Analysis of heart rate variability and risk factors for SUDEP in patients with drug-resistant epilepsy

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

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

Interictal respiratory variability predicts severity of hypoxemia after generalized convulsive seizures

OBJECTIVE

Severe respiratory dysfunction induced by generalized convulsive seizures (GCS) is now thought to be a common mechanism for sudden unexpected death in epilepsy (SUDEP). In a mouse model of seizure-induced death, increased interictal respiratory variability was reported in mice that later died of respiratory arrest after GCS. We studied respiratory variability in epilepsy patients as a predictive tool for severity of postictal hypoxemia, a potential biomarker for SUDEP risk. We then explored the relationship between respiratory variability and central CO2 drive, measured by the hypercapnic ventilatory response (HCVR).

METHODS

We reviewed clinical, video-electroencephalography, and respiratory (belts, airflow, pulse oximeter, and HCVR) data of epilepsy patients. Mean, SD, and coefficient of variation (CV) of interbreath interval (IBI) were calculated. Primary outcomes were: (1) nadir of capillary oxygen saturation (SpO2 ) and (2) duration of oxygen desaturation. Poincaré plots of IBI were created. Covariates were evaluated in univariate models, then, based on Akaike information criteria (AIC), multivariate regression models were created.

RESULTS

Of 66 GCS recorded in 131 subjects, 30 had interpretable respiratory data. In the multivariate model with the lowest AIC value, duration of epilepsy was a significant predictor of duration of oxygen desaturation. Duration of tonic phase and CV of IBI during the third postictal minute correlated with SpO2 nadir, whereas CV of IBI during non-rapid eye movement sleep had a negative correlation. Poincaré plots showed that long-term variability was significantly greater in subjects with ≥200 s of postictal oxygen desaturation after GCS compared to those with <200 s desaturation. Finally, HCVR slope showed a negative correlation with measures of respiratory variability.

SIGNIFICANCE

These results indicate that interictal respiratory variability predicts severity of postictal oxygen desaturation, suggesting its utility as a potential biomarker. They also suggest that interictal respiratory control may be abnormal in some patients with epilepsy.

Sudden unexpected death in epilepsy: A critical view of the literature

Sudden unexpected death in epilepsy (SUDEP) is a sudden, unexpected, witnessed or unwitnessed, non-traumatic and non-drowning death, occurring in benign circumstances, in an individual with epilepsy, with or without evidence for a seizure and excluding documented status epilepticus in which postmortem examination does not reveal other causes of death. Lower diagnostic levels are assigned when cases met most or all of these criteria, but data suggested more than one possible cause of death. The incidence of SUDEP ranged from 0.09 to 2.4 per 1000 person-years. Differences can be attributed to the age of the study populations (with peaks in the 20-40-year age group) and the severity of the disease. Young age, disease severity (in particular, a history of generalized TCS), having symptomatic epilepsy, and the response to antiseizure medications (ASMs) are possible independent predictors of SUDEP. The pathophysiological mechanisms are not fully known due to the limited data available and because SUDEP is not always witnessed and has been electrophysiologically monitored only in a few cases with simultaneous assessment of respiratory, cardiac, and brain activity. The pathophysiological basis of SUDEP may vary according to different circumstances that make that particular seizure, in that specific moment and in that patient, a fatal event. The main hypothesized mechanisms, which could contribute to a cascade of events, are cardiac dysfunction (included potential effects of ASMs, genetically determined channelopathies, acquired heart diseases), respiratory dysfunction (included postictal arousal deficit for the respiratory mechanism, acquired respiratory diseases), neuromodulator dysfunction, postictal EEG depression and genetic factors.

How predictable is heart rate variability in Brazilian patients with drug-resistant mesial temporal lobe epilepsy?

This study aimed to compare heart rate variability (HRV) in patients with drug-resistant mesial temporal lobe epilepsy (MTLE) with healthy controls and to analyze their clinical and sociodemographic variables predictive for HRV. Thirty-nine consecutive patients with drug-resistant MTLE were included in the study. The control group included twenty-seven healthy participants matched by age and gender. Seven HRV indices (HR, RR, rMSSD, SDNN, LF, HF, and LF/HF) were compared between patients and controls. The clinical and sociodemographic variables independently associated with the HRV indices were identified by multiple linear regression. In comparison with controls, the patients with MTLE showed a significant reduction in RR, rMSSD, SDNN, LF, HF, and LF/HF indices (t value 1.97-5.97, p < 0.05). Multiple regression models showed that disease duration predicted 11-22% of the analyzed HRV indices. Time domain indices showed higher association with disease duration than coefficients in frequency domain. Patients with drug-resistant MTLE present cardiac autonomic tone dysfunction, showing a significant reduction in their HRV indices (RR, SDNN, rMSSD, LF, HF, and LF/HF). Disease duration has a negative association with all HRV indices. This study contributes to understanding the relationship between MTLE and the cardiac autonomic tone, with possible implications for sudden unexpected death in epilepsy.

Prolonged Video-EEG and Heart Rate Variability can Elucidate Autonomic Dysregulation in Infantile Apneic Seizures

BACKGROUND

Infantile apneic seizures (IASs) are unexpected life-threatening events. We aimed to determine the utility of prolonged video-electroencephalography (vEEG) and heart rate variability (HRV) in IAS.

METHODS

The study included seven infants with apneic seizures captured by vEEG, percutaneous oxygen saturation (SpO₂), and electrocardiography (ECG). Interictal, preictal, and postictal HRV of patients and N2 sleep HRV of 10 age-matched controls were determined.

RESULTS

We analyzed seven vEEGs (duration = 17 to 87 hours) of seven patients aged three to 13 months (mean onset age of apneic event = 6.3 months). Fifteen apneic seizures (one to five per infant) were captured. The initial apneic seizure was captured at 7.5 to 76 hours (mean = 36.6 hours) after vEEG initiation. Ictal rhythmic delta/theta/fast waves were seen over temporal (five patients), central (one), and diffuse areas (one). Ictal SpO₂ decreased between 1.5% and 90% (mean = 47.9%). Ictal decreased heart rate (HR) (six seizures) and ictal increased HR (14) was detected. Both decreased and increased HR was observed (five). The preictal low-frequency (LF)/high-frequency (HF) ratio was significantly higher than the interictal LF/HF ratio (P = 0.048). Preictal (P = 0.048), and postictal (P = 0.019) root mean square of successive differences (RMSSDs) of patients were lower than the sleep RMSSD of controls. These results indicated dominant sympathetic activity. RMSSD from interictal to preictal periods tended to be higher in IAS with decreased HR than in IAS with increased HR alone (P = 0.066). The postictal RMSSD showed tendency to be higher in IAS with decreased HR than in IAS with increased HR alone (P = 0.088). The decreased HR and increased RMSSD suggested not only sympathetic activity but also escalated parasympathetic activity in IAS.

CONCLUSIONS

Infants with unexpected apneic events should be monitored with prolonged vEEG, SpO₂, and ECG. Abnormal HRV in infants with apneic seizures might indicate additional autonomic dysregulation in IAS.

Heart Rate Variability in Insulo-Opercular Epilepsy

Background: We aimed to evaluate heart rate variability (HRV) changes in insulo-opercular epilepsy (IOE) and after insulo-opercular surgery. Methods: We analyzed 5-min resting HRV of IOE patients before and after surgery. Patients’ SUDEP-7 risk inventory scores were also calculated. Results were compared with age- and sex-matched patients with temporal lobe epilepsy (TLE) and healthy individuals. Results: There were no differences in HRV measurements between IOE, TLE, and healthy control groups (and within each IOE group and TLE group) in preoperative and postoperative periods. In IOE patients, the SUDEP-7 score was positively correlated with pNN50 (percentage of successive RR intervals that differ by more than 50 ms) (p = 0.008) and RMSSD (root mean square of successive RR interval differences) (p = 0.019). We stratified IOE patients into those whose preoperative RMSSD values were below (Group 1a = 7) versus above (Group 1b = 9) a cut-off threshold of 31 ms (median value of a healthy population from a previous study). In group 1a, all HRV values significantly increased after surgery. In group 1b, time-domain parameters significantly decreased postoperatively. Conclusions: Our results suggest that in IOE, HRV may be either decreased in parasympathetic tone or increased globally in both sympathetic and parasympathetic tones. We found no evidence that insulo-opercular surgeries lead to major autonomic dysfunction when a good seizure outcome is reached. The increase in parasympathetic tone observed preoperatively may be of clinical concern, as it was positively correlated with the SUDEP-7 score.

Heart rate variability in patients with refractory epilepsy: The influence of generalized convulsive seizures

OBJECTIVE

Patients with epilepsy, mainly drug-resistant, have reduced heart rate variability (HRV), linked to an increased risk of sudden death in various other diseases. In this context, it could play a role in SUDEP. Generalized convulsive seizures (GCS) are one of the most consensual risk factors for SUDEP. Our objective was to assess the influence of GCS in HRV parameters in patients with drug-resistant epilepsy.

METHODS

We prospectively evaluated 121 patients with refractory epilepsy admitted to our Epilepsy Monitoring Unit. All patients underwent a 48-hour Holter recording. Only patients with GCS were included (n = 23), and we selected the first as the index seizure. We evaluated HRV (AVNN, SDNN, RMSSD, pNN50, LF, HF, and LF/HF) in 5-min epochs (diurnal and nocturnal baselines; preictal - 5 min before the seizure; ictal; postictal - 5 min after the seizure; and late postictal - >5 h after the seizure). These data were also compared with normative values from a healthy population (controlling for age and gender).

RESULTS

We included 23 patients, with a median age of 36 (min-max, 16-55) years and 65% were female. Thirty percent had cardiovascular risk factors, but no previously known cardiac disease. HRV parameters AVNN, RMSSD, pNN50, and HF were significantly lower in the diurnal than in the nocturnal baseline, whereas the opposite occurred with LF/HF and HR. Diurnal baseline parameters were inferior to the normative population values (which includes only diurnal values). We found significant differences in HRV parameters between the analyzed periods, especially during the postictal period. All parameters but LF/HF suffered a reduction in that period. LF/HF increased in that period but did not reach statistical significance. Visually, there was a tendency for a global reduction in our patients' HRV parameters, namely AVNN, RMSSD, and pNN50, in each period, comparing with those from a normative healthy population. No significant differences were found in HRV between diurnal and nocturnal seizures, between temporal lobe and extra-temporal-lobe seizures, between seizures with and without postictal generalized EEG suppression, or between seizures of patients with and without cardiovascular risk factors.

SIGNIFICANCE/CONCLUSION

Our work reinforces the evidence of autonomic cardiac dysfunction in patients with refractory epilepsy, at baseline and mainly in the postictal phase of a GCS. Those changes may have a role in some SUDEP cases. By identifying patients with worse autonomic cardiac function, HRV could fill the gap of a lacking SUDEP risk biomarker.

Pre- and postoperative heart rate variability and vagus nerve stimulation in patients with drug-resistant epilepsy - A meta-analysis

OBJECTIVE

The effect of vagus nerve stimulation (VNS), an important auxiliary therapy for treating drug-resistant epilepsy (DRE), on autonomic nerve function is still controversial. Heart rate variability is a widely used indicator of autonomic nerve function. To clarify the relationship between VNS and heart rate variability (HRV), we performed a meta-analysis to systematically evaluate the effect of VNS on HRV in patients with epilepsy.

METHODS

We performed a systematic review by searching the following online databases: PubMed, Web of Science, EMBASE and the Cochrane Library. The key search terms were "vagal nerve stimulation," "epilepsy" and "heart rate variability". Other features of VNS in patients with epilepsy include postoperative changes in low-frequency (LF), high-frequency (HF) and low-frequency/high-frequency (LF/HF) heart rate variability, which were used as evaluation indices, and the Newcastle-Ottawa Quality Assessment Scale and Stata 14.0 statistical software were used for literature quality evaluation and meta-analysis.

RESULTS

Twelve studies published in English were obtained, and 229 patients with epilepsy who underwent VNS were ultimately included after elimination of duplicate articles and those that did not meet the inclusion criteria. Regarding LF heart rate variability, in the response subgroup, patients with DRE with VNS presented a lower value (-0.58) before surgery than after surgery, with a 95% confidence interval (CI) ranging from -1.00 to -0.15. For HF heart rate variability, patients with DRE with VNS had a lower value (-0.45) before surgery than after surgery in the response subgroup, with a 95% CI ranging from -0.74 to -0.17. No differences were found for LF/HF values or the LF and HF values of other subgroups.

CONCLUSION

VNS has little effect on the balance of sympathetic and parasympathetic nerve activity and would not be expected to cause cardiovascular autonomic dysfunction in patients with DRE. For patients with DRE, VNS can control seizures and has little effect on autonomic nervous function.

Left ventricular dysfunction and cardiac autonomic imbalance in children with drug-resistant epilepsy

BACKGROUND

Resistance to antiepileptic drug treatment increases the risk of comorbidities and mortality due to a cardio-autonomic imbalance and left ventricular (LV) dysfunction.

OBJECTIVE

To assess the prevalence of LV dysfunction and cardio-autonomic imbalance in children with drug-resistant epilepsy (DRE).

PATIENTS AND METHODS

This cross-sectional study included 40 children with DRE and 40 healthy age- and sex-matched controls. LV function was evaluated by M-mode, two-dimensional, pulse-wave Doppler echocardiography, and tissue Doppler imaging (TDI). Cardio-autonomic function was assessed by 24 -h Holter monitoring of heart rate variability.

RESULTS

All time domain measures were significantly lower in the epilepsy group than in the control group (all Ps<0.01). Additionally, the mean high frequency (HF) parameters were significantly lower (P = 0.035), whereas the mean low frequency (LF) parameters and the LF/HF ratio were significantly higher (P < 0.001) in the epilepsy group than in the control group. LV function did not differ between groups regarding all standard echocardiographic parameters. There was evidence of subclinical LVdysfunction by tissue doppler among the epileptic group, as evidenced by the elevated Myocardial Performance Index, isovolumetric relaxation time and mitral E/Em ratio. There was no significant correlation between the duration of epilepsy or seizure frequency with any cardiac abnormality.

CONCLUSIONS

Children with DRE exhibited cardio-autonomic and subclinical LV dysfunction, independent of the duration of epilepsy, frequency, and seizure type.

Seizures and status epilepticus may be risk factor for cardiac arrhythmia or cardiac arrest across multiple time frames

OBJECTIVE

To determine if Emergency Department (ED) or inpatient encounters for epilepsy or status epilepticus are associated with increased odds of cardiac arrhythmia or cardiac arrest over successively longer time frames.

METHODS

The State Inpatient and ED Databases (from New York, Florida, and California) are statewide datasets containing data on 97% of hospitalizations and ED encounters from these states. In this retrospective, case-crossover study, we used International Classification of Diseases, Ninth Revision, Clinical Modification codes to identify index cardiac arrhythmia encounters. Exposures were inpatient or ED encounters for epilepsy or status epilepticus. The case-crossover analysis tested whether an epilepsy or status epilepticus encounter within various case periods (1, 3, 7, 30, 60, 90, and 180 days prior to index encounter) was associated with subsequent ED or inpatient encounter for cardiac arrhythmia, as compared to control periods of equal length one year prior.

RESULTS

The odds ratio (OR) for cardiac arrhythmia after an epilepsy encounter was significant at all time intervals (OR range 2.37-3.36), and highest at 1 day after epilepsy encounter (OR 3.63, 95% confidence interval [CI] 1.66-7.93, p = 0.0013). The OR after status epilepticus was significant at 7- to 180-day intervals (OR range 2.25-2.74), and highest at 60 days (OR 2.74, CI 2.09-3.61, p < 0.0001).

SIGNIFICANCE

Epilepsy and status epilepticus events are associated with increased odds of subsequent cardiac arrhythmia or cardiac arrest over multiple chronic timeframes. Increased cardiac surveillance may be warranted to minimize morbidity and mortality in patients with epilepsy.

Cardiorespiratory findings in epilepsy: A recent review on outcomes and pathophysiology

Epilepsy is a debilitating disorder of uncontrollable recurrent seizures that occurs as a result of imbalances in the brain excitatory and inhibitory neuronal signals, that could stem from a range of functional and structural neuronal impairments. Globally, nearly 70 million people are negatively impacted by epilepsy and its comorbidities. One such comorbidity is the effect epilepsy has on the autonomic nervous system (ANS), which plays a role in the control of blood circulation, respiration and gastrointestinal function. These epilepsy-induced impairments in the circulatory and respiratory systems may contribute toward sudden unexpected death in epilepsy (SUDEP). Although, various hypotheses have been proposed regarding the role of epilepsy on ANS, the linking pathological mechanism still remains unclear. Channelopathies and seizure-induced damages in ANS-control brain structures were some of the causal/pathological candidates of cardiorespiratory comorbidities in epilepsy patients, especially in those who were drug resistant. However, emerging preclinical research suggest that neurotransmitter/receptor dysfunction and synaptic changes in the ANS may also contribute to the epilepsy-related autonomic disorders. Thus, pathological mechanisms of cardiorespiratory dysfunction should be elucidated by considering the modifications in anatomy and physiology of the autonomic system caused by seizures. In this regard, we present a comprehensive review of the current literature, both clinical and preclinical animal studies, on the cardiorespiratory findings in epilepsy and elucidate the possible pathological mechanisms of these findings, in hopes to prevent SUDEP especially in patients who are drug resistant.

The brain-heart interaction in epilepsy: implications for diagnosis, therapy, and SUDEP prevention

The influence of the central nervous system and autonomic system on cardiac activity is being intensively studied, as it contributes to the high rate of cardiologic comorbidities observed in people with epilepsy. Indeed, neuroanatomic connections between the brain and the heart provide links that allow cardiac arrhythmias to occur in response to brain activation, have been shown to produce arrhythmia both experimentally and clinically. Moreover, seizures may induce a variety of transient cardiac effects, which include changes in heart rate, heart rate variability, arrhythmias, asystole, and other ECG abnormalities, and can trigger the development of Takotsubo syndrome. People with epilepsy are at a higher risk of death than the general population, and sudden unexpected death in epilepsy (SUDEP) is the most important direct epilepsy-related cause of death. Although the cause of SUDEP is still unknown, cardiac abnormalities during and between seizures could play a significant role in its pathogenesis, as highlighted by studies on animal models of SUDEP and registration of SUDEP events. Recently, genetic mutations in genes co-expressed in the heart and brain, which may result in epilepsy and cardiac comorbidity/increased risk for SUDEP, have been described. Recognition and a better understanding of brain-heart interactions, together with new advances in sequencing techniques, may provide new insights into future novel therapies and help in the prevention of cardiac dysfunction and sudden death in epileptic individuals.

Ultra-short heart rate variability reliability for cardiac autonomic tone assessment in mesial temporal lobe epilepsy

Autonomic dysfunction in epilepsy is well-described. Heart rate variability (HRV) is a useful method to evaluate autonomic cardiac tone. Cardiac dysfunction may be involved in sudden unexpected death in epilepsy (SUDEP). HRV is a promising biomarker to enlighten the heart-brain axis role in SUDEP, but the required duration for a proper HRV recording in clinical routine remains unknown. This study aimed to verify the reliability of ultra-short HRV indices to evaluate cardiac autonomic tone in patients with epilepsy (PWE). Thirty-nine patients with mesial temporal lobe epilepsy (MTLE) had electrocardiogram recordings during the first day of video-EEG. Pearson's correlations were performed to evaluate the association between ultra-short HRV indices (five 1-min and five 30-s epochs) with standard time recording (5-min) and ANOVA compared the differences between mean HRV indices across epochs. Time domain (TD) indices showed higher mean r values when compared to frequency domain (FD) indices in 1-min (TD: r 0.80-0.99, FD: r 0.61-0.95) and 30-s epochs (TD: r 0.69-0.99, only high frequency: mean r values of 0.96). ANOVA evidenced that standard deviation of RR intervals and very low frequency means had at least 3 epochs significantly different for 1-min and 30-s epochs. Root mean square of the successive differences of RR intervals (rMSSD) presented higher Pearson's coefficient values and lower percentage of variation at 1-min or 30-s epochs in comparison to other HRV indices. In conclusion, rMSSD is the most reliable ultra-short HRV index for cardiac autonomic tone assessment in MTLE. The prognostic value of ultra-short HRV for cardiovascular risk evaluation in epilepsy remains to be determined in future studies.

Cardiac Autonomic Dysfunction and Risk of Sudden Unexpected Death in Epilepsy

OBJECTIVE

We aimed to test whether patients who died of sudden unexpected death in epilepsy (SUDEP) had an abnormal cardiac autonomic response to sympathetic stimulation by hyperventilation.

METHODS

We conducted a retrospective, observational, case-control study of a group of patients who died of SUDEP and controls who were matched to the patients for epilepsy type, drug resistance, sex, age at EEG recording, age at onset of epilepsy, and duration of epilepsy. We analyzed the heart rate (HR) and HR variability (HRV) at rest and during and after hyperventilation performed during the patient's last EEG recording before SUDEP. In each group, changes over time in HRV indexes were analyzed with linear mixed models.

RESULTS

Twenty patients were included in each group. In the control group, the HR increased and the root mean square of successive RR-interval differences (RMSSD) decreased during the hyperventilation and then returned to the baseline values. In the SUDEP group, however, the HR and RMSSD did not change significantly during or after hyperventilation. A difference in HR between the end of the hyperventilation and 4 minutes after its end discriminated well between patients with SUDEP and control patients (area under the receiver operating characteristic curve 0.870, sensitivity 85%, specificity 75%).

CONCLUSION

Most of patients with subsequent SUDEP have an abnormal cardiac autonomic response to sympathetic stimulation through hyperventilation. An index reflecting the change in HR on hyperventilation might be predictive of the risk of SUDEP and could be used to select patients at risk of SUDEP for inclusion in trials assessing protective measures.

The risk of cardiac mortality in patients with status epilepticus: A 10-year study using data from the Centers for Disease Control and Prevention (CDC)

OBJECTIVE

To explore whether status epilepticus affected cardiac mortality.

METHODS

We used the 2008-2017 multicause mortality data of the Centers for Disease Control and Prevention Wide-ranging Online Data for Epidemiological Research. The status epilepticus group included patients whose death certificates mentioned status epilepticus as contributing to death. The non-status epilepticus group included patients whose death certificates mentioned epilepsy, other and unspecified convulsions, febrile convulsions, or post-traumatic seizures, as contributing to death. The outcomes for evaluation were death certificates that indicated that myocardial infarction, arrhythmia, heart failure, or cardiac arrest (CA) was the immediate cause of death. The numbers of deaths and population sizes by categorical demographics were recorded and subjected to multiple logistic regression analysis.

RESULTS

Among the 14,487 death certificates in status epilepticus group; 3080 patients (21.3%) died of CA. When clinical records were compared to autopsy data, females were at a lower risk of myocardial infarction (odds ratio [OR]: 0.55, 95% confidence interval [CI]: 0.51-0.61). Patients aged 45-65 years and older than 65 years were at a higher risk of developing all four cardiac complications. Status epilepticus was associated with higher risks of arrhythmia (OR: 1.55, 95% CI: 1.11-2.15) and CA (OR: 4.34, 95% CI: 3.49-5.39) but a reduced risk of myocardial infarction (OR: 0.42, 95% CI: 0.30-0.57) as the cause of immediate death.

CONCLUSION

The frequency of CA in patients with status epilepticus increased between 2008 and 2017. Male and elderly patients were at a higher risk of cardiogenic mortality.

Ictal and Interictal Cardiac Manifestations in Epilepsy. A Review of Their Relation With an Altered Central Control of Autonomic Functions and With the Risk of SUDEP

There is a complex interrelation between epilepsy and cardiac pathology, with both acute and long-term effects of seizures on the regulation of the cardiac rhythm and on the heart functioning. A specific issue is the potential relation between these cardiac manifestations and the risk of Sudden and Unexpected Death in Epilepsy (SUDEP), with unclear respective role of centrally-control ictal changes, long-term epilepsy-related dysregulation of the neurovegetative control and direct effects on the heart function. In the present review, we detailed available data about ictal cardiac changes, along with interictal cardiac manifestations associated with long-term functional and structural alterations of the heart. Pathophysiological mechanisms of these cardiac changes are discussed, with a specific focus on central mechanisms and the investigation of a possible deregulation of the central control of autonomic functions in addition to the role of catecholamine and hypoxemia on heart.

Children with refractory epilepsy demonstrate alterations in myocardial strain

OBJECTIVE

To test whether children with epilepsy have impairments in myocardial mechanics compared to controls without epilepsy.

METHODS

Children with refractory epilepsy with epilepsy duration of at least 3 years underwent echocardiography including conventional measurements and speckle tracking to assess longitudinal and circumferential strain. Parent-completed surveys, capturing critical aspects of the children's seizure history and cardiac risk factors, complemented retrospective chart reviews, which also included antiepileptic drug history. Normal echocardiograms from controls, matched for age and gender, were obtained from our institutional database and evaluated for strain.

RESULTS

Forty-one patients (median age = 10 years, interquartile range [IQR] = 5-15; 58.5% male) were enrolled. Epilepsy etiology included genetic (n = 26), structural (n = 6), genetic and structural (n = 5), infection (n = 3), and unknown (n = 1). No cardiac structural abnormalities were identified. Both longitudinal and circumferential strain were impaired (P < .03) in patients compared to controls (median [IQR] = 22.7% [21.2-24.2] vs 23.6% [22.2-26.1] and 22.0% [20.3-25.4] vs 24.5% [22.3-27.0], respectively), indicating decreased myocardial deformation/contraction. Shortening fraction was higher in patients (37.6% [35.7-39.7] vs 34.9% [32.5-38.7], P = .009); mitral valve E wave inflow velocity (84.8 cm/s [78.4-92.8] vs 97.2 cm/s [85.9-105.8], P = .005) and tissue Doppler lateral E' wave (13.9 cm/s [12.3-16.1] vs 17.3 cm/s [15.4-18.5], P < .001) were decreased compared to controls. Findings were similar in the pairs with epilepsy patients distinguished by the ability to independently ambulate. There was no difference between patients and controls in ejection fraction. Among the epilepsy patients, there were no associations between cardiac measurements and epilepsy characteristics, including seizure type and frequency and cardiotoxic antiseizure medication exposure after correction for multiple comparisons.

SIGNIFICANCE

Children with refractory epilepsy had impaired systolic ventricular strain compared to controls, not correlated with epilepsy history. Further studies are needed to determine the significance of these changes.

Cardiovascular complications of epileptic seizures

Seizure disorders are associated with multisystem complications. Cardiovascular complications account for a significant proportion of morbidity and mortality in these patients. As such, particular attention must be paid to the incidence of cardiovascular complications especially in populations at increased risk. The background for cardiac dysfunction lies in the interplay of genetic/molecular, autonomic, and iatrogenic factors that contribute to its onset. The purpose of this review was to summarize the state of literature in the last decade with regard to cardiac complications of epileptic seizures in order to increase awareness of short- and long-term debilitating cardiac complications as well as facilitate informed clinical decision-making. Taken together, the evidence provided in this review suggests that cardiac dysfunction following seizures should not be viewed as a separate entity but as an important complication of epileptic seizures. Appropriate cardiac therapy should be instituted in the postictal medical management of epileptic seizures. In acute states, postictal cardiac troponinemia (elevated cTn) should be worked up. Longer-term, monitoring for the development of cardiac structural and functional abnormalities is prudent.

Heart Rate Variability Parameters During Psychogenic Non-epileptic Seizures: Comparison Between Patients With Pure PNES and Comorbid Epilepsy

Introduction: Psychogenic non-epileptic seizures (PNES) may resemble epileptic seizures. There are few data about ictal ANS activity alterations induced by PNES in patients with pure PNES (pPNES) compared to PNES with comorbid epilepsy (PNES/ES). We aimed to compare heart rate variability (HRV) parameters and hence autonomic regulation in PNES in epileptic and non-epileptic patients.

Methods: We obtained HRV data from video-electroencephalography recordings in 22 patients presenting PNES (11 pPNES and 11 PNES/ES) in awake, and supine states. We calculated HRV parameters in both time and frequency domains including low frequency (LF) power, high frequency power (HF), LF/HF ratio, square root of the mean of the sum of the squares of differences between adjacent R wave intervals (RMSSD) and the standard deviation of all consecutive R wave intervals (SDNN). We also evaluated approximate entropy (ApEn), cardiosympathetic index (CSI), and cardiovagal index (CVI). Four conditions were considered: basal condition (BAS), before PNES (PRE), during PNES (ICT) and after PNES (POST).

Results: HRV analysis showed significantly higher ICT LF and LF/HF ratio vs. each condition. We also found higher POST HF vs. PRE and BAS, lower RRI in ICT vs. each condition and PRE vs. BAS. POST RMSSD was significantly higher compared to all other states. ICT CSI was significantly higher compared to all other states, whereas CSI was significantly lower in POST vs. PRE and PRE CVI lower than ICT and higher in POST vs. BAS and PRE. Also, ICT ApEn was lower than in all other states. Higher LF in pPNES vs. PNES/ES was also evident when compared across groups.

Significance: A few studies examined HRV alterations in PNES, reporting high sympathetic tone (although less evident than in epileptic seizures). Our data suggest a sympathetic overdrive before and during PNES followed by a post-PNES increase in vagal tone. A sympathovagal imbalance was more evident in pPNES as compared to PNES/ES.

24-hour Holter findings in infants with in-utero exposure to the Zika virus: a series of cases

Severe neurological problems and other special manifestations such as high prevalence of structural cardiac changes has been described in infants vertically exposed to the Zika virus (ZIKV) and has been called congenital Zika virus syndrome (CZS). Previous studies have shown that the 24-hour Holter heart rate variability (HRV) analysis allows the prediction of worse outcomes in infants with neurological impairment and higher risk of sudden infant death syndrome (SIDS), hypertension, diabetes mellitus and other cardiovascular diseases. This study describes the 24-hour Holter findings of infants with confirmed vertical exposure to the ZIKV by positive polymerase chain reaction (PCR) assays in the mother's blood during pregnancy and/or in the urine or cerebrospinal fluid of the newborn. Data analysis was descriptive and included two subgroups according to the presence of fetal distress, positive PCR to ZIKV in the newborn, CZS and severe microcephaly. Heart rate, pauses, arrhythmias, ST segment and QT interval analyses and HRV evaluation through R-R, SDNN, pNN50 and rMMSD were described. The Mann-Whitney test was performed to assess differences between the two subgroups. The sample consisted of 15 infants with a mean age of 16 months, nine of whom were male. No arrhythmias or QT interval changes were observed. The comparison of HRV through the Mann-Whitney test showed a significant difference between patients with and without CZS, with and without severe microcephaly, with lower HRV in the groups with severe microcephaly and CZS. The study suggests that there is an increased risk of SIDS and cardiovascular diseases in this group of patients.

Biomarkers of seizure severity derived from wearable devices

Besides triggering alarms, wearable seizure detection devices record a variety of biosignals that represent biomarkers of seizure severity. There is a need for automated seizure characterization, to identify high-risk seizures. Wearable devices can automatically identify seizure types with the highest associated morbidity and mortality (generalized tonic-clonic seizures), quantify their duration and frequency, and provide data on postictal position and immobility, autonomic changes derived from electrocardiography/heart rate variability, electrodermal activity, respiration, and oxygen saturation. In this review, we summarize how these biosignals reflect seizure severity, and how they can be monitored in the ambulatory outpatient setting using wearable devices. Multimodal recording of these biosignals will provide valuable information for individual risk assessment, as well as insights into the mechanisms and prevention of sudden unexpected death in epilepsy.

The Epileptic Heart: Concept and clinical evidence

Sudden unexpected death in epilepsy (SUDEP) is generally considered to result from a seizure, typically convulsive and usually but not always occurring during sleep, followed by a sequence of events in the postictal period starting with respiratory distress and progressing to eventual cardiac asystole and death. Yet, recent community-based studies indicate a 3-fold greater incidence of sudden cardiac death in patients with chronic epilepsy than in the general population, and that in 66% of cases, the cardiac arrest occurred during routine daily activity and without a temporal relationship with a typical seizure. To distinguish a primarily cardiac cause of death in patients with epilepsy from the above description of SUDEP, we propose the concept of the "Epileptic Heart" as "a heart and coronary vasculature damaged by chronic epilepsy as a result of repeated surges in catecholamines and hypoxemia leading to electrical and mechanical dysfunction." This review starts with an overview of the pathophysiological and other lines of evidence supporting the biological plausibility of the Epileptic Heart, followed by a description of tools that have been used to generate new electrocardiogram (EKG)-derived data in patients with epilepsy that strongly support the Epileptic Heart concept and its propensity to cause sudden cardiac death in patients with epilepsy independent of an immediately preceding seizure.

Risks and predictive biomarkers of sudden unexpected death in epilepsy patient

PURPOSE OF REVIEW

The current review updates our knowledge regarding sudden unexpected death in epilepsy patient (SUDEP) risks, risk factors, and investigations of putative biomarkers based on suspected mechanisms of SUDEP.

RECENT FINDINGS

The overall incidence of SUDEP in adults with epilepsy is 1.2/1000 patient-years, with surprisingly comparable figures in children in recently published population-based studies. This risk was found to decrease over time in several cohorts at a rate of -7% per year, for unknown reasons. Well established risk factors include frequency of generalized tonic-clonic seizures, while adding antiepileptic treatment, nocturnal supervision and use of nocturnal listening device appear to be protective. In contrast, recent data failed to demonstrate the predictive value of heart rate variability, periictal cardiorespiratory dysfunction, and postictal generalized electroencephalography suppression. Preliminary findings suggest that brainstem and thalamic atrophy may be associated with a higher risk of SUDEP. Novel experimental and human data support the primary role of generalized tonic-clonic seizure-triggered respiratory dysfunction and the likely contribution of altered brainstem serotoninergic neurotransmission, in SUDEP pathophysiology.

SUMMARY

Although significant progress has been made during the past year in the understanding of SUDEP mechanisms and investigation of numerous potential biomarkers, we are still missing reliable predictors of SUDEP beyond the well established clinical risk factors.

Let's talk SUDEP

Sudden unexplained death in epilepsy (SUDEP) is a devastating complication of epilepsy which was under-recognized in the recent past despite its clear importance. In this review, we examine the definition of SUDEP, revise current pathophysiological theories, discuss risk factors and preventative measures, disclose tools for appraising the SUDEP risk, and last but not least dwell upon announcing and explaining the SUDEP risk to the patients and their caretakers. We aim to aid the clinicians in their responsibility of knowing SUDEP, explaining the SUDEP risk to their patients in a reasonable and sensible way and whenever possible, preventing SUDEP. Future studies are definitely needed to increase scientific knowledge and awareness related to this prioritized topic with malign consequences.

Brainstem atrophy in focal epilepsy destabilizes brainstem-brain interactions: Preliminary findings

Background

MR Imaging has shown atrophy in brainstem regions that were linked to autonomic dysfunction in epilepsy patients. The brainstem projects to and modulates the activation state of several wide-spread cortical/subcortical regions. The goal was to investigate 1. Impact of brainstem atrophy on gray matter connectivity of cortical/subcortical structures and autonomic control. 2. Impact on the modulation of cortical/subcortical functional connectivity.

Methods

11 controls and 18 patients with non-lesional focal epilepsy (FE) underwent heart rate variability (HRV) measurements and a 3 T MRI (T1 in all subjects, task-free fMRI in 7 controls/ 12 FE). The brainstem was extracted, and atrophy assessed using deformation-based-morphometry. The age-corrected z-scores of the mean Jacobian determinants were extracted from 71 5x5x5 mm grids placed in brainstem regions associated with autonomic function. Cortical and non-brainstem subcortical gray matter atrophy was assessed with voxel-based-morphometry and mean age corrected z-scores of the modulated gray matter volumes extracted from 380 cortical/subcortical rois. The profile similarity index was used to characterize the impact of brainstem atrophy on gray matter connectivity. The fMRI was preprocessed in SPM12/Conn17 and the BOLD signal extracted from 398 ROIs (16 brainstem). A dynamic task-free analysis approach was used to identify activation states. Connectivity HRV relationship were assessed with Spearman rank correlations.

Results

HRV was negatively correlated with reduced brainstem right hippocampus/parahippocampus gray matter connectivity in controls (p < .05, FDR) and reduced brainstem to right parietal cortex, lingual gyrus, left hippocampus/amygdala, parahippocampus, temporal pole, and bilateral anterior thalamus connectivity in FE (p < .05, FDR). Dynamic task-free fMRI analysis identified 22 states. The strength of the functional brainstem/cortical connectivity of state 15 was negatively associated with HRV (r = −0.5, p = .03) and positively with decreased brainstem-cortical (0.49, p = .03) gray matter connectivity.

Conclusion

The findings of this small pilot study suggest that impaired brainstem-cortex gray matter connectivity in FE negatively affects the brainstem's ability to control cortical activation.

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Brainstem and cortical/subcortical gray matter (gm) connectivity is impaired in FE.

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FE is associated with an abnormal brain activation state in the interictal state.

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The severity of the gm impairment and of the abnormal brain state are correlated.

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GM connectivity impairment and abnormal brain activity affect HRV.

Impact of repeated kindled seizures on heart rate rhythms, heart rate variability, and locomotor activity in rats

Although an impact of epilepsy on circadian rhythmicity is well-recognized, there are profound gaps in our understanding of the influence of seizures on diurnal rhythms. The effect on activity levels and heart rate is of particular interest as it might contribute to the disease burden. The kindling model with telemetric transmitter implants provides excellent opportunities to study the consequences of focal and generalized seizures under standardized conditions. Data from kindled rats with generalized seizures revealed an increase in activity and heart rate during the resting phase. Total and short-term heart rate variabilities were not affected by electrode implantation or seizure induction. Ictal alterations in heart rate associated with generalized seizures were characterized by a biphasic bradycardia with an immediate drop of heart rate followed by a transient normalization and a second more steady decrease. In conclusion, the findings demonstrate that once daily generalized seizures can exert significant effects on heart rate rhythms. Respective alterations in patients would be of relevance for patient counselling and therapeutic management. Occurrence of biphasic bradycardia associated with seizure induction suggests that the kindling model is suitable to study the consequences and the prevention of ictal bradycardia, which may pose patients at risk for sudden unexpected death.

Longitudinal change of cardiac electrical and autonomic function and potential risk factors in children with dravet syndrome

PURPOSE

This study aimed to investigate cardiac electrical and autonomic function, the longitudinal changes, and the associated risk factors in children with Dravet syndrome (DS).

METHODS

Twenty-four children with DS (11 boys, 13 girls; mean age, 7.2 ± 2.9 years) and 21 control subjects (9 boys, 12 girls; mean age, 8.2 ± 3.0 years) were enrolled in this study. P dispersion, QTc and QTc dispersion, and heart rate variability (HRV) were evaluated using standard electrocardiography and 24-hr Holter monitoring at the initial and follow-up study of the 6-12 months intervals.

RESULTS

The DS group had significantly higher P dispersion (p = 0.017), QT and QTc dispersion values (p <  0.001 for two parameters) than the control group. Most HRV parameters, such as SDNN (p <  0.001), SDANN5 (p <  0.001), SDANN-index (p = 0.001), and RMSSD (p = 0.006) were all significantly lower in the DS group than in the control group. The mean values of initial QTc, QTc dispersion, and HRV parameters showed significantly increase (QTc and QTc dispersion) and decrease (HRV) in the follow-up study (mean duration: 1.2 ± 0.5 years) in 13 DS children. ± On multivariate regression analysis, epilepsy duration had an independently significant effect for the longitudinal change of QTc, QTc dispersion, and HRV.

CONCLUSIONS

DS children had significant different values of cardiac electrical and autonomic function compared with control group. Particularly, longer duration of epilepsy was significantly negative effect on the longitudinal change of cardiac autonomic function.

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.

Sign and magnitude scaling properties of heart rate fluctuations following vagus nerve stimulation in a patient with drug-resistant epilepsy

Vagus nerve stimulation (VNS) therapy has been recently incorporated in Latin America as a treatment for drug-resistant epilepsy. In particular, it is known that linear analysis and fractal parameters of heart rate variability (HRV) are able to indirectly measure cardiac autonomic activity. This case report presents a 17-year-old female with drug-resistant epilepsy implanted with a VNS device. In order to explore cardiac autonomic changes due to VNS, linear and fractal HRV indices were calculated in the presence and absence of neurostimulation. Novel fractal scaling exponents from HRV analysis were obtained from this patient and from a healthy control subject. Our results indicate that fractal indices of HRV, such as short-term scaling parameters from magnitude and sign analyses seem to be sensitive to the presence or absence of VNS, being confirmed by linear classical methods. This study shows that VNS therapy increases the complexity of cardiac fluctuations in a patient with drug-resistant epilepsy, reflecting an augmented HRV non-linearity and a diminished anticorrelated pattern in heart rate fluctuations. A potential clinical use of these parameters includes the early identification of bradycardia, sudden unexpected death (SUDEP) risk and preoperative VNS approaches. Thus, the scaling and magnitude properties of HRV have potential importance as a non-invasive and easy method for adequate diagnostic/prognostic implications in epilepsy treatment.

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.