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cardiac arrhythmias in patients with epilepsy represent an important area of clinical interest , particularly given their suspected contributions to sudden unexpected death in epilepsy ( sudep ) .
previous literature suggests that left hemispheric epileptogenic substrates are more often associated with ictal bradyarrhythmias and right hemispheric substrates with tachyarrhythmias .
we present two cases of potentially lethal asystole associated with seizures of right , rather than the expected left , hemispheric onset .
during video - eeg monitoring for seizure characterization , a 37-year - old man with nonlesional epilepsy was observed to have a seizure characterized by a feeling of dj vu followed by altered awareness during which bilateral tonic extension of the upper extremities occurred ( video  1 ) .
electrographically , the seizure demonstrated right temporal onset and remained lateralized to the right hemisphere as the seizure progressed .
ten seconds after electrographic onset , concurrent ekg showed a slow trending heart rate that culminated in asystole for 27  s. correspondingly , the eeg revealed diffuse and marked background attenuation during the period of asystole . upon recovery and stabilization of the heart rate
, the eeg background quickly normalized after 9  s ( fig .  1 ) .
subsequently , the patient sustained two more seizures associated with ictal asystole of similar duration . eventually , the patient underwent placement of a dual chamber pacemaker .
a 60-year - old woman presented with two seizures characterized by staring and altered awareness followed by left arm and leg shaking for 30  s. simultaneously , her ekg revealed an initial bradycardia followed by asystole lasting 15  s. she required cardiopulmonary resuscitation for both episodes .
brain mri revealed an enhancing lesion in the right hemisphere involving the frontal and temporal lobes , insula , thalamus , hypothalamus , and pons ( fig .  2 ) .
although her seizures were not corroborated by simultaneous eeg monitoring , the ictal semiology and imaging findings strongly support a right hemispheric epileptogenic zone .
during video - eeg monitoring for seizure characterization , a 37-year - old man with nonlesional epilepsy was observed to have a seizure characterized by a feeling of dj vu followed by altered awareness during which bilateral tonic extension of the upper extremities occurred ( video  1 ) .
electrographically , the seizure demonstrated right temporal onset and remained lateralized to the right hemisphere as the seizure progressed .
ten seconds after electrographic onset , concurrent ekg showed a slow trending heart rate that culminated in asystole for 27  s. correspondingly , the eeg revealed diffuse and marked background attenuation during the period of asystole . upon recovery and stabilization of the heart rate
, the eeg background quickly normalized after 9  s ( fig .  1 ) .
subsequently , the patient sustained two more seizures associated with ictal asystole of similar duration . eventually , the patient underwent placement of a dual chamber pacemaker .
a 60-year - old woman presented with two seizures characterized by staring and altered awareness followed by left arm and leg shaking for 30  s. simultaneously , her ekg revealed an initial bradycardia followed by asystole lasting 15  s. she required cardiopulmonary resuscitation for both episodes .
brain mri revealed an enhancing lesion in the right hemisphere involving the frontal and temporal lobes , insula , thalamus , hypothalamus , and pons ( fig .  2 ) .
although her seizures were not corroborated by simultaneous eeg monitoring , the ictal semiology and imaging findings strongly support a right hemispheric epileptogenic zone .
ictal cardiac rate changes commonly occur , with sinus tachycardia ( pulse  >  100  beats per minute ) evident in the majority of patients .
while ictal bradycardia and asystole are documented in only about 2.1% of recorded seizures , many patients who experienced such arrhythmias had potentially fatal asystole and required subsequent permanent pacemaker .
according to the lateralization hypothesis , seizures with a left - sided focus result in bradyarrhythmias , whereas seizures with a right - sided focus result in tachyarrhythmias .
selective activation of parasympathetic or sympathetic centers via the electrical propagation of seizures may explain ictal cardiac changes . in one study , electrical stimulation of
the left insular cortex resulted in bradycardia , implying that a parasympathetic - mediated pathway was involved .
conversely , stimulation of the right insular cortex induced tachycardia , implying a right hemispheric predominance in cardiac sympathetic regulation .
in contrast to this hypothesis , the two cases of ictal asystole presented here occurred with right - sided seizure foci .
other studies have shown that autonomic alterations may be more prominent in patients with right - sided versus left - sided epileptogenic zones .
interestingly , the second case demonstrated an extensive lesion involving the thalamus and cingulate  structures which have been shown to influence cardiac rhythms . furthermore , more recent studies involving 13 patients with ictal bradycardia failed to show any consistent lateralization of seizures .
in fact , 9 of the 13 patients showed bilateral electrographic activity at seizure onset . based on these previous studies as well as our present cases ,
ictal asystole may be driven by a mechanism that is more intricate than the strictly lateralized cardiomotor representation of either sympathetic or parasympathetic function .
the mechanisms underlying ictal cardiac arrhythmias remain elusive , and most patients have no underlying cardiac risk factors . frequently , ictal arrhythmias are detected incidentally during simultaneous eeg and ecg monitoring .
this diagnostic elusiveness , in the midst of a potential lethal condition , underscores the importance of clinical vigilance and the need of an enhanced diagnostic tool for early detection of this condition such that appropriate intervention may promptly ensue .
genomic biomarkers are in development , aiming to reliably detect channelopathies which may subserve dual roles in epileptogenesis as well as cardiorespiratory pathophysiology ( i.e. , neurocardiac genes ) .
there are currently no clinical guidelines pertaining to the type of epilepsy syndrome or the extent of ictal bradycardia / asystole and seizure control for which the placement of a permanent pacemaker becomes indicated . however , even in cases of apparently good seizure control , it may be intuitive to place pacemakers in patients with ictal asystole considering the gravity of a potentially lethal alternative outcome .
important investigations on the mechanisms underlying ictal cardiac arrhythmias and their clinical management are ongoing .
the following are the supplementary data related to this article.video  1cardiac asystole associated with focal seizure arising from the right temporal region .
the patient depicted in the supplementary materials provided permission for his face to be shown in the images .
ictal asystole is frequently underrecognized despite being a potentially lethal condition . 
 we report two cases of ictal asystole with right hemispheric onset . 
 these cases are unique since previous literature reports that seizures associated with bradyarrhythmias typically arise from left hemispheric foci . these cases further underscore the importance of clinical vigilance and the need of an enhanced diagnostic biomarker .