The functions of the heart and central nervous system (CNS) are inherently interdependent, with diseases of one system usually affecting the function of the other. Neurocardiology, the study of heart and brain interactions in both health and disease, has recently developed into an important subspecialty interest of many neurologists and cardiologists.
Although regulation of the heart via the autonomic nervous system usually maintains cardiovascular homeostasis, dysfunction of the nervous system disrupts the balance. Isolated seizures can transiently influence cardiac function, and epilepsy, if not managed appropriately, can lead to serious cardiac dysfunction, though it is rare. In addition, some epilepsy treatments have potential cardiac complications, adding another level of complexity to the management of patients with epilepsy. When patients with epilepsy need to undergo cardiac surgery, the balance is especially delicate.
On the other hand, cardiovascular disease and treatments can precipitate new seizures or alter the management of pre-existing epilepsy.
Finally, many cardiovascular symptoms can imitate seizures, so extensive evaluation of both systems may be necessary for an accurate diagnosis of paroxysmal episodes.
How does cardiac disease bring on seizures?
The Rotterdam Study determined that a history of stroke or risk factors for stroke were associated with an increased lifetime risk for epilepsy.1 Embolic and hemorrhagic strokes that compress or injure the cerebral cortex probably cause more seizures than subcortical thrombotic strokes or lacunes.
Brain ischemia or infarction of any etiology can cause seizures. Structural cardiac disease and arrhythmias cause impaired or turbulent cardiac output. The result may be poor cerebral perfusion, either globally or in areas of vascular compromise. Diffuse cerebral hypoperfusion can result in epileptogenic injury to watershed areas of cerebral cortex, or to areas sensitive to oxygen deprivation, such as the hippocampus. Many different cardiac events and conditions can lower seizure threshold:
- cardiac arrest and subsequent resuscitation
- congestive heart failure
- cardiogenic shock
- congenital cardiac anomalies and conduction defects (sometimes associated with congenital CNS abnormalities causing seizures)
- cardiac surgery and other interventions
- cardiac medications
Adapted from: Boggs J. Cardiac disorders. In: Ettinger AB and Devinsky O, eds. . Managing epilepsy and co-existing disorders. Boston: Butterworth-Heinemann; 2002;39-47.
With permission from Elsevier (www.elsevier.com).