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

Metabolite signatures of heart failure, sleep apnoea, their interaction, and outcomes in the community

AIMS

Sleep apnoea and congestive heart failure (CHF) commonly co-exist, but their interaction is unclear. Metabolomics may clarify their interaction and relationships to outcome.

METHODS AND RESULTS

We assayed 372 circulating metabolites and lipids in 1919 and 1524 participants of the Framingham Heart Study (FHS) (mean age 54 ± 10 years, 53% women) and Women's Health Initiative (WHI) (mean age 67 ± 7 years), respectively. We used linear and Cox regression to relate plasma concentrations of metabolites and lipids to echocardiographic parameters; CHF and its subtypes heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF); and sleep indices. Adenine dinucleotide phosphate (ADP) associated with left ventricular (LV) fractional shortening; phosphocreatine with LV wall thickness; lysosomal storage molecule sphingomyelin 18:2 with LV mass; and nicotine metabolite cotinine with time spent with an oxygen saturation less than 90% (β = 2.3 min, P = 2.3 × 10^-5 ). Pro-hypertrophic metabolite hydroxyglutarate partly mediated the association between LV wall thickness and HFpEF. Central sleep apnoea was significantly associated with HFpEF (P = 0.03) but not HFrEF (P = 0.5). There were three significant metabolite canonical variates, one of which conferred protection from cardiovascular death [hazard ratio = 0.3 (0.11, 0.81), P = 0.02].

CONCLUSIONS

Energetic metabolites were associated with cardiac function; energy- and lipid-storage metabolites with LV wall thickness and mass; plasma levels of nicotine metabolite cotinine were associated with increased time spent with a sleep oxygen saturation less than 90%, a clinically significant marker of outcome, indicating a significant hazard for smokers who have sleep apnoea.

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

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

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

Background

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

Methods and Results

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

Conclusions

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

Redundant vasodilator pathways underlying radial artery flow-mediated dilation are preserved in healthy aging

Background. Blocking nitric oxide (NO) and vasodilator prostanoids (PN) does not consistently reduce flow-mediated dilation (FMD) in young adults. The impact of aging on the contribution of NO and PG to FMD is unknown. Methods. FMD was measured in older adults (n = 10, 65 ± 3 y) after arterial infusion of saline, N(G)-monomethyl-L-arginine (L-NMMA), and ketorolac + L-NMMA. Data were compared to published data in young adults. Results. L-NMMA reduced FMD in older adults (8.9 ± 3.6 to 5.9 ± 3.7%) although this was not statistically significant (P = 0.08) and did not differ (P = 0.74) from the reduction observed in young adults (10.0 ± 3.8 to 7.6 ± 4.7%; P = 0.03). Blocking PN did not affect FMD in young or older adults. In older adults, L-NMMA reduced (n = 6; range = 36-123% decrease), augmented (n = 3; 10-122% increase), or did not change FMD (n = 1; 0.4% increase). After PN blockade, FMD responses were reduced (n = 2), augmented (n = 6), or unaffected (n = 1). Conclusions. NO or PN blockade did not consistently reduce FMD in healthy older adults, suggesting the existence of redundant vasodilator phenotypes as observed previously in young adults.

Heterogenous vasodilator pathways underlie flow-mediated dilation in men and women

This study investigated the sex differences in the contribution of nitric oxide (NO) and prostaglandins (PGs) to flow-mediated dilation (FMD). Radial artery (RA) FMD, assessed as the dilatory response to 5-min distal cuff occlusion, was repeated after three separate brachial artery infusions of saline (SAL), N(G)-monomethyl-L-arginine (L-NMMA), and ketorolac (KETO) + L-NMMA in healthy younger men (M; n = 8) and women (W; n = 8). In eight subjects (4 M, 4W) RA FMD was reassessed on a separate day with drug order reversed (SAL, KETO, and L-NMMA + KETO). RA FMD was calculated as the peak dilatory response observed relative to baseline (%FMD) and expressed relative to the corresponding area under the curve shear stress (%FMD/AUC SS). L-NMMA reduced %FMD similarly and modestly (P = 0.68 for sex * trial interaction) in M and W (all subjects: 10.0 ± 3.8 to 7.6 ± 4.7%; P = 0.03) with no further effect of KETO (P = 0.68). However, all sex * trial and trial effects on %FMD/AUC SS for l-NMMA and KETO + l-NMMA were insignificant (all P > 0.20). There was also substantial heterogeneity of the magnitude and direction of dilator responses to blockade. After l-NMMA infusion, subjects exhibited both reduced (n = 14; range: 11 to 78% decrease) and augmented (n = 2; range: 1 to 96% increase) %FMD. Following KETO + l-NMMA, seven subjects exhibited reduced dilation (range: 10 to 115% decrease) and nine subjects exhibited augmented dilation (range: 1 to 212% increase). Reversing drug order did not change the nature of the findings. These findings suggest that RA FMD is not fully or uniformly NO dependent in either men or women, and that there is heterogeneity in the pathways underlying the conduit dilatory response to ischemia.

Nitric oxide is not obligatory for radial artery flow-mediated dilation following release of 5 or 10 min distal occlusion

This study investigated the nitric oxide (NO) dependence of radial artery (RA) flow-mediated dilation (FMD) in response to three different reactive hyperemia (RH) shear stimulus profiles. Ten healthy males underwent the following three RH trials: 1) 5 min occlusion (5 trial), 2) 10 min occlusion (10 trial), and 3) 10 min occlusion with cuff reinflation at 30 s (10–30 trial). Trials were performed during saline infusion and repeated during NG-monomethyl-l-arginine (l-NMMA) infusion in the brachial artery. RA blood flow velocity was measured with Doppler ultrasound, and B-mode RA images were analyzed using automated edge detection software. Shear rate estimation of shear stress was calculated as the blood flow velocity/vessel diameter. l-NMMA decreased baseline vascular conductance by 35%. l-NMMA infusion did not affect the peak shear rate stimulus ( P = 0.681) or the area under the curve (AUC) of shear rate to peak FMD ( P = 0.088). The AUC was significantly larger in the 10 trial vs. the 10–30 or 5 trial ( P < 0.001). Although percent FMD (%change in diameter) in the 10 trial was larger than that in the 5 trial ( P = 0.035), there was no significant difference in %FMD between the saline and l-NMMA conditions in any trial: 5 trial, 5.62 ± 1.48 vs. 5.63 ± 1.27%; 10 trial, 9.07 ± 1.16 vs. 11.22 ± 2.21%; 10–30 trial, 6.52 ± 1.43 vs. 7.98 ± 1.51% for saline and l-NMMA, respectively ( P = 0.158). We conclude the following: 1) RH following 10 min of occlusion results in an enhanced stimulus and %FMD compared with 5 min of occlusion. 2) When the occlusion cuff is reinflated 30 s postrelease of a 10 min occlusion, it does not result in an enhanced %FMD compared with that which results from RH following 5 min of occlusion. 3) The lack of effect of l-NMMA on FMD suggests that NO may not be obligatory for radial artery FMD in response to either 5 or 10 min of occlusion in healthy volunteers.

Role of xanthine oxidoreductase in cardiac nitroso-redox imbalance

Emerging evidence supports the importance of nitroso-redox balance in the cardiovascular system. Xanthine oxidoreductase (XOR) is a major oxidative enzyme and increased XOR activity, leading to both increased production of reactive oxygen species and uric acid, is implicated in heart failure. Within the heart, XOR activity stimulates cardiomyocyte hypertrophy, apoptosis, and impairs matrix structure. The underpinnings of these derangements can be linked not solely to oxidative stress, but may also involve the process of nitroso-redox imbalance. In this regard, XOR interacts with nitric oxide signaling at numerous levels, including a direct protein-protein interaction with neuronal nitric oxide synthase (NOS1) in the sarcoplasmic reticulum. Deficiency or translocation of NOS1 away from this microdomain leads to increased activity of XOR, which in turn impairs excitation-contraction coupling and myofilament calcium sensitivity. There is a mounting abundance of preclinical data supporting beneficial effects of inhibiting XOR, but translation to the clinic continues to be incomplete. A growing understanding of XOR and its role in nitroso-redox imbalance has great potential to lead to improved pathophysiologic insights and possibly therapeutic advances.

Role of kallistatin in prevention of cardiac remodeling after chronic myocardial infarction

Oxidative stress causes cardiomyocyte death and subsequent ventricular dysfunction and cardiac remodeling after myocardial infarction (MI), thus contributing to high mortality in chronic heart failure patients. We investigated the effects of kallistatin in cardiac remodeling in a chronic MI rat model and in primary cardiac cells. Human kallistatin gene was injected intramyocardially 20 min after ligation of the left coronary artery. At 4 weeks after MI, expression of human kallistatin in rat hearts was identified by reverse transcription-polymerase chain reaction, immunohistochemistry and ELISA. Kallistatin administration improved cardiac performance, increased mean arterial pressure, decreased myocardial infarct size and restored left ventricular wall thickness. Kallistatin treatment significantly attenuated cardiomyocyte size and atrial natriuretic peptide expression. Kallistatin also reduced collagen accumulation, collagen fraction volume and expression of collagen types I and III, transforming growth factor-beta1 (TGF-beta1) and plasminogen activator inhibitor-1 in the myocardium. Inhibition of cardiac hypertrophy and fibrosis by kallistatin was associated with increased cardiac nitric oxide (NO) levels and decreased superoxide formation, NADH oxidase activity and p22-phox expression. Moreover, in both primary cultured rat cardiomyocytes and myofibroblasts, recombinant kallistatin inhibited intracellular superoxide formation induced by H(2)O(2), and the antioxidant effect of kallistatin was abolished by Nomega-nitro-L-arginine methyl ester (L-NAME), indicating a NO-mediated event. Kallistatin promoted survival of cardiomyocytes subjected to H(2)O(2) treatment, and inhibited H(2)O(2)-induced Akt and ERK phosphorylation, as well as NF-kappaB activation. Furthermore, kallistatin abrogated TGF-beta-induced collagen synthesis and secretion in cultured myofibroblasts. This is the first study to demonstrate that kallistatin improves cardiac performance and prevents post-MI-induced cardiac hypertrophy and fibrosis through its antioxidant action.

Activation of inducible NOS in peripheral vessels and outcomes in heart failure patients

BACKGROUND

Activation of inducible nitric oxide synthase (iNOS) has been reported in congestive heart failure (CHF) conditions. However, it is unknown whether activation of iNOS affects prognosis of CHF patients. We prospectively studied the influence of activation of iNOS in the forearm on the outcome of CHF patients.

METHODS AND RESULTS

Forearm blood flow (FBF) responses to 3 doses of acetylcholine (ACh) and nitroglycerin (NTG), and 4 doses of a selective iNOS inhibitor (aminoguanidine: Amn) and a nonselective NOS inhibitor (L-NMMA) were examined using plethysmography in 68 patients with CHF from idiopathic dilated cardiomyopathy. Plasma brain natriuretic peptide (BNP) and tumor necrosis factor-alpha (TNF-alpha) were also measured in all patients. During the mean follow-up period of 3.8 years, 25 patients were hospitalized for worsening heart failure and 9 of these patients died. Patients with adverse events had a diminished vasodilator response to ACh (P < .001) compared to patients without adverse events. Amn significantly decreased FBF (P < .001) in patients with adverse events, but not in patients without adverse events. FBF responses to NTG and L-NMMA were not significantly different between the 2 groups. When grouped by maximum FBF responses to each drug above and below the median value, multivariate Cox proportional hazards model analyses for cardiac event showed a significance in the FBF response to Amn (adjusted hazard ratio 5.89, P < .001). FBF responses to maximum dose of Amn significantly correlated with BNP and TNF-alpha levels (both P < .001).

CONCLUSIONS

CHF patients with vascular iNOS activation, as demonstrated by a greater vasoconstrictor response to Amn, had poor outcomes. Activation of iNOS in peripheral vessels, associated with proinflammatory cytokines in accordance to the severity of heart failure, is a marker for, or contributes to, adverse events in patients with CHF.

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.

Plasma Brain Natriuretic Peptide Levels Indicating Thromboembolism in Very Elderly Patients With Non-Valvular Atrial Fibrillation

BACKGROUND

Assessment of left atrial (LA) function by transesophageal echocardiography is useful for detecting patients with a high risk thromboembolism secondary to atrial fibrillation (AF). A recent study showed that the atrium is the main source of brain natriuretic peptide (BNP) in AF patients without overt heart failure. The purpose of this study was to assess the possible relationship between LA function and plasma BNP levels in very elderly patients with non-valvular AF.

METHODS AND RESULTS

Seventy-four consecutive patients with chronic non-valvular AF (aged, 82+/-6 years) underwent transthoracic and transesophageal echocardiography and measurement of plasma BNP. Thirteen AF patients who had a history of cerebral embolism or echocardiographic evidence of thrombus (TE+ group) were compared with 61 AF patients who had no such complications (TE- group). The TE+ group demonstrated a lower LA appendage (LAA) velocity and higher plasma BNP level than the TE- group. Assessment of variables by multiple logistic regression analysis revealed that BNP was a significant predictor of thromboembolism. There was a significant negative correlation between the plasma BNP level and the LAA peak flow velocity.

CONCLUSIONS

The present findings would suggest the usefulness of measuring plasma BNP to detect very elderly non-valvular AF patients at high risk for thromboembolism.

Effects of oral beraprost sodium, a prostaglandin I2 analogue, on endothelium dependent vasodilatation in the forearm of patients with coronary artery disease

1. Previous clinical studies with prostaglandin I(2) (PGI(2)) analogue beraprost sodium suggested the potential effects on protection of cardiovascular events in patients with peripheral artery disease. Although the mechanism is not well known, experimental studies have shown protective effects of endothelial cells. This study was designed to examine the effects of beraprost sodium on vascular endothelial function in the forearm of patients with coronary artery disease. 2. Beraprost sodium (120 microg/day) was orally administered to 14 coronary artery disease patients for 4 weeks and then stopped for 4 weeks. Eleven control patients did not receive beraprost sodium treatment. Reactive hyperemia was induced in the forearm, endothelium-dependent vasodilatation was assessed by plethysmography, and urinary 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)) was measured at baseline, 4 weeks and 8 weeks. 3. Both groups had similar reactive hyperemic responses at baseline. In the control group, reactive hyperemic response and urinary 8-iso-PGF(2alpha) remained unchanged for 8 weeks. In the beraprost group, maximum forearm blood flow increased significantly (P = 0.01) after 4 weeks of treatment and returned to baseline at 8 weeks. Duration of hyperemia increased significantly (P = 0.003) after 4 weeks, and remained greater than baseline at 8 weeks (P = 0.02). Urinary 8-iso-PGF(2alpha) decreased significantly (P = 0.03) after 4 weeks, and tended to be lower at 8 weeks (P = 0.07). Changes in reactive hyperemia correlated weakly but significantly with changes in 8-iso-PGF(2alpha) (P < 0.001). 4. Beraprost sodium decreased oxidative stress and improved forearm endothelium-dependent vasodilatation in coronary artery disease patients. The favorable effects on vascular endothelium could potentially lead to a decrease in vascular events.

Nonheart failure-associated elevation of amino terminal pro-brain natriuretic peptide in the setting of sepsis

In addition to its importance in clinical assessment, N-terminal pro-brain natriuretic peptide (NT pro-BNP) is a valuable marker for evaluation of treatment and prognosis of heart failure. However, there are situations where NT pro-BNP is not related to myocardial dysfunction. Two cases of sepsis with markedly elevated NT pro-BNP levels that are not indicative of depressed myocardial function are described.

Short duration of reactive hyperemia in the forearm of subjects with multiple cardiovascular risk factors

BACKGROUND

Peripheral vascular endothelial dysfunction is an independent predictor of cardiovascular events, and can be assessed noninvasively by measuring reactive hyperemia, either by vascular ultrasound measurement of flow-mediated vasodilatation or, less commonly, by measurement of blood flow using plethysmography. In the present study reactive hyperemia was measured using plethysmography in healthy subjects with multiple cardiovascular risk factors.

METHODS AND RESULTS

Reactive hyperemia was measured following 5-min occlusion of the upper arm in 449 healthy subjects (302 men, 147 women, age range 20-70 years) with (n=352) and without (n=97) risk factors such as smoking, hypertension, diabetes mellitus, hypercholesterolemia, obesity, family history of cardiovascular disease, and menopause. Maximum blood flow and minimum vascular resistance in reactive hyperemia did not differ between subjects with and without risk factors regardless of gender. Duration of reactive hyperemia, however, was significantly shorter in subjects with risk factors. Age-adjusted mean value of duration of reactive hyperemia was significantly smaller in men with a smoking habit, diabetes mellitus, hypercholesterolemia or obesity, and in women with smoking habit, hypertension, diabetes mellitus or obesity. The number of risk factors significantly correlated with the duration of reactive hyperemia in both men (r=-0.56, p<0.001) and women (r=-0.62, p<0.001), suggesting that endothelial dysfunction increases with the number of risk conditions clustering in a single individual.

CONCLUSIONS

Duration of reactive hyperemia reflects cardiovascular risk factors and decreases with the number of risk conditions. These findings suggest that the duration of reactive hyperemia measured with plethysmography is potentially useful for assessing endothelial dysfunction.

Vascular and renal actions of brain natriuretic peptide in man: physiology and pharmacology

During the last decade brain natriuretic peptide (BNP) has received increasing attention as a potential marker of cardiovascular disease. BNP may act as a compensating mechanism in cardiovascular diseases in order to reduce preload. However, the increase in endogenous BNP is often not sufficient to compensate for volume overload in diseases like established hypertension and heart failure. The reported hemodynamic and renal effects of BNP in man differ largely between studies, because of differences in design and doses of BNP employed. In the pharmacological range, BNP has clear blood pressure and afterload lowering effects, and in the kidney blood flow and filtration is increased with concomitant natriuresis and diuresis. While in the physiological range BNP does not affect blood pressure and reduces preload only, and induces natriuresis/diuresis without changes in renal blood flow and filtration. There is increasing evidence from vascular studies that BNP preferentially acts on the venous system resulting in preload reduction, in contrast to atrial natriuretic peptide which acts preferentially on the arterial system to reduce afterload. This review summarizes our current understanding of BNP, and discuss its regulation and mechanisms of action on the vasculature and the kidneys.

Endothelial cell activation in patients with decompensated heart failure

BACKGROUND

Vascular endothelial functions, other than nitric oxide (NO)-mediated control of vasomotor tone, are poorly characterized in patients with chronic heart failure (CHF). Veins and arteries are exposed to the same circulating proinflammatory mediators in patients with CHF. The present study tested whether endothelial cell activation occurs in veins of patients with decompensated CHF and whether activation, if present, subsides with return to a clinically compensated state.

METHODS AND RESULTS

Fifteen patients with decompensated CHF requiring transient inotropic support and 6 age-matched, healthy controls were studied. Endothelial cells and blood were collected from a forearm vein, and brachial artery flow-mediated dilation (FMD) was measured before and 24 hours after discontinuation of short-term inotropic therapy, when patients had returned to a steady compensated state. Nitrotyrosine immunoreactivity (an intracellular marker of oxidative stress), cyclooxygenase-2 (COX-2), and inducible NO synthase (iNOS) expression were significantly higher in venous endothelial cells of patients in clinical decompensation when compared with healthy subjects. Return to a compensated state resulted in a significant reduction in nitrotyrosine immunoreactivity, COX-2, and iNOS expression. Concomitantly, a significant increase in FMD and a decline in plasma total 8-isoprostane and bicycloprostaglandin E2 levels were observed. Venous endothelial NOS expression was unaffected by clinical decompensation.

CONCLUSIONS

Clinical decompensation in CHF is associated with activation of the venous endothelium. Return to a compensated state after short-term inotropic therapy results in a significant reduction in endothelial nitrotyrosine formation, COX-2, and iNOS expression.

Endothelial Dysfunction and Damage in Congestive Heart Failure

Background— Congestive heart failure (CHF) is associated with endothelial perturbation (as defined by flow-mediated endothelial-dependent vasodilation [FMD, an index of endothelial dysfunction], circulating endothelial cells [CECs, an index of endothelial damage], or plasma indexes of endothelial damage/dysfunction [eg, von Willebrand factor (vWf) and soluble thrombomodulin (sTM)]) and raised plasma levels of brain natriuretic peptide (BNP, a peptide hormone associated with left ventricular systolic dysfunction and prognosis). However, the relations between these parameters are unclear.

Methods and Results— To test the hypothesis that there is a relation between endothelial perturbation (defined by FMD, CECs, vWf, and sTM) and BNP in CHF, we studied these indexes in 30 patients with CHF who were compared with 20 age-matched control subjects. FMD, CECs, plasma vWf, and BNP levels (but not sTM) were all abnormal in patients with CHF. There were significant inverse correlations between FMD and vWf ( P =0.001), CECs ( P =0.002) and BNP ( P =0.006) as well as a positive correlation between CECs and vWf ( P =0.032). In multivariate analysis, BNP ( P <0.001) and FMD ( P <0.001) were both independently associated with CHF.

Conclusions— Ample evidence of endothelial cell damage/dysfunction in CHF cannot be fully explained by the variance in plasma BNP per se. Therefore, the routes by which these indexes influence the pathophysiology of CHF as well as predict adverse outcomes may be independent.

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.

Increased nitric oxide in proportion to the severity of heart failure in patients with dilated cardiomyopathy: close correlation of tumor necrosis factor-alpha with systemic and local production of nitric oxide

Recent studies have demonstrated that proinflammatory cytokines induce large amounts of nitric oxide (NO) and that the amount increases in patients with congestive heart failure (CHF). There are, however, few reports regarding the relationships between NO production, cytokines and the severity of heart failure, so the plasma concentrations of nitrite and nitrate (NOx), tumor necrosis factor-alpha (TNF-alpha) and brain natriuretic peptide (BNP) were measured in 43 patients with CHF caused by dilated cardiomyopathy and 26 age- and sex-matched normal control subjects. Forearm blood flow (FBF) was measured using plethysmography during infusions of acetylcholine and nitroglycerin and after the administration of the NO synthesis inhibitor L-NMMA (N(G)-monomethyl-L-arginine). Plasma concentrations of both NOx and TNF-alpha were significantly higher in the patient group than in the control group (p<0.001) and correlated closely with BNP concentrations (p<0.001). There was a positive relationship between NOx and TNF-alpha concentrations (r=0.80, p<0.001). Administration of L-NMMA significantly reduced FBF in both groups, and the percent change in FBF from baseline correlated significantly with TNF-alpha concentrations (r=0.63, p<0.001). The FBF response to acetylcholine was depressed in the patient group and correlated inversely with TNF-alpha concentrations. The FBF response to nitroglycerin did not correlate with TNF-alpha concentrations. The findings indicate that the concentrations of NO and TNF-alpha in patients with CHF increase in proportion to the severity of heart failure, and that TNF-alpha plays a role in the enhanced systemic and local production of NO.

Impaired exercise-induced vasodilatation in chronic atrial fibrillation--role of endothelium-derived nitric oxide

Exercise capacity is often reduced in patients with atrial fibrillation (AF), but very few studies have focused on changes in endothelial function as a potential mechanism for the exercise limitation. The present study used using venous occlusion plethysmography to investigate whether nitric oxide (NO)-mediated vasodilatation is attenuated during exercise in patients with AF by measuring forearm blood flow (FBF) in 10 patients at rest and immediately after 2 levels of rhythmic handgrip exercise, before and after inhibition of NO synthesis with N(G)-monomethyl-L-arginine (L-NMMA, 100 micromol). The measurements were repeated 1 day after restoration of sinus rhythm by cardioversion. FBF responses to graded doses of acetylcholine (ACh) were also observed before and after cardioversion. Heart rate decreased after cardioversion, but blood pressure did not change. FBF at rest was not affected by cardioversion, but at the highest level of exercise it increased from 28.4+/-2.3 ml x min(-1) x dl(-1) before to 39.4+/-3.2 ml x min(-1) x dl(-1) after cardioversion (p<0.05). L-NMMA significantly decreased FBF at rest (p<0.01) and depressed the increase in FBF response to exercise after (p<0.01), but not before cardioversion. The FBF response to ACh was also accelerated significantly after cardioversion. The present results provide new evidence that NO bioavailability is depressed at rest and during exercise in patients with AF.

High plasma brain natriuretic polypeptide level as a marker of risk for thromboembolism in patients with nonvalvular atrial fibrillation

BACKGROUND AND PURPOSE

Assessment of left atrial appendage (LAA) function with transesophageal echocardiography is useful for detecting patients at high risk for thromboembolism as a result of atrial fibrillation (AF). A recent study reported that the atrium is the main source of brain natriuretic polypeptide (BNP) in AF patients without overt heart failure. The purpose of this study was to assess a possible relationship between LAA function and plasma BNP levels in nonvalvular AF.

METHODS

Thirty-four consecutive patients with chronic nonvalvular AF (age, 69+/-9 years) underwent transesophageal echocardiography and plasma BNP measurement. Thirteen patients with a history of thromboembolism or echocardiographic evidence of thrombus (E + group) were compared with 21 AF patients without complications (E- group).

RESULTS

The E+ group patients demonstrated greater impairment of LAA velocity and higher plasma BNP levels than the E- group patients (LAA velocity: 12+/-6 versus 31+/-17 cm/s, P<0.05; plasma BNP: 126+/-53 versus 86+/-45 ng/L, P<0.05). Overall analysis of the continuous variables with multiple logistic regression analysis revealed that BNP was a significant predictor of thromboembolism. There was a weak but significant negative correlation between plasma BNP levels and LAA flow velocity (r=0.38, P<0.05). No intergroup difference in plasma atrial natriuretic polypeptide levels was found.

CONCLUSIONS

The present data suggest the usefulness of measuring plasma BNP levels, which may reflect augmented atrial secretion of BNP from the impaired atrial myocardium, in detecting patients at high risk for thromboembolic complications in nonvalvular AF.

Nitric oxide and potassium channels are involved in brain natriuretic peptide induced vasodilatation in man

OBJECTIVE

Brain natriuretic peptide (BNP) causes vasodilatation but the mechanisms by which this is accomplished are not fully known. The aim of the present study was to determine whether, besides K+Ca2+-channels, nitric oxide (NO) is involved in BNP-induced vasodilatation.

METHODS

We studied 10 healthy males twice, in random order, at an interval of 2 weeks. Experiments always started with infusion of BNP (8-16-32-64 pmol/dl per min) into the brachial artery. On the first day this infusion was followed by a second BNP infusion combined with the K+Ca2+-channel-blocker, tetraethylammonium (TEA, 0.1 mg/dl per min), and on the other day by BNP infusion combined with the NO-synthase inhibitor, l-NG-monomethyl arginine (l-NMMA, 0.8 mumol/dl per min). The latter was then followed by a combined infusion of BNP, l-NMMA and TEA. All infusions were separated by a 1 h washout period. Forearm blood flow (FBF) was determined by venous occlusion plethysmography.

RESULTS

Mean arterial pressure and heart rate did not change during any of the experiments. BNP alone induced a dose-dependent dilatation, which was similar on both days. TEA, l-NMMA, and their combination all reduced the BNP-induced dilatation (P < 0.05). The combined infusion had a significantly greater effect than TEA alone (P = 0.005). BNP infusions were associated with a significant increase in plasma cyclic guanosine monophosphate (cGMP) and C-type natriuretic peptide (CNP) (P < 0.05).

CONCLUSIONS

BNP induces arterial vasodilatation not only by opening K+Ca2+-channels, but also via stimulation of NO production. In addition, BNP stimulates net CNP increase.

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.