By: Siddharth Anbalagan
The Relationship Between the Heart and Brain During Epilepsy
Epilepsy is a neurological disorder characterized by relatively recurrent, unprovoked seizures influencing brain and systemic physiology. Epilepsy is often discussed solely as a central nervous system disorder; however, it also considerably impacts cardiovascular physiology, specifically within the context of understanding seizure-related risk such as cardiac arrhythmias and sudden unexpected death in epilepsy (SUDEP). Acknowledging the heart’s role in epilepsy may lead to better monitoring of cardiovascular health during seizures and the prevention of SUDEP.
Autonomic Cardiac Dysfunction Associated with Seizures
Seizures can affect the autonomic nervous system, which can affect the heart and potentially lead to distant changes in heart rhythm. Among the more common cardiac changes associated with seizure activity are ictal tachycardia (increased heart rate associated with seizure activity), bradycardia, and, though rare, asystole. Autonomic cardiac dysfunction most commonly occurs when a seizure starts in the temporal lobe with rapid pacemaker involvement, propagating to the central autonomic centers located in the insula and amygdala. This was demonstrated by Oppenheimer et al. (2006) when they applied stimulation to the right insular cortex, which often leads to greater sympathetic nervous system activity, resulting in tachycardia, whereas stimulation of the left side leads to parasympathetic activity which often results in bradycardia.
Chronic Seizures and Cardiac Pathophysiology
Over the long term, repeated seizure activity may lead to functional and structural heart changes, which primarily consist of decreased heart rate variability (HRV), lengthy QT intervals, and increased degrees of myocardial fibrosis. The terms “epileptic heart” has been used to describe chronic pathology representing these functional and structural changes associated with recurrent seizure activity (Surges et al 2012). While the physiological basis for these changes in HRV, QT intervals, and myocardial rigidity are still under investigation, such alterations in cardiac response and structure over the long-term may predispose patients to dangerous arrhythmias and likely contribute to SUDEP.
The Risk and Mechanisms Associated with SUDEP
The most serious cardiac event associated with epilepsy may be considered SUDEP, which is the leading cause of cardiovascular related death in individuals with uncontrolled or poorly controlled epilepsy. SUDEP most commonly occurs either, during or shortly after, a generalized tonic clonic seizure, and typically while the patient is asleep. While the causes of SUDEP are still being investigated, the most common hypotheses depict a fusion of postictal respiratory depression, autonomic failure, and fatal cardiac arrhythmia. Devinsky et al. (2016) reviewed cases of SUDEP and described a common story, “first apnea followed by arrest,” with frequent EEG suppression postictally.
Clinical Implications and Prevention
While the heart is traditionally not a point of focus when managing epilepsy, cardiac arrest and SUDEP are genuinely life-threatening conditions in patients with epilepsy. Cardiac monitoring is presenting more as a vital part of epilepsy management, as Holter monitors, implantable loop recorders, and wearable seizure detection devices will assist in understanding risk through heart activity and the potential of dangerous rhythm fluctuations during seizures. Furthermore, neurologists and cardiologists, among other disciplines, should work in collaboration and teamwork in a clinical setting to develop, integrate, and implement clinical care plans for treatment as well as intervene early to potentially limit SUDEP.
Conclusion
Epilepsy does not occur purely in the brain; it occurs systemically in relation to the heart in multiple manners due to autonomic pathways and structural pathway from multiple zones. Understanding that seizures can cause involvement with cerebral and cardiovascular function represents an important area of study with significant clinical implications. By understanding and addressing these delicate variations, healthcare workers can improve their understanding of risk mechanisms that can help SUDEP, but more importantly target those who are truly at risk.
References
Devinsky, O., Hesdorffer, D. C., Thurman, D. J., Lhatoo, S., & Richerson, G. (2016). Sudden unexpected death in epilepsy: Epidemiology, mechanisms, and prevention. The Lancet Neurology, 15(10), 1075–1088. https://doi.org/10.1016/S1474-4422(16)30158-2
Oppenheimer, S. M. (2006). Cerebrogenic cardiac arrhythmias: Cortical lateralization and clinical significance. Clinical Autonomic Research, 16(1), 6–11.https://doi.org/10.1007/s10286-006-0284-1
Surges, R., & Sander, J. W. (2012). Sudden unexpected death in epilepsy: Mechanisms, prevalence, and prevention. Current Opinion in Neurology, 25(2), 201–207. https://doi.org/10.1097/WCO.0b013e328351c5b7
