Exercise-induced vasodilation in forearm circulation of normal subjects and patients with congestive heart failure: role of endothelium-derived nitric oxide

The First Dedicated Comprehensive Heart Failure Program in the United States: The Division of Circulatory Physiology at Columbia Presbyterian (1992-2004)

The first dedicated multidisciplinary heart failure program in the United States was founded as the Division of Circulatory Physiology at the Columbia University College of Physicians & Surgeons in 1992. The Division was administratively and financially independent of the Division of Cardiology and grew to 24 faculty members at its peak. Its administrative innovations included (1) a comprehensive full-integrated service line, with 2 differentiated clinical teams, one devoted to drug therapy and the other to heart transplantation and ventricular assist devices; (2) a nurse specialist/physician assistant-led clinical service; and (3) a financial structure independent of (and not supported by) other cardiovascular medical or surgical services. The division had 3 overarching missions: (1) to promote a unique career development path for each faculty member to be linked to recognition in a specific area of heart failure expertise; (2) to change the trajectory and enhance the richness of intellectual discourse in the discipline of heart failure, so as to foster an understanding of fundamental mechanisms and to develop new therapeutics; and (3) to provide optimal medical care to patients and to promote the ability of other physicians to provide optimal care. The major research achievements of the division included (1) the development of beta-blockers for heart failure, from initial hemodynamic assessments to proof-of-concept studies to large-scale international trials; (2) the development and definitive assessment of flosequinan, amlodipine, and endothelin antagonists; (3) initial clinical trials and concerns with nesiritide; (4) large-scale trials evaluating dosing of angiotensin converting-enzyme inhibitors and the efficacy and safety of neprilysin inhibition; (5) identification of key mechanisms in heart failure, including neurohormonal activation, microcirculatory endothelial dysfunction, deficiencies in peripheral vasodilator pathways, noncardiac factors in driving dyspnea, and the first identification of subphenotypes of heart failure and a preserved ejection fraction; (6) the development of a volumetric approach to the assessment of myocardial shortening; (7) conceptualization and early studies of cardiac contractility modulation as a treatment for heart failure; (8) novel approaches to the identification of cardiac allograft rejection and new therapeutics to prevent allograft vasculopathy; and (9) demonstration of the effect of left ventricular assist devices to induce reverse remodeling, and the first randomized trial showing a survival benefit with ventricular assist devices. Above all, the division served as an exceptional incubator for a generation of leaders in the field of heart failure.

Cardiovascular Benefits from Gliflozins: Effects on Endothelial Function

Type 2 diabetes mellitus (T2DM) is a known independent risk factor for atherosclerotic cardiovascular disease (CVD) and solid epidemiological evidence points to heart failure (HF) as one of the most common complications of diabetes. For this reason, it is imperative to consider the prevention of CV outcomes as an effective goal for the management of diabetic patients, as important as lowering blood glucose. Endothelial dysfunction (ED) is an early event of atherosclerosis involving adhesion molecules, chemokines, and leucocytes to enhance low-density lipoprotein oxidation, platelet activation, and vascular smooth muscle cell proliferation and migration. This abnormal vascular phenotype represents an important risk factor for the genesis of any complication of diabetes, contributing to the pathogenesis of not only macrovascular disease but also microvascular damage. Gliflozins are a novel class of anti-hyperglycemic agents used for the treatment of Type 2 diabetes mellitus (T2DM) that selectively inhibit the sodium glucose transporter 2 (SGLT2) in the kidneys and have provoked large interest in scientific community due to their cardiovascular beneficial effects, whose underlying pathophysiology is still not fully understood. This review aimed to analyze the cardiovascular protective mechanisms of SGLT2 inhibition in patients T2DM and their impact on endothelial function.

Peripheral Vascular Function in Dilated Cardiomyopathy of Different Etiology

Vascular function in dilated cardiomyopathy of different etiology has been poorly investigated. Moreover, reference values of flow-mediated dilation (FMD) in chronic heart failure (CHF) need to be updated according to the new standardized protocols. We characterized the vascular impairment in different stages of post-ischemic dilated cardiomyopathy (PI-DC) or idiopathic dilated cardiomyopathy (I-DC). Eighty consecutive outpatients with CHF in different New York Heart Association (NYHA) classes (45 PI-DC, 35 I-DC) and 50 control subjects underwent FMD and brachial distensibility coefficient measurement. Patients with CHF showed a marked impairment in FMD compared with controls that worsened from classes NYHA I-II to III-IV, independently of etiology ( P < .05). New York Heart Association I-II PI-DC patients showed a worse FMD compared with NYHA I-II I-DC patients ( P < .05). Brachial distensibility coefficient values were significantly lower in patients with CHF compared with controls ( P < .001) without differences between PI-DC and I-DC. In conclusion, advanced CHF is characterized by vascular impairment that is independent of etiology. In the early stages of CHF, endothelial dysfunction is more severe in patients with PI-DC compared with I-DC probably due to the high cardiovascular risk profile. In I-DC, vascular function impairment is independent of cardiovascular risk factors and could participate in the pathogenesis of I-DC.

Peripheral endothelial dysfunction is a novel risk factor for systolic dysfunction and heart failure progression

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Peripheral endothelial dysfunction (PED) predicts adverse outcomes in patients with stage B HF.

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PED was independently associated with stage B HF, even after adjusting for co-variables.

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PED was strongly associated with progression from stage B to overt stage C HF.

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Detecting PED may stratify the risk of HF progression.

Background

ACC/AHA guidelines recognize the progressive nature of heart failure (HF). Patients with risk factors (Stage A) are at risk for developing asymptomatic cardiac dysfunction (Stage B), which may then lead to symptomatic HF (Stage C). As such, therapies targeting abnormalities in stages A and B may protect against development of symptomatic HF. peripheral endothelial dysfunction (PED) is an independent predictor of adverse outcomes in patients with stage C HF. The aim of the current study was to evaluate whether PED might be associated with Stage B HF, where therapeutic interventions to prevent progression might be more efficacious.

Methods

We performed a retrospective cross-sectional analysis of patients who were referred for routine cardiovascular evaluation that included an assessment of peripheral endothelial function with reactive hyperemia-peripheral arterial tonometry. Individuals in this study underwent routine clinically indicated echocardiography within 2 months of testing for PED. Patients with clinical HF were excluded.

Results

The study included 355 patients (mean age 51.5 ± 14.6 years, 231 (65.1%) female). There was a significant association between PED and Stage B HF (Odds Ratio (OR) 6.38; P < 0.0001) that persisted after stratifying by sex. In multivariate analyses PED was significantly associated with Stage B HF (OR 5.33; P = 0.0038), and was also associated with progression to overt stage C HF (OR 4.63; P = 0.033).

Conclusion

Peripheral endothelial dysfunction is risk factor for Stage B HF, even in low risk individuals. Further study is warranted to better understand the mechanistic basis of PED in HF to reduce the risk of symptomatic progression.

Asymptomatic Left Ventricle Systolic Dysfunction

Heart failure is a common debilitating illness, associated with significant morbidity and mortality, rehospitalisation and societal costs. Current guidelines and position statements emphasise the management of patients with overt symptomatic disease, but the increasing prevalence of congestive heart failure underscores the need to identify and manage patients with early left ventricular dysfunction prior to symptom onset. Asymptomatic left ventricular systolic dysfunction (ALVSD), classified as stage B heart failure, is defined as depressed left ventricular systolic function in the absence of clinical heart failure. Early initiation of therapies in patients with presumed ALVSD has been shown to lead to better outcomes. In this article, the authors clarify issues surrounding the definition and natural history of ALVSD, outline clinical tools that may be of value in identifying patients with ALVSD and highlight potential opportunities for future investigations to better address aspects of our understanding of this complex syndrome.

Peripheral vascular function, oxygen delivery and utilization: the impact of oxidative stress in aging and heart failure with reduced ejection fraction

The aging process appears to be a precursor to many age-related diseases, perhaps the most impactful of which is cardiovascular disease (CVD). Heart disease, a manifestation of CVD, is the leading cause of death in the USA, and heart failure (HF), a syndrome that develops as a consequence of heart disease, now affects almost six million American. Importantly, as this is an age-related disease, this number is likely to grow along with the ever-increasing elderly population. Hallmarks of the aging process and HF patients with a reduced ejection fraction (HFrEF) include exercise intolerance, premature fatigue, and limited oxygen delivery and utilization, perhaps as a consequence of diminished peripheral vascular function. Free radicals and oxidative stress have been implicated in this peripheral vascular dysfunction, as a redox imbalance may directly impact the function of the vascular endothelium. This review aims to bring together studies that have examined the impact of oxidative stress on peripheral vascular function and oxygen delivery and utilization with both healthy aging and HFrEF.

Exercise limitations in heart failure with reduced and preserved ejection fraction

The hallmark symptom of chronic heart failure (HF) is severe exercise intolerance. Impaired perfusive and diffusive O₂ transport are two of the major determinants of reduced physical capacity and lowered maximal O₂ uptake in patients with HF. It has now become evident that this syndrome manifests at least two different phenotypic variations: heart failure with preserved or reduced ejection fraction (HFpEF and HFrEF, respectively). Unlike HFrEF, however, there is currently limited understanding of HFpEF pathophysiology, leading to a lack of effective pharmacological treatments for this subpopulation. This brief review focuses on the disturbances within the O₂ transport pathway resulting in limited exercise capacity in both HFpEF and HFrEF. Evidence from human and animal research reveals HF-induced impairments in both perfusive and diffusive O₂ conductances identifying potential targets for clinical intervention. Specifically, utilization of different experimental approaches in humans (e.g., small vs. large muscle mass exercise) and animals (e.g., intravital microscopy and phosphorescence quenching) has provided important clues to elucidating these pathophysiological mechanisms. Adaptations within the skeletal muscle O₂ delivery-utilization system following established and emerging therapies (e.g., exercise training and inorganic nitrate supplementation, respectively) are discussed. Resolution of the underlying mechanisms of skeletal muscle dysfunction and exercise intolerance is essential for the development and refinement of the most effective treatments for patients with HF.

Rationale and design of a multicenter placebo-controlled double-blind randomized trial to evaluate the effect of empagliflozin on endothelial function: the EMBLEM trial

BACKGROUND

Type 2 diabetes mellitus (T2DM) is characterized by systemic metabolic abnormalities and the development of micro- and macrovascular complications, resulting in a shortened life expectancy. A recent cardiovascular (CV) safety trial, the EMPA-REG OUTCOME trial, showed that empagliflozin, a sodium glucose cotransporter 2 (SGLT2) inhibitor, markedly reduced CV death and all-cause mortality and hospitalization for heart failure in patients with T2DM and established CV disease (CVD). SGLT2 inhibitors are known to not only decrease plasma glucose levels, but also favorably modulate a wide range of metabolic and hemodynamic disorders related to CV pathways. Although some experimental studies revealed a beneficial effect of SGLT2 inhibitors on atherosclerosis, there is a paucity of clinical data showing that they can slow the progression of atherosclerosis in patients with T2DM. Therefore, the EMBLEM trial was designed to investigate whether empagliflozin treatment can improve endothelial function, which plays a pivotal role in the pathogenesis of atherosclerosis, in patients with T2DM and established CVD.

METHODS

The EMBLEM trial is an ongoing, prospective, multicenter, placebo-controlled double-blind randomized, investigator-initiated clinical trial in Japan. A total of 110 participants with T2DM (HbA1c range 6.0-10.0%) and with established CVD will be randomized (1:1) to receive either empagliflozin 10 mg once daily or a placebo. The primary endpoint of the trial is change in the reactive hyperemia (RH)-peripheral arterial tonometry-derived RH index at 24 weeks from baseline. For comparison of treatment effects between the treatment groups, the baseline-adjusted means and their 95% confidence intervals will be estimated by analysis of covariance adjusted for the following allocation factors: HbA1c (<7.0 or ≥7.0%), age (<65 or ≥65 years), systolic blood pressure (<140 or ≥140 mmHg), and current smoking status (nonsmoker or smoker). Key secondary endpoints include the change from baseline for other vascular-related markers such as arterial stiffness, sympathetic nervous activity, and parameters of cardiac and renal function. Importantly, serious adverse effects independently on the causal relationship to the trial drugs and protocol will be also evaluated throughout the trial period.

DISCUSSION

EMBLEM is the first trial to assess the effect of empagliflozin on endothelial function in patients with T2DM and established CVD. Additionally, mechanisms associating empagliflozin-mediated actions with endothelial function and other CV markers will be evaluated. Thus, the trial is designed to elucidate potential mechanisms by which empagliflozin protects CV systems and improves CV outcomes. Trial registration Unique Trial Number, UMIN000024502 ( https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000028197 ).

Nitrite and S -Nitrosohemoglobin Exchange Across the Human Cerebral and Femoral Circulation

Background:

The mechanisms underlying red blood cell (RBC)–mediated hypoxic vasodilation remain controversial, with separate roles for nitrite ( ) and S -nitrosohemoglobin (SNO-Hb) widely contested given their ability to transduce nitric oxide bioactivity within the microcirculation. To establish their relative contribution in vivo, we quantified arterial-venous concentration gradients across the human cerebral and femoral circulation at rest and during exercise, an ideal model system characterized by physiological extremes of O 2 tension and blood flow.

Methods:

Ten healthy participants (5 men, 5 women) aged 24±4 (mean±SD) years old were randomly assigned to a normoxic (21% O 2 ) and hypoxic (10% O 2 ) trial with measurements performed at rest and after 30 minutes of cycling at 70% of maximal power output in hypoxia and equivalent relative and absolute intensities in normoxia. Blood was sampled simultaneously from the brachial artery and internal jugular and femoral veins with plasma and RBC nitric oxide metabolites measured by tri-iodide reductive chemiluminescence. Blood flow was determined by transcranial Doppler ultrasound (cerebral blood flow) and constant infusion thermodilution (femoral blood flow) with net exchange calculated via the Fick principle.

Results:

Hypoxia was associated with a mild increase in both cerebral blood flow and femoral blood flow ( P <0.05 versus normoxia) with further, more pronounced increases observed in femoral blood flow during exercise ( P <0.05 versus rest) in proportion to the reduction in RBC oxygenation ( r =0.680–0.769, P <0.001). Plasma gradients reflecting consumption (arterial>venous; P <0.05) were accompanied by RBC iron nitrosylhemoglobin formation (venous>arterial; P <0.05) at rest in normoxia, during hypoxia ( P <0.05 versus normoxia), and especially during exercise ( P <0.05 versus rest), with the most pronounced gradients observed across the bioenergetically more active, hypoxemic, and acidotic femoral circulation ( P <0.05 versus cerebral). In contrast, we failed to observe any gradients consistent with RBC SNO-Hb consumption and corresponding delivery of plasma S -nitrosothiols ( P >0.05).

Conclusions:

These findings suggest that hypoxia and, to a far greater extent, exercise independently promote arterial-venous delivery gradients of intravascular nitric oxide, with deoxyhemoglobin-mediated reduction identified as the dominant mechanism underlying hypoxic vasodilation.

Dietary nitrate supplementation and exercise tolerance in patients with heart failure with reduced ejection fraction

Endothelial dysfunction and reduced nitric oxide (NO) signaling are key abnormalities leading to skeletal muscle oxygen delivery-utilization mismatch and poor physical capacity in patients with heart failure with reduced ejection fraction (HFrEF). Oral inorganic nitrate supplementation provides an exogenous source of NO that may enhance locomotor muscle function and oxygenation with consequent improvement in exercise tolerance in HFrEF. Thirteen patients (left ventricular ejection fraction ≤40%) were enrolled in a double-blind, randomized crossover study to receive concentrated nitrate-rich (nitrate) or nitrate-depleted (placebo) beetroot juice for 9 days. Low- and high-intensity constant-load cardiopulmonary exercise tests were performed with noninvasive measurements of central hemodynamics (stroke volume, heart rate, and cardiac output via impedance cardiography), arterial blood pressure, pulmonary oxygen uptake, quadriceps muscle oxygenation (near-infrared spectroscopy), and blood lactate concentration. Ten patients completed the study with no adverse clinical effects. Nitrate-rich supplementation resulted in significantly higher plasma nitrite concentration compared with placebo (240 ± 48 vs. 56 ± 8 nM, respectively; P < 0.05). There was no significant difference in the primary outcome of time to exercise intolerance between nitrate and placebo (495 ± 53 vs. 489 ± 58 s, respectively; P > 0.05). Similarly, there were no significant differences in central hemodynamics, arterial blood pressure, pulmonary oxygen uptake kinetics, skeletal muscle oxygenation, or blood lactate concentration from rest to low- or high-intensity exercise between conditions. Oral inorganic nitrate supplementation with concentrated beetroot juice did not present with beneficial effects on central or peripheral components of the oxygen transport pathway thereby failing to improve exercise tolerance in patients with moderate HFrEF.

Potentiation of the NO-cGMP pathway and blood flow responses during dynamic exercise in healthy humans

PURPOSE

Previous work has shown nitric oxide (NO) contributes to ~15% of the hyperemic response to dynamic exercise in healthy humans. This NO-mediated vasodilation occurs, in part, via increases in intracellular cyclic guanosine monophosphate (cGMP), which is catabolized by phosphodiesterase. We sought to examine the effect of phosphodiesterase-5 (PDE-5) inhibition on forearm blood flow (FBF) responses to dynamic handgrip exercise in healthy humans and the role of NO. We hypothesized exercise hyperemia would be augmented by sildenafil citrate (SDF, PDE-5 inhibitor). We further hypothesized any effect of SDF on exercise hyperemia would be abolished with intra-arterial infusion of the NO synthase (NOS) inhibitor L-N^G-monomethyl arginine (L-NMMA).

METHODS

FBF (Doppler ultrasound) was assessed at rest and during 5 min of dynamic forearm handgrip exercise at 15% of maximal voluntary contraction under control (saline) conditions and during 3 experimental protocols: (1) oral SDF (n = 10), (2) intra-arterial L-NMMA (n = 20), (3) SDF and L-NMMA (n = 10). FBF responses to intra-arterial sodium nitroprusside (NTP, NO donor) were also assessed.

RESULTS

FBF increased with exercise (p < 0.01). Intra-arterial infusion of L-NMMA resulted in a reduction in exercise hyperemia (17 ± 1 to 15 ± 1 mL/dL/min, p < 0.01). Although the hyperemic response to NTP was augmented by SDF (area under the curve: 41 ± 7 vs 61 ± 11 AU, p < 0.01), there was no effect of SDF on exercise hyperemia (p = 0.33).

CONCLUSIONS

Despite improving NTP-mediated vasodilation, oral SDF failed to augment exercise hyperemia in young, healthy adults. These observations reflect a minor contribution of NO and the cGMP pathway during exercise hyperemia in healthy young humans.

Effect of Heart Failure With Preserved Ejection Fraction on Nitric Oxide Metabolites

Endothelial function may be deranged in heart failure with preserved ejection fraction (HFpEF). Serum NO-derived metabolites (NO_m) might provide a biochemical surrogate of endothelial function in patients with heart failure (HF). We measured serum NO_m in 415 participants in the Penn HF Study. Participants with HFpEF (n = 82) and those whose EF had recovered (Recovered-HF, n = 125) were matched 1:1 to heart failure with reduced ejection fraction (HFrEF) participants based on age, gender, race, tobacco use, and eGFR. Serum NO_m levels were quantified after chemical reduction coupled with gas-phase chemiluminescence detection. After adjustment for matching covariates and BMI, HFpEF (34.5 μM; interquartile range [IQR] 25.0, 51.5) participants had lower NO_m levels than HFrEF (41.0 μM; IQR 28.3, 58.0; ratio of HFpEF:HFrEF 0.82, 95% confidence interval [CI] 0.67 to 0.99; p = 0.04), which further decreased when adjusted for covariates that affect endothelial function (ratio 0.79, 95% CI 0.65 to 0.98; p = 0.03). There were no differences between HFrEF (34.0; IQR 25.3, 49.0) and matched Recovered-HF (36.0 μM; IQR 25.0, 55.0) or HFpEF and Recovered-HF. Age (+21%/10-year increase, p <0.001) and black race (-28%, p = 0.03) associated with NO_m in HFpEF, whereas age (+11%/10-year increase, p = 0.03), current tobacco use (+67%, p = 0.01), and eGFR (p = 0.01) associated with NO_m in Recovered-HF. In conclusion, HFpEF participants have reduced NO_m compared with HFrEF in this matched cohort. This might suggest either compromised endothelial function or poor dietary intake. Black race was associated with lower NO_m in HFpEF.

Heart Failure, Left Ventricular Remodeling, and Circulating Nitric Oxide Metabolites

Background

Stable plasma nitric oxide (NO) metabolites (NO_M), composed predominantly of nitrate and nitrite, are attractive biomarkers of NO bioavailability. NO_M levels integrate the influence of NO‐synthase‐derived NO production/metabolism, dietary intake of inorganic nitrate/nitrite, and clearance of NO_M. Furthermore, nitrate and nitrite, the most abundant NO_M, can be reduced to NO via the nitrate‐nitrite‐NO pathway.

Methods and Results

We compared serum NO_M among subjects without heart failure (n=126), subjects with heart failure and preserved ejection fraction (HFpEF; n=43), and subjects with heart failure and reduced ejection fraction (HFrEF; n=32). LV mass and extracellular volume fraction were measured with cardiac MRI. Plasma NO_M levels were measured after reduction to NO via reaction with vanadium (III)/hydrochloric acid. Subjects with HFpEF demonstrated significantly lower unadjusted levels of NO_M (8.0 μmol/L; 95% CI 6.2–10.4 μmol/L; ANOVA P=0.013) than subjects without HF (12.0 μmol/L; 95% CI 10.4–13.9 μmol/L) or those with HFrEF (13.5 μmol/L; 95% CI 9.7–18.9 μmol/L). There were no significant differences in NO_M between subjects with HFrEF and subjects without HF. In a multivariable model that adjusted for age, sex, race, diabetes mellitus, body mass index, current smoking, systolic blood pressure, and glomerular filtration rate, HFpEF remained a predictor of lower NO_M (β=−0.43; P=0.013). NO_M did not correlate with LV mass, or LV diffuse fibrosis.

Conclusions

HFpEF, but not HFrEF, is associated with reduced plasma NO_M, suggesting greater endothelial dysfunction, enhanced clearance, or deficient dietary ingestion of inorganic nitrate. Our findings may underlie the salutary effects of inorganic nitrate supplementation demonstrated in recent clinical trials in HFpEF.

Selective Vascular Endothelial Protection Reduces Cardiac Dysfunction in Chronic Heart Failure

Background—

Chronic heart failure (CHF) induces endothelial dysfunction in part because of decreased nitric oxide (NO · ) production, but the direct link between endothelial dysfunction and aggravation of CHF is not directly established. We previously reported that increased NO production via inhibition of protein tyrosine phosphatase 1B (PTP1B) is associated with reduced cardiac dysfunction in CHF. Investigation of the role of endothelial PTP1B in these effects may provide direct evidence of the link between endothelial dysfunction and CHF.

Methods and Results—

Endothelial deletion of PTP1B was obtained by crossing LoxP-PTP1B with Tie2-Cre mice. CHF was assessed 4 months after myocardial infarction. In some experiments, to exclude gene extinction in hematopoietic cells, Tie2-Cre/LoxP-PTP1B mice were lethally irradiated and reconstituted with bone marrow from wild-type mice, to obtain mouse with endothelial-specific deletion of PTP1B. Vascular function evaluated ex vivo in mesenteric arteries showed that in wild-type mice, CHF markedly impaired NO-dependent flow-mediated dilatation. CHF-induced endothelial dysfunction was less marked in endoPTP1B −/− mice, suggesting restored NO production. Echocardiographic, hemodynamic, and histological evaluations demonstrated that the selectively improved endothelial function was associated with reduced left ventricular dysfunction and remodeling, as well as increased survival, in the absence of signs of stimulated angiogenesis or increased cardiac perfusion.

Conclusions—

Prevention of endothelial dysfunction, by endothelial PTP1B deficiency, is sufficient to reduce cardiac dysfunction post myocardial infarction. Our results provide for the first time a direct demonstration that endothelial protection per se reduces CHF and further suggest a causal role for endothelial dysfunction in CHF development.

Exercise training in chronic heart failure: improving skeletal muscle O2 transport and utilization

Chronic heart failure (CHF) impairs critical structural and functional components of the O2 transport pathway resulting in exercise intolerance and, consequently, reduced quality of life. In contrast, exercise training is capable of combating many of the CHF-induced impairments and enhancing the matching between skeletal muscle O2 delivery and utilization (Q̇mO2 and V̇mO2 , respectively). The Q̇mO2 /V̇mO2 ratio determines the microvascular O2 partial pressure (PmvO2 ), which represents the ultimate force driving blood-myocyte O2 flux (see Fig. 1). Improvements in perfusive and diffusive O2 conductances are essential to support faster rates of oxidative phosphorylation (reflected as faster V̇mO2 kinetics during transitions in metabolic demand) and reduce the reliance on anaerobic glycolysis and utilization of finite energy sources (thus lowering the magnitude of the O2 deficit) in trained CHF muscle. These adaptations contribute to attenuated muscle metabolic perturbations (e.g., changes in [PCr], [Cr], [ADP], and pH) and improved physical capacity (i.e., elevated critical power and maximal V̇mO2 ). Preservation of such plasticity in response to exercise training is crucial considering the dominant role of skeletal muscle dysfunction in the pathophysiology and increased morbidity/mortality of the CHF patient. This brief review focuses on the mechanistic bases for improved Q̇mO2 /V̇mO2 matching (and enhanced PmvO2 ) with exercise training in CHF with both preserved and reduced ejection fraction (HFpEF and HFrEF, respectively). Specifically, O2 convection within the skeletal muscle microcirculation, O2 diffusion from the red blood cell to the mitochondria, and muscle metabolic control are particularly susceptive to exercise training adaptations in CHF. Alternatives to traditional whole body endurance exercise training programs such as small muscle mass and inspiratory muscle training, pharmacological treatment (e.g., sildenafil and pentoxifylline), and dietary nitrate supplementation are also presented in light of their therapeutic potential. Adaptations within the skeletal muscle O2 transport and utilization system underlie improvements in physical capacity and quality of life in CHF and thus take center stage in the therapeutic management of these patients.

Heart failure: not a single organ disease but a multisystem syndrome

Heart failure is not simply a single organ disease; rather it is a complex multi-system clinical syndrome, with impairment of endocrine, haematological, musculoskeletal, renal, respiratory and vascular systems, which influence morbidity and mortality.

Vascular endothelial function and blood pressure regulation in afferent autonomic failure

BACKGROUND

Familial dysautonomia (FD) is a rare hereditary disease characterized by loss of afferent autonomic neural fiber signaling and consequent profound impairment of arterial baroreflex function and blood pressure regulation. Whether vascular endothelial dysfunction contributes to defective vasomotor control in this form of afferent autonomic failure is not known.

METHODS

We assessed blood pressure response to orthostatic stress and vascular endothelial function with brachial artery reactivity testing in 34 FD subjects with afferent autonomic failure and 34 healthy control subjects.

RESULTS

Forty-four percent of the afferent autonomic failure subjects had uncontrolled hypertension at supine rest (median systolic blood pressure = 148mm Hg, interquartile range (IQR) = 144-155mm Hg; median diastolic blood pressure = 83mm Hg, IQR = 78-105mm Hg), and 88% had abnormal response to orthostatic stress (median decrease in systolic blood pressure after upright tilt = 48mm Hg, IQR = 29-61mm Hg). Flow-mediated brachial artery reactivity did not differ in subjects with afferent autonomic failure vs. healthy control subjects (median = 6.00%, IQR = 1.86-11.77%; vs. median = 6.27%, IQR = 4.65-9.34%; P = 0.75). In afferent autonomic failure subjects, brachial artery reactivity was not associated with resting blood pressure or the magnitude of orthostatic hypotension but was decreased in association with reduced glomerular filtration rate (r = 0.62; P < 0.001).

CONCLUSIONS

Brachial artery reactivity was preserved in subjects with afferent autonomic failure despite the presence of marked blood pressure dysregulation. Comorbid renal dysfunction was associated with reduced brachial artery reactivity.

Abnormal neurocirculatory control during exercise in humans with chronic renal failure

Abnormal neurocirculatory control during exercise is one important mechanism leading to exercise intolerance in patients with both end-stage renal disease (ESRD) and earlier stages of chronic kidney disease (CKD). This review will provide an overview of mechanisms underlying abnormal neurocirculatory and hemodynamic responses to exercise in patients with kidney disease. Recent studies have shown that ESRD and CKD patients have an exaggerated increase in blood pressure (BP) during both isometric and rhythmic exercise. Subsequent studies examining the role of the exercise pressor reflex in the augmented pressor response revealed that muscle sympathetic nerve activity (MSNA) was not augmented during exercise in these patients, and metaboreflex-mediated increases in MSNA were blunted, while mechanoreflex-mediated increases were preserved under basal conditions. However, normalizing the augmented BP response during exercise via infusion of nitroprusside (NTP), and thereby equalizing baroreflex-mediated suppression of MSNA, an important modulator of the final hemodynamic response to exercise, revealed that CKD patients had an exaggerated increase in MSNA during isometric and rhythmic exercise. In addition, mechanoreflex-mediated control was augmented, and metaboreceptor blunting was no longer apparent in CKD patients with baroreflex normalization. Factors leading to mechanoreceptor sensitization, and other mechanisms underlying the exaggerated exercise pressor response, such as impaired functional sympatholysis, should be investigated in future studies.

Skeletal muscle microvascular oxygenation dynamics in heart failure: exercise training and nitric oxide-mediated function

Chronic heart failure (CHF) impairs nitric oxide (NO)-mediated regulation of skeletal muscle O2 delivery-utilization matching such that microvascular oxygenation falls faster (i.e., speeds PO2mv kinetics) during increases in metabolic demand. Conversely, exercise training improves (slows) muscle PO2mv kinetics following contractions onset in healthy young individuals via NO-dependent mechanisms. We tested the hypothesis that exercise training would improve contracting muscle microvascular oxygenation in CHF rats partly via improved NO-mediated function. CHF rats (left ventricular end-diastolic pressure = 17 ± 2 mmHg) were assigned to sedentary (n = 11) or progressive treadmill exercise training (n = 11; 5 days/wk, 6-8 wk, final workload of 60 min/day at 35 m/min; -14% grade downhill running) groups. PO2mv was measured via phosphorescence quenching in the spinotrapezius muscle at rest and during 1-Hz twitch contractions under control (Krebs-Henseleit solution), sodium nitroprusside (SNP; NO donor; 300 μM), and N(G)-nitro-l-arginine methyl ester (L-NAME, nonspecific NO synthase blockade; 1.5 mM) superfusion conditions. Exercise-trained CHF rats had greater peak oxygen uptake and spinotrapezius muscle citrate synthase activity than their sedentary counterparts (p < 0.05 for both). The overall speed of the PO2mv fall during contractions (mean response time; MRT) was slowed markedly in trained compared with sedentary CHF rats (sedentary: 20.8 ± 1.4, trained: 32.3 ± 3.0 s; p < 0.05), and the effect was not abolished by L-NAME (sedentary: 16.8 ± 1.5, trained: 31.0 ± 3.4 s; p > 0.05). Relative to control, SNP increased MRT in both groups such that trained CHF rats had slower kinetics (sedentary: 43.0 ± 6.8, trained: 55.5 ± 7.8 s; p < 0.05). Improved NO-mediated function is not obligatory for training-induced improvements in skeletal muscle microvascular oxygenation (slowed PO2mv kinetics) following contractions onset in rats with CHF.

Effects of chronic heart failure on neuronal nitric oxide synthase-mediated control of microvascular O2 pressure in contracting rat skeletal muscle

Chronic heart failure (CHF) impairs nitric oxide (NO)-mediated regulation of the skeletal muscle microvascular O(2) delivery/V(O(2)) ratio (which sets the microvascular O(2) pressure, PO(2)mv). Given the pervasiveness of endothelial dysfunction in CHF, this NO-mediated dysregulation is attributed generally to eNOS. It is unknown whether nNOS-mediated PO(2)mv regulation is altered in CHF. We tested the hypothesis that CHF impairs nNOS-mediated PO(2)mv control. In healthy and CHF (left ventricular end diastolic pressure (LVEDP): 6 ± 1 versus 14 ± 1 mmHg, respectively, P < 0.05) rats spinotrapezius muscle blood flow (radiolabelled microspheres), PO(2)mv (phosphorescence quenching), and V(O(2)) (Fick calculation) were measured before and after 0.56 mg kg(-1)i.a. of the selective nNOS inhibitor S-methyl-l-thiocitrulline (SMTC). In healthy rats, SMTC increased baseline PO(2)mv (

CONTROL

29.7 ± 1.4, SMTC: 34.4 ± 1.9 mmHg, P < 0.05) by reducing V(O(2)) (↓20%) without any effect on blood flow and speeded the mean response time (MRT, time to reach 63% of the overall kinetics response,

CONTROL

24.2 ± 2.0, SMTC: 18.5 ± 1.3 s, P < 0.05). In CHF rats, SMTC did not alter baseline PO(2)mv (

CONTROL

25.7 ± 1.6, SMTC: 28.6 ± 2.1 mmHg, P > 0.05), V(O(2)) at rest, or the MRT (CONTROL: 22.8 ± 2.6, SMTC: 21.3 ± 3.0 s, P > 0.05). During the contracting steady-state, SMTC reduced blood flow (↓15%) and V(O(2)) (↓15%) in healthy rats such that PO(2)mv was unaltered (

CONTROL

19.8 ± 1.7, SMTC: 20.7 ± 1.8 mmHg, P > 0.05). In marked contrast, in CHF rats SMTC did not change contracting steady-state blood flow, V(O(2)), or PO(2)mv (

CONTROL

17.0 ± 1.4, SMTC: 17.7 ± 1.8 mmHg, P > 0.05). nNOS-mediated control of skeletal muscle microvascular function is compromised in CHF versus healthy rats. Treatments designed to ameliorate microvascular dysfunction in CHF may benefit by targeting improvements in nNOS function.

Endothelial function and left ventricular remodeling in diabetic and non-diabetic patients after acute coronary syndrome

BACKGROUND

Endothelial dysfunction is an independent predictor of future cardiac events.

MATERIAL/METHODS

We evaluated the relationship between flow-mediated dilation (FMD) in brachial artery and coronary risk factors in 93 patients (70 males, mean age: 62 ± 8 years) with ACS treated with primary angioplasty (PCI). The patients were divided into 2 subgroups: 43 patients with diabetes mellitus type 2 (DM) and 50 non-diabetics (non-DM). Patients were examined on the 3rd day after ACS and after 6 months. FMD on the 3rd day were significantly lower in DM than in non-DM (5.8 ± 2.2% vs. 8.8 ± 4.9%, p=0.0007) and after 6 months (6.2 ± 2.6% vs. 9.4 ± 4.4%, p<0.0001). It was also observed that the improvement of FMD in both groups after a 6-month follow-up inversely correlated with the increase of left ventricular end-diastolic volume (LVEDV) (r=-0.41, p<0.001).

RESULTS

There was an inverse relationship between FMD and age (r=-0.26, p<0.01), BMI (r=-0.26, p<0,005), total cholesterol (r=-0.56, p<0.001) and LDL cholesterol (r=-0.53, p<0.001). There was no relationship between triglycerides, hypertension and history of smoking. In the DM group, FMD negatively correlated with HbA1c (r=-0.68, p<0.001). Restenosis rate was significantly higher in the DM group (19% vs. 6%, p<0.001) but there was no relationship between FMD and restenosis.

CONCLUSIONS

Impaired FMD is more significant in diabetics than in non-diabetic patients with ACS. Lack of improvement of FMD after acute coronary syndrome can be a predictor of detrimental left ventricular remodeling in patients with ACS.

Skeletal muscle arteriolar function following myocardial infarction: Analysis of branch-order effects

Diminished bioavailability of nitric oxide (NO) may impair skeletal muscle arteriolar function after myocardial infarction (MI). We tested the hypotheses that chronic MI induced would diminish 1) endothelial function in large (resting diameter ~75μm) feed arterioles, and 2) functional dilation in feed arterioles, but not smaller arcade (~25μm) or transverse (~15μm) arterioles, in the spinotrapezius muscle of female Sprague-Dawley rats. Additionally, we hypothesized that blockade of NO production with N(G)-nitro-l-arginine methyl ester (l-NAME; 30mg/kg i.v.) would have a greater blunting effect on control rats than MI rats. Endothelial function of the feed arterioles was assessed with an infusion of acetylcholine (1.5μg i.v.) after pretreatment with indomethacin (5mg/kgi.p.). MI blunted the response to acetylcholine in feed arterioles (p=0.037), but did not affect resting or post-contraction diameter at any branching order. l-NAME had similar effects on MI and SHAM rats; the response to acetylcholine was blunted in feed arterioles (p=0.003), resting diameter was diminished in arcade arterioles (p=0.003), and post-contraction diameter was diminished in both arcade arterioles (p=0.03) and transverse arterioles (p=0.05). In conclusion, despite endothelial dysfunction in feed arterioles, functional dilation was not affected by MI in any branching order studied. l-NAME had similar effects on MI and SHAM rats that were branch order-dependent. These branch-order effects should be considered in future studies of the control of blood flow.

Electrical muscle stimulation for chronic heart failure: an alternative tool for exercise training?

Conventional exercise training has been shown conclusively to improve exercise capacity, quality of life, and even reduce mortality in chronic heart failure. Unfortunately, not all heart failure patients are suitable for conventional exercise programs for various reasons. The exciting new technique of electrical muscle stimulation (EMS) of large groups of muscles has been shown to produce a physiologic response consistent with cardiovascular exercise at mild to moderate intensities by increasing peak oxygen consumption, carbon dioxide production, ventilatory capacity, and heart rate. Additionally, there is improvement in muscle strength. The handful of small studies that exist of home-based EMS training of leg muscles in heart failure show that EMS produces similar benefits to conventional exercise in improving exercise capacity, making EMS an alternative to aerobic exercise training in those that cannot undertake conventional exercise. The improvement seen in leg muscle strength promises also to improve mobility in this sedentary population.

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.

Treating heart failure with sildenafil

Sildenafil is a selective inhibitor of type 5 phosphodiesterase, the main phosphodiesterase isoform responsible for hydrolysis of intracellular cyclic guanosine monophosphate in the pulmonary vasculature. It improves exercise capacity and quality of life in patients with systolic heart failure, especially in those who develop secondary pulmonary hypertension. It improves peak oxygen consumption, reduces minute ventilation/carbon dioxide output slope, and acts as a selective pulmonary vasodilator during rest and exercise in patients with heart failure and pulmonary hypertension. It improves flow-mediated maximal dilatation, ergoreflex on ventilation, and breathlessness both after 3 and 6 months of treatment. Sildenafil, by improving endothelial activity and muscle perfusion, improves signaling and ventilatory efficiencies, potentially indicating a novel approach in the therapeutic management of heart failure.

Vascular endothelial function predicts mortality risk in patients with advanced ischaemic chronic heart failure

AIMS

Endothelial function is impaired in advanced chronic heart failure (ACHF) patients. We explored a possible association between endothelial function and subsequent mortality risk in ACHF.

METHODS AND RESULTS

We prospectively assessed brachial flow-mediated dilation (FMD) in 82 consecutive New York Heart Association class IV ischaemic ACHF patients with a mean left ventricular ejection fraction (LVEF) of 22 +/- 3%. Following overnight fasting and discontinuation of all medications for > or = 12 h, percent increase in FMD (%FMD) and nitroglycerin-mediated vasodilation were assessed using linear array ultrasound. All patients were followed for 14 +/- 2 months for adverse cardiovascular events, including death, hospitalization for CHF exacerbation, or myocardial infarction. Patients were divided into two groups: those with an FMD lesser than or equal to the median %FMD of 4.6% (n = 41) and those with an FMD above the median (n = 41). Both groups were comparable regarding cardiovascular risk factors, LVEF, and concomitant medications. During follow-up, 22 (53.6%) patients with FMD lesser than or equal to the median had composite adverse cardiovascular events compared with only eight patients (19.5%) with FMD above the median (P < 0.01). Furthermore, fiver deaths (12.1%) occurred in patients with FMD lesser than or equal to the median, compared with no deaths in patients with FMD above the median (P < 0.03). Cox regression analyses revealed that FMD was an independent predictor for these events.

CONCLUSION

Flow-mediated dilation is associated with increased mortality risk in ischaemic ACHF patients.

Brachial artery differential characteristic impedance: Contributions from changes in young's modulus and diameter

This examination of brachial artery (BA) differential characteristic impedance, DeltaZ (c), illustrates that changes in Z (c) can occur from changes in either BA wall stiffness (Young's modulus, E) and/or its diameter, D. Furthermore, we assessed how changes in both E and D combine in either an isolated, synergistic, or antagonistic manner to yield the net change in BA Z (c). The basis of this analysis is a partial differential equation which approximates DeltaZ (c) as a total differential. The effects on BA DeltaZ (c) of acetylcholine, atenolol, fenoldapine, nitroglycerin, hydrochlorothiazide and other medications are examined using data from previously published studies. Clinical situations which alter BA Z (c), such as congestive heart failure, hypertension, and hyperemia, are also analyzed. Results illustrate the usefulness of the present approach in differentiating how medications, hyperemia, and pathological conditions affect BA DeltaZ (c) by causing independent changes to E and/or D.

Alterations in vasomotor control of coronary resistance vessels in remodelled myocardium of swine with a recent myocardial infarction

The mechanism underlying the progressive deterioration of left ventricular (LV) dysfunction after myocardial infarction (MI) towards overt heart failure remains incompletely understood, but may involve impairments in coronary blood flow regulation within remodelled myocardium leading to intermittent myocardial ischemia. Blood flow to the remodelled myocardium is hampered as the coronary vasculature does not grow commensurate with the increase in LV mass and because extravascular compression of the coronary vasculature is increased. In addition to these factors, an increase in coronary vasomotor tone, secondary to neurohumoral activation and endothelial dysfunction, could also contribute to the impaired myocardial oxygen supply. Consequently, we explored, in a series of studies, the alterations in regulation of coronary resistance vessel tone in remodelled myocardium of swine with a 2 to 3-week-old MI. These studies indicate that myocardial oxygen balance is perturbed in remodelled myocardium, thereby forcing the myocardium to increase its oxygen extraction. These perturbations do not appear to be the result of blunted β-adrenergic or endothelial NO-mediated coronary vasodilator influences, and are opposed by an increased vasodilator influence through opening of K_ATP channels. Unexpectedly, we observed that despite increased circulating levels of noradrenaline, angiotensin II and endothelin-1, α-adrenergic tone remained negligible, while the coronary vasoconstrictor influences of endogenous endothelin and angiotensin II were virtually abolished. We conclude that, early after MI, perturbations in myocardial oxygen balance are observed in remodelled myocardium. However, adaptive alterations in coronary resistance vessel control, consisting of increased vasodilator influences in conjunction with blunted vasoconstrictor influences, act to minimize the impairments of myocardial oxygen balance.

Effects of dietary decosahexaenoic acid (DHA) on eNOS in human coronary artery endothelial cells

Endothelial dysfunction occurs in heart disease and may reduce functional capacity via attenuations in peripheral blood flow. Dietary decosahexaenoic acid (DHA) may improve this dysfunction, but the mechanism is unknown. This study determined if DHA enhances expression and activity of eNOS in cultured human coronary artery endothelial cells (HCAEC). HCAEC from 4 donors were treated with 5 nM, 50 nM, or 1 microM DHA for 7 days to model chronic DHA exposure. A trend for increased expression of endothelial nitric oxide synthase (eNOS) and phospho-eNOS was observed with 5 and 50 nM DHA. DHA also enhanced expression of 2 proteins instrumental in activation of eNOS: phospho-Akt (5 and 50 nM) and HSP90 (50 nM and 1 microM). Vascular endothelial growth factor-induced activation of Akt increased NOx in treated (50 nM DHA) versus untreated HCAEC (9.2 +/- 1.0 vs 3.3 +/- 1.1 micromol/microg protein/microL). Findings suggest that DHA enhances eNOS and Akt activity, augments HSP90 expression, and increases NO bioavailability in response to Akt kinase activation.

C-type natriuretic peptide expression in patients with chronic heart failure: effects of aerobic training

BACKGROUND

C-type natriuretic peptide (CNP) is structurally related to cardiac natriuretic peptides and is currently considered as an endothelium-derived hyperpolarizing factor. Endothelial dysfunction, commonly observed in chronic heart failure (HF) patients is positively affected by physical training.

METHODS

To evaluate the effect of aerobic physical training on the expression of CNP, 90 HF patients on optimal pharmacological treatment (age 62+/-2 years, mean+/-SEM), randomly assigned in a 3 : 1 ratio to either control group (C, 19 patients) or home-based aerobic exercise-training program group (T, 71 patients), completed the protocol. Plasma assay of CNP, brain natriuretic peptide or B-type natriuretic peptide (BNP), and norepinephrine; echocardiogram; and cardiopulmonary-stress test were performed in all patients at enrollment and after 9 months.

RESULTS

At baseline, in both groups, CNP plasma level was significantly related to BNP (R=0.50), ejection fraction (R=0.43), and peak oxygen uptake (VO2, R=0.43, all P<0.001). After 9 months, trained patients showed an improvement in peak VO2 (P<0.001) and ejection fraction (P<0.05), whereas norepinephrine (P<0.05), BNP (P<0.001), and CNP (P<0.001) decreased. No changes occurred in group C. In group T, the decrease in CNP was significantly related to the increase in peak VO2 (R=0.31, P<0.01), and the relation between CNP and BNP was preserved at the end of the program (R=0.41, P<0.001).

CONCLUSION

Clinical and functional improvement after physical training in HF patients is associated with a decrease in adrenergic activation and in both CNP and BNP concentration. Changes in CNP plasma concentration after physical training might reflect an improvement in endothelial function.

Sympathetic nerve activity restrains reflex vasodilatation in heart failure

BACKGROUND

Blunted reflex muscle vasodilatory response during exercise in heart failure (HF) patients may be secondary to augmented vasoconstriction. We tested the hypothesis that the exaggerated sympathetic nerve activity restrains the reflex muscle vasodilatation during exercise in HF patients.

METHODS

We studied the reflex vasodilatory response (plethysmography) during 3 min static handgrip exercise at 30% maximal voluntary contraction in 10 advanced HF patients (45 +/- 3 year, NYHA Functional Class III/IV) and 10 age-matched normal controls (NC, 40 +/- 3 year, P = 0.23) during intra-arterial infusion of: (1) saline control; and (2) alpha-adrenergic blocker (phentolamine).

RESULTS

Baseline forearm vascular conductance (FVC) was lower in HF patients than in NC (2.07 +/- 0.2 vs. 4.26 +/- 0.6 units, respectively; P = 0.002). FVC responses during exercise increased significantly in NC, but not in HF patients (delta changes: 1.05 +/- 0.4 vs. 0.05 +/- 0.2 units, respectively). Phentolamine significantly increased resting FVC in HF patients (from 2.07 +/- 0.2 to 5.74 +/- 0.7 units, P = 0.00004) and restored reflex vasodilatory responses during exercise (delta changes: from 0.05 +/- 0.2 to 1.82 +/- 0.9 units) eliminating the difference in FVC between both groups.

CONCLUSIONS

The blunted reflex muscle vasodilatory response during exercise in advanced HF patients is, at least in part, due to the increase in sympathetic nerve activity.

Exercise training after coronary angioplasty improves cardiorespiratory function

AIM

The aim of this prospective randomized study was to evaluate the impact of long-term aerobic exercise training on respiratory function, left ventricular systolic function and remodeling in patients with coronary heart disease and ischemic heart failure after successful angioplasty.

DESIGN

Patients (n=185) have undergone Doppler echocardiography and ergospirometry. Ninety-five patients practiced 6 month-term aerobic exercise training, less by 10% to their anaerobic threshold. Ninety patients were studied as controls. They were given only drug treatment without training. Measurements were repeated after 6 and 12 months.

RESULTS

Training group patients after 6 months showed significant (p<0.05) improvement in exercise capacity, oxygen consumption and ventilating equivalents. The Doppler echocardiographic findings revealed significant (p<0.05) improvement in ejection fraction, left ventricular and atria morphometric data. Improved ergospirometric and echocardiographic data were established after 12 months, too.

CONCLUSIONS

Long-term aerobic exercise training is an effective and workable measure improving respiratory efficiency, left ventricular systolic function, attenuating negative remodeling and stopping further progression in patients with coronary heart disease and chronic heart failure after successful angioplasty.

Endothelium-mediated modulation of ergoreflex and improvement in exercise ventilation by acute sildenafil in heart failure patients

Reflex neural oversignaling sensitive to muscle by-products (ergoreflex) causes exercise hyperventilation in heart failure (HF). We probed whether an improved endothelial function with sildenafil intake may prevent this effect. In 16 chronic heart failure patients and 16 normal subjects, before and after sildenafil intake (50 mg) or placebo, we measured ergoreflex, flow-mediated brachial artery dilation (FMD, an index of endothelial function), and, during maximal exercise, the slope of ventilation to carbon dioxide production (VE/VCO2, an index of ventilatory efficiency), the ratio of changes in O2 uptake (VO2) versus work rate (WR) (deltaVO2/deltaWR, an index of aerobic efficiency). After sildenafil intake, patients, unlike controls, showed a significant decrease in ergoreflex and VE/VCO2 slope and an increase in FMD and deltaVO2/deltaWR. Ergoreflex changes with sildenafil intake correlated with those in FMD and VE/VCO2. Phosphodiesterase-5 inhibition, by improving endothelial activity and muscle perfusion, modulates signaling and improves ventilatory and aerobic efficiencies, potentially indicating a novel pathway in the HF therapeutic management.

Exercise training reduces sympathetic nerve activity in heart failure patients treated with carvedilol

BACKGROUND

Evidence suggests that carvedilol decreases muscle sympathetic nerve activity (MSNA) in patients with heart failure (HF) but carvedilol fails to improve forearm vascular resistance and overall functional capacity. Exercise training in HF reduces MSNA and improves forearm vascular resistance and functional capacity.

AIMS

To investigate whether the beneficial effects exercise training on MSNA are maintained in the presence of carvedilol.

METHODS AND RESULTS

Twenty seven HF patients, NYHA Class II-III, EF <35%, peak VO(2) <20 ml/kg/min, treated with carvedilol were randomly divided into two groups: exercise training (n=15) and untrained (n=12). MSNA was recorded by microneurography. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. The four-month training program consisted of three 60-min exercise/week on a cycloergometer. Baseline parameters were similar between groups. Exercise training reduced MSNA (-14+/-3.3 bursts/100 HB, p=0.001) and increased forearm blood flow (0.6+/-0.1 mL/min/100 g, p<0.001) in HF patients on carvedilol. In addition, exercise training improved peak VO(2) in HF patients (20+/-6%, p=0.002). MSNA, FBF and peak VO(2) were unchanged in untrained HF patients on carvedilol.

CONCLUSION

Exercise training reduces MSNA in heart failure patients treated with carvedilol. In addition, the beneficial effects of exercise training on muscle blood flow and functional capacity are still realized in patients on carvedilol.

Inducible nitric oxide synthase activity does not contribute to the maintenance of peripheral vascular tone in patients with heart failure

Enhanced iNOS (inducible nitric oxide synthase) activity may contribute to vascular dysfunction in patients with heart failure. In the present study, we aimed to determine whether iNOS activity contributes to the maintenance of vascular tone in patients with symptomatic heart failure with the use of the highly selective iNOS inhibitor 1400W {N-[3-(aminomethyl)benzyl] acetamidine}. Bilateral forearm blood flow was measured using venous occlusion plethysmography in 12 patients with New York Heart Association class II-IV heart failure and eight matched healthy control subjects during intra-brachial infusion of 1400W (0.1-1 micromol/min), L-NMMA (N(G)-monomethyl-L-arginine; a non-selective NOS inhibitor; 2-8 micromol/min) and noradrenaline (control vasoconstrictor; 60-480 pmol/min). In both patients and controls, intra-brachial infusion of L-NMMA and noradrenaline caused a dose-dependent reduction in infused forearm blood flow (P<0.05 for both): peak reduction of 32+/-6% and 37+/-4% during L-NMMA and 52+/-6% and 49+/-5% during noradrenaline respectively (P values were not significant when patients were compared with controls). In contrast, 1400W had no effect on blood flow at 1 micromol/min [-3+/-4% in patients (95% confidence intervals, -11 to 5%) and 3+/-8% in controls; P value was not significant]. In conclusion, we have demonstrated that intrabrachial selective iNOS inhibition does not influence forearm blood flow in patients with heart failure. We conclude that iNOS activity does not contribute to peripheral vascular tone in patients with symptomatic heart failure.

Comparison of metabolic vasodilation in response to exercise and ischemia and endothelium-dependent flow-mediated dilation in African-American versus non-African-American patients with chronic heart failure

Race-related disparities in response to therapy and clinical outcomes have been reported in patients with chronic heart failure (HF). Vascular dysfunction is an important determinant of therapeutic response and clinical outcomes in chronic HF, but race-related differences of vasodilator responses in those with chronic HF have not been previously characterized. We assessed metabolic vasodilation in response to exercise and ischemia and endothelium-dependent flow-mediated dilation in conduit and resistance vessels with strain gauge venous occlusion plethysmography and high-resolution ultrasound imaging in the forearm circulation of 69 African-American and 188 non-African-American patients with chronic HF. African-American patients had a higher prevalence of hypertension than non-African-American patients (59% vs 35%, p = 0.001) and higher mean arterial pressures despite similar HF treatment (93 +/- 2 vs 89 +/- 1 mm Hg, p = 0.045). Forearm vascular resistance in African-American patients was higher than that of non-African-American patients at rest (22.3 +/- 1.8 vs 16.2 +/- 0.8 U, p <0.001), during exercise (4.7 +/- 0.3 vs 3.8 +/- 0.2 U, p = 0.03), and after ischemia (2.0 +/- 0.3 vs 1.5 +/- 0.1 U, p = 0.04). Endothelium-dependent flow-mediated vasodilation was significantly decreased in African-American compared with non-African-American patients in conduit vessels (brachial artery flow-mediated dilation 0.77 +/- 0.43% vs 1.86 +/- 0.24%, p = 0.03) and resistance vessels (post-ischemic forearm hyperemia 110 +/- 11 vs 145 +/- 10 ml/min/100 ml, p = 0.035). Estimates of differences in race-related vasoreactivity did not substantially change and remained at significant or borderline significant levels after adjustment for hypertension. Impaired vasodilation may contribute to differences in therapeutic response and clinical outcomes in African-American patients with chronic HF.

Anaemia and the heart

Anaemia is common in patients with congestive heart failure (CHF). Its prevalence increases with disease severity as a consequence of renal insufficiency, cytokine production, blood loss, iron deficiency, malnutrition and/or plasma volume overload. Anaemia can contribute to worsening of CHF. There is a nonlinear relationship (U-shaped curve) between haemoglobin and survival. Prevalence of anaemia among elderly people with acute myocardial infarction is high and is associated with more frequent in-hospital events, including death. Anaemia is also associated with higher in-hospital mortality rate after coronary bypass surgery and with all-cause and cardiac mortality after percutaneous coronary interventions. Patients with anaemia and cardiovascular disease have a higher mortality rate after cardiac/noncardiac surgery as compared to those with anaemia but without cardiovascular disease or those with cardiovascular disease but without anaemia. However, not all authors confirmed these findings. Therefore, multicentre trials to clarify this issue are urgently needed. Pleiotropic effects of recombinant human erythropoietin include reduction of myocardial and cerebral infarct size without an increase in haematocrit, neovascularization as well as mobilization of endothelial progenitor cells.

Peripheral vascular endothelial function correlates with exercise capacity in women

BACKGROUND

Vascular endothelial function has been observed to correlate with exercise capacity in predominantly male populations. Gender-based differences exist in the clinical course of coronary artery disease, and previous studies indicate that estrogen may influence endothelial function. These observations raise the possibility that the relationship between endothelial function and exercise capacity in women may differ from that in men.

HYPOTHESIS

This study aimed to determine whether peripheral vascular endothelial function correlates with exercise capacity in women.

METHODS

Women who were referred for clinically indicated exercise testing with technetium-99 myocardial perfusion imaging were consecutively recruited. To ensure a population free of exercise limitation due to ischemic heart disease, women without myocardial perfusion defects were included for analysis in this study (n = 105). Endothelial function was assessed by brachial artery ultrasound flow-mediated vasodilation (FMD). Exercise capacity was defined as the duration of exercise on a symptom-limited Bruce protocol.

RESULTS

Mean FMD was 11.8 +/- 0.6%, and median FMD was 12%. Subjects with an FMD less than the median of 12% had a significantly shorter exercise time than those with FMD > or = 12% (411 +/- 17 vs. 482 +/- 24 s, p = 0.014). There was a significant correlation between FMD and exercise time (r = 0.34, p < 0.001). Age and body mass index were additional predictors of exercise time; however, the relationship between FMD and exercise time was independent of these variables.

CONCLUSION

Brachial artery FMD correlates with exercise capacity in women, even in the absence of ischemic heart disease.

Secondary Pulmonary Hypertension

Pulmonary hypertension (PAH) is defined as mean pulmonary artery pressure greater than 25 mm Hg at rest, or greater than 30 mm Hg with exercise. While there are a myriad of etiologies for PAH, many times a cardiac etiology may be present. This is particularly important from both diagnostic and therapeutic standpoints, as many lesions are readily repairable with corrective surgery. Often, PAH may be drastically reduced, or even returned to baseline, after surgical correction. This article focuses on these cardiac etiologies of secondary PAH. Primary PAH, and PAH secondary to disease of the lung parenchyma, will not be discussed. Pulmonary hypertension is generated by increased flow through the pulmonary arteries, increased resistance to flow, or venous obstruction at the entrance to the left atrium. There is no upper limit of PAH that definitively precludes surgery, thus all patients with surgically approachable lesions should be referred for evaluation.

Vascular endothelial dysfunction and mortality risk in patients with chronic heart failure

BACKGROUND

Endothelial function is known to be impaired in subjects with chronic heart failure (CHF), but the association between endothelial function and subsequent mortality risk in CHF has not been previously reported.

METHODS AND RESULTS

Biomarkers of endothelial function in the systemic arterial circulation (flow-mediated dilation [FMD] in the brachial artery) and the pulmonary circulation (exhaled nitric oxide [NO] production during submaximal exercise) were prospectively assessed in 259 subjects with New York Heart Association class II-III CHF. In subjects with FMD measurements (n=149), there were 12 deaths and 5 urgent transplantations over a median follow-up period of 841 days. In subjects with exhaled NO production measurements (n=110), there were 18 deaths and 1 urgent transplantation over a median follow-up period of 396 days. Both decreased FMD and decreased exhaled NO production were associated with increased risk of death or urgent transplantation after adjustment for other known CHF prognostic factors (age, etiology of CHF, functional class, left ventricular ejection fraction) in Cox multivariate proportional-hazards models (adjusted hazard ratio [HR] estimate for a 1% decrease in FMD=1.20; 95% confidence interval [CI], 1.03 to 1.45; P=0.027; adjusted HR estimate for a 1-ppb/min decrease in exhaled NO production=1.31, 95% CI, 1.01 to 1.69, P=0.04).

CONCLUSIONS

Endothelial dysfunction in CHF, as assessed by FMD in the brachial artery and exhaled NO production during submaximal exercise, is associated with an increased mortality risk in subjects with both ischemic and nonischemic CHF.

The effects of phosphodiesterase-5 inhibition with sildenafil on pulmonary hemodynamics and diffusion capacity, exercise ventilatory efficiency, and oxygen uptake kinetics in chronic heart failure

OBJECTIVES

We sought to investigate the effects of sildenafil, a phosphodiesterase-5 (PDE(5)) inhibitor, on lung function and exercise performance in chronic heart failure (CHF).

BACKGROUND

In CHF, nitric oxide-mediated regulation of lung vascular tone and alveolar-capillary membrane conductance is impaired and contributes to exercise intolerance. The potential for benefits due to increased nitric-oxide availability is unexplored.

METHODS

In 16 patients with CHF and 8 normal subjects, we measured-before and 60 min after sildenafil (50 mg) or placebo-ejection fraction, pulmonary hemodynamics, carbon monoxide diffusion capacity (DLco), with its membrane (D(M)) and capillary blood volume (V(c)) subcomponents, endothelial function (brachial reactive hyperemia) at rest, peak oxygen uptake (VO(2)), increments in VO(2) versus work rate (DeltaVO(2)/DeltaWR), changes in ventilation versus CO(2) production (VE/VCO(2)) slope, and recovery VO(2) time constant (tau) on exertion.

RESULTS

In CHF, sildenafil did not affect cardiac index, wedge pulmonary pressure, or ejection fraction; it significantly (p < 0.01) decreased pulmonary mean artery pressure (-20.4%) and arteriolar resistance (-45.1%), VE/VCO(2) slope (-9.0%) and recovery tau (-25.8%), and increased (p < 0.01) DLco (+11.1%), D(M) (+9.9%) peak VO(2) (+19.7%), DeltaVO(2)/DeltaWR (+11.0%), and brachial reactive hyperemia (+33.3%). No variations occurred in normal subjects and after placebo. Changes in DLco were related to those in VE/VCO(2) slope (r = -0.71; p = 0.002), and changes in brachial hyperemia correlated with those in DeltaVO(2)/DeltaWR (r = 0.80; p = 0.0002).

CONCLUSIONS

This study shows that in CHF PDE(5) inhibition modulates pulmonary pressure and vascular tone, and improves DLco, exercise peak VO(2), aerobic (DeltaVO(2)/DeltaWR) and ventilatory (VE/VCO(2) slope) efficiencies, and oxygen debt (recovery tau). Endothelial mechanisms may underlie these effects.