Cardiac arrhythmias have been recorded during and after seizures. Bradyarrhythmias may occur with temporal lobe foci,34termed the ictal bradycardia syndrome.35 Most observed arrhythmias, such as premature atrial and ventricular contractions and beat-to-beat variations in R-R intervals, are clinically benign.36 Photic stimulation, however, can trigger either benign sinus tachycardia or clinically significant bradycardia with sinus arrest requiring cardiopulmonary resuscitation.37
Sinus tachycardia is the rhythm most often seen intra-ictally. It is a normal stress-induced sympathetic response, which sometimes is mistakenly categorized as an arrhythmia.38 In fact, the failure to develop sinus tachycardia with a prolonged seizure indicates cardiovascular dysfunction or incompetence of the autonomic response to seizures.
Arrhythmias are less common than repolarization and conduction abnormalities.39,40 Such functional cardiac electrical changes may impart instability to ventricular function and lower the threshold for ventricular fibrillation and tachycardia. In the Greater Richmond Metropolitan Area Status Epilepticus Study, acute fatal cardiac decompensation was most typically associated with ventricular tachyarrhythmias.41 Most of these patients did not have increased premature ventricular contractions prior to death, indicating a latent cardiac arrhythmogenicity, possibly induced by prolonged effects of seizures on their hearts. Similar potential myocardial damage may be induced by longstanding refractory epilepsy, which has been suggested as a risk factor for SUDEP, sudden unexplained (or unexpected) death in epilepsy.42
Sudden unexplained death in epilepsy (SUDEP)
There are differences of opinion about the specific definition of SUDEP, but it is generally agreed that “definite” cases require autopsy confirmation to ensure that no anatomic or toxicologic cause of death can be identified. The exact incidence is unclear because of the low rate of autopsies, but is estimated to be 0.35 to 1.0 per 1000 patient years.42,43 This incidence is estimated to be at least 24 times higher than the rate of sudden death in the general population without epilepsy. Higher incidences are found in patients with refractory seizures, and appear independent of type of treatment.
Proposed mechanisms of SUDEP include:
- cardiac arrhythmia44
- microscopic myocardial damage from seizure-induced catecholamine effects
- neurogenic pulmonary edema
- central apnea.45
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).