Differential effects of nonselective versus selective β-blockers on cardiac sympathetic activity and hemostasis in patients with heart failure

Prolonged corrected QT interval is associated with cardiac sympathetic nervous function overactivity in patients with severe aortic stenosis: assessment by 123I-metaiodobenzylguanidine myocardial scintigraphy

Prolonged corrected QT interval (QTc) is known to be associated with adverse cardiovascular events in patients with heart failure. The delayed heart-to-mediastinum (H/M) ratio obtained from 123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy is a marker of cardiac sympathetic nervous (CSN) activity and has been proposed as a prognostic marker of severe aortic stenosis (AS). However, the association between prolonged QTc and CSN overactivity in patients with AS remains unclear. This study retrospectively analyzed 83 patients with severe AS who underwent electrocardiography, echocardiography, and 123I-MIBG scintigraphy. Prolonged QTc was defined as QTc > 450 and > 470 ms in men and women, respectively. CSN overactivity was defined as delayed H/M ratio < 2.2 and washout rate (WR) > 34%. Prolonged QTc was detected in 14 patients, and these patients had higher left ventricular (LV) mass index and lower LV ejection fraction as compared to those with normal QTc. A significantly higher proportion of patients with prolonged QTc demonstrated CSN overactivity (p = 0.02). In addition, the prolonged QTc group had a lower delayed H/M ratio and higher WR. QTc was inversely correlated with the delayed H/M ratio in men (r =  - 0.53, p = 0.02) and women (r =  - 0.29, p = 0.02). QTc was positively correlated with WR in men (r = 0.55, p = 0.01) and women (r = 0.42, p = 0.001). Multivariate analysis identified age and prolonged QTc as significantly associated with CSN overactivity. Thus, prolonged QTc is associated with CSN overactivity, as assessed using 123I-MIBG scintigraphy in patients with severe AS.

Anti-inflammatory phenotypes of immune cells after myocardial infarction and prospects of therapeutic strategy

Often causing negative cardiac remodeling and heart failure, a major threat to human life and health, myocardial infarction (MI) is a cardiovascular disease with a high morbidity and fatality rate worldwide. Maintaining ordinary heart function depends significantly on the immune system. Necrotic cardiomyocyte signals promote specific immunity and activate general immunity as the disease progresses in MI. Complex immune cells play a key role in all stages of MI progression by removing necrotic cardiomyocytes and tissue and promoting the healing of damaged tissue cells. Immune cells can help to regrow injured heart muscle as well as enable both inflammation and cardiomyocyte death. Immune cells are essential elements that help the immune system carry out its protective function. There are two types of immunity: nonspecific immunity and specific immunity. Developed throughout the long-term evolution of species, nonspecific immunity (including macrophages, myeloid-derived suppressor cells MDSC, natural killer cells NK, neutrophils, and dendritic cells DC) offers immediate and conservative host defense that might destroy healthy tissues because of its nonspecific nature. Precisely acquired immunity, specific immunity helps humoral and cellular immunity mediated through B and T cells correspondingly. These findings offer crucial information needed for the creation of effective immunomodulatory treatment, as discussed in this article.

Improving mitochondrial function in preclinical models of heart failure: therapeutic targets for future clinical therapies?

INTRODUCTION

Heart failure is a complex clinical syndrome resulting from the unsuccessful compensation of symptoms of myocardial damage. Mitochondrial dysfunction is a process that occurs because of an attempt to adapt to the disruption of metabolic and energetic pathways occurring in the myocardium. This, in turn, leads to further dysfunction in cardiomyocyte processes. Currently, many therapeutic strategies have been implemented to improve mitochondrial function, but their effectiveness varies widely.

AREAS COVERED

This review focuses on new models of therapeutic strategies targeting mitochondrial function in the treatment of heart failure.

EXPERT OPINION

Therapeutic strategies targeting mitochondria appear to be a valuable option for treating heart failure. Currently, the greatest challenge is to develop new research models that could restore the disrupted metabolic processes in mitochondria as comprehensively as possible. Only the development of therapies that focus on improving as many dysregulated mitochondrial processes as possible in patients with heart failure will be able to bring the expected clinical improvement, along with inhibition of disease progression. Combined strategies involving the reduction of the effects of oxidative stress and mitochondrial dysfunction, appear to be a promising possibility for developing new therapies for a complex and multifactorial disease such as heart failure.

Autonomic nervous system and cardiac neuro-signaling pathway modulation in cardiovascular disorders and Alzheimer's disease

The heart is a functional syncytium controlled by a delicate and sophisticated balance ensured by the tight coordination of its several cell subpopulations. Accordingly, cardiomyocytes together with the surrounding microenvironment participate in the heart tissue homeostasis. In the right atrium, the sinoatrial nodal cells regulate the cardiac impulse propagation through cardiomyocytes, thus ensuring the maintenance of the electric network in the heart tissue. Notably, the central nervous system (CNS) modulates the cardiac rhythm through the two limbs of the autonomic nervous system (ANS): the parasympathetic and sympathetic compartments. The autonomic nervous system exerts non-voluntary effects on different peripheral organs. The main neuromodulator of the Sympathetic Nervous System (SNS) is norepinephrine, while the principal neurotransmitter of the Parasympathetic Nervous System (PNS) is acetylcholine. Through these two main neurohormones, the ANS can gradually regulate cardiac, vascular, visceral, and glandular functions by turning on one of its two branches (adrenergic and/or cholinergic), which exert opposite effects on targeted organs. Besides these neuromodulators, the cardiac nervous system is ruled by specific neuropeptides (neurotrophic factors) that help to preserve innervation homeostasis through the myocardial layers (from epicardium to endocardium). Interestingly, the dysregulation of this neuro-signaling pathway may expose the cardiac tissue to severe disorders of different etiology and nature. Specifically, a maladaptive remodeling of the cardiac nervous system may culminate in a progressive loss of neurotrophins, thus leading to severe myocardial denervation, as observed in different cardiometabolic and neurodegenerative diseases (myocardial infarction, heart failure, Alzheimer's disease). This review analyzes the current knowledge on the pathophysiological processes involved in cardiac nervous system impairment from the perspectives of both cardiac disorders and a widely diffused and devastating neurodegenerative disorder, Alzheimer's disease, proposing a relationship between neurodegeneration, loss of neurotrophic factors, and cardiac nervous system impairment. This overview is conducive to a more comprehensive understanding of the process of cardiac neuro-signaling dysfunction, while bringing to light potential therapeutic scenarios to correct or delay the adverse cardiovascular remodeling, thus improving the cardiac prognosis and quality of life in patients with heart or neurodegenerative disorders.

Targeting Adrenergic Receptors in Metabolic Therapies for Heart Failure

The heart has a reduced capacity to generate sufficient energy when failing, resulting in an energy-starved condition with diminished functions. Studies have identified numerous changes in metabolic pathways in the failing heart that result in reduced oxidation of both glucose and fatty acid substrates, defects in mitochondrial functions and oxidative phosphorylation, and inefficient substrate utilization for the ATP that is produced. Recent early-phase clinical studies indicate that inhibitors of fatty acid oxidation and antioxidants that target the mitochondria may improve heart function during failure by increasing compensatory glucose oxidation. Adrenergic receptors (α1 and β) are a key sympathetic nervous system regulator that controls cardiac function. β-AR blockers are an established treatment for heart failure and α1A-AR agonists have potential therapeutic benefit. Besides regulating inotropy and chronotropy, α1- and β-adrenergic receptors also regulate metabolic functions in the heart that underlie many cardiac benefits. This review will highlight recent studies that describe how adrenergic receptor-mediated metabolic pathways may be able to restore cardiac energetics to non-failing levels that may offer promising therapeutic strategies.

Effectiveness of beta blockers in patients with and without a history of myocardial infarction

PURPOSE

Studies demonstrating mortality benefit of beta blockers (BB) after myocardial infarction (MI) were conducted before the era of percutaneous intervention and widespread use of statins. Recent retrospective studies show inconsistent results regarding which subgroups of coronary artery disease (CAD) patients' benefit. Most studies did not account for medication changes over time. We evaluated the association of time-varying BB exposure with death in CAD patients with or without a history of MI.

METHODS

This retrospective cohort study included all patients with MI and those with coronary disease but no MI at a single health care system who also had health insurance from January 1, 1997, to June 30, 2011. Pharmacy claims data were used to estimate BB exposure over 6-month rolling windows. The primary endpoint was all-cause death. The effect of BB exposure was tested using time-updated Cox proportional hazards models.

RESULTS

We identified 6220 patients with MI and 21,285 patients with CAD but no MI. Among patients who suffered MI, BB exposure was associated with a 31% relative risk reduction in all-cause death (hazard ratio [HR] 0.69, P = 0.001). Among subjects who survived 3 years after MI, BB retained a protective association (HR 0.71, P = 0.001). Among CAD-only patients, BB exposure was also associated with risk reduction (HR 0.85, P = 0.001).

CONCLUSION

Among patients with CAD, BB exposure is associated with reduced risk of death. The association is strongest among those who have suffered MI. This favorable association appears durable beyond 3 years.

Life-Threatening Ventricular Arrhythmias: Current Role of Imaging in Diagnosis and Risk Assessment

Sudden cardiac arrest continues to be a major cause of death from cardiovascular disease but our ability to predict patients at the highest risk of developing lethal ventricular arrhythmias remains limited. Left ventricular ejection fraction is inversely related to the risk of sudden death but has a low sensitivity and specificity for the population at risk. Nevertheless, it continues to be the main variable considered in identifying patients most likely to benefit from implantable defibrillators to prevent sudden death. Imaging myocardial sympathetic innervation with PET and SPECT as well as imaging characteristics of myocardial infarcts using gadolinium-enhanced cardiac magnetic resonance are emerging as imaging modalities that may further refine patient selection beyond ejection fraction. This review will primarily focus on employing advanced imaging approaches to identify patients with left ventricular dysfunction that are most likely to develop lethal arrhythmias and benefit from inserting a primary prevention implantable cardiac defibrillator. While not yet tested in prospective studies, we will review risk prediction models incorporating quantitative imaging and biomarkers that have been developed that appear promising to identify those at highest risk of sudden death.

Pharmacogenomics of heart failure: a systematic review

BACKGROUND

Heart failure (HF) and multiple HF-related phenotypes are heritable. Genes implicated in the HF pathophysiology would be expected to influence the response to treatment.

METHODS

We conducted a series of systematic literature searches on the pharmacogenetics of HF therapy to assess the current knowledge on this field.

RESULTS

Existing data related to HF pharmacogenomics are still limited. The ADRB1 gene is a likely candidate to predict response to β-blockers. Moreover, the cytochrome P450 2D6 coding gene (CYP2D6) clearly affects the pharmacokinetics of metoprolol, although the clinical impact of this association remains to be established.

CONCLUSION

Given the rising prevalence of HF and related costs, a more personalized use of HF drugs could have a remarkable benefit for patients, caregivers and healthcare systems.

Radionuclide imaging of cardiac sympathetic innervation in heart failure: unlocking untapped potential

Heart failure (HF) is associated with sympathetic overactivity, which contributes to disease progression and arrhythmia development. Cardiac sympathetic innervation imaging can be performed using radiotracers that are taken up in the presynaptic nerve terminal of sympathetic nerves. The commonly used radiotracers are (123)I-metaiodobenzylguanidine ((123)I-mIBG) for planar and single-photon emission computed tomography imaging, and (11)C-hydroxyephedrine for positron emission tomography imaging. Sympathetic innervation imaging has been used in assessing prognosis, response to treatment, risk of ventricular arrhythmias and sudden death and prediction of response to cardiac resynchronization therapy in patients with HF. Other potential applications of these techniques are in patients with chemotherapy-induced cardiomyopathy, predicting myocardial recovery in patients with left ventricular assist devices, and assessing reinnervation following cardiac transplantation. There is a lack of standardization with respect to technique of (123)I-mIBG imaging that needs to be overcome for the imaging modality to gain popularity in clinical practice.

Heterogeneous response of cardiac sympathetic function to cardiac resynchronization therapy in heart failure documented by 11[C]-hydroxy-ephedrine and PET/CT

INTRODUCTION

Cardiac resynchronization therapy (CRT) is an accepted treatment in patients with end-stage heart failure. PET permits the absolute quantification of global and regional homogeneity in cardiac sympathetic innervation. We evaluated the variation of cardiac adrenergic activity in patients with idiopathic heart failure (IHF) disease (NYHA III-IV) after CRT using (11)C-hydroxyephedrine (HED) PET/CT.

METHODS

Ten IHF patients (mean age = 68; range = 55-81; average left ventricular ejection fraction 26 ± 4%) implanted with a resynchronization device underwent three HED PET/CT studies: PET 1 one week after inactive device implantation; PET 2, one week after PET 1 under stimulated rhythm; PET 3, at 3 months under active CRT. A dedicated software (PMOD 3.4 version) was used to estimate global and regional cardiac uptake of HED through 17 segment polar maps.

RESULTS

At baseline, HED uptake was heterogeneously distributed throughout the left ventricle with a variation coefficient of 18 ± 5%. This variable markedly decreased after three months CRT (12 ± 5%, p < 0.01). Interestingly, subdividing the 170 myocardial segments (17 segments of each patient multiplied by the number of patients) into two groups, according to the median value of tracer uptake expressed as % of maximal myocardial uptake (76%), we observed a different behaviour depending on baseline innervation: HED uptake significantly increased only in segments with "impaired innervation" (SUV 2.61 ± 0.92 at PET1 and 3.05 ± 1.67 at three months, p < 0.01).

CONCLUSION

As shown by HED PET/CT uptake and distribution, improvement in homogeneity of myocardial neuronal function reflected a selective improvement of tracer uptake in regions with more severe neuronal damage.

ADVANCES IN KNOWLEDGE

These finding supported the presence of a myocardial regional variability in response of cardiac sympathetic system to CRT and a systemic response involving remote tissues with rich adrenergic innervation.

IMPLICATION FOR PATIENT CARE

This work might contribute to identify imaging parameters that could predict the response to CRT therapy.

Autonomic dysfunction in acute ischemic stroke: an underexplored therapeutic area?

Impaired autonomic function, characterized by a predominance of sympathetic activity, is common in patients with acute ischemic stroke. This review describes methods to measure autonomic dysfunction in stroke patients. It summarizes a potential relationship between ischemic stroke-associated autonomic dysfunction and factors that have been associated with worse outcome, including cardiac complications, blood pressure variability changes, hyperglycemia, immune depression, sleep disordered breathing, thrombotic effects, and malignant edema. Involvement of the insular cortex has been suspected to play an important role in causing sympathovagal imbalance, but its exact role and that of other brain regions remain unclear. Although sympathetic overactivity in patients with ischemic stroke appears to be a negative prognostic factor, it remains to be seen whether therapeutic strategies that reduce sympathetic activity or increase parasympathetic activity might improve outcome.