Sleep Depth May Be Correlated with Heart Rate After Seizures During Sleep

Sleep cycles are accompanied by dynamic changes in cardiac activity in normal individuals. In patients with epilepsy, seizures occurring during sleep may be followed by cardiac dysregulation, including arrhythmias and bradycardia. This cardiac dysregulation may be relevant to sudden unexpected death in epilepsy because most of these deaths occur during sleep.

Schomer and colleagues reasoned that a better understanding of cardiac changes after seizures that occur in sleep may help predict which patients with epilepsy are vulnerable to sudden unexpected death. In this study, they analyzed how seizure activity occurring at different depths of the sleep cycle affected heart rate after the seizure.

The investigators monitored patients with epilepsy during sleep at the University of Virginia Epilepsy Monitoring Unit. Participants were monitored with electroencephalographic scalp recordings for sleep and seizure activity and cardiac telemetry for cardiac monitoring. They correlated sleep depth in the 5 minutes preceding a seizure with the slowest heart rate in the 10 minutes following the seizure.

Participants in the study had received a diagnosis of epilepsy an average of 20.5 years before enrollment and had an average age of 40.5 years. There were 42 patients who had 101 seizures during monitoring, with 35 of these seizures occurring during sleep.

The investigators found that a greater sleep depth was associated with a lower heart rate after the seizure (P <.05). Age, baseline heart rate, and seizures that were not generalized tonic-clonic seizures also correlated with lower heart rate after seizures. When they adjusted their data for these covariates, the correlation between sleep depth and heart rate after a seizure was even more significant (P <.001).

The investigators concluded that sleep state during a seizure affects cardiac regulation, and a seizure during deep sleep when the heart rate is already low can further reduce the heart rate.

These results may have implications for predicting which patients are at risk for sudden unexpected death in epilepsy. The investigators speculated that “bradycardia may be a surrogate marker for those at increased risk of more severe cardiac deterioration after seizures.”

Source

Schomer AC, Lynch M, Lowenhaupt S, et al. Synergistic effect of sleep depth and seizures correlates with postictal heart rate. Epilepsia. 2021;62:e65-e69.