Changes in arrhythmia profile and heart rate variability during abrupt withdrawal of antiepileptic drugs. Implications for sudden death

Exercise-induced central and peripheral sympathetic activity in a community-based group of epilepsy patients differ from healthy controls

Ictal and interictal activity within the autonomic nervous system is characterized by a sympathetic overshoot in people with epilepsy. This autonomic dysfunction is assumed to be driven by alterations in the central autonomic network. In this study, exercise-induced changes of the interrelation of central and peripheral autonomic activity in patients with epilepsy was assessed. 21 patients with epilepsy (16 seizure-free), and 21 healthy matched controls performed an exhaustive bicycle ergometer test. Immediately before and after the exercise test, resting state electroencephalography measurements (Brain Products GmbH, 128-channel actiCHamp) of 5 min were carried out to investigate functional connectivity assessed by phase locking value in source space for whole brain, central autonomic network and visual network. Additionally, 1-lead ECG (Brain products GmbH) was performed to analyze parasympathetic (root mean square of successive differences (RMSSD) of the heart rate variability) and sympathetic activity (electrodermal activity (meanEDA)). MeanEDA increased (p < 0.001) and RMSSD decreased (p < 0.001) from pre to post-exercise in both groups. Correlation coefficients of meanEDA and central autonomic network functional connectivity differed significantly between the groups (p = 0.004) after exercise. Both patients with epilepsy and normal control subjects revealed the expected physiological peripheral autonomic responses to acute exhaustive exercise, but alterations of the correlation between central autonomic and peripheral sympathetic activity may indicate a different sympathetic reactivity after exercise in patients with epilepsy. The clinical relevance of this finding and its modulators (seizures, anti-seizure medication, etc.) still needs to be elucidated.

Cardiac arrhythmia and epilepsy genetic variants in sudden unexpected death in epilepsy

Introduction

Sudden Unexpected Death in Epilepsy (SUDEP) is the leading epilepsy-related cause of death, affecting approximately 1 per 1,000 individuals with epilepsy per year. Genetic variants that affect autonomic function, such as genes associated with cardiac arrhythmias, may predispose people with epilepsy to greater risk of both sudden cardiac death and SUDEP. Advances in next generation sequencing allow for the exploration of gene variants as potential biomarkers.

Methods

Genetic testing for the presence of cardiac arrhythmia and epilepsy gene variants was performed via genetic panels in 39 cases of SUDEP identified via autopsy by the Ontario Forensic Pathology Service. Variants were summarized by in-silico evidence for pathogenicity from 4 algorithms (SIFT, PolyPhen-2, PROVEAN, Mutation Taster) and allele frequencies in the general population (GnomAD). A maximum credible population allele frequency of 0.00004 was calculated based on epilepsy prevalence and SUDEP incidence to assess whether a variant was compatible with a pathogenic interpretation.

Results

Median age at the time of death was 33.3 years (range: 2, 60). Fifty-nine percent (n=23) were male. Gene panels detected 62 unique variants in 45 genes: 19 on the arrhythmia panel and 26 on the epilepsy panel. At least one variant was identified in 28 (72%) of decedents. Missense mutations comprised 57 (92%) of the observed variants. At least three in silico models predicted 12 (46%) cardiac arrhythmia panel missense variants and 20 (65%) epilepsy panel missense variants were pathogenic. Population allele frequencies were <0.00004 for 11 (42%) of the cardiac variants and 10 (32%) of the epilepsy variants. Together, these metrics identified 13 SUDEP variants of interest.

Discussion

Nearly three-quarters of decedents in this SUDEP cohort carried variants in comprehensive epilepsy or cardiac arrhythmia gene panels, with more than a third having variants in both panels. The proportion of decedents with cardiac variants aligns with recent studies of the disproportionate cardiac burden the epilepsy community faces compared to the general population and suggests a possible cardiac contribution to epilepsy mortality. These results identified 13 priority targets for future functional studies of these genes potential role in sudden death and demonstrates the necessity for further exploration of potential genetic contributions to SUDEP.

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.

Fitness, performance, and cardiac autonomic responses to exercise in people with epilepsy

People with epilepsy (PWE) are less fit and have an increased risk of sudden cardiac death. Imbalances within the autonomic nervous system (ANS) are believed to mediate some of those effects. However, results are mostly derived from patients whose seizures are refractory to medical therapy. In this study, an exhaustive bicycle ergometer test was delivered to 25 PWE (19 seizure free in the last 6 months) recruited in a community-based setting and 25 age-, sex-, and BMI-matched healthy controls. During the exercise test a 12-channel ECG was recorded and spirometry was carried out to determine the maximal oxygen uptake (VO₂peak) as the gold standard to assess fitness. Before and after exercise, heart rate variability (HRV) and electrodermal activity (EDA) were measured along with an electroencephalogram (EEG). Blood samples were collected to determine anti-seizure drug (ASD) serum levels and physical activity of daily living was evaluated via the International Physical Activity Questionnaire (IPAQ). People with epilepsy and healthy controls were similarly fit and physically active. However, PWE had a lower maximum heart rate, a lower heart rate reserve, and a lower chronotropic index. The ratio between low- to high-frequency HRV changes (LF/HF ratio) was lower in PWE. Two patients with idiopathic genetic epilepsies revealed generalized interictal epileptiform discharges only after, but not before exercise. However, post-exercise EEG measurement was three times longer than pre-exercise and those patients did not report exercise induced seizures in the history. Besides epileptogenesis, anti-seizure medications may also contribute to those autonomic differences.

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.

Interictal autonomic changes in persons with epilepsy (PWE) on carbamazepine (CBZ) versus other anti-seizure drug monotherapy: A cross-sectional study

OBJECTIVE

Epilepsy is one of the most prevalent neurological conditions and carbamazepine is a commonly used anti-seizure drug (ASD), especially in developing nations. There are reports of carbamazepine causing atrioventricular conduction defects and autonomic dysfunctions and its implication in Sudden Unexpected Death in Epilepsy (SUDEP) is controversial. We planned this study to assess the effect of carbamazepine (CBZ) on autonomic function compared to other ASDs in persons with epilepsy.

METHODS

In this cross-sectional study, we assessed the sympathetic and parasympathetic autonomic functions in persons with epilepsy (PWE) on CBZ versus other anti-seizure monotherapy using tests of heart rate variability including its time-, frequency- and non-linear domains, heart rate response to deep breathing, valsalva maneuver, and blood pressure response to isometric handgrip.

RESULTS

Persons with epilepsy on CBZ monotherapy did not show a significant reduction in the time domain parameter SDRR compared to other ASDs used as monotherapy (mean ± SD, 38.04 ± 18.75 ms vs 44.37 ± 20.35 ms; p = 0.125). However, PWE on CBZ had significantly lower time-domain measurements including RMSSD (mean ± SD 31.95 ± 17.29 ms vs 42.02 ± 22.29 ms; p = 0.018), SDSD (mean ± SD 31.91 ± 17.26 ms vs 41.96 ± 22.27 ms; p 0.018), and pNN50 [median (IQR) 05.45(0.69-25.37) vs 16.38(2.32-36.83); p = 0.030]. Frequency domain measures of HRV, heart rate responses to deep breathing, valsalva maneuver and tilt-testing and BP responses to valsalva and tilt-testing were not significantly different between the groups.

CONCLUSION

The findings of our study indicate reduced parasympathetic activity in persons on CBZ monotherapy compared to other ASDs, which may pose risk of SUDEP. Carbamazepine may thus be avoided in those at risk of autonomic dysfunction and SUDEP.

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.

Simultaneous electrocardiogram during routine electroencephalogram: arrhythmia rates through the eyes of the cardiologist

BACKGROUND

The importance of simultaneous 2-lead electrocardiogram (ECG) recording during routine electroencephalogram (EEG) has been reported several times on clinical grounds.

OBJECTIVE

To investigate arrhythmia rates detected by simultaneous 2-lead ECG in our patient sample undergoing routine EEG. Remarkably, we sought to assess the possible expansion of results with a more experienced interpretation of simultaneous ECG.

METHODS

Simultaneous 2-lead ECG recordings during routine EEG, performed between January and March, 2016, have been retrospectively analyzed by a cardiology specialist. In addition, EEG reports were screened with the keywords 'arrhythmia, tachycardia, bradycardia, atrial fibrillation, extrasystole' to evaluate the neurologist interpretation.

RESULTS

Overall, 478 routine EEG recordings were scanned. The mean age of the patients was 42.8±19.8 (16-95), with a sex ratio of 264/214 (F/M). In 80 (17%) patients, findings compatible with arrhythmia were identified on simultaneous ECG after a cardiologist's evaluation. The detected arrhythmia subtypes were: ventricular extrasystole (n=27; 5.6%), supraventricular extrasystole (n=23; 4.8%), tachycardia (n=9; 1.8%), prolonged QRS duration (n=7; 8.7%), atrial fibrillation (n=6; 1.2%), and block (n=6; 1.2%). On the other hand, keywords related to arrhythmia were present in 45 (9.4%) of EEG reports. The reported statements were tachycardia (3.3%), arrhythmia (2.5%), bradycardia (2.1%), and extrasystole (1.5%).

CONCLUSIONS

A considerably high rate of arrhythmia cases was determined on simultaneous ECG during routine EEG after being interpreted by a cardiologist. However, the screening results of EEG reports revealed relatively low arrhythmia rates. These results suggest that the detection rates of ECG abnormalities during routine EEG may be potentially improved.

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.

Ictal Cardiac Ryhthym Abnormalities

Cardiac rhythm abnormalities in the context of epilepsy are a well-known phenomenon. However, they are under-recognized and often missed. The pathophysiology of these events is unclear. Bradycardia and asystole are preceded by seizure onset suggesting ictal propagation into the cortex impacting cardiac autonomic function, and the insula and amygdala being possible culprits. Sudden unexpected death in epilepsy (SUDEP) refers to the unanticipated death of a patient with epilepsy not related to status epilepticus, trauma, drowning, or suicide. Frequent refractory generalized tonic-clonic seizures, anti-epileptic polytherapy, and prolonged duration of epilepsy are some of the commonly identified risk factors for SUDEP. However, the most consistent risk factor out of these is an increased frequency of generalized tonic–clonic seizures (GTC). Prevention of SUDEP is extremely important in patients with chronic, generalized epilepsy. Since increased frequency of GTCS is the most consistently reported risk factor for SUDEP, effective seizure control is the most important preventive strategy.

[Current possibilities of treatment of generalized convulsive seizures]

Current possibilities of treatment of generalized convulsive seizures are presented. Progress in the field of pharmacotherapy of epilepsy allowed to introduce new antiepileptic drugs (AED). Some of them are modified AED with higher efficacy or better tolerability and others represent a generation of new drugs with different mechanisms of action. Perampanel, an agonist of AMPA-receptors, is a new drug approved in more than 40 countries, including Russia. At present, the use of some AED is limited by the high risk of sudden death (sudden unexpected death in epilepsy (SUDEP)). SUDEP is a common cause of death directly associated with epilepsy, with the highest frequency in patients with active epilepsy. Subtherapeutic concentrations of SED in the serum of SUDEP patients may be the consequence of inadequate treatment and low compliance to treatment that causes the development of pseudoresistant seizures and, hence, the higher risk of SUDEP. At the same time, AED per se play an important role in the modification of functions of the autonomic nervous system and may induce disturbances of heart rate and conductivity.

Treatment of cardiac arrhythmias in a mouse model of Rett syndrome with Na+-channel-blocking antiepileptic drugs

One quarter of deaths associated with Rett syndrome (RTT), an X-linked neurodevelopmental disorder, are sudden and unexpected. RTT is associated with prolonged QTc interval (LQT), and LQT-associated cardiac arrhythmias are a potential cause of unexpected death. The standard of care for LQT in RTT is treatment with β-adrenergic antagonists; however, recent work indicates that acute treatment of mice with RTT with a β-antagonist, propranolol, does not prevent lethal arrhythmias. In contrast, acute treatment with the Na⁺ channel blocker phenytoin prevented arrhythmias. Chronic dosing of propranolol may be required for efficacy; therefore, we tested the efficacy of chronic treatment with either propranolol or phenytoin on RTT mice. Phenytoin completely abolished arrhythmias, whereas propranolol showed no benefit. Surprisingly, phenytoin also normalized weight and activity, but worsened breathing patterns. To explore the role of Na⁺ channel blockers on QT in people with RTT, we performed a retrospective analysis of QT status before and after Na⁺ channel blocker antiepileptic therapies. Individuals with RTT and LQT significantly improved their QT interval status after being started on Na⁺ channel blocker antiepileptic therapies. Thus, Na⁺ channel blockers should be considered for the clinical management of LQT in individuals with RTT.

Sudden unexpected death in epilepsy. Potential role of antiepileptic drugs

Among people with epilepsy, there is a 20-fold higher risk of dying suddenly and unexpectedly compared with the general population. This phenomenon is called sudden unexpected death in epilepsy (SUDEP) and the term is used when sudden death occurs in an otherwise reasonably healthy person with epilepsy and the autopsy is unrevealing. In most cases, SUDEP occurs during sleep and is unwitnessed. Risk factors for SUDEP include the presence or number of generalized tonic-clonic seizures (GTCS), nocturnal seizures, young age at epilepsy onset, longer duration of epilepsy, dementia, absence of cerebrovascular disease, asthma, male gender, symptomatic aetiology of epilepsy and alcohol abuse. Suggested factors predisposing to SUDEP have included long-QT-related mutations, impaired serotonergic brain stem control of respiration, altered autonomic control and seizures with a pronounced postictal suppression and respiratory compromise. Final events that may lead up to SUDEP are a postictal CNS shutdown with pronounced EEG suppression, ictal or postictal apnoea, and ictal cardiac arrhythmia. It is unknown whether antiepileptic drugs (AEDs) modify the risk for SUDEP. Studies have consistently found that the presence or number of GTCS is associated with an increased risk for SUDEP. Since continued presence of GTCS clearly necessitates the use of AEDs, both factors must be taken into account to determine whether one or both increases the risk for SUDEP. Some studies suggest that AEDs, such as lamotrigine and carbamazepine, may increase the risk of SUDEP, but rarely adjust for GTCS. Other studies, which have found that AEDs are associated with a decreased SUDEP risk, either adjust for the number of GTCS or are meta-analyses of randomized clinical trials. Studies assessing the impact of AEDs on the risk for SUDEP are limited because SUDEP is a rare event, making randomized clinical trials impossible to conduct. Observational studies focus on whether or not an AED was prescribed. When postmortem AED concentrations are assessed they are usually low or absent, perhaps due to sampling in deceased individuals, making it difficult to fully resolve whether AEDs increase or decrease SUDEP risk. Despite these caveats, the evidence suggests that AEDs are not associated with an increased risk for SUDEP on a population level, although some individuals may be susceptible to effects of AEDs. Recent evidence from a meta-analysis of randomized clinical trials of adjunctive AEDs at efficacious doses provides strong support for AED treatment as mono- or polytherapy to increase seizure control and protect against SUDEP in patients with refractory epilepsy. For patients for whom seizure control is unattainable, supervision or monitoring may prevent SUDEP, though this has never been formally tested.

Heart rate variability

Heart rate variability (HRV) provides indirect insight into autonomic nervous system tone, and has a well-established role as a marker of cardiovascular risk. Recent decades brought an increasing interest in HRV assessment as a diagnostic tool in detection of autonomic impairment, and prediction of prognosis in several neurological disorders. Both bedside analysis of simple markers of HRV, as well as more sophisticated HRV analyses including time, frequency domain and nonlinear analysis have been proven to detect early autonomic involvement in several neurological disorders. Furthermore, altered HRV parameters were shown to be related with cardiovascular risk, including sudden cardiac risk, in patients with neurological diseases. This chapter aims to review clinical and prognostic application of HRV analysis in diabetes, stroke, multiple sclerosis, muscular dystrophies, Parkinson's disease and epilepsy.

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.

Cardiac arrhythmias and sudden unexpected death in epilepsy (SUDEP)

Sudden unexpected death in epilepsy (SUDEP) is a major clinical problem in epilepsy patients in the United States, especially those with chronic, uncontrolled epilepsy. Several pathophysiological events contributing to SUDEP include cardiac arrhythmias, respiratory dysfunction, and dysregulation of systemic or cerebral circulation. There is a significant body of literature suggesting the prominent role of cardiac arrhythmias in the pathogenesis of SUDEP. There is evidence to say that long-standing epilepsy can cause physiological and anatomical autonomic instability resulting in life-threatening arrhythmias. Tachyarrhythmias, bradyarrhythmias, and asystole are commonly seen during ictal, interictal, and postictal phase in epilepsy patients. It is unclear if these rhythm disturbances need attention as some of them may be just benign findings. Evidence regarding prolonged cardiovascular monitoring or the benefit of pacemaker/defibrillator implantation for primary or secondary prevention in epilepsy patients is limited. Awareness regarding pathophysiology, cardiac effects, and management options of SUDEP will become useful in guiding more individualized treatment in the near future. (PACE 2011; 1-8).

Characterization of novel KCNH2 mutations in type 2 long QT syndrome manifesting as seizures

BACKGROUND

Long QT syndrome (LQTS) is characterized by corrected QT interval prolongation leading to torsades de pointes and sudden cardiac death. LQTS type 2 (LQTS2) is caused by mutations in the KCNH2 gene, leading to a reduction of the rapidly activating delayed rectifier K+ current and loss of human ether-à-go-go-related gene (hERG) channel function by different mechanisms. Triggers for life-threatening arrhythmias in LQTS2 are often auditory stimuli.

OBJECTIVES

To screen KCNH2 for mutations in patients with LQTS2 on an electrocardiogram and auditory-induced syncope interpreted as seizures and sudden cardiac death, and to analyze their impact on the channel function in vitro.

METHODS

The KCNH2 gene was screened for mutations in the index patients of three families. The novel mutations were reproduced in vitro using site-directed mutagenesis and characterized using the Xenopus oocyte expression system in voltage clamp mode.

RESULTS

Novel KCNH2 mutations (Y493F, A429P and del234-241) were identified in the index patients with mostly typical LQTS2 features on their electrocardiograms. The biochemical data revealed a trafficking defect. The biophysical data revealed a loss of function when mutated hERG channels were coexpressed with the wild type.

CONCLUSIONS

In all families, at least one patient carrying the mutation had a history of seizures after auditory stimuli, which is a major trigger for arrhythmic events in LQTS2. Seizures are likely due to cardiac syncope as a consequence of mutation-induced loss of function of the rapidly activating delayed rectifier K+ current.

Sudden unexpected death in epilepsy: risk factors and potential pathomechanisms

Sudden unexpected death in epilepsy (SUDEP) is the most common cause of death directly related to epilepsy, and most frequently occurs in people with chronic epilepsy. The main risk factors for SUDEP are associated with poorly controlled seizures, suggesting that most cases of SUDEP are seizure-related events. Dysregulation in cardiac and respiratory physiology, dysfunction in systemic and cerebral circulation physiology, and seizure-induced hormonal and metabolic changes might all contribute to SUDEP. Cardiac factors include bradyarrhythmias and asystole, as well as tachyarrhythmias and alterations to cardiac repolarization. Altered electrolytes and blood pH, as well as the release of catecholamines, modulate cardiac excitability and might facilitate arrhythmias. Respiratory symptoms are not uncommon during seizures and comprise central apnea or bradypnea, and, less frequently, obstruction of the airways and neurogenic pulmonary edema. Alterations to autonomic function, such as a reduction in heart rate variability or disturbed baroreflex sensitivity, can impair the body's capacity to cope with challenging situations of elevated stress, such as seizures. Here, we summarize data on the incidence of and risk factors for SUDEP, and consider the pathophysiological aspects of chronic epilepsy that might lead to sudden death. We suggest that SUDEP is caused by the fatal coexistence of several predisposing and triggering factors.

Application of a vagal nerve stimulator in an epilepsy patient with cardiac pacemaker after post-ictal cardiac arrest

In this case report we present a patient with temporal lobe epilepsy (TLE) showing partial complex seizures and secondary generalization, and treated with several antiepileptic drugs. After two consecutive seizures she had an episode of cardiac arrest followed by AV-block III which led to the implantation of a cardiac pacemaker. She subsequently received a vagal nerve stimulator because of poor response to epilepsy treatment. Combined treatment with two different electromagnetic stimulators raises the question of safety during surgery which is discussed.

A review of sudden unexpected death in epilepsy: prediction of patients at risk

This review attempts to provide up-to-date quantitative data from published reports on sudden unexpected death in epilepsy (SUDEP) appearing on Medline and, especially, to provide a means to predict the probability of SUDEP in a given patient. The mean incidence of SUDEP was 1.8/1000, similar to the median of 1.5. The mean standardized mortality ratio was 6.8, and the mean percentage of SUDEP cases among deaths from epilepsy was 16.6. Seventeen risk factors were identified, each given a value according to the number of studies in the literature that specified that condition as a significant risk. The addition of these 17 values then indicated the risk for a given patient. The author calculated these for a group of 91 patients who died of SUDEP and also for 91 live patients. Many of their values for the different risks were significantly different. The sensitivity of these SUDEP values was 71.3%, the specificity 81.8%, and the positive predictive value 84.6%. A discussion includes the question of whether the death in SUDEP is primarily cardiac or pulmonary and the suggestion that it may be either or both in a given patient. The most important risk factor in this study was noncompliance with antiepileptic medication, and the main message of this study to caregivers is that therapeutic drug levels are crucial to avoid SUDEP.

Changes in autonomic cardiac control in patients with epilepsy after discontinuation of antiepileptic drugs: a randomized controlled withdrawal study

The aim of this study was to assess cardiac autonomic control in patients with epilepsy before and after withdrawal of antiepileptic drugs (AEDs). The study was prospective, randomized and double blinded. Spectral analysis of heart rate variability (HRV) in 24 h ECG-registration before and after withdrawal of AEDs was used to assess autonomic cardiac control. The assessment of HRV with spectral analysis was based on sinus rhythm and normal heart beats [normal to normal beat (NN)]. Thirty-nine patients had 24 h rhythms free from any ectopic beats both before and after intervention, and were included in the analysis. Significant differences were found in the withdrawal group: filtered RR intervals for all 5 min segments of the analysis; percentage of differences between adjacent filtered RR intervals that are greater than 50 ms for the whole analysis; very low frequency power; low frequency power and high frequency power. The results demonstrate that slow withdrawal of AEDs in seizure-free patients with epilepsy on drug mono-therapy resulted in an increase in both parasympathetic and sympathetic functions, indicative of increased power amongst patients following cessation of AED treatment. As low HRV has been associated with increased mortality in patients with other diseases, this increased HRV may be beneficial.

Mortality in epilepsy

All studies report an increased mortality risk for people with epilepsy compared with the general population. Population-based studies have demonstrated that the increased mortality is often related to the cause of the epilepsy. Common etiologies include neoplasia, cerebrovascular disease, and pneumonia. Deaths in selected cohorts, such as sudden unexpected death in epilepsy (SUDEP), status epilepticus (SE), suicides, and accidents are more frequently epilepsy-related. SUDEP is a particular cause for concern in younger people, and whether and when SUDEP should be discussed with patients with epilepsy remain problematic issues. Risk factors for SUDEP include generalized tonic-clonic seizures, increased seizure frequency, concomitant learning disability, and antiepileptic drug polypharmacy. The overall incidence of SE may be increasing, although case fatality rates remain constant. Mortality is frequently secondary to acute symptomatic disorders. Poor compliance with treatment in patients with epilepsy accounts for a small proportion of deaths from SE. The incidence of suicide is increased, particularly for individuals with epilepsy and comorbid psychiatric conditions. Late mortality figures in patients undergoing epilepsy surgery vary and are likely to reflect differences in case selection. Future studies of mortality should be prospective and follow agreed guidelines to better quantify risk and causation in individual populations.

Risk factors in sudden death in epilepsy (SUDEP): the quest for mechanisms

People with epilepsy may die suddenly and unexpectedly without a structural pathological cause. Most SUDEP cases are likely to be related to seizures. SUDEP incidence varies and is <1:1,000 person-years among prevalent cases in the community and approximately 1:250 person years in specialist centres. Case-control studies identified certain risk factors, some potentially amenable to manipulation, including uncontrolled convulsive seizures and factors relating to treatment and supervision. Both respiratory and cardiac mechanisms are important. The apparent protective effect of lay supervision supports an important role for respiratory factors, in part amenable to intervention by simple measures. Whereas malignant tachyarrhythmias are rare during seizures, sinus bradycardia/arrest, although infrequent, is well documented. Both types of arrhythmias can have a genetic basis. This article reviews SUDEP and explores the potential of coexisting liability to cardiac arrhythmias as a contributory factor, while acknowledging that at present, bridging evidence between cardiac inherited gene determinants and SUDEP is lacking.

SUDEP in the Netherlands: A retrospective study in a tertiary referral center

OBJECTIVE

To evaluate risk factors for sudden and unexpected death in epilepsy (SUDEP) in a high-risk population, i.e. patients treated in a Dutch tertiary referral center for epilepsy.

METHODS

All patients who died between January 1999 and April 2004 while under treatment of the epilepsy center were identified. Based on clinical data, deaths were classified as definite, probable, possible or non-SUDEP. Potential risk factors were compared in SUDEP cases and non-SUDEP cases.

RESULTS

SUDEP incidence was 1.24 per 1000 patient years. SUDEP patients died at a younger age than patients from the control group of non-SUDEP deaths with epilepsy and had an earlier onset of epilepsy. However, the frequently mentioned factors in previous studies, i.e. male sex, generalized tonic-clonic seizures, high seizure frequency, specific AEDs, polytherapy with several AEDs, mental retardation, psychiatric illness and psychotropic comedication, were not found to be correlated with SUDEP.

CONCLUSIONS

Even in this high-risk population of patients with refractory epilepsy, treated in a tertiary referral center, SUDEP is not a frequently occurring phenomenon. Specific risk factors could not be identified within an already high-risk population.

Finding the missing link between ictal bradyarrhythmia, ictal asystole, and sudden unexpected death in epilepsy

Basic science studies of the human brain have supported the cortical representation of cardiovascular responses, including heart rate variability. Clinical observations of ictal bradyarrhythmia may be mechanistically explained by the influence of the central autonomic network, although the localization and lateralization issues need to be considered in the light of patterns of seizure spread, hand dominance, and presence of lesions. Ictal bradyarrhythmia also offers a mechanistic explanation of sudden unexpected death in epilepsy (SUDEP), though it may explain only some but not all cases of SUDEP. The missing links are (1) clinical evidence of common factors shared by patients with ictal bradyarrhythmia and patients who die from SUDEP, (2) evidence of arrhythmia as a risk factor for SUDEP from epidemiological studies, and, (3) determination of the importance of ictal bradyarrhythmia in SUDEP with respect to other proposed mechanisms including apnea and intrinsic cardiac abnormalities. There remains a need to review the seizure mechanisms in cases of SUDEP and to step up the amount of concurrent ECG/intracranial EEG analysis in both ictal bradyarrhythmia and SUDEP cases.

Abrupt Discontinuation of Psychotropic Drugs Following Confirmation of Pregnancy: A Risky Practice

A number of pregnant women suffer from psychiatric disorders that require treatment with psychotropic drugs. A literature review suggests that these medications are relatively safe to use during pregnancy. Abrupt discontinuation of these drugs can have both physiological and psychological ramifications, which include unpleasant physical symptoms and re-emergence of the psychiatric condition. Therefore, it is not good practice to discontinue these medications abruptly upon diagnosis of pregnancy.

Time and frequency domain analyses of heart rate variability in patients with epilepsy

Heart rate variability (HRV) is a useful tool for the detection of sympathetic-parasympathetic balance of autonomic nervous system in patients at risk of sudden death (SD). SD is more common in patients with epilepsy and the exact mechanisms of SD are unknown. Autonomic nervous system involvement in patients with epilepsy has rarely been studied and has shown conflicting results. Our purpose was to determine if HRV showed any changes in patients with epilepsy in comparison with normal population. A short period analysis of HRV was performed for both the frequency and time domain in 43 epilepsy patients who had generalized tonic-clonic seizures (GTCS) and who were not taking any medications and also in 43 age and sex matched controls. In the time domain analysis, patients displayed higher SDNN (standard deviation of all R-R intervals), SDANN (standard deviation of mean NN intervals in 5 min recordings) and HRV triangular index than did healthy subjects (p < 0.0001). Patients tended to display higher pNN50 (number of R-R intervals differed by > 50 ms from adjacent interval divided by the total number of all R-R intervals) and RMSSD (root-mean-square of successive differences) values than did healthy subjects, but the differences were not statistically significant (p > 0.05). In the frequency domain analysis, the spectral measures of HRV showed a reduction of high frequency (HF) values (is a marker of parasympathetic activity) and an increase of low frequency (LF) values (is a measure of sympathetic activity); as a result, the ratio between low and high frequencies (LF/HF) was significantly increased (p < 0.0001, p < 0.0001 and p < 0.001, respectively). Our data suggests an increase in the sympathetic control of the heart rate in epilepsy patients who have GTCS. This increased sympathetic activity could play a key role in the development of ventricular tachyarrhythmias in patients with epilepsy and may be related to the higher incidence of sudden death in this disorder as compared to controls.

Cardiovascular Regulation and Hippocampal Sclerosis

PURPOSE

Cardiovascular dysregulation has been detected in patients with temporal lobe epilepsy (TLE) by using cardiovascular reflex tests and analysis of heart rate variability (HRV). The two methods have not previously been used in the same study to compare them in the assessment of cardioregulatory function. Magnetic resonance imaging (MRI) is considered the best method to reveal structural changes such as hippocampal sclerosis associated with TLE. It is not known whether these structural changes modify cardioregulatory function in patients with TLE.

METHODS

Standard cardiovascular reflex tests and analysis of spectral and dynamic measures from 24-h electrocardiogram (ECG) recordings were performed for eight patients with and 31 patients without hippocampal sclerosis and for 72 control subjects. MRI also was performed in each patient to reveal hippocampal sclerosis.

RESULTS

Various measures of cardiovascular reflexes and HRV were diminished in patients with TLE compared with the control subjects. No significant differences were found in the measures obtained from the cardiovascular reflex tests or analysis of HRV between those with and without hippocampal sclerosis, although a nonsignificant trend toward reduced values was seen among those with hippocampal sclerosis. The values of cardiovascular reflexes and spectral analysis of HRV correlated with each other.

CONCLUSIONS

These results suggest that functional rather than structural changes related to TLE are involved mainly as a mechanism of altered cardioregulatory function. The cardiovascular reflex test and analysis of HRV both appear to be useful in studying cardioregulation in patients with TLE.

Do antiepileptic drugs play a role in sudden unexpected death in epilepsy?

Sudden unexpected death in epilepsy (SUDEP) accounts for approximately 2% of deaths in population-based cohorts of epilepsy, and up to 25% of deaths in cohorts of more severe epilepsy. When it occurs, SUDEP usually follows a generalised tonic-clonic seizure. Unresponsiveness, apnoea, and cardiac arrest occur in SUDEP, rather than the typical gradual recovery. The great majority of tonic-clonic seizures occur without difficulty and how the rare seizure associated with SUDEP differs from others is unknown.Three mechanisms have been proposed for SUDEP: cardiac arrhythmia, neurogenic pulmonary oedema, and postictal suppression of brainstem respiratory centres leading to central apnoea. Recent studies have found that the incidence of SUDEP increases with the severity of epilepsy in the population studied. The duration of epilepsy, number of tonic-clonic seizures, mental retardation, and simultaneous treatment with more than two antiepileptic drugs are independent risk factors for SUDEP. Some studies have reported that carbamazepine use, carbamazepine toxicity, and frequent, rapid changes in carbamazepine levels, may be associated with SUDEP. Other evidence indicates that carbamazepine could potentially increase the risk for SUDEP by causing arrhythmia or by altering cardiac autonomic function. However, this evidence is tenuous and most studies have not found an association between the use of carbamazepine or any other individual antiepileptic drug and SUDEP. There is little information regarding antiepileptic drugs other than phenytoin and carbamazepine. The incidence of SUDEP with gabapentin, tiagabine, and lamotrigine clinical development programmes is in the range found in other populations with refractory epilepsy. This suggests that these individual antiepileptic drugs are no more likely to cause SUDEP than antiepileptic drugs in general. Best current evidence indicates that the risk of SUDEP can be decreased by aggressive treatment of tonic-clonic seizures with as few antiepileptic drugs as necessary to achieve complete control. At present there is no strong reason to avoid any particular antiepileptic drug. Further studies are needed to elucidate the potential role of individual antiepileptic drugs in SUDEP and establish clinical relevance, if any. These studies may be challenging to conduct and interpret because SUDEP is relatively uncommon and large numbers will be necessary to narrow confidence intervals to determine the clinical relevance. Also adjustments will be needed to account for the potent risks associated with other independent factors.

Carbamazepine affects autonomic cardiac control in patients with newly diagnosed epilepsy

Previous studies indicate that epilepsy patients may have impaired autonomic cardiovascular control in the interictal state although it is unclear whether the observed reduction in cardiovascular responses is due to the epilepsy and the interictal epileptogenic discharges, or to the treatment with antiepileptic drugs. Spectral analysis of heart rate variability makes it possible to partly separate the sympathetic components, low frequency (LF), from the vagal components, high frequency (HF) of autonomic cardiac control. We used spectral analysis of heart rate variability to assess the effect of carbamazepine (CBZ) on autonomic cardiac control in patients with newly diagnosed epilepsy. Fifteen adult outpatients with newly diagnosed seizures/epilepsy underwent 24 h ambulatory EKG recordings before and after commencement of CBZ treatment. Total power as well as low frequency (LF), very low frequency (VLF) and high frequency (HF) power in heart rate variability was calculated. When analysing the full 24 h recordings, patients had significantly lower standard deviation of RR-intervals (P=0.0015), total power (P=0.0010), LF (P=0.0002), VLF (P=0.0025) and HF (P=0.0139) during treatment with CBZ than before. The results were very similar for daytime and night time recordings. Our observations demonstrate that CBZ may suppress both parasympathetic and sympathetic functions in newly diagnosed patients with epilepsy. The possible implications of our results for sudden unexpected death in epilepsy are discussed.

Sudden unexplained death in adults caused by intracranial pathology

Sudden unexplained deaths as a result of intracranial lesions in adults are an important component of medicolegal practice and are best examined as a combined effort by a forensic pathologist, or a histopathologist experienced in coroner's necropsies, and a neuropathologist. Analysis of case material on file in the University of Glasgow's departments of forensic medicine and science, and neuropathology showed that the principal causes were sudden unexplained death in epilepsy (SUDEP), intracranial haemorrhage, either natural or after trauma, purulent meningitis or an abscess, and tumours. The mechanisms of death are considered to be the rapid increase of intracranial pressure caused by bleeding into the various compartments of the brain, or an acute obstructive hydrocephalus, and in cases where death is very rapid, autonomic and/or neurochemical dysfunction.

Heart rate and heart rate variability changes in the intracarotid sodium amobarbital test

PURPOSE

Changes in heart rate and heart rate variability have been found in prior studies performed during the intracarotid sodium amobarbital (ISA) test. However, these results are not entirely consistent with current models of differential cerebral involvement in the modulation of the heart. This study was designed to re-investigate this topic with a larger N than has heretofore been used.

METHODS

The electrocardiogram was recorded during left and right ISAs in 73 subjects. Raw heart rate and heart rate variability were calculated.

RESULTS

Raw heart rate increased during inactivation of either hemisphere, but more so for the right hemisphere. Heart rate variability changes consistent with decreasing parasympathetic tone also were found to occur during either ISA, but to a significant degree, only during right ISA.

CONCLUSIONS

The right hemisphere appears to have a greater role in cerebral regulation of cardiac function, perhaps by virtue of the modification of parasympathetic effects.

Mortality in pediatric epilepsy

Mortality in pediatric epilepsy is the subject of this review. Epilepsy in both adults and children increases the risk of premature death. Conditions that are comorbid with epilepsy may carry an increased mortality risk. Patients with neurologic compromise may be at risk for aspiration and critical respiratory disease. Epilepsy per se enhances the risks of accidents, particularly drowning. Epilepsy may result in unwitnessed or, less frequently, witnessed sudden death. Witnessed sudden death frequently involves an observed seizure. Cardiac and respiratory mechanisms for epileptic sudden death have been proposed. Reducing the number of seizures should reduce the risk for sudden death. Awareness of the increased risk for premature death associated with epilepsy may enhance patients' and parents' cooperation with therapy.

[Bradycardia as an epileptic manifestation in temporal epilepsy: report of a case]

We describe a patient who had cardiac arrhythmia as epileptic manifestation. In a 34-year-old woman who had many episodes of loss of consciousness, the simultaneous ECG and video-EEG monitoring recorded bradycardia with a short episode of asystole (4 seconds) and left temporal rhythmic theta activity on EEG. MRI showed a small mass lesion in the left parahippocampal gyrus. Alterations in cardiac rhythm have been reported in epileptic seizures and tachycardia is the most common finding associated with them; bradyarrhythmia during seizures was uncommon. Many interconnections among insular cortex, limbic system and hypothalamus, may be responsible for vegetative manifestations in temporal lobe epilepsy.

Sudden unexpected death in epilepsy (SUDEP): a clinical perspective and a search for risk factors

OBJECTIVES

To examine the risk factors and their relative importance and possible role in sudden unexpected death in epilepsy (SUDEP).

METHODS

The study was conducted as a retrospective analysis of deaths in an outpatient population of a tertiary referral centre, based on clinical and pathological data.

RESULTS

Of a total of 140 deaths, 61 (44%) had not been to postmortem and were excluded, 37 (26%) had a verified cause of death and formed the non-SUDEP group, and 42 (30%) were classified as SUDEP. In the SUDEP group there was pulmonary oedema in 62%, signs of preceding seizures in 67%, no visible seizures in three of six observed deaths. A high seizure frequency prevailed in SUDEP as well as non-SUDEP. Sixty per cent of deaths were sleep related. Various other circumstances were temporally associated with death. The prone position at death was seen in 71% of the SUDEP patients; possible interpretations are discussed. Supposedly subtherapeutic serum concentrations of one or more antiepileptic drugs were found in 57% of those with reported serum concentrations. Alcohol was not a factor in the material, whereas hyponatraemia was seen in two cases.

CONCLUSIONS

Most cases of SUDEP are preceded by seizures; their presence, frequency, type, aetiology, tractability, and the use of antiepileptic drugs are factors in the demise. No common risk factor, present in all cases of SUDEP, could be found, suggesting the probability of multiple mechanisms behind SUDEP.

Heart rate variability in patients with epilepsy

Autonomic function was studied by the use of spectral analysis of heart-rate variability in patients with epilepsy in relation to type of epilepsy and anti-epileptic drug therapy. A total of 21 patients with juvenile myoclonic epilepsy (JME) and 21 with temporal lobe epilepsy (TLE) were included; 18 patients were treated with carbamazepine (CBZ), 16 with valproate (VPA) and seven with phenytoin (PHT). One healthy drug free control, matched for age and sex, was selected for each patient. Patients and controls underwent an ambulatory 24 h EKG. Heart-rate variability was analyzed in time and frequency domains. Patients with TLE had significantly lower S.D. of the RR-intervals, lower low frequency power and a lower low frequency/high frequency power ratio than their controls. A lower low frequency/high frequency power ratio was the only significant difference between the JME patient group and their controls. Treatment, however, may have had a considerable influence on the heart rate variability in the epilepsy patients. Patients on CBZ had significantly lower S.D. of RR-intervals, low frequency power and a low frequency/ high frequency power ratio than did their matched healthy drug free controls. The ratio of low frequency/high frequency power was also lower in patients on VPA compared with their controls, but apart from that no differences could be demonstrated between this treatment group and the controls. In conclusion, patients with epilepsy appear to have an altered autonomic control of the heart, with a reduction in some heart-rate variability measures, suggesting a decreased sympathetic tone, which may be related to the drug therapy or the epilepsy as such. Further studies are warranted to explore these changes and their possible relevance for sudden death in epilepsy.