Interictal cardiovascular autonomic responses in patients with temporal lobe epilepsy

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.

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.

Assessing epilepsy-related autonomic manifestations: Beyond cardiac and respiratory investigations

The Autonomic Nervous System (ANS) regulates many critical physiological functions. Its control relies on cortical input, especially limbic areas, which are often involved in epilepsy. Peri-ictal autonomic dysfunction is now well documented, but inter-ictal dysregulation is less studied. In this review, we discuss the available data on epilepsy-related autonomic dysfunction and the objective tests available. Epilepsy is associated with sympathetic-parasympathetic imbalance and a shift towards sympathetic dominance. Objective tests report alterations in heart rate, baroreflex function, cerebral autoregulation, sweat glands activity, thermoregulation, gastrointestinal and urinary function. However, some tests have found contradictory results and many tests suffer from a lack of sensitivity and reproducibility. Further study on interictal ANS function is required to further understand autonomic dysregulation and the potential association with clinically-relevant complications, including risk of Sudden Unexpected Death In Epilepsy (SUDEP).

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.

Seizures detection using multimodal signals: a scoping review

INTRODUCTION

Epileptic seizures are common neurological disorders in the world, impacting 50 million people globally. Around 30% of patients with seizures suffer from refractory epilepsy, where seizures are not controlled by medications. The unpredictability of seizures makes it essential to have a continuous seizure monitoring system outside clinical settings for the purpose of minimizing patients' injuries and providing additional pathways for evaluation and treatment follow-up. Autonomic changes related to seizure events have been extensively studied and attempts made to apply them for seizure detection and prediction tasks. This scoping review aims to depict current research activities associated with the implementation of portable, wearable devices for seizure detection or prediction and inform future direction in continuous seizure tracking in ambulatory settings.

METHODS

Overall methodology framework includes 5 essential stages: research questions identification, relevant studies identification, selection of studies, data charting and summarizing the findings. A systematic searching strategy guided by systematic reviews and meta-analysis (PRISMA) was implemented to identify relevant records on two databases (PubMed, IEEE).

RESULTS

A total of 30 articles were included in our final analysis. Most of the studies were conducted off-line and employed consumer-graded wearable device. ACM is the dominant modality to be used in seizure detection, and widely deployed algorithms entail Support Vector Machine, Random Forest and threshold-based approach. The sensitivity ranged from 33.2% to 100% for single modality with a false alarm rate (FAR) ranging from 0.096 /day to 14.8 /day. Multimodality has a sensitivity ranging from 51% to 100% with FAR ranging from 0.12/day - 17.7/day.

CONCLUSION

The overall performance in seizure detection system based on non-cerebral physiological signals is promising, especially for the detection of motor seizures and seizures accompanied with intense ictal autonomic changes.

Interictal autonomic dysfunction in patients with epilepsy

Background

Autonomic nervous system (ANS) symptoms are frequently present in people with epilepsy (PwE). They are generally more prominent when they originate from the temporal lobe. We aim to investigate the alterations of autonomic functions during the interictal period in patient with temporal lobe epilepsy (TLE) and idiopathic generalized epilepsy (IGE) using heart-based tests, blood pressure (BP)-based tests and sympathetic skin response (SSR). Forty-eight PwE with disease duration ranging from 2 to 15 years and 51 healthy individuals were studied. Long-term electroencephalography (EEG) monitoring, the heart rate variability (HRV) during normal breathing, deep breathing, Valsalva maneuver and standing, BP responses during standing, to isometric hand grip and to mental arithmetic, and the SSR was recorded for all participants.

Results

31 patients with TLE and 17 with IGE showed lower RR-IV values during deep breathing, Valsalva maneuver and standing, but not during rest, impaired BP responses during standing, isometric hand grip, and mental arithmetic. Also, prolonged SSR latencies. Within PwE group, no difference was noticed between males and females, nor between the left and right temporal lobes.

Conclusion

Abnormal autonomic (sympathetic and parasympathetic) regulatory functions suggest that epilepsy may alter the autonomic function and this is not only in TLE but rather in IGE too. These autonomic changes are irrespective of the localization of epilepsy between the two hemispheres. The ANS changes in epileptic patients, particularly those with autonomic symptoms, confirm that electrophysiologic measures of autonomic function may be of value in preventing sudden unexpected death in epilepsy.

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.

Pre-ictal heart rate variability alterations in focal onset seizures and response to vagus nerve stimulation

PURPOSE

Vagus nerve stimulation (VNS) is an effective and well-known treatment for drug resistant epilepsy (DRE) patients since 1997, yet prediction of treatment response before implantation is subject of ongoing research. Neuroimaging and neurophysiological studies investigating the vagal afferent network in resting state documented that differences in between epilepsy patients were related to treatment response. This study investigated whether an event-related parameter, pre-ictal heart rate variability (HRV) is associated with response to VNS therapy.

METHODS

DRE patients underwent video-electroencephalography (EEG) recording before VNS implantation. HRV parameters (time, non-linear and frequency domain) were assessed for every seizure during two 10 min timeframes: baseline (60 min before seizure onset) and pre-ictal (10 min before seizure onset). Pre-ictal HRV parameter alterations were correlated with VNS response after one year of VNS therapy and seizure characteristics (temporal/extratemporal, left/right or bilateral).

RESULTS

104 seizures from 22 patients were evaluated. Eleven patients were VNS responders with a seizure frequency reduction of ≥ 50 % after one year of VNS. In VNS responders no changes in HRV parameters were found while in VNS non-responders the time domain and non-linear HRV variables decreased significantly (p = 0.024, p = 0.005, p = 0.005) during the pre-ictal time frame. 10/11 VNS non-responders had a seizure lateralization to the left compared to 4/11 VNS responders.

CONCLUSION

VNS non-responders were characterized by a significant decrease of pre-ictal HRV (time domain/non-linear variables) suggesting a sudden autonomic imbalance probably due to an impaired central autonomic function that makes it at the same time unlikely to respond to VNS.

Interictal Heart Rate Variability Analysis Reveals Lateralization of Cardiac Autonomic Control in Temporal Lobe Epilepsy

Purpose: The temporal lobe, a critical hub for cognition, also plays a central role in the regulation of autonomic cardiovascular functions. Lesions in this area are usually associated with abnormalities in the regulation of heart rate (HR) and blood pressure (BP). The analysis of the heart rate variability (HRV) is useful to evaluate the cardiac parasympathetic nervous system activity. This study aims at comparing HRV changes occurring in two groups of patients suffering from Temporal Lobe Epilepsy (TLE). To that aim, we evaluated patients differentiated by the right or left location of the epileptic foci.

Materials and Methods: Fifty-two adult patients with a diagnosis of TLE were enrolled. Each patient underwent a 20-min EEG + EKG recording in resting state. According to the localization of epileptic focus, patients were divided into two subgroups: right TLE (R-TLE) and left TLE (L-TLE). HRV parameters were calculated with a short-lasting analysis of EKG recordings. Time-domain and frequency domain-related, as well as non-linear analysis, parameters, were compared between the two groups.

Results: Compared to the R-TLE group, L-TLE subjects showed a significant decrease in low frequency (LF) (p < 0.01) and low frequency/high-frequency ratio (LF/HF) (p < 0.001) as well as increased HF values (p < 0.01), a parameter indicative of the presence of an increased cardiac vagal tone. These results were also confirmed in the subgroup analysis that took into account the seizure types, responses to antiepileptic drugs, seizure frequencies, and etiology.

Conclusions: The main finding of the study is that, compared to R-TLE, L-TLE is associated with increased cardiac vagal tone. These results indicate that patients with TLE exhibit a lateralized cardiac autonomic control. L-TLE patients may have a lower risk of developing cardiac dysfunctions and less susceptible to develop Sudden Death for Epilepsy (SUDEP).

Wearable Epileptic Seizure Prediction System with Machine-Learning-Based Anomaly Detection of Heart Rate Variability

A warning prior to seizure onset can help improve the quality of life for epilepsy patients. The feasibility of a wearable system for predicting epileptic seizures using anomaly detection based on machine learning is evaluated. An original telemeter is developed for continuous measurement of R-R intervals derived from an electrocardiogram. A bespoke smartphone app calculates the indices of heart rate variability in real time from the R-R intervals, and the indices are monitored using multivariate statistical process control by the smartphone app. The proposed system was evaluated on seven epilepsy patients. The accuracy and reliability of the R-R interval measurement, which was examined in comparison with the reference electrocardiogram, showed sufficient performance for heart rate variability analysis. The results obtained using the proposed system were compared with those obtained using the existing video and electroencephalogram assessments; it was noted that the proposed method has a sensitivity of 85.7% in detecting heart rate variability change prior to seizures. The false positive rate of 0.62 times/h was not significantly different from the healthy controls. The prediction performance and practical advantages of portability and real-time operation are demonstrated in this study.

Increased ACh-Associated Immunoreactivity in Autonomic Centers in PTZ Kindling Model of Epilepsy

Experimental and clinical studies of cardiac pathology associated with epilepsy have demonstrated an impact on the autonomic nervous system (ANS). However, the underlying molecular mechanism has not been fully elucidated. Molecular investigation of the neurotransmitters related receptor and ion channel directing ANS might help in understanding the associated mechanism. In this paper, we investigated the role of acetylcholine (ACh), which demonstrates both sympathetic and parasympathetic roles in targeted expression in terms of the relevant receptor and ion channel. Inwardly rectifying potassium (Kir) channels play a significant role in maintaining the resting membrane potential and controlling cell excitability and are prominently expressed in both the excitable and non-excitable tissues. The immunoreactivity of ACh-activated Kir3.1 channel and muscarinic ACh receptors (M2) in autonomic centers such as the brainstem, vagus nerve (VN) and atria of heart was confirmed by both histological staining and pathological tissue analysis. Significant upregulations of Kir3.1 and M2 receptors were observed in pentylenetetrazol (PTZ)-kindled epileptic rats for all related tissues investigated, whereas no pathological difference was observed. These findings provide proof-of-concept that changes in ACh-associated immunoreactivity might be linked to the ANS dysfunctions associated with epilepsy.

Epilepsy and aging

The intersection of epilepsy and aging has broad, significant implications. Substantial increases in seizures occur both in the elderly population, who are at a higher risk of developing new-onset epilepsy, and in those with chronic epilepsy who become aged. There are notable gaps in our understanding of aging and epilepsy at the basic and practical levels, which have important consequences. We are in the early stages of understanding the complex relationships between epilepsy and other age-related brain diseases such as stroke, dementia, traumatic brain injury (TBI), and cancer. Furthermore, the clinician must recognize that the presentation and treatment of epilepsy in the elderly are different from those of younger populations. Given the developing awareness of the problem and the capabilities of contemporary, multidisciplinary approaches to advance understanding about the biology of aging and epilepsy, it is reasonable to expect that we will unravel some of the intricacies of epilepsy in the elderly; it is also reasonable to expect that these gains will lead to further improvements in our understanding and treatment of epilepsy for all age groups.

Assessment of cardiac structure and function in a murine model of temporal lobe epilepsy

Sudden unexpected death in epilepsy (SUDEP) is a significant cause of premature seizure-related death. An association between SUDEP and cardiac remodeling has been suggested. However, whether SUDEP is a direct consequence of acute or recurrent seizures is unsettled. The purpose of this study was to evaluate the impact of status epilepticus (SE) and chronic seizures on myocardial structure and function. We used the intracortical kainate injection model of temporal lobe epilepsy to elicit SE and chronic epilepsy in mice. In total, 24 C57/BL6 mice (13 kainate, 11 sham) were studied 2 and 30 days post-injection. Cardiac structure and function were investigated in-vivo with a 9.4 T MRI, electrocardiography (ECG), echocardiography, and histology [Haematoxylin/Eosin (HE) and Martius Scarlet Blue (MSB)] for staining of collagen proliferation and fibrin accumulation. In conclusion, we did not detect any significant changes in cardiac structure and function neither in mice 2 days nor 30 days post-injection.

Evaluation of Cardiac Repolarization Indices in Epilepsy Patients Treated with Carbamazepine and Valproic Acid

Background and Objectives: Epilepsy patients have a higher risk of sudden unexplained death compared to the rest of the population. Cardiac repolarization abnormalities might be seen in epilepsy during interictal periods. We aimed to evaluate the changes in electrocardiography (ECG) parameters in generalized tonic-clonic seizure patients treated with carbamazepine or valproic acid (VPA) drug. Materials and Methods: A totally of 129 subjects (66 epilepsy patients, 63 healthy subjects) were enrolled in the study. Of the patients, 36 were on carbamazepine and 30 were on VPA. There were 12-lead ECGs obtained from all participants. RR interval (time between consecutive R peaks), QT interval (defines the period of ventricular repolarization), corrected QT (QT interval corrected for heart rate; QTc), QTc-maximum (QTc-max), QTc-minimum (QTc-min), QTc dispersion (QTcd), P (atrial depolarization )-maximum (P-max), P-minimum (P-min) and P dispersion (Pd) were measured. Results: QTd (QT dispersion), QTcd, and Pd values were significantly higher in the patients compared to the controls (p < 0.01). QTcd, Pd, and P-max values were statistically higher in male patients compared to healthy male controls. QTcd values were significantly higher in female patients using carbamazepine compared to the female patients on VPA and healthy controls (p = 0.01). Male patients using VPA had significantly higher QTcd values against the male population in carbamazepine and control groups. Conclusions: This study demonstrated that QTd, QTcd, and Pd values were significantly higher in epilepsy patients than in healthy controls. In addition, female patients using carbamazepine and male patients using VPA were prone to ventricular arrhythmia compared to the control group.

Heart Rate Variability and Vagus Nerve Stimulation in Epilepsy Patients

Background

Vagus nerve stimulation (VNS) exerts a cortical modulating effect through its diffuse projections, especially involving cerebral structures related to autonomic regulation. The influence of VNS on cardiovascular autonomic function in drug-resistant epilepsy patients is still debated. We aimed to evaluate the impact of VNS on cardiovascular autonomic function in drug-resistant epilepsy patients, after three months of neurostimulation, using the heart rate variability (HRV) analysis.

Methodology

Multiple Trigonometric Regressive Spectral analysis enables a precise assessment of the autonomic control on the heart rate. We evaluated time and frequency-domain HRV parameters in resting condition and during sympathetic and parasympathetic activation tests in five epilepsy patients who underwent VNS procedure.

Results

We found appropriate cardiac autonomic responses to sympathetic and parasympathetic activation tests, described by RMSSD, pNN50, HF and LF/HF dynamics after three months of VNS. ON period of the neurostimulation may generate a transient vagal activation reflected on heart rate and RMSSD values, as observed in one of our cases.

Conclusion

VNS therapy in epilepsy patients seems not to disrupt the cardiac autonomic function. HRV represents a useful tool in evaluating autonomic activity. More extensive studies are needed to further explore cardiac autonomic response after neurostimulation.

Epilepsy and ultra-structural heart changes: The role of catecholaminergic toxicity and myocardial fibrosis. What can we learn from cardiology?

In this article, we explore the interaction of brain and heart in patients with epilepsy (PWE), focusing on new insights into possible pathways from epilepsy, catecholaminergic toxicity, subtle cardiac changes and sudden death. Initial evidence and biological plausibility point to an interaction between autonomic dysfunction, higher sympathetic drive, myocardial catecholaminergic toxicity and cardiac fibrosis resulting in subtle myocardial changes in structure, function, arrhythmogenesis and/or a heart failure-like phenotype in PWE. Non invasive imaging and biomarkers of cardiac injury and fibrosis are emerging as possible diagnostic tools to better stratify the risk of such individuals. Translational lessons from cardiac models of disease and ultra-structural lesions are used to support these considerations.

Subjective and physiological response to emotions in temporal lobe epilepsy and psychogenic non-epileptic seizures

BACKGROUND

Temporal lobe epilepsy (TLE) and psychogenic non-epileptic seizures (PNES) are conditions frequently associated with dysfunction in emotional regulation leading to increased risk of affective disorders. This study investigates emotional processing with an objective measure of emotional reactivity in patients with TLE and patients with PNES.

METHODS

34 patients with TLE and 14 patients with PNES were evaluated on skin conductance responses (SCR) to emotions induced by short films and compared to 34 healthy controls. An attention and a suppression condition were performed while viewing the films.

RESULTS

The both groups of patients disclosed lower SCR to emotions compared to controls, mainly in suppression condition. While TLE patients had lower SCR in attention condition than controls for fear, sadness and happiness, PNES had lower SCR only for happiness. In suppression condition, both had lower SCR than controls except for peacefulness in both groups and sadness in PNES. Subjective evaluations revealed that both patient's groups scored a higher intensity for sadness than controls in attention and lower for in fear and disgust in suppression only in TLE.

LIMITATIONS

The sample size in the PNES group and the lack of a control group with similar levels of mood symptoms limited the interpretation of our results.

CONCLUSION

As no correlation were found between SCR to emotions and scores of affective disorders, this pattern of responses might be underpinned by specific pathophysiological and cognitive mechanisms related to TLE and to PNES. Thus, therapeutic approaches targeting emotional autonomic responses can be of interest in the management of these conditions.

Post-ictal Modulation of Baroreflex Sensitivity in Patients With Intractable Epilepsy

Objective: Seizure-related autonomic dysregulation occurs in epilepsy patients and may contribute to Sudden Unexpected Death in Epilepsy (SUDEP). We tested how different types of seizures affect baroreflex sensitivity (BRS) and heart rate variability (HRV). We hypothesized that BRS and HRV would be reduced after bilateral convulsive seizures (BCS).

Methods: We recorded blood pressure (BP), electrocardiogram (ECG) and oxygen saturation continuously in patients (n = 18) with intractable epilepsy undergoing video-EEG monitoring. A total of 23 seizures, either focal seizures (FS, n = 14) or BCS (n = 9), were analyzed from these patients. We used 5 different HRV measurements in both the time and frequency domains to study HRV in pre- and post-ictal states. We used the average frequency domain gain, computed as the average of the magnitude ratio between the systolic BP (BPsys) and the RR-interval time series, in the low-frequency (LF) band as frequency domain index of BRS in addition to the instantaneous slope between systolic BP and RR-interval satisfying spontaneous BRS criteria as a time domain index of BRS.

Results: Overall, the post-ictal modulation of HRV varied across the subjects but not specifically by the type of seizures. Comparing pre- to post-ictal epochs, the LF power of BRS decreased in 8 of 9 seizures for patients with BCS; whereas following 12 of 14 FS, BRS increased. Similarly, spontaneous BRS decreased following 7 of 9 BCS. The presence or absence of oxygen desaturation was not consistent with the changes in BRS following seizures, and the HRV does not appear to be correlated with the BRS changes. These data suggest that a transient decrease in BRS and temporary loss of cardiovascular homeostatic control can follow BCS but is unlikely following FS.

Significance: These findings indicate significant post-ictal autonomic dysregulation in patients with epilepsy following BCS. Further, reduced BRS following BCS, if confirmed in future studies on SUDEP cases, may indicate one quantifiable risk marker of SUDEP.

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.

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.

Alteration of cardiac autonomic function in patients with newly diagnosed epilepsy

The aim of the study was to determine if heart rate variability (HRV) showed any changes in patients with newly diagnosed epilepsy in comparison with controls. Sixty‐five patients with epilepsy (38 males and 27 females), aged 30–50 years, who had never previously received treatment with antiepileptic drugs were eligible for inclusion in this study. Resting electrocardiogram (ECG) at spontaneous respiration was recorded for 5 min in supine position. Time‐domain analysis, frequency‐domain analysis, and Poincare plot of HRV were recorded from ECG. In time‐domain measures, the square root of the mean of the sum of the squares of differences between adjacent RR intervals (RMSSD) and percentage of consecutive RR intervals that differ by more than 50 msec (pNN50) were significantly less in patients with epilepsy. In frequency‐domain measures, high frequency [(HF) msec²], HF (nu), and low frequency [LF (msec²)] were significantly less in patients with epilepsy while LF (nu) and LF/HF were significantly high in patients with epilepsy. In Poincare plot, standard deviation perpendicular to line of Poincare plot (SD1) and standard deviation along the line of entity in Poincare plot (SD2) were significantly less in patients with epilepsy. Our results suggest that epileptic patients have an impact on the cardiac autonomic function as measured by HRV.

Assessment of Time and Frequency Domain Parameters of Heart Rate Variability and Interictal Cardiac Rhythm Abnormalities in Drug-naïve Patients with Idiopathic Generalized Epilepsy

Background and Purpose:

Epilepsy is a disease known to occur with autonomous phenomenons. Earlier studies indicate decreased heart rate variability (HRV) during ictal and interictal periods among epilepsy patients. In this study, we aim to investigate cardiac rhythm abnormalities and HRV during interictal period between drug-naïve patients with idiopathic generalized epilepsy (IGE) and healthy control group.

Methods:

Twenty-six patients with IGE and 26 healthy individuals included in the study. In order to eliminate any structural cardiac pathology, transthoracic echocardiography was performed in all subjects and time and frequency domain parameters of HRV were evaluated after 24-hour rhythm holter monitoring.

Results:

Between two groups, no significant difference was detected in terms of mean heart rate and maximum duration between the start of the Q waves and the end of the T waves (QT intervals). In the time domain analysis of HRV, no statically significant difference was detected for standard deviation of all R - R intervals and root-mean-square of successive differences between patient and control group (p = 0,070 and p = 0,104 respectively). In the frequency domain analysis of HRV, patients tended to display lower total power and very low frequency power than did healthy subjects, but the differences were not statistically significant.

Conclusions:

Our results suggest that there is no major effect of the epilepsy on HRV in patients with IGE. It should be emphasized that, in this study, HRV was evaluated only in patients with IGE and that the results are not proper to be generalized for patients with partial seizures.

Sudden unexpected death in epilepsy genetics: Molecular diagnostics and prevention

Epidemiologic studies clearly document the public health burden of sudden unexpected death in epilepsy (SUDEP). Clinical and experimental studies have uncovered dynamic cardiorespiratory dysfunction, both interictally and at the time of sudden death due to epilepsy. Genetic analyses in humans and in model systems have facilitated our current molecular understanding of SUDEP. Many discoveries have been informed by progress in the field of sudden cardiac death and sudden infant death syndrome. It is becoming apparent that SUDEP genomic complexity parallels that of sudden cardiac death, and that there is a pauci1ty of analytically useful postmortem material. Because many challenges remain, future progress in SUDEP research, molecular diagnostics, and prevention rests in international, collaborative, and transdisciplinary dialogue in human and experimental translational research of sudden death.

Heart rate and blood pressure in sudden unexpected death in epilepsy (SUDEP)

Epilepsy is associated with interictal and ictal autonomic dysfunction. Seizures can immediately cause increases in blood pressure (BP) and heart rate (HR). However, it is unknown whether uncontrolled seizures, particularly when frequent, might chronically elevate the BP or HR. Additionally, it is unknown whether the interictal BP and HR is altered in individuals who are at risk for SUDEP, compared with other individuals with epilepsy. SUDEP often occurs in patients with highly refractory epilepsy. Such individuals might be at risk for a state of chronically heightened sympathetic tone, which might affect the HR and BP interictally. This study compared the resting awake interictal HR and BP in individuals who subsequently died due to SUDEP and compared these to HR and BP in two control epilepsy groups (refractory and controlled). While the overall HR and BP are similar between groups, there is a trend toward a higher diastolic BP and more stable HR in individuals who subsequently died due to SUDEP, compared with epilepsy controls. These data suggest that there may be specific types of interictal autonomic dysfunction in individuals at risk for SUDEP. Such abnormalities might serve as markers for those at elevated risk for SUDEP.

Ictal tachycardia: the head-heart connection

Epileptic seizures can lead to changes in autonomic function affecting the sympathetic, parasympathetic, and enteric nervous systems. Changes in cardiac signals are potential biomarkers that may provide an extra-cerebral indicator of ictal onset in some patients. Heart rate can be measured easily when compared to other biomarkers that are commonly associated with seizures (e.g., long-term EEG), and therefore it has become an interesting parameter to explore for detecting seizures. Understanding the prevalence and magnitude of heart rate changes associated with seizures, as well as the timing of such changes relative to seizure onset, is fundamental to the development and use of cardiac based algorithms for seizure detection. We reviewed 34 articles that reported the prevalence of ictal tachycardia in patients with epilepsy. Scientific literature supports the occurrence of significant increases in heart rate associated with ictal events in a large proportion of patients with epilepsy (82%) using concurrent electroencephalogram (EEG) and electrocardiogram (ECG). The average percentage of seizures associated with significant heart rate changes was similar for generalized (64%) and partial onset seizures (71%). Intra-individual variability was noted in several articles, with the majority of studies reporting significant increase in heart rate during seizures originating from the temporal lobe. Accurate detection of seizures is likely to require an adjustable threshold given the variability in the magnitude of heart rate changes associated with seizures within and across patients.

Synchronization analysis between heart rate variability and EEG activity before, during, and after epileptic seizure

An innovative concept for synchronization analysis between heart rate (HR) components and rhythms in EEG envelopes is represented; it applies time-variant analyses to heart rate variability (HRV) and EEG, and it was tested in children with temporal lobe epilepsy (TLE). After a removal of ocular and movement-related artifacts, EEG band activity was computed by means of the frequency-selective Hilbert transform providing envelopes of frequency bands. Synchronization between HRV and EEG envelopes was quantified by Morlet wavelet coherence. A surrogate data approach was adapted to test for statistical significance of time-variant coherences. Using this processing scheme, significant coherence values between a HRV low-frequency sub-band (0.08–0.12 Hz) and the EEG δ envelope (1.5–4 Hz) occurring both in the preictal and early postictal periods of a seizure can be shown. Investigations were performed for all electrodes at 20-s intervals and for selected electrode pairs (T3÷C3, T4÷C4) in a time-variant mode. Synchronization was more pronounced in the group of right hemispheric TLE patients than in the left hemispheric group. Such a group-specific augmentation of synchronization confirms the hypothesis of a right hemispheric lateralization of sympathetic cardiac control of the low-frequency HRV components.

Heart rate variability in normal and pathological sleep

Sleep is a physiological process involving different biological systems, from molecular to organ level; its integrity is essential for maintaining health and homeostasis in human beings. Although in the past sleep has been considered a state of quiet, experimental and clinical evidences suggest a noteworthy activation of different biological systems during sleep. A key role is played by the autonomic nervous system (ANS), whose modulation regulates cardiovascular functions during sleep onset and different sleep stages. Therefore, an interest on the evaluation of autonomic cardiovascular control in health and disease is growing by means of linear and non-linear heart rate variability (HRV) analyses. The application of classical tools for ANS analysis, such as HRV during physiological sleep, showed that the rapid eye movement (REM) stage is characterized by a likely sympathetic predominance associated with a vagal withdrawal, while the opposite trend is observed during non-REM sleep. More recently, the use of non-linear tools, such as entropy-derived indices, have provided new insight on the cardiac autonomic regulation, revealing for instance changes in the cardiovascular complexity during REM sleep, supporting the hypothesis of a reduced capability of the cardiovascular system to deal with stress challenges. Interestingly, different HRV tools have been applied to characterize autonomic cardiac control in different pathological conditions, from neurological sleep disorders to sleep disordered breathing (SDB). In summary, linear and non-linear analysis of HRV are reliable approaches to assess changes of autonomic cardiac modulation during sleep both in health and diseases. The use of these tools could provide important information of clinical and prognostic relevance.

Anticonvulsant and antiarrhythmic effects of nifedipine in rats prone to audiogenic seizures

Calcium ion participates in the regulation of neural transmission and the presynaptic release of neurotransmitters. It is also involved in epileptic events, cardiac arrhythmias and abnormal conduction of stimuli. The purpose of the present study was to evaluate the effects of nifedipine, a calcium channel blocker, on epileptic seizures and on reperfusion arrhythmias in rats prone to audiogenic epileptic seizures (Wistar audiogenic rats, WAR) and in normal Wistar rats (N = 6/group). The seizure severity index was applied after an intraperitoneal injection of 20 or 40 mg/kg nifedipine (N20 and N40 groups, respectively). The Langendorff technique was used to analyze cardiac function, as well as the incidence and severity of the reperfusion arrhythmias after ligature and release of the left coronary artery in rats treated or not with nifedipine. We found that nifedipine treatment decreased seizure severity (0.94 ± 0.02 for WAR; 0.70 ± 0.10 for WAR + N20; 0.47 ± 0.08 for WAR + N40) and increased the latent period (13 ± 2 s for WAR; 35 ± 10 s for WAR + N20; 48 ± 7 s for WAR + N40) for the development of seizures in WAR. Furthermore, the incidence and severity of the reperfusion arrhythmias were lower in WAR and normal Wistar rats injected with nifedipine. In WAR, these effects were mediated, at least in part, by a decrease in heart rate. Thus, our results indicate that nifedipine may be considered to be a potential adjuvant drug for epilepsy treatment, especially in those cases associated with cardiac rhythm abnormalities.

Interictal autonomic abnormalities in idiopathic Rolandic epilepsy

We investigated 50 young patients with a diagnosis of Rolandic Epilepsy (RE) for the presence of abnormalities in autonomic tone compared with 50 young patients with idiopathic generalized epilepsy with absences and 50 typically developing children of comparable age. We analyzed time domain (N-N interval, pNN50) and frequency domain (High Frequency (HF), Low Frequency (LF) and LF/HF ratio) indices from ten-minute resting EKG activity. Patients with RE showed significantly higher HF and lower LF power and lower LF/HF ratio than controls, independent of the epilepsy group, and did not show significant differences in any other autonomic index with respect to the two control groups. In RE, we found a negative relationship between both seizure load and frequency of sleep interictal EEG abnormalities with parasympathetic drive levels. These changes might be the expression of adaptive mechanisms to prevent the excessive sympathetic drive seen in patients with refractory epilepsies.

Changes in autonomic control of the cardiovascular system in the Wistar audiogenic rat (WAR) strain

We evaluated autonomic cardiovascular modulation and baroreflex control of heart rate (HR) in a particular epileptic rat strain, Wistar audiogenic rats (WARs). We studied spontaneous baroreflex sensitivity as well as reflex changes in HR evoked by phenylephrine/nitroprusside-induced changes in arterial pressure (AP). Atropine and propranolol were used to measure cardiac autonomic tone. AP and pulse interval (PI) variability analysis were performed in the time and frequency domains (FFT spectral analysis) to evaluate cardiovascular sympatovagal modulation in WARs. AP and HR were higher in WARs (109±2 mm Hg and 366±9 bpm) than in Wistar control rats (101±2 mm Hg and 326±10 bpm). The power of the low-frequency band of both AP and PI spectra, a marker of sympathetic modulation, was higher in WARs than in Wistar control rats. The high-frequency power of the PI spectra in normalized units, which is linked to cardiac vagal modulation, was lower in WARs. Both WARs and Wistar control rats had similar vagal tone (91±13 bpm vs 94±11 bpm, respectively), but sympathetic tone was higher in WARs (30±4 bpm vs 14±4 bpm). No differences were detected in the gain of evoked (1.32±0.1 ms/mm Hg vs 1.35±0.2 ms/mm Hg) or spontaneous (1.34±0.2 ms/mm Hg vs 2.04±0.2 ms/mm Hg) baroreflex sensitivity. The higher AP and HR and the autonomic imbalance (sympathetic predominance) in WARs might be associated with an increased risk of life-threatening cardiovascular events in this strain.

Pre-ictal autonomic changes

Autonomic measures frequently alter with seizure activity and with brain state and so theoretically, there could be pre-ictal changes in autonomic function. However, there are considerable confounders. First, the measurement of autonomic function is not straightforward; heart rate and measures derived form heart rate have been those that have used the most in assessing changes in autonomic function. Second, autonomic function can vary considerably over the 24h cycle and can change suddenly depending on internal and external stimuli (e.g. fear, pain) and so any measures of changes in autonomic function will lose specificity. Third, changes in autonomic function in response to seizures, depends upon the individual, seizure type and spread of the seizure and even then can vary from seizure to seizure in the same individual. The idea that there will be well-defined, unique autonomic changes that occur in the pre-ictal period is very unlikely. These factors make it unlikely that autonomic function monitoring can be used successfully as a means of seizure prediction. However, in sleep, changes in autonomic function relate to changes in arousal state and since such states and the transition between such states may predict seizure occurrence in certain individuals, autonomic function could be a helpful determinant of seizure risk at certain stages of sleep. This hypothesis has, however, yet to be tested.

Evaluation of Heart Rate Variation Analysis during Rest and Tilting in Patients with Temporal Lobe Epilepsy

Objective. To evaluate spectral heart rate (HR) variation using short-term ECG recordings at rest and during the tilt table test. Methods. The values of spectral components of total power (TP), high-frequency power (HF), low-frequency power (LF) and LF: HF ratio were measured at rest and during the head-up tilt in patients with temporal lobe epilepsy (TLE) and their control subjects. Results. Compared to the control subjects, patients with TLE had lower HF (P < 0.05) and LF : HF ratio (P < 0.05) at rest and lower TP (P < 0.001), HF (P < 0.05), and LF (P < 0.05) during the head-up tilt. Upon changing from supine to standing position TP (P < 0.05) and LF (P < 0.05) were attenuated in patients with TLE compared to the control subjects. Conclusion. These results suggest that spectral analysis of HR variation from ECG recordings of short duration may add value to assessment of autonomic nervous system function using autonomic cardiac tests in patients with TLE.