Impact of aging on cardiac sympathetic innervation measured by 123I-mIBG imaging in patients with systolic heart failure. Eur J Nucl Med Mol Imaging. 2016;43:2392-2400. [PMID: 27287990 DOI: 10.1007/s00259-016-3432-3]

Iodine-123 Metaiodobenzylguanidine (I-123 MIBG) in Clinical Applications: A Comprehensive Review

Iodine-123 metaiodobenzylguanidine (I-123 MIBG) is a crucial radiopharmaceutical widely used in nuclear medicine for its diagnostic capabilities in both cardiology and oncology. This review aims to present a comprehensive evaluation of the clinical applications of I-123 MIBG, focusing on its use in diagnosing and managing various diseases. In cardiology, I-123 MIBG has proven invaluable in assessing cardiac sympathetic innervation, particularly in patients with heart failure, where it provides prognostic information that guides treatment strategies. In oncology, I-123 MIBG is primarily utilized for imaging neuroendocrine tumors, such as neuroblastoma and pheochromocytoma, where it offers high specificity and sensitivity in the detection of adrenergic tissue. Additionally, its role in neurology, specifically in differentiating between Parkinson's disease, dementia, and Lewy body dementia, has become increasingly significant due to its ability to identify postganglionic sympathetic dysfunction. Despite its established clinical utility, the use of I-123 MIBG is not without limitations, including variability in imaging protocols and interpretation challenges. This review will explore these issues and discuss emerging alternatives, while also highlighting areas where I-123 MIBG continues to be a gold standard. By synthesizing the current research, this article aims to provide a clear understanding of the strengths, limitations, and prospects of I-123 MIBG in clinical practice.

Renal Denervation in Heart Failure Treatment: Data for a Self-Fulfilling Prophecy

Renal denervation (RDN), a transcatheter renal sympathetic nerve ablation procedure, is a relatively novel established procedure for the treatment of hypertension, with it being recognized as a third option for hypertension management in the most recent European guidelines, together with pharmacotherapy, for achieving blood pressure targets. Given the relationship between both hypertension and sympathetic overdrive and the development of heart failure (HF), even studies at the dawn of research on RDN explored it as a treatment to overcome diuretic resistance in those patients. As it is now recognized that RDN does not only have organ-specific but also systemic effects, several investigators have aimed to delineate whether renal sympathetic denervation could alter the prognosis, symptoms, and adverse events of HF patients. Data are available in both HF patients with reduced and preserved ejection fraction. As the significance of neuromodulation is gaining grounds in the HF therapeutic arsenal, in this review, we aim to provide a rationale for using RDN in HF and an up-to-date overview of available data in both HF phenotypes, as well as discuss the future of neuromodulatory therapy in HF management.

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.

123I-MIBG imaging in heart failure: impact of comorbidities on cardiac sympathetic innervation

PURPOSE

Heart failure (HF) is a primary cause of morbidity and mortality worldwide, with significant impact on life quality and extensive healthcare costs. Assessment of myocardial sympathetic innervation function plays a central role in prognosis assessment in HF patients. The aim of this review is to summarize the most recent evidence regarding the clinical applications of iodine-123 metaiodobenzylguanidine (¹²³I-MIBG) imaging in patients with HF and related comorbidities.

METHODS

A comprehensive literature search was conducted on PubMed and Web of Science databases. Articles describing the impact of ¹²³I-MIBG imaging on HF and related comorbidities were considered eligible for the review.

RESULTS

We collected several data reporting that ¹²³I-MIBG imaging is a safe and non-invasive tool to evaluate dysfunction of cardiac sympathetic neuronal function and to assess risk stratification in HF patients. HF is frequently associated with comorbidities that may affect cardiac adrenergic innervation. Furthermore, HF is frequently associated with comorbidities and chronic conditions, such as diabetes, obesity, kidney disease and others, that may affect cardiac adrenergic innervation.

CONCLUSION

Comorbidities and chronic conditions lead to more severe impairment of sympathetic nervous system in patients with HF, with a negative impact on disease progression and outcome. Cardiac imaging with ¹²³I-MIBG can be a useful tool to reduce morbidity and prevent adverse events in HF patients.

Sex/Gender- and Age-Related Differences in β-Adrenergic Receptor Signaling in Cardiovascular Diseases

Sex differences in cardiovascular disease (CVD) are often recognized from experimental and clinical studies examining the prevalence, manifestations, and response to therapies. Compared to age-matched men, women tend to have reduced CV risk and a better prognosis in the premenopausal period. However, with menopause, this risk increases exponentially, surpassing that of men. Although several mechanisms have been provided, including sex hormones, an emerging role in these sex differences has been suggested for β-adrenergic receptor (β-AR) signaling. Importantly, β-ARs are the most important G protein-coupled receptors (GPCRs), expressed in almost all the cell types of the CV system, and involved in physiological and pathophysiological processes. Consistent with their role, for decades, βARs have been considered the first targets for rational drug design to fight CVDs. Of note, β-ARs are seemingly associated with different CV outcomes in females compared with males. In addition, even if there is a critical inverse correlation between β-AR responsiveness and aging, it has been reported that gender is crucially involved in this age-related effect. This review will discuss how β-ARs impact the CV risk and response to anti-CVD therapies, also concerning sex and age. Further, we will explore how estrogens impact β-AR signaling in women.

Usefulness of the 2-year iodine-123 metaiodobenzylguanidine-based risk model for post-discharge risk stratification of patients with acute decompensated heart failure

PURPOSE

A four-parameter risk model that included cardiac iodine-123 metaiodobenzylguanidine (MIBG) imaging and readily available clinical parameters was recently developed for prediction of 2-year cardiac mortality risk in patients with chronic heart failure. We sought to validate the ability of this risk model to predict post-discharge clinical outcomes in patients with acute decompensated heart failure (ADHF) and to compare its prognostic value with that of the Acute Decompensated Heart Failure National Registry (ADHERE) and Get With The Guidelines-Heart Failure (GWTG-HF) risk scores.

METHODS

We studied 407 consecutive patients who were admitted for ADHF and survived to discharge, with definitive 2-year outcomes (death or survival). Cardiac MIBG imaging was performed just before discharge. The 2-year cardiac mortality risk was calculated using four parameters, namely age, left ventricular ejection fraction, New York Heart Association functional class, and cardiac MIBG heart-to-mediastinum ratio on delayed images. Patients were stratified into three groups based on the 2-year cardiac mortality risk: low- (< 4%), intermediate- (4-12%), and high-risk (> 12%) groups. The ADHERE and GWTG-HF risk scores were also calculated.

RESULTS

There was a significant difference in the incidence of cardiac death among the three groups stratified using the 2-year cardiac mortality risk model (p < 0.0001). The 2-year cardiac mortality risk model had a higher C-statistic (0.732) for the prediction of cardiac mortality than the ADHERE and GWTG-HF risk scores.

CONCLUSION

The 2-year MIBG-based cardiac mortality risk model is useful for predicting post-discharge clinical outcomes in patients with ADHF.

TRIAL REGISTRATION NUMBER

UMIN000015246, 25 September 2014.

Relationship between heart rate response and cardiac innervation in patients with suspected or known coronary artery disease

BACKGROUND

Chronotropic response to pharmacological stress test is blunted in patients with autonomic neuropathy. The relationship between heart rate (HR) changes during pharmacological stress test and cardiac autonomic dysfunction has not been fully investigated. We assessed the potential interplay between HR response (HRR) and myocardial innervation in patients with suspected or known coronary artery disease (CAD).

METHODS AND RESULTS

We studied 71 patients with suspected or known CAD referred to pharmacological stress myocardial perfusion imaging and 123I metaiodobenzylguanidine (123I-MIBG) cardiac scintigraphy. HRR was calculated as the maximum percent change from baseline according to the formula: (peak HR - rest HR)/rest HR × 100. 123I-MIBG heart-to-mediastinum (H/M) ratio was calculated and a late H/M ratio < 1.6 was considered abnormal. HRR progressively decreased with decreasing late H/M ratio (P for trend = 0.02) and a significant correlation between HRR and late H/M ratio (P = 0.03) was observed. The addition of HRR to a model including age, diabetes, known CAD, left ventricular ejection fraction, and stress-induced ischemia added incremental value in predicting an abnormal late H/M ratio, increasing the global chi-square from 8.09 to 13.8 (P = 0.02).

CONCLUSIONS

The relationship between HRR and cardiac sympathetic innervation in patients with suspected or known CAD confirms a strong interplay between cardiac response to stress tests and cardiac autonomic activation. This finding suggests that HRR may be used as a surrogate for assessing cardiac sympathetic function.

Factors Influencing Cardiac Sympathetic Nervous Function in Patients With Severe Aortic Stenosis: Assessment by 123I-Metaiodobenzylguanidine Myocardial Scintigraphy

BACKGROUND

Numerous studies have shown that 123I-metaiodobenzylguanidine (MIBG) scintigraphy, an index of cardiac sympathetic nervous (CSN) activity, is useful for predicting prognosis in patients with heart failure. However, the factors influencing the CSN activity of patients with severe aortic stenosis (AS) remain unclear.

METHODS

We enrolled 91 patients with severe AS who underwent 123I-MIBG scintigraphy, coronary computed tomography (CCT), and transthoracic echocardiography. When CCT angiography (CCTA) showed an obstructive epicardial artery, invasive coronary angiography was performed within 1 week of CCTA.

RESULTS

There were 21 male and 70 female patients with a mean age of 84±5 years. Eighty-five (85) patients (93%) had hypertension and 13 patients (14%) had diabetes. Two (2) patients (2%) had previous myocardial infarction and eight (9%) had a previous coronary intervention. All patients had severe AS: aortic valve area was 0.63±0.18 cm² and the mean pressure gradient was 56±19 mmHg. Regarding 123I-MIBG parameters, early heart-to-mediastinum (H/M) ratio was 3.1±0.5, delayed H/M ratio was 2.8±0.6, and the washout rate (WR) was 35%±13%. Multivariable linear regression analysis showed that coronary artery disease (β=-0.30, p=0.002) was an independent predictor of delayed H/M ratio, and that aortic valve area (β=-0.20, p=0.048) was an independent predictor of WR.

CONCLUSIONS

Our findings suggest that coronary artery disease is an independent predictor of delayed H/M ratio, and aortic valve area is an independent predictor of WR in patients with severe AS.

Aging is associated with cardiac autonomic nerve fiber depletion and reduced cardiac and circulating BDNF levels

BACKGROUND

Aging is a multifactorial process associated with an impairment of autonomic nervous system (ANS) function. Progressive ANS remodeling includes upregulation of expression of circulating catecholamines and depletion of cardiac autonomic nerve fibers, and it is responsible, in part, for the increased susceptibility to cardiac diseases observed in elderly subjects. Neurotrophic factors, such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), are involved in synaptogenesis and neurite outgrowth processes, supporting neuronal cell differentiation and maturation. However, whether and how these factors and their downstream signaling are involved in cardiac aging remains unclear. Here, we tested whether, in the aged heart, the overall extent of autonomic fibers is reduced, owing to lower production of trophic factors such as BDNF and NGF.

METHODS

In vivo, we used young (age: 3 months; n = 10) and old (age: 24 months; n = 11) male Fisher rats, whereas, we used human neuroblastoma (SH-SY5Y) cells in vitro.

RESULTS

Compared to the young rats, old rats displayed a marked reduction in the overall ANS fiber density, affecting both sympathetic and cholinergic compartments, as indicated by dopamine β-hydroxylase (dβh) and vesicular acetylcholine transporter (VaChT) immunohistochemical staining. In addition, a marked downregulation of GAP-43 and BDNF protein was observed in the left ventricular lysates of old rats compared to those of young rats. Interestingly, we did not find any significant difference in cardiac NGF levels between the young and old groups. To further explore the impact of aging on ANS fibers, we treated SH-SY5Y cells in vitro with serum obtained from young and old rats. Sera from both groups induced a remarkable increase in neuronal sprouting, as evidenced by a crystal violet assay. However, this effect was blunted in cells cultured with old rat serum and was accompanied by a marked reduction in GAP-43 and BDNF protein levels.

CONCLUSIONS

Our data indicate that physiological aging is associated with an impairment of ANS structure and function and that reduced BDNF levels are responsible, at least in part, for these phenomena.

The emerging role of the sympathetic nervous system in skeletal muscle motor innervation and sarcopenia

Examining neural etiologic factors'role in the decline of neuromuscular function with aging is essential to our understanding of the mechanisms underlying sarcopenia, the age-dependent decline in muscle mass, force and power. Innervation of the skeletal muscle by both motor and sympathetic axons has been established, igniting interest in determining how the sympathetic nervous system (SNS) affect skeletal muscle composition and function throughout the lifetime. Selective expression of the heart and neural crest derivative 2 gene in peripheral SNs increases muscle mass and force regulating skeletal muscle sympathetic and motor innervation; improving acetylcholine receptor stability and NMJ transmission; preventing inflammation and myofibrillar protein degradation; increasing autophagy; and probably enhancing protein synthesis. Elucidating the role of central SNs will help to define the coordinated response of the visceral and neuromuscular system to physiological and pathological challenges across ages. This review discusses the following questions: (1) Does the SNS regulate skeletal muscle motor innervation? (2) Does the SNS regulate presynaptic and postsynaptic neuromuscular junction (NMJ) structure and function? (3) Does sympathetic neuron (SN) regulation of NMJ transmission decline with aging? (4) Does maintenance of SNs attenuate aging sarcopenia? and (5) Do central SN group relays influence sympathetic and motor muscle innervation?

Impact of the number of comorbidities on cardiac sympathetic derangement in patients with reduced ejection fraction heart failure

INTRODUCTION

Heart failure (HF) is frequently associated with comorbidities. ¹²³I-metaiodobenzylguanidine (¹²³I-mIBG) imaging constitutes an effective tool to measure cardiac adrenergic innervation and to improve prognostic stratification in HF patients, including the risk of major arrhythmic events. Although comorbidities have been individually associated with reduced cardiac adrenergic innervation, thus suggesting increased arrhythmic risk, very comorbid HF patients seem to be less likely to experience fatal arrhythmias. We evaluated the impact of the number of comorbidities on cardiac adrenergic innervation, assessed through ¹²³I-mIBG imaging, in patients with systolic HF.

METHODS

Patients with systolic HF underwent clinical examination, transthoracic echocardiography and cardiac ¹²³I-mIBG scintigraphy. The presence of 7 comorbidities/conditions (smoking, chronic obstructive pulmonary disease, diabetes mellitus, peripheral artery disease, atrial fibrillation, chronic ischemic heart disease and chronic kidney disease) was documented in the overall study population.

RESULTS

The study population consisted of 269 HF patients with a mean age of 66±11 years, a left ventricular ejection fraction (LVEF) of 31±7%, and 153 (57%) patients presented ≥3 comorbidities. Highly comorbid patients presented a reduced late heart to mediastinum (H/M) ratio, while no significant differences emerged in terms of early H/M ratio and washout rate. Multiple regression analysis revealed that the number of comorbidities was not associated with mIBG parameters of cardiac denervation, which were correlated with age, body mass index and LVEF.

CONCLUSION

In systolic HF patients, the number of comorbidities is not associated with alterations in cardiac adrenergic innervation. These results are consistent with the observation that very comorbid HF patients suffer lower risk of sudden cardiac death.

Incremental prognostic value of myocardial neuroadrenergic damage in patients with chronic congestive heart failure: An iodine-123 meta-iodobenzylguanidine scintigraphy study

BACKGROUND

ICD in primary prevention reduced mortality in patients with heart failure (HF); however, in about 80% of the ICD recipients an event requiring a device intervention will never occur. Thus, a reliable screening test included in a multiparametric approach to appropriately select patients to ICD implantation is increasingly required. Aim of the work was to assess if the Iodine-123 Meta-Iodobenzylguanidine scintigraphy (123I-mIBG) could be useful to identify patients with HF who would not benefit from the ICD implantation because at low risk of arrhythmias.

METHODS AND RESULTS

This is a retrospective multicentre study on patients undergoing 123I-mIBG from February 2012 to December 2015. Inclusion criteria where: age ≥ 18 years old, LVEF ≤ 35% with idiopathic or ischemic heart disease, no previous malignant ventricular arrhythmias. Patients were divided in two groups based on of late H/M < or ≥ 1.60 on 123I-mIBG. Primary end-point was occurrence of malignant arrhythmias. Secondary end-point was occurrence of cardiac death and hospitalization for worsening HF. MACE were mortality and malignant arrhythmias. Eighty-one patients were enrolled (mean age: 69 years). On 123I-mIBG, 54 patients had late H/M < 1.6 and 27 patients had late H/M ≥ 1.60. After a mean follow-up of 13.3 (± 9.7) months, the primary end-point occurred in 13 patients out of 81. No arrhythmias occurred in patients with H/M late ≥ 1.6. Nineteen patients out of 20 with MACE showed an H/M late < 1.6. Death in group with H/M ≥ 1.6 occurred for worsening HF. A late H/M ≥ 1.60 showed a very high NPV for arrhythmia (100%) and for death (96.3%).

CONCLUSION

123I-mIBG imaging has the capability to identify patients at low risk of events.

Sympathetic nervous system activation and heart failure: Current state of evidence and the pathophysiology in the light of novel biomarkers

Heart failure (HF) is a complex clinical syndrome characterized by the activation of at least several neurohumoral pathways that have a common role in maintaining cardiac output and adequate perfusion pressure of target organs and tissues. The sympathetic nervous system (SNS) is upregulated in HF as evident in dysfunctional baroreceptor and chemoreceptor reflexes, circulating and neuronal catecholamine spillover, attenuated parasympathetic response, and augmented sympathetic outflow to the heart, kidneys and skeletal muscles. When these sympathoexcitatory effects on the cardiovascular system are sustained chronically they initiate the vicious circle of HF progression and become associated with cardiomyocyte apoptosis, maladaptive ventricular and vascular remodeling, arrhythmogenesis, and poor prognosis in patients with HF. These detrimental effects of SNS activity on outcomes in HF warrant adequate diagnostic and treatment modalities. Therefore, this review summarizes basic physiological concepts about the interaction of SNS with the cardiovascular system and highlights key pathophysiological mechanisms of SNS derangement in HF. Finally, special emphasis in this review is placed on the integrative and up-to-date overview of diagnostic modalities such as SNS imaging methods and novel laboratory biomarkers that could aid in the assessment of the degree of SNS activation and provide reliable prognostic information among patients with HF.

Impact of body mass index on cardiac adrenergic derangement in heart failure patients: a 123I-mIBG imaging study

PURPOSE

To assess the impact of body mass index (BMI) on cardiac adrenergic derangement, measured by iodine-123 meta-iodobenzylguanidine (¹²³I-mIBG) imaging in heart failure (HF) patients. Overweight and obesity represent relevant health issues, and augmented sympathetic tone has been described in patients with increased BMI. An extensive literature supports that HF-dependent cardiac denervation, measured through mIBG parameters, is an independent predictor of cardiovascular outcomes and mortality. However, the influence of BMI on cardiac mIBG uptake has not been largely investigated.

METHODS

We prospectively enrolled patients with systolic HF, collecting demographic, clinical, echocardiographic data, and mIBG imaging parameters. In order to detect the factors associated with mIBG parameters, a model building strategy, based on the Multivariable Fractional Polynomial algorithm, has been employed.

RESULTS

We studied 249 patients with systolic HF, mean age of 66.4 ± 10.6 years, and mean left ventricular ejection fraction (LVEF) of 30.7% ± 6.4, undergoing cardiac ¹²³I-mIBG imaging to assess HF severity and prognosis. Seventy-eight patients (31.3%) presented a BMI ≥ 30 kg/m² and obese patients showed a significant reduction in early heart to mediastinum (H/M) ratio (1.66 ± 0.19 vs. 1.75 ± 0.26; p = 0.008) and a trend to reduction in washout rate (33.6 ± 18.3 vs. 38.1 ± 20.1; p = 0.092) compared with patients with BMI < 30 kg/m². Multiple regression analysis revealed that BMI, age, and LVEF were significantly correlated with early and late H/M ratios.

CONCLUSIONS

Results of the present study indicate that BMI, together with LVEF and age, is independently correlated with cardiac mIBG uptake in HF patients.

Long-Term Caloric Restriction Improves Cardiac Function, Remodeling, Adrenergic Responsiveness, and Sympathetic Innervation in a Model of Postischemic Heart Failure

BACKGROUND

Caloric restriction (CR) has been described to have cardioprotective effects and improve functional outcomes in animal models and humans. Chronic ischemic heart failure (HF) is associated with reduced cardiac sympathetic innervation, dysfunctional β-adrenergic receptor signaling, and decreased cardiac inotropic reserve. We tested the effects of a long-term CR diet, started late after myocardial infarction on cardiac function, sympathetic innervation, and β-adrenergic receptor responsiveness in a rat model of postischemic HF.

METHODS AND RESULTS

Adult male rats were randomly assigned to myocardial infarction or sham operation and 4 weeks later were further randomized to a 1-year CR or normal diet. One year of CR resulted in a significant reduction in body weight, heart weight, and heart weight/tibia length ratio when compared with normal diet in HF groups. At the end of the study period, echocardiography and histology revealed that HF animals under the CR diet had ameliorated left ventricular remodeling compared with HF rats fed with normal diet. Invasive hemodynamic showed a significant improvement of cardiac inotropic reserve in CR HF rats compared with HF-normal diet animals. Importantly, CR dietary regimen was associated with a significant increase of cardiac sympathetic innervation and with normalized cardiac β-adrenergic receptor levels in HF rats when compared with HF rats on the standard diet.

CONCLUSIONS

We demonstrate, for the first time, that chronic CR, when started after HF established, can ameliorate cardiac dysfunction and improve inotropic reserve. At the molecular level, we find that chronic CR diet significantly improves sympathetic cardiac innervation and β-adrenergic receptor levels in failing myocardium.

Behind Traditional Semi-quantitative Scores of Myocardial Perfusion Imaging: An Eye on Niche Parameters

The evaluation of stress-induced myocardial perfusion defects by non-invasive myocardial perfusion imaging (MPI) modalities has a leading role in the identification of coronary artery disease, and has excellent diagnostic and prognostic value. Non-invasive MPI can be performed using conventional and novel gamma cameras or by PET/CT. New software has allowed novel parameters that may have a role in the identification of early marks of cardiac impairment to be evaluated. We aim to give an overview of niche parameters obtainable by single photon emission CT (SPECT) and PET/CT MPI that may help practitioners to detect initial signs of cardiac damage and identify new therapy targets. In particular, we summarise the role of left ventricular geometry indices for remodelling, phase analysis parameters to evaluate mechanical dyssynchrony, the concept of relative flow reserve in the evaluation of flow-limiting epicardial stenosis, vascular age and epicardial adipose tissue as early markers of atherosclerotic burden, and emerging parameters for the evaluation of myocardial innervation, such as the total defect score.

Cardiac sympathetic innervation scintigraphy with 123I-meta-iodobenzylguanidine. Basis, protocols and clinical applications in Cardiology

Imaging of cardiac sympathetic innervation is only possible by nuclear cardiology techniques and its assessment is key in the evaluation of and decision-making for patients with cardiac sympathetic impairment. This review includes the basis of cardiac sympathetic scintigraphy with ¹²³I-meta-iodobenzylguanidine (¹²³I-MIBG), recommended protocols, patient preparation, image acquisition and quantification, reproducibility, dosimetry, etc., and also the clinical indications for cardiac patients, mainly with regard to heart failure, arrhythmia, coronary artery disease, cardiotoxicity, including its contribution to establishing the indication for and monitoring the response to implantable cardiac devices, pharmacological treatment, heart transplantation and other.

Sympathetic nervous system in age-related cardiovascular dysfunction: Pathophysiology and therapeutic perspective

Cardiovascular diseases such as heart failure and metabolic syndrome have high prevalence in the elderly population and are leading causes of death, disability, hospitalization, driving high healthcare costs worldwide. To reduce this social and economic burden there is urgency to find effective therapeutic targets. Several studies have linked the dysfunction of the Sympathetic Nervous System and β-adrenergic receptor signaling with the pathogenesis of age-related cardiovascular diseases. Therapeutic treatments that restore their functions have been shown to be effective in subjects with cardiovascular comorbidities. In fact, lifestyle interventions (such as exercise training and diet) as well as pharmacologic treatments (e.g. β-blockers or moxonidine) and mini-invasive interventions (renal sympathetic denervation) have beneficial effects on age-related cardiovascular diseases. In the current "Medicine in focus" article we will discuss the pathogenic role of the Sympathetic Nervous System in age-related cardiovascular diseases as well as current and new therapeutic approaches.

Heart rate variability in middle-aged sprint and endurance athletes

BACKGROUND

Aging is associated with decreased autonomic balance which could be assessed by Heart Rate Variability (HRV). Exercise training improves autonomic balance, but there is a lack in the literature regarding the heart rate variability (HRV) of master sprinters and endurance athletes.

PURPOSE

The effects of lifelong endurance and sprint training on cardiac autonomic balance were assessed in master athletes and compared with age-matched controls and young untrained controls.

METHODS

Participants (n = 81) were 8 master sprinters (MS; 51.8 ± 11.1 yrs), 8 master endurance athletes (EN, n = 8, 53.6 ± 8.6 yrs), 17 age-matched untrained (CON, 47.47 ± 6.00 yrs) and 48 young controls (YC, 25.40 ± 3.87 yrs). For the acquisition of RR intervals (iRR) (Polar RS800X Heart Rate Monitor®) the participants remained seated for 15-min with the final 10-min being considered for analysis. HRV was measured using Kubios software. A one-way ANOVA with repeated measures was applied.

RESULTS

All studied parameters did not differ between MS and EN {Time Domain [HR (bpm) 59.00 ± 6.13 vs. 58.94 ± 12.75], [R-R (ms) 1030.45 ± 107.45 vs. 1068.77 ± 206.17], [SDNN (ms) 57.35 ± 20.07 vs. 80.66 ± 71.07], [RMSSD (ms) 40.88 ± 20.07 vs. 38.93 ± 20.44]; Non-linear domain [SD1 (ms) 28.93 ± 14.20 vs. 27.56 ± 14.46]}, whose demonstrated a reduced HR and elevated mean R-R intervals in comparison to both YC {[HR (bpm) 69.64 ± 9.81]; [R-R (ms) 883.93 ± 124.11]} and age-matched controls {[HR (bpm) 70.06 ± 6.63]; [R-R (ms) 865.11 ± 78.39]}. It was observed a lower HRV for middle-aged CON {[RMSSD (ms) 20.23 ± 5.87], [SDNN (ms) 37.79 ± 10.15] and [SD1 (ms) 14.31 ± 4.15]} compared to YC {[RMSSD (ms) 43.33 ± 26.41], [SDNN (ms) 67.07 ± 28.77] and [SD1 (ms) 30.66 ± 18.69; p < .05]}. These last age-related differences were not observed for MS and EN.

CONCLUSION

For master athletes, regardless of whether they are trained in endurance or sprinters, both training modes revealed to be equally beneficial in attenuating the effects of aging on the autonomic balance.

New Insights in Cardiac β-Adrenergic Signaling During Heart Failure and Aging

Heart failure (HF) has become increasingly common within the elderly population, decreasing their survival and overall quality of life. In fact, despite the improvements in treatment, many elderly people suffer from cardiac dysfunction (HF, valvular diseases, arrhythmias or hypertension-induced cardiac hypertrophy) that are much more common in an older fragile heart. Since β-adrenergic receptor (β-AR) signaling is abnormal in failing as well as aged hearts, this pathway is an effective diagnostic and therapeutic target. Both HF and aging are characterized by activation/hyperactivity of various neurohormonal pathways, the most important of which is the sympathetic nervous system (SNS). SNS hyperactivity is initially a compensatory mechanism to stimulate contractility and maintain cardiac output. Unfortunately, this chronic stimulation becomes detrimental and causes decreased cardiac function as well as reduced inotropic reserve due to a decrease in cardiac β-ARs responsiveness. Therapies which (e.g., β-blockers and physical activity) restore β-ARs responsiveness can ameliorate cardiac performance and outcomes during HF, particularly in older patients. In this review, we will discuss physiological β-adrenergic signaling and its alterations in both HF and aging as well as the potential clinical application of targeting β-adrenergic signaling in these disease processes.

New Insights in Cardiac β-Adrenergic Signaling During Heart Failure and Aging

Heart failure (HF) has become increasingly common within the elderly population, decreasing their survival and overall quality of life. In fact, despite the improvements in treatment, many elderly people suffer from cardiac dysfunction (HF, valvular diseases, arrhythmias or hypertension-induced cardiac hypertrophy) that are much more common in an older fragile heart. Since β-adrenergic receptor (β-AR) signaling is abnormal in failing as well as aged hearts, this pathway is an effective diagnostic and therapeutic target. Both HF and aging are characterized by activation/hyperactivity of various neurohormonal pathways, the most important of which is the sympathetic nervous system (SNS). SNS hyperactivity is initially a compensatory mechanism to stimulate contractility and maintain cardiac output. Unfortunately, this chronic stimulation becomes detrimental and causes decreased cardiac function as well as reduced inotropic reserve due to a decrease in cardiac β-ARs responsiveness. Therapies which (e.g., β-blockers and physical activity) restore β-ARs responsiveness can ameliorate cardiac performance and outcomes during HF, particularly in older patients. In this review, we will discuss physiological β-adrenergic signaling and its alterations in both HF and aging as well as the potential clinical application of targeting β-adrenergic signaling in these disease processes.

The Impact of Ageing on 11C-Hydroxyephedrine Uptake in the Rat Heart

We aimed to explore the impact of ageing on 11C-hydroxyephedrine (11C-HED) uptake in the healthy rat heart in a longitudinal setting. To investigate a potential cold mass effect, the influence of specific activity on cardiac 11C-HED uptake was evaluated: 11C-HED was synthesized by N-methylation of (−)-metaraminol as the free base (radiochemical purity >95%) and a wide range of specific activities (0.2–141.9 GBq/μmol) were prepared. ¹¹C-HED (48.7 ± 9.7MBq, ranged 0.2–60.4 μg/kg cold mass) was injected in healthy Wistar Rats. Dynamic 23-frame PET images were obtained over 30 min. Time activity curves were generated for the blood input function and myocardial tissue. Cardiac 11C-HED retention index (%/min) was calculated as myocardial tissue activity at 20–30 min divided by the integral of the blood activity curves. Additionally, the impact of ageing on myocardial 11C-HED uptake was investigated longitudinally by PET studies at different ages of healthy Wistar Rats. A dose-dependent reduction of cardiac 11C-HED uptake was observed: The estimated retention index as a marker of norepinephrine function decreased at a lower specific activity (higher amount of cold mass). This observed high affinity of 11C-HED to the neural norepinephrine transporter triggered a subsequent study: In a longitudinal setting, the 11C-HED retention index decreased with increasing age. An age-related decline of cardiac sympathetic innervation could be demonstrated. The herein observed cold mass effect might increase in succeeding scans and therefore, 11C-HED microPET studies should be planned with extreme caution if one single radiosynthesis is scheduled for multiple animals.

Is 123I-metaiodobenzylguanidine heart-to-mediastinum ratio dependent on age? From Japanese Society of Nuclear Medicine normal database

BACKGROUND

Heart-to-mediastinum ratios (HMRs) of 123I-metaiodobenzylguanidine (MIBG) have usually been applied to prognostic evaluations of heart failure and Lewy body disease. However, whether these ratios depend on patient age has not yet been clarified using normal databases.

METHODS

We analyzed 62 patients (average age 57 ± 19 years, male 45%) derived from a normal database of the Japanese Society of Nuclear Medicine working group. The HMR was calculated from early (15 min) and delayed (3-4 h) anterior planar 123I-MIBG images. All HMRs were standardized to medium-energy general purpose (MEGP) collimator equivalent conditions using conversion coefficients for the collimator types. Washout rates (WR) were also calculated, and we analyzed whether early and late HMR, and WR are associated with age.

RESULTS

Before standardization of HMR to MEGP collimator conditions, HMR and age did not significantly correlate. However, late HMR significantly correlated with age after standardization: late HMR = - 0.0071 × age + 3.69 (r2 = 0.078, p = 0.028), indicating that a 14-year increase in age corresponded to a decrease in HMR of 0.1. Whereas the lower limit (2.5% quantile) of late HMR was 2.3 for all patients, it was 2.5 and 2.0 for those aged ≤ 63 and > 63 years, respectively. Early HMR tended to be lower in subjects with the higher age (p = 0.076), whereas WR was not affected by age.

CONCLUSION

While late HMR was slightly decreased in elderly patients, the lower limit of 2.2-2.3 can still be used to determine both early and late HMR.

A noradrenergic lesion aggravates the effects of systemic inflammation on the hippocampus of aged rats

Neuroinflammation is potentiated by early degeneration of the locus coeruleus noradrenergic pathway (LC-NE) commonly seen in aging-related neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. In animal models, lipopolysaccharide (LPS) induces strong peripheral immune responses that can cause cognitive changes secondary to neuroinflammation. The influence of the peripheral immune response on cognition might be exacerbated by LC-NE degeneration, but this has not been well characterized previously. In this study, we investigated how systemic inflammation affects neuroinflammation and cognition in aged rats that have had either normal or damaged LC-NE transmitter systems. Rats were first exposed to the selective noradrenergic (NE) neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4) to induce degeneration of central NE pathways. Two weeks later, the rats received a low dose of LPS. This resulted in 3 treatment groups (Control, LPS-, and DSP4+LPS-treated rats) studied at 4 hours (short-term subgroup) and 7 days (long-term subgroup) following the LPS injection. DSP4+LPS-treated rats exhibited increased serum levels of several pro-inflammatory cytokines, increased astroglial and microglial activation in the hippocampus, and poorer performance in the novel object recognition task (NORT) compared to controls and LPS-treated rats. Additionally, serum and brain tissue levels of brain-derived neurotrophic factor (BDNF) were modulated over time in the DSP4+LPS group compared to the other two groups. Specifically, DSP4+LPS-treated rats in the short-term subgroup had lower hippocampal BDNF levels (~25%) than controls and LPS-treated rats, which negatively correlated with hippocampal astrogliosis and positively correlated with hippocampal IL-1β levels. Serum and hippocampal BDNF levels in the DSP4+LPS-treated rats in the long-term subgroup returned to levels similar to the control group. These results show that systemic inflammation in LC-NE-lesioned aged rats promotes an exacerbated systemic and central inflammatory response compared to LC-NE-intact rats and alters BDNF levels, indicating the important role of this neurotransmitter system in response to neuroinflammation.

microRNA in Cardiovascular Aging and Age-Related Cardiovascular Diseases

Over the last decades, life expectancy has significantly increased although several chronic diseases persist in the population, with aging as the leading risk factor. Despite improvements in diagnosis and treatment, many elderlies suffer from cardiovascular problems that are much more frequent in an older, more fragile organism. In the long term, age-related cardiovascular diseases (CVDs) contribute to the decline of quality of life and ability to perform normal activities of daily living. microRNAs (miRNAs) are a class of small non-coding RNAs that regulate gene expression at the posttranscriptional level in both physiological and pathological conditions. In this review, we will focus on the role of miRNAs in aging and age-related CVDs as heart failure, hypertension, atherosclerosis, atrial fibrillation, and diabetes mellitus. miRNAs are key regulators of complex biological mechanisms, representing an exciting potential therapeutic target in CVDs. Moreover, one major challenge in geriatric medicine is to find reliable biomarkers for diagnosis, prognosis, and prediction of the response to specific drugs. miRNAs represent a very promising tool due to their stability in the circulation and unique signature in CVDs. However, further studies are needed to investigate their translational potential in the real clinical practice.

The natural history of takotsubo syndrome: a two-year follow-up study with myocardial sympathetic and perfusion G-SPECT imaging

PURPOSE

To investigate changes in sympathetic activity, perfusion, and left ventricular (LV) functionality in takotsubo cardiomyopathy (TTC) patients from onset (T₀) to post-onset conditions at 1 month (T₁), 1-2 years (T₂, T₃).

METHODS

Twenty-two patients (70 ± 11 years) underwent serial gated single photon emission tomography (G-SPECT) studies with ¹²³I-mIBG and ^99mTc-Sestamibi. Statistics were performed using ANOVA/Sheffé post-hoc, correlation test, and receiver operating characteristic (ROC) curve analysis (p < 0.05).

RESULTS

Patients presented at T₀ with LV ballooning and reduced early-late mIBG uptake (95%, 100%), left ventricular ejection fraction (LVEF)_G-SPECT (86%) and perfusion (77 %). Adrenergic dysfunction was greater in apex, it overlaps with contractile impairment, and both were more severe than perfusion defect. During follow-up, LVEF_G-SPECT, contractility, and perfusion were normal, while 82% and 90% of patients at T₁ and 50% at T₂ and T₃ continued to show a reduced apical early-late mIBG distribution. These patients presented at T₀-T₁ with greater impairment of adrenergic function, contractility, and perfusion. A relationship was present within innervation and both perfusion and contractile parameters at T₀ and T₁, and between the extent of adrenergic defect at T₃ and both the defect extent and age at T₀ (cut-off point 42.5%, 72 years).

CONCLUSION

Outcome for TTC is not limited to a reversible contractile and perfusion abnormalities, but it includes residual adrenergic dysfunction, depending on the level of adrenergic impairment and age of patients at onset. The number of patients, as well as degree of perfusion abnormalities were found to be higher than those previously reported possibly depending on the time-interval between hospital admission and perfusion scan.