Abnormal vascular responses in human chronic cardiac failure are both endothelium dependent and endothelium independent

Understanding the Pathobiology of Pulmonary Hypertension Due to Left Heart Disease

The development of pulmonary hypertension (PH) is common and has adverse prognostic implications in patients with heart failure due to left heart disease (LHD), and thus far, there are no known treatments specifically for PH-LHD, also known as group 2 PH. Diagnostic thresholds for PH-LHD, and clinical classification of PH-LHD phenotypes, continue to evolve and, therefore, present a challenge for basic and translational scientists actively investigating PH-LHD in the preclinical setting. Furthermore, the pathobiology of PH-LHD is not well understood, although pulmonary vascular remodeling is thought to result from (1) increased wall stress due to increased left atrial pressures; (2) hemodynamic congestion-induced decreased shear stress in the pulmonary vascular bed; (3) comorbidity-induced endothelial dysfunction with direct injury to the pulmonary microvasculature; and (4) superimposed pulmonary arterial hypertension risk factors. To ultimately be able to modify disease, either by prevention or treatment, a better understanding of the various drivers of PH-LHD, including endothelial dysfunction, abnormalities in vascular tone, platelet aggregation, inflammation, adipocytokines, and systemic complications (including splanchnic congestion and lymphatic dysfunction) must be further investigated. Here, we review the diagnostic criteria and various hemodynamic phenotypes of PH-LHD, the potential biological mechanisms underlying this disorder, and pressing questions yet to be answered about the pathobiology of PH-LHD.

Cardioprotective Actions of Nitroxyl Donor Angeli's Salt are Preserved in the Diabetic Heart and Vasculature in the Face of Nitric Oxide Resistance

Background and Purpose

The risk of fatal cardiovascular events is increased in patients with type 2 diabetes mellitus (T2DM). A major contributor to poor prognosis is impaired nitric oxide (NO•) signalling at the level of tissue responsiveness, termed NO• resistance. This study aimed to determine if T2DM promotes NO• resistance in the heart and vasculature and whether tissue responsiveness to nitroxyl (HNO) is affected.

Experimental Approach

At 8 weeks of age, male Sprague–Dawley rats commenced a high‐fat diet. After 2 weeks, the rats received low‐dose streptozotocin (two intraperitoneal injections, 35 mg·kg⁻¹, over two consecutive days) and continued on the same diet. Twelve weeks later, isolated hearts were Langendorff‐perfused to assess responses to the NO• donor diethylamine NONOate (DEA/NO) and the HNO donor Angeli's salt. Isolated mesenteric arteries were utilised to measure vascular responsiveness to the NO• donors sodium nitroprusside (SNP) and DEA/NO, and the HNO donor Angeli's salt.

Key Results

Inotropic, lusitropic and coronary vasodilator responses to DEA/NO were impaired in T2DM hearts, whereas responses to Angeli's salt were preserved or enhanced. Vasorelaxation to Angeli's salt was augmented in T2DM mesenteric arteries, which were hyporesponsive to the relaxant effects of SNP and DEA/NO.

Conclusion and Implications

This is the first evidence that inotropic and lusitropic responses are preserved, and NO• resistance in the coronary and mesenteric vasculature is circumvented, by the HNO donor Angeli's salt in T2DM. These findings highlight the cardiovascular therapeutic potential of HNO donors, especially in emergencies such as acute ischaemia or heart failure.

Therapeutic potential of resveratrol in heart failure

Despite existing therapies, patients with heart failure have a very poor quality of life and a high 1-year mortality rate. Given the impact of this syndrome on health outcomes, research is being directed toward identifying novel strategies to treat heart failure symptoms as well as to prolong survival. One molecule that has been tested in animal models for this purpose is resveratrol. Resveratrol is a naturally occurring polyphenol found in several plants, and administration of resveratrol has been shown to prevent and/or slow the progression of heart failure in animal models of heart failure induced by myocardial infarction, pressure overload, myocarditis, and chemotherapy-induced cardiotoxicity. In addition, some animal studies have shown that resveratrol improves cardiac function and survival when administered as a treatment for established heart failure. Furthermore, as heart failure induces alterations in skeletal muscle and vasculature that also contribute to certain heart failure symptoms, such as fatigue and exercise intolerance, it has also been shown that resveratrol acts on these peripheral tissues to improve skeletal muscle and endothelial/vascular function. Therefore, if these animal studies translate to humans, resveratrol may prove to be a novel therapy for the treatment of heart failure.

Phosphodiesterase 1 regulation is a key mechanism in vascular aging

Reduced nitric oxide (NO)/cGMP signalling is observed in age-related vascular disease. We hypothesize that this disturbed signalling involves effects of genomic instability, a primary causal factor in aging, on vascular smooth muscle cells (VSMCs) and that the underlying mechanism plays a role in human age-related vascular disease. To test our hypothesis, we combined experiments in mice with genomic instability resulting from the defective nucleotide excision repair gene ERCC1 (Ercc1(d/-) mice), human VSMC cultures and population genome-wide association studies (GWAS). Aortic rings of Ercc1(d/-) mice showed 43% reduced responses to the soluble guanylate cyclase (sGC) stimulator sodium nitroprusside (SNP). Inhibition of phosphodiesterase (PDE) 1 and 5 normalized SNP-relaxing effects in Ercc1(d/-) to wild-type (WT) levels. PDE1C levels were increased in lung and aorta. cGMP hydrolysis by PDE in lungs was higher in Ercc1(d/-) mice. No differences in activity or levels of cGMP-dependent protein kinase 1 or sGC were observed in Ercc1(d/-) mice compared with WT. Senescent human VSMC showed elevated PDE1A and PDE1C and PDE5 mRNA levels (11.6-, 9- and 2.3-fold respectively), which associated with markers of cellular senescence. Conversely, PDE1 inhibition lowered expression of these markers. Human genetic studies revealed significant associations of PDE1A single nucleotide polymorphisms with diastolic blood pressure (DBP; β=0.28, P=2.47×10(-5)) and carotid intima-media thickness (cIMT; β=-0.0061, P=2.89×10(-5)). In summary, these results show that genomic instability and cellular senescence in VSMCs increase PDE1 expression. This might play a role in aging-related loss of vasodilator function, VSMC senescence, increased blood pressure and vascular hypertrophy.

Organic nitrates and nitrate resistance in diabetes: the role of vascular dysfunction and oxidative stress with emphasis on antioxidant properties of pentaerithrityl tetranitrate

Organic nitrates represent a class of drugs which are clinically used for treatment of ischemic symptoms of angina as well as for congestive heart failure based on the idea to overcome the impaired NO bioavailability by “NO” replacement therapy. The present paper is focused on parallels between diabetes mellitus and nitrate tolerance, and aims to discuss the mechanisms underlying nitrate resistance in the setting of diabetes. Since oxidative stress was identified as an important factor in the development of tolerance to organic nitrates, but also represents a hallmark of diabetic complications, this may represent a common principle for both disorders where therapeutic intervention should start. This paper examines the evidence supporting the hypothesis that pentaerithrityl tetranitrate may represent a nitrate for treatment of ischemia in diabetic patients. This evidence is based on the considerations of parallels between diabetes mellitus and nitrate tolerance as well as on preliminary data from experimental diabetes studies.

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.

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.

Impaired nitroglycerin biotransformation in patients with chronic heart failure

OBJECTIVE

Patients with chronic heart failure (CHF) often require higher doses of nitroglycerin (glyceryl trinitrate, GTN) than patients with normal cardiac function to achieve a given haemodynamic goal. Two pathways leading to biotransformation of GTN have been characterized; a high-affinity pathway operative in nanomolar concentration ranges yielding predominantly 1,2-glyceryl dinitrate (1,2-GDN), and a low-affinity pathway operative at higher, micromolar concentrations of GTN associated with a greater proportion of 1,3-GDN formation. We tested the hypothesis that, at a given GTN-induced blood pressure reduction, the CHF group would present with: (i) higher concentrations of GTN; and (ii) decreased ratios of 1,2-GDN/GTN and 1,2-GDN/1,3-GDN compared with healthy subjects (HS).

METHODS

Twelve patients with CHF (left ventricular ejection fraction 20 +/- 5%, NYHA III) and nine HS were investigated during a right cardiac catheterization. GTN was titrated intravenously until mean arterial blood pressure (MAP) was reduced by 15%.

RESULTS

At arterial GTN concentrations of 27.2 [10.0-57.8] nmol l(-1) in CHF and 2.8 [2.5-3.5] nmol l(-1) in HS [median (quartile range), P<0.05 between groups], MAP and mean capillary wedge pressures were reduced similarly in both groups (approx. 15% and 65%, respectively, P = NS between groups). The ratios of 1,2-GDN/GTN and 1,2-GDN/1,3-GDN were lower in CHF (0.86 [0.28-1.58] and 5.8 [5.6-6.3]) compared with HS [1.91 (1.54-2.23) and 7.6 (7.2-10.2), P<0.05], with a negative correlation between the 1,2-GDN/1,3-GDN ratio and the arterial GTN concentrations in the CHF patients (R = -0.8, P<0.05).

CONCLUSION

Patients with CHF have attenuated GTN responsiveness and decreased relative formation of 1,2-GDN in comparison with HS, indicating an altered biotransformation of GTN.

Differences in arterial compliance, microvascular function and venous capacitance between patients with heart failure and either preserved or reduced left ventricular systolic function

BACKGROUND

Up to 50% of patients with the clinical syndrome of heart failure have preserved left ventricular systolic function (HF-PSF). These patients may have abnormalities of ventriculo-vascular coupling, due to increased vascular and ventricular stiffness.

METHODS

We compared arterial compliance, microvascular vasodilator function and venous capacitance (VC) in 3 groups of patients (n=12 each) matched for the presence of coronary heart disease: 1) HF and preserved systolic function (HF-PSF), 2) HF and reduced systolic function (HF-RSF) and 3) controls (no HF, PSF). Arterial compliance was assessed by measuring aortic pulse wave velocity (PWV) with applanation tonometry. Cutaneous microvascular function was assessed using Laser Doppler imaging (LDI) coupled with iontophoresis of endothelium-dependent (acetylcholine) and -independent (sodium nitroprusside) vasodilators. VC was measured using venous occlusion plethysmography.

RESULTS

PWV was significantly higher in HF-PSF subjects than in both HF-RSF and control groups (10.7 [1.1], 8.9 [1.7] and 8.6 [2.1] m/s respectively, p<0.05). Acetylcholine and nitroprusside induced vasodilatation were equally impaired in HF-PSF and HF-RSF, as compared to controls (p<0.01). VC was higher in HF-RSF subjects compared with HF-PSF subjects (1.75 [0.41], 1.34 [0.34] ml/100 ml forearm vol. respectively, p<0.05).

CONCLUSIONS

These findings are consistent with a more marked increase in vascular stiffness in HF-PSF than in HF-RSF and suggest that arterial stiffness, dynamic vasodilator function and venous abnormalities may be implicated in the complex pathophysiology of HF-PSF.

Impaired tissue responsiveness to organic nitrates and nitric oxide: a new therapeutic frontier?

Nitric oxide (NO) is a physiologically important modulator of both vasomotor tone and platelet aggregability. These effects of NO are predominantly mediated by cyclic guanosine-3,'5'-monophosphate (cGMP) via activation of soluble guanylate cyclase. However, in patients with ischemic heart disease, platelets and coronary/peripheral arteries are hyporesponsive to the antiaggregatory and vasodilator effects of NO donors. NO resistance is also associated with a number of coronary risk factors and presents in different disease states. It correlates with conventional measures of "endothelial dysfunction," and represents a multifaceted disorder, in which smooth muscle and platelet NO resistance are equally important, as sites of abnormal NO-driven physiology. NO resistance results largely from a combination of "scavenging" of NO by superoxide anion radical (O(2)(-)) and of (reversible) inactivation of soluble guanylate cyclase. It constitutes an impaired physiological response to endogenous NO (endothelium-derived relaxing factor, EDRF) and, as such, may contribute to the increased risk of ischemic events. Impairment in responsiveness to NO in ischemic patients implies a potential problem that those patients, in greatest need of nitrate therapy, may be least likely to respond. The prognostic impact of NO resistance at vascular and platelet levels has been demonstrated in patients with ischemic heart disease, and it has been shown that a number of agents (angiotensin-converting enzyme [ACE] inhibitors, perhexiline, insulin, and possibly statins) ameliorate this anomaly. The current review examines different aspects of the "NO resistance" phenomenon and discusses some related methodological issues.

Nitric oxide in the pathogenesis of cardiac disease

Endothelial dysfunction is characterized by a vasoconstrictive and prothrombotic state in the vasculature; it plays a role in all stages of cardiac disease and is a significant independent predictor of cardiovascular outcomes. Nitric oxide (NO) performs multiple biologic activities in the endothelium, including vasodilation and antithrombotic actions. Reduced NO bioactivity is a major component of endothelial dysfunction. Impaired NO bioactivity is an important factor in the pathogenesis of atherosclerosis and in the metabolic syndrome. The functions of NO bioactivity in the heart go well beyond those in the endothelium, as all 3 NO synthase (NOS) isoforms-endothelial NOS, neuronal NOS, and inducible NOS-are expressed in cardiac myocytes and mediate systolic, diastolic, and chronotropic cardiac functions. Impairment of NO bioactivity is a pathogenic factor in various forms of cardiac disease. Although these findings support the potential use of NO-targeted therapies for treatment of cardiac disease, the complexities of the biologic actions of NO in the vasculature and heart are such that development of therapies is still largely in the preliminary stages.

Erectile Dysfunction in Heart Failure Patients

Chronic heart failure (HF) and erectile dysfunction (ED) are 2 highly prevalent disorders that frequently occur concomitantly. Coronary artery disease, HF, and ED share several common risk factors, including diabetes mellitus, hypertension, smoking, and dyslipidemia. Additionally, the distinct physiologic sequelae of HF create unique organic and psychologic factors contributing to ED in this patient population. Standard HF therapy with beta-receptor blockers, digoxin and thiazide diuretics may worsen sexual dysfunction owing to medication side effects. This may, in turn, lead to noncompliance in misguided efforts to retain satisfactory sexual activity, with secondary worsening of cardiac capacity. This review describes the unique aspects of ED in the HF population.

Simvastatin improves diabetes-induced coronary endothelial dysfunction

3-Hydroxy-3-methylglutaryl CoA reductase inhibitors decrease cardiovascular morbidity in diabetic patients, but the mechanism is unclear. We studied the actions of simvastatin (SIM) in enhancing NO bioavailability and reducing oxidative stress in coronary vessels from diabetic rats and in rat coronary artery endothelial cells (RCAEC) exposed to high glucose. Coronary arteries isolated from diabetic rats showed decreases in acetylcholine (ACh)-mediated maximal relaxation from 81.0 +/- 4.5% in controls to 43.5 +/- 7.6% at 4 weeks and 22.3 +/- 0.6% at 10 weeks of diabetes. This effect was associated with oxidative stress in coronary vessels as shown by dichlorofluorescein (DCF) imaging and nitrotyrosine labeling. Diabetes also reduced trans-coronary uptake of [(3)H]l-arginine. Supplemental l-arginine (50 mg/kg/day p.o.) did not improve coronary vasorelaxation to ACh. However, SIM treatment (5 mg/kg/day subcutaneously) improved maximal ACh relaxation to 65.8 +/- 5.1% at 4 weeks and 47.1 +/- 3.9% at 10 weeks. Coronary arteries from rats treated with both SIM and l-arginine demonstrated the same maximal relaxation to ACh (66.1 +/- 3%) as SIM alone. Mevalonate and l-NAME (N(omega)-nitro-l-arginine methyl ester hydrochloride) inhibited the response to ACh in SIM-treated diabetic rats. Coronary arteries from all groups relaxed similarly to sodium nitroprusside. SIM increased endothelial NO synthase protein levels and blocked diabetes-induced increases in DCF and nitrotyrosine labeling in diabetic coronary vessels. SIM treatment restored normal NO levels in media from high-glucose-treated RCAEC and plasma of diabetic rat. Treatment with SIM or the NADPH oxidase inhibitor apocynin also blocked high-glucose-induced increases in reactive oxygen species and superoxide formation in RCAEC. Taken together, these data suggest that SIM improves diabetes-induced coronary dysfunction by reducing oxidative stress and increasing NO bioavailability.

Impaired endothelium-dependent and -independent vasodilation in elderly patients with chronic heart failure

BACKGROUND

Impaired endothelium-dependent and independent vasodilator responses in chronic heart failure (CHF) have been well described. Previous studies involved younger patients and omitted medications prior to study.

AIMS

We explored if new therapeutic interventions would restore vasodilator responses in typical patients with chronic heart failure.

METHODS AND RESULTS

24 patients and 15 controls were recruited, patients were maintained on their usual medications. Forearm blood flow responses were measured by venous occlusion plethysmography in response to incremental doses of sodium nitroprusside (SNP) (6, 9 and 12 nmol/min), acetylcholine (ACH) (120, 180 and 240 nmol/min), angiotensin II (AII) (1, 10 and 100 nmol/min) and N(g)-Nitro-L-arginine methyl ester (L-NAME) (1, 2 and 4 nmol/min) infused into the non-dominant brachial artery. FBF responses to SNP were impaired in patients compared with controls (13.7(9.9,17.4) vs. 24.8(18.6,30.9)) arbitrary units, P<0.001). Similarly FBF responses to ACH were reduced in patients compared with controls (7.5(4.2,10.9) vs. 24.8(16.4,33.2)) arbitrary units, P<0.001. Decreased FBF was noted in response to AII and L-NAME but was significant only for AII and did not differ between groups.

CONCLUSIONS

In elderly patients with CHF, endothelium-dependent and independent vasodilator responses were blunted compared with controls. Defects in nitric oxide bioavailability and smooth muscle responsiveness are not reversed by modern medical management of the heart failure syndrome.

Why do patients with heart failure suffer from erectile dysfunction? A critical review and suggestions on how to approach this problem

Chronic heart failure (HF) is an increasingly common cardiovascular disorder. The goal of health-care providers is to optimize quality of life in this population, including sexual health. Up to 75% of patients with HF report erectile dysfunction (ED). As HF is a condition with distinct physiologic sequelae, some unique organic and psychological factors contributing to ED in this patient population have been identified, along with risk factors common to the development of coronary artery disease, HF and ED. This review describes contributing factors to ED in the setting of HF and highlights treatment considerations for this distinct patient population.

Effects of Heat Stress on Thermoregulatory Responses in Congestive Heart Failure Patients

Background— Clinical observations suggest that tolerance to heat stress may be impaired in patients with cardiovascular diseases, particularly those associated with impaired ventricular function and congestive heart failure (CHF). However, thermoregulatory function during a controlled heat stress challenge in patients with CHF has not been studied.

Methods and Results— To test the hypothesis that thermoregulatory responses are attenuated in such patients, we assessed cutaneous vasodilation and sweat rate in patients with stable class II–III CHF and in matched healthy subjects during passive whole-body heating. Whole-body heating induced a similar increase in internal temperature (≈0.85°C) in both groups. The sweating responses in patients with CHF were not significantly different from that in control subjects. In contrast, the elevation in forearm cutaneous vascular conductance in patients with CHF was reduced by nearly 50% relative to the control subjects (3.8±0.8 versus 6.9±1.0 mL/100 mL tissue per minute per 100 mm Hg, P =0.04). Moreover, maximal cutaneous vasodilator capacity to direct local heating in patients with CHF was also significantly lower than in control subjects, suggesting that vascular remodeling may be limiting cutaneous vasodilation during hyperthermia.

Conclusions— These observations suggest that patients with CHF exhibit attenuated cutaneous vasodilator responses to both whole-body and local heating, whereas sweating responses are preserved. Attenuated cutaneous vasodilation may be a potential mechanism for heat intolerance in patients with CHF.

The endopeptidase inhibitor, candoxatril, and its therapeutic potential in the treatment of chronic cardiac failure in man

Candoxatril (UK-79300) is the orally-active prodrug of candoxatrilat (UK-73967), the active enantiomer of (+/-)candoxatrilat (UK-69578), a potent neutral endopeptidase (NEP) inhibitor. This article describes the rationale behind the use of such a drug in the treatment of chronic heart failure in man. It further describes the pharmacokinetics and pharmacodynamics of candoxatril in normal healthy individuals and in patients with chronic cardiac failure. In addition, we describe the initial results comparing candoxatril with furosemide and captopril in human heart failure.

Impaired Vasoreactivity in End-Stage Heart Failure Patients on Intravenous Inotropic Support

BACKGROUND

Vasoreactivity is known to be impaired in heart failure patients; however, it has not been determined whether standard medical therapy for end-stage heart failure patients (ES-HF) ameliorates this impairment. Therefore, we sought to investigate flow-mediated dilation (FMD) responses in ES-HF with normal or near normal cardiac indices from continuous inotropic support.

METHODS AND RESULTS

Vascular ultrasound was used to assess FMD responses to isometric exercise and cuff occlusion in 15 ES-HF patients and 5 control subjects (C). ES-HF patients had significant hyperemic response to maximal exercise (P < .05), which was blunted relative to C (ES-HF; 84 +/- 21 mL/min versus C; 299 +/- 85 mL/min, P < .05). ES-HF patients did not show a significant hyperemic response to submaximal exercise. C had a significant increase in arterial diameter that exceeded ES-HF after both maximal (C; 8 +/- 1% versus. ES-HF; -0.9 +/- 0.86%, P < .05) and submaximal exercise (C; 6 +/- 1% versus ES-HF; 0.57 +/- 1%, P < .05). FMD responses at similar absolute workloads showed that both the mean hyperemic response and the change in arterial diameter were significantly greater in C. After cuff occlusion, the mean hyperemic response for ES-HF was again significantly blunted compared with C (ES-HF; 117 +/- 26% versus C; 352 +/- 86%, P < .05). After cuff occlusion, arterial diameter in C significantly increased in response to hyperemia, whereas ES-HF patients had a paradoxical vasoconstrictive response (C; 10.7 +/- 1.1% versus ES-HF; -5.3 +/- 1.5%, P < .05).

CONCLUSION

Peripheral vasoreactivity in response to either maximal exercise, submaximal exercise, or hyperemic stimuli is impaired in ES-HF patients with normal resting cardiac outputs.

Inhibition of angiotensin-converting enzyme and phosphodiesterase type 5 improves endothelial function in heart failure

ACE (angiotensin-converting enzyme) inhibitors and PDE5 (phosphodiesterase type 5) inhibitors have each been reported to improve endothelial function in cardiovascular disease patients, but the comparative and combined effects of these two classes have not been studied previously. We sought to characterize the acute effects of ramipril alone, sildenafil alone, or their combination on endothelial function in patients with CHF (chronic heart failure). CHF subjects (n=64) were randomized to receive placebo, 10 mg of ramipril alone, 50 mg of sildenafil alone or a combination of ramipril and sildenafil in a double-blind manner. FMD (flow-mediated dilation) of the brachial artery was determined by high-resolution ultrasound imaging before and at 1, 2 and 4 h after administration of the study drug. Ramipril alone increased FMD at 4 h compared with placebo (+2.3+/-1.3%, P=0.02). Sildenafil alone increased FMD at 1, 2 and 4 h compared with placebo (+3.9+/-1.4, +4.6+/-1.8 and +3.7+/-1.3% respectively, all P<0.02). Sildenafil in combination with ramipril increased FMD at 1, 2 and 4 h when compared with placebo (+3.5+/-1.5, +4.5+/-1.8 and +4.8+/-1.3% respectively, all P<0.03). Ramipril and sildenafil both acutely improved FMD in patients with CHF, with additive effects evident at 4 h during combination therapy. Therefore further work to characterize chronic effects of combined ACE and PDE5 inhibition on endothelial function are warranted.

Endothelium-ameliorating effects of statin therapy and coenzyme Q10 reductions in chronic heart failure

Although not currently indicated for chronic heart failure (CHF), statins have been associated with improved outcome in retrospective analysis. However, statin therapy reduces plasma levels of coenzyme Q(10) (ubiquinone), which may have adverse effects on heart failure states. We hypothesized that atorvastatin treatment improves endothelial function in patients with chronic heart failure independent of LDL-cholesterol alterations. Furthermore, we assessed how reductions in coenzyme Q(10) levels impact on potentially improved endothelial function. Twenty-four patients with stable, symptomatic heart failure (New York Heart Association Class II or III) and a left ventricular ejection fraction <40% were randomised to 40 mg atorvastatin or placebo for 6 weeks and crossed over to the other treatment arm for a further 6 weeks, after a 2-week wash out. Forearm resistance vessel function was assessed by venous occlusion plethysmography during infusion of acetylcholine (ACh), sodium nitroprusside (SNP), and N(G)-monomethyl-L-arginine (L-NMMA) into the brachial artery. Atorvastatin treatment lowered triglycerides, LDL-cholesterol and coenzyme Q(10) levels (all p<0.001) and improved endothelium-dependent vasodilatation during acetylcholine infusion (p=0.015). Endothelium-dependent forearm blood flow improvements correlated with reductions in coenzyme Q(10) levels (p=0.011), but not with LDL-cholesterol levels (p=0.084). Coenzyme Q(10) remained the significant variable predicting improvement in NO dependent endothelial function after adjusting for LDL-cholesterol levels (p=0.041). In conclusion, short-term atorvastatin therapy improved endothelial function in chronic heart failure patients. Further studies are required to determine whether coenzyme Q(10) reductions are limiting the maximum favourable effects of statin therapy on the microcirculation.

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.

Effect of the Asp298 variant of endothelial nitric oxide synthase on survival for patients with congestive heart failure

BACKGROUND

Significant variation exists within the endothelial nitric oxide synthase (NOS3) gene that may influence cardiovascular risk. The Asp298 variant of NOS3 has a shorter half-life in endothelial cells. Given the importance of nitric oxide in the heart failure syndrome, we evaluated the effect of this variant on event-free survival in a population with systolic dysfunction.

METHODS AND RESULTS

Four hundred sixty-nine patients (72% male, 49% ischemic; mean age, 56+/-12 years) with systolic dysfunction (left ventricular ejection fraction < or =0.45) were enrolled in a study of Genetic Risk Assessment of Cardiac Events (GRACE). The polymorphism in exon 7 of NOS3, a G-T transition at position 894 that results in a Glu to Asp amino acid substitution for codon 298, was genotyped and subjects were followed prospectively to the end point of death or heart transplantation. Event-free survival was compared on the basis of the presence (group 1, n=266) or absence (group 2, n=203) of the Asp298 variant. Event-free survival was significantly poorer in patients with the Asp298 variant (percent event-free survival group 1 at 1/2/3 years=78/65/54; group 2=82/72/64, P=0.03). In subset analysis, the adverse impact of the Asp298 variant was primarily in patients with nonischemic cardiomyopathy (group 1=82/73/63; group 2=87/79/71, P=0.03) and was not apparent among patients with ischemic heart disease (group 1=75/59/47; group 2=74/62/54, P=0.71).

CONCLUSIONS

For patients with heart failure caused by systolic function, the Asp298 variant of NOS3 is associated with poorer event-free survival, particularly in patients with nonischemic cardiomyopathy.

Potential role of type 5 phosphodiesterase inhibition in the treatment of congestive heart failure

Endothelial dysfunction is associated with impairment of aerobic capacity in patients with heart failure and may play a role in the progression of disease. Impaired endothelium-dependent vasodilation in patients with heart failure can be attributed to decreased bioavailability of nitric oxide and attenuated responses to nitric oxide in vascular smooth muscle. Impaired vasodilation in response to nitric oxide derived from vascular endothelium or organic nitrates in vascular smooth muscle may be related in part to increased degradation of the second messenger cyclic guanosine monophosphate by type 5 phosphodiesterase. Sildenafil, a specific type 5 phosphodiesterase inhibitor currently approved for the treatment of erectile dysfunction, has been shown to acutely enhance endothelium-dependent vasodilation in patients with heart failure. Further studies are warranted to characterize the safety and efficacy of type 5 phosphodiesterase inhibition in the treatment of chronic heart failure.

Nitric oxide production is maintained in exercising swine with chronic left ventricular dysfunction

Left ventricular (LV) dysfunction caused by myocardial infarction (MI) is accompanied by endothelial dysfunction, most notably a loss of nitric oxide (NO) availability. We tested the hypothesis that endothelial dysfunction contributes to impaired tissue perfusion during increased metabolic demands as produced by exercise, and we determined the contribution of NO to regulation of regional systemic, pulmonary, and coronary vasomotor tone in exercising swine with LV dysfunction produced by a 2- to 3-wk-old MI. LV dysfunction resulted in blunted systemic and coronary vasodilator responses to ATP, whereas the responses to nitroprusside were maintained. Exercise resulted in blunted systemic and pulmonary vasodilator responses in MI that resembled the vasodilator responses in normal (N) swine following blockade of NO synthase with N(omega)-nitro-L-arginine (L-NNA, 20 mg/kg iv). However, L-NNA resulted in similar decreases in systemic (43 +/- 3% in N swine and 49 +/- 4% in MI swine), pulmonary (45 +/- 5% in N swine and 49 +/- 4% in MI swine), and coronary (28 +/- 4% in N and 35 +/- 3% in MI) vascular conductances in N and MI swine under resting conditions; similar effects were observed during treadmill exercise. Selective inhibition of inducible NO synthase with aminoguanidine (20 mg/kg iv) had no effect on vascular tone in MI. These findings indicate that while agonist-induced vasodilation is already blunted early after myocardial infarction, the contribution of endothelial NO synthase-derived NO to regulation of vascular tone under basal conditions and during exercise is maintained.

T-1032, a novel phosphodiesterase type 5 inhibitor, increases the survival of cardiomyopathic hamsters

To evaluate the influence of T-1032 (methyl2-(4-aminophenyl)-1,2-dihydro-1-oxo-7-(2-pyridylmethoxy)-4-(3,4,5-trimethoxyphenyl)-3-isoquinoline carboxylate sulfate), a potent and relatively selective phosphodiesterase 5 inhibitor, on chronic heart failure, we examined the acute hemodynamic profile of T-1032 and its chronic effect on the survival of Bio 14.6 cardiomyopathic hamsters. In the acute study, T-1032 (1, 10, 100 microg/kg) was administered intravenously by means of a dose-escalating procedure in 55-week-old hamsters. T-1032 significantly reduced both the right and left ventricular end-diastolic pressure in a dose-dependent manner. T-1032 modestly reduced the systemic arterial pressure at the highest dose (100 microg/kg i.v.). T-1032 did not change the heart rate or left ventricular dp/dt(max). In the survival study, chronic administration of T-1032 (50 and 500 ppm in a diet) increased survival, and the survival rate was 24.2%, 45.4% and 48.5% in the control, 50 and 500 ppm-treated groups, respectively. The median survival was 55, 58 and 58 weeks in control, 50 and 500 ppm-treated groups, respectively. Analysis of the survival curves revealed that T-1032 (500 ppm) significantly increased the survival of these hamsters (P<0.05 vs. control). It was concluded that T-1032 had beneficial hemodynamic effects on heart failure in Bio 14.6 cardiomyopathic hamsters, and the favorable hemodynamic changes induced by T-1032 were partly related to the increase in the survival of these hamsters. Phosphodiesterase type 5 inhibitors may have therapeutic potential for the treatment of chronic heart failure.

Bradykinin infusion in chronic cardiac failure and the effects of captopril

BACKGROUND

Patients with chronic cardiac failure (CCF) have abnormal vascular responses. Bradykinin (BK) is thought to contribute to the vasodilator effects of ACE inhibitors, but the effect of BK itself in patients with CCF has not been examined.

METHODS

We studied the responses to infused BK at 10, 30 and 100 pmol min(-1) in patients with CCF (n=10) and controls (n=10). The slope of the dose-response curve was used for comparisons between the groups. Forearm blood flow (FBF) was measured by venous occlusion plethysmography.

RESULTS

Following BK, vasodilatation was observed in both groups as the slopes were positive in all, but the difference between the groups was not significant (P=0.77). The study was repeated with the co-administration of 4 micromol min(-1) of N(G)-monomethyl L-arginine (L-NMMA). The vasodilator response to BK was reduced in both groups, and the effect was somewhat greater in the patient group (P=0.23). The vasodilator response to the endothelium-independent vasodilator sodium nitroprusside was slightly less in the patient group (P=0.08). The patients only then underwent repeat infusion of BK before and after a single oral dose of captopril 12.5 mg or placebo. Following captopril, the vasodilator response to BK was unchanged when compared to placebo (difference between slopes, P=0.53).

CONCLUSIONS

BK produces dose-dependent vasodilatation in both patients with CCF and controls; there was no difference in the responses, which were antagonised by L-NMMA and therefore in part NO (endothelium)-dependent. The responses were also unchanged after administration of an ACE inhibitor (captopril).

Preservation of venous endothelial function in the forearm venous capacitance bed of patients with chronic heart failure despite arterial endothelial dysfunction

OBJECTIVES

The goal of this study was to assess whether endothelial dysfunction occurs in the forearm venous capacitance bed of patients with chronic heart failure (CHF) and to determine the role of nitric oxide (NO) in modulating venous tone.

BACKGROUND

Control of venous tone is crucially important in CHF. More than 70% of blood volume lies in the venous capacitance beds. Therefore, small changes in venous tone may markedly affect cardiac filling pressures and cardiac output.

METHODS

Venous tone was measured using radionuclide forearm venous plethysmography in 24 patients with CHF and 16 age-matched controls. The effect of basal NO activity on venous tone was assessed by infusing N-monomethyl-L-arginine 12 mg/min and stimulated NO using carbachol 15 microg/min. Brachial artery flow-mediated dilation was assessed by ultrasonic wall-tracking.

RESULTS

Blockade of basal NO release caused a significant and similar venoconstriction in patients (9.6 +/- 1.8%, p < 0.01) and controls (6.6 +/- 1.7%, p < 0.01). Carbachol-induced venodilation was significant and similar in patients (36.8 +/- 3.9%, p < 0.001) and controls (40.7 +/- 3.9%, p < 0.001). Brachial artery flow-mediated dilation was impaired in patients compared with controls (2.0 +/- 0.6% vs. 7.5 +/- 2.5%, p < 0.01).

CONCLUSIONS

Our data indicate that, despite marked impairment of the function of the arterial endothelium, there is preservation of both basal and stimulated NO release in the forearm venous capacitance bed. This may provide important insights into mechanisms of endothelial dysfunction in CHF and the potential for novel therapy.

Blunted peripheral vasodilatory response is a hallmark of progressive deterioration in mild to moderate congestive heart failure

BACKGROUND

Several reports have shown that dilatory response to acetylcholine (ACh) and nitroprusside (SNP) is blunted in the limb vasculature in patients with congestive heart failure (CHF). However, it is not yet known whether this vascular dysfunction is related to clinical outcome. We have examined the relationship between peripheral vasodilatory response and prognosis of CHF.

METHODS AND RESULTS

A total of 46 patients with mild to moderate CHF were enrolled (mean age 56 years). Changes in forearm blood flow (FBF) during intra-arterial infusion of ACh and SNP were determined by plethysmography. FBF changes above baseline for each dose were cumulated and used as an index of endothelium-dependent (ACh) response and endothelium-independent (SNP) response, respectively. During the follow-up period (mean 32 months), 9 patients were admitted to the hospital for treatment of worsening refractory CHF, and 6 patients died suddenly or developed life-threatening arrhythmia. By Kaplan-Meier analysis, when all cardiac events were included, no significant differences were observed between any levels of vascular response in terms of prognosis. However, when deterioration events were analyzed separately, patients with SNP responses below the median (7.4 mL/min/dL) had significantly higher rates of hospital admission caused by worsening CHF than those with above the median responses (P <.05). This relationship was not found between ACh response and clinical outcome. By Cox multivariate analysis, blunted vasodilatory response to SNP was a significant predictor of worsening CHF (chi(2) = 3.95; P <.05).

CONCLUSION

This study has shown that patients with mild to moderate CHF showing a blunted vascular response to SNP rather than ACh were admitted to the hospital more frequently because of deterioration of CHF. This finding suggests that changes in vascular smooth muscle and/or vascular structure in the peripheral vasculature may be a critical element in the worsening of CHF.

No evidence for functional involvement of 5-HT2B receptors in serotonin-induced vasodilatation in the human forearm

The receptor involved in the serotonin (5-hydroxytryptamine [5-HT])-induced vasodilatation in the human forearm has not yet been identified. Experimental data point to the 5-HT2B receptor located on the endothelium. RS-127445 (2-amino-4-(4-fluoronaphthyl-1-yl)-6-isopropylpyrimidine) is a novel potent and selective 5-HT2B receptor antagonist. The effect of oral RS-127445 (500 mg) on 5-HT-induced vasodilatation was studied in a double-blind, randomized, placebo-controlled, crossover study in six healthy volunteers. On each study day 5-HT (0.5 ng/kg/min) was infused into the brachial artery for 8 min, before drug administration and at intervals of 20, 65, 110, 230, and 470 min after oral ingestion. At each infusion, plasma samples for study drug assay were taken and forearm blood flow was assessed using venous occlusion plethysmography. Although (log) drug concentrations exceeded pKi, there was no correlation between RS-127445 concentrations and 5-HT-induced vasodilatation. 5-HT-induced vasodilatation did not differ between treatments and time points. It appears that there is no functional involvement of 5-HT2B receptors in 5-HT-mediated vasodilatation in the human forearm.

Acute type 5 phosphodiesterase inhibition with sildenafil enhances flow-mediated vasodilation in patients with chronic heart failure

OBJECTIVES

To determine the acute effects of type 5 phosphodiesterase inhibition with sildenafil on flow-mediated vasodilation in the brachial artery of patients with chronic heart failure.

BACKGROUND

Impaired endothelium-dependent, flow-mediated vasodilation in patients with heart failure is partly attributable to hyporesponsiveness of cyclic guanosine monophosphate (cGMP) mediated vasorelaxation effector mechanisms in vascular smooth muscle. The effect of inhibition of cGMP degradation with sildenafil, a specific type 5 cGMP phosphodiesterase inhibitor, on flow-mediated dilation in heart failure is unknown.

METHODS

Flow-mediated vasodilation after release of 1, 3 and 5 min of transient arterial occlusion was measured in the brachial artery with high resolution two-dimensional ultrasound imaging in 48 patients with chronic heart failure before and 1 h after randomized, double-blind assignment to a single oral dose of sildenafil 12.5, 25 or 50 mg or matching placebo.

RESULTS

In response to oral administration of a single dose of study drug, the change in flow-mediated vasodilation after release of 1, 3 and 5 min of arterial occlusion was significantly greater in patients receiving sildenafil 25 mg (3.3 +/- 1.9, 3.8 +/- 1.8 and 4.0 +/- 1.8%, respectively, p < 0.05) and patients receiving sildenafil 50 mg (3.7 +/- 1.3, 4.1 +/- 1.1, 3.9 +/- 1.3%, respectively, p < 0.05) than that of patients receiving placebo (0.7 +/- 1.1, 0.2 +/- 1.2, 0.6 +/- 0.8%, respectively).

CONCLUSIONS

Acute type 5 phosphodiesterase inhibition with sildenafil 25 and 50 mg increases endothelium-dependent, flow-mediated vasodilation in patients with chronic heart failure when compared with placebo.

Nitric oxide as a metabolic regulator during exercise: effects of training in health and disease

1. Accumulating animal and human data suggest that nitric oxide (NO) is important for both coronary and peripheral haemodynamic control and metabolic regulation during performance of exercise. 2. While still controversial, NO of endothelial origin is thought to potentiate exercise-induced hyperaemia, both in the peripheral and coronary circulations. The mechanism of release may include both acetylcholine derived from the neuromuscular junction and vascular shear stress. 3. A splice variant of neuronal nitric oxide synthase (NOS), nNOSmicro, incorporating an extra 34 amino acids, is expressed in human skeletal muscle. In addition to being a potential modulator of blood flow, skeletal muscle-derived NO is an important regulator of muscle contraction and metabolism. In particular, recent human data indicate that NO modulates muscle glucose uptake during exercise, independently of blood flow. 4. Exercise training in healthy individuals promotes adaptations in the various NO systems, which can increase NO bioavailability through a variety of mechanisms, including increased NOS enzyme expression and activity. Such adaptations likely contribute to increased exercise capacity and protection from cardiovascular events. 5. Cardiovascular risk factors, including hypercholesterolaemia, hypertension, diabetes and smoking, as well as established disease, are associated with impairment of the various NO systems. Given that NO is an important signalling mechanism during exercise, such impairment may contribute to limitations in exercise capacity through inadequate coronary or peripheral blood delivery and via metabolic effects. 6. Exercise training in individuals with elevated cardiovascular risk or established disease can increase NO bioavailability and may represent an important mechanism by which exercise training provides benefit in the setting of secondary prevention.

Exhaled nitric oxide during incremental and constant workload exercise in chronic cardiac failure

BACKGROUND

Nitric oxide (NO) is present in exhaled breath and produced by the pulmonary vascular endothelium as a potent vasodilator. Exercise is normally associated with pulmonary vasodilatation and a decrease in pulmonary vascular resistance to accommodate the increase in cardiac output. If production of NO is impaired in patients with chronic congestive cardiac failure (CCF), this might contribute to their exercise intolerance.

PATIENTS AND METHODS

We quantified NO production (V NO) in 12 patients with chronic stable CCF and 12 controls, at rest and during incremental cardiopulmonary exercise on a treadmill, and at a later date during constant workload exercise.

RESULTS

Patients had reduced V NO compared with controls during incremental exercise [381 (180) vs. 777 (275) nL min-1; mean (SD); P < 0.0001] but at constant workload V NO was similar between the two groups [353 (124) vs. 389 (189) nL min-1; P = 0.25]. Plasma levels of nitrate, the stable end-product of NO production, were significantly higher in patients [resting value 46.1 (21.6) vs. 23.0 (10.0) microM; P = 0.004] and were not influenced by exercise.

CONCLUSION

Impaired NO-mediated pulmonary vasodilatation does not appear to contribute to exercise limitation in CCF. Alternatively, the lower NO production observed during maximal exercise in the patient group compared with controls may reflect a reduced incremental response of a system that is already abnormally activated in heart failure.

Peripheral vascular remodeling in chronic heart failure: clinical relevance and new conceptualization of its mechanisms

Increased peripheral vascular tone is a critical factor in the deterioration of clinical stage and symptoms in chronic congestive heart failure (CHF) because of increased cardiac afterload and decreased nutritive skeletal muscle blood flow. Endothelial function as represented by nitric oxide (NO) production shows significant attenuation with the progression of clinical severity of CHF as determined by New York Heart Association class and exercise capacity parameters. This endothelial dysfunction emerges in the early stages of CHF. In the advanced stage of the condition, both endothelium-dependent and endothelium-independent dilator mechanisms are impaired in limb resistance vessels. This occurs because vascular endothelial function, especially NO production, is an important factor in the regulation of vasodilatory function, as well as making an important contribution to vascular structure. Furthermore, although such vasodilatory circulating factors as natriuretic polypeptides and newly discovered adrenomedullin are increased in heart failure, the vasodilatory potency of these polypeptide hormones in the limb vascular bed is significantly blunted. These observations suggest that peripheral circulatory failure in CHF is caused not only by simple arterial muscle constriction, but also by structural and functional changes, including receptor and postreceptor levels in the vasculature. This vascular remodeling may be an important mechanism underlying vasodilatory failure in both limb conduit and intraskeletal muscle vessels and may contribute significantly to left ventricular dysfunction and exercise intolerance in patients with heart failure.