels of evidence, 7 studies were graded at level IIb, 1 study at level IV, and the remaining study at level V. Articles were also graded for scientific rigour according to the PEDro scale. One study was rated as high quality, 4 studies were rated as moderate, and 2 studies were graded as poor quality.

CONCLUSIONS

Eccentric training may be safely used to restore musculoskeletal function in patients with some specific chronic conditions. However, the heterogeneity of diseases makes it very difficult to extrapolate results and to standardize clinical recommendations for adequate implementation of this type of exercise. More studies are needed to establish the potential advantages of eccentric training in chronic conditions.

Exercise training improves peripheral chemoreflex function in heart failure rabbits

An enhancement of peripheral chemoreflex sensitivity contributes to sympathetic hyperactivity in chronic heart failure (CHF) rabbits. The enhanced chemoreflex function in CHF involves augmented carotid body (CB) chemoreceptor activity via upregulation of the angiotensin II (ANG II) type 1 (AT(1))-receptor pathway and downregulation of the neuronal nitric oxide synthase (nNOS)-nitric oxide (NO) pathway in the CB. Here we investigated whether exercise training (EXT) normalizes the enhanced peripheral chemoreflex function in CHF rabbits and possible mechanisms mediating this effect. EXT partially, but not fully, normalized the exaggerated baseline renal sympathetic nerve activity (RSNA) and the response of RSNA to hypoxia in CHF rabbits. EXT also decreased the baseline CB nerve single-fiber discharge (4.9 +/- 0.4 vs. 7.7 +/- 0.4 imp/s at Po(2) = 103 +/- 2.3 Torr) and the response to hypoxia (20.6 +/- 1.1 vs. 36.3 +/- 1.3 imp/s at Po(2) = 41 +/- 2.2 Torr) from CB chemoreceptors in CHF rabbits, which could be reversed by treatment of the CB with ANG II or a nNOS inhibitor. Our results also showed that NO concentration and protein expression of nNOS were increased in the CBs from EXT + CHF rabbits, compared with that in CHF rabbits. On the other hand, elevated ANG II concentration and AT(1)-receptor overexpression of the CBs in CHF state were blunted by EXT. These results indicate that EXT normalizes the CB chemoreflex in CHF by preventing an increase in afferent CB chemoreceptor activity. EXT reverses the alterations in the nNOS-NO and ANG II-AT(1)-receptor pathways in the CB responsible for chemoreceptor sensitization in CHF.

Reproducibility of the self-controlled six-minute walking test in heart failure patients

INTRODUCTION

The six-minute walk test (6WT) has been proposed to be a submaximal test, but could actually demand a high level of exercise intensity from the patient, expressed by a respiratory quotient >1.0, following the guideline recommendations. Standardizing the 6WT using the Borg scale was proposed to make sure that all patients undergo a submaximal walking test.

PURPOSE

To test the reproducibility of the six-minute treadmill cardiopulmonary walk test (6CWT) using the Borg scale and to make sure that all patients undergo a submaximal test.

METHODS

Twenty-three male heart failure patients (50+/-9 years) were included; these patients had both ischemic (5) and non-ischemic (18) heart failure with a left ventricle ejection fraction of 23+/-7%, were diagnosed as functional class NYHA II-III and were undergoing optimized drug therapy. Patients were guided to walk at a pace between "relatively easy and slightly tiring" (11 and 13 on Borg scale). The 6CWT using the Borg scale was performed two times on a treadmill with zero inclination and patient control of speed with an interval of 24 hours. During the sixth minute, we analyzed ventilation (VE, L/min), respiratory quotient, Oxygen consumption (VO2, ml/kg/min), VE/VCO2 slope, heart rate (HR, bpm), systolic blood pressure (SBP, mmHg), diastolic (DBP, mmHg) blood pressure and distance.

RESULTS

The intraclass correlation coefficients at the sixth minute were: HR (r i=0.96, p<0.0001), VE (r i=0.84, p<0.0001), SBP (r i=0.72, p=0.001), distance (r i=0.88, p<0.0001), VO2 (r i=0.92, p<0.0001), SlopeVE/VCO2 (r i=0.86, p<0.0001) and RQ<1 (r i=0.6, p=0.004).

CONCLUSION

Using the 6CWT with the Borg scale was reproducible, and it seems to be an appropriate method to evaluate the functional capacity of heart failure patients while making sure that they undergo a submaximal walking test.

Exercise intolerance

Exercise intolerance is the primary symptom of chronic diastolic heart failure. It is part of the definition of heart failure and is intimately linked to its pathophysiology. Further, exercise intolerance affects the diagnosis and prognosis of heart failure. In addition, understanding the mechanisms of exercise intolerance can lead to developing and testing rational treatments for heart failure. This article focuses on the fundamental principles of exercise physiology and on the assessment, pathophysiology, and potential treatment of exercise intolerance in diastolic heart failure.

Implications of chronic heart failure on peripheral vasculature and skeletal muscle before and after exercise training

The pathophysiology of chronic heart failure (CHF) is typically conceptualized in terms of cardiac dysfunction. However, alterations in peripheral blood flow and intrinsic skeletal muscle properties are also now recognized as mechanisms for exercise intolerance that can be modified by therapeutic exercise. This overview focuses on blood delivery, oxygen extraction and utilization that result from heart failure. Related features of inflammation, changes in skeletal muscle signaling pathways, and vulnerability to skeletal muscle atrophy are discussed. Specific focus is given to the ways in which perfusion and skeletal muscle properties affect exercise intolerance and how peripheral improvements following exercise training increase aerobic capacity. We also identify gaps in the literature that may constitute priorities for further investigation.

The association between vitamin D and inflammation with the 6-minute walk and frailty in patients with heart failure

OBJECTIVES

To identify relationships between anabolic hormones, inflammatory markers, and physical function.

DESIGN

Cross-sectional.

SETTING

Outpatient university heart failure program in Connecticut.

PARTICIPANTS

Sixty patients with an ejection fraction of 40% or less.

MEASUREMENTS

The 6-minute walk distance and frailty phenotype were measured. The relationship between physical measures of hormones and inflammatory mediators were examined. Linear and ordinal logistic regression analyses were performed for the physical measures.

RESULTS

Forty-three men (mean age 77 +/- 9) and 17 women (mean age 78 +/- 12) participated. Longer 6-minute walk distance was correlated with higher 25-hydroxyvitamin D (25OHD) level, and a shorter walk was correlated with higher cortisol: dehydroepiandrosterone sulphate (DHEAS) ratio, high-sensitivity C-reactive protein (hsCRP), interleukin-6 (IL6), and intact parathyroid hormone (PTH) (all P<.05). Percentage of free testosterone, DHEAS alone, and N-terminal pro-brain natriuretic peptide (NTpro-BNP) did not correlate with 6-minute walk distance. Higher frailty phenotype score (more frail) was correlated with higher high-sensitivity CRP, higher IL6, and lower 25OHD levels (all P<.05). Linear regression with the 6-minute walk distance as the dependent variable and independent variables of age, sex, percentage of free testosterone, DHEAS, 25OHD, intact PTH, hsCRP, IL6, cortisol/DHEAS ratio, and NTpro-BNP, revealed age, sex, 25OHD and hsCRP to be significant (coefficient of determination=53.5%). Ordinal logistic regression with the frailty phenotype and hormonal levels revealed that age, 25OHD, and hsCRP also predicted frailty status.

CONCLUSION

Twenty-five-hydroxyvitamin D and hsCRP levels may contribute to lower aerobic capacity and frailty in patients with heart failure. A longitudinal study will further define the role of 25OHD and hsCRP on muscle strength and functional decline.

Skeletal muscle contractile protein function is preserved in human heart failure

Skeletal muscle weakness is a common finding in patients with chronic heart failure (CHF). This functional deficit cannot be accounted for by muscle atrophy alone, suggesting that the syndrome of heart failure induces a myopathy in the skeletal musculature. To determine whether decrements in muscle performance are related to alterations in contractile protein function, biopsies were obtained from the vastus lateralis muscle of four CHF patients and four control patients. CHF patients exhibited reduced peak aerobic capacity and knee extensor muscle strength. Decrements in whole muscle strength persisted after statistical control for muscle size. Thin filaments and myosin were isolated from biopsies and mechanically assessed using the in vitro motility assay. Isolated skeletal muscle thin-filament function, however, did not differ between CHF patients and controls with respect to unloaded shortening velocity, calcium sensitivity, or maximal force. Similarly, no difference in maximal force or unloaded shortening velocity of isolated myosin was observed between CHF patients and controls. From these results, we conclude that skeletal contractile protein function is unaltered in CHF patients. Other factors, such as a decrease in total muscle myosin content, are likely contributors to the skeletal muscle strength deficit of heart failure.

Cardiopulmonary exercise testing and its application

Cardiopulmonary exercise testing (CPET) has become an important clinical tool to evaluate exercise capacity and predict outcome in patients with heart failure and other cardiac conditions. It provides assessment of the integrative exercise responses involving the pulmonary, cardiovascular and skeletal muscle systems, which are not adequately reflected through the measurement of individual organ system function. CPET is being used increasingly in a wide spectrum of clinical applications for evaluation of undiagnosed exercise intolerance and for objective determination of functional capacity and impairment. This review focuses on the exercise physiology and physiological basis for functional exercise testing and discusses the methodology, indications, contraindications and interpretation of CPET in normal people and in patients with heart failure.

Muscle Strength in Relation to Disease Severity in Patients with Congestive Heart Failure

OBJECTIVE

Indices of exercise capacity such as peak oxygen uptake (VO2peak) and muscle strength are important in association with reduced mortality. The present study compared differences in VO2peak and muscle strength indices (grip strength and knee extensor and flexor muscle strength) with disease severity and investigated the relation of these variables in congestive heart failure (CHF) patients.

DESIGN

The study comprised 102 patients with stable CHF (93 men, age 61.4 +/- 10.2 yrs) with left ventricular ejection fraction (LVEF) <40% by echocardiography. We used New York Heart Association (NYHA) functional class to index disease severity. VO2peak, grip strength, knee extensor, and flexor muscle strength were determined. Patients were divided into three groups by NYHA class: class I (n = 39), class II (n = 49), and class III (n = 14).

RESULTS

Age, sex, and LVEF did not differ according to NYHA class. VO2peak and all muscle strength indices decreased with increases in NYHA class (P < 0.05). VO2peak correlated positively with all muscle strengths (P < 0.05). Stepwise linear regression analysis revealed that grip and knee extensor strength were important in predicting VO2peak.

CONCLUSIONS

Exercise capacity and disease severity in CHF patients may be influenced not only by lower-limb but also upper-limb muscle strength.

Impact of diabetes, chronic heart failure, congenital heart disease and chronic obstructive pulmonary disease on acute and chronic exercise responses

Several chronic diseases are known to negatively affect the ability of an individual to perform exercise. However, the altered exercise capacity observed in these patients is not solely associated with the heart and lungs dysfunction. Exercise has also been shown to play an important role in the management of several pathologies encountered in the fields of cardiology and pneumology. Studies conducted in our institution regarding the influence of diabetes, chronic heart failure, congenital heart disease and chronic pulmonary obstructive disease on the acute and chronic exercise responses, along with the beneficial effects of exercise training in these populations, are reviewed.