Most seizures increase heart rate, but epilepsy can also produce bradycardia, asystole and other rhythm changes. These uncommon cardiac manifestations are important because they can cause sudden collapse, mimic syncope and occasionally require treatment beyond antiseizure medication alone.
The heart changes during many seizures
Autonomic activation commonly produces tachycardia during focal and bilateral tonic-clonic seizures.
Less commonly, seizure activity can slow the heart dramatically or produce transient asystole.
Ictal bradycardia and asystole are uncommon but real
Classic literature found that many documented cases arose from temporal or frontotemporal seizures.
A 2025 state-of-the-art review confirms that ictal bradycardia and asystole remain recognised seizure-associated arrhythmias.
Why a seizure can alter heart rhythm
The insula, amygdala, cingulate cortex and other components of the central autonomic network influence sympathetic and parasympathetic cardiac control.
Seizure activity spreading through these networks can therefore change heart rate and conduction.
Why diagnosis is difficult
A person who suddenly becomes pale and collapses may have primary cardiac syncope, an epileptic seizure with secondary arrhythmia, or both conditions.
Simultaneous EEG and ECG during an event is especially valuable because either test alone can miss the sequence.
Pacemakers do not treat the epilepsy
In selected people with recurrent ictal asystole and injury-producing collapse, cardiac pacing may reduce the consequences of the bradyarrhythmia.
Seizure control remains essential because a pacemaker does not stop the underlying epileptic event.
This is not the whole explanation for SUDEP
Ictal asystole is dramatic, but current evidence does not support it as the main mechanism of most SUDEP.
Generalised tonic-clonic seizures can produce complex central respiratory and autonomic dysfunction that is biologically different from the classic ictal-bradycardia syndrome.
Concurrent monitoring is increasingly important
Recent reviews highlight the value of combining ECG with EEG in epilepsy monitoring, ambulatory assessment and selected wearable technologies.
This is particularly relevant when a history contains both seizure-like events and unexplained syncope.
Related reading
Sources and further reading
- Epilepsy and cardiac arrhythmias: state-of-the-art review — 2025
- The brain-heart connection: concurrent ECG and EEG — 2024
- Ictal bradycardia in partial seizures — review
Evidence checked: September 2026.