Reducing cardiac filling pressure lowers norepinephrine spillover in patients with chronic heart failure

Mechanisms of neurohormonal activation in chronic congestive heart failure: pathophysiology and therapeutic implications

Patients with chronic congestive heart failure have a sequential and incessant activation of those neurohormonal systems, which control body fluids, cardiac output and systemic blood pressure. Neurohormonal activation is initially selective and regional. Generalized activation is a late event in the natural history of congestive heart failure. Although the ultimate stimulus responsible for the activation of these neurohormonal systems is unknown, a decreased cardiac output and diminished effective blood volume have been proposed as the responsible mechanisms. However, extensive clinical and experimental research suggest that cardiac remodeling and loading of low-pressure cardiac receptors with sympathetic afferents could be the triggering events followed by unloading of high-pressure carotid receptors by decreased cardiac output and diminished effective blood volume.

Doppler-derived left ventricular filling pressures and the regulation of heart rate recovery after exercise in patients with suspected coronary artery disease

Slowed heart rate (HR) recovery after exercise is strongly predictive of increased long-term mortality. The factors responsible for impaired HR regulation are not fully understood. We performed echocardiography with tissue Doppler imaging in 121 patients before maximal exercise testing. HR recovery was measured 1 minute after the end of exercise in the supine position. The best echocardiographic correlate of HR recovery was the ratio of early mitral flow velocity (E) to early diastolic mitral annular velocity (Ea; r = -0.781, p <0.001). This correlation was not affected by the use of negative chronotropic agents. Patients whose E/Ea was <10 had a faster 1-minute HR recovery and a greater chronotropic response during exercise than did those whose E/Ea was >/=10. Receiver-operator characteristic analysis showed that an E/Ea >/=10.3 predicted 1-minute HR recovery of </=18 beats/min, with 83% sensitivity and 100% specificity. Neither left ventricular ejection fraction nor the presence of a "slow relaxation" mitral inflow pattern (E/A <1.0) was predictive of impaired HR recovery. Thus, slowed HR recovery is strongly associated with increased E/Ea, a marker of increased left ventricular filling pressures. E/Ea at rest may become a simple, reliable, and sensitive predictor of increased long-term mortality, even in the absence of overt heart failure.

Interaction Between Nesiritide and a Heparin-Coated Pulmonary Artery Line During an Infusion for Decompensated Heart Failure

STUDY OBJECTIVE

Because it is known that intravenous nesiritide is not compatible with unfractionated heparin, we sought to determine the effect that heparin coating on a pulmonary artery catheter may have on the efficacy of a nesiritide infusion.

METHODS

The efficacy of a nesiritide infusion given through a heparin-coated pulmonary artery line was compared with that of a nesiritide infusion administered in the same patient through a heparin-free peripheral line.

RESULTS

The rate of infusion was titrated to maintain consistent hemodynamic parameters. When nesiritide was administered through a heparin-coated line, the infusion rate escalated from 0.01 microg/kg/minute to 0.07 microg/kg/minute. After the route of administration was switched to a heparin-free line, the same hemodynamic parameters were maintained. The heparin-free line made it possible to reduce the infusion rate by 57.1% over the next 24 hours to 0.03 microg/kg/minute.

CONCLUSION

The interaction of nesiritide with heparin-coated pulmonary artery lines has the potential to be clinically significant. Clinicians should be educated about this potential interaction. Nesiritide should be infused only through heparin-free lines.

Chronic hypoxia increases blood pressure and noradrenaline spillover in healthy humans

Chronic hypoxia is associated with elevated sympathetic activity and hypertension in patients with chronic pulmonary obstructive disease. However, the effect of chronic hypoxia on systemic and regional sympathetic activity in healthy humans remains unknown. To determine if chronic hypoxia in healthy humans is associated with hyperactivity of the sympathetic system, we measured intra-arterial blood pressure, arterial blood gases, systemic and skeletal muscle noradrenaline (norepinephrine) spillover and vascular conductances in nine Danish lowlanders at sea level and after 9 weeks of exposure at 5260 m. Mean blood pressure was 28 % higher at altitude (P < 0.01) due to increases in both systolic (18 % higher, P < 0.05) and diastolic (41 % higher, P < 0.001) blood pressures. Cardiac output and leg blood flow were not altered by chronic hypoxia, but systemic vascular conductance was reduced by 30 % (P < 0.05). Plasma arterial noradrenaline (NA) and adrenaline concentrations were 3.7- and 2.4-fold higher at altitude, respectively (P < 0.05). The elevation of plasma arterial NA concentration was caused by a 3.8-fold higher whole-body NA release (P < 0.001) since whole-body noradrenaline clearance was similar in both conditions. Leg NA spillover was increased similarly (x 3.2, P < 0.05). These changes occurred despite the fact that systemic O2 delivery was greater after altitude acclimatisation than at sea level, due to 37 % higher blood haemoglobin concentration. In summary, this study shows that chronic hypoxia causes marked activation of the sympathetic nervous system in healthy humans and increased systemic arterial pressure, despite normalisation of the arterial O2 content with acclimatisation.

Sympathetic activation in human heart failure: diverse mechanisms, therapeutic opportunities

Plasma noradrenaline (NA) concentrations relate both to the severity of heart failure, and to its impact on survival, but have shortcomings that limit their usefulness as measures of sympathetic discharge. Neural recordings and the isotopic dilution method for determining organ-specific rates of NA spillover into plasma have enhanced our understanding of mechanisms responsible for sympathetic activation. Because the arterial baroreceptor reflex control of heart rate is impaired in heart failure, a parallel reduction in the reflex inhibition of sympathetic outflow has been assumed. However, human heart failure is characterized by rapidly responsive arterial baroreflex regulation of muscle sympathetic nerve activity (MSNA), attenuated cardiopulmonary reflex modulation of MSNA, and activation of a cardiac-specific sympatho-excitatory reflex related to increased cardiopulmonary filling pressures. Together, these baroreceptor mediated mechanisms account only, in part, for the time course and magnitude of adrenergic activation in heart failure. Non-baroreflex sympatho-excitatory mechanisms include: a metaboreflex arising from exercising skeletal muscle, mediated, in part, by adenosine, co-existing sleep apnoea, and pre-junctional facilitation of NA release. Thus, sympathetic activation in the setting of impaired systolic function reflects the net balance and interaction between augmented excitatory and diminished inhibitory influences. Variation, between patients, in the dynamics, magnitude and progression of sympathetic activation mandates an individualized approach to investigation and therapy. Excessive sympathetic outflow to the heart and periphery can be addressed by several complimentary strategies: attenuating these sympatho-excitatory stimuli, modulating the neural regulation of NA release, and blocking the actions of catecholamines at post-junctional receptors.

Avoidance of the left lateral decubitus position during sleep in patients with heart failure: relationship to cardiac size and function

OBJECTIVES

We sought to determine whether patients with congestive heart failure (CHF) avoid the left lateral decubitus (LLD) position during sleep and, if so, whether this avoidance would be more pronounced in those with greater degrees of cardiomegaly.

BACKGROUND

Anecdotal reports suggest that, in patients with CHF, the LLD position is associated with discomfort due to the enlarged apical heart beat and greater degree of dyspnea (trepopnea) than other positions. It has also been suggested that the LLD position is associated with increased sympathetic nervous activity.

METHODS

A total of 75 patients with CHF and 75 control subjects underwent nocturnal polysomnography with monitoring of body position. Echocardiography was performed in all patients with CHF to determine left ventricular end-diastolic diameter (LVEDD). A total of 40 patients underwent cardiac catheterization from which pulmonary capillary wedge pressure (PCWP) and cardiac output (CO) were obtained.

RESULTS

Patients with CHF spent significantly less time in the LLD position than in the right lateral decubitus position. No such difference was observed among control subjects. Among patients with CHF, those with larger LVEDD, higher PCWP, and lower CO spent less time in the LLD position.

CONCLUSIONS

Patients with CHF avoid the LLD position spontaneously during sleep. This may be a protective strategy to avoid discomfort from the enlarged apical heart beat or further hemodynamic or autonomic compromise.

Differential pre- and postsynaptic effects of desipramine on cardiac sympathetic nerve terminals in RHF

Right heart failure (RHF) is characterized by chamber-specific reductions of myocardial norepinephrine (NE) reuptake, beta-receptor density, and profiles of cardiac sympathetic nerve ending neurotransmitters. To study the functional linkage between NE uptake and the pre- and postsynaptic changes, we administered desipramine (225 mg/day), a NE uptake inhibitor, to dogs with RHF produced by tricuspid avulsion and progressive pulmonary constriction or sham-operated dogs for 6 wk. Animals receiving no desipramine were studied as controls. We measured myocardial NE uptake activity using [(3)H]NE, beta-receptor density by [(125)I]iodocyanopindolol, inotropic responses to dobutamine, and noradrenergic terminal neurotransmitter profiles by glyoxylic acid-induced histofluorescence for catecholamines, and immunocytochemical staining for tyrosine hydroxylase and neuropeptide Y. Desipramine decreased myocardial NE uptake activity and had no effect on the resting hemodynamics in both RHF and sham animals but decreased myocardial beta-adrenoceptor density and beta-adrenergic inotropic responses in both ventricles of the RHF animals. However, desipramine treatment prevented the reduction of sympathetic neurotransmitter profiles in the failing heart. Our results indicate that NE uptake inhibition facilitates the reduction of myocardial beta-adrenoceptor density and beta-adrenergic subsensitivity in RHF, probably by increasing interstitial NE concentrations, but protects the cardiac noradrenergic nerve endings from damage, probably via blockade of NE-derived neurotoxic metabolites into the nerve endings.

The effects of dobutamine on cardiac sympathetic activity in patients with congestive heart failure

OBJECTIVES

The goal of this work was to study the effects of short-term infusion of dobutamine on efferent cardiac sympathetic activity.

BACKGROUND

Increased efferent cardiac sympathetic activity is associated with poor outcomes in the setting of congestive heart failure (CHF). Dobutamine is commonly used in the therapy of decompensated CHF. Dobutamine, through its effects on excitatory beta-receptors, may increase cardiac sympathetic activity.

METHODS

Seven patients with normal left ventricular (LV) function and 13 patients with CHF were studied. A radiotracer technique was used to measure cardiac norepinephrine spillover (CANESP) before and during an intravenous infusion of dobutamine titrated to increase the rate of rise in LV peak positive pressure (+dP/dt) by 40%.

RESULTS

Systemic arterial pulse pressure increased significantly in response to dobutamine in the normal LV function group (74 +/- 3 mm Hg to 85 +/- 3 mm Hg, p = 0.005) but remained unchanged in the CHF group. Dobutamine caused a significant decrease in LV end-diastolic pressure in the CHF group (14 +/- 2 mm Hg to 11 +/- 2 mm Hg, p = 0.02), an effect not observed in the normal LV group. In the normal LV function group, CANESP did not change in response to dobutamine (75 +/- 22 pmol/min vs. 72 +/- 22 pmol/min, p = NS). In contrast, dobutamine infusion was associated with a significant reduction in CANESP in patients with CHF (199 +/- 43 pmol/min to 128 +/- 30 pmol/min, p < 0.0009).

CONCLUSIONS

Dobutamine infusion caused a significant sympatholytic response in patients with CHF. This sympathetic withdrawal response is probably related to reduction of LV filling pressures and/or activation of ventricular mechanoreceptors with dobutamine infusion.

Chronic infusion of dobutamine and nitroprusside in patients with end-stage heart failure awaiting heart transplantation: safety and clinical outcome

BACKGROUND

in patients with severe heart failure additional therapeutic support with intravenous inotropic or vasodilator drugs is frequently employed in an attempt to obtain hemodynamic and clinical control. No data comparing the use and efficacy of chronic intravenous inotropic and vasodilator therapy in patients with advanced heart failure are available.

AIMS

we evaluated, in a group of patients with advanced heart failure undergoing chronic infusion with dobutamine or nitroprusside, in addition to optimized oral therapy, (1) the safety of chronic infusion, (2) the efficacy of both drugs in managing unloading therapy and (3) clinical outcome of the two therapeutic strategies.

METHODS

one hundred and thirteen patients receiving optimized oral therapy, in functional class III/IV with symptoms and signs of refractory heart failure and requiring additional pharmacological support with either intravenous dobutamine or nitroprusside were evaluated. Clinical and therapeutic management and clinical outcome of the two groups were considered.

RESULTS

dobutamine was administered for 12 h/day for 20+/-23 days at a dosage of 7+/-3 microg/kg/min to 43 patients. The mean dose of nitroprusside was 0.76+/-0.99 microg/kg/min. The mean duration of use of this drug, administered as a 12-h/day infusion was 22+/-38 days. Nitroprusside infusion allowed greater doses of short-term ACE-inhibitors to be used compared to pre-infusion (ACE-inhibitor dose: 55+/-30 mg/day vs. 127+/-30 mg/day P<0.0001) and during dobutamine infusion (ACE-inhibitor dose: 85+/-47 mg/day vs. 127+/-30 mg/day P<0.002). Nitroprusside unlike dobutamine significantly improved the NYHA functional class. Of the 113 patients, 109 (97%) had a cardiac event during a mean follow-up of 337+/-264 days. Forty-four patients required hospitalization for worsening congestive heart failure, 45/113 (39%) patients died during the follow-up and 27/113 (24%) patients had a heart transplant in status one. Hospitalization, because of worsening heart failure was less frequent in the nitroprusside than in the dobutamine subgroup [29/51 (57%) vs. 19/22 (86%) P<0.02]. The overall mortality was 28% (20/70) in the nitroprusside group and 58% (25/43) in the dobutamine group (odds ratio 0.33 CI 0.16 to 0.73 P<0.006). In the group treated with nitroprusside, heart transplantation in status one was performed in 16/33 patients (48%), while in the dobutamine group this was done in 11/14 patients (78%) (odds ratio 0.25 CI 0.06-1.02 P<0.06). There was a significant reduction in the combined end-point of mortality/heart transplantation in status one in patients treated with nitroprusside compared to those treated with dobutamine (36/70 (51%) vs. 36/43 (84%) - (odds ratio 0.34 CI 0.14-0.80 P<0.01). The incidence of adverse events in the patients treated with nitroprusside was similar to that in those treated with dobutamine (20% vs. 17% P=ns).

CONCLUSIONS

for patients awaiting heart transplantation chronic intermittent nitroprusside infusions are more effective and safer than dobutamine in relieving symptoms, facilitating unloading therapy management and improving survival. Whether chronic intermittent infusion of nitroprusside could represent a feasible medical strategy in out-patients with severe heart failure remains to be investigated.

Prognostic importance of elevated jugular venous pressure and a third heart sound in patients with heart failure

BACKGROUND

The independent prognostic value of elevated jugular venous pressure or a third heart sound in patients with heart failure is not well established.

METHODS

We performed a retrospective analysis of the Studies of Left Ventricular Dysfunction treatment trial, in which 2569 patients with symptomatic heart failure or a history of it were randomly assigned to receive enalapril or placebo. The mean (+/-SD) follow-up was 32+/-15 months. The presence of elevated jugular venous pressure or a third heart sound was ascertained by physical examination on entry into the trial. The risks of hospitalization for heart failure and progression of heart failure as defined by death from pump failure and the composite end point of death or hospitalization for heart failure were compared in patients with these findings on physical examination and patients without these findings.

RESULTS

Data on 2479 patients were complete and analyzed. In multivariate analyses that were adjusted for other markers of the severity of heart failure, elevated jugular venous pressure was associated with an increased risk of hospitalization for heart failure (relative risk, 1.32; 95 percent confidence interval, 1.08 to 1.62; P<0.01), death or hospitalization for heart failure (relative risk, 1.30; 95 percent confidence interval, 1.11 to 1.53; P<0.005), and death from pump failure (relative risk, 1.37; 95 percent confidence interval, 1.07 to 1.75; P<0.05). The presence of a third heart sound was associated with similarly increased risks of these outcomes.

CONCLUSIONS

In patients with heart failure, elevated jugular venous pressure and a third heart sound are each independently associated with adverse outcomes, including progression of heart failure. Clinical assessment for these findings is currently feasible and clinically meaningful.

Differential sympathetic nerve and heart rate spectral effects of nonhypotensive lower body negative pressure

Lower body negative pressure (LBNP; -5 and -15 mmHg) was applied to 14 men (mean age 44 yr) to test the hypothesis that reductions in preload without effect on stroke volume or blood pressure increase selectively muscle sympathetic nerve activity (MSNA), but not the ratio of low- to high-frequency harmonic component of spectral power (P(L)/P(H)), a coarse-graining power spectral estimate of sympathetic heart rate (HR) modulation. LBNP at -5 mmHg lowered central venous pressure and had no effect on stroke volume (Doppler) or systolic blood pressure but reduced vagal HR modulation. This latter finding, a manifestation of arterial baroreceptor unloading, refutes the concept that low levels of LBNP interrogate, selectively, cardiopulmonary reflexes. MSNA increased, whereas P(L)/P(H) and HR were unchanged. This discordance is consistent with selectivity of efferent sympathetic responses to nonhypotensive LBNP and with unloading of tonically active sympathoexcitatory atrial reflexes in some subjects. Hypotensive LBNP (-15 mmHg) increased MSNA and P(L)/P(H), but there was no correlation between these changes within subjects. Therefore, HR variability has limited utility as an estimate of the magnitude of orthostatic changes in sympathetic discharge to muscle.

Increased extraction of endothelin-1 across the failing human heart

In this study we compared the transcardiac gradient of plasma endothelin-1 in patients with normal ventricular function and in those with congestive heart failure. We documented a significant reduction in the plasma levels of endothelin-1 across the failing human heart, an effect not seen in patients with normal left ventricular function.

Arterial baroreceptor and cardiopulmonary reflex control of sympathetic outflow in human heart failure

Several observations indicate that the arterial baroreflex control of sympathetic nerve activity is preserved, even in advanced heart failure. These include: (1) augmentation of muscle sympathetic nerve activity burst amplitude and duration following a premature beat; (2) rapid recognition of changes in blood pressure induced by ventricular arrhythmias; (3) muscle sympathetic alternans and a steep inverse relationship between changes in diastolic pressure and the subsequent sympathetic burst amplitude during pulsus alternans; (4) similar inhibition of muscle sympathetic nerve activity in subjects with normal and impaired left ventricular systolic function by increases in intrathoracic aortic transmural pressure; (5) documentation, by cross-spectral analysis, of similar gain in the transfer function between blood pressure and muscle sympathetic nerve activity in these two groups; and (6) during sodium nitroprusside infusion, similar reflex increases in total body norepinephrine spillover in normal and heart-failure subjects. When nonhypotensive lower-body negative pressure was applied to test the hypothesis that selective reduction of atrial and pulmonary pressures would exert a cardiac sympathoinhibitory response in heart failure, there was no effect in control subjects, but cardiac norepinephrine spillover fell by 25% (P < .05) in those with systolic dysfunction. In summary, human heart failure is characterized by a rapidly responsive and sensitive arterial baroreflex, and by activation of a cardiac sympathoexcitatory reflex related to increased cardiopulmonary filling pressures.

Effects of intravenous brain natriuretic peptide on regional sympathetic activity in patients with chronic heart failure as compared with healthy control subjects

OBJECTIVES

We sought to assess the effects of brain natriuretic peptide (BNP) on systemic and regional sympathetic nervous activity (SNA) in both patients with congestive heart failure (CHF) and healthy control subjects.

BACKGROUND

Although the response of SNA to atrial natriuretic peptide (ANP) has been well documented, the response of SNA to BNP is largely unknown.

METHODS

We assessed cardiac and whole-body SNA using the norepinephrine (NE) tracer dilution method before and after infusion of two doses of BNP (3 and 15 ng/kg body weight per min) in 11 patients with stable CHF (ejection fraction 24 +/- 2%) and 12 age-matched healthy control subjects. In addition, renal SNA and hemodynamic variables were assessed at baseline and after the higher BNP dose.

RESULTS

Low dose BNP did not change blood pressure or whole-body NE spillover, but reduced cardiac NE spillover in both groups by 32 +/- 13 pmol/min (p < 0.05). In both groups, high dose BNP reduced pulmonary capillary pressure by 5 +/- 1 mm Hg (p < 0.001) and mean arterial pressure by 6 +/- 3 mm Hg (p < 0.05), without a concomitant increase in whole-body NE spillover; however, cardiac NE spillover returned to baseline levels. Renal NE spillover remained virtually unchanged in healthy control subjects (501 +/- 120 to 564 +/- 115 pmol/min), but was reduced in patients with CHF (976 +/- 133 to 656 +/- 127 pmol/min, p < 0.01).

CONCLUSIONS

Our results demonstrate a sympathoinhibitory effect of BNP. Cardiac sympathetic inhibition was observed at BNP concentrations within the physiologic range, whereas high dose BNP, when arterial and filling pressures fell and reflex sympathetic stimulation was expected, systemic and cardiac SNA equated to baseline values. There was inhibition of renal SNA in patients with CHF, but not in healthy control subjects. Whether this effect is specific to BNP or related to reduced filling pressure remains to be determined.

Atrial natriuretic peptide augments the variability of sympathetic nerve activity in human heart failure

OBJECTIVES

Activation of the sympathetic nervous system, decreased heart rate variability (HRV), and loss of modulation of muscle sympathetic nerve activity (MSNA) within the low frequency (LF, 0.05-0.15 Hz) range are three adverse features of advanced congestive heart failure (CHF). In healthy men, atrial natriuretic peptide (ANP) infusion attenuates reflex increases in MSNA and reduces LF components of HRV spectral power. Sympathoinhibitory actions have also been documented in CHF, but effects on the variability of MSNA and HRV have not been described.

DESIGN AND METHODS

Heart rate and MSNA were recorded in 10 men (aged 39 +/- 3 years, mean +/- SE) with dilated cardiomyopathy (mean EF 20 +/- 4%) treated with angiotensin converting enzyme (ACE) inhibitors. Subjects received i.v. ANP (50 microg bolus then 50 ng/kg/min) and nitroglycerin (NTG, 8 mg/min) as a hemodynamic control. Signals at baseline, and 13-20 min into each infusion were submitted to spectral analysis.

RESULTS

ANP had no effect on HRV, but increased MSNA LF (from 7.9 +/- 1.5 to 12.1 +/- 2.6 U2; P< 0.02) and total spectral power (from 47.9 +/- 5.4 to 61.9 +/- 6.8 U2; P < 0.05). NTG had no effect on the variability of MSNA or HRV.

CONCLUSIONS

In CHF patients receiving ACE inhibitors, ANP (i) does not suppress HRV and (ii) enhances the modulation of MSNA, particularly within the LF range. This latter action is not observed with NTG. These findings suggest beneficial actions of exogenous ANP on neurogenic circulatory control.