The sympathetic nervous system in heart failure physiology, pathophysiology, and clinical implications

Dynamic remodeling of the guinea pig intrinsic cardiac plexus induced by chronic myocardial infarction

Myocardial infarction (MI) is associated with remodeling of the heart and neurohumoral control systems. The objective of this study was to define time-dependent changes in intrinsic cardiac (IC) neuronal excitability, synaptic efficacy, and neurochemical modulation following MI. MI was produced in guinea pigs by ligation of the coronary artery and associated vein on the dorsal surface of the heart. Animals were recovered for 4, 7, 14, or 50 days. Intracellular voltage recordings were obtained in whole mounts of the cardiac neuronal plexus to determine passive and active neuronal properties of IC neurons. Immunohistochemical analysis demonstrated an immediate and persistent increase in the percentage of IC neurons immunoreactive for neuronal nitric oxide synthase. Examination of individual neuronal properties demonstrated that after hyperpolarizing potentials were significantly decreased in both amplitude and time course of recovery at 7 days post-MI. These parameters returned to control values by 50 days post-MI. Synaptic efficacy, as determined by the stimulation of axonal inputs, was enhanced at 7 days post-MI only. Neuronal excitability in absence of agonist challenge was unchanged following MI. Norepinephrine increased IC excitability to intracellular current injections, a response that was augmented post-MI. Angiotensin II potentiation of norepinephrine and bethanechol-induced excitability, evident in controls, was abolished post-MI. This study demonstrates that MI induces both persistent and transient changes in IC neuronal functions immediately following injury. Alterations in the IC neuronal network, which persist for weeks after the initial insult, may lead to alterations in autonomic signaling and cardiac control.

Heart failure-induced changes of voltage-gated Ca2+ channels and cell excitability in rat cardiac postganglionic neurons

Chronic heart failure (CHF) is characterized by decreased cardiac parasympathetic and increased cardiac sympathetic nerve activity. This autonomic imbalance increases the risk of arrhythmias and sudden death in patients with CHF. We hypothesized that the molecular and cellular alterations of cardiac postganglionic parasympathetic (CPP) neurons located in the intracardiac ganglia and sympathetic (CPS) neurons located in the stellate ganglia (SG) possibly link to the cardiac autonomic imbalance in CHF. Rat CHF was induced by left coronary artery ligation. Single-cell real-time PCR and immunofluorescent data showed that L (Ca(v)1.2 and Ca(v)1.3), P/Q (Ca(v)2.1), N (Ca(v)2.2), and R (Ca(v)2.3) types of Ca2+ channels were expressed in CPP and CPS neurons, but CHF decreased the mRNA and protein expression of only the N-type Ca2+ channels in CPP neurons, and it did not affect mRNA and protein expression of all Ca2+ channel subtypes in the CPS neurons. Patch-clamp recording confirmed that CHF reduced N-type Ca2+ currents and cell excitability in the CPP neurons and enhanced N-type Ca2+ currents and cell excitability in the CPS neurons. N-type Ca2+ channel blocker (1 μM ω-conotoxin GVIA) lowered Ca2+ currents and cell excitability in the CPP and CPS neurons from sham-operated and CHF rats. These results suggest that CHF reduces the N-type Ca2+ channel currents and cell excitability in the CPP neurons and enhances the N-type Ca2+ currents and cell excitability in the CPS neurons, which may contribute to the cardiac autonomic imbalance in CHF.

Hyponatremia is an independent predictor of adverse clinical outcomes in hospitalized patients due to worsening heart failure

BACKGROUND AND PURPOSE

Hyponatremia is common and is associated with poor in-hospital outcomes in patients hospitalized with heart failure (HF). However, it is unknown whether hyponatremia is associated with long-term adverse outcomes. The purpose of this study was to clarify the characteristics, clinical status on admission, and management during hospitalization according to the serum sodium concentration on admission, and determine whether hyponatremia was associated with in-hospital as well as long-term outcomes in 1677 patients hospitalized with worsening HF on index hospitalization registered in the database of the Japanese Cardiac Registry of Heart Failure in Cardiology (JCARE-CARD).

METHODS AND SUBJECTS

We studied the characteristics and in-hospital treatment in 1659 patients hospitalized with worsening HF by using the JCARE-CARD database. Patients were divided into 2 groups according to serum sodium concentration on admission <135mEq/mL (n=176; 10.6%) or ≥135mEq/mL (n=1483; 89.4%).

RESULTS

The mean age was 70.7 years and 59.2% were male. Etiology was ischemic in 33.9% and mean left ventricular ejection fraction was 42.4%. After adjustment for covariates, hyponatremia was independently associated with in-hospital death [adjusted odds ratio (OR) 2.453, 95% confidence interval (CI) 1.265-4.755, p=0.008]. It was significantly associated also with adverse long-term (mean 2.1±0.8 years) outcomes including all-cause death (OR 1.952, 95% CI 1.433-2.657), cardiac death (OR 2.053, 95% CI 1.413-2.983), and rehospitalization due to worsening HF (OR 1.488, 95% CI 1.134-1.953).

CONCLUSIONS

Hyponatremia was independently associated with not only in-hospital but also long-term adverse outcomes in patients hospitalized with worsening HF.

Nonlinear methods to assess changes in heart rate variability in type 2 diabetic patients

Background

Heart rate variability (HRV) is an important indicator of autonomic modulation of cardiovascular function. Diabetes can alter cardiac autonomic modulation by damaging afferent inputs, thereby increasing the risk of cardiovascular disease. We applied nonlinear analytical methods to identify parameters associated with HRV that are indicative of changes in autonomic modulation of heart function in diabetic patients.

Objective

We analyzed differences in HRV patterns between diabetic and age-matched healthy control subjects using nonlinear methods.

Methods

Lagged Poincaré plot, autocorrelation, and detrended fluctuation analysis were applied to analyze HRV in electrocardiography (ECG) recordings.

Results

Lagged Poincare plot analysis revealed significant changes in some parameters, suggestive of decreased parasympathetic modulation. The detrended fluctuation exponent derived from long-term fitting was higher than the short-term one in the diabetic population, which was also consistent with decreased parasympathetic input. The autocorrelation function of the deviation of inter-beat intervals exhibited a highly correlated pattern in the diabetic group compared with the control group.

Conclusion

The HRV pattern significantly differs between diabetic patients and healthy subjects. All three statistical methods employed in the study may prove useful to detect the onset and extent of autonomic neuropathy in diabetic patients.

Physiology and pharmacology of the cardiovascular adrenergic system

Heart failure (HF), the leading cause of death in the western world, ensues in response to cardiac injury or insult and represents the inability of the heart to adequately pump blood and maintain tissue perfusion. It is characterized by complex interactions of several neurohormonal mechanisms that get activated in the syndrome in order to try and sustain cardiac output in the face of decompensating function. The most prominent among these neurohormonal mechanisms is the adrenergic (or sympathetic) nervous system (ANS), whose activity and outflow are greatly elevated in HF. Acutely, provided that the heart still works properly, this activation of the ANS will promptly restore cardiac function according to the fundamental Frank-Starling law of cardiac function. However, if the cardiac insult persists over time, this law no longer applies and ANS will not be able to sustain cardiac function. This is called decompensated HF, and the hyperactive ANS will continue to "push" the heart to work at a level much higher than the cardiac muscle can handle. From that point on, ANS hyperactivity becomes a major problem in HF, conferring significant toxicity to the failing heart and markedly increasing its morbidity and mortality. The present review discusses the role of the ANS in cardiac physiology and in HF pathophysiology, the mechanisms of regulation of ANS activity and how they go awry in chronic HF, and, finally, the molecular alterations in heart physiology that occur in HF along with their pharmacological and therapeutic implications for the failing heart.

Carotid chemoreceptor ablation improves survival in heart failure: rescuing autonomic control of cardiorespiratory function

OBJECTIVES

This study sought to investigate whether selective ablation of the carotid body (CB) chemoreceptors improves cardiorespiratory control and survival during heart failure.

BACKGROUND

Chronic heart failure (CHF) is a recognized health problem worldwide, and novel treatments are needed to better improve life quality and decrease mortality. Enhanced carotid chemoreflex drive from the CB is thought to contribute significantly to autonomic dysfunction, abnormal breathing patterns, and increased mortality in heart failure.

METHODS

Chronic heart failure was induced by coronary ligation in rats. Selective CB denervation was performed to remove carotid chemoreflex drive in the CHF state (16 weeks post-myocardial infarction). Indexes of autonomic and respiratory function were assessed in CB intact and CB denervated animals. CB denervation at 2 weeks post-myocardial infarction was performed to evaluate whether early targeted CB ablation decreases the progression of left ventricular dysfunction, cardiac remodeling, and arrhythmic episodes and improves survival.

RESULTS

The CHF rats developed increased CB chemoreflex drive and chronic central pre-sympathetic neuronal activation, increased indexes of elevated sympathetic outflow, increased breathing variability and apnea incidence, and desensitization of the baroreflex. Selective CB ablation reduced the central pre-sympathetic neuronal activation by 40%, normalized indexes of sympathetic outflow and baroreflex sensitivity, and reduced the incidence of apneas in CHF animals from 16.8 ± 1.8 events/h to 8.0 ± 1.4 events/h. Remarkably, when CB ablation was performed early, cardiac remodeling, deterioration of left ventricle ejection fraction, and cardiac arrhythmias were reduced. Most importantly, the rats that underwent early CB ablation exhibited an 85% survival rate compared with 45% survival in CHF rats without the intervention.

CONCLUSIONS

Carotid chemoreceptors play a seminal role in the pathogenesis of heart failure, and their targeted ablation might be of therapeutic value to reduce cardiorespiratory dysfunction and improve survival during CHF.

The role and management of sympathetic overactivity in cardiovascular and renal complications of diabetes

Feedback activation of neurohormonal pathways in the setting of kidney or heart failure contributes to the development and progression of dysfunction in the other. Diabetes and its management independently activate these same pathogenic pathways, feeding into this vicious cycle and contributing to a poor prognosis. One of the most important of these neurohormonal pathways is the sympathetic nervous system (SNS). The activity of the SNS in increased in patients with chronic kidney disease, even in the absence of renal impairment or heart failure. There is a strong relationship between SNS overactivity and prognosis, and evidence that blockade of SNS reduces morbidity and mortality in patients with diabetes. However, modulation of SNS is underutilised as a strategy to protect both the diabetic kidney and the heart. This is partly because of the historically poor tolerability, adverse haemodynamic and metabolic effects, lack of selectivity of β-blockers and the lack of specificity of other interventions that might modify SNS activation. The advent of "vasodilating β-blockers" with better tolerability as well as more favourable effects on renal function and metabolic profiles opens the door for their more widespread utility in patients with diabetes. Radiofrequency renal sympathectomy and baroreflex activation technologies also offer exciting new ways to tackle the challenge of sympathetic overactivity.

Adrenergic nervous system in heart failure: pathophysiology and therapy

Heart failure (HF), the leading cause of death in the western world, develops when a cardiac injury or insult impairs the ability of the heart to pump blood and maintain tissue perfusion. It is characterized by a complex interplay of several neurohormonal mechanisms that become activated in the syndrome to try and sustain cardiac output in the face of decompensating function. Perhaps the most prominent among these neurohormonal mechanisms is the adrenergic (or sympathetic) nervous system (ANS), whose activity and outflow are enormously elevated in HF. Acutely, and if the heart works properly, this activation of the ANS will promptly restore cardiac function. However, if the cardiac insult persists over time, chances are the ANS will not be able to maintain cardiac function, the heart will progress into a state of chronic decompensated HF, and the hyperactive ANS will continue to push the heart to work at a level much higher than the cardiac muscle can handle. From that point on, ANS hyperactivity becomes a major problem in HF, conferring significant toxicity to the failing heart and markedly increasing its morbidity and mortality. The present review discusses the role of the ANS in cardiac physiology and in HF pathophysiology, the mechanisms of regulation of ANS activity and how they go awry in chronic HF, methods of measuring ANS activity in HF, the molecular alterations in heart physiology that occur in HF, along with their pharmacological and therapeutic implications, and, finally, drugs and other therapeutic modalities used in HF treatment that target or affect the ANS and its effects on the failing heart.

Relation of short-term heart rate variability to incident heart failure (from the Multi-Ethnic Study of Atherosclerosis)

Whether autonomic dysfunction predates the development of symptomatic heart failure (HF) or is simply a consequence of severe HF is unknown. We hypothesized that reduced heart rate variability (a marker of abnormal autonomic function) at baseline is associated with incident HF in subjects free of clinically recognized cardiovascular disease. In the Multi-Ethnic Study of Atherosclerosis (MESA), a population-based study of subclinical cardiovascular disease in adults aged 45 to 84 years, we measured the heart rate variability using a standard 30-second, 12-lead electrocardiogram to measure the standard deviation of normal-to-normal intervals (SDNN) and the root mean square of successive differences in RR intervals (RMSSD). During a median follow-up of 7.6 years, 95 participants developed HF (incidence rate 2.7/1,000 person-years). After adjusting for age, gender, and ethnicity, the hazard ratio for incident HF stratified by the RMSSD tertile was 2.4 (95% confidence interval 1.4 to 4.2) for the lowest tertile and 1.7 (95% confidence interval 1.0 to 3.2) for the middle tertile (highest tertile was the referent group; p for trend <0.001). The inverse association between the RMSSD and incident HF persisted after adjustment for additional covariates, including diabetes, systolic blood pressure, heart rate, subclinical atherosclerosis, left ventricular end-systolic volume, interim myocardial infarction, and high-sensitivity C-reactive protein (p for trend = 0.009). A similarly significant inverse association was also observed for SDNN. In conclusion, baseline autonomic dysfunction was a risk factor for the development of HF in a multiethnic cohort. These population-based findings implicate autonomic dysfunction in the pathogenesis of HF, and decreased short-term heart rate variability might be a novel form of stage B (asymptomatic) HF.

Deletion of the β2-adrenergic receptor prevents the development of cardiomyopathy in mice

Beta adrenergic receptor (β-AR) subtypes act through diverse signaling cascades to modulate cardiac function and remodeling. Previous in vitro studies suggest that β1-AR signaling is cardiotoxic whereas β2-AR signaling is cardioprotective, and may be the case during ischemia/reperfusion in vivo. The objective of this study was to assess whether β2-ARs also play a cardioprotective role in the pathogenesis of non-ischemic forms of cardiomyopathy. To dissect the role of β1 vs β2-ARs in modulating MLP (Muscle LIM Protein) cardiomyopathy, we crossbred MLP-/- with β1-/- or β2-/- mice. Deletion of the β2-AR improved survival, cardiac function, exercise capacity and myocyte shortening; by contrast haploinsufficency of the β1-AR reduced survival. Pathologic changes in Ca(2+) handling were reversed in the absence of β2-ARs: peak Ca(2+) and SR Ca(2+) were decreased in MLP-/- and β1+/-/MLP-/- but restored in β2-/-MLP-/-. These changes were associated with reversal of alterations in troponin I and phospholamban phosphorylation. Gi inhibition increased peak and baseline Ca(2+), recapitulating changes observed in the β2-/-/MLP-/-. The L-type Ca(2+) blocker verapamil significantly decreased cardiac function in β2-/-MLP-/- vs WT. We next tested if the protective effects of β2-AR ablation were unique to the MLP model using TAC-induced heart failure. Similar to MLP, β2-/- mice demonstrated delayed progression of heart failure with restoration of myocyte shortening and peak Ca(2+) and Ca(2+) release. Deletion of β2-ARs prevents the development of MLP-/- cardiomyopathy via positive modulation of Ca(2+) due to removal of inhibitory Gi signaling and increased phosphorylation of troponin I and phospholamban. Similar effects were seen after TAC. Unlike previous models where β2-ARs were found to be cardioprotective, in these two models, β2-AR signaling appears to be deleterious, potentially through negative regulation of Ca(2+) dynamics.

A pooled analysis of multicenter cohort studies of (123)I-mIBG imaging of sympathetic innervation for assessment of long-term prognosis in heart failure

OBJECTIVES

The study objectives were to create a cardiac metaiodobenzylguanidine (mIBG) database using multiple prospective cohort studies and to determine the quantitative iodine-123-labeled mIBG indices for identifying patients with chronic heart failure (HF) at greatest and lowest risk of lethal events.

BACKGROUND

Although the prognostic value of cardiac mIBG imaging in patients with HF has been shown, clinical use of this procedure has been limited. It is required to define universally accepted quantitative thresholds for high and low risk that could be used as an aid to therapeutic decision-making using a large cohort database.

METHODS

Six prospective HF cohort studies were updated, and the individual datasets were combined for the present patient-level analysis. The database consisted of 1,322 patients with HF followed up for a mean interval of 78 months. Heart-to-mediastinum ratio (HMR) and washout rate of cardiac mIBG activity were the primary cardiac innervation markers. The primary outcome analyzed was all-cause death.

RESULTS

Lethal events were observed in 326 patients, and the population mortality rate was 5.6%, 11.3%, and 19.7% at 1, 2, and 5 years, respectively. Multivariate Cox proportional hazard model analysis for all-cause mortality identified age (p < 0.0001), New York Heart Association (NYHA) functional class (p < 0.0001), late HMR of cardiac mIBG activity (p < 0.0001), and left ventricular ejection fraction (LVEF) (p = 0.0029) as significant independent predictors. Analysis of the 512-patient subpopulation with B-type natriuretic peptide (BNP) results showed BNP (p < 0.0001), greater NYHA functional class (p = 0.0002), and late HMR (p = 0.0011) as significant predictors, but LVEF was not. The receiver-operating characteristic-determined threshold of HMR (1.68) identified patients at significantly increased risk in any LVEF category. Survival rates decreased progressively with decreasing HMR, with 5-year all-cause mortality rates >7% annually for HMR <1.25, and <2% annually for HMR ≥1.95. Addition of HMR to clinical information resulted in a significant net reclassification improvement of 0.175 (p < 0.0001).

CONCLUSIONS

Pooled analyses of independent cohort studies confirmed the long-term prognostic value of cardiac mIBG uptake in patients with HF independently of other markers, such as NYHA functional class, BNP, and LVEF, and demonstrated that categoric assessments could be used to define meaningful thresholds for lethal event risk.

Observer reproducibility of results from a low-dose 123I-metaiodobenzylguanidine cardiac imaging protocol in patients with heart failure

PURPOSE

Imaging of the cardiac autonomic system with (123)I-metaiodobenzylguanidine (MIBG) is useful in the evaluation of patients with a variety of cardiac conditions, including heart failure (HF), but few data are available about the reproducibility of this technique. We assessed the observer reproducibility of the results from a low-dose (123)I-MIBG cardiac imaging protocol in patients with HF.

METHODS

A total of 74 patients (62 men, age 67 ± 10 years) with HF and left ventricular systolic dysfunction (ejection fraction 31 ± 7 %) underwent low-dose (111 MBq) planar and single-photon emission computed tomography (SPECT) (123)I-MIBG cardiac sympathetic imaging. The intraclass coefficient of correlation (ICC), Lin's concordance correlation coefficient, and Bland-Altman analysis were used to evaluate the intraobserver and interobserver reproducibility of early and late heart-to-mediastinum (H/M) ratios and of defect scores on SPECT images. The κ statistic was used to evaluate the concordance rates for the identification of patients with a low H/M ratio (<1.60) on late planar imaging.

RESULTS

The differences between measurements obtained twice by the same examiner and by two examiners were negligible for both early and late H/M ratios and for SPECT defect scores. These findings were confirmed by the results of Bland-Altman analysis, and ICC and Lin's coefficient values were excellent (>0.90) for all measurements. For the identification of patients with a low H/M ratio, the κ values were 0.90 for intraobserver concordance and 0.83 for interobserver concordance.

CONCLUSION

The present study showed a high observer reproducibility of planar H/M ratios and SPECT defect scores using a low-dose (123)I-MIBG cardiac imaging protocol in patients with HF.

Cardiac Autonomic Dysfunction in the Early Phase after Left Ventricular Assist Device Implant: Implications for Surgery and Follow-Up?

Purpose

In congestive heart failure (CHF) patients, a profound cardiac autonomic derangement, clinically expressed by reduced heart rate variability (HRV), is present and is related to the degree of ventricular dysfunction. Implantation of a left ventricular assist device (LVAD) can progressively improve HRV, associated with an increased circulatory output. Data from patients studied at different times after LVAD implantation are controversial. The aims of this study were to assess cardiac autonomic function in the early phases after axial-flow LVAD implantation, and to estimate the potential relevance of recent major surgical stress on the autonomic balance.

Methods

HRV (time-domain; 24-h Holter) was evaluated in 14 patients, 44.8 ± 25.8 days after beginning of Jarvik-2000 LVAD support; 47 advanced stage CHF, 24 cardiac surgery (CS) patients and 30 healthy subjects served as control groups. Inclusion criteria: sinus rhythm, stable clinical conditions, no diabetes or other known causes of HRV alteration.

Results

HRV was considerably reduced in LVAD patients in the early phases after device implantation in comparison to all control groups. A downgrading of HRV parameters was also present in CS controls. Circadian oscillations were highly depressed in LVAD and CHF patients, and slightly reduced in CS patients.

Conclusions

In CHF patients supported by a continuous-flow LVAD, a profound cardiac dysautonomia is still evident in the first two months from the beginning of circulatory support; the degree of cardiac autonomic imbalance is even greater in comparison to advanced CHF patients. The recent surgical stress could be partly linked to these abnormalities.

Iodine-123-metaiodobenzylguanidine scintigraphy in risk stratification of sudden death in heart failure

Metaiodobenzylguanidine (MIBG) is a false neurotransmitter noradrenaline analogue that is taken up by the 'uptake 1' transporter mechanism in the cell membrane of presynaptic adrenergic neurons and accumulates in catecholamine storage vesicles. Since it is practically unmetabolized, it can be labeled with a radioisotope (iodine-123) in scintigraphic exams to noninvasively assess the functional status of the sympathetic innervation of organs with a significant adrenergic component, including the heart. Studies of its application in nuclear cardiology appear to confirm its value in the assessment of conditions such as coronary artery disease, heart failure, arrhythmias and sudden death. Heart failure is a global problem, with an estimated prevalence of 2% in developed countries. Sudden cardiac death is the main cause of its high mortality. The autonomic nervous system dysfunction, including sympathetic hyperactivity, that accompanies chronic heart failure is associated with progressive myocardial remodeling, declining left ventricular function and worsening symptoms, and contributes to the development of ventricular arrhythmias and sudden death. Since 123I-MIBG cardiac scintigraphy can detect changes in the cardiac adrenergic system, there is considerable interest in its role in obtaining diagnostic and prognostic information in patients with heart failure. In this article we present a literature review on the use of 123I-MIBG scintigraphy for risk stratification of sudden death in patients with heart failure.

The blockade of angiotensin AT1 and aldosterone receptors protects rats from synthetic androgen-induced cardiac autonomic dysfunction

AIM

This study aimed to evaluate the combined effects of exercise and antagonists of the angiotensin II and aldosterone receptors on cardiac autonomic regulation and ventricular repolarization in rats chronically treated with nandrolone decanoate (ND), a synthetic androgen.

METHODS

Thirty male Wistar rats were divided into six groups: sedentary, trained, ND-treated, trained and ND-treated, trained and treated with both ND and spironolactone, and trained and treated with both ND and losartan. ND (10 mg kg(-1) weekly) and the antagonists (20 mg kg(-1) daily) of the angiotensin II AT1 (losartan) and aldosterone (spironolactone) receptors were administered for 8 weeks. Exercise training was performed using a treadmill five times each week for 8 weeks. Following this 8-week training and treatment period, electrocardiogram recordings were obtained to determine the time and frequency domains of heart rate variability (HRV) and corrected QT interval (QTc).

RESULTS

Nandrolone decanoate treatment increased the QTc interval and reduced the parasympathetic indexes of HRV (RMSSD, pNN5 and high-frequency power) in sedentary and trained rats. The ratio between low- and high-frequency power (LF/HF) was higher in ND-treated groups. Both losartan and spironolactone treatments prevented the effects of ND on the QTc interval and the HRV parameters (RMSSD, pNN5, high-frequency power, and the LF/HF ratio).

CONCLUSION

Our results show that chronic treatment with a high dose of ND induces cardiac parasympathetic dysfunction and disturbances in ventricular repolarization in both sedentary and exercised rats. Furthermore, inhibiting the renin-angiotensin-aldosterone system using losartan, or spironolactone, prevented these deleterious effects.

Autonomic cardiac innervation: development and adult plasticity

Autonomic cardiac neurons have a common origin in the neural crest but undergo distinct developmental differentiation as they mature toward their adult phenotype. Progenitor cells respond to repulsive cues during migration, followed by differentiation cues from paracrine sources that promote neurochemistry and differentiation. When autonomic axons start to innervate cardiac tissue, neurotrophic factors from vascular tissue are essential for maintenance of neurons before they reach their targets, upon which target-derived trophic factors take over final maturation, synaptic strength and postnatal survival. Although target-derived neurotrophins have a central role to play in development, alternative sources of neurotrophins may also modulate innervation. Both developing and adult sympathetic neurons express proNGF, and adult parasympathetic cardiac ganglion neurons also synthesize and release NGF. The physiological function of these “non-classical” cardiac sources of neurotrophins remains to be determined, especially in relation to autocrine/paracrine sustenance during development.

 

Cardiac autonomic nerves are closely spatially associated in cardiac plexuses, ganglia and pacemaker regions and so are sensitive to release of neurotransmitter, neuropeptides and trophic factors from adjacent nerves. As such, in many cardiac pathologies, it is an imbalance within the two arms of the autonomic system that is critical for disease progression. Although this crosstalk between sympathetic and parasympathetic nerves has been well established for adult nerves, it is unclear whether a degree of paracrine regulation occurs across the autonomic limbs during development. Aberrant nerve remodeling is a common occurrence in many adult cardiovascular pathologies, and the mechanisms regulating outgrowth or denervation are disparate. However, autonomic neurons display considerable plasticity in this regard with neurotrophins and inflammatory cytokines having a central regulatory function, including in possible neurotransmitter changes. Certainly, neurotrophins and cytokines regulate transcriptional factors in adult autonomic neurons that have vital differentiation roles in development. Particularly for parasympathetic cardiac ganglion neurons, additional examinations of developmental regulatory mechanisms will potentially aid in understanding attenuated parasympathetic function in a number of conditions, including heart failure.

Heart disease as a risk factor for dementia

As life expectancy lengthens, dementia is becoming a significant human condition in terms of its prevalence and cost to society worldwide. It is important in that context to understand the preventable and treatable causes of dementia. This article exposes the link between dementia and heart disease in all its forms, including coronary artery disease, myocardial infarction, atrial fibrillation, valvular disease, and heart failure. This article also explores the cardiovascular risk factors and emphasizes that several of them are preventable and treatable. In addition to medical therapies, the lifestyle changes that may be useful in retarding the onset of dementia are also summarized.

The cardiorenal syndrome in heart failure: cardiac? renal? syndrome?

There has been increasing interest on the so-called cardiorenal syndrome (CRS), defined as a complex pathophysiological disorder of the heart and kidneys whereby acute or chronic dysfunction in one organ may induce acute or chronic dysfunction in the other. In this review, we contend that there is lack of evidence warranting the adoption of a specific clinical construct such as the CRS within the heart failure (HF) syndrome by demonstrating that: (a) the approaches and tools regarding the definition of kidney involvement in HF are suboptimal; (b) development of renal failure in HF is often confounded by age, hypertension, and diabetes; (c) worsening of renal function (WRF) in HF may be largely independent of alterations in cardiac function; (d) the bidirectional association between HF and renal failure is not unique and represents one of the several such associations encountered in HF; and (e) inflammation is a common denominator for HF and associated noncardiac morbidities. Based on these arguments, we believe that dissecting one of the multiple bidirectional associations in HF and constructing the so-called cardiorenal syndrome is not justified pathophysiologically. Fully understanding of all morbid associations and not only the cardiorenal is of great significance for the clinician who is caring for the patient with HF.

Discrepant fibrinolytic response in plasma and whole blood during experimental endotoxemia in healthy volunteers

Background

Sepsis induces early activation of coagulation and fibrinolysis followed by late fibrinolytic shutdown and progressive endothelial damage. The aim of the present study was to investigate and compare the functional hemostatic response in whole blood and plasma during experimental human endotoxemia by the platelet function analyzer, Multiplate and by standard and modified thrombelastography (TEG).

Methods

Prospective physiologic study of nine healthy male volunteers undergoing endotoxemia by means of a 4-hour infusion of E. coli lipopolysaccharide (LPS, 0.5 ng/kg/hour), with blood sampled at baseline and at 4 h and 6 h. Physiological and standard biochemical data and coagulation tests, TEG (whole blood: TEG, heparinase-TEG, Functional Fibrinogen; plasma: TEG±tissue-type plasminogen activator (tPA)) and Multiplate (TRAPtest, ADPtest, ASPItest, COLtest) were recorded. Mixed models with Tukey post hoc tests and correlations were applied.

Results

Endotoxemia induced acute SIRS with increased HR, temperature, WBC, CRP and procalcitonin and decreased blood pressure. It also induced a hemostatic response with platelet consumption and reduced APTT while INR increased (all p<0.05). Platelet aggregation decreased (all tests, p<0.05), whereas TEG whole blood clot firmness increased (G, p = 0.05). Furthermore, during endotoxemia (4 h), whole blood fibrinolysis increased (clot lysis time (CLT), p<0.001) and Functional Fibrinogen clot strength decreased (p = 0.049). After endotoxemia (6 h), whole blood fibrinolysis was reduced (CLT, p<0.05). In contrast to findings in whole blood, the plasma fibrin clot became progressively more resistant towards tPA-induced fibrinolysis at both 4 h and 6 h (p<0.001).

Conclusions

Endotoxemia induced a hemostatic response with reduced primary but enhanced secondary hemostasis, enhanced early fibrinolysis and fibrinogen consumption followed by downregulation of fibrinolysis, with a discrepant fibrinolytic response in plasma and whole blood. The finding that blood cells are critically involved in the vasculo-fibrinolytic response to acute inflammation is important given that disturbances in the vascular system contribute significantly to morbidity and mortality in critically ill patients.

Neurocardiological differences between musicians and control subjects

BACKGROUND

Exercise training is beneficial in health and disease. Part of the training effect materialises in the brainstem due to the exercise-associated somatosensory nerve traffic. Because active music making also involves somatosensory nerve traffic, we hypothesised that this will have training effects resembling those of physical exercise.

METHODS

We compared two groups of healthy, young subjects between 18 and 30 years: 25 music students (13/12 male/female, group M) and 28 controls (12/16 male/female, group C), peers, who were non-musicians. Measurement sessions to determine resting heart rate, resting blood pressure and baroreflex sensitivity (BRS) were held during morning hours.

RESULTS

Groups M and C did not differ significantly in age (21.4 ± 3.0 vs 21.2 ± 3.1 years), height (1.79 ± 0.11 vs 1.77 ± 0.10 m), weight (68.0 ± 9.1 vs 66.8 ± 10.4 kg), body mass index (21.2 ± 2.5 vs 21.3 ± 2.4 kg∙m(-2)) and physical exercise volume (39.3 ± 38.8 vs 36.6 ± 23.6 metabolic equivalent hours/week). Group M practised music daily for 1.8 ± 0.7 h. In group M heart rate (65.1 ± 10.6 vs 68.8 ± 8.3 beats/min, trend P =0.08), systolic blood pressure (114.2 ± 8.7 vs 120.3 ± 10.0 mmHg, P = 0.01), diastolic blood pressure (65.0 ± 6.1 vs 71.0 ± 6.2 mmHg, P < 0.01) and mean blood pressure (83.7 ± 6.4 vs 89.4 ± 7.1, P < 0.01) were lower than in group C. BRS in groups M and C was 12.9 ± 6.7 and 11.3 ± 5.8 ms/mmHg, respectively (P = 0.17).

CONCLUSIONS

The results of our study suggest that active music making has training effects resembling those of physical exercise training. Our study opens a new perspective, in which active music making, additionally to being an artistic activity, renders concrete health benefits for the musician.

Effect of educational program on quality of life of patients with heart failure: a randomized clinical trial

INTRODUCTION

Heart failure is one of the most common cardiovascular diseases which decrease the quality of life. Most of the factors influencing the quality of life can be modified with educational interventions. Therefore, this study examined the impact of a continuous training program on quality of life of patients with heart failure.

METHODS

This randomized clinical trial study was conducted during May to August 2011. Forty four participants with heart failure referred to Shahid Madani's polyclinics of Tabriz were selected through convenient sampling method and were randomly allocated to two groups. The intervention group (n = 22) received ongoing training including one-to-one teaching, counseling sessions and phone calls over 3 months. The control group (n = 22) received routine care program. Data on quality of life was collected using the Minnesota Living with Heart Failure Questionnaire at baseline as well as three months later.

RESULTS

The statistical tests showed significant differences in the physical, emotional dimensions and total quality of life in intervention group. But in control group, no significant differences were obtained. There was not any significant association in demographic characteristics and quality of life.

CONCLUSION

Ongoing training programs can be effective in improving quality of life of patients with heart failure. Hence applying ongoing educational program as a non-pharmacological intervention can help to improve the quality of life of these patients.

Inhibition of hydrogen sulfide restores normal breathing stability and improves autonomic control during experimental heart failure

Cardiovascular autonomic imbalance and breathing instability are major contributors to the progression of heart failure (CHF). Potentiation of the carotid body (CB) chemoreflex has been shown to contribute to these effects. Hydrogen sulfide (H2S) recently has been proposed to mediate CB hypoxic chemoreception. We hypothesized that H2S synthesis inhibition should decrease CB chemoreflex activation and improve breathing stability and autonomic function in CHF rats. Using the irreversible inhibitor of cystathione γ-lyase dl-propargylglycine (PAG), we tested the effects of H2S inhibition on resting breathing patterns, the hypoxic and hypercapnic ventilatory responses, and the hypoxic sensitivity of CB chemoreceptor afferents in rats with CHF. In addition, heart rate variability (HRV) and systolic blood pressure variability (SBPV) were calculated as an index of autonomic function. CHF rats, compared with sham rats, exhibited increased breath interval variability and number of apneas, enhanced CB afferent discharge and ventilatory responses to hypoxia, decreased HRV, and increased low-frequency SBPV. Remarkably, PAG treatment reduced the apnea index by 90%, reduced breath interval variability by 40-60%, and reversed the enhanced hypoxic CB afferent and chemoreflex responses observed in CHF rats. Furthermore, PAG treatment partially reversed the alterations in HRV and SBPV in CHF rats. Our results show that PAG treatment restores breathing stability and cardiac autonomic function and reduces the enhanced ventilatory and CB chemosensory responses to hypoxia in CHF rats. These results support the idea that PAG treatment could potentially represent a novel pathway to control sympathetic outflow and breathing instability in CHF.

Acute myocardial infarction is associated with endothelial glycocalyx and cell damage and a parallel increase in circulating catecholamines

Introduction

Excessive sympathoadrenal activation in critical illness contributes directly to organ damage, and high concentrations of catecholamines damage the vascular endothelium. This study investigated associations between potential drivers of sympathoadrenal activation, circulating catecholamines and biomarkers of endothelial damage and outcome in ST segment elevation myocardial infarction (STEMI)-patients, hypothesizing that the catecholamine surge would reflect shock degree and correlate with biomarkers of endothelial damage.

Methods

This was a prospective study of 678 consecutive STEMI-patients admitted to a single high-volume invasive heart centre for primary percutaneous coronary intervention (pPCI) from September 2006 to July 2008. Blood samples were drawn immediately before pPCI. Plasma adrenaline, noradrenaline, syndecan-1 and thrombomodulin were measured retrospectively with complete data in 571 patients (84%). Median follow-up time was 28 (IQR 23 to 34) months. Follow-up was 99.7% complete. Outcomes were all-cause and cardiovascular mortality, re-myocardial infarction and admission due to heart failure.

Results

Circulating noradrenaline and adrenaline correlated weakly but independently with syndecan-1 (rho = 0.15 and rho = 0.13, both P <0.01) and thrombomodulin (rho = 0.11 and rho = 0.17, both P <0.01), biomarkers of glycocalyx and endothelial cell damage, respectively. Considering biomarkers, patients with shock pre-pPCI had higher adrenaline and syndecan-1 and patients admitted to ICU post-pPCI had higher syndecan-1 (all P <0.05), and in the patients with shock (n = 51) catecholamines correlated strongly with thrombomodulin and syndecan-1 (rho = 0.31 to 0.42, all P <0.05). During follow-up, 78 (14%) patients died (37 cardiovascular deaths) and 65 (11%) were admitted with heart failure. By multivariate Cox proportional hazards analyses, one quartile higher plasma adrenaline was weakly but independently associated with both 30-day and long term mortality and heart failure (30-day all-cause mortality hazard ratio (95% CI) 1.39 (1.01 to 1.92), P = 0.046; 30-day heart failure 1.65 (1.17 to 2.34), P = 0.005; and long-term cardiovascular mortality 1.49 (1.08 to 2.04), P = 0.014). Furthermore, one quartile higher syndecan-1 was also weakly but independently associated with long-term all cause mortality (1.26 (1.02 to 1.57), P = 0.034).

Conclusions

In STEMI patients treated with pPCI, catecholamines correlated weakly with biomarkers of endothelial damage, with the strongest correlations and highest adrenaline and syndecan-1 levels in patients with shock. Furthermore, adrenaline and syndecan-1 were weakly but independently associated with mortality and heart failure. Acute myocardial infarction appears to cause significant endothelial cell and glycocalyx injury and a parallel increase in circulating catecholamines.

'Ryanopathy': causes and manifestations of RyR2 dysfunction in heart failure

The cardiac ryanodine receptor (RyR2), a Ca(2+) release channel on the membrane of the sarcoplasmic reticulum (SR), plays a key role in determining the strength of the heartbeat by supplying Ca(2+) required for contractile activation. Abnormal RyR2 function is recognized as an important part of the pathophysiology of heart failure (HF). While in the normal heart, the balance between the cytosolic and intra-SR Ca(2+) regulation of RyR2 function maintains the contraction-relaxation cycle, in HF, this behaviour is compromised by excessive post-translational modifications of the RyR2. Such modification of the Ca(2+) release channel impairs the ability of the RyR2 to properly deactivate leading to a spectrum of Ca(2+)-dependent pathologies that include cardiac systolic and diastolic dysfunction, arrhythmias, and structural remodelling. In this article, we present an overview of recent advances in our understanding of the underlying causes and pathological consequences of abnormal RyR2 function in the failing heart. We also discuss the implications of these findings for HF therapy.

Cardiac autonomic imaging with SPECT tracers

Radionuclide cardiac imaging has potential to assess underlying molecular, electrophysiologic, and pathophysiologic processes of cardiac disease. An area of current interest is cardiac autonomic innervation imaging with a radiotracer such as (123)I-meta-iodobenzylguanidine ((123)I-mIBG), a norepinephrine analogue. Cardiac (123)I-mIBG uptake can be assessed by planar and SPECT techniques, involving determination of global uptake by a heart-to-mediastinal ratio, tracer washout between early and delayed images, and focal defects on tomographic images. Cardiac (123)I-mIBG findings have consistently been shown to correlate strongly with heart failure severity, pre-disposition to cardiac arrhythmias, and poor prognosis independent of conventional clinical, laboratory, and image parameters. (123)I-mIBG imaging promises to help monitor a patient's clinical course and response to therapy, showing potential to help select patients for an ICD and other advanced therapies better than current methods. Autonomic imaging also appears to help diagnose ischemic heart disease and identify higher risk, as well as risk-stratify patients with diabetes. Although more investigations in larger populations are needed to strengthen prior findings and influence modifications of clinical guidelines, cardiac (123)I-mIBG imaging shows promise as an emerging technique for recognizing and following potentially life-threatening conditions, as well as improving our understanding of the pathophysiology of various diseases.

Blockade of different subtypes of α(1)-adrenoceptors produces opposite effect on heart chronotropy in newborn rats

We compared the effects of blockade of α(1A)-, α(1B)-, and α(1D)-subtypes of α(1)-adrenoceptors on the cardiac rhythm in newborn rats. Different responses of the heart were observed after blockade of several subtypes of α(1)-adrenoceptors. Administration of WB 4101, a selective blocker of α(1A)-adrenoceptors, increased heart rate, while blockade of α(1AD)-adrenoceptors with BMY 7378 decelerated of heart rhythm. Blockade of α(1B)-adrenoceptors with chloroethylclonidine produced no significant effects on heart chronotropy.

Diabetic cardiovascular autonomic neuropathy: clinical implications

Diabetic cardiovascular autonomic neuropathy (DCAN), the impairment of the autonomic balance of the cardiovascular system in the setting of diabetes mellitus (DM), is frequently observed in both Type 1 and 2 DM, has detrimental effects on the quality of life and portends increased mortality. Clinical manifestations include: resting heart rate disorders, exercise intolerance, intraoperative cardiovascular lability, orthostatic alterations in heart rate and blood pressure, QT-interval prolongation, abnormal diurnal and nocturnal blood pressure variation, silent myocardial ischemia and diabetic cardiomyopathy. Clinical tests for autonomic nervous system evaluation, heart rate variability analysis, autonomic innervation imaging techniques, microneurography and baroreflex analysis are the main diagnostic tools for DCAN detection. Aldose reductase inhibitors and antioxidants may be helpful in DCAN therapy, but a regular, more generalized and multifactorial approach should be adopted with inclusion of lifestyle modifications, strict glycemic control and treatment of concomitant traditional cardiovascular risk factors, in order to achieve the best therapeutic results. In the present review, the authors provide aspects of DCAN pathophysiology, clinical presentation, diagnosis and an algorithm regarding the evaluation and management of DCAN in DM patients.

High E/e' disrupts the rapid lowering of blood glucose in response to exercise training

BACKGROUND

No relationship between the ratio of peak early velocity of left ventricular inflow to peak systolic longitudinal velocity of the mitral annulus velocity (E/e') and insulin resistance has yet been shown in patients with cardiac disease. We hypothesized that patients with high E/e' values would tend not to show the rapid blood glucose-lowering in response to exercise training characteristic of impaired glucose tolerance (IGT) or diabetes mellitus (DM) patients.

METHODS

The subjects were continuous IGT/DM patients (n = 27) participating in cardiac rehabilitation. All patients' E/e' values were measured by echocardiography. The patients' blood glucose levels (mg/dl) were measured just before (pre-BS) and after (post-BS) exercise training. Post-BS was subtracted from pre-BS to obtain ΔBS, and the relationship between E/e' and ΔBS was investigated.

RESULTS

E/e' correlated negatively with ΔBS. Moreover, E/e' was a significant predictor of ΔBS and as such was independent of hemoglobin A1c (HbA1c), pre-BS, and presence of atrial fibrillation on multivariate analysis.

CONCLUSIONS

Patients with high E/e', indicating high left ventricular filling pressure, were unlikely to exhibit the rapid glucose-lowering response.

Rethinking Heart Failure

An increasing body of clinical observations and experimental evidence suggests that cardiac dysfunction results from autonomic dysregulation of the contractile output of the heart. Excessive activation of the sympathetic nervous system and a decrease in parasympathetic tone are associated with increased mortality. Elevated levels of circulating catecholamines closely correlate with the severity and poor prognosis in heart failure. Sympathetic over-stimulation causes increased levels of catecholamines, which induce excessive aerobic metabolism leading to excessive cardiac oxygen consumption. Resulting impaired mitochondrial function causes acidosis, which results in reduction in blood flow by impairment of contractility. To the extent that the excessive aerobic metabolism resulting from adrenergic stimulation comes to a halt the energy deficit has to be compensated for by anaerobic metabolism. Glucose and glycogen become the essential nutrients. Beta-adrenergic blockade is used successfully to decrease hyperadrenergic drive. Neurohumoral antagonists block adrenergic over-stimulation but do not provide the heart with fuel for compensatory anaerobic metabolism. The endogenous hormone ouabain reduces catecholamine levels in healthy volunteers, promotes the secretion of insulin, induces release of acetylcholine from synaptosomes and potentiates the stimulation of glucose metabolism by insulin and acetylcholine. Ouabain stimulates glycogen synthesis and increases lactate utilisation by the myocardium. Decades of clinical experience with ouabain confirm the cardioprotective effects of this endogenous hormone. The so far neglected sympatholytic and vagotonic effects of ouabain on myocardial metabolism clearly make a clinical re-evaluation of this endogenous hormone necessary. Clinical studies with ouabain that correspond to current standards are warranted.

Heart Rate Variability Biofeedback for Postconcussion Syndrome: Implications for Treatment

Heart Rate Variability (HRV) Biofeedback is used to restore balance in the activity of the sympathetic and parasympathetic branches of the autonomic nervous system by increasing or reducing the activity of either. Researchers have postulated that a fundamental cause of refractory postconcussion syndrome (PCS) is physiologic dysfunction that fails to return to normal after concussion. The primary physiologic issues identified have been altered autonomic function and impaired cerebral autoregulation. Evidence has shown that aerobic exercise training increases parasympathetic activity, reduces sympathetic activation, and improves cerebral blood flow so it may, therefore, help to reduce concussion-related physiological dysfunction. The authors hypothesize that HRV biofeedback training will ameliorate PCS by improving autonomic balance as well as cerebral autoregulation, and that there will be a relationship between increased interval variability and postconcussion symptom reduction.

Comorbid Heart Failure and Renal Impairment: Epidemiology and Management

Heart failure mortality is significantly increased in patients with baseline renal impairment and those with underlying heart failure who subsequently develop renal dysfunction. This accelerated progression occurs independent of the cause or grade of renal dysfunction and baseline risk factors. Recent large prospective databases have highlighted the depth of the current problem, while longitudinal population studies support an increasing disease burden. We have extensively reviewed the epidemiological and therapeutic data among these patients. The evidence points to a progression of heart failure early in renal impairment, even in the albuminuric stage. The data also support poor prescription of prognostic therapies. As renal function is the most important prognostic factor in heart failure, it is important to establish the current understanding of the disease burden and the therapeutic implications.

β-adrenergic receptor polymorphisms in susceptibility, response to treatment and prognosis in heart failure: implication of ethnicity

Common functional polymorphisms in β-adrenergic receptor (βAR) genes have been associated with heart failure (HF) phenotypes and pharmacogenetic interactions with βAR blockers. This study evaluated the association between βAR polymorphisms and carvedilol drug response and prognosis in patients with HF. In this prospective cohort controlled study, 326 volunteers were enrolled [146 HF patients (ejection fraction (EF)<50% by Simpson) and 180 healthy controls]. Drug response was evaluated by echocardiography and outcomes were mortality and hospitalization. DNA was extracted from peripheral blood leukocytes, fragments were amplified by the polymerase reaction and genotyped by restriction fragment length polymorphism (RFLP) for Ser49Gly and Arg389Gly βAR-1 polymorphisms and Gln27Glu and Arg16Gly βAR-2 polymorphisms. The study population was in Hardy‑Weinberg equilibrium. The survival rate was adjusted using the Kaplan-Meier method. HF patients showed the following characteristics: EF 35±9%, 69.9% male, age 59±13 years, 50.7% self-identified as black, 46% had ischemic etiology. The mean follow-up of 23 months showed 18 mortalities and 46 hospitalizations. The genotypes Glu27Glu (24.7 vs. 6.1%, p=0.0004) and Arg16Arg (72.6 vs. 22.8, p<0.0001) of βAR2 polymorphisms and Gly49Gly (33.6 vs. 4.3%, p<0.0001) of the βAR1 polymorphism were higher in HF patients compared with controls. Patients with hospital admission showed a significantly higher Gly389 allelic frequency (54.9 vs. 42.1%, p=0.039), and the trend prevailed among patients who succumbed to the disease (61.1%, p=0.047). Black patients with the Ser49Ser genotype showed a reduced survival compared with the Gly49Gly or Ser49Gly genotypes (p=0.028). There was no association between improved LVEF >20% and βAR polymorphisms. HF patients with β-blocker therapy and the Gly389 allele have reduced event-free survival compared to those carrying the Arg389 allele. Additionally, systolic HF outpatients undergoing β-blocker therapy, self‑identified as black and homozygous for Ser49Ser may have reduced event-free survival, while Glu27Glu, Arg16Arg and Gly49Gly genotypes may be associated with risk for HF.

Resting heart rate and incident heart failure in apparently healthy men and women in the EPIC-Norfolk study

AIMS

Increasing levels of resting heart rate are associated with increased risk of developing hypertension and cardiovascular disease, and seem to play a role in the progression of heart failure. The shape of the association between resting heart rate and risk of developing heart failure has not been examined in healthy individuals of the general population.

METHODS AND RESULTS

Hazard ratios (HRs) of heart failure comparing categories of resting heart rate [51-60 b.p.m. (reference), 61-70 b.p.m., 71-80 b.p.m., 81-90 b.p.m., and 91-100 b.p.m.] were calculated in apparently healthy men (9805) and women (12 321) aged 39-79 participating in the 'European Prospective Investigation into Cancer and Nutrition' (EPIC) study in Norfolk. During a mean follow-up of 12.9 years, 1356 incident cases of heart failure occurred. In participants without potential heart rate-modifying medication, age- and sex-adjusted incidence rates of heart failure were 3.3, 3.7, 4.0, 5.1, and 5.5 per 1000 person-years for increasing categories of resting heart rate; compared with the reference category, HRs and 95% confidence intervals (CI) for increasing categories of resting heart rate were 1.08 (0.88-1.34), 1.17 (0.94-1.46), 1.39 (1.08-1.79), and 1.42 (1.00-2.03), respectively, in multivariable analysis adjusting for age, sex, body mass index, systolic blood pressure, prevalent diabetes, cholesterol concentration, social class, educational level, smoking, and physical activity. Within the reference range of resting heart rate (50-100 b.p.m.) each 10 b.p.m. increase was associated with an 11% increase in hazard of heart failure in multivariable analysis. The results did not change materially after adjusting for myocardial infarction and coronary heart disease events during follow up (1.12, 1.06-1.18).

CONCLUSION

Resting heart rate shows a graded association with hazard of heart failure in apparently healthy men and women which is not mediated by coronary heart disease. Further study is needed to examine the underlying mechanisms.

Acute myocardial infarction inhibits the neurogenic tachycardic and vasopressor response in rats via presynaptic cannabinoid type 1 receptor

The present study was carried out to examine whether acute experimental myocardial infarction affects the sympathetic transmission to vessels and the heart of pithed rats via a presynaptic mechanism and, if so, to check whether inhibitory presynaptic cannabinoid (CB) receptors and endocannabinoids are involved in this response. In pithed and vagotomized rats, electrical stimulation (0.75 Hz; 1 ms; 50 V; 5 or 15 pulses for increases in heart rate or blood pressure, respectively) of the preganglionic sympathetic nerve fibers or intravenous injection of isoprenaline (0.1 nmol/kg) or noradrenaline (1 nmol/kg) increased heart rate and blood pressure by approximately 50 beats/min and 40 mm Hg, respectively. Ligation of the left coronary artery reduced the electrically (as opposed to the chemically) induced tachycardic and pressor responses by approximately 30 to 40%. The inhibitory effect of myocardial infarction was prevented by the CB(1) receptor antagonist rimonabant but not by the CB(2) receptor antagonist N-[(1S)-endo-1,3,3-trimethyl-bicyclo[2.2.1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyra-zole-3-carboxamide (SR144528) and the transient receptor potential vanilloid 1 receptor antagonist capsazepine. The inhibitory effect of myocardial infarction was slightly enhanced by the inhibitors of anandamide and 2-arachidonyl glycerol degradation, 3'-(aminocarbonyl)[1,1'-biphenyl]-3-yl)-cyclohexylcarbamate (URB597) and 4-nitrophenyl-4-(dibenzo[d][1,3]dioxol-5-yl(hydroxy)methyl)piperidine-1-carboxylate (JZL184), respectively. Rimonabant increased myocardial infarction-induced mortality. Our results demonstrate that during the early phase of myocardial infarction the activation of presynaptic CB(1) receptors by endogenously formed cannabinoids contributes to the inhibition of the neurogenic tachycardic and vasopressor responses. Thus, the CB(1) receptor-mediated inhibition of excessive noradrenaline release from the sympathetic nerve fibers innervating the heart and vessels might play a protective role in myocardial ischemia.

Effects of renal sympathetic denervation on post-myocardial infarction cardiac remodeling in rats

OBJECTIVE

To investigate the therapeutic effects of renal denervation (RD) on post- myocardial infarction (MI) cardiac remodeling in rats, the most optimal time for intervention and the sustainability of these effects.

METHODS

One hundred SPF male Wistar rats were randomly assigned to N group (Normal, n=10), MI group(MI, n=20),RD group (RD, n=10), RD3+MI (MI three days after RD, n=20), MI1+RD (RD one day after MI, n=20), MI7+RD (RD seven days after MI, n=20). MI was produced through thoracotomic ligation of the anterior descending artery. RD was performed through laparotomic stripping of the renal arteriovenous adventitial sympathetic nerve. Left ventricular function, hemodynamics, plasma BNP, urine volume, urine sodium excretion and other indicators were measured four weeks after MI.

RESULTS

(1) The left ventricular function of the MI group significantly declined (EF<40%), plasma BNP was elevated, urine output was significantly reduced, and 24-hour urine sodium excretion was significantly reduced. (2) Denervation can be achieved by surgically stripping the arteriovenous adventitia, approximately 3 mm from the abdominal aorta. (3) In rats with RD3+MI, MI1+RD and MI7+RD, compared with MI rats respectively, the LVEF was significantly improved (75 ± 8.4%,69 ± 3.8%,73 ± 5.5%), hemodynamic indicators were significantly improved, plasma BNP was significantly decreased, and the urine output was significantly increased (21.3 ± 5 ml,23.8 ± 5.4 ml,25.2 ± 8.7 ml). However, the urinary sodium excretion also increased but without significant difference.

CONCLUSIONS

RD has preventive and therapeutic effects on post-MI cardiac remodeling.These effects can be sustained for at least four weeks, but there were no significant differences between denervation procedures performed at different times in the course of illness. Cardiac function, hemodynamics, urine volume and urine sodium excretion in normal rats were not affected by RD.

Catheter-based renal denervation for resistant hypertension: rationale and design of the SYMPLICITY HTN-3 Trial

Hypertension represents a significant global public health concern, contributing to vascular and renal morbidity, cardiovascular mortality, and economic burden. The opportunity to influence clinical outcomes through hypertension management is therefore paramount. Despite adherence to multiple available medical therapies, a significant proportion of patients have persistent blood pressure elevation, a condition termed resistant hypertension. Recent recognition of the importance of the renal sympathetic and somatic nerves in modulating blood pressure and the development of a novel procedure that selectively removes these contributors to resistant hypertension represents an opportunity to provide clinically meaningful benefit across wide and varied patient populations. Early clinical evaluation with catheter-based, selective renal sympathetic denervation in patients with resistant hypertension has mechanistically correlated sympathetic efferent denervation with decreased renal norepinephrine spillover and renin activity, increased renal plasma flow, and has demonstrated clinically significant, sustained reductions in blood pressure. The SYMPLICITY HTN-3 Trial is a pivotal study designed as a prospective, randomized, masked procedure, single-blind trial evaluating the safety and effectiveness of catheter-based bilateral renal denervation for the treatment of uncontrolled hypertension despite compliance with at least 3 antihypertensive medications of different classes (at least one of which is a diuretic) at maximal tolerable doses. The primary effectiveness endpoint is measured as the change in office-based systolic blood pressure from baseline to 6 months. This manuscript describes the design and methodology of a regulatory trial of selective renal denervation for the treatment of hypertension among patients who have failed pharmacologic therapy.

Relationship between HbA1c levels and risk of cardiovascular adverse outcomes and all-cause mortality in overweight and obese cardiovascular high-risk women and men with type 2 diabetes

AIMS/HYPOTHESIS

The optimal HbA(1c) concentration for prevention of macrovascular complications and deaths in obese cardiovascular high-risk patients with type 2 diabetes remains to be established and was therefore studied in this post hoc analysis of the Sibutramine Cardiovascular OUTcomes (SCOUT) trial, which enrolled overweight and obese patients with type 2 diabetes and/or cardiovascular disease.

METHODS

HRs for meeting the primary endpoint (nonfatal myocardial infarction, nonfatal stroke, resuscitated cardiac arrest or cardiovascular death) and all-cause mortality were analysed using Cox regression models.

RESULTS

Of 8,252 patients with type 2 diabetes included in SCOUT, 7,479 had measurements of HbA(1c) available at baseline (i.e. study randomisation). Median age was 62 years (range 51-86 years), median BMI was 34.0 kg/m(2) (24.8-65.1 kg/m(2)) and 44% were women. The median HbA(1c) concentration was 7.2% (3.8-15.9%) (55 mmol/l [18-150 mmol/l]) and median diabetes duration was 7 years (0-57 years). For each 1 percentage point HbA(1c) increase, the adjusted HR for the primary endpoint was 1.17 (95% CI 1.11, 1.23); no differential sex effect was observed (p = 0.12 for interaction). In contrast, the risk of all-cause mortality was found to be greater in women than in men: HR 1.22 (1.10, 1.34) vs 1.12 (1.04, 1.20) for each 1 percentage point HbA(1c) increase (p = 0.02 for interaction). There was no evidence of increased risk associated with HbA(1c) ≤ 6.4% (≤ 46 mmol/l). Glucose-lowering treatment regimens, diabetes duration or a history of cardiovascular disease did not modify the associations.

CONCLUSIONS/INTERPRETATION

In overweight, cardiovascular high-risk patients with type 2 diabetes, increasing HbA(1c) concentrations were associated with increasing risks of cardiovascular adverse outcomes and all-cause mortality.

Remodeling of intrinsic cardiac neurons: effects of β-adrenergic receptor blockade in guinea pig models of chronic heart disease

Chronic heart disease induces remodeling of cardiac tissue and associated neuronal components. Treatment of chronic heart disease often involves pharmacological blockade of adrenergic receptors. This study examined the specific changes in neuronal sensitivity of guinea pig intrinsic cardiac neurons to autonomic modulators in animals with chronic cardiac disease, in the presence or absence of adrenergic blockage. Myocardial infarction (MI) was produced by ligature of the coronary artery and associated vein on the dorsal surface of the heart. Pressure overload (PO) was induced by a banding of the descending dorsal aorta (∼20% constriction). Animals were allowed to recover for 2 wk and then implanted with an osmotic pump (Alzet) containing either timolol (2 mg·kg(-1)·day(-1)) or vehicle, for a total of 6-7 wk of drug treatment. At termination, intracellular recordings from individual neurons in whole mounts of the cardiac plexus were used to assess changes in physiological responses. Timolol treatment did not inhibit the increased sensitivity to norepinephrine seen in both MI and PO animals, but it did inhibit the stimulatory effects of angiotensin II on the norepinephrine-induced increases in neuronal excitability. Timolol treatment also inhibited the increase in synaptically evoked action potentials observed in PO animals with stimulation of fiber tract bundles. These results demonstrate that β-adrenergic blockade can inhibit specific aspects of remodeling within the intrinsic cardiac plexus. In addition, this effect was preferentially observed with active cardiac disease states, indicating that the β-receptors were more influential on remodeling during dynamic disease progression.