ECG in Seizures: Indications and Clinical Utility
Yes, an ECG is strongly indicated in patients presenting with seizures and should be performed routinely as part of the initial diagnostic evaluation. Multiple high-quality guidelines and research studies support obtaining an ECG to identify cardiac causes that may mimic seizures and to detect potentially life-threatening cardiac abnormalities that increase mortality risk.
Primary Indications for ECG in Seizure Patients
Initial Diagnostic Evaluation
An ECG should be obtained in all patients presenting with seizures or suspected epilepsy to rule out cardiac syncope masquerading as seizure activity, particularly long QT syndrome and other arrhythmogenic conditions that can cause convulsive syncope 1.
Cardiac syncope from arrhythmias frequently presents with seizure-like activity including convulsions, loss of consciousness, and loss of postural tone, leading to high rates of misdiagnosis when ECG is not performed 2.
Long QT syndrome (LQTS) is a critical differential diagnosis that can lead to torsade de pointes, ventricular fibrillation, and cardiac arrest if mistaken for epilepsy and left untreated 3.
Prognostic Value
QT prolongation detected on ECG predicts all-cause mortality in seizure patients with a Cox hazard ratio of 1.90 (95% CI 1.76-2.05), maintained even after adjusting for age, comorbidities, and sex (HR 1.48; 95% CI 1.37-1.59) 4.
Patients with epilepsy should undergo ECG screening to rule out diseases that mimic epilepsy and to identify neurological channelopathies that affect both cardiac and brain ion channels 1.
Specific Clinical Scenarios Requiring ECG
Post-Cardiac Arrest Seizures
EEG, not ECG, is the primary monitoring tool for seizure diagnosis after cardiac arrest, with Class I recommendation to promptly perform and interpret EEG in patients who do not follow commands after return of spontaneous circulation (ROSC) 1.
However, continuous cardiac monitoring remains essential in this population given the 10-35% incidence of seizures and the need to distinguish seizure activity from ongoing cardiac dysfunction 1.
Refractory Seizures
Patients with refractory focal seizures have significant risk of cardiac arrhythmias including potentially fatal asystole (16% in one study), with clinical characteristics similar to those at greatest risk of sudden unexpected death in epilepsy (SUDEP) 5.
Ictal bradycardia (<40 bpm) occurs in 2.1% of recorded seizures, and 21% of patients with refractory epilepsy may develop bradycardia or asystole requiring permanent pacemaker insertion 5.
Generalized Seizures
Generalized seizures carry higher risk of ECG abnormalities compared to non-generalized seizures (35% vs lower rates), including potentially serious changes like ST-depression and T-wave inversion in 13% of generalized seizures 6.
Nearly all seizures (99%) cause increased heart rate, and 21.5% overall demonstrate ECG abnormalities beyond sinus tachycardia, with 6% showing potentially serious changes 6.
Common Pitfalls and How to Avoid Them
Diagnostic Delays
Patients with LQTS initially misdiagnosed with epilepsy experience particularly long diagnostic delays, sometimes taking years before correct diagnosis, with some not diagnosed until requiring resuscitation from cardiac arrest 3.
ECG should be repeated if seizures persist despite antiepileptic treatment, as this may indicate an incorrect diagnosis of epilepsy when the true cause is cardiac 3.
Inadequate ECG Utilization
Current ECG utilization in seizure evaluation is poor, with only 57.4% of patients receiving an ECG during index evaluation for seizure or epilepsy in one large cohort study 4.
The one-lead ECG during video-EEG monitoring is insufficient; a full 12-lead ECG provides superior diagnostic information and should be obtained as a separate test 2.
Distinguishing Syncope from Seizure
Brief seizure activity can occur during syncope (including vasovagal syncope), and when the history clearly indicates syncope, this seizure-like activity does not require neurologic investigation or EEG 1.
Tilt-table testing with simultaneous EEG and hemodynamic monitoring is reasonable (Class IIa) to distinguish among syncope, pseudosyncope, and epilepsy when the diagnosis remains unclear 1.
Practical Algorithm for ECG Use
At initial presentation with seizure:
- Obtain 12-lead ECG in all patients 4
- Measure QTc interval and assess for conduction abnormalities 3
- Screen for features suggesting cardiac syncope: syncope during exertion, supine position, palpitations, family history of sudden cardiac death 1
If seizures persist despite treatment:
In post-cardiac arrest patients:
If cardiac abnormalities detected: