Long-term treatment with the beta-blocker carvedilol restores autonomic tone and responsiveness in patients with moderate heart failure

The adipose-neural axis is involved in epicardial adipose tissue-related cardiac arrhythmias

Dysfunction of the sympathetic nervous system and increased epicardial adipose tissue (EAT) have been independently associated with the occurrence of cardiac arrhythmia. However, their exact roles in triggering arrhythmia remain elusive. Here, using an in vitro coculture system with sympathetic neurons, cardiomyocytes, and adipocytes, we show that adipocyte-derived leptin activates sympathetic neurons and increases the release of neuropeptide Y (NPY), which in turn triggers arrhythmia in cardiomyocytes by interacting with the Y1 receptor (Y1R) and subsequently enhancing the activity of the Na+/Ca2+ exchanger (NCX) and calcium/calmodulin-dependent protein kinase II (CaMKII). The arrhythmic phenotype can be partially blocked by a leptin neutralizing antibody or an inhibitor of Y1R, NCX, or CaMKII. Moreover, increased EAT thickness and leptin/NPY blood levels are detected in atrial fibrillation patients compared with the control group. Our study provides robust evidence that the adipose-neural axis contributes to arrhythmogenesis and represents a potential target for treating arrhythmia.

Outcomes of hypothalamic oxytocin neuron-driven cardioprotection after acute myocardial infarction

Altered autonomic balance is a hallmark of numerous cardiovascular diseases, including myocardial infarction (MI). Although device-based vagal stimulation is cardioprotective during chronic disease, a non-invasive approach to selectively stimulate the cardiac parasympathetic system immediately after an infarction does not exist and is desperately needed. Cardiac vagal neurons (CVNs) in the brainstem receive powerful excitation from a population of neurons in the paraventricular nucleus (PVN) of the hypothalamus that co-release oxytocin (OXT) and glutamate to excite CVNs. We tested if chemogenetic activation of PVN-OXT neurons following MI would be cardioprotective. The PVN of neonatal rats was transfected with vectors to selectively express DREADDs within OXT neurons. At 6 weeks of age, an MI was induced and DREADDs were activated with clozapine-N-oxide. Seven days following MI, patch-clamp electrophysiology confirmed the augmented excitatory neurotransmission from PVN-OXT neurons to downstream nuclei critical for parasympathetic activity with treatment (43.7 ± 10 vs 86.9 ± 9 pA; MI vs. treatment), resulting in stark improvements in survival (85% vs. 95%; MI vs. treatment), inflammation, fibrosis assessed by trichrome blue staining, mitochondrial function assessed by Seahorse assays, and reduced incidence of arrhythmias (50% vs. 10% cumulative incidence of ventricular fibrillation; MI vs. treatment). Myocardial transcriptomic analysis provided molecular insight into potential cardioprotective mechanisms, which revealed the preservation of beneficial signaling pathways, including muscarinic receptor activation, in treated animals. These comprehensive results demonstrate that the PVN-OXT network could be a promising therapeutic target to quickly activate beneficial parasympathetic-mediated cellular pathways within the heart during the early stages of infarction.

Pharmacological Modulation of Vagal Nerve Activity in Cardiovascular Diseases

Cardiovascular diseases are life-threatening illnesses with high morbidity and mortality. Suppressed vagal (parasympathetic) activity and increased sympathetic activity are involved in these diseases. Currently, pharmacological interventions primarily aim to inhibit over-excitation of sympathetic nerves, while vagal modulation has been largely neglected. Many studies have demonstrated that increased vagal activity reduces cardiovascular risk factors in both animal models and human patients. Therefore, the improvement of vagal activity may be an alternate approach for the treatment of cardiovascular diseases. However, drugs used for vagus nerve activation in cardiovascular diseases are limited in the clinic. In this review, we provide an overview of the potential drug targets for modulating vagal nerve activation, including muscarinic, and β-adrenergic receptors. In addition, vagomimetic drugs (such as choline, acetylcholine, and pyridostigmine) and the mechanism underlying their cardiovascular protective effects are also discussed.

Lack of improvement in autonomic cardiac tone after sacubitril/valsartan at lower than target doses

Autonomic regulation plays a role in the progression of heart failure with reduced ejection fraction (HrEF).Twenty-one HFrEF patients, 60.8 ± 13.1 years, receiving angiotensin inhibition, were replaced by angiotensin receptor-neprilysin inhibitor (ARNI). A 24-hour Holter recording was performed before and after 3 months of the maximum tolerated dose of ARNi. We evaluated changes in autonomic tone using heart rate variability (SDNN, rMSSD, pNN50, LF, HF, LF/HF, α1, α2), and heart rate turbulence (TO and TS). ARNI was up-titrated to a maximum daily dose of 190 ± 102 mg, 47.5% of the target dose. ARNI therapy was not associated with any improvement in any of the parameters related with heart rate variability or heart rate turbulence (p > 0.05 for all). ARNI use at lower than target doses did not improve autonomic cardiac tone as evaluated by 24-hour Holter monitoring.

Aberrant parasympathetic reactivity to acute psychosocial stress in male patients with schizophrenia spectrum disorders

Autonomic dysfunction represents a core domain of the pathophysiology of schizophrenia spectrum disorders (SCZ), with aberrant physiologic arousal underlying maladaptive social and cognitive behaviors. Antagonistic parasympathetic and sympathetic systems support autonomic flexibility to appropriately regulate arousal and respond to environmental challenges, which can be modeled using physiologic measures. SCZ patients consistently show heightened basal stress, however, their parasympathetic reactivity to an acute psychosocial stressor is poorly understood. Heart period (HP-arousal), respiratory sinus arrhythmia (RSA-parasympathetic vagal activity), and their relationship were measured in SCZ patients (n = 19) and healthy controls (n = 20) at baseline and during psychosocial stress exposure. Parasympathetic vagal control of arousal, reflected in RSA-HP coupling, was assessed for the first time in SCZ. Patients demonstrated blunted physiologic reactivity (less change in heart period and respiratory sinus arrhythmia), a unique increase in respiratory sinus arrhythmia relative to baseline during recovery, and elevated arousal was associated with poor cognitive performance and greater positive symptoms. Arousal regulation was tightly controlled by parasympathetic activity in controls only, indicated by a strong association between changes in heart period and respiratory sinus arrhythmia. Results are the first to demonstrate maladaptive, inefficient parasympathetic arousal regulation (RSA-HP decoupling) in reaction to psychosocial stress in SCZ, representing an autonomic profile incompatible with appropriate social and emotional functioning.

The phenotype characteristics of type 13 long QT syndrome with mutation in KCNJ5 (Kir3.4-G387R)

BACKGROUND

Long QT syndrome type 13 (LQT13) is caused by loss-of-function mutation in the KCNJ5-encoded cardiac G-protein-coupled inward rectifier potassium channel subtype 4 protein. The electrocardiographic (ECG) features of LQT13 are not described yet.

OBJECTIVE

To describe for the first time in detail the phenotype-genotype relationship of the ECG and clinical features in patients with LQT13.

METHODS

The 12-lead ECGs, 24-hour Holter recordings, and clinical information from KCNJ5-G387R mutation carriers of a fourth-generation Han Chinese family with LQT13 and a group of healthy Chinese individuals were analyzed.

RESULTS

Compared with the analysis of the healthy group (n = 8), age- and sex-matched pair analysis revealed that the mutation carriers (n = 8) had ventricular repolarization abnormality results in the prolongation of corrected QT and QTpeak intervals (P < .01); greater combined measure of repolarization morphology (T-wave morphology combination score) based on asymmetry, flatness, and notch (P < .01); and reduced low frequency/high frequency ratio of heart rate variability (P < .01) as a reflection of cardiac autonomic imbalance. Mean heart rate, time domain parameters of heart rate variability, time interval from T-wave peak to T-wave end, and T-wave amplitude were similar.

CONCLUSIONS

This study demonstrates for the first time the ECG features of patients with LQT13. Our data suggest that QTpeak intervals and T-wave morphology combination score may be the better parameters than the corrected QT interval to predict the phenotype-genotype relationship in patients with LQT13.

Geographic variation in cardioprotective antihypertensive medication usage in dialysis patients

BACKGROUND

Despite their high risk of adverse cardiac outcomes, persons on long-term dialysis therapy have had lower use of antihypertensive medications with cardioprotective properties, such as angiotensin-converting enzyme (ACE) inhibitors/angiotensin receptor blockers (ARBs), β-blockers, and calcium channel blockers, than might be expected. We constructed a novel database that permits detailed exploration into the demographic, clinical, and geographic factors associated with the use of these agents in hypertensive long-term dialysis patients.

STUDY DESIGN

National cross-sectional retrospective analysis linking Medicaid prescription drug claims with US Renal Data System core data.

SETTING & PARTICIPANTS

48,882 hypertensive long-term dialysis patients who were dually eligible for Medicaid and Medicare services in 2005.

FACTORS

Demographics, comorbid conditions, functional status, and state of residence.

OUTCOMES

Prevalence of cardioprotective antihypertensive agents in Medicaid pharmacy claims and state-specific observed to expected ORs of medication exposure.

MEASUREMENTS

Factors associated with medication use were modeled using multilevel logistic regression models.

RESULTS

In multivariable analyses, cardioprotective antihypertensive medication exposure was associated significantly with younger age, female sex, nonwhite race, intact functional status, and use of in-center hemodialysis. Diabetes was associated with a statistically significant 28% higher odds of ACE-inhibitor/ARB use, but congestive heart failure was associated with only a 9% increase in the odds of β-blocker use and no increase in ACE-inhibitor/ARB use. There was substantial state-by-state variation in the use of all classes of agents, with a greater than 2.9-fold difference in adjusted-rate ORs between the highest and lowest prescribing states for ACE inhibitors/ARBs and a 3.6-fold difference for β-blockers.

LIMITATIONS

Limited generalizability beyond study population.

CONCLUSIONS

In publicly insured long-term dialysis patients with hypertension, there were marked differences in use rates by state, potentially due in part to differences in Medicaid benefits. However, geographic characteristics also were associated with exposure, suggesting clinical uncertainty about the utility of these medications.

Evidence for impaired vagus nerve activity in heart failure

Parasympathetic control of the heart via the vagus nerve is the primary mechanism that regulates beat-to-beat control of heart rate. Additionally, the vagus nerve exerts significant effects at the AV node, as well as effects on both atrial and ventricular myocardium. Vagal control is abnormal in heart failure, occurring at early stages of left ventricular dysfunction, and this reduced vagal function is associated with worse outcomes in patients following myocardial infarction and with heart failure. While central control mechanisms are abnormal, one of the primary sites of attenuated vagal control is at the level of the parasympathetic ganglion. It remains to be seen whether or not preventing or treating abnormal vagal control of the heart improves prognosis.

A critical role of sympathetic nerve regulation for the treatment of impaired daily rhythm in hypertensive Dahl rats

There is a deep relationship between impaired circadian rhythm and hypertension. However, the detailed mechanisms between the daily sleep-wake rhythm and cardiovascular disorders have not yet been elucidated. To clarify the mechanism, we examined salt-sensitive Dahl rats that were fed normal chow (n=10), high-salt chow (n=10) and high-salt chow with bisoprolol (n=10). Simultaneous electroencephalogram, electromyogram and locomotor activity were examined to analyze the sleep-wake state. We also examined heart rate, blood pressure and echocardiographic findings to verify the presence of hypertension. Hypertension with impaired ventricular contraction was observed in the rats with high-salt-chow consumption whereas normal-chow rats did not show these disorders. Although rats with the normal diet showed a standard daily rhythm with normal rapid eye movement (REM) sleep duration and locomotor activity, the high-salt-diet group exhibited an impaired daily rhythm with suppressed REM sleep and significant abnormal locomotor activity. Bisoprolol significantly improved the daily sleep-wake rhythm and locomotor activity. We showed that an impaired daily rhythm was closely related to the development of hypertension. Regulation of sympathetic nerve alterations may have a key role in the treatment of hypertension and circadian rhythm disorder.

Different ventricular remodelling and autonomic modulation after long-term beta-blocker treatment in hypertensive, ischaemic and idiopathic dilated cardiomyopathy

OBJECTIVE

In this retrospective analysis, we investigated the influence of aetiology on autonomic modulation and reverse ventricular remodelling induced by beta-blockade in heart failure.

METHODS

Twenty-three heart failure patients without comorbidities (mean age 61 +/- 4 years, New York Heart Association class 3.1 +/- 0.1, treated with angiotensin-converting enzyme inhibitors and diuretics) were divided into three groups according to aetiology: hypertensive (group 1, n = 7), ischaemic (group 2, n = 6), and idiopathic (group 3, n = 10). Before and after 6 months of carvedilol (53 +/- 10 mg/day), patients underwent cardiopulmonary test, echocardiography and autonomic evaluation with spectral analysis of RR variability (10 min of rest plus 10 min of standing: the low frequency/high frequency ratio between low and high frequency components of each spectrum was the index of sympathovagal balance).

RESULTS

Carvedilol improved New York Heart Association class and exercise performance. In group 1, ejection fraction and left ventricular end-diastolic volume normalised, and interventricular septum thickness increased. No remodelling occurred in group 2. In group 3, interventricular septum thickness was unchanged, ejection fraction and left ventricular end-diastolic volume improved. Also autonomic modulation differed. At baseline, adrenergic activation was observed either at rest or during standing. After carvedilol treatment, group 1 did not show any change in the low frequency/high frequency ratio in both conditions, whereas groups 2 and 3 showed reduced adrenergic activation at rest and normal response to standing.

CONCLUSIONS

Despite favourable ventricular remodelling, the poor autonomic modulation observed with beta-blockade indicates a persistent central adrenergic activation in hypertensive heart failure patients.

Autonomic dysfunction in unselected and untreated primary open angle glaucoma patients: a pilot study

PURPOSE

To investigate the presence of silent cardiac ischaemic episodes and the status of autonomic function in consecutive, newly diagnosed and untreated primary open-angle glaucoma patients.

METHODS

Twenty-four consecutively diagnosed glaucoma patients and 22 age-matched controls were subjected to ambulatory 24-h blood pressure (BP) and electrocardiogram (ECG) monitoring by using Cardiotens-01 (Meditech Ltd). Based on the ECG recordings, heart rate variability (HRV) frequency domain parameters [low-frequency (LF), high-frequency (HF) and LF/HF ratio] were calculated and analysed in the two study groups.

RESULTS

Glaucoma patients demonstrated higher LF and LF/HF values than normal subjects for both the active period (p=0.020 and 0.029) and the passive period (p=0.044 and 0.049 respectively). HRV parameters were similar in patients and controls suffering from silent cardiac ischaemia (p>0.05); however, glaucoma patients with normal ECG demonstrated higher LF and LF/HF values during the active period of the 24-h measurement period than control subjects characterized by the same cardiac activity (p=0.010 and 0.021 respectively).

CONCLUSION

Independent of a history and/or clinical signs of cardiovascular disease, glaucoma patients exhibit abnormal autonomic function.

Does beta-blocker treatment influence central sleep apnoea?

Chronic severe heart failure is frequently associated with disturbances in the central control of breathing. During wakefulness, central breathing disorders could be ameliorated with beta-blocker treatment, but nothing is known about the effects of beta-blockers on the control of breathing during sleep. This study intends to determinate the prevalence and severity of nocturnal apnoeas and hypopnoeas in heart failure patients treated with or without metoprolol or carvedilol. Fifty consecutive patients with dilated cardiomyopathy in NYHA class II-IV with a left ventricular ejection fraction (LVEF) of 35% or below were studied with full polysomnography over one night. The mean Apnoea-Hypopnoea Index of beta-blocker free patients was 19.8+/-14.2 versus 7.4+/-8.5 (p<0.05) and 8.7+/-8.1 (p<0.05) in patients treated with metoprolol or carvedilol, respectively. The arousal index, sleep quality, and daytime sleepiness were improved in similar magnitude.

CONCLUSION

Long-term treatment of patients with advanced chronic heart failure with sufficient doses of metoprolol or carvedilol is associated with a lower prevalence and severity of central sleep apnoea (CSA).

Effect of adrenergic blockade on plasma adrenomedullin concentration during static handgrip in patients with heart failure

Our previous study showed that static handgrip caused increases in the plasma adrenomedullin (ADM) both in patients with heart failure (HF) and healthy subjects. The present study was designed to determine the role of the sympathetic nervous system in mediating plasma ADM changes during handgrip in patients with HF. Twelve male HF patients (II class NYHA) treated with carvedilol, a non-selective adrenergic blocker (TC) and 12 patients untreated with carvedilol (UC) performed two 3-min bouts of static handgrip at 30% of maximal voluntary contraction, alternately with each hand. At the end of both exercise bouts and in 5 min of the recovery period, plasma ADM and catecholamines were determined. In addition, heart rate, blood pressure and stroke volume (SV) were measured. The baseline plasma ADM, noradrenaline (NA) and adrenaline (A) levels were similar in the two groups of patients, while SV was higher (P<0.05) in TC than in UC. During exercise plasma ADM concentrations were lower (P<0.05) in TC than in UC, but the handgrip-induced increases in plasma ADM did not differ between the groups. Plasma ADM correlated with NA concentrations (r = 0.764) and with SV (r = -0.435) and increases in plasma ADM expressed as percentage of baseline values correlated with those of plasma NA (r = 0.499), diastolic BP (r = 0.550) and total peripheral resistance (r = 0.435). The study suggests that the sympathetic nervous system may be involved in the stimulation of ADM secretion during static exercise either directly or by changes in the haemodynamic response.

Effects of carvedilol on M2 receptors and cholinesterase-positive nerves in adriamycin-induced rat failing heart

Heart failure is correlated with attenuation of parasympathetic nervous function and enhanced sympathetic activity. Carvedilol, a third-generation beta-blocker, may improve the prognosis of heart failure better than selective beta(1)-blockers. Not all of its effects, however, can be explained by direct actions on the sympathetic nervous system. This study was therefore performed to investigate the possible alterations of muscarinic cholinergic (M)(2) receptors and cholinesterase-positive nerves in different regions of the adriamycin-induced failing rat heart, and the potential effects of carvedilol on these M(2) receptors and cholinesterase-positive nerves. Karnovsky-Roots histochemical staining combined with point counting methods, and immunochemical streptavidin-biotin complex staining and image analysis were used to test the distribution of cholinesterase-positive nerves and the expression of M(2) receptors, respectively. Our results show that the cholinesterase-positive nerve system was downregulated in the adriamycin-induced failing heart group, while the density of M(2) receptors was increased in the carvedilol 3- and 10-mg/kg body weight groups, especially in the endocardial tissues of the left-ventricular free wall. It is concluded that upregulation of M(2) receptors may be one of the potential mechanisms by which carvedilol exert its action on heart failure.