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The Nitrate-Nitrite-NO Pathway and Its Implications for Heart Failure and Preserved Ejection Fraction.

ABSTRACT: The pathogenesis of exercise intolerance in patients with heart failure and preserved ejection fraction (HFpEF) is likely multifactorial. In addition to cardiac abnormalities (diastolic dysfunction, abnormal contractile reserve, chronotropic incompetence), several peripheral abnormalities are likely to be involved. These include abnormal pulsatile hemodynamics, abnormal arterial vasodilatory responses to exercise, and abnormal peripheral O2 delivery, extraction, and utilization. The nitrate-nitrite-NO pathway is emerging as a potential target to modify key physiologic abnormalities, including late systolic left ventricular (LV) load from arterial wave reflections (which has deleterious short- and long-term consequences for the LV), arterial vasodilatory reserve, muscle O2 delivery, and skeletal muscle mitochondrial function. In a recently completed randomized trial, the administration of a single dose of exogenous inorganic nitrate has been shown to exert various salutary arterial hemodynamic effects, ultimately leading to enhanced aerobic capacity in patients with HFpEF. These effects have the potential for both immediate improvements in exercise tolerance and for long-term "disease-modifying" effects. In this review, we provide an overview of key mechanistic contributors to exercise intolerance in HFpEF, and of the potential therapeutic role of drugs that target the nitrate-nitrite-NO pathway.

SUBMITTER: Chirinos JA

PROVIDER: S-EPMC4755323 | biostudies-literature | 2016 Feb

REPOSITORIES: biostudies-literature

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The Nitrate-Nitrite-NO Pathway and Its Implications for Heart Failure and Preserved Ejection Fraction.

Chirinos Julio A JA Zamani Payman P

Current heart failure reports 20160201 1

The pathogenesis of exercise intolerance in patients with heart failure and preserved ejection fraction (HFpEF) is likely multifactorial. In addition to cardiac abnormalities (diastolic dysfunction, abnormal contractile reserve, chronotropic incompetence), several peripheral abnormalities are likely to be involved. These include abnormal pulsatile hemodynamics, abnormal arterial vasodilatory responses to exercise, and abnormal peripheral O2 delivery, extraction, and utilization. The nitrate-nitr ...[more]

PMID: 26792295

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Project description:RATIONALE:Nitrate-rich beetroot juice has been shown to improve exercise capacity in heart failure with preserved ejection fraction, but studies using pharmacological preparations of inorganic nitrate are lacking. OBJECTIVES:To determine (1) the dose-response effect of potassium nitrate (KNO3) on exercise capacity; (2) the population-specific pharmacokinetic and safety profile of KNO3 in heart failure with preserved ejection fraction. METHODS AND RESULTS:We randomized 12 subjects with heart failure with preserved ejection fraction to oral KNO3 (n=9) or potassium chloride (n=3). Subjects received 6 mmol twice daily during week 1, followed by 6 mmol thrice daily during week 2. Supine cycle ergometry was performed at baseline (visit 1) and after each week (visits 2 and 3). Quality of life was assessed with the Kansas City Cardiomyopathy Questionnaire. The primary efficacy outcome, peak O2-uptake, did not significantly improve (P=0.13). Exploratory outcomes included exercise duration and quality of life. Exercise duration increased significantly with KNO3 (visit 1: 9.87, 95% confidence interval [CI] 9.31-10.43 minutes; visit 2: 10.73, 95% CI 10.13-11.33 minute; visit 3: 11.61, 95% CI 11.05-12.17 minutes; P=0.002). Improvements in the Kansas City Cardiomyopathy Questionnaire total symptom (visit 1: 58.0, 95% CI 52.5-63.5; visit 2: 66.8, 95% CI 61.3-72.3; visit 3: 70.8, 95% CI 65.3-76.3; P=0.016) and functional status scores (visit 1: 62.2, 95% CI 58.5-66.0; visit 2: 68.6, 95% CI 64.9-72.3; visit 3: 71.1, 95% CI 67.3-74.8; P=0.01) were seen after KNO3. Pronounced elevations in trough levels of nitric oxide metabolites occurred with KNO3 (visit 2: 199.5, 95% CI 98.7-300.2 ?mol/L; visit 3: 471.8, 95% CI 377.8-565.8 ?mol/L) versus baseline (visit 1: 38.0, 95% CI 0.00-132.0 ?mol/L; P<0.001). KNO3 did not lead to clinically significant hypotension or methemoglobinemia. After 6 mmol of KNO3, systolic blood pressure was reduced by a maximum of 17.9 (95% CI -28.3 to -7.6) mm?Hg 3.75 hours later. Peak nitric oxide metabolites concentrations were 259.3 (95% CI 176.2-342.4) ?mol/L 3.5 hours after ingestion, and the median half-life was 73.0 (interquartile range 33.4-232.0) minutes. CONCLUSIONS:KNO3 is potentially well tolerated and improves exercise duration and quality of life in heart failure with preserved ejection fraction. This study reinforces the efficacy of KNO3 and suggests that larger randomized trials are warranted. CLINICAL TRIAL REGISTRATION:URL: http://www.clinicaltrials.gov. Unique identifier: NCT02256345.

Project description:Inorganic nitrate (NO3(-)), abundant in certain vegetables, is converted to nitrite by bacteria in the oral cavity. Nitrite can be converted to nitric oxide in the setting of hypoxia. We tested the hypothesis that NO3(-) supplementation improves exercise capacity in heart failure with preserved ejection fraction via specific adaptations to exercise.Seventeen subjects participated in this randomized, double-blind, crossover study comparing a single dose of NO3-rich beetroot juice (NO3(-), 12.9 mmol) with an identical nitrate-depleted placebo. Subjects performed supine-cycle maximal-effort cardiopulmonary exercise tests, with measurements of cardiac output and skeletal muscle oxygenation. We also assessed skeletal muscle oxidative function. Study end points included exercise efficiency (total work/total oxygen consumed), peak VO2, total work performed, vasodilatory reserve, forearm mitochondrial oxidative function, and augmentation index (a marker of arterial wave reflections, measured via radial arterial tonometry). Supplementation increased plasma nitric oxide metabolites (median, 326 versus 10 ?mol/L; P=0.0003), peak VO2 (12.6±3.7 versus 11.6±3.1 mL O2·min(-1)·kg(-1); P=0.005), and total work performed (55.6±35.3 versus 49.2±28.9 kJ; P=0.04). However, efficiency was unchanged. NO3(-) led to greater reductions in systemic vascular resistance (-42.4±16.6% versus -31.8±20.3%; P=0.03) and increases in cardiac output (121.2±59.9% versus 88.7±53.3%; P=0.006) with exercise. NO3(-) reduced aortic augmentation index (132.2±16.7% versus 141.4±21.9%; P=0.03) and tended to improve mitochondrial oxidative function.NO3(-) increased exercise capacity in heart failure with preserved ejection fraction by targeting peripheral abnormalities. Efficiency did not change as a result of parallel increases in total work and VO2. NO3(-) increased exercise vasodilatory and cardiac output reserves. NO3(-) also reduced arterial wave reflections, which are linked to left ventricular diastolic dysfunction and remodeling.www.clinicaltrials.gov. Unique identifier: NCT01919177.

Project description:AimsHeart failure with preserved ejection fraction (HFpEF) is a heterogeneous condition, and tissue congestion manifested by oedema is not present in all patients. We compared clinical characteristics, exercise capacity, and outcomes in patients with HFpEF with and without oedema.Methods and resultsThis study was a post hoc analysis of pooled data of patients with left ventricular ejection fraction of ?50% enrolled in the DOSE, CARRESS-HF, RELAX, ATHENA, ROSE, INDIE, and NEAT trials. Patients were dichotomized by the severity of oedema. Cox proportional hazard regression and generalized linear regression models were used to assess associations between oedema, symptoms, and clinical outcomes. The ambulatory cohort included 393 patients (228 with and 165 without oedema), and the hospitalized cohort included 338 patients (249 with ?moderate oedema and 89 with mild or none). Among ambulatory patients, patients with oedema had a higher body mass index (35.2 kg/m2 [inter-quartile range, IQR 30.5, 41.6] vs. 31.6 kg/m2 [IQR 27.9, 36.3], P < 0.001), greater burden of co-morbidities, higher intravascular pressures estimated on physical examination (elevated jugular venous pressure: 50% vs. 24.7%, P < 0.001), poorer renal function (creatinine: 1.2 mg/dL [IQR 0.9, 1.5] vs. 1 mg/dL [IQR 0.8, 1.3], P = 0.003), and lower peak VO2 (adjusted mean difference -1.04 mL/kg/min, 95% confidence interval [-1.71, -0.37], P < 0.003). Among hospitalized patients, despite greater in-hospital fluid/weight loss in the ?moderate oedema group, there was no difference in the improvement in dyspnoea by the visual analogue scale or well-being visual analogue scale from baseline to 3-4 days and no statistically significant difference in the rate of 60 day rehospitalization/death (adjusted hazard ratio 1.44, 95% confidence interval [0.87, 2.39], P = 0.156).ConclusionsPatients with HFpEF and oedema display higher body mass, greater burden of co-morbidities, and more severe exercise intolerance, but clinical responses to treatment appear similar. Further research is required to better understand the nature of volume distribution in different HFpEF phenotypes.

Project description:AimsWe sought to compare the generalizability and prognostic implications of heart failure with preserved ejection fraction (HFpEF) scores (HFA-PEFF and H2 FPEF score) in Treatment of Preserved Cardiac Function Heart Failure with an Aldosterone Antagonist (TOPCAT) and Phosphodiesterase-5 Inhibition to Improve Clinical Status and Exercise Capacity in Heart Failure with Preserved Ejection Fraction (RELAX) trial participants and matched controls from the Atherosclerosis Risk in Community (ARIC) study.Methods and resultsBased on the respective scores, the study participants from the TOPCAT (N = 356), RELAX (N = 216), and ARIC (N = 379) studies were categorized as having a low, intermediate, or high likelihood of HFpEF. Age, sex, and race matched controls free of cardiovascular disease who had unexplained dyspnoea were used to evaluate the diagnostic performance. The prognostic value of scores was assessed using multivariable-adjusted Cox regression analyses. The median HFA-PEFF scores in the TOPCAT, RELAX, and ARIC studies were 5.0 [interquartile range (IQR): 5.0-6.0], 4.0 (IQR: 2.0-4.0), and 3.0 (IQR: 2.0-4.0), respectively. The median H2 FPEF scores in the three studies were 5.5 (IQR: 4.0-7.0), 6.0 (IQR: 4.0-7.0), and 3.0 (IQR: 2.0-5.0), respectively. A low HFA-PEFF and H2 FPEF score can rule out HFpEF with high sensitivity (99.5% and 99.6%, respectively) and negative predictive value (95.7% and 98.3%, respectively). A high HFA-PEFF and H2 FPEF score can rule-in HFpEF with good specificity (82.8% and 95.6%, respectively) and positive predictive value (79.9% and 90.4%, respectively). Among TOPCAT participants, the hazard for adverse cardiovascular events per point increase in HFA-PEFF and H2 FPEF score was 1.26 (95% confidence interval: 0.98-1.63) and 1.01 (95% confidence interval: 0.88-1.15), respectively. A higher H2 FPEF score was associated with lower peak oxygen intake in RELAX trial participants (adjusted P = 0.01).ConclusionsThe HFA-PEFF and the H2 FPEF scores are reliable diagnostic tools for HFpEF. The prognostic utility of HFpEF scores requires further validation in larger rigorously phenotyped populations.

Dataset Information

The Nitrate-Nitrite-NO Pathway and Its Implications for Heart Failure and Preserved Ejection Fraction.

Publications

The Nitrate-Nitrite-NO Pathway and Its Implications for Heart Failure and Preserved Ejection Fraction.

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