Acute Modulation of Left Ventricular Control by Selective Intracardiac Sympathetic Denervation.

BACKGROUND: The sympathetic nervous system plays an integral role in cardiac physiology. Nerve fibers innervating the left ventricle are amenable to transvenous catheter stimulation along the coronary sinus (CS). OBJECTIVES: The aim of the present study was to modulate left ventricular control by selective intracardiac sympathetic denervation. METHODS: First, the impact of epicardial CS ablation on cardiac electrophysiology was studied in a Langendorff model of decentralized murine hearts (n = 10 each, ablation and control groups). Second, the impact of transvenous, anatomically driven axotomy by catheter-based radiofrequency ablation via the CS was evaluated in healthy sheep (n = 8) before and during stellate ganglion stimulation. RESULTS: CS ablation prolonged epicardial ventricular refractory period without (41.8 ± 8.4 ms vs 53.0 ± 13.5 ms; P = 0.049) and with ß1-2-adrenergic receptor blockade (47.8 ± 7.8 ms vs 73.1 ± 13.2 ms; P < 0.001) in mice. Supported by neuromorphological studies illustrating a circumferential CS neural network, intracardiac axotomy by catheter ablation via the CS in healthy sheep diminished the blood pressure increase during stellate ganglion stimulation (Δ systolic blood pressure 21.9 ± 10.9 mm Hg vs 10.5 ± 12.0 mm Hg; P = 0.023; Δ diastolic blood pressure 9.0 ± 5.5 mm Hg vs 3.0 ± 3.5 mm Hg; P = 0.039). CONCLUSIONS: Transvenous, anatomically driven axotomy targeting nerve fibers along the CS enables acute modulation of left ventricular control by selective intracardiac sympathetic denervation.

Catecholaminergic axon innervation and morphology in flat-mounts of atria and ventricles of mice.

Sympathetic efferent axons regulate cardiac functions. However, the topographical distribution and morphology of cardiac sympathetic efferent axons remain insufficiently characterized due to the technical challenges involved in immunohistochemical labeling of the thick walls of the whole heart. In this study, flat-mounts of the left and right atria and ventricles of FVB mice were immunolabeled for tyrosine hydroxylase (TH), a marker of sympathetic nerves. Atrial and ventricular flat-mounts were scanned using a confocal microscope to construct montages. We found (1) In the atria: A few large TH-immunoreactive (IR) axon bundles entered both atria, branched into small bundles and then single axons that eventually formed very dense terminal networks in the epicardium, myocardium and inlet regions of great vessels to the atria. Varicose TH-IR axons formed close contact with cardiomyocytes, vessels, and adipocytes. Multiple intrinsic cardiac ganglia (ICG) were identified in the epicardium of both atria, and a subpopulation of the neurons in the ICG were TH-IR. Most TH-IR axons in bundles traveled through ICG before forming dense varicose terminal networks in cardiomyocytes. We did not observe varicose TH-IR terminals encircling ICG neurons. (2) In the left and right ventricles and interventricular septum: TH-IR axons formed dense terminal networks in the epicardium, myocardium, and vasculature. Collectively, TH labeling is achievable in flat-mounts of thick cardiac walls, enabling detailed mapping of catecholaminergic axons and terminal structures in the whole heart at single-cell/axon/varicosity scale. This approach provides a foundation for future quantification of the topographical organization of the cardiac sympathetic innervation in different pathological conditions.

Comparative gross anatomy of epicardiac ganglionated nerve plexi on the human and sheep cardiac ventricles.

This study aimed to examine the distribution and quantitative parameters of the epicardiac ventricular neural ganglionated plexus in the hearts of humans and sheep, highlighting the differences of this plexus in humans and large models. Five non-sectioned pressure distended whole hearts of the human newborns and 10 hearts of newborn German black-faced lambs were investigated applying a histochemical method for acetylcholinesterase to stain epicardiac neural structures with their subsequent stereomicroscopic examination. In humans, the ventricular nerves are spread by four epicardiac nerve subplexuses, that is, the left and right coronary as well as the left and middle dorsal. In sheep, the ventricular nerves are spread by five epicardiac nerve subplexuses, that is, the left and right coronary, the left and middle dorsal and the right ventral ones. The ventricular epicardium involved up to 129 ganglia in humans and up to 198-in sheep. The largest number of the ventricular ganglionic cells in humans were located on the ventral side, in front of the conus arteriosus, while on sheep ventricles, the most numerous neurons distributed on the dorsal wall of the left ventricle. This comparative study of the morphological patterns of the human and sheep ventricles demonstrates that the sheep heart is neuroanatomically distinct from the human one and this must be taking into consideration using the sheep model for the heart physiology experiments.

Anti-arrhythmic and anti-heart failure effects of low-level electrical stimulation on aortic root ventricular ganglionated plexi.

BACKGROUND: It remains uncertain whether low-level electrical stimulation (LL-ES) of the ventricular ganglionated plexi (GP) improves heart function. This study investigated the anti-arrhythmic and anti-heart failure effects of LL-ES of the aortic root ventricular GP (ARVGP). METHODS: Thirty dogs were divided randomly into control, drug, and LL-ES groups after performing rapid right ventricular pacing to establish a heart failure (HF) model. The inducing rate of arrhythmia; levels of bioactive factors influencing HF, including angiotensin II type I receptor (AT-1R), transforming growth factor-beta (TGF-ß), matrix metalloproteinase (MMP), and phosphorylated extracellular signal-regulated kinase (p-ERK1/2); left ventricular stroke volume (LVSV), and left ventricular ejection fraction (LVEF)were measured after treatment with placebo, drugs, and LL-ES. RESULTS: The inducing rate of atrial arrhythmia decreased from 60% in the control group to 50% in the drug group and 10% in the LL-ES group (p = .033 vs. drug group) after 1 week of treatment. The ventricular effective refractory period was prolonged from 139 ± 8 ms in the drug group to 166 ± 13 ms in the LL-ES group (p = .001). Compared to the drug group, the expressions of AT-1R, TGF-ß, and MMP proteins were down-regulated in the LL-ES group, whereas that of p-ERK1/2 was significantly increased (all p = .001). Moreover, in the LL-ES group, LVSV increased markedly from 13.16 ± 0.22 to 16.86 ± 0.27 mL, relative to that in the drug group (p = .001), and LVEF increased significantly from 38.48% ± 0.53% to 48.94% ± 0.57% during the same time frame (p = .001). CONCLUSION: Short-term LL-ES of ARVGP had both anti-arrhythmic and anti-inflammatory effects and contributed to the treatment of tachycardia-induced HF and its associated arrhythmia.

Left Stellate Ganglion Ablation Inhibits Ventricular Arrhythmias through Macrophage Regulation in Canines with Acute Ischemic Stroke.

AIMS: To investigate the potential mechanism of ventricular arrhythmias (VAs) after acute ischemic stroke and explore the effects of left stellate gangling (LSG) ablation on VAs induced by stroke in canines. Materials and Methods: Twenty canines were randomly divided into the sham-operated group (n=6), AS group (n=7) and SGA group (n=7). Cerebral ischemic model was established in the AS group and the SGA group by right acute middle cerebral artery occlusion (MCAO). LSG ablation was performed in the SGA group as soon as MCAO. After 3 days, atrial electrophysiology and neural activity were measured in vivo. The levels of norepinephrine (NE) in plasma and ventricle were detected by ELISA. The levels of monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-α (TNF-α) and NF-κB p65 in ventricle were detected by western blotting. The pro-inflammatory polarization of macrophages in ventricle was detected by immunofluorescence. Results: Higher ventricular tachycardia (VT) inducibility and lower ventricular fibrillation threshold (VFT) were observed in the AS group compared with those in the sham-operated group, associated with higher LSG activity and NE levels, increased number of M1 macrophages and secretion of inflammatory cytokines in ventricle (all P<0.001). Compared with the AS group, the SGA group had lower VT inducibility and higher VFT, combined with lower NE levels, and reduced number of M1 macrophages and secretion of inflammatory cytokines in ventricle (all P<0.001). Conclusion: LSG ablation could reduce VAs vulnerability after acute stroke by preventing the macrophages polarization and activation induced by sympathetic hyperactivity.

Focal reduction in left ventricular 123I-metaiodobenzylguanidine uptake and impairment in systolic function in patients with Anderson-Fabry disease.

BACKGROUND: Abnormalities of cardiac sympathetic innervation have been demonstrated in Anderson-Fabry disease (AFD). We aimed to investigate the relationship between regional left ventricular (LV) denervation and regional function abnormalities. METHODS: Twenty-four AFD patients (43.7 ± 12.8 years) were studied by 123I-metaiodobenzylguanidine (MIBG) cardiac imaging and speckle-tracking echocardiography. Segmental tracer uptake was estimated according to 0 to 4 score, and total defect score (TDS) was calculated for each patient. RESULTS: Segmental longitudinal strain worsened as MIBG uptake score increased (P < 0.001). By ROC analysis, a segmental longitudinal strain > - 16.2% predicted a segmental MIBG uptake score ≥1, with 79.7% sensitivity and 65.3% specificity. Segmental MIBG uptake defects were found in 13 out 24 AFD patients. LV mass index (60.8 ± 10.1 vs. 41.4 ± 9.8 g/h2.7), relative wall thickness (0.51 ± 0.06 vs. 0.40 ± 0.06), systolic pulmonary artery pressure (35.2 ± 6.7 vs. 27.2 ± 4.2 mmHg), and longitudinal strain (- 14.3 ± 2.7 vs. -19.4 ± 1.8%) were significantly higher in patients with segmental defect (all P < 0.01). At multivariate linear regression analysis, global longitudinal strain was independently associated with TDS (B = 3.007, 95% confidence interval 1.384 to 4.630, P = 0.001). CONCLUSIONS: Reduced cardiac MIBG uptake reflects the severity of cardiac involvement in AFD patients. LV longitudinal function impairment seems to be an earlier disease feature than regional myocardial denervation.

Different effects of amiodarone and dofetilide on the dispersion of repolarization between well-coupled ventricular and Purkinje fibers1.

Increased transmural dispersion of repolarization is an established contributing factor to ventricular tachyarrhythmias. In this study, we evaluated the effect of chronic amiodarone treatment and acute administration of dofetilide in canine cardiac preparations containing electrotonically coupled Purkinje fibers (PFs) and ventricular muscle (VM) and compared the effects to those in uncoupled PF and VM preparations using the conventional microelectrode technique. Dispersion between PFs and VM was inferred from the difference in the respective action potential durations (APDs). In coupled preparations, amiodarone decreased the difference in APDs between PFs and VM, thus decreasing dispersion. In the same preparations, dofetilide increased the dispersion by causing a more pronounced prolongation in PFs. This prolongation was even more emphasized in uncoupled PF preparations, while the effect in VM was the same. In uncoupled preparations, amiodarone elicited no change on the difference in APDs. In conclusion, amiodarone decreased the dispersion between PFs and VM, while dofetilide increased it. The measured difference in APD between cardiac regions may be the affected by electrotonic coupling; thus, studying PFs and VM separately may lead to an over- or underestimation of dispersion.

Predictors of ventricular ablation's success: Viability, innervation, or mismatch?

AIMS: Sympathetic dys-innervation may play an important role in the development of post-ischemic ventricular arrhythmias (VA). Aim of this study was to prove that perfusion/innervation mismatch (PIM) evaluated by SPECT can identify areas of local abnormal ventricular activities (LAVA) on electroanatomic mapping (EAM). METHODS: Sixteen patients referred to post-ischemic VA catheter ablation underwent pre-procedural and 1-month post-ablation 123I-MIBG/99mTc-tetrofosmin rest SPECT myocardial imaging. PIM was defined according to the segmental distributions of 99mTc-tetrofosmin and 123I-MIBG. A 17-segment LV analysis was used for either SPECT or LV EAM voltage map. All patients were followed up clinically for at least 1 year. RESULTS: Before ablation, the mean voltage in the PIM segments was higher than in the scarred ones but lower than in the normal regions. The presence of PIM in a specific LV zone was an independent predictor of LAVA. After ablation, PIM value was significantly reduced, mainly due to an increase in perfusion summed rest score, in particular in patients that were responders to ablation. CONCLUSIONS: PIM may associate with VA substrate expressed by LAVA and might provide a novel guide for substrate ablation. A significant reduction of PIM could predict a positive clinical response to ablation.

Cells of the adult human heart.

Cardiovascular disease is the leading cause of death worldwide. Advanced insights into disease mechanisms and therapeutic strategies require a deeper understanding of the molecular processes involved in the healthy heart. Knowledge of the full repertoire of cardiac cells and their gene expression profiles is a fundamental first step in this endeavour. Here, using state-of-the-art analyses of large-scale single-cell and single-nucleus transcriptomes, we characterize six anatomical adult heart regions. Our results highlight the cellular heterogeneity of cardiomyocytes, pericytes and fibroblasts, and reveal distinct atrial and ventricular subsets of cells with diverse developmental origins and specialized properties. We define the complexity of the cardiac vasculature and its changes along the arterio-venous axis. In the immune compartment, we identify cardiac-resident macrophages with inflammatory and protective transcriptional signatures. Furthermore, analyses of cell-to-cell interactions highlight different networks of macrophages, fibroblasts and cardiomyocytes between atria and ventricles that are distinct from those of skeletal muscle. Our human cardiac cell atlas improves our understanding of the human heart and provides a valuable reference for future studies.

Increased arrhythmia susceptibility in type 2 diabetic mice related to dysregulation of ventricular sympathetic innervation.

Patients with type 2 diabetes mellitus (T2DM) have a greater risk of developing life-threatening cardiac arrhythmias. Because the underlying mechanisms and potential influence of diabetic autonomic neuropathy are not well understood, we aimed to assess the relevance of a dysregulation in cardiac autonomic tone. Ventricular arrhythmia susceptibility was increased in Langendorff-perfused hearts isolated from mice with T2DM (db/db). Membrane properties and synaptic transmission were similar at cardiac postganglionic parasympathetic neurons from diabetic and control mice; however, a greater asynchronous neurotransmitter release was present at sympathetic postganglionic neurons from the stellate ganglia of db/db mice. Western blot analysis showed a reduction of tyrosine hydroxylase (TH) from the ventricles of db/db mice, which was confirmed with confocal imaging as a heterogeneous loss of TH-immunoreactivity from the left ventricular wall but not the apex. In vivo stimulation of cardiac parasympathetic (vagus) or cardiac sympathetic (stellate ganglion) nerves induced similar changes in heart rate in control and db/db mice, and the kinetics of pacing-induced Ca2+ transients (recorded from isolated cardiomyocytes) were similar in control and db/db cells. Antagonism of cardiac muscarinic receptors did not affect the frequency or severity of arrhythmias in db/db mice, but sympathetic blockade with propranolol completely inhibited arrhythmogenicity. Collectively, these findings suggest that the increased ventricular arrhythmia susceptibility of type 2 diabetic mouse hearts is due to dysregulation of the sympathetic ventricular control.NEW & NOTEWORTHY Patients with type 2 diabetes mellitus have greater risk of suffering from sudden cardiac death. We found that the increased ventricular arrhythmia susceptibility in type 2 diabetic mouse hearts is due to cardiac sympathetic dysfunction. Sympathetic dysregulation is indicated by an increased asynchronous release at stellate ganglia, a heterogeneous loss of tyrosine hydroxylase from the ventricular wall but not apex, and inhibition of ventricular arrhythmias in db/db mice after ß-sympathetic blockade.

Thoracic spinal cord neuromodulation obtunds dorsal root ganglion afferent neuronal transduction of the ischemic ventricle.

Aberrant afferent signaling drives adverse remodeling of the cardiac nervous system in ischemic heart disease. The study objective was to determine whether thoracic spinal dorsal column stimulation (SCS) modulates cardiac afferent sensory transduction of the ischemic ventricle. In anesthetized canines (n = 16), extracellular activity generated by 62 dorsal root ganglia (DRG) soma (T1-T3), with verified myocardial ischemic (MI) sensitivity, were evaluated with and without 20-min preemptive SCS (T1-T3 spinal level; 50 Hz, 90% motor threshold). Transient MI was induced by 1-min coronary artery occlusion (CAO) of the left anterior descending (LAD) or circumflex (LCX) artery, randomized as to sequence. LAD and LCX CAO activated cardiac-related DRG neurons (LAD: 0.15 ± 0.04-1.05 ± 0.20 Hz, P < 0.00002; LCX: 0.08 ± 0.02-1.90 ± 0.45 Hz, P < 0.0003). SCS decreased basal neuronal activity of neurons that responded to LAD (0.15 ± 0.04 to 0.02 ± 0.01 Hz, P < 0.006) and LCX (0.08 ± 0.02 to 0.02 ± 0.01 Hz, P < 0.003). SCS suppressed responsiveness to transient MI (LAD: 1.05 ± 0.20-0.03 ± 0.01 Hz; P < 0.0001; LCX: 1.90 ± 0.45-0.03 ± 0.01 Hz; P < 0.001). Suprathreshold SCS (1 Hz) did not activate DRG neurons antidromically (n = 10 animals). Ventricular fibrillation (VF) was associated with a rapid increase in DRG activity to a maximum of 4.39 ± 1.07 Hz at 20 s after VF induction and a return to 90% of baseline within 10 s thereafter. SCS obtunds the capacity of DRG ventricular neurites to transduce the ischemic myocardium to second-order spinal neurons, a mechanism that would blunt reflex sympathoexcitation to myocardial ischemic stress, thereby contributing to its capacity to cardioprotect.NEW & NOTEWORTHY Aberrant afferent signaling drives adverse remodeling of the cardiac nervous system in ischemic heart disease. This study determined that thoracic spinal column stimulation (SCS) obtunds the capacity of dorsal root ganglia ventricular afferent neurons to transduce the ischemic myocardium to second-order spinal neurons, a mechanism that would blunt reflex sympathoexcitation to myocardial ischemic stress. This modulation does not reflect antidromic actions of SCS but likely reflects efferent-mediated changes at the myocyte-sensory neurite interface.

Neuromodulation Approaches for Cardiac Arrhythmias: Recent Advances.

PURPOSE OF REVIEW: This review aims to describe the latest advances in autonomic neuromodulation approaches to treating cardiac arrhythmias, with a focus on ventricular arrhythmias. RECENT FINDINGS: The increasing understanding of neuronal remodeling in cardiac diseases has led to the development and improvement of novel neuromodulation therapies targeting multiple levels of the autonomic nervous system. Thoracic epidural anesthesia, spinal cord stimulation, stellate ganglion modulatory therapies, vagal stimulation, renal denervation, and interventions on the intracardiac nervous system have all been studied in preclinical models, with encouraging preliminary clinical data. The autonomic nervous system regulates all the electrical processes of the heart and plays an important role in the pathophysiology of cardiac arrhythmias. Despite recent advances in the clinical application of cardiac neuromodulation, our comprehension of the anatomy and function of the cardiac autonomic nervous system is still limited. Hopefully in the near future, more preclinical data combined with larger clinical trials will lead to further improvements in neuromodulatory treatment for heart rhythm disorders.

Effect of sympathetic autonomic stress from the cold pressor test on left ventricular function in young healthy adults.

There is a dearth of studies investigating the effect of sympathetic activation on left ventricular function. This study aimed to investigate the effect of sympathetic autonomic stress on left ventricular function in young healthy adults. Fifty-six normotensive healthy participants (age 23.55 ± 3.82 years) took part in the study after giving informed consent. After obtaining baseline measurements, heart rate (HR), blood pressure (BP), peripheral saturation of oxygen (SpO2) and left ventricular function (assessed by means of ejection fraction (EF) obtained by transthoracic 2-D echocardiography) were determined before and following sympathetic activation using cold pressor test (CPT). Exposure to CPT led to significant increase (P < 0.0001) in HR (70.4 ± 10.7 bpm to 91.6 ± 14.8 bpm), SBP (118 ± 8 mmHg to 138 ± 14 mmHg) and DBP (71 ± 7 mmHg to 91 ± 11 mmHg). Participants' EDV (101.1 ± 15.8 ml to 104.2 ± 19.3 mL), ESV (38.7 ± 9.1 mL to 40.3 ± 11.6 mL), SpO2 (99.5 ± 0.79% to 99.5 ± 0.77%) and EF (61.9 ± 5.9% to 60.9 ± 6.4%) were only slightly changed (P > 0.05). However, cardiac output (4.3 ± 0.9 L/min to 5.4 ± 1.4 L/min) and cardiac index (3.7 ± 0.8 L/min per m2 to 4.5 ± 1.4 L/min per m2 ) increased significantly (P < 0.0001). We conclude that sympathetic stress induced by cold pressor test has marginal effect on ejection fraction and fractional shortening while increasing cardiac output and cardiac index in young healthy adults.

Interactions between myocardial sympathetic denervation and left ventricular mechanical dyssynchrony: A CZT analysis.

BACKGROUND: A correlation between left ventricular (LV) dyssynchrony (LVD) and impaired myocardial sympathetic tone has been hypothesized. We sought to assess the interactions between regional LV sympathetic innervation, perfusion, and mechanical dyssynchrony. METHODS: Eighty-three patients underwent evaluation of LV perfusion and sympathetic innervation on 99mTc-tetrofosmin/123I-metaiodobenzylguanidine (123I-MIBG) imaging. The summed rest score and summed 123I-MIBG score (SS-MIBG) were computed. The extent of "innervation/perfusion" mismatch was defined as the number of denervated LV segments with relatively preserved perfusion. LVD was evaluated on phase analysis and the wall with latest mechanical activation identified. RESULTS: LVD was revealed in 36 (43%) patients. Patients with LVD had more abnormal values of SRS (21 ± 9 vs 10 ± 8, P < 0.001) and SS-MIBG (29 ± 9 vs 17 ± 11, P < 0.001) than those without LVD. The presence of LVD also clustered with a higher burden of "innervation/perfusion" mismatch (P = 0.019). On per-wall analysis, LV walls with delayed mechanical activation showed a higher burden of "innervation/perfusion" mismatch (2.3 ± 1.4 segments) than normally contracting walls (1.3 ± 1.2 segments; P < 0.001). On multivariate analysis, the extent of "innervation/perfusion" mismatch was the only predictor of delayed mechanical activation (P = 0.029). CONCLUSIONS: Patients with LVD show an elevated burden of "innervation/perfusion" mismatch that is concentrated at the level of the most dyssynchronous walls.

Autonomic Neuromodulation Acutely Ameliorates Left Ventricular Strain in Humans.

Low-level transcutaneous vagus nerve stimulation at the tragus (LLTS) is anti-adrenergic. We aimed to evaluate the acute effects of LLTS on left ventricular (LV) function and autonomic tone. Patients with diastolic dysfunction and preserved LV ejection fraction were enrolled in a prospective, randomized, double-blind, 2 × 2 cross-over study. Patients received two separate, 1-h sessions, at least 1 day apart, of active LLTS (20 Hz, 1 mA below the discomfort threshold) and sham stimulation. Echocardiography was performed after LLTS or sham stimulation to assess cardiac function. A 5-min ECG was performed to assess heart rate variability (HRV). Twenty-four patients were enrolled. LV global longitudinal strain improved by 1.8 ± 0.9% during active LLTS compared to sham stimulation (p = 0.001). Relative to baseline, HRV frequency domain components (low frequency, high frequency, and their ratio) were favorably altered after LLTS compared to sham stimulation (all p < 0.05). We concluded that LLTS acutely ameliorates cardiac mechanics by modulating the autonomic tone. Trial registration: NCT02983448.

Influence of vagal control on sex-related differences in left ventricular mechanics and hemodynamics.

Left ventricular (LV) twist mechanics differ between men and women during acute physiological stress, which may be partly mediated by sex differences in autonomic control. While men appear to have greater adrenergic control of LV twist, the potential contribution of vagal modulation to sex differences in LV twist remains unknown. Therefore, the present study examined the role of vagal control on sex differences in LV twist during graded lower body negative pressure (LBNP) and supine cycling. On two separate visits, LV mechanics were assessed using two-dimensional speckle-tracking echocardiography in 18 men (22 ± 2 yr) and 17 women (21 ± 4 yr) during -40- and -60-mmHg LBNP and 25% and 50% of peak supine cycling workload with and without glycopyrrolate (vagal blockade). LV twist was not different at baseline but was greater in women during -60 mmHg in both control (women: 16.0 ± 3.4° and men: 12.9 ± 2.3°, P = 0.004) and glycopyrrolate trials (women: 17.7 ± 5.9° and men: 13.9 ± 3.3°, P < 0.001) due to greater apical rotation during control (women: 11.9 ± 3.6° and men: 7.8 ± 1.5°, P < 0.001) and glycopyrrolate (women: 11.6 ± 4.9° and men: 7.1 ± 3.6°, P = 0.009). These sex differences in LV twist consistently coincided with a greater LV sphericity index (i.e., ellipsoid geometry) in women compared with men. In contrast, LV twist did not differ between the sexes during exercise with or without glycopyrrolate. In conclusion, women have augmented LV twist compared with men during large reductions to preload, even during vagal blockade. As such, differences in vagal control do not appear to contribute to sex differences in the LV twist responses to physiological stress, but they may be related to differences in ventricular geometry. NEW & NOTEWORTHY This is the first study to specifically examine the role of vagal autonomic control on sex-related differences in left ventricular (LV) mechanics. Contrary to our hypothesis, vagal control does not appear to primarily determine sex differences in LV mechanical or hemodynamic responses to acute physiological stress. Instead, differences in LV geometry may be a more important contributor to sex differences in LV mechanics.

Leptin-Aldosterone-Neprilysin Axis: Identification of Its Distinctive Role in the Pathogenesis of the Three Phenotypes of Heart Failure in People With Obesity.

Obesity (especially visceral adiposity) can be associated with 3 different phenotypes of heart failure: heart failure with a reduced ejection fraction, heart failure with a preserved ejection fraction, and high-output heart failure. All 3 phenotypes are characterized by an excessive secretion of aldosterone and sodium retention. In addition, obesity is accompanied by increased signaling through the leptin receptor, which can promote activation of both the sympathetic nervous system and the renin-angiotensin system and can directly stimulate the secretion of aldosterone. The deleterious interaction of leptin and aldosterone is potentiated by the simultaneous action of adiposity and the renal sympathetic nerves to cause overactivity of neprilysin; the loss of the counterbalancing effects of natriuretic peptides is exacerbated by an additional effect of both obesity and heart failure to interfere with adiponectin signaling. This intricate neurohormonal interplay leads to plasma volume expansion as well as to adverse ventricular remodeling and cardiac fibrosis. Furthermore, the activity of aldosterone and neprilysin is not only enhanced by obesity, but these mechanisms can also promote adipogenesis and adipocyte dysfunction, thereby enhancing the positive feedback loop. Last, in elderly obese women, changes in quantity and biology of epicardial adipose tissue further enhances the release of leptin and other proinflammatory adipokines, thereby leading to cardiac and systemic inflammation, end-organ fibrosis, and multiple comorbidities. Regardless of the phenotypic expression, activation of the leptin-aldosterone-neprilysin axis appears to contribute importantly to the evolution and progression of heart failure in people with obesity. Efforts to interfere with the detrimental interactions of this distinctive neurohormonal ecosystem with existing or novel therapeutic agents are likely to yield unique clinical benefits.

Ablation of the Ligament of Marshall and Left Stellate Ganglion Similarly Reduces Ventricular Arrhythmias During Acute Myocardial Infarction.

BACKGROUND: Sympathetic denervation exerts protective effects against ventricular arrhythmias (VAs) induced by acute myocardial infarction. The results of a previous study indicated that the distal part of the ligament of Marshall (LOMLSPV) might be a sympathetic conduit between the left stellate ganglion (LSG) and the ventricles. The present study was designed to compare the effects between LSG and LOMLSPV ablation on ischemia-induced VAs. METHODS: Twenty-nine dogs were randomly divided into sham ablation group (group 1, n=9), LOMLSPV ablation group (group 2, n=10), and LSG ablation group (group 3, n=10). Ablation was performed before occlusion of the left anterior coronary artery. Changes in the heart rate variability, serum norepinephrine, ventricular effective refractory period, and blood pressure induced by LSG stimulation were observed, and the occurrence of VAs was recorded. Immunostaining examinations of LOMLSPV were performed in dogs without ablation. RESULTS: In group 2, LOMLSPV ablation evidently attenuated blood pressure elevation induced by LSG stimulation. Both LOMLSPV ablation and LSG ablation similarly prolonged ventricular effective refractory period and reduced the concentration of serum norepinephrine, the sympathetic index of heart rate variability, and the incidence of VAs compared with sham ablation. Abundant sympathetic nerve fibers were observed in LOMLSPV. CONCLUSIONS: LOMLSPV ablation prevented acute myocardial infarction-induced VAs with the same efficiency as LSG ablation, potentially by blocking the sympathetic pathway from the LSG to the heart.

Inadvertent Left Ventricle Endocardial or Uncomplicated Right Ventricular Pacing: How to Differentiate in the Emergency Department.

BACKGROUND: Temporary transvenous pacemaker implantation is an important and critical procedure for emergency physicians. Traditionally, temporary pacemakers are inserted by electrocardiography (ECG) guidance in the emergency department because fluoroscopy at the bedside in an unstable patient can be limited by time and equipment availability. However, in the presence of atrial septal defect, ventricular septal defect, and patent foramen ovale, the pacemaker lead can be implanted inadvertently into the left ventricle or directly into the coronary sinus instead of right ventricle. Regular pacemaker rhythm can be achieved despite inadvertent implantation of the pacemaker lead into the left ventricle, leading to ignorance of the possibility of lead malposition. CASE REPORT: A 65-year-old female patient with hemodynamic instability and complete atrioventricular block underwent temporary pacemaker implantation via right jugular vein with ECG guidance at the emergency department. Approximately 12 h after implantation, it was noticed that the ECG revealed right bundle branch block (RBBB)-type paced QRS complexes. Diagnostic workup revealed that the lead was inadvertently located in the left ventricular apex. This case illustrates the importance of careful scrutiny of the 12-lead ECG and imaging clues in identifying lead malposition in the emergency department. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Because inadvertent left ventricle endocardial pacing carries a high risk for systemic embolization, it is important to determine whether an RBBB pattern induced by ventricular pacing is the result of a malpositioned lead or uncomplicated transvenous right ventricular pacing.

Stimulation of Epicardial Sympathetic Nerves at Different Sites Induces Cardiac Electrical Instability to Various Degrees.

The cardiac sympathetic nerves distribute across cardiac tissues with uneven density. Yet, to what extent this anatomical heterogeneity affects electrical activity of the left ventricle is largely unknown. Dogs were randomized into non-stimulation control (NC), posterior basal-stimulation (PB), anterior superior-stimulation (AS), apical part-stimulation (AP) group. The epicardial sympathetic nerves at different sites along their distribution were with electrical stimulation (ES) for 4 hours except in the NC group. The myocardial effective refractory period (ERP), ventricular fibrillation threshold (VFT) and density of sympathetic nerves were recorded. Compared with ES at other places, the stimulation at PB site significantly shortened ERP (left ventricular anterior and posterior walls; PB group, 118 ± 4 ms, 106 ± 2 ms; Versus NC group, 155 ± 3.5 ms, 160 ± 3 ms; p < 0.01) and VFT (PB group, 11.5 ± 1.5 V; Versus NC group, 20.5 ± 0.9 V; p < 0.01), and induced remarkable regeneration of the cardiac sympathetic nerves, hence influencing electrical activity of the left ventricle to the most extent. Our study demonstrates that the degree of induced ventricular electrical instability is correlated tightly with the density of sympathetic nerves around ES site, and PB site is a potential target for modulating ventricular electrical activity to the maximal extent.