Effects of antiepileptic drug therapy on heart rate variability in children with epilepsy

Association of minor electrocardiographic (ECG) abnormalities with epilepsy duration in children: A manifestation of the epileptic heart?

PURPOSE

Cardiac abnormalities resulting from chronic epilepsy ("the epileptic heart") constitute a well-recognized comorbidity. However, the association of cardiac alterations with epilepsy duration remains understudied. We sought to evaluate this association using electrocardiogram (ECG).

METHODS

We prospectively enrolled children between 1 months and 18 years of age without known cardiac conditions or ion channelopathies during routine clinic visits. ECGs were categorized as abnormal if there were alterations in rhythm; PR, QRS, or corrected QT interval; QRS axis or morphology; ST segment or T wave. An independent association between ECG abnormalities and epilepsy duration was evaluated using multivariable logistic regression modeling.

RESULTS

213 children were enrolled. 100 ECGs (47%) exhibited at least one alteration; most commonly in the ST segment (37, 17%) and T wave (29, 11%). Children with normal ECGs had shorter epilepsy duration as compared to those with ECG abnormalities (46 [18-91] months vs. 73 [32-128 months], p = 0.004). A multivariable logistic regression model demonstrated that increasing epilepsy duration was independently associated with the presence of ECG abnormalities (OR=1.09, 95% CI=1.02-1.16, p = 0.008), adjusted for seizure frequency, generalized tonic-clonic/focal to bilateral tonic-clonic seizures as the predominant seizure type, and number of channel-modifying anti-seizure medications. Increasing epilepsy duration was also independently associated with the presence of ST/T wave abnormalities (OR=1.09, 95% CI=1.01-1.16, p = 0.017), adjusted for the same covariates.

SIGNIFICANCE

Increasing epilepsy duration is independently associated with the presence of minor ECG abnormalities. Additional studies are needed to evaluate whether this finding may represent a manifestation of the "epileptic heart".

Vagus nerve stimulation and heart rate variability: A scoping review of a somatic oscillatory signal

The goal of this review is to synthesize the literature on vagus nerve stimulator (VNS)-related changes in heart rate variability (HRV) in patients with drug-resistant epilepsy (DRE) and assess the role of these changes in seizure relief. A scoping literature review was performed with the following inclusion criteria: primary articles written in English, involved implantable VNS in humans, and had HRV as a primary outcome. Twenty-nine studies were retrieved, however with considerable heterogeneity in study methods. The overall depression in HRV seen in DRE patients compared to healthy controls persisted even after VNS implant, indicating that achieving "healthy" HRV is not necessary for VNS therapeutic success. Within DRE patients, changes in frequency domain parameters six months after VNS implant returned to baseline after a year. The mechanism of how VNS reduces seizure burden does not appear to be significantly related to alterations in baseline HRV. However, the subtlety of sympathetic/parasympathetic signaling likely requires a more structured approach to experimental and analytic techniques than currently found in the literature.

The effect of epilepsy and antiseizure medications on cardiac autonomic functions in children with epilepsy

BACKGROUND

Autonomic manifestations have been frequently studied in adults with epilepsy. Here, we evaluated cardiac autonomic (ANS) functions in children with epilepsy in the interictal period and determined the risks for their dysfunctions.

RESEARCH DESIGN AND METHODS

This study included 60 patients (boys = 25; girls = 35 age: 14.53 ± 2.54 yrs) and 25 controls. Patients were well-controlled on antiseizure medications (ASMs). The battery of testing included measuring resting heart rate (HR) and blood pressure (BP), 30:15 ratio, HR variability (HRV) response to deep breathing, Valsalva ratio and BP changes in response to standing, isometric exercise and cold.

RESULTS

Dizziness was reported in 25%. Autonomic dysfunctions were found in 45% (n = 27). Manifestations included high frequencies of abnormal 30:15 ratio (22%), HRV responses to deep breathing (45%), Valsalava ratio (45%), and BP responses to standing (35%), isometric exercise (27%) and cold (27%), indicating parasympathetic and sympathetic hypofunctions. There were positive correlations between parasympathetic and sympathetic dysfunctions. Logistic analysis showed that the durations of epilepsy and ASMs therapy were associated with ANS dysfunctions [95% CI: 0.895-4.719, p = 0.004].

CONCLUSIONS

Parasympathetic and sympathetic autonomic hypofunctions are common in children with epilepsy. This could be due to the depressant effect of sodium channel blocker ASMs on central and/or cardiac autonomic systems.

Is anti-seizure medication the culprit of SUDEP?

BACKGROUND

Heart rate variability (HRV) reduction is a potential biomarker for sudden cardiac death. This study aimed to study the effects of anti-seizure medications (ASMs), adjusted with reported factors associated with sudden unexpected death in epilepsy (SUDEP) on HRV parameters.

METHODS

We recruited patients who were admitted in our epilepsy monitoring unit between January 2013 and December 2021. Two 5-min electrocardiogram epochs during wakefulness and sleep were selected in each patient. HRV analysis with Python® software was performed. The imputed datasets were used for linear regression analysis to assess association between each ASM item and all HRV parameters. The effects of ASM on HRV parameters were subsequently adjusted with the significant clinical characteristics and the concomitant use of other ASMs, respectively.

RESULTS

Carbamazepine (CBZ), levetiracetam (LEV), lamotrigine (LTG), and clonazepam (CZP) were statistically significantly associated with changes of sleep HRV parameters. Only CBZ showed negative effects with reduction in HRV, evidenced as lower standard deviation of RR interval (SDNN), even when adjusted with concomitant use of other ASMs (p = 0.045) and had a trend of significance when adjusted with significant clinical characteristics of concurrent taking of beta-blocker drug (p = 0.052). LEV and CZP showed opposite effects with increased HRV even when adjusted with significant clinical characteristics and the concomitant use of other ASMs.

CONCLUSIONS

CBZ showed negative effects on HRV. We proposed that CBZ should be cautiously used in patients with known risks for SUDEP. In addition, HRV assessment should be performed prior to commencing CBZ and re-performed in follow-up in cases of prolonged use.

Exploring Autonomic Alterations during Seizures in Temporal Lobe Epilepsy: Insights from a Heart-Rate Variability Analysis

Epilepsy's impact on cardiovascular function and autonomic regulation, including heart-rate variability, is complex and may contribute to sudden unexpected death in epilepsy (SUDEP). Lateralization of autonomic control in the brain remains the subject of debate; nevertheless, ultra-short-term heart-rate variability (HRV) analysis is a useful tool for understanding the pathophysiology of autonomic dysfunction in epilepsy patients. A retrospective study reviewed medical records of patients with temporal lobe epilepsy who underwent presurgical evaluations. Data from 75 patients were analyzed and HRV indices were extracted from electrocardiogram recordings of preictal, ictal, and postictal intervals. Various HRV indices were calculated, including time domain, frequency domain, and nonlinear indices, to assess autonomic function during different seizure intervals. The study found significant differences in HRV indices based on hemispheric laterality, language dominancy, hippocampal atrophy, amygdala enlargement, sustained theta activity, and seizure frequency. HRV indices such as the root mean square of successive differences between heartbeats, pNN50, normalized low-frequency, normalized high-frequency, and the low-frequency/high-frequency ratio exhibited significant differences during the ictal period. Language dominancy, hippocampal atrophy, amygdala enlargement, and sustained theta activity were also found to affect HRV. Seizure frequency was correlated with HRV indices, suggesting a potential relationship with the risk of SUDEP.

Heart rate variability analysis for the prediction of EEG grade in infants with hypoxic ischaemic encephalopathy within the first 12 h of birth

Background and aims

Heart rate variability (HRV) has previously been assessed as a biomarker for brain injury and prognosis in neonates. The aim of this cohort study was to use HRV to predict the electroencephalography (EEG) grade in neonatal hypoxic-ischaemic encephalopathy (HIE) within the first 12 h.

Methods

We included 120 infants with HIE recruited as part of two European multi-centre studies, with electrocardiography (ECG) and EEG monitoring performed before 12 h of age. HRV features and EEG background were assessed using the earliest 1 h epoch of ECG-EEG monitoring. HRV was expressed in time, frequency and complexity features. EEG background was graded from 0-normal, 1-mild, 2-moderate, 3-major abnormalities to 4-inactive. Clinical parameters known within 6 h of birth were collected (intrapartum complications, foetal distress, gestational age, mode of delivery, gender, birth weight, Apgar at 1 and 5, assisted ventilation at 10 min). Using logistic regression analysis, prediction models for EEG severity were developed for HRV features and clinical parameters, separately and combined. Multivariable model analysis included 101 infants without missing data.

Results

Of 120 infants included, 54 (45%) had normal-mild and 66 (55%) had moderate-severe EEG grade. The performance of HRV model was AUROC 0.837 (95% CI: 0.759-0.914) and clinical model was AUROC 0.836 (95% CI: 0.759-0.914). The HRV and clinical model combined had an AUROC of 0.895 (95% CI: 0.832-0.958). Therapeutic hypothermia and anti-seizure medication did not affect the model performance.

Conclusions

Early HRV and clinical information accurately predicted EEG grade in HIE within the first 12 h of birth. This might be beneficial when EEG monitoring is not available in the early postnatal period and for referral centres who may want some objective information on HIE severity.

Effects of levetiracetam treatment on autonomic nervous system functions in pediatric epilepsy patients

BACKGROUND

This study investigated the effects of levetiracetam (LEV) treatment on cardiac rhythm and heart rate variability.

METHODS

The study included two groups of patients diagnosed with non-lesional epilepsy who had not yet been treated and who presented to the outpatient pediatric neurology clinic at Van Training and Research Hospital, Van, Turkey, between 2019 and 2020. The heart rate variability (HRV) of 47 patients in the first group, before and at the 3rd month of treatment, and intravenous (IV) LEV loading in 13 patients in the second group was evaluated by Holter electrocardiography (ECG).

RESULTS

It was determined that the values of triangular index, standard deviation of the RR intervals over a 24-hour period (SDNN), standard deviation of all 5-minute mean RR intervals (SDANN), mean of standard deviations of all normal RR intervals (SDNNI), the percentage of RR intervals with >50-millisecond variation (PNN50), and the square root of mean squared differences of successive RR intervals (RMSSD). HRV of 47 patients under LEV treatment significantly increased in the 3rd month of treatment compared to baseline (p < 0.05). No difference was found in HRV between the intravenous loading and the control group (p > 0.05).

CONCLUSIONS

Our study suggests that the sympathovagal balance before treatment in the patient group is in favor of the sympathetic nervous system and that the sympathovagal imbalance improves after treatment. Our results show that LEV monotherapy and loading have no negative effect on HRV and potential cardiac arrhythmia risk in children with epilepsy.

Early transient dysautonomia predicts the risk of infantile epileptic spasm syndrome onset: A prospective cohort study

Background

Infantile epileptic spasm syndrome (IESS) is an age-dependent epileptic encephalopathy with a significant risk of developmental regression. This study investigates the association between heart rate variability (HRV) in infants at risk of IESS and the clinical onset of IESS.

Methods

Sixty neonates at risk of IESS were prospectively followed from birth to 12 months with simultaneous electroencephalogram (EEG) and electrocardiogram recordings for 60 min at every 2-month interval. HRV metrics were calculated from 5 min time-epoch during sleep including frequency domain measures, Poincare analysis including cardiac vagal index (CVI) and cardiac sympathetic index (CSI), and detrended fluctuation analysis (DFA α1, DFA α2). To assess the effect of each HRV metric at the 2-month baseline on the time until the first occurrence of either hypsarrhythmia on EEG and/or clinical spasm, univariate cox-proportional hazard models were fitted for each HRV metric.

Results

Infantile epileptic spasm syndrome was diagnosed in 20/60 (33%) of the cohort in a 12-month follow-up and 3 (5%) were lost to follow-up. The median age of developing hypsarrhythmia was 25 (7-53) weeks and clinical spasms at 24 (8-40) weeks. Three (5%) patients had clinical spasms without hypsarrhythmia, and 5 (8%) patients had hypsarrhythmia before clinical spasms at the initial presentation. The infants with high CSI (hazard ratio 2.5, 95% CI 1.2-5.2, P = 0.01) and high DFA α1 (hazard ratio 16, 95% CI 1.1-240, P = 0.04) at 2 months were more likely to develop hypsarrhythmia by the first year of age. There was a trend toward decreasing CSI and DFA α1 and increasing CVI in the first 8 months of age.

Conclusion

Our data suggest that relative sympathetic predominance at an early age of 2 months may be a potential predictor for developing IESS. Hence, early HRV patterns may provide valuable prognostic information in children at risk of IESS allowing early detection and optimization of cognitive outcomes. Whether early intervention to restore sympathovagal balance per se would provide clinical benefit must be addressed by future studies.

Sudden Death and Cardiac Arrythmia With Lamotrigine: A Rapid Systematic Review

BACKGROUND AND OBJECTIVES

A recent Food and Drug Administration warning concerning an arrhythmogenic potential of lamotrigine created concern in the neurologic community. This warning was based on in vitro studies, but no clinically relevant risk was considered. This rapid systematic review aims to elucidate the risk of lamotrigine on sudden death or ECG abnormalities.

METHODS

We conducted a systematic search of Ovid Medline and Ovid Embase, including randomized controlled trials and observational studies and studies of people with or without epilepsy, with the outcome measures sudden unexpected death in epilepsy (SUDEP) or sudden cardiac death as well as the development or worsening of ECG abnormalities. We evaluated the sudden death definitions used in all included studies, as some could have used unclear or overlapping definitions. We used the American Academy of Neurology risk of bias tool to evaluate the class of evidence and the GRADE approach to evaluate our confidence in the evidence.

RESULTS

We included 26 studies with 24,962 participants, of whom 2,326 used lamotrigine. Twelve studies showed no significant risk of SUDEP for lamotrigine users. One study reporting on sudden cardiac death and 3 studies with unclear sudden death definitions did not report an elevated risk of death in lamotrigine users compared to controls. In 10 studies reporting on ECG measures, there was no statistically significant increased risk among lamotrigine users except in 2 studies. These 2 studies reported either "slight increases" in PR interval or an increased PQ interval that the primary study authors believed to be related to structural cardiac differences rather than an effect of lamotrigine. One study was rated Class II; all others were Class III or IV. We had very low confidence in the evidence following the GRADE assessment. None of the studies examined the risk of lamotrigine in people with preexisting cardiac conditions.

DISCUSSION

There is insufficient evidence to support or refute that lamotrigine is associated with sudden death or ECG changes in people with or without epilepsy as compared to antiseizure medication or placebo, due to the high risk of bias in most studies and low precision and inconsistency in the reported results.

Wearable device assessments of antiseizure medication effects on diurnal patterns of electrodermal activity, heart rate, and heart rate variability

Patient-generated health data provide a great opportunity for more detailed ambulatory monitoring and more personalized treatments in many diseases. In epilepsy, robust diagnostics applicable to the ambulatory setting are needed as diagnosis and treatment decisions in current clinical practice are primarily reliant on patient self-reports, which are often inaccurate. Recent work using wearable devices has focused on methods to detect and forecast epileptic seizures. Whether wearable device signals may also contain information about the effect of antiseizure medications (ASMs), which may ultimately help to better monitor their efficacy, has not been evaluated yet. Here we systematically investigated the effect of ASMs on different data modalities (electrodermal activity, EDA, heart rate, HR, and heart rate variability, HRV) simultaneously recorded by a wearable device in 48 patients with epilepsy over several days in the epilepsy long-term monitoring unit at a tertiary hospital. All signals exhibited characteristic diurnal variations. HRV, but not HR or EDA-based metrics, were reduced by ASMs. By assessing multiple signals related to the autonomic nervous system simultaneously, our results provide novel insights into the effects of ASMs on the sympathetic and parasympathetic interplay in the setting of epilepsy and indicate the potential of easy-to-wear wearable devices for monitoring ASM action. Future work using longer data may investigate these metrics on multidien cycles and their utility for detecting seizures, assessing seizure risk, or informing treatment interventions.

Comparing Ictal Cardiac Autonomic Changes in Patients with Frontal Lobe Epilepsy and Temporal Lobe Epilepsy by Ultra-Short-Term Heart Rate Variability Analysis

Background and Objectives: Abnormal epileptic discharges in the brain can affect the central brain regions that regulate autonomic activity and produce cardiac symptoms, either at onset or during propagation of a seizure. These autonomic alterations are related to cardiorespiratory disturbances, such as sudden unexpected death in epilepsy. This study aims to investigate the differences in cardiac autonomic function between patients with temporal lobe epilepsy (TLE) and frontal lobe epilepsy (FLE) using ultra-short-term heart rate variability (HRV) analysis around seizures. Materials and Methods: We analyzed electrocardiogram (ECG) data recorded during 309 seizures in 58 patients with epilepsy. Twelve patients with FLE and 46 patients with TLE were included in this study. We extracted the HRV parameters from the ECG signal before, during and after the ictal interval with ultra-short-term HRV analysis. We statistically compared the HRV parameters using an independent t-test in each interval to compare the differences between groups, and repeated measures analysis of variance was used to test the group differences in longitudinal changes in the HRV parameters. We performed the Tukey-Kramer multiple comparisons procedure as the post hoc test. Results: Among the HRV parameters, the mean interval between heartbeats (RRi), normalized low-frequency band power (LF) and LF/HF ratio were statistically different between the interval and epilepsy types in the t-test. Repeated measures ANOVA showed that the mean RRi and RMSSD were significantly different by epilepsy type, and the normalized LF and LF/HF ratio significantly interacted with the epilepsy type and interval. Conclusions: During the pre-ictal interval, TLE patients showed an elevation in sympathetic activity, while the FLE patients showed an apparent increase and decrease in sympathetic activity when entering and ending the ictal period, respectively. The TLE patients showed a maintained elevation of sympathetic and vagal activity in the pos-ictal interval. These differences in autonomic cardiac characteristics between FLE and TLE might be relevant to the ictal symptoms which eventually result in SUDEP.

Autonomic Characteristics of Sudden Unexpected Death in Epilepsy in Children-A Systematic Review of Studies and Their Relevance to the Management of Epilepsy in Rett Syndrome

Aim: To systematically identify and critically appraise studies that investigate the autonomic characteristics of Sudden Unexpected Death in Epilepsy (SUDEP) in the pediatric population. We also wanted to explore how this information would be relevant to the management of epilepsy in patients with Rett Syndrome.

Method: Using PRISMA guidelines, a systematic review of PubMed, Scopus, Cochrane, PsycINFO, Embase, and Web of Science databases was performed to identify eligible studies. After extracting data from the included studies, a thematic analysis was undertaken to identify emerging themes. A quality appraisal was also done to assess the quality of the included studies.

Results: The systematic search revealed 41 records, and 15 full-text articles on the autonomic characteristics of SUDEP in children were included in the final analysis. Following thematic analysis, three themes were identified (I) modulation in sympathovagal tone, (II) pre- and post-ictal autonomic changes, and (III) other markers of autonomic dysregulation in children with epilepsy. Modulation in sympathovagal tone emerged as the theme with the highest frequency followed by pre- and post-ictal autonomic changes. While the themes provide additional insight into the management of epilepsy in the Rett Syndrome population, the quality of evidence concerning the autonomic characteristics of SUDEP in the pediatric population was low and underscores the importance of much needed research in this area.

Conclusion: The mechanism of SUDEP in the pediatric population is complex and involves an interplay between several components of the autonomic nervous system. While direct clinical inferences regarding pediatric SUDEP could not be made, the thematic analysis does suggest that in vulnerable populations such as Rett Syndrome, where there is already a pervasive autonomic dysregulation, pro-active surveillance of the autonomic profile in this patient group would be useful to better manage epilepsy and reduce the SUDEP risk.

Interictal autonomic dysfunction

PURPOSE OF REVIEW

Epilepsy is associated with autonomic dysfunction. Here, we provide an up-to-date review on measures of interictal autonomic function, focusing on heart rate variability (HRV), baroreflex sensitivity (BRS) and electrodermal activity (EDA).

RECENT FINDINGS

Resting HRV, BRS and EDA are altered in patients with epilepsy compared with healthy controls. A larger body of work is available for HRV compared with BRS and EDA, and points to interictal HRV derangements across a wide range of epilepsies, including focal, generalized, and combined generalized and focal epilepsies. HRV alterations are most pronounced in temporal lobe epilepsy, Dravet syndrome and drug-resistant and chronic epilepsies. There are conflicting data on the effect of antiseizure medications on measures of interictal autonomic function. However, carbamazepine has been associated with decreased HRV. Epilepsy surgery and vagus nerve stimulation do not appear to have substantial impact on measures of interictal autonomic function but well designed studies are lacking.

SUMMARY

Patients with epilepsy, particularly those with longstanding uncontrolled seizures, have measurable alterations of resting autonomic function. These alterations may be relevant to the increased risk of premature mortality in epilepsy, including sudden unexpected death in epilepsy, which warrants investigation in future research.

Impairment of Cardiac Autonomic Nerve Function in Pre-school Children With Intractable Epilepsy

Objective: Intractable epilepsy and uncontrolled seizures could affect cardiac function and the autonomic nerve system with a negative impact on children's growth. The aim of this study was to investigate the variability and complexity of cardiac autonomic function in pre-school children with pediatric intractable epilepsy (PIE). Methods: Twenty four-hour Holter electrocardiograms (ECGs) from 93 patients and 46 healthy control subjects aged 3-6 years were analyzed by the methods of traditional heart rate variability (HRV), multiscale entropy (MSE), and Kurths-Wessel symbolization entropy (KWSE). Receiver operating characteristic (ROC) curve analysis was used to estimate the overall discrimination ability. Net reclassification improvement (NRI) and integrated discrimination improvement (IDI) models were also analyzed. Results: Pre-school children with PIE had significantly lower HRV measurements than healthy controls in time (Mean_RR, SDRR, RMSSD, pNN50) and frequency (VLF, LF, HF, LF/HF, TP) domains. For the MSE analysis, area 1_5 in awake state was lower, and areas 6_15 and 6_20 in sleep state were higher in PIE with a significant statistical difference. KWSE in the PIE group was also inferior to that in healthy controls. In ROC curve analysis, pNN50 had the greatest discriminatory power for PIE. Based on both NRI and IDI models, the combination of MSE indices (wake: area1_5 and sleep: area6_20) and KWSE (m = 2, τ = 1, α = 0.16) with traditional HRV measures had greater discriminatory power than any of the single HRV measures. Significance: Impaired HRV and complexity were found in pre-school children with PIE. HRV, MSE, and KWSE could discriminate patients with PIE from subjects with normal cardiac complexity. These findings suggested that the MSE and KWSE methods may be helpful for assessing and understanding heart rate dynamics in younger children with epilepsy.

Tachyarrhythmias and neurologic complications

Tachyarrhythmias are abnormal heart rhythms with a ventricular rate of 100 or more beats per minute. These rhythms are classified as either narrow or wide-complex tachycardia with further subdivision into regular or irregular rhythm. Patients are frequently symptomatic presenting with palpitations, diaphoresis, dyspnea, chest pain, dizziness, and syncope. Sudden cardiac death may occur with certain arrhythmias. Recognizing tachyarrhythmia and understanding its management is important as a wide spectrum of neurologic complications have been associated with such arrhythmias. The purpose of this chapter is to provide a comprehensive overview on the neurologic complications of tachyarrhythmias, neurologic adverse events of antiarrhythmic interventions, and neurologic conditions that can precipitate tachyarrhythmia.

Outcome measures in pediatric polypharmacy research: a scoping review

INTRODUCTION

Various methods have been used to interpret the reports of pediatric polypharmacy across the literature. This is the first scoping review that explores outcome measures in pediatric polypharmacy research.

OBJECTIVES

The aim of our study was to describe outcome measures assessed in pediatric polypharmacy research.

METHODS

A search of electronic databases was conducted in July 2017, including Ovid Medline, PubMed, Elsevier Embase, Wiley Cochrane Central Register of Controlled Trials (CENTRAL), EBSCO CINAHL, Ovid PsyclNFO, Web of Science Core Collection, ProQuest Dissertations and Thesis A&I. Data were extracted about study characteristics and outcome measures, and also synthesized by harms or benefits mentioned.

RESULTS

The search strategy initially identified 8169 titles and screened 4398 using the inclusion criteria after de-duplicating. After the primary screening, a total of 363 studies were extracted for the data analysis. Polypharmacy (prevalence) was identified as an outcome in 31.4% of the studies, prognosis-related outcomes in 25.6%, and adverse drug reactions in 16.5%. A total of 265 articles (73.0%) mentioned harms, including adverse drug reactions (26.4%), side effects (24.2%), and drug-drug interactions (20.9%). A total of 83 studies (22.9%) mentioned any benefit, 48.2% of which identified combination for efficacy, 24.1% combination for treatment of complex diseases, and 19.3% combination for treatment augmentation. Thirty-eight studies reported adverse drug reaction as an outcome, where polypharmacy was a predictor, with various designs.

CONCLUSIONS

Most studies of pediatric polypharmacy evaluate prevalence, prognosis, or adverse drug reaction-related out-comes, and underscore harms related to polypharmacy. Clinicians should carefully weigh benefits and harms when introducing medications to treatment regimens.

Time, frequency and information domain analysis of short-term heart rate variability before and after focal and generalized seizures in epileptic children

OBJECTIVE

In this work we explore the potential of combining standard time and frequency domain indexes with novel information measures, to characterize pre- and post-ictal heart rate variability (HRV) in epileptic children, with the aim of differentiating focal and generalized epilepsy regarding the autonomic control mechanisms.

APPROACH

We analyze short-term HRV in 37 children suffering from generalized or focal epilepsy, monitored 10 s, 300 s, 600 s and 1800 s both before and after seizure episodes. Nine indexes are computed in time (mean, standard deviation of normal-to-normal intervals, root mean square of the successive differences (RMSSD)), frequency (low-to-high frequency power ratio LF/HF, normalized LF and HF power) and information (entropy, conditional entropy and self-entropy) domains. Focal and generalized epilepsy are compared through statistical analysis of the indexes and using linear discriminant analysis (LDA).

MAIN RESULTS

In children with focal epilepsy, early post-ictal phase is characterized by significant tachycardia, depressed HRV, increased LF power and LF/HF, and decreased complexity, progressively recovered across time windows after the episodes. Children with generalized seizures instead show significant tachycardia, lower RMSSD, higher LF power and LF/HF ratio before the seizure. These different behaviors are exploited by LDA analysis to separate focal and generalized epilepsy up to an accuracy of 75%. Results suggest a shift of the sympatho-vagal balance towards sympathetic dominance and vagal withdrawal, noticeable just after the termination of seizure episodes and then reverted in focal epilepsy, and persistent during inter-ictal and pre-ictal periods in generalized epilepsy.

SIGNIFICANCE

Our analysis helps in elucidating the pathophysiology of inter-ictal HRV autonomic control and the differential diagnosis of generalized and focal epilepsy. These findings may have clinical relevance since altered sympatho-vagal control can be related to a higher danger of morbidity and mortality, may reduce thresholds for life-threatening arrhythmias, and could be a biomarker of risk for sudden unexpected death in epilepsy.

The effect of unilateral stroke on autonomic function in the term newborn

BACKGROUND

The mature cerebral cortex has a topographically organized influence on reflex autonomic centers of the brainstem and diencephalon and sympathetic activation coming primarily from the right hemisphere and parasympathetic activation from the left. In the term newborn, the maturational status of this central autonomic system remains poorly understood.

METHODS

Sixteen term newborns admitted to Children's National with unilateral middle cerebral artery (MCA) strokes (n = 8 left, n = 8 right) had archived continuous electrocardiograph (EKG) signals available. We compared stroke laterality and severity with indices of autonomic function, as measured by heart rate variability. We performed both time- and frequency-domain analyses on the R-R interval (RRi) over 24h of continuous EKG data at around 7 days of age.

RESULTS

Right MCA stroke significantly increased sympathetic tone, while left MCA stroke increased parasympathetic tone. Regardless of laterality, stroke severity was associated inversely with sympathetic tone and positively with parasympathetic tone. Surprisingly, injury to either insular region had no significant autonomic effect. Phenobarbital blood levels were positively associated with sympathetic tone and inversely related to parasympathetic tone.

CONCLUSION

Based on these findings, it is difficult to reconcile the functional topography of the central autonomic system in term newborns with that currently proposed for the normal mature brain. Further investigation is clearly needed.

Analysis of tissue Doppler parameters and 24-hour heart rate variations in children with newly diagnosed untreated idiopathic epilepsy in interictal period

INTRODUCTION

Cardiac mortality has increased in patients with epilepsy. Although majority of cardiac autonomic and ventricular function abnormalities were detected in ictal and postictal period, interictal epileptogenic activity may induce the autonomic imbalance as well. In our study, we aimed to investigate the interictal, subclinical cardiac changes in terms of cardiac autonomic balance via 24-hour Holter electrocardiography (ECG) and ventricular functions by tissue Doppler echocardiography (TDI) in children with newly diagnosed untreated idiopathic epilepsy.

MATERIAL AND METHODS

Thirty children with newly diagnosed untreated idiopathic epilepsy (12 males, 18 females; mean age: 125.13 ± 35.2 months) (patient group) and 40 healthy, age and body mass index (BMI)-matched children (18 males, 22 females; mean age: 129.43 ± 38.5 months) (control group) were enrolled. Included patients underwent 24-hour Holter electrocardiographic and tissue Doppler echocardiographic study.

RESULTS

Time domain measures were found significantly lower in the patient group. Mean high frequency (HF) values were significantly lower, and mean low frequency (LF) and mean LF/HF parameters were significantly higher in the patient group. Mean isovolumetric contraction time (ICT), isovolumetric relaxation time (IRT), and myocardial performance index (MPI) values were significantly higher, and mean ejection time (ET) values were significantly lower among the patients with untreated idiopathic epilepsy.

CONCLUSION

We found that patients with untreated newly diagnosed epilepsy have a significant subclinical deterioration of left ventricular functions, and they also showed changes in heart rate variability (HRV) regarding the sympathovagal imbalance in interictal period. These findings can be related with increased cardiac mortality.

Heart rate variability measurement in epilepsy: How can we move from research to clinical practice?

Our objective was to critically evaluate the literature surrounding heart rate variability (HRV) in people with epilepsy and to make recommendations as to how future research could be directed to facilitate and accelerate integration into clinical practice. We reviewed relevant HRV publications including those involving human subjects with seizures. HRV has been studied in patients with epilepsy for more than 30 years and, overall, patients with epilepsy display altered interictal HRV, suggesting a shift in autonomic balance toward sympathetic dominance. This derangement appears more severe in those with temporal lobe epilepsy and drug-resistant epilepsy. Normal diurnal variation in HRV is also disturbed in at least some people with epilepsy, but this aspect has received less study. Some therapeutic interventions, including vagus nerve stimulation and antiepileptic medications, may partially normalize altered HRV, but studies in this area are sometimes contradictory. During seizures, the changes in HRV may be complex, but the general trend is toward a further increase in sympathetic overactivity. Research in HRV in people with epilepsy has been limited by inconsistent experimental protocols and studies that are often underpowered. HRV measurement has the potential to aid clinical epilepsy management in several possible ways. HRV may be useful in predicting which patients are likely to benefit from surgical interventions such as vagus nerve stimulation and focal cerebral resection. As well, HRV could eventually have utility as a biomarker of risk for sudden unexpected death in epilepsy (SUDEP). However, at present, the inconsistent measurement protocols used in research are hindering translation into clinical practice. A minimum protocol for HRV evaluation, to be used in all studies involving epilepsy patients, is necessary to eventually allow HRV to become a useful tool for clinicians. We propose a straightforward protocol, involving 5-minute measurements of root mean square of successive differences in wakefulness and light sleep.

Interictal electrocardiographic alternations in patients with drug-resistant epilepsy

PURPOSE

Previous studies suggested the possible role of autonomic dysfunction in sudden unexpected death in epilepsy (SUDEP). The aim of this study is to assess the interictal ECG alternations especially heart rate variability (HRV), as a marker of autonomic dysfunction, in patients with drug-resistant epilepsy and determine the effect of epilepsy type and duration, seizure frequency and anti-epileptic drugs (AEDs) on ECG findings.

METHODS

In this comparative cross-sectional study, the interictal ECG parameters of 64 consecutive patients with drug-resistant epilepsy and the same number of age and sex-matched controls were analyzed. Epilepsy type and duration, seizure frequency, MRI findings and patients' anti-convulsive medications were determined.

RESULTS

Our study showed significant longer mean PR interval, shorter mean QRS duration, shorter mean QTc interval and longer corrected QT interval dispersion (QTcd) in patients with epilepsy compared to healthy subjects. The analysis of RR intervals revealed reduced RR standard deviation (SDNN), which is a marker of reduced HRV. A positive linear correlation was found between QRS duration and epilepsy duration. No significant correlation was found between taking a certain kind of AED, and ECG alternations, except for mild QTcd prolongation in patients taking valproate.

CONCLUSION

Our study showed clinically important alternations in interictal ECG parameters in patients with drug-resistant epilepsy which could result in sudden cardiac death.

Effects of vagus nerve stimulation on heart rate variability in children with epilepsy

PURPOSE

The aim of this study was to evaluate the effects of vagus nerve stimulation (VNS) on heart rate variability (HRV) in children with epilepsy.

METHODS

The subgroups of HRV, namely time domain (Standard deviation of NN interval (SDNN), SDNN index, Standard deviation of the averages of NN intervals (SDANN), Root mean square of successive differences (RMMSD), Adjacent NN intervals differing by more than 50 ms in the entire recording divided by the total number of all NN intervals (PNN50), triangular index) and frequency domain (Low-frequency (LF), High-frequency (HF), LF/HF), were investigated in 20 pediatric patients before and after 6 and 12months of VNS treatment during day and night by comparing their data with those of 20 control subjects. In addition, subgroups of age, epilepsy duration and localization, and antiepileptic drugs (AEDs) were also evaluated if they had further effects on basal HRV levels.

RESULTS

Increased heart rates (HRs); decreased SDNN, SDANN, RMMSD, and PNN50; and increased LF/HF ratios were identified before VNS therapy (p<0.05). Even though remarkable improvement was seen after 6months of VNS treatment (p<0.05), no further changes were observed in 12-month compared with 6-month levels (p>0.05) in all parameters, still even significantly lower than those of controls (p<0.05). Longer duration of epilepsy and localization of epileptic focus, such as in the temporal lobe, were also found to further contribute to diminished basal HRV levels (p<0.05).

CONCLUSION

The cardiovascular system is under deep sympathetic influence in children with epilepsy. Although VNS seems to provide a substantial improvement by achieving increased parasympathetic effects in short-term therapy, the levels were still lower than those of healthy children after either short- or long-term therapy. Therefore, impaired cardiovascular autonomic regulation may be associated with the epileptic process itself as well as with the contribution of some additional factors. Overall, different aspects such as age, epilepsy duration, epileptic focus, seizure frequency, and AEDs should also be considered for their further possible effects on HRV during VNS therapy.

Comparison of Autonomic Function before and after Surgical Intervention in Patients with Temporal Lobe Epilepsy

Background and Purpose

Refractory temporal lobe epilepsy (TLE) is commonly associated with imbalances in cardiovascular (CV) parasympathetic and sympathetic functions, which are treated using TLE surgery. We investigated the effect of hemispheric lateralization of seizure foci on autonomic CV functions before and after TLE surgery.

Methods

The study was conducted on patients with left TLE (LTLE, n = 23) and right TLE (RTLE, n = 30) undergoing unilateral TLE surgery. To assess the autonomic CV functions, changes in the heart rate (ΔHR) and blood pressure (BP) were measured using a standardized battery of autonomic reactivity tests before surgery and at 3 and 6 months after surgery.

Results

Before surgery, ΔHR and the expiration to inspiration ratio (E:I) during the deep breathing test were higher in the LTLE group than in the RTLE group (both p < 0.001), but both outcomes were comparable between the groups at 3 and 6 months. ΔHR decreased at 3 and 6 months (p < 0.001 and 0.01, respectively) compared with preoperative values. The E:I at 3 months in the LTLE group was lower (p = 0.04) than the preoperative values. Decrease in systolic BP during the head-up tilt test was greater in the LTLE group than in the RTLE group (p = 0.002) before surgery. The maximum increase in diastolic BP during the cold pressor test was lower in the RTLE group at 6 months than that before surgery (p = 0.001) and in the LTLE group (p = 0.002).

Conclusions

We found that hemispheric lateralization of seizure foci in the temporal lobe had a differential effect on autonomic CV functions before surgery. Before surgery, parasympathetic reactivity was higher in the LTLE group, and sympathetic reactivity was higher in the RTLE group. After surgery, autonomic CV functions were comparable between the groups, suggesting that TLE surgery stabilizes autonomic CV functions.

Interictal cardiac autonomic nervous system disturbances in dogs with idiopathic epilepsy

Autonomic nervous system (ANS) activity in the interictal period (InIp) in dogs with presumed idiopathic epilepsy (pIE) was assessed using heart rate variability (HRV) analysis. The HRVs obtained from 28 pIE dogs with interictal epileptic discharges (InIEd; 11 with treatment and 17 without treatment) detected on electroencephalography (EEG) were compared with those obtained from 13 healthy dogs. On electrocardiographic (ECG) study, the P wave dispersion (PWD; P<0.001), P max (P=0.004) and corrected QT interval (QTc; P=0.025) were significantly increased in the pIE group. On the basis of HRV analysis, the pIE dogs had an increased activity of the parasympathetic component of the ANS, including the percentage of R-R interval (pNN50%) that differs more than 50ms (P=0.011) and high frequency band (HF; P=0.041). Administration of phenobarbitone had no influence on the ANS pattern when pIE subgroups were compared (P>0.05). In InIp, dogs elicited specific conductibility delays of the electrical impulses (increased PWD and QTc interval); these delays are considered to be risk factors for developing severe arrhythmias, such as atrial fibrillation and ventricular tachycardia. When compared with human beings, a different ANS pattern characterised by increased parasympathetic activity was observed, which may influence the therapeutic approach of IE in dogs.

Autonomic function in reflex and non-reflex epilepsy--an exploratory study

PURPOSE

Seizures are known to affect diverse areas of the Central Autonomic Network (CAN) resulting in varied autonomic symptoms. The objectives of the study were to characterize neuro-cardiac autonomic regulation in hot water epilepsy (HWE) with or without spontaneous seizure, and to analyze the effect of Carbamazepine (CBZ).

METHODS

Seventy patients of HWE [42 drug-naïve 'HWE only' and 28 'HWE with spontaneous complex partial seizure (CPS),' on CBZ] and 40 spontaneous CPS on CBZ were recruited after informed consent. Fifty healthy volunteers served as control. Conventional cardiac autonomic function tests, Heart Rate Variability (HRV), Blood Pressure Variability (BPV), and baroreflex sensitivity (BRS) were performed.

RESULTS

Significant dysfunction was evidenced in most of the autonomic function parameters in all the epilepsy subgroups when compared with controls. Significant reduction in the parasympathetic activity in HWE patients was observed. Significant impairment of short-term fluctuation of blood pressure in 'HWE with spontaneous CPS' compared to 'healthy volunteers' was detected. Compared to 'HWE only', 'HWE with spontaneous CPS' showed impaired sympathovagal balance. The BRS were also altered in 'HWE with spontaneous CPS' compared to 'HWE only'. The comparison of 'spontaneous CPS' with 'HWE with spontaneous CPS' and 'HWE only' showed reduced parasympathetic and sympathetic activities.

CONCLUSION

Both cardiovascular reflexes and autonomic cardiovascular regulation were altered in HWE, more so in 'HWE with spontaneous seizures'. Compared to those on CBZ, drug naïve had severe effect on vagal tone and CBZ did not alter cardiac autonomic functions in reflex as well as in non-reflex epilepsies.

Cardiac autonomic balance in children with epilepsy: value of antiepileptic drugs

BACKGROUND

Dysfunction of the autonomous nervous system causes arrhythmias and, although previous studies have investigated the effects of epilepsy on the autonomic control of the heart, there is still uncertainty about whether imbalance of sympathetic, vagal, or both systems occurs in epilepsy as well as the effect of anticonvulsants on the autonomic system.

AIM

To evaluate cardiac autonomic status in children with epilepsy on antiepileptic drugs.

PATIENTS AND METHODS

Sixty patients with epilepsy were recruited from the Outpatient Neurology Clinic at Ain Shams University and were divided into the following groups: group I, drug naive; and group II, patients with epilepsy on regular antiepileptic drugs. The second group was further subdivided into the following groups: group IIa, received monotherapy; and group IIb, received polytherapy. Forty age- and sex-matched healthy children served as controls. Included patients underwent videorecorded electroencephalograph, Holter electrocardiogram (EKG) for time and frequency domains of heart rate variability, and standard EKG recording for QTc, QTd.

RESULTS

Mean values of all time domain, total power, and high-frequency power were significantly lower, whereas low-frequency and low-frequency/high-frequency power, QTc. and QTd were significantly higher in group I compared with group II and in patients compared with controls. No significant difference was found between patients on different antiepileptic drug regimens regarding heart rate variability values. A significant negative correlation was found between Chalfont severity score and 50% of difference between adjacent, normal RR intervals in patient groups.

CONCLUSIONS

Children with epilepsy have cardiac autonomic dysfunction evident in their heart rate variability assessment. Patients on antiepileptic drugs had better autonomic balance than those not on antiepileptic drugs. Holter and EKG follow-up should be considered for early detection in those at high-risk cardiac complications.

Heart rate variability in infants with West syndrome

PURPOSE

West syndrome (WS) is a severe age-related acute epileptic encephalopathy of infancy characterized by infantile spasms, hypsarrhythmia and psychomotor delay. The aim of this study was to investigate if patients with WS had an altered autonomic output to the heart.

METHODS

In 23 patients with WS the heart rate variability (HRV) was investigated by examining time- and frequency-domain parameters of HRV at the time of the diagnosis of hypsarrhythmia and compared to 22 age-matched controls. For the WS patients the same dataset was obtained and compared again at the end of the study period, when hypsarrhythmia was no longer present.

RESULTS

Compared to controls, patients with WS during hypsarrhythmia had significantly lower SDNN (the standard deviation of the NN interval, i.e. the square root of variance) (19.2 ms; p = 0.007, Mann-Whitney's U-Test) and total power (242 ms(2); p = 0.044, Mann-Whitney's U-Test) in the awake state, indicating an abnormal autonomic output to the heart. Comparing the initial to the final examination demonstrated a significant increase in the HRV parameters SDNN (31.3 ms) and total power (757 ms(2); p = 0.001 and p = 0.013, Wilcoxon Signed Ranked Test). In addition, at the final examination the WS-patients no longer differed significantly from the controls.

CONCLUSION

Our data suggest that the initial reduction in HRV in patients at the time of onset of WS is transient and related to the presence of hypsarrhythmia.

Vagus nerve stimulation reduces cardiac electrical instability assessed by quantitative T-wave alternans analysis in patients with drug-resistant focal epilepsy

OBJECTIVE

The cardiac component of risk for sudden unexpected death in epilepsy (SUDEP) and alterations in cardiac risk by vagus nerve stimulation (VNS) are not well understood. We determined changes in T-wave alternans (TWA), a proven noninvasive marker of risk for sudden cardiac death in patients with cardiovascular disease, and heart rate variability (HRV), an indicator of autonomic function, in association with VNS in patients with drug-resistant focal epilepsy.

METHODS

Ambulatory 24-h electrocardiograms (N = 9: ages 29-63, six males) were analyzed.

RESULTS

Mean TWA during the interictal period was 37 ± 3.1 μV (mean ± SEM) in lead V1 for nine patients monitored following implantation of the VNS system (n = 7) or battery change (n = 2). Of these, six patients also monitored prior to implantation (n = 5) or battery change (n = 1) showed abnormally high TWA levels pre-VNS (60.0 ± 4.3 μV), which were significantly reduced by 24.3 μV (to 35.7 ± 4.8 μV, p = 0.02) after VNS settings were adjusted for desired clinical response. TWA in four (67%) of the six patients was reduced in association with VNS to levels below the 47-μV cut point of abnormality. The decrease in TWA was correlated with VNS intensity (r = 0.88, p < 0.02). In addition, low-frequency HRV was reduced by 60% (805.61 ± 253.96 to 323.49 ± 102.74 msec(2) , p = 0.05) and low-to high-frequency HRV ratio by 32% (3.34 ± 0.57 to 2.26 ± 0.31, p = 0.025), indicating a change in autonomic balance in favor of parasympathetic dominance.

SIGNIFICANCE

This is the first report that elevated levels of TWA in patients with drug-refractory partial-onset seizures were reduced in association with VNS, potentially by improving sympathetic/parasympathetic balance. VNS may have a cardioprotective role at stimulation settings typically used for seizure control. These findings indicate the utility of TWA for tracking improvement in cardiac status in this population.

Cardiac phenomena during kainic-acid induced epilepsy and lamotrigine antiepileptic therapy

RATIONALE

Pathologic ECG events are known to accompany seizures and to persist in several chronic epilepsy syndromes. The contribution of antiepileptic drugs (AEDs) to these events and the implications in the etiology of sudden-unexpected death in epilepsy (SUDEP) continue to be a matter of debate. We therefore investigated cardiac parameters during kainic-acid (KA) induced experimental epilepsy and antiepileptic treatment with lamotrigine (LTG).

METHODS

Epilepsy was induced in seven C57Bl/6 mice by injections of KA (20 mg/kg) on days 1 and 5, which produced severe acute seizures and spontaneous seizures 10 days later. Treatment with LTG (30 mg/kg) was initiated on day 11 and repeated on day 12. Continuous ECGs and ECoGs were collected telemetrically from freely moving mice.

RESULTS

Mice displayed pre-ictal but not ictal tachycardia. The squared coefficient of variation (SCV) of R-R intervals was significantly elevated 30s before and during seizures compared to control conditions. LTG produced a significant reversible increase in SCV and LF/HF ratio during slow-wave sleep (SWS), potentially indicative of sympatho-vagal imbalance during this state of vigilance, in which epileptic patients are known to be particularly vulnerable to SUDEP.

SIGNIFICANCE

The KA model used in this study permits the investigation of cardiac phenomena during epilepsy, as it features many effects found in human epileptic patients. Increased LF/HF, a known risk factor for cardiac disease, which is often found in epileptic patients, was observed as a side-effect of LTG treatment during SWS, suggesting that LTG may promote imbalance of the autonomous nervous system in epileptic mice.

Effect of antiepilepsy drug therapy on ventricular function in children with epilepsy: a tissue Doppler imaging study

Impaired cardiac myocardial function may contribute to the risk for sudden unexpected death of a patient with epilepsy. This study aimed to investigate the effect of antiepilepsy drugs (AEDs) on cardiac function in pediatric epileptic patients using standard and tissue Doppler imaging (TDI) echocardiography. This hospital-based, prospective cross-sectional study investigated 52 epileptic children (mean age 9.3 ± 3.1 years) treated with AEDs (duration 2.4-10.0 years) and 36 healthy children (mean age 9.5 ± 4.0 years). In the epilepsy group, standard echocardiography showed increased left ventricular (LV) end-diastolic and end-systolic diameters, an increased LV mass index, and preserved ejection fraction. The patients also exhibited increased mitral peak A-wave velocity and mitral E-wave deceleration time as well as a decreased mitral E/A ratio. The E/Em ratio was significantly higher in the epilepsy group (5.6 ± 1.2) than in the control group (5.2 ± 1.1) (p = 0.016). In the epilepsy group, TDI showed an increased isovolumetric relaxation time and myocardial performance index (MPI). It also exhibited decreased early diastolic velocity (Em) and a decreased mitral annular displacement index in these patients. There were positive correlations between the LV lateral wall MPI (r = 0.231), septal MPI (r = 0.223), and LV mass index (p < 0.05) but no correlation with the duration of AED treatment. The authors detected subclinical ventricular dysfunction associated with AEDs at a preclinical stage. They suggest that TDI can be useful for determining the short- and long-term cardiac effects of AEDs.

[Heart rate variability during sleep in children with multiple disabilities]

OBJECTIVES

To study heart rate variability during sleep in children with multiple disabilities in order to observe the behavior of the autonomic nervous system.

METHODS

The R-R interval variability of 4 to 12 years old children was recorded with a heart rate monitor during one night. Children with multiple disabilities (G1) and healthy children (G2) were compared in time, frequency, and non-linear domains.

RESULTS

Temporal (P<0.01), frequency (P<0.05), and non-linear (P<0.01) variables in the G1 were lower than in the G2 group.

DISCUSSION

The time and frequency analysis confirmed the predominance of the sympathetic nervous system during sleep in G1 children. Reduced non-linear variables can explain sleep with less informations (correlation dimension: 2.203 ± 1.239 versus 3.842 ± 0.378; P<0.001), less complex cycles of sleep (approximate entropy: 1.153 ± 0.200 versus 1.365 ± 0.099; P<0.01), and a reduced correlation in short-term variability (SD1: 42.37 ± 19.0 (ms) versus 73.44 ± 25.3; P<0.01). The fractal structure of the recordings was not affected (P>0.05). The diseases encountered are probably the reason for these findings, but the variety of disorders and medications of the children with multiple disabilities needs to be studied with a larger and more varied sample.

CONCLUSION

Sympathetic predominance during sleep in children with multiple disabilities is associated with a decrease in adaptive abilities of these children's autonomic nervous system.

Heart rate variability in children with tricyclic antidepressant intoxication

The aim of this study was to evaluate HRV in children requiring intensive care unit stays due to TCA poisoning between March 2009 and July 2010. In the time-domain nonspectral evaluation, the SDNN (P < 0.001), SDNNi (P < 0.05), RMSDD (P < 0.01), and pNN50 (P < 0.01) were found to be significantly lower in the TCA intoxication group. The spectral analysis of the data recorded during the first 5 minutes after intensive care unit admission showed that the values of the nLF (P < 0.05) and the LF/HF ratio (P = 0.001) were significantly higher in the TCA intoxication group, while the nHF (P = 0.001) values were significantly lower. The frequency-domain spectral analysis of the data recorded during the last 5 minutes showed a lower nHF (P = 0.001) in the TCA intoxication group than in the controls, and the LF/HF ratio was significantly higher (P < 0.05) in the intoxication group. The LF/HF ratio was higher in the seven children with seizures (P < 0.001). These findings provided us with a starting point for the value of HRV analysis in determining the risk of arrhythmia and convulsion in TCA poisoning patients. HRV can be used as a noninvasive testing method in determining the treatment and prognosis of TCA poisoning patients.

Cardiac manifestations of neurologic disorders

The cardiac complications of certain neurologic diseases have been well recognized for over 50 years and are mostly evident for cerebrovascular accidents. Although these complications are frequent and in most circumstances benign, detrimental cardiac side effects, such as serious arrhythmias and myocardial infarctions, may occur. The link to most of these cardiac derangements is a transient or chronic autonomic dysfunction, depending on the specific neurologic disease. Myocardial infarcts, left ventricular dysfunction, and arrhythmias are well-recognized complications of subarachnoid hemorrhage, intracranial bleed, and ischemic strokes. Seizures may present with atonia or sudden death from asystole. Degenerative brain disorders, namely the synucleinopathies, may affect the central control areas or peripheral ganglia of the autonomic nervous system, causing autonomic dysfunction. In addition, cardiac conduction defects and cardiomyopathy are common in certain neuromuscular disorders, namely the dystrophies and mitochondrial myopathies.

A systematic review and meta-analysis of heart rate variability in epilepsy and antiepileptic drugs

PURPOSE

Epilepsy is associated with near-fatal and fatal arrhythmias, and sudden unexpected death in epilepsy (SUDEP) is partly related to cardiac events. Dysfunction of the autonomous nervous system causes arrhythmias and, although previous studies have investigated the effects of epilepsy on the autonomic control of the heart, the results are still mixed regarding whether imbalance of sympathetic, vagal, or both systems is present in epilepsy, and also the importance of anticonvulsant treatment on the autonomic system. Therefore, we aimed to investigate epilepsy and its treatment impact on heart rate variability (HRV), assessed by sympathetic and parasympathetic activity expressed as low-frequency (LF) and high-frequency (HF) power spectrum, respectively.

METHOD

We performed a systematic review from the first date available to July 2011 in Medline and other databases; key search terms were "epilepsy"; "anticonvulsants"; "heart rate variability"; "vagal"; and "autonomous nervous system." Original studies that reported data and/or statistics of at least one HRV value were included, with data being extracted by two independent authors. We used a random-effects model with Hedges's g as the measurement of effect size to perform two main meta-analyses comparing LF and HF HRV values in (1) epilepsy patients versus controls; (2) patients receiving versus not receiving treatment; and (3) well-controlled versus refractory patients. Secondary analyses assessed other time- and frequency-domain measurements (nonlinear methods were not analyzed due to lack of sufficient data sets). Quality assessment of each study was verified and also meta-analytic techniques to identify and control bias. Meta-regression for age and gender was performed.

KEY FINDINGS

Initially, 366 references were identified. According to our eligibility criteria, 30 references (39 studies) were included in our analysis. Regarding HF, epilepsy patients presented lower values (g -0.69) than controls, with the 95% confidence interval (CI) ranging from -1.05 to -0.33. No significant differences were observed for LF (g -0.18; 95% CI -0.71 to 0.35). Patients receiving treatment presented HF values to those not receiving treatment (g -0.05; 95% CI -0.37 to 0.27), with a trend for having higher LF values (g 0.1; 95% CI -0.13 to 0.33), which was more pronounced in those receiving antiepileptic drugs (vs. vagus nerve stimulation). No differences were observed for well-controlled versus refractory patients, possibly due to the low number of studies. Regression for age and gender did not influence the results. Finally, secondary time-domain analyses also showed lower HRV and lower vagal activity in patients with epilepsy, as shown by the standard deviation of normal-to-normal interval (SDNN) and the root mean square of successive differences (RMSSD) indexes, respectively.

SIGNIFICANCE

We confirmed and extended the hypothesis of sympathovagal imbalance in epilepsy, as showed by lower HF, SDNN, and RMSSD values when compared to controls. In addition, there was a trend for higher LF values in patients receiving pharmacotherapy. As lower vagal (HF) and higher sympathetic (LF) tone are predictors of morbidity and mortality in cardiovascular samples, our findings highlight the importance of investigating autonomic function in patients with epilepsy in clinical practice. Assessing HRV might also be useful when planning therapeutic interventions, as some antiepileptic drugs can show hazardous effects in cardiac excitability, potentially leading to cardiac arrhythmia.

Autonomic effects of refractory epilepsy on heart rate variability in children: influence of intermittent vagus nerve stimulation

AIM

Vagus nerve stimulation (VNS) is a therapeutic option for individuals with refractory epilepsy. Individuals with refractory epilepsy are prone to dysfunction of the autonomic nervous system. Reduced heart rate variability is a marker of dysfunction of the autonomic nervous system. Our goal was to study heart rate variability in children with refractory epilepsy and the influence of VNS on this parameter.

METHODS

In 17 children (13 male; four female; mean age 7 y 6 mo; age range 3-16 y) with refractory epilepsy, electroencephalographic and electrocardiographic data were obtained before and after implantation of VNS during stage 2 and slow-wave sleep. Time and frequency domain parameters were calculated and the results were compared with an age- and sex-matched group of individuals without refractory epilepsy.

RESULTS

Our results show that autonomic cardiac control is affected in individuals with refractory epilepsy. There is a striking reduction in vagal tone during slow-wave sleep and modulation capacity is smaller than in individuals without refractory epilepsy. Implantation of VNS induces a shift in sympathovagal balance towards sympathetic predominance and an improvement in autonomic modulation.

INTERPRETATION

Heart rate variability is affected in children with refractory epilepsy, and changes after implantation of VNS. The observed changes could be of importance in the cardiac complications of individuals with epilepsy and should be explored in more detail.

Electrical and autonomic cardiac function in patients with Dravet syndrome

Dravet syndrome (DS) is an epileptic encephalopathy related mainly to mutations in the SCN1A gene, encoding for neuronal sodium channels. Patients with DS have a high risk of sudden unexpected death in epilepsy (SUDEP). In this study we investigated whether patients with DS present abnormalities in electrical and autonomic cardiac function. To this aim we assessed ventricular repolarization and heart rate variability (HRV) on standard electrocardiography (ECG) and on 24-h ECG Holter monitoring, respectively, in 20 patients affected by DS (6.8 ± 4 years, 11 female). As age- and sex-matched control groups, we also studied 20 patients with other epileptic syndromes receiving antiepileptic drugs (ES/AED, 6.0 ± 5 years, 12 female), 20 patients with other epileptic syndromes without treatment (ES/no-AED, 6.7 ± 4 years, 10 female), and 20 healthy children (HC, 7.2 ± 5 years, 11 females). Data analysis showed that patients with DS had depressed HRV variables compared to both ES patients (ES/AED and ES/no-AED) and HC control group, whereas no significant differences in HRV variables were found between ES patients (with and without treatment) and HC. There was no significant difference between patients with DS and all the other control groups in RR intervals, QT, and QTc interval analysis. In conclusion, DS patients display an imbalance of cardiac autonomic function toward a relative predominance of adrenergic tone compared to both healthy children and patients with other forms of epilepsy, independent of antiepileptic therapy. Follow-up studies should clarify the clinical significance of this autonomic impairment and whether HRV analysis can be helpful in predicting the risk of sudden death in patients with DS.

Severe valproic acid intoxication: case study on the unbound fraction and the applicability of extracorporeal elimination

Among anticonvulsants, valproic acid (VPA) is cited as the most frequent cause of unintentional and intentional intoxications. Symptoms of VPA intoxication are diverse and are related to VPA plasma concentration. Although total plasma concentrations of less than 450 mg/l produce limited toxicity, severe intoxications (>850 mg/l) can induce coma and are ultimately life threatening. A 32-year-old comatose woman was admitted to the ICU at our hospital; she suffered from hypotension, respiratory depression, hypoglycaemia, sinus bradycardia, hyperammonaemia, metabolic acidosis, and her core body temperature was 33.7 degrees C. The total VPA plasma concentration was 1244 mg/l with an increased unbound fraction of 85%. After we administered multiple doses of activated charcoal, she underwent continuous veno-venous haemofiltration to reduce the plasma VPA concentration. As the total concentration decreased, the unbound fraction also decreased. Within 20 h of admission, the patient made a full recovery. In cases of VPA intoxication, protein-binding saturation and drug characteristics render extracorporeal elimination, an effective technique for eliminating the unbound drug. Its application should be considered, depending on clinical symptoms, VPA concentration (>300 mg/l), albumin concentration and ammonia concentration (>400 micromol/l). The application of this technique should be weighed against its risks. This case illustrates the clinical significance of applying continuous veno-venous haemofiltration in VPA intoxication because of protein-binding saturation, and suggests when extracorporeal elimination should be considered.

Cardiac changes in epilepsy

Epilepsy and seizures can have a dramatic effect on the autonomic nervous system by involvement of the central autonomic control centers. The peri-ictal changes can lead to short-term alteration of cardiac functions in patients with seizures, and are partially hemispheric specific. Changes in heart rhythm, conduction and even subtle signs of ischemia have been reported. Ictal asystole and the lock-step phenomenon during seizures play an important role in the pathophysiology of SUDEP. In patients with longlasting epilepsy and multiple seizures, there are now convincing arguments for a chronic dysfunction of the autonomic nervous system. In this sense, heart rate variability can be considered as a biomarker of autonomic dysfunction in epilepsy. Early recognition of these short- and long-term cardiac effects will become useful in predicting seizures and in guiding more individualized treatment in the near future.