Early cardiac electrographic and molecular remodeling in a model of status epilepticus and acquired epilepsy

Ictal asystole during epileptic seizures: A case report and narrative review

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Synapse-specific changes in Arc and BDNF in rat hippocampus following chronic temporal lobe epilepsy

Expression of immediate early genes (IEGs) in the brain is important for synaptic plasticity, and probably also in neurodegenerative conditions. To understand the cellular mechanisms of the underlying neuropathophysiological processes in epilepsy, we need to pinpoint changes in concentration of synaptic plasticity-related proteins at subsynaptic levels. In this study, we examined changes in synaptic expression of Activity-regulated cytoskeleton-associated (Arc) and Brai Derived Neurotrophic Factor (BDNF) in a rat model of kainate-induced temporal lobe epilepsy (TLE). Western blotting showed reduced concentrations of Arc and increased concentrations of BDNF in hippocampal synaptosomes in chronic TLE rats. Then, using quantitative electron microscopy, we found corresponding changes in subsynaptic regions in the hippocampus. Specifically, we detected significant reductions in the concentrations of Arc in the presynaptic terminal of Schaffer collateral glutamatergic synapses in the stratum radiatum of the CA1 area in TLE, as well as in their adjacent postsynaptic spines. In CA3, there was a significant reduction of Arc only in the presynaptic terminal cytoplasm. Conversely, in CA3, there was a significant increase in the expression of BDNF in the presynaptic terminal, but not in the postsynaptic spine. Significant increase in BDNF concentration in the CA1 postsynaptic density was also obtained. We hypothesize that the observed changes in Arc and BDNF may contribute to both cognitive impairment and increased excitotoxic vulnerability in chronic epilepsy.

Putative therapeutic impacts of cardiac CTRP9 in ischaemia/reperfusion injury

Recently, cytokines belonging to C1q/tumour necrosis factor‐related proteins (CTRPs) superfamily have attracted increasing attention due to multiple metabolic functions and desirable anti‐inflammatory effects. These various molecular effectors exhibit key roles upon the onset of cardiovascular diseases, making them novel adipo/cardiokines. This review article aimed to highlight recent findings correlated with therapeutic effects and additional mechanisms specific to the CTRP9, particularly in cardiac ischaemia/reperfusion injury (IRI). Besides, the network of the CTPR9 signalling pathway and its possible relationship with IRI were discussed. Together, the discovery of all involved underlying mechanisms could shed light to alleviate the pathological sequelae after the occurrence of IRI.

Heart rate variability alterations in Dravet Syndrome: The role of status epilepticus and a possible association with mortality risk

PURPOSE

Preliminary data suggest that patients with Dravet Syndrome (DS) have a reduced heart rate variability (HRV). This seems particularly evident in patients who experienced sudden unexpected death in epilepsy (SUDEP). This study aims at confirming these findings in a larger cohort and at defining clinical, genetic or electroencephalographic predictors of HRV impairment in DS patients.

METHODS

DS patients followed at our Institution performed a 24h-ECG Holter to derive HRV parameters. We used as control population patients with epilepsy (PWEs) and healthy controls (HCs). In DS patients, we assessed the impact of different clinical, neurophysiological and genetic features on HRV alterations through multiple linear regression. After a mean follow-up of 7.4 ± 3.2 years since the HRV assessment, all DS patients were contacted to record death or life-threatening events.

RESULTS

56 DS patients had a significantly reduced HRV compared to both HCs and PWEs. A recent history of status epilepticus (SE) was the only significant predictor of lower HRV in the multivariate analysis. At follow-up, only one patient died; her HRV was lower than that of all the controls and was in the low range for DS patients.

CONCLUSION

We describe for the first time an association between SE and HRV alterations in DS. Further studies on other SCN1A-related phenotypes and other epilepsies with frequent SE will help clarify this finding. Compared to the literature, our cohort showed better HRV and lower mortality. Although limited, this observation reinforces the role of HRV as a biomarker for mortality risk in DS.

Suppression of Electrographic Seizures Is Associated with Amelioration of QTc Interval Prolongation in Patients with Traumatic Brain Injury

Introduction: Disorders in electroencephalography (EEG) are commonly noted in patients with traumatic brain injury (TBI) and may be associated with electrocardiographic disturbances. Electrographic seizures (ESz) are the most common features in these patients. This study aimed to explore the relationship between ESz and possible changes in QTc interval and spatial QRS-T angle both during ESz and after ESz resolution. Methods: Adult patients with TBI were studied. Surface 12-lead ECGs were recorded using a Cardiax device during ESz events and 15 min after their effective suppression using barbiturate infusion. The ESz events were diagnosed using Masimo Root or bispectral index (BIS) devices. Results: Of the 348 patients considered for possible inclusion, ESz were noted in 72, with ECG being recorded in 21. Prolonged QTc was noted during ESz but significantly ameliorated after ESz suppression (540.19 ± 60.68 ms vs. 478.67 ± 38.52 ms, p < 0.001). The spatial QRS-T angle was comparable during ESz and after treatment. Regional cerebral oximetry increased following ESz suppression (from 58.4% ± 6.2 to 60.5% ± 4.2 (p < 0.01) and from 58.2% ± 7.2 to 60.8% ± 4.8 (p < 0.05) in the left and right hemispheres, respectively). Conclusion: QTc interval prolongation occurs during ESz events in TBI patients but both it and regional cerebral oximetry are improved after suppression of seizures.

Acute and chronic cardiorespiratory consequences of focal intrahippocampal administration of seizure-inducing agents. Implications for SUDEP

The risk factors for SUDEP are undoubtedly heterogenous but the main factor is the frequency of generalized tonic-clonic seizures with apnoea and/or cardiac abnormalities likely precipitating the lethal event. By its very nature modelling SUDEP experimentally is challenging, yet insights into the nature of the lethal event and precipitating factors are vital in order to understand and prevent fatalities. Acute animal models, which induce status epilepticus (SE), can be used to help understand pathophysiological processes during and following seizures, which sometimes lead to death. The most commonly used method to induce seizures and status epilepticus is systemic administration of an ictogenic agent. Microinjection of such agents into restricted regions within the brain induces a more localised epileptic focus and circumvents the risk of direct actions on cardiorespiratory control centres. Both approaches have revealed substantial cardiovascular and respiratory consequences, including death as a result of apnoea, which may be of central origin, obstructive due to laryngospasm or, at least in genetically modified mice, a result of spreading depolarisation to medullary respiratory control centres. SUDEP is by definition a result of epilepsy, which in turn is diagnosed on the basis of two or more unprovoked seizures. The incidence of tonic-clonic seizures is the main risk factor, raising the possibility that repeated seizures cause cumulative pathological and/or pathophysiological changes that contribute to the risk of SUDEP. Chronic experimental models, which induce repeated seizures that in some cases lead to death, do show progressive development of pathophysiological changes in the myocardium, e.g. prolongation of QT the interval of the ECG or, over longer periods, ventricular hypertrophy. However, the currently available evidence indicates that seizure-related deaths are primarily due to apnoeas, but cardiac factors, particularly cumulative cardiac pathophysiologies due to repeated seizures, are potential contributing factors.

Epilepsy duration is an independent factor for electrocardiographic changes in pediatric epilepsy

Objective

Cardiac alterations represent a potential epilepsy‐associated comorbidity. Whether cardiac changes occur as a function of epilepsy duration is not well understood. We sought to evaluate whether cardiac alterations represented a time‐dependent phenomenon in pediatric epilepsy.

Methods

We retrospectively followed pediatric epilepsy patients without preexisting cardiac conditions or ion channelopathies who had history of pediatric intensive care unit admission for convulsive seizures or status epilepticus between 4/2014 and 7/2017. All available 12‐lead electrocardiograms (ECGs) from these patients between 1/2006 and 5/2019 were included. We examined ECG studies for changes in rhythm; PR, QRS, or corrected QT intervals; QRS axis or morphology; ST segment; or T wave. Data were analyzed using multivariable models containing covariates associated with ECG changes or epilepsy duration from the univariate analyses.

Results

127 children with 323 ECGs were included in the analyses. The median epilepsy duration was 3.9 years (IQR 1.3‐8.4 years) at the time of an ECG study and a median of 2 ECGs (IQR 1‐3) per subject. The clinical encounters associated with ECGs ranged from well‐child visits to status epilepticus. We observed changes in 171 ECGs (53%), with 83 children (65%) had at least 1 ECG with alterations. In a multivariable logistic regression model adjusting for potentially confounding variables and accounting for clustering by patient, epilepsy duration was independently associated with altered ECGs for each year of epilepsy (OR: 1.1, 95% CI: 1.0‐1.2, P = .002). Extrapolating from this model, children with epilepsy durations of 10 and 15 years had 2.9 and 4.9 times the odds of having ECG changes, respectively.

Significance

Cardiac alterations may become more common with increasing epilepsy duration in select pediatric epilepsy patients. Future studies are needed to determine the potential clinical implications and the generalizability of these observations.

Cardiac dysregulation following intrahippocampal kainate-induced status epilepticus

Status epilepticus (SE) is a prevalent disorder associated with significant morbidity, including the development of epilepsy and mortality. Cardiac arrhythmias (i.e. inappropriate sinus tachycardia and bradycardia, asystole, and atrioventricular blocks) are observed in patients following SE. We characterized ictal (during a seizure) and interictal (between seizure) cardiac arrhythmogenesis following SE using continuous electrocardiography and video electroencephalography (vEEG) recordings throughout a 14-day monitoring period in an intrahippocampal chemoconvulsant mouse model that develops epilepsy. We quantified heart rhythm abnormalities and examined whether the frequency of cardiac events correlated with epileptiform activity, circadian (light/dark) cycle, the presence of seizures, and survival during this period of early epileptogenesis (the development of epilepsy) following SE. Shortly following SE, mice developed an increased interictal heart rate and heart rhythm abnormalities (i.e. sinus pause and sinus arrhythmias) when compared to control mice. Heart rhythm abnormalities were more frequent during the light cycle and were not correlated with increased epileptiform activity or seizure frequency. Finally, SE animals had early mortality, and a death event captured during vEEG recording demonstrated severe bradycardia prior to death. These cardiac changes occurred within 14 days after SE and may represent an early risk factor for sudden death following SE.

Acquired cardiac channelopathies in epilepsy: Evidence, mechanisms, and clinical significance

There is growing evidence that cardiac dysfunction in patients with chronic epilepsy could play a pathogenic role in sudden unexpected death in epilepsy (SUDEP). Recent animal studies have revealed that epilepsy secondarily alters the expression of cardiac ion channels alongside abnormal cardiac electrophysiology and remodeling. These molecular findings represent novel evidence for an acquired cardiac channelopathy in epilepsy, distinct from inherited ion channels mutations associated with cardiocerebral phenotypes. Specifically, seizure activity has been shown to alter the messenger RNA (mRNA) and protein expression of voltage-gated sodium channels (Na_v 1.1, Na_v 1.5), voltage-gated potassium channels (K_v 4.2, K_v 4.3), sodium-calcium exchangers (NCX1), and nonspecific cation-conducting channels (HCN2, HCN4). The pathophysiology may involve autonomic dysfunction and structural cardiac disease, as both are independently associated with epilepsy and ion channel dysregulation. Indeed, in vivo and in vitro studies of cardiac pathology reveal a complex network of signaling pathways and transcription factors regulating ion channel expression in the setting of sympathetic overactivity, cardiac failure, and hypertrophy. Other mechanisms such as circulating inflammatory mediators or exogenous effects of antiepileptic medications lack evidence. Moreover, an acquired cardiac channelopathy may underlie the electrophysiologic cardiac abnormalities seen in chronic epilepsy, potentially contributing to the increased risk of malignant arrhythmias and sudden death. Therefore, further investigation is necessary to establish whether cardiac ion channel dysregulation similarly occurs in patients with epilepsy, and to characterize any pathogenic relationship with SUDEP.

Pin1 Is Regulated by CaMKII Activation in Glutamate-Induced Retinal Neuronal Regulated Necrosis

In our previous study, we reported that peptidyl-prolyl isomerase 1 (Pin1)-modulated regulated necrosis (RN) occurred in cultured retinal neurons after glutamate injury. In the current study, we investigated the role of calcium/calmodulin-dependent protein kinase II (CaMKII) in Pin1-modulated RN in cultured rat retinal neurons, and in an animal in vivo model. We first demonstrated that glutamate might lead to calcium overloading mainly through ionotropic glutamate receptors activation. Furthermore, CaMKII activation induced by overloaded calcium leads to Pin1 activation and subsequent RN. Inactivation of CaMKII by KN-93 (KN, i.e., a specific CaMKII inhibitor) application can decrease the glutamate-induced retinal neuronal RN. Finally, by using an animal in vivo model, we also demonstrated the important role of CaMKII in glutamate-induced RN in rat retina. In addition, flash electroretinogram results provided evidence that the impaired visual function induced by glutamate can recover after CaMKII inhibition. In conclusion, CaMKII is an up-regulator of Pin1 and responsible for the RN induced by glutamate. This study provides further understanding of the regulatory pathway of RN and is a complementary mechanism for Pin1 activation mediated necrosis. This finding will provide a potential target to protect neurons from necrosis in neurodegenerative diseases, such as glaucoma, diabetic retinopathy, and even central nervous system diseases.

Genetic ablation or pharmacological inhibition of Kv1.1 potassium channel subunits impairs atrial repolarization in mice

Voltage-gated Kv1.1 potassium channel α-subunits, encoded by the Kcna1 gene, have traditionally been regarded as neural-specific with no expression or function in the heart. However, recent data revealed that Kv1.1 subunits are expressed in atria where they may have an overlooked role in controlling repolarization and arrhythmia susceptibility independent of the nervous system. To explore this concept in more detail and to identify functional and molecular effects of Kv1.1 channel impairment in the heart, atrial cardiomyocyte patch-clamp electrophysiology and gene expression analyses were performed using Kcna1 knockout ( Kcna1-/-) mice. Specifically, we hypothesized that Kv1.1 subunits contribute to outward repolarizing K+ currents in mouse atria and that their absence prolongs cardiac action potentials. In voltage-clamp experiments, dendrotoxin-K (DTX-K), a Kv1.1-specific inhibitor, significantly reduced peak outward K+ currents in wild-type (WT) atrial cells but not Kcna1-/- cells, demonstrating an important contribution by Kv1.1-containing channels to mouse atrial repolarizing currents. In current-clamp recordings, Kcna1-/- atrial myocytes exhibited significant action potential prolongation which was exacerbated in right atria, effects that were partially recapitulated in WT cells by application of DTX-K. Quantitative RT-PCR measurements showed mRNA expression remodeling in Kcna1-/- atria for several ion channel genes that contribute to the atrial action potential including the Kcna5, Kcnh2, and Kcnj2 potassium channel genes and the Scn5a sodium channel gene. This study demonstrates a previously undescribed heart-intrinsic role for Kv1.1 subunits in mediating atrial repolarization, thereby adding a new member to the already diverse collection of known K+ channels in the heart.

Changes in synaptic AMPA receptor concentration and composition in chronic temporal lobe epilepsy

Excitotoxicity caused by excessive stimulation of glutamate receptors, resulting in pathologically increased Ca²⁺-concentrations, is a decisive factor in neurodegenerative diseases. We investigated long-term changes in synaptic contents of AMPA receptor subunits that play important roles in calcium regulation in chronic epilepsy. Such plastic changes may be either adaptive or detrimental. We used a kainic acid (KA)-based rat model of chronic temporal lobe epilepsy (TLE). Using hippocampal synaptosomes, we found significant reductions in the concentration of the AMPA receptor subunits GluA1 and GluA2, and the NMDA receptor subunit NR2B. The relative size of GluA1 and GluA2 reductions were almost identical, at 28% and 27%, respectively. In order to determine whether the synaptic reduction of the AMPA receptor subunits actually reflected the pool of receptors present along the postsynaptic density (PSD), as opposed to cytoplasmic or extrasynaptic pools, we performed postembedding immunogold electron microscopy (EM) of GluA1 and GluA2 in Schaffer collateral synapses in the hippocampal CA1 area. We found significant reductions, at 32% and 52% of GluA1 and GluA2 subunits, respectively, along the PSD, indicating that these synapses undergo lasting changes in glutamatergic neurotransmission during chronic TLE. When compared to the overall concentration and composition of AMPA receptors expressed in the brain, there was a relative increase in GluA2-lacking AMPA receptor subunits following chronic epilepsy. These changes in synaptic AMPA receptor subunits may possibly contribute to further aggravate the excitotoxic vulnerability of the neurons as well as have significant implications for hippocampal cognitive functions.

Cardiac-derived CTRP9 protects against myocardial ischemia/reperfusion injury via calreticulin-dependent inhibition of apoptosis

Cardiokines play an essential role in maintaining normal cardiac functions and responding to acute myocardial injury. Studies have demonstrated the heart itself is a significant source of C1q/TNF-related protein 9 (CTRP9). However, the biological role of cardiac-derived CTRP9 remains unclear. We hypothesize cardiac-derived CTRP9 responds to acute myocardial ischemia/reperfusion (MI/R) injury as a cardiokine. We explored the role of cardiac-derived CTRP9 in MI/R injury via genetic manipulation and a CTRP9-knockout (CTRP9-KO) animal model. Inhibition of cardiac CTRP9 exacerbated, whereas its overexpression ameliorated, left ventricular dysfunction and myocardial apoptosis. Endothelial CTRP9 expression was unchanged while cardiomyocyte CTRP9 levels decreased after simulated ischemia/`reperfusion (SI/R) in vitro. Cardiomyocyte CTRP9 overexpression inhibited SI/R-induced apoptosis, an effect abrogated by CTRP9 antibody. Mechanistically, cardiac-derived CTRP9 activated anti-apoptotic signaling pathways and inhibited endoplasmic reticulum (ER) stress-related apoptosis in MI/R injury. Notably, CTRP9 interacted with the ER molecular chaperone calreticulin (CRT) located on the cell surface and in the cytoplasm of cardiomyocytes. The CTRP9-CRT interaction activated the protein kinase A-cAMP response element binding protein (PKA-CREB) signaling pathway, blocked by functional neutralization of the autocrine CTRP9. Inhibition of either CRT or PKA blunted cardiac-derived CTRP9's anti-apoptotic actions against MI/R injury. We further confirmed these findings in CTRP9-KO rats. Together, these results demonstrate that autocrine CTRP9 of cardiomyocyte origin protects against MI/R injury via CRT association, activation of the PKA-CREB pathway, ultimately inhibiting cardiomyocyte apoptosis.

Myocardial remodeling and susceptibility to ventricular tachycardia in a model of chronic epilepsy

Objective

Sympathetic predominance and ventricular repolarization abnormalities represent epilepsy‐associated cardiac alterations and may underlie seizure‐induced ventricular arrhythmias. Myocardial ion channel and electrical remodeling have been described early in epilepsy development and may contribute to ventricular repolarization abnormalities and excitability. Using the pilocarpine‐induced acquired epilepsy model we sought to examine whether altered myocardial ion channel levels and electrophysiological changes also occur in animals with long‐standing epilepsy.

Methods

We examined myocardial adrenergic receptor and ion channel protein levels of epileptic and age‐matched sham rats (9–20 months old) using western blotting. Cardiac electrical properties were examined using optical mapping ex vivo and electrophysiology in vivo. We investigated the propensity for ventricular tachycardia (VT) and the effects of β‐adrenergic blockade on ventricular electrical properties and excitability in vivo.

Results

In animals with long‐standing epilepsy, we observed decreased myocardial voltage‐gated K⁺ channels Kv_4.2 and Kv_4.3, which are known to underlie early ventricular repolarization in rodents. Decreased β1 and increased α1_A adrenergic receptor protein levels occurred in the myocardium of chronically epileptic animals consistent with elevated sympathetic tone. These animals exhibited many cardiac electrophysiological abnormalities, represented by longer QRS and corrected QT (QTc) intervals in vivo, slower conduction velocity ex vivo, and stimulation‐induced VT. Administration of a β‐adrenergic antagonist late in epilepsy was beneficial, as the therapy shortened the QTc interval and decreased stimulation‐induced VT.

Significance

Our findings demonstrate that myocardial ion channel remodeling and sympathetic predominance, risk factors for increased ventricular excitability and arrhythmias, persist in chronic epilepsy. The beneficial effects of β‐adrenergic antagonist treatment late in the course of epilepsy suggest that attenuating elevated sympathetic tone may represent a therapeutic target for ameliorating epilepsy‐associated cardiac morbidity.

Epilepsy is associated with ventricular alterations following convulsive status epilepticus in children

Objective

Convulsive status epilepticus can exert profound cardiovascular effects in adults, including ventricular depolarization–repolarization abnormalities. Whether status epilepticus adversely affects ventricular electrical properties in children is less understood. Therefore, we sought to characterize ventricular alterations and the associated clinical factors in children following convulsive status epilepticus.

Methods

We conducted a 2‐year retrospective case–control study. Children between 1 month and 21 years of age were included if they were admitted to the pediatric intensive care unit with primary diagnosis of convulsive status epilepticus and had 12‐lead electrocardiogram (ECG) within 24 h of admission. Children with heart disease or ion channelopathy, or who were on vasoactive medications were excluded. Age‐matched control subjects had no history of seizures or epilepsy. The primary outcome was ventricular abnormalities represented by ST segment changes, abnormal T wave, QRS axis deviation, and corrected QT (QTc) interval prolongation. The secondary outcomes included QT/RR relationship, beat‐to‐beat QTc interval variability, ECG interval measurement between groups, and clinical factors associated with ECG abnormalities.

Results

Of 317 eligible children, 59 met the inclusion criteria. History of epilepsy was present in 31 children (epileptic) and absent in 28 children (nonepileptic). Compared with the control subjects (n = 31), the status epilepticus groups were more likely to have an abnormal ECG, with overall odds ratios of 3.8 and 7.0 for the nonepileptic and the epileptic groups, respectively. Simple linear regression analysis demonstrated that children with epilepsy exhibited impaired dependence and adaptation of the QT interval on heart rate. Beat‐to‐beat QTc interval variability, a marker of ventricular repolarization instability, was increased in children with epilepsy.

Significance

Convulsive status epilepticus can adversely affect ventricular electrical properties and stability in children, especially those with epilepsy. These findings suggest that children with epilepsy may be particularly vulnerable to seizure‐induced arrhythmias. Therefore, postictal cardiac surveillance may be warranted in this population.