Attenuated endothelium-dependent peripheral vasodilation and clinical characteristics in patients with chronic heart failure

Effect of inorganic nitrate on exercise capacity, mitochondria respiration, and vascular function in heart failure with reduced ejection fraction

This is the largest study to date to examine the effects of inorganic nitrate supplementation in patients with heart failure with reduced ejection fraction (HFrEF) and the first to include measures of vascular function and mitochondrial respiration. Although daily supplementation increased plasma nitrite, our data indicate that supplementation with inorganic nitrate as a standalone treatment is ineffective at improving exercise capacity, vascular function, or mitochondrial respiration in patients with HFrEF.

Effects of exercise training on neurovascular control and skeletal myopathy in systolic heart failure

Neurohormonal excitation and dyspnea are the hallmarks of heart failure (HF) and have long been associated with poor prognosis in HF patients. Sympathetic nerve activity (SNA) and ventilatory equivalent of carbon dioxide (VE/VO2) are elevated in moderate HF patients and increased even further in severe HF patients. The increase in SNA in HF patients is present regardless of age, sex, and etiology of systolic dysfunction. Neurohormonal activation is the major mediator of the peripheral vasoconstriction characteristic of HF patients. In addition, reduction in peripheral blood flow increases muscle inflammation, oxidative stress, and protein degradation, which is the essence of the skeletal myopathy and exercise intolerance in HF. Here we discuss the beneficial effects of exercise training on resting SNA in patients with systolic HF and its central and peripheral mechanisms of control. Furthermore, we discuss the exercise-mediated improvement in peripheral vasoconstriction in patients with HF. We will also focus on the effects of exercise training on ventilatory responses. Finally, we review the effects of exercise training on features of the skeletal myopathy in HF. In summary, exercise training plays an important role in HF, working synergistically with pharmacological therapies to ameliorate these abnormalities in clinical practice.

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.

Effects of 5'-phosphodiesterase four-week long inhibition with sildenafil in patients with chronic heart failure: a double-blind, placebo-controlled clinical trial

BACKGROUND

The effects of chronic inhibition of 5'-phosphodiesterase with sildenafil on functional capacity, ventilatory efficiency, oxygen uptake, pulmonary hypertension, and endothelial function in chronic heart failure (CHF) are unknown.

METHODS

We conducted a randomized, double-blind, placebo-controlled trial to assess the acute (1 hour after 50 mg by mouth) and chronic (4 weeks after 50 mg 3 times per day by mouth) effects of sildenafil in outpatients with CHF. The outcomes were cardiopulmonary exercise test parameters (chronic effect), echocardiographic-derived pulmonary artery systolic pressure, and plethysmography-derived forearm blood flow (acute and chronic effects).

RESULTS

Nineteen patients with CHF (48 +/- 12 years) with an ejection fraction of 28% +/- 6% were studied. Patients who received sildenafil (n = 11) showed improved maximal oxygen uptake, ventilatory efficiency, and oxygen uptake kinetics. Sildenafil decreased pulmonary artery systolic pressure levels at 60 minutes and at 4 weeks compared with changes after placebo (P = .004 for group and time interaction). Improvement in ventilatory efficiency was positively associated with reductions in pulmonary artery systolic pressure. Patients allocated to placebo demonstrated a trend toward decreased forearm blood flow after reactive hyperemia, whereas this remained unchanged in patients allocated to sildenafil.

CONCLUSIONS

Sildenafil administration for 4 weeks in stable outpatients with CHF improves functional capacity, ventilatory efficiency, oxygen uptake kinetics, and pulmonary hypertension. These effects may be mediated in part by improvements in endothelial function.

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.

ETBreceptor dependent alteration in aortic responses to ET-1 in the cardiomyopathic hamsterThis paper is one of a selection of papers published in this Special issue, entitled Second Messengers and Phosphoproteins—12th International Conference

The aim of this study was to verify whether an alteration in the aortic endothelin-1 (ET-1) response takes place in UM-X7.1 cardiomyopathic hamsters. Our results showed that ET-1 (10−12– 10−5 mol/L) induces dose-dependent sustained increases in tension in the intact and endothelium denuded aortas from both normal and cardiomyopathic hamsters. The EC50values of ET-1 of both intact and endothelium denuded aortas of normal hamsters were similar (2.2 × 10−9 mol/L and 1.8 × 10−9 mol/L, respectively). However, in cardiomyopathic hamsters, the EC50of ET-1 in intact aortas was higher (1.5 × 10−8 mol/L) than that of the endothelium denuded preparations (2.7 × 10−9 mol/L). The EC50of ET-1 in normal and cardiomyopathic hamster denuded aortas were similar. However, the EC50of ET-1 in intact aortas of cardiomyopathic hamster was higher (1.5 × 10−8 mol/L) than that of normal hamsters (2.2 × 10−9 mol/L). Pre-treatment with the ETAreceptor antagonist ABT-627 (10−5 mol/L) of intact and endothelium denuded aortas from both normal and cardiomyopathic hamsters significantly prevented ET-1 (10−7 mol/L) from inducing an increase in tension. Pre-treatment with the ETBreceptor antagonist A-192621 (10−5 mol/L) had no effect on the ET-1-induced increase in tension in endothelium denuded aortas of both normal and cardiomyopathic hamsters, as well as in intact preparations of normal animals. However, blockade of the ETBreceptors in intact aortas of cardiomyopathic hamsters significantly (p < 0.001) potentiated the ET-1-induced increase in tension. In summary, an attenuation of the contraction response to ET-1 was found in UM-X7.1 cardiomyopathic hamsters when compared with normal age-matched hamsters. This alteration of the ET-1 effect in the aortas of cardiomyopathic hamsters seems to be dependent on the presence of the endothelium and could be due, in part, to an increase in the contribution of endothelial ETBreceptors to relaxation, which in turn acts as a physiological depressor of ET-1 vasoconstriction. Our results suggest that an increase in the endothelium ETBreceptor density may play a role in the development of hypotension in UM-X7.1 cardiomyopathic hamsters.

Effect of an exercise training program on endothelial dysfunction in diabetic and non-diabetic patients with severe chronic heart failure

BACKGROUND

Endothelial dysfunction is found both in patients with chronic heart failure and in patients with insulin-treated type 2 diabetes mellitus. This endothelial dysfunction leads to a significant reduction in endothelium-derived vasodilation. Physical exercise can have a positive effect on endothelial dysfunction in patients with coronary artery disease, chronic heart failure and diabetes mellitus. It is not clear, however, whether an exercise program influences endothelial function in diabetics with chronic heart failure. Our study was thus aimed at investigating whether a special exercise program would affect endothelial function. Comparisons were made with insulin-treated type 2 diabetics and with non-diabetics suffering from chronic heart failure.

METHODS

42 patients with severe chronic heart failure (LVEF < or = 30%), insulin-dependent diabetics (n=20, mean age 67+/-6 yrs, 16 male, 4 female), non-diabetics (n=22, mean age 68+/-10 yrs, 20 male, 2 female) participated in a 4-week exercise program consisting of ergometer and special muscle strength training. Before (T1) and at the end (T2) of the training program endothelium-dependent and endothelium-independent vasodilatory capacity were assessed by brachial artery diameter measurement.

RESULTS

At the end of the training program, there were no significant results within the two groups. The endothelium-dependent vasodilation changed between T1 and T2 as follows: In the diabetic group, the endothelium-dependent vasodilation at T1 and T2 was 5.1+/-3.6 and 4.9+/-2.5%, respectively. For the non-diabetics, the endothelium-dependent vasodilation was 6.8+/-4.5 and 7.6+/-4.0% at T1 and T2, respectively. The endothelium-independent vasodilation in the diabetics was 10.5+/-5.6 at T1 and dropped to 8.7+/-4.1% at T2. The results for the non-diabetics were 13.2+/-5.8 and 12.3+/-6.3% at T1 and T2, respectively. The LVEF in the diabetics was 24.2+/-3.4% at T1, increasing to 27.8+/-5.8% at T2. In the non-diabetics, the LVEF was 22.9+/-3.8 at T1 vs. 28.6+/-6.9% at T2. In the groups of diabetics, the maximum oxygen uptake (VO2-max) was 10.3+/-3.9 at T1 vs. 11.4+/-2.8 ml/kg/min at T2 and in the group of non-diabetics 10.0+/-3.1 vs. 13.5+/-5.0 ml/kg/min. No correlations were found between the change in endothelium-dependent vasodilation and the increase in oxygen uptake.

CONCLUSION

In our study, a program of physical exercise had no influence on endothelium-dependent or endothelium-independent vasodilation in insulin-treated type 2 diabetics or in non-diabetics with considerably reduced ejection fraction. In both groups, however, an exercise-related influence on medical parameters and physical performance could be observed.

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.

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.

Microvascular abnormalities in chronic heart failure: a cross-sectional analysis

OBJECTIVES

Similar to what has been found in hypertension, elevated peripheral resistance in chronic heart failure (CHF) might be related to microvascular constriction and rarefaction. Our objective was to evaluate both structural and functional microvascular changes in patients with CHF in relation to left ventricular function and neurohumoral activation.

METHODS

In 25 patients with mild and severe CHF (New York Heart Association class I-II [n = 11] and class III-IV [n = 14]) and 10 age-matched healthy subjects, we studied microvascular density, diameters, and morphology of the bulbar conjunctiva and skin nailfold using intravital microscopy.

RESULTS

Total conjunctival microvascular density was higher in patients with mild heart failure compared with healthy controls, whereas it was lower in severe heart failure (medians, 6.75, 4.31, and 3.56 mm/mm2, respectively, p < 0.01). In patients with heart failure, venular density was correlated with left ventricular ejection fraction. Nailfold capillary recruitment during postocclusive reactive hyperemia, a measure of functional reserve capacity, was impaired in patients with severe CHF (p < 0.05). Furthermore, in severe CHF, more abnormal capillaries and enlarged diameters were found in the nailfold (p < 0.05).

CONCLUSIONS

In heart failure, several microvascular abnormalities occur that differ, depending on the severity of this condition.

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.

Peripheral vasodilatory dysfunction in adult patients with congenital heart disease and severely elevated pulmonary vascular resistance

Several studies have demonstrated that pulmonary vascular abnormalities precede alterations in aortic circulation downstream in animal models of heart failure. The relationship between increased pulmonary vascular resistance (PVR) and agonist-induced limb vasodilatory response remains unknown in patients with congenital cardiovascular shunt lesions (CSL). The authors hypothesized that patients with CSL and severely elevated PVR will show a defective vasomotor response in the peripheral vascular bed. To examine this hypothesis we measured forearm blood flow (FBF) responses to the endothelium-dependent vasodilator acetylcholine and the endothelium-independent vasodilator sodium nitroprusside. The values for these FBF responses were compared with PVR in adult patients with CSL (n=20) and healthy age- and sex-matched controls (n = 15). When patients with CSL were divided into 2 subgroups by median value of PVR, in the lower PVR subgroup, acetylcholine-induced FBF changes were selectively and significantly lower than in the healthy control group (p <0.05). In the higher PVR subgroup, FBF responses to both acetylcholine and sodium nitroprusside were significantly blunted compared to healthy controls (both p < 0.01). In addition, when FBF changes above baseline for each dose of acetylcholine and sodium nitroprusside were cumulated and used as acetylcholine response and sodium nitroprusside response, the sensitivity and specificity for identifying patients with Eisenmenger's type of CSL was 100% and 80% by acetylcholine response, and 67% and 80% by sodium nitroprusside response, respectively. In conclusion, adult CSL patients with elevated PVR and severe pulmonary arterial hypertension showed generalized vasodilator dysfunction in the forearm vasculature. This result suggests that upper limb resistance vessel dysfunction may be an indicator for advanced stage of adult patients with CSL.

An inhibitor of inducible nitric oxide synthase decreases forearm blood flow in patients with congestive heart failure

OBJECTIVES

The functional activation of inducible nitric oxide synthase (iNOS) was evaluated as a source of nitric oxide (NO) in the forearm of patients with heart failure.

BACKGROUND

Although endogenous NO is normally produced by constitutive NO synthase (cNOS) in patients with congestive heart failure (CHF), expression of iNOS provides an additional source of NO. However, there are no in vivo studies showing functional activation of iNOS in humans.

METHODS

A nonselective NOS inhibitor, N(G)-monomethyl-L-arginine (L-NMMA), and a selective inhibitor of iNOS, aminoguanidine, were administered intra-arterially in graded doses into the brachial arteries of 13 patients with CHF and 10 normal control subjects. Forearm blood flow (FBF) was measured simultaneously in the infused and noninfused arms by plethysmography. Arterial and venous plasma concentrations of nitrite/nitrate (NOx) were measured at baseline and at the highest dose of each drug.

RESULTS

L-NMMA significantly reduced the FBF ratio between the infused and noninfused arms in both the control and patient groups (35 +/- 12% and 34 +/- 10%, respectively; both p < 0.001). Aminoguanidine at the same concentration significantly reduced the ratio in the patient group (15 +/- 9%, p < 0.01), with no change in the control group. The arterial NOx concentration was not affected by either drug; however, venous NOx concentrations were significantly decreased in both the control and patient groups by L-NMMA (18 +/- 5% and 18 +/- 17%, respectively; both p < 0.05) and in the patient group only by aminoguanidine (7 +/- 6%, p < 0.05).

CONCLUSIONS

These findings suggest that NO production in the forearms of patients with CHF is induced partly by iNOS activation, whereas in normal subjects, it can be ascribed to cNOS activation.

Endothelium-derived hyperpolarizing factor : identification and mechanisms of action in human subcutaneous resistance arteries

BACKGROUND

Both a vascular endothelial cytochrome P450 (CYP450) product of arachidonic acid metabolism and the potassium ion (K(+)) have been identified as endothelium-derived hyperpolarizing factors (EDHFs) in animal vascular tissues. We studied the relative importance of EDHF, nitric oxide (NO), and prostacyclin (PGI(2)) as vasodilators in human subcutaneous arteries. We also examined the mechanisms underlying the vasodilator action of EDHF to elucidate its identity.

METHODS AND RESULTS

Subcutaneous resistance arteries were obtained from 41 healthy volunteers. The contribution of EDHF to the vasodilation induced by acetylcholine was assessed by inhibiting production of NO, PGI(2), and membrane hyperpolarization. The mechanisms underlying the relaxation evoked by K(+) and EDHF were elucidated. EDHF was found to account for approximately 80% of acetylcholine-mediated vasorelaxation. Its action was insensitive to the combination of barium and ouabain, whereas barium and ouabain reversed K(+)-mediated vasorelaxation. EDHF-mediated vasorelaxation, however, was sensitive to the phospholipase A(2) inhibitor oleyloxyethyl phosphorylcholine and the CYP450 inhibitor ketoconazole.

CONCLUSIONS

EDHF is the major contributor to endothelium-dependent vasorelaxation in human subcutaneous resistance arteries. A product of phospholipase A(2)/CYP450-dependent metabolism of arachidonic acid and not K(+) is the likely identity of EDHF in human subcutaneous resistance arteries.

Atrial fibrillation impairs endothelial function of forearm vessels in humans

BACKGROUND

Although there have been many studies on the effects of atrial fibrillation (AF) on cardiac function, few studies have been done on its effects on endothelial function. The present study was designed to examine the effects of AF on endothelial function in human subjects.

METHODS AND RESULTS

Changes in forearm blood flow (FBF) induced by acetylcholine and nitroglycerin were measured by using plethysmography in 14 patients with lone AF, 13 patients with AF and underlying heart disease, and 12 normal control subjects. In the patients, these measurements were repeated after cardioversion. Although baseline FBF was the same in the 3 groups, acetylcholine-induced increases in FBF were significantly smaller in both patient groups than in the control group, and FBF increases were particularly depressed in AF patients with underlying heart disease. After restoration of sinus rhythm by cardioversion, FBF response to the highest dose of acetylcholine increased by 46% in patients with lone AF (n = 10) and by 90% in AF patients with underlying heart disease (n = 11). Nitroglycerin-induced vasodilatation was the same in all 3 groups and was not affected by cardioversion.

CONCLUSIONS

These findings suggest that endothelium-dependent vasodilatation is impaired by AF and improves after sinus rhythm is restored.

Contribution of endogenous nitric oxide to basal vasomotor tone of peripheral vessels and plasma B-type natriuretic peptide levels in patients with congestive heart failure

OBJECTIVES

We examined whether a relationship exists between the vasoconstrictive response to endogenous nitric oxide (NO) synthesis inhibition and the severity of heart failure in patients with congestive heart failure (CHF).

BACKGROUND

Controversy exists as to whether the vasoconstrictive response to NO synthesis inhibition in patients with CHF is comparable to that in normal subjects or is enhanced.

METHODS

Forearm blood flow (FBF) and calculated forearm vascular conductance (FVC) were obtained using plethysmography before and after administration of the NO synthesis inhibitor L-NMMA (NG-monomethyl-L-arginine) in 40 patients with CHF due to dilated cardiomyopathy and in 16 normal control subjects. Basal plasma B-type natriuretic peptide (BNP) and nitric oxide concentrations were measured in all subjects.

RESULTS

Plasma BNP and nitrite/nitrate (NOx) levels in the patients group were significantly greater and baseline FBF was significantly less. Administration of L-NMMA significantly decreased FBF and FVC in both groups. The percent changes in FBF (%FBF) and FVC (%FVC) from the baseline after L-NMMA correlated significantly with plasma BNP level (%FBF: r = 0.72; %FVC: r = 0.76; both p < 0.001). Percent changes in both FBF and FVC were greater in patients with BNP > or = 100 pg/ml than in normal subjects; however, in patients with BNP < 100 pg/ml they were comparable to those in normal subjects.

CONCLUSIONS

Vasoconstrictive response to L-NMMA in patients with CHF was preserved or enhanced in proportion to the basal plasma BNP level, indicating a close relationship between the contribution of endogenous NO to basal vasomotor tone and the severity of heart failure.

Effects of tumor necrosis factor-alpha on basal and stimulated endothelium-dependent vasomotion in human resistance vessel

The aim of this study was to determine whether tumor necrosis factor (TNF)-alpha would impair basal and stimulated endothelium-dependent vasomotion in human resistance vessel. Changes in baseline and acetylcholine (ACh)-induced forearm vascular resistance (FVR) were measured plethysmographically before and after a low-dose intraarterial forearm infusion of TNF-alpha according to the following three protocols in healthy volunteers. In the condition without pretreatment, basal FVR was significantly increased by TNF-alpha (from 30.5 +/- 4.8 to 39.9 +/- 5.9 units; p < 0.01), whereas ACh-induced minimal FVR did not differ between pre- and post-TNF-alpha states. In the condition after pretreatment with the cyclooxygenase inhibitor acetylsalicylic acid, although the vascular effects of TNF-alpha on basal FVR appeared to be blocked (37.1 +/- 5.3 vs. 37.6 +/- 5.2; NS), ACh-induced minimal FVR did not differ between pre- and post-TNF-alpha states. In the condition after pretreatment with the nitric oxide (NO) synthase inhibitor N(G)-monomethyl-L-arginine, the vascular effect of TNF-alpha on basal FVR was diminished, and the ACh-induced maximal dilatory response was significantly blunted after TNF-alpha compared with before TNF-alpha (minimal FVR: 30.4 +/- 12.0 vs. 12.3 +/- 4.2 units; p < 0.05). These findings suggest that brief exposure of the human forearm resistance artery to TNF-alpha may increase basal bioavailability of the vasoconstrictor prostaglandin and reduce basal bioavailability of NO. In the stimulated condition, TNF-alpha-induced vascular dysfunction may be overwhelmed by increased NO bioavailability in healthy humans.

Impaired vasodilatation response to amrinone in the forearm of patients with congestive heart failure: role of endothelium-derived nitric oxide

Recent in vitro experiments have shown that amrinone enhances the release of nitric oxide (NO) from the endothelium and induces NO mediated vasodilatation. This in vivo study examined whether amrinone causes vasodilatation mediated by endothelium-derived NO, and whether this effect is attenuated in patients with endothelial dysfunction. Eight patients with congestive heart failure and 10 age- and sex-matched healthy volunteers were studied. Forearm blood flow (FBF) was measured before and during infusion of drugs of acetylcholine, amrinone, and nitroglycerin in incremental doses. After the completion of these measurements, 100 micromol of N(G)-monomethyl-L-arginine (L-NMMA) was infused intraarterially. Thereafter, FBF measurement in response to incremental doses of amrinone was repeated. Infusion of incremental doses of amrinone caused a comparable increase in amrinone plasma concentration in both groups. Baseline FBF was 3.2+/-0.79 ml/min/100 ml in controls vs. 2.91+/-0.79 ml/min/100 ml in patients (p = 0.43). In both groups, FBF increased in response to acetylcholine, amrinone, and nitroglycerin. During infusion of the highest dose of nitroglycerin, FBF was not different between the two groups (p = 0.51); however, FBF during infusion of the highest doses of acetylcholine and amrinone was significantly less in patients than in controls: 9.75+/-2.69 vs. 24.87+/-8.65 ml/min/100 ml (p < 0.001) and 3.79+/-1.21 vs. 7.15+/-2.06 ml/min/100 ml (p < 0.001), respectively. L-NMMA significantly depressed the increase in FBF in response to amrinone in controls, but not in patients. In conclusion, the selective PDE III inhibitor, amrinone, has endothelium-derived NO-mediated vasodilating effects in addition to direct effects. This property may be impaired in patients with endothelial dysfunction.

Endothelial dysfunction in patients with heart failure: relationship to disease severity

BACKGROUND

Heart failure is associated with abnormal endothelium-dependent vasodilation. However, the relationship of this abnormality to heart failure severity has not been well defined.

METHODS AND RESULTS

We used strain-gauge plethysmography to assess forearm blood flow (FBF) responses to endothelium-dependent, endothelium-independent, and reactive hyperemic stimuli in normal subjects (n = 29) and in patients with mild (n = 26) and severe (n = 41) heart failure. FBF responses to intra-arterial methacholine (0.3, 1.5, 3.0 microg/min) were significantly (P < .005) and similarly reduced in patients with mild (2.8 +/- 0.4, 5.9 +/- 0.7, and 7.7 +/- 1.1 mL/min/dL) and severe (2.7 +/- 0.4, 5.4 +/- 0.7, and 6.9 +/- 0.9) heart failure compared with normal subjects (4.5 +/- 0.4, 9.4 +/- 1.0, and 12.0 +/- 1.1). FBF responses to nitroprusside (1, 5, 10 microg/min) were significantly reduced in mild (2.4 +/- 0.3, 6.7 +/- 1.1, and 11.9 +/- 2.0, P < .05) and severe (1.9 +/- 0.2, 5.1 +/- 0.5, and 7.3 +/- 0.9, P < .001) heart failure groups compared with normal subjects (3.8 +/- 0.5, 10.8 +/- 1.2, and 14.9 +/- 1.2). However, FBF responses were reduced to a greater extent (P < .001) in mild heart failure compared with severe heart failure. Peak reactive hyperemia was significantly impaired only in severe heart failure. There was no correlation between methacholine responses and ejection fraction, maximum oxygen consumption, wedge pressure, or serum norepinephrine.

CONCLUSION

Impaired endothelium-dependent vasodilation is present and near maximum in mild heart failure. Endothelial dysfunction may be an early finding in human heart failure.

Acetylcholine but not sodium nitroprusside exerts vasodilation in pulmonary hypertension secondary to chronic congestive heart failure

BACKGROUND

Reduced endothelium-dependent vasodilation contributes to the development of pulmonary hypertension in chronic congestive heart failure (CHF). We investigated pulmonary endothelium-dependent and independent vasodilation in patients with CHF.

METHODS

We studied 42 patients with CHF (age 55 +/- 10, NYHA Classes II-III, left ventricular ejection fraction 27 +/- 10%, mean PAP 29 +/- 12 mmHg). The endothelial vasodilator capacity of pulmonary resistance vessels was assessed by the infusion of acetylcholine into a pulmonary artery branch while measuring the blood flow velocity with a Doppler flow wire. For comparison endothelium-independent vasodilation was measured with the response to sodium nitroprusside. The conductance vessel diameter (4.4 +/- 0.2 mm) was determined by intravascular ultrasound. Acetylcholine was administered at concentrations of 10(-6) to 10(-4) mol/l, sodium nitroprusside was administered at concentrations of 0.125 and 0.25 microg/kg per min. The effects on conductance vessel diameter were investigated in 12 patients by the measurement of diameter and flow velocity following the administration of acetylcholine and sodium nitroprusside.

RESULTS

Acetylcholine markedly increased blood flow velocity (+39 +/- 7% at 10(-4) mol/l; p < .05). This correlated with the baseline PAP (r = 0.58; p < .05) and pulmonary vascular resistance (r = 0.58; p < .05). Sodium nitroprusside caused a small increase in the flow velocity (5 +/- 2% at 0.125, 12 +/- 4% at 0.25 microg/kg per minute; p < .05) that was accompanied by systemic vasodilation. The conductance vessel diameter was unchanged after acetylcholine was administered and was only marginally decreased after the administration of sodium nitroprusside.

CONCLUSIONS

In CHF acetylcholine reveals preserved receptor-mediated endothelial vasodilation, that is positively correlated to pulmonary hypertension, and cannot be reproduced by sodium nitroprusside.

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.

Angiotensin-converting enzyme inhibition restores hepatocyte growth factor production in patients with congestive heart failure

Endothelium-dependent vasodilation is impaired in patients with congestive heart failure. For vascular endothelium, hepatocyte growth factor (HGF) is one of the most potent and specific growth factors, which acts protectively against endothelial dysfunction. HGF production is downregulated by angiotensin II (Ang II) in vitro. We hypothesized that HGF production is impaired as the result of increased Ang II in patients with congestive heart failure, and that if so, the impaired production should be restored with angiotensin-converting enzyme inhibitors (ACE-I). We studied 16 patients with congestive heart failure caused by previous anterior myocardial infarction in whom left ventricular ejection fraction was 35+/-8% (mean+/-SD). Before and approximately 4 weeks after the treatment with ACE-I, blood samples were collected to measure the levels of HGF, Ang II, and brain natriuretic peptide as a biochemical marker for severity of heart failure. We also studied 5 control subjects, in whom heparin increased HGF production to 48+/-5-fold. However, in patients with heart failure, HGF response to heparin was significantly attenuated (24+/-5-fold, P<0.05 vs control). Therapy with ACE-I decreased the levels of Ang II and brain natriuretic peptide and restored HGF production in response to heparin by 43+/-7-fold, comparable to the control response. In conclusion, impaired HGF production was restored after the treatment with ACE-I probably by the mechanism of Ang II suppression. This novel effect of ACE-I may contribute to the clinical improvement in patients with heart failure and thereby may have an important therapeutic implication.

Relation between impairment in nitric oxide pathway and clinical status in patients with congestive heart failure

A dissociation between basal and stimulated release of nitric oxide (NO) has been found in the peripheral vasculature of patients with congestive heart failure. To explore basal and stimulated NO-mediated vasodilation in patients with heart failure of varying severity, three groups of subjects were studied: group 1, eight normal subjects; group 2, six patients with moderate heart failure; and group 3, eight patients with severe heart failure. Forearm blood flow (FBF) was measured by plethysmography in response to local brachial infusion of acetylcholine, N(G)-monomethyl-L-arginine (L-NMMA), sodium nitroprusside (SNP), and noradrenaline (NA). The vasodilating response to acetylcholine was markedly impaired in patients with severe heart failure compared with the other groups, with FBF increasing by 59 +/- 19% in group 3 vs. 220 +/- 64% in group 2 (p < 0.05) and 586 +/- 168% in group 1 (p < 0.01) at 80 microg/min acetylcholine. As compared with controls, vasodilation to SNP was impaired in group 3 but unchanged in group 2. NA caused similar vasoconstrictor response in the three groups, whereas vasoconstriction to L-NMMA was less marked in group 3. These results show that vasodilator responses to both acetylcholine and SNP are impaired in patients with heart failure and that this impairment is related to the clinical severity of heart failure.

Effects of exercise training on limb blood flow in patients with reduced ventricular function

BACKGROUND

Among the factors that contribute to limiting exercise tolerance in chronic heart failure are reduced peripheral blood flow and impaired vasodilatory capacity. Exercise training improves vasodilatory capacity in normal subjects, but controlled studies of exercise training evaluating upper and lower limb blood flow rates have not been performed in patients with reduced ventricular function. Improved vasodilatory capacity could help explain how training increases exercise capacity in these patients.

METHODS

Twenty patients (mean age 55 +/- 6 years) with reduced left ventricular function (mean ejection fraction 32% +/- 6%) after a myocardial infarction were randomized to a 2-month high-intensity residential rehabilitation program or to a control group and were monitored over the subsequent year. Both groups were treated according to current practice with angiotensin-converting enzyme inhibition therapy. Training began 1 month after myocardial infarction. Baseline and postischemic flow rates were measured by plethysmography in both the upper and lower limbs 1 month, 3 months, and 1 year after the infarction. Peak oxygen uptake (VO2) and cardiac output were measured before and after training, and peak VO2 was determined again after 1 year.

RESULTS

After 2 months of training peak VO2 increased 25%, VO2 at the lactate threshold increased 40%, and maximal cardiac output increased from 12.1 +/- 1.6 L/min to 13.9 +/- 2.4 L/min in the exercise group (all p < 0.05), whereas no differences were observed in the control group. At the 1-year follow-up no further increases in peak VO2 were noted in either group, but the higher value persisted in the trained group. However, changes in limb flow rates were poorly related to changes in both peak VO2 and maximal cardiac output. Improvements in baseline and postischemic flow rates occurred mainly in the lower limbs and were observed in the two groups to a similar degree.

CONCLUSION

Exercise training is highly effective in improving exercise capacity in patients with reduced ventricular function after myocardial infarction. These improvements parallel an increase in maximal cardiac output, but they are unrelated to vasodilatory capacity. In patients with reduced ventricular function after myocardial infarction, lower limb vasodilatory capacity improves gradually over the subsequent year, and these improvements occur irrespective of exercise training.

Abnormal desmopressin-induced forearm vasodilatation in patients with heart failure: dependence on nitric oxide synthase activity

BACKGROUND

Peripheral vasodilatation in response to muscarinic agonists has been shown to be subnormal during heart failure. However, a more recent study suggested that the abnormal muscarinic-induced vasodilatation was not due to abnormal nitric oxide synthase activity. This study was designed to show that nitric oxide synthase contributes to desmopressin-induced forearm vasodilatation and to determine whether vasodilatation mediated by nitric oxide synthase is abnormal during heart failure.

METHODS

Desmopressin (10, 50, and 100 ng/min) was infused into the brachial artery of 10 healthy subjects and eight patients with heart failure, and forearm blood flow was measured by venous occlusion plethsymography. Desmopressin responses were then recorded during inhibition of nitric oxide synthase with L-monomethylarginine or after aspirin.

RESULTS

In healthy subjects, desmopressin caused a significant (p < 0.001) dose-dependent increase in forearm blood flow of 0.9 +/- 0.6, 4.0 +/- 2.6, and 7.9 +/- 2.6 ml/min/dl, respectively. Desmopressin responses in heart failure of 0.8 +/- 0.6, 1.7 +/- 1.4, and 3.1 +/- 1.0 ml/min/dl were significantly less (p < 0.001) than normal. L-Monomethylarginine reduced desmopressin responses in normal subjects (p < 0.01), and this inhibitory effect was significantly (p < 0.01) greater than in patients with heart failure. Aspirin did not affect desmopressin-induced vasodilatation.

CONCLUSION

Nitric oxide synthase contributes to desmopressin-induced forearm vasodilatation. In response to desmopressin, patients with heart failure have subnormal vasodilatation mediated through nitric oxide synthase.

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

OBJECTIVES

This study was undertaken to investigate the role of endothelium-derived nitric oxide in the regulation of forearm blood flow during exercise in normal subjects and patients with congestive heart failure.

BACKGROUND

Nitric oxide-mediated vasodilation in response to muscarinic stimulation is impaired in the peripheral circulation of patients with congestive heart failure. Whether nitric oxide-mediated vasodilation during exercise is also impaired in patients with congestive heart failure is unknown.

METHODS

Forearm blood flows (ml/min per 100 ml) were determined during rhythmic hand grip exercise at 15%, 30% and 45% of maximal voluntary contraction by venous occlusion plethysmography before and after regional inhibition of nitric oxide synthesis with administration of L-NG-monomethylarginine (L-NMMA) in the brachial artery of 17 patients with congestive heart failure (mean age 49 years, mean left ventricular ejection fraction 0.22) and 10 age-matched normal subjects.

RESULTS

Before administration of L-NMMA in the brachial artery, forearm blood flows in patients with congestive heart failure during rhythmic hand grip exercise at 15%, 30% and 45% of maximal voluntary contraction were slightly but not significantly lower than that of normal subjects ([mean +/- SE] 6.8 +/- 1.0, 8.5 +/- 1.0 and 12.9 +/- 1.7 ml/min per 100 ml, respectively, in patients with congestive heart failure vs. 6.6 +/- 1.2, 11.6 +/- 1.9 and 16.2 +/- 1.9 ml/min per 100 ml, respectively, in normal subjects, p = NS). After administration of L-NMMA in the brachial artery, forearm blood flows in normal subjects significantly decreased by 10% to 21% during hand grip exercise but did not change during exercise in patients with congestive heart failure.

CONCLUSIONS

Regional inhibition of nitric oxide synthase with administration of L-NMMA in the brachial artery significantly decreased forearm blood flows during rhythmic hand grip exercise in normal subjects but not in patients with congestive heart failure. These findings suggest that nitric oxide-mediated vasodilation during submaximal exercise is impaired in the forearm circulation of patients with congestive heart failure.

Randomized, double-blind, placebo-controlled study of supplemental oral L-arginine in patients with heart failure

BACKGROUND

Patients with heart failure have reduced peripheral blood flow at rest, during exercise, and in response to endothelium-dependent vasodilators. Nitric oxide formed from L-arginine metabolism in endothelial cells contributes to regulation of blood flow under these conditions. A randomized, double-blind crossover study design was used to determine whether supplemental oral L-arginine can augment peripheral blood flow and improve functional status in patients with moderate to severe heart failure.

METHODS AND RESULTS

Fifteen subjects were given 6 weeks of oral L-arginine hydrochloride (5.6 to 12.6 g/d) and 6 weeks of matched placebo capsules in random sequence. Compared with placebo, supplemental oral L-arginine significantly increased forearm blood flow during forearm exercise, on average from 5.1 +/- 2.8 to 6.6 +/- 3.4 mL. min-1. dL-1 (P < .05). Furthermore, functional status was significantly better on L-arginine compared with placebo, as indicated by increased distances during a 6-minute walk test (390 +/- 91 versus 422 +/- 86 m, P < .05) and lower scores on the Living With Heart Failure questionnaire (55 +/- 28 versus 42 +/- 26, P < .05). Oral L-arginine also improved arterial compliance from 1.99 +/- 0.38 to 2.36 +/- 0.30 mL/mm Hg (P < .001) and reduced circulating levels of endothelin from 1.9 +/- 1.1 to 1.5 +/- 1.1 pmol/L (P < .05).

CONCLUSIONS

Supplemental oral L-arginine had beneficial effects in patients with heart failure. Further studies are needed to confirm the therapeutic potential of supplemental oral L-arginine and to identify mechanisms of action in patients with heart failure.

Impaired cholinergic peripheral vasodilation and its relationship to hyperemic calf blood flow response and exercise intolerance in patients with chronic heart failure

This study examined the peripheral endothelium-dependent vasodilatory response to acetylcholine and the endothelium-independent vasodilatory response to nitroprusside in 19 patients with chronic heart failure and eight controls. These peripheral blood flow responses were compared with hyperemic calf blood flow changes after maximum leg exercise and 5-min femoral occlusion. The peripheral blood flow response to forearm intra-arterial infusion of acetylcholine and sodium nitroprusside, and reactive hyperemic calf blood flow changes were measured by plethysmography. All peripheral blood flow responses were significantly reduced in patients with chronic heart failure (P < 0.05). Reduction of acetylcholine-mediated changes in peripheral blood flow was correlated with exercise-induced calf blood flow response (r = 0.51, P < 0.05), but not with occlusion-induced calf blood flow response (r = 0.02, NS). Sodium nitroprusside-mediated changes were not correlated with any reactive hyperemic blood flow responses (exercise: r = 0.27, NS; occlusion: r = 0.11, NS). When the patients were divided into two subgroups based on the median exercise-induced calf blood flow change, the subgroup with the lower calf blood flow response showed a reduction in exercise capacity (anaerobic threshold: 11.8 +/- 0.6 vs. 14.6 +/- 1.0 ml/kg/min; P < 0.05). These findings suggest that endothelial dysfunction is related to a decrease in exercise-induced skeletal muscle blood flow and exercise capacity in patients with chronic heart failure.