Fabien Despas

Cardiorenal anemia syndrome in chronic heart failure contributes to increased sympathetic nerve activity

BACKGROUNDnWe sought to assess whether cardiorenal anemia syndrome (CRAS) in chronic heart failure (CHF) patients contributes to sympathetic overactivity through modulation of sympathetic reflexes.nnnMETHODS AND RESULTSnWe prospectively studied 15 patients with CRAS and CHF and 15 control CHF patients, matched for age, gender distribution, type of cardiomyopathy, left ventricular ejection fraction (LVEF) and BMI. We compared muscle sympathetic nerve activity (MSNA) and the effect of peripheral chemoreflex deactivation on MSNA in both groups. We also compared sympathetic baroreflex function, assessed by the slope of the relationship between MSNA and diastolic blood pressure in both groups and while peripheral chemoreflexes were (by breathing 100% oxygen for 15 min) or not deactivated. Baseline MSNA was significantly elevated in CHF patients with CRAS compared with control CHF patients (83.1 ± 4.6 versus 64.9 ± 2.9 bursts/100 heart beats; P<0.05) and sympathetic baroreflex impaired (2.69 ± 0.44 vs 5.25 ± 0.60%bursts/mmHg; P<0.01). Chemoreflex deactivation with administration of 100% oxygen led to a significant decrease in muscle sympathetic nerve activity (77.8 ± 4.7 versus 82.1 ± 4.9 bursts/100 heart beats; P<0.01) and to an increase in sympathetic baroreflex function (2.77 ± 0.45 vs 5.63 ± 0.73%bursts/mmHg; P<0.01) in patients with CRAS and CHF. In contrast, neither room air nor 100% oxygen changed MSNA, hemodynamic or sympathetic baroreflex function in control CHF patients.nnnCONCLUSIONSnCRAS in CHF patients is associated with elevated sympathetic activity mediated by both tonic activation of peripheral chemoreflex and baroreflex impairment.

Effects of leptin on sympathetic nerve activity in conscious mice.

The adipocyte‐derived hormone, leptin, has emerged as an important regulator of regional sympathetic nerve activity (SNA) with pathophysiological implications in obesity. Genetically engineered mice are useful to understand the molecular pathways underlying the SNA responses evoked by leptin. However, so far the effect of leptin on direct SNA in mice has been studied under general anesthesia. Here, we examined the sympathetic responses evoked by leptin in conscious mice. Mice were instrumented, under ketamine/xylazine anesthesia, with renal or lumbar SNA recordings using a thin (40 gauge) bipolar platinum–iridium wire. The electrodes were exteriorized at the nape of the neck and mice were allowed (5 h) to recover from anesthesia. Interestingly, the reflex increases in renal and lumbar SNA caused by sodium nitroprusside (SNP)‐induced hypotension was higher in the conscious phase versus the anesthetized state, whereas the increase in both renal and lumbar SNA evoked by leptin did not differ between anesthetized or conscious mice. Next, we assessed whether isoflurane anesthesia would yield a better outcome. Again, the SNP‐induced increase in renal SNA and baroreceptor‐renal SNA reflex were significantly elevated in the conscious states relative to isoflurane‐anesthetized phase, but the renal SNA response induced by leptin in the conscious states were qualitatively comparable to those evoked above. Thus, despite improvement in sympathetic reflexes in conscious mice the sympathetic responses evoked by leptin mimic those induced during anesthesia.

Intracranial Pressure Is a Determinant of Sympathetic Activity

Intracranial pressure (ICP) is the pressure within the cranium. ICP rise compresses brain vessels and reduces cerebral blood delivery. Massive ICP rise leads to cerebral ischemia, but it is also known to produce hypertension, bradycardia and respiratory irregularities due to a sympatho-adrenal mechanism termed Cushing response. One still unresolved question is whether the Cushing response is a non-synaptic acute brainstem ischemic mechanism or part of a larger physiological reflex for arterial blood pressure control and homeostasis regulation. We hypothesize that changes in ICP modulates sympathetic activity. Thus, modest ICP increase and decrease were achieved in mice and patients with respectively intra-ventricular and lumbar fluid infusion. Sympathetic activity was gauged directly by microneurography, recording renal sympathetic nerve activity in mice and muscle sympathetic nerve activity in patients, and gauged indirectly in both species by heart-rate variability analysis. In mice (n = 15), renal sympathetic activity increased from 29.9 ± 4.0 bursts.s−1 (baseline ICP 6.6 ± 0.7 mmHg) to 45.7 ± 6.4 bursts.s−1 (plateau ICP 38.6 ± 1.0 mmHg) and decreased to 34.8 ± 5.6 bursts.s−1 (post-infusion ICP 9.1 ± 0.8 mmHg). In patients (n = 10), muscle sympathetic activity increased from 51.2 ± 2.5 bursts.min−1 (baseline ICP 8.3 ± 1.0 mmHg) to 66.7 ± 2.9 bursts.min−1 (plateau ICP 25 ± 0.3 mmHg) and decreased to 58.8 ± 2.6 bursts.min−1 (post-infusion ICP 14.8 ± 0.9 mmHg). In patients 7 mmHg ICP rise significantly increases sympathetic activity by 17%. Heart-rate variability analysis demonstrated a significant vagal withdrawal during the ICP rise, in accordance with the microneurography findings. Mice and human results are alike. We demonstrate in animal and human that ICP is a reversible determinant of efferent sympathetic outflow, even at relatively low ICP levels. ICP is a biophysical stress related to the forces within the brain. But ICP has also to be considered as a physiological stressor, driving sympathetic activity. The results suggest a novel physiological ICP-mediated sympathetic modulation circuit and the existence of a possible intracranial (i.e., central) baroreflex. Modest ICP rise might participate to the pathophysiology of cardio-metabolic homeostasis imbalance with sympathetic over-activity, and to the pathogenesis of sympathetically-driven diseases.

111 Prognostic value of cardiac metaiodobenzylguanidine in patients with advanced heart failure: relationship with peak oxygen consumption and brain natriuretic peptide

Objectives We sought to prospectively compare the prognostic value of cardiac iodine-123 (I-123) metaiodobenzylguanidine (MIBG) imaging with peak oxygen comsumption (VO2) and plasma BNP level in patients with advanced heart failure (AHF) waiting for heart transplant. Bakground In mild to moderate heart failure, cardiac fixation of MIBG reflecting presynaptic uptake is reduced, exercise capacity is altered and plasma BNP level is increased. In AHF prognostic value of these parameters is still unknown. Methods Fifty one patients with advanced heart failure were studied with planar MIBG imaging, cardiopulmonary exercise tests, hemodynamic and neurohormonal parameters. Early (30 min) and late (4 h) MIBG acquisition, as well as their ratio (washout rate, WOR) were determined. Prognostic value was assessed by survival curves (Kaplan-Meier method) and uni- and multivariate Cox analyses. Results Early and late cardiac MIBG uptake were correlated with ejection fraction (r=0.33 and r=0.42). With a median follow up of 494 days, NYHA (p=0.03), plasma BNP (p=0.002), peak VO2 (p=0.03) were predictive of death or heart transplantation, but only plasma BNP emerged by multivariate analysis. WOR>36.63% (1st quartile) was predictive on kaplan-Meier analysis. Conclusions In AHF patients, VO2 and BNP plasma level are stronger prognosticator than MIBG imaging related parameters. MIBG should be reserved to patients with mild to moderate heart failure while BNP remains the most powerful prognostic index whatever the severity of heart failure.

114 Metaboreflex is deactivated by hyperoxia in chronic heart failure

Introduction In healthy subject hyperoxia enhances metaboreflex sensitivity during static exercise. However the influence of chronic heart failure on metaboreflex sensibility remains a matter of controversies. Moreover the effect of hyperoxia on this reflex in CHF patients is unknown. This is of importance since these patients regularly receive chronic administration of nasal oxygen during hospital admission. Methods The effects of breathing 21% (normoxia) and 100% oxygen (hyperoxia) at rest and during isometric handgrip at 30% of maximal voluntary contraction on MSNA, heart rate (HR), blood pressure (systolic, diastolic, mean and pulse pressure) and O2 saturation (DaO2) were determined in 14 patients with heart failure. The isometric handgrips were followed by 3 min of post-exercise circulation arrest (PE-CA) to allow metaboreflex activation in the absence of other reflex mechanisms. Results In normoxia, hangrip and PE-CA induced an expected increase in MSNA and hemodynamic parameters (BP, HR ; all p Conclusion In patients with chronic heart failure, hyperoxia did not altered mecanoreflex MSNA activation. In contrast, hyperoxia attenuates metaboreflex activation. This effect could lead to a diminished activation of the sympathetic nervous tone in heart failure and have beneficial effects.

112 Levosimedan improves hemodynamics functions without sympathetic activation in severe heart failure patients: direct evidence from sympathetic neural recording

Background Levosimendan is a new inodilatory agent with calcium sensitizing activity. A major concern regarding the use of inotropic agent in heart failure is their effect on the sympathetic tone. This effect could explain increase in short term mortality with other inotropes. In this setting, the aim of our study was to assess the effect of levosimendan on sympathetic tone measured directly by microneurography. Methods In a group of acute decompensated heart failure patients, we assessed cardiac performance by digital plethysmography (Finometer©) measurement. Sympathetic tone was assessed through recording of muscle sympathetic nerve activity by microneurography. Recording were done blindy, for each patient after dobutamine perfusion was stopped (baseline) and 48 hours after levosimendan infusion. Clinical, biological and morphological data were collected. We compared cardiac parameters and sympathetic nerve activity before and after administration of levosimedan. Results 13 patients with refractory chronic heart failure were recruited (aged 48±3.6 years). Systolic blood pressure and rate pressure product (mmHg × Beat/min) decreased significantly after levosimendan infusion (p Conclusion Levosimendan induced improvement of cardiac performance is associated with a decreased in MSNA. This study show for the first time that levosimendan has no direct detrimental effect on the sympathetic nervous system.

248 Ephrin-B1: a new ultrastructural protein of the cardiomyocyte

Background Ephrin-B1 is a ligand from Eph/Ephrin family involved in cell-cell interactions. If the role of ephrine molecules is well known in embryonic tissue, their expressions/functions in adult remain unclear. Aim The aim of the present work is to characterize the cardiac phenotype of two-months old ephrin-B1 knockout mice. Results Western-blot analysis demonstrated specific expression of ephrin-B1 in total heart protein extracts from WT mice that was lost in KO mice. Further IF studies demonstrated broad expression of ephrin-B1 protein throughout all heart compartments (right ventricle, septum, left ventricle) with different cellular localizations (cardiomyocytes and micro/macrocirculation). HE stained-paraffin-embedded heart sections from KO mice revealed loss of organized cardiac tissue characterized by the presence of wavy cardiomyocytes in the myocardium from septum and right/left ventricles. Modification of cardiomyocytes’ morphology correlates with a loss of their apparent lateral junctions and a significant reduction in cytoskeleton proteins (α-actinin/β-actin levels), consistent with a reduced size of the mycoytes. Ultrastructural analysis (electronic microscopy) revealed significant loss of electronic density of Z-disks and a highly packed intercalated disk (ID) with no modifications in the ID space, probably as a consequence of myocytes’ lateral junctions loss. Functional analysis of KO-mice with echocardiography revealed a significant increase in systolic and diastolic diameters of the left ventricle. Consistent with disruption of myocardial architecture, electrocardiograms demonstrated a first degree AV block together with a significant reduction of heart frequency. Conclusion This is the first report providing evidence for the presence of ephrin molecules in the adult heart tissue. This study using ephrin-B1 KO mouse identified ephrin-B1 as a new ultrastructural protein of the cardiomyocyte whose deletion leads to a dilated cardiomyopathy.

I005 Chemical denervation of sympathetic nervous system induces abnormal myocardial architecture

Introduction The role of autonomic nervous system (ANS) on heart function modulation is well-known. By contrast, ANS role on myocardial tissue architecture has scarcely been investigated. The aim of the present work was to investigate changes in heart tissue architecture after chemical sympathetic denervation by 6OH-Dopamine (6OH-DA) in mice. Methods Two months old mice (n=18) received 3 injections of 6OHDA (200xa0mg/kg, ip) or saline (n = 6) at 3 days of interval. At 15 and 30 days after first injection, ECG was recorded (PowerLab, DSI) under anaesthesia and heart rate spectral variability (HRV) was performed (FFT) in low frequency (LF: 0.15-1.5xa0Hz) and high frequency (HF: 1.5-5xa0Hz) ranges; LH/HF ratio was also calculated. After sacrifice, blood was withdrawn for plasma catecholamine determination (HPLC). Heart tissue was fixed (formaldehyde 10 %) for histology or frozen for western blot analysis (tyrosine hydroxylase, TH). Results When compared to controls (1410±145 pg/ml) plasma norepinephrine levels were significantly lower at D15 (766±186 pg/ml) and D30 (675±288 pg/ml) after 6OH-DA without significant change in epinephrine levels. TH expression was absent at D15 and present but significantly lower than in controls at D30. When compared to controls (48.5±6.2 %), LF HRV was significantly reduced at D15 (31.6±5.4 %) but not at D30 (58.2±16.2 %) without any change in HF. LF/HF ratio was lower in 6OH-DA treated mice at D15 (0.49±0.13 vs 1.29±0.17 in controls) but was normal at D30 (1.63±0.31). At D15, hearts from 6-OH-DA treated mice exhibited mild structural abnormalities with wavy cardiomyocyte appearance in septum. At D30, histological abnormalities concerned whole myocardium with myocytes intersecting at various angles with bundles wavy appearance. Variability in cell size with anisocaryosis, attenuated myocytes with perinuclear halo and shaped nuclei were observed. No inflammation, interstitial fibrosis or necrosis were noticed. Conclusion This study suggests that heart denervation induces myocardial tissue disorganization. Relationship between these pathological changes and sympathetic nerve destruction and/ or catecholamine depletion remains to be elucidated. Apart from physiological significance, these results also bring new structural basis to explain increased risk of cardiac disease during human autonomic failure.

H012 QT dynamicity predicts short term mortality in acute heart failure patient

Introduction Sympathetic overactivity increases the risk of ventricular arrhythmias. Previous studies showed that alteration of QT dynamicity, reflecting abnormal sympathetic modulation of ventricular repolarisation, is independently predictive of sudden cardiac death among patients with chronic heart failure. The aim of this study was to determine whether impaired adaptation of the QT interval to changes in heart rate also predicts death at one month in patients with acute heart failure. Methods In this study, we prospectively included 99 patients (mean age 71+/-13 years) with acute heart failure (EFxa0=xa035,2±13,4 %, BNPxa0=xa01045±83 pg/ml). Heart rate variability and QT dynamicity was evaluated by analyzing 24-h Holter recordings. The linear regression slope of QT interval measured to the apex and to the end of T wave plotted against RR intervals was calculated using dedicated Holter algorithm. Clinical, biological and morphological data were collected. Follow-up was performed by direct examination or. Results After a follow up of one month 21 patients died. Non survivors were older (76+/8 vs. 69±15 years, p Conclusion These results suggest that clinical, biological and electrical parameters issued from 24xa0hours Holter-ECG recording are able to predict short term mortality in patients with acute heart failure. These preliminary results need to be confirmed by a more extensive statistical approach currently ongoing. These predictive parameters are simple to use and their clinical or pharmacological interest need to be confirmed.

H011 Aortic valve remplacement normalizes sympathetic nerve activity in patient with severe aorticv stenosis

Introduction In patients with aortic stenosis, reduced cardiac output may increase sympathetic nerve activity. However, the magnitude of the increase in sympathetic activity in such patients and the effect of valve replacement (VR) on this activity are unknown. Methods In this preliminary study, we prospectively included 24 patients (mean agexa0=xa076,0xa0±xa08,7 years) with severe aortic stenosis (defined for Results Valve replacement induced a significant improvement in cardiac output. Holter EKG parameters evaluating the sympathetic nervous system activity showed a decrease of SDNN, VLF and LF. Hence, SDNN/5mn, eflecting sympathetic modulation of heart rate, calculated on 24xa0hours significantly decreased after aortic valve replacement (42,1±25,0 to 27,27±24xa0ms; p * for p Conclusion This study shows for the first time the beneficial effect of aortic valve replacement on the sympathetic nervous tone. We plan to follow up these patients and assess occurrence of cardiovascular complications (i.e. Heart failure, atrial fibrillation). Complimentary results will allow us to identify SNS measurement.