Suppressed circadian heart rate dynamics in temporal lobe epilepsy

Ictal electrocardiographic changes in children presenting with seizures

BACKGROUND

The aim of this study was to determine electrocardiographic changes in children during seizures.

METHODS

We assessed heart rate changes, RR intervals and QT changes during 47 seizures in children. Consecutive QT and RR intervals were measured for 60 s before the seizures, during the seizures and 60 s after the seizures during video electroencephalography monitoring.

RESULTS

There were 47 seizures in 18 patients. Five patients had generalized seizures and 13 patients had focal seizures. Twelve patients were male. The mean age during monitoring was 10.1 years (range 4 months-19 years). Ictal tachycardia was seen in every seizure. No ictal bradycardia was noted. There was only one dropped beat in a patient. The mean ictal heart-rate-corrected QT (QTc) interval was significantly higher than the postictal measurements (P= 0.005). Mean ictal QTc variation tended to increase during seizures and then decreased below the pre-ictal measurements in the postictal period. However these changes were statistically insignificant (P > 0.05). RR variance was significantly decreased during seizures compared to the postictal period and the standard deviation of the RR intervals was significantly decreased in the ictal period compared to the pre-ictal period (P= 0.014 and P= 0.001, respectively).

CONCLUSION

Tachycardia is the main finding in seizures in children. Ictal bradycardia and cardiac arrhythmias are very rare despite being more frequent in adults with seizures.

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

PURPOSE

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

METHOD

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

KEY FINDINGS

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

SIGNIFICANCE

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

Sudden unexpected death in epilepsy

Sudden unexpected death in epilepsy (SUDEP) refers to the sudden death of a seemingly healthy individual with epilepsy, usually occurring during, or immediately after, a tonic-clonic seizure. The frequency of SUDEP varies depending on the severity of the epilepsy, but overall the risk of sudden death is more than 20 times higher than that in the general population. Several different mechanisms probably exist, and most research has focused on seizure-related respiratory depression, cardiac arrhythmia, cerebral depression, and autonomic dysfunction. Data from a pooled analysis of risk factors indicate that the higher the frequency of tonic-clonic seizures, the higher the risk of SUDEP; furthermore, risk of SUDEP is also elevated in male patients, patients with long-duration epilepsy, and those on antiepileptic polytherapy. SUDEP usually occurs when the seizures are not witnessed and often at night. In this Seminar, we provide advice to clinicians on ways to minimise the risk of SUDEP, information to pass on to patients, and medicolegal aspects of these deaths.

Sudden unexpected death in epilepsy

Sudden unexpected death in epilepsy (SUDEP) has an incidence ranging between 0.09 and 9 per 1000 patient-years depending on the patient population and the study methodology. It is the commonest cause of death directly attributable to epilepsy, and occurs at or around the time of a seizure. The principal risk factor for SUDEP is poorly controlled generalized tonic-clonic seizures. Other risk factors include polytherapy, male sex, early age at onset of epilepsy, symptomatic etiology, and, possibly, treatment with lamotrigine. The mechanisms underlying SUDEP are poorly understood, but autonomic dysfunction, central apnea, cerebral depression, and cardiac arrthymias have all been described in animal models of SUDEP and during human seizures. Prevention of this fatal event should be aimed at optimizing control of seizures, including prompt referral for consideration of epilepsy surgery. All patients should be told about the risks of SUDEP and informed that complete seizure control appears to be the one proven way of preventing the phenomenon.

Explaining the unexplained; expecting the unexpected: where are we with sudden unexpected death in epilepsy?

Sudden death is over 20 times more frequent in people with epilepsy than the general population. The literature on clinical risk factors is now able to define individuals at the highest risk. Despite these advances in our understanding of risk, the mechanism of sudden unexpected death in epilepsy remains elusive. While it is unlikely that a single mechanism will be found to explain all deaths, there have been recent advances that identify factors that play a critical role. This review provides an update on new advances in the understanding of sudden unexpected death in epilepsy.

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.

Cardiac changes in epilepsy

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

Enhanced QT shortening and persistent tachycardia after generalized seizures

OBJECTIVE

Generalized tonic-clonic seizures (GTCS) are a major risk factor for sudden unexpected death in epilepsy (SUDEP). We investigated whether ictal/postictal cardiac features were dependent on seizure type within individual patients.

METHODS

ECG data from patients with medically refractory temporal lobe epilepsy (TLE) undergoing presurgical investigation who had both complex partial seizures and secondarily GTCS during video-EEG telemetry were retrospectively reviewed. Peri-ictal heart rate (HR), corrected QT interval (QTc), HR variability, and cardiac rhythm were assessed.

RESULTS

Twenty-five patients were included in this study. Secondarily GTCS led to higher ictal HR, persistent postictal tachycardia, and decreased postictal HR variability. Moreover, abnormal shortening of QTc occurred in 17 patients mainly during the early postictal phase and significantly more often in secondarily GTCS. Abnormal QTc prolongation occurred in 3 patients with no significant association with GTCS. Benign cardiac arrhythmias occurred in 14 patients and were independent of seizure type.

CONCLUSIONS

Our data suggest a substantial disturbance of autonomic function following secondarily generalized tonic-clonic seizures (GTCS) in patients with medically refractory temporal lobe epilepsy. The observed alterations could potentially facilitate sudden cardiac death and might contribute to the association of sudden unexpected death in epilepsy with GTCS.

Autonomic alterations and cardiac changes in epilepsy

Studies with heart rate variability have revealed interictal autonomic alterations in patients with epilepsy. In addition, epilepsy is frequently associated with ictal tachycardia or bradycardia, which sometimes precedes the onset of seizures. Ictal tachycardia is sometimes associated with electrocardiography (ECG) morphologic changes and ictal bradycardia often progresses to asystole. Such cardiac manifestations of seizures have been hypothesized as possible causes for sudden unexplained death in epilepsy (SUPEP). The present review relates to interictal and ictal cardiac manifestations of epilepsy with focus on heart rate, heart rate variability, and ECG changes. Aspects of the supporting mechanisms are discussed and attention is drawn to the interaction between central and peripheral effects, interictal autonomic conditions, ictal autonomic discharges, and administration of antiepileptic drugs in shaping the ictal cardiac changes. Because these interactions are complex and not totally understood, closer surveillance of patients and more experimental work is necessary to elucidate the mechanistic support of autonomic and cardiac changes in epilepsy, and to design better strategies to avoid their undesirable effects. It is also suggested that some of these changes could be used as predictors or markers for the onset of seizures.

Factors that affect interictal cardiovascular autonomic dysfunction in temporal lobe epilepsy: role of hippocampal sclerosis

The aim of this study was to evaluate possible factors affecting interictal cardiovascular autonomic function in temporal lobe epilepsy with complex partial seizures, paying special attention to hippocampal sclerosis. The study was carried out with 88 patients with epilepsy (22 with left hippocampal sclerosis, 22 with right hippocampal sclerosis, and 44 without hippocampal sclerosis) and 44 healthy subjects. All subjects underwent three tests of cardiac autonomic function: heart rate variation during resting activity, heart rate variation in response to deep breathing and blood pressure response to rising quickly from the supine position. Hippocampal sclerosis and disease duration were found to have significantly important effects on parasympathetic autonomic function, whereas seizure control and type of antiepileptic drug had significant effects on sympathetic autonomic function. This study shows that in addition to factors related to the chronic nature of epilepsy and antiepileptic drug use, hippocampal sclerosis may cause autonomic dysfunction during the interictal period in persons with temporal lobe epilepsy.

Sudden unexpected death in epilepsy: risk factors and potential pathomechanisms

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

The circadian rhythm and its interaction with human epilepsy: a review of literature

Knowledge on the interaction between circadian rhythm and human epilepsy is relatively poor, although if it exists, this interaction may be of value for better knowledge of pathophysiology and for timing of diagnostic procedures and therapy. It appears that human seizure occurrence may have 24-h rhythmicity, depending on the origin. These findings are endorsed by animal studies. Rats placed in constant darkness showed spontaneous limbic seizures occurring in an endogenously mediated circadian pattern. More studies are available on the influence of epilepsy on circadian rhythms. Significant differences in chronotypes between patients with different epilepsy syndromes have been found and numerous studies have described influences of epilepsy and seizures on sleep. In contrast, knowledge on (core) body temperature and clock genes in patients is minimal. Reduced heart rate variability and changed hormone levels, which are under the influence of the biological clock, have been observed in people with epilepsy. In short, large gaps in the knowledge about the interaction of circadian rhythm and human epilepsy still remain. Proposals for studies in this borderline area between the biological clock and epilepsy will be discussed.

n-3 fatty acids (fish oil) for epilepsy, cardiac risk factors, and risk of SUDEP: clues from a pilot, double-blind, exploratory study

OBJECTIVE

The goal of the work described here was to determine the effect of high-dose n-3 fatty acids (eicosapentanoic acid+docosahexanoic acid, fish oil) on several outcomes in subjects with refractory epilepsy, including seizure severity, seizure frequency, cardiac risk factors, and heart rate variability, in a pilot, exploratory planning trial.

METHODS

Pilot, randomized, double-blind two-period crossover clinical trial of high-dose fish oil (9600 mg of fish oil/day, 2880 mg of n-3 fatty acids) in 11 subjects with refractory seizures. Outcomes included seizure frequency, seizure severity, lipid panel, and heart rate variability as measured by SDNN and SDANN (defined as the standard deviation of all normal R-R intervals for 1h, and the standard deviation of all R-R intervals in each successive 5-min epoch, respectively).

RESULTS

Preliminary data identified trends towards lower seizure severity, lower triglycerides, higher HDL, and increased SDNN/SDANN in those with low SDNN/SDANN at baseline (Spearman's correlation=-0.65, P=0.03). No positive effect on seizure frequency was identified.

CONCLUSIONS

Further study of the effect of n-3 fatty acids is indicated in people with epilepsy, as favorable trends were identified on cardiac risk factors (triglycerides) and in a subgroup with low heart rate variability (low SDNN/SDANN), a marker of sudden death risk. To our knowledge, this is the first trial to explore the beneficial effects of n-3 fatty acids on cardiac risk factors and heart rate variability in people with epilepsy.

Non-invasive assessment of cardioregulatory autonomic functions in children with epilepsy

OBJECTIVES

We aimed to evaluate the interictal cardiovascular autonomic functions in pediatric patients with idiopathic epilepsy, both partial and generalized.

MATERIALS AND METHODS

The study included 25 patients with idiopathic epilepsy and 50 control subjects. Patients underwent five standardized clinical cardiovascular reflex autonomic tests [resting heart rate (HR), HR response to deep breathing and to Valsalva maneuver, the 30:15 ratio of HR response to standing, and blood pressure response to standing], as well as a 12 lead surface electrocardiogram. Heart rate variability (HRV) was tested via 24-h Holter monitoring and the time domain parameters (SDNN, PNN50, rMSDD) were assessed. Excretion of vanillyl mandelic acid and metanephrine was measured in 24-h urine collection.

RESULTS

Clinical reflex autonomic tests showed mild dysfunction in 8%, moderate dysfunction in 44% and severe dysfunction in 4% of patients. The HRV parameter, SDNN, was reduced in all age groups, while rMSDD and PNN50 were reduced only in the older age group. Metanephrine levels were significantly reduced in the patients group. Patients with uncontrolled epilepsy had a significantly higher frequency of autonomic dysfunction as assessed by clinical scoring.

CONCLUSION

Cardiac autonomic dysfunction is not uncommon in pediatric patients with epilepsy. Altered cardiovascular regulation seems to be related to the epilepsy itself rather than to the characteristics of the disorder.

Circadian Variation in Heart-Rate Variability in Localization-related Epilepsy

PURPOSE

Case-control studies of sudden unexpected death in epilepsy (SUDEP) have reported that SUDEP is more likely to occur during sleep and thus presumably during night hours. The circadian variation of heart-rate variability (HRV) might be of relevance to this risk. We examined night versus daytime HRV in patients with newly diagnosed and refractory localization-related epilepsy, assessing the effects of drug treatment and epilepsy surgery on the night/daytime HRV ratio.

METHODS

We used spectral analysis to assess HRV and calculated the night-time (00.00-05.00)/daytime (07.30-21.30) ratio of HRV in 14 patients with newly diagnosed localization-related epilepsy before and during carbamazepine (CBZ) treatment and in 21 patients with temporal lobe epilepsy before and after epilepsy surgery. Both groups were compared with age- and sex-matched controls.

RESULTS

No significant differences were found from controls in the night/daytime ratios of HRV whether compared before or after initiation of treatment with CBZ in newly diagnosed epilepsy patients. When patients were used as their own controls, night/daytime ratios of standard deviation of RR intervals (p = 0.04) and total power (p = 0.04) were significantly lower during treatment than before. Compared with those of controls, the night/daytime ratios were lower in epilepsy surgery patients before surgery [low-frequency power (p = 0.04); high-frequency power (p = 0.04)]. Night/daytime ratios did not change significantly after surgery.

CONCLUSIONS

The HRV of the patients was more affected during night-time when the risk of SUDEP seems to be highest in such patients.

Cardiac Autonomic Control in Patients with Refractory Epilepsy before and during Vagus Nerve Stimulation Treatment: A One-Year Follow-up Study

PURPOSE

To elucidate possible effect of vagus nerve stimulation (VNS) therapy on interictal heart rate (HR) variability in patients with refractory epilepsy before and after 1-year VNS treatment.

METHODS

A 24-hour electrocardiogram (ECG) was recorded at the baseline and after 12 months of VNS treatment in 14 patients with refractory epilepsy, and once in 28 healthy age- and sex-matched control subjects. Time and frequency domain measures, along with fractal and complexity measures of HR variability, were analyzed from the ECG recordings.

RESULTS

The mean value of the RR interval (p=0.008), standard deviation of N-N intervals (SDNN) (p<0.001), very-low frequency (VLF) (p<0.001), low-frequency (LF) (p=0.001), and high-frequency (HF) (p=0.002) spectral components of HR variability, and the Poincaré components SD(1) (p=0.005) and SD(2) (p<0.001) of the patients with refractory epilepsy were significantly lower than those of the control subjects before VNS implantation. The nocturnal increase in HR variability usually seen in the normal population was absent in patients with refractory epilepsy. VNS had no significant effects on any of the HR-variability indexes despite a significant reduction in the frequency of seizures.

CONCLUSIONS

HR variability was reduced, and the nocturnal increase in HR variability was not present in patients with refractory epilepsy. One-year treatment with VNS did not have a marked effect on HR variability, suggesting that impaired cardiovascular autonomic regulation is associated with the epileptic process itself rather than with recurrent seizures.